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+Draft version January 10, 2023
+Typeset using LATEX twocolumn style in AASTeX631
+3D modeling of the molecular gas kinematics in optically-selected jellyfish galaxies
+Cecilia Bacchini
+,1 Matilde Mingozzi
+,2 Bianca M. Poggianti
+,1 Alessia Moretti
+,1
+Marco Gullieuszik
+,1 Antonino Marasco
+,1 Bernardo Cervantes Sodi
+,3 Osbaldo S´anchez-Garc´ıa
+,3
+Benedetta Vulcani
+,1 Ariel Werle
+,1 Rosita Paladino
+,4 and Mario Radovich
+1
+1INAF - Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, IT-35122 Padova, Italy
+2Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
+3Istituto de Radioastronom´ıa y Astrof´ısica, Universidad Nacional Aut´onoma de M´exico, Campus Morelia, A.P. 3-72, C.P. 58089,
+Michoac´an, M´exico
+4INAF - Istituto di Radioastronomia, via P. Gobetti 101, I-40129 Bologna, Italy
+ABSTRACT
+Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can
+perturb or even strip away their gas while leaving the stars unperturbed. We model the distribution
+and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204,
+JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure
+stripping. We analyze MUSE@VLT data and CO data from ALMA searching for signatures of radial
+gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible
+exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206,
+which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping
+affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead
+dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of
+the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in
+JO204 and JW100, but more uncertain in JO201 and JO206. We show that our galaxy sample follows
+the molecular gas mass-size relation, confirming that it is essentially independent of environment even
+for the most extreme cases of stripping. Our findings are consistent with the molecular gas being
+affected by ram pressure on different timescales and less severely than the atomic and ionized gas
+phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.
+1. INTRODUCTION
+In dense environments, such as groups and clusters,
+galaxies are affected by various physical mechanisms
+that can significantly influence their properties and evo-
+lution (Nulsen 1982; Boselli & Gavazzi 2006; Cortese
+et al. 2021). These processes are usually divided into
+gravitational and hydrodynamical interactions (Boselli
+et al. 2022a).
+Gravitational perturbations can be in-
+duced by tidal forces due to the potential of other clus-
+ter/group members (Merritt 1983) or the large scale
+structure itself (Byrd & Valtonen 1990), but also by fly-
+by encounters and mergers (Barnes & Hernquist 1992;
+Kronberger et al. 2006). Gravitational interactions af-
+fect both the stellar and the gaseous components of
+galaxies. Instead, the hydrodynamical interactions be-
+Corresponding author: Cecilia Bacchini
+cecilia.bacchini@inaf.it
+tween the galactic interstellar medium (ISM) and the in-
+tracluster medium (ICM) are expected to influence only
+the gaseous components of galaxies. These mechanisms
+are the thermal evaporation of the cold (T ≲ 104 K) ISM
+due to the interaction of the hot (T ≈ 107 −108 K) ICM
+(Cowie & Songaila 1977), the removal of the outer ISM
+layer due to the viscosity momentum transfer with the
+ICM (viscous stripping) or instabilities (Nulsen 1982;
+Roediger & Hensler 2008), and the ram pressure strip-
+ping, that is the removal of the ISM due to the pressure
+exerted by the ICM while a galaxy is moving through
+the cluster (Gunn & Gott 1972). In addition, the in-
+teraction with the ICM can heat up or strip away the
+hot (T ≈ 106 K) gas corona surrounding galaxies and
+prevent them from accreting new gas, finally quenching
+star formation (starvation; Larson et al. 1980).
+Ram pressure is often considered among the domi-
+nant mechanisms affecting the ISM in cluster galaxies.
+The ram pressure can be calculated as Pram = ρICMV 2
+gal,
+arXiv:2301.03090v1  [astro-ph.GA]  8 Jan 2023
+
+ID2
+Bacchini et al.
+where ρICM and Vgal are the ICM density and the galaxy
+velocity relative to the cluster (Gunn & Gott 1972).
+Hence, this mechanism is expected to be particularly
+strong for galaxies with high Vgal located close to the
+cluster center, where ρICM is the highest. The ram pres-
+sure can have different effects on the gas distribution
+and kinematics in galaxies. The compression of the gas
+disk can make it morphologically lopsided and asymmet-
+ric (e.g. Mapelli et al. 2008; Kronberger et al. 2008b).
+Depending on its direction with respect to the galaxy
+rotation, the ram pressure can decelerate one side of the
+gas disk and accelerate the other, resulting in a kinemat-
+ically lopsided disk, or even shift the kinematic center
+of the gas disk with respect to the optical center of the
+galaxy (e.g. Kronberger et al. 2008b).
+Typical signa-
+tures of ram pressure stripping are one-sided tails of gas
+extending outside the stellar disk and gas clouds that are
+spatially detached and kinematically decoupled from the
+galaxy (e.g. Chung et al. 2007; Merluzzi et al. 2013; Lee
+et al. 2017). Moreover, gas disks in cluster galaxies are
+sometimes less extended and less massive that those in
+field galaxies (Chamaraux et al. 1980; Haynes et al. 1984;
+Cayatte et al. 1990; Schr¨oder et al. 2001; Chung et al.
+2009). Both truncation and gas deficiency are proper-
+ties ascribed to ram pressure stripping, being relatively
+common in both low- (e.g. Chung et al. 2007; Gavazzi
+et al. 2018) and intermediate-redshift cluster galaxies
+(e.g. Cortese et al. 2007; Boselli et al. 2019; Moretti et al.
+2022). The efficiency of ram pressure stripping depends
+on the gas properties, being more effective on a diffuse
+medium than on dense gas clumps, and on the gravita-
+tional pull caused by the galactic potential, that weak-
+ens with increasing galactocentric distance and height
+above the midplane (e.g. Gunn & Gott 1972; Tonnesen
+& Bryan 2009; K¨oppen et al. 2018).
+The atomic gas in galaxies is relatively diffuse and
+typically distributed in a disk that is very extended (up
+to twice the stellar disk diameter; see e.g. Verheijen
+& Sancisi 2001; Wang et al. 2016; Lelli et al. 2016a)
+and thick (up to ≈1 kpc; see e.g. Olling 1996; Yim
+et al. 2011, 2014; Marasco et al. 2017; Bacchini et al.
+2019a,b, 2020b), being very susceptible to ram pressure.
+Indeed, cluster galaxies often contain less atomic gas
+than expected from their optical size or stellar mass and
+have truncated and/or asymmetric HI discs (Chama-
+raux et al. 1980; Haynes et al. 1984; Giovanelli & Haynes
+1985; Cayatte et al. 1990; Solanes et al. 2001; Schr¨oder
+et al. 2001; Waugh et al. 2002; Chung et al. 2009; Loni
+et al. 2021; Zabel et al. 2022). Morever, long tails of
+atomic gas are commonly observed in cluster galaxies
+(Bravo-Alfaro et al. 2000; Kenney et al. 2004; Chung
+et al. 2007; Scott et al. 2010; Sorgho et al. 2017; Ramat-
+soku et al. 2019, 2020; Deb et al. 2020; Healy et al. 2021;
+Deb et al. 2022).
+The molecular gas is typically denser than the atomic
+gas (e.g. Leroy et al. 2008) and its distribution is also
+less extended in both the radial (up to the stellar disk
+diameter; Davis et al. 2013; Brown et al. 2021; Zabel
+et al. 2022) and vertical (up to ≈ 0.3 kpc; Yim et al.
+2011, 2014; Marasco et al. 2017; Bacchini et al. 2019a,b)
+directions. Hence, it is expected that the molecular gas
+is more resilient to ram pressure than the atomic gas
+(e.g. Lee et al. 2017; Brown et al. 2021; Zabel et al.
+2022; Boselli et al. 2022a). Nevertheless, there is grow-
+ing observational evidence that the ram pressure actu-
+ally influences the molecular gas in cluster galaxies, as
+indicated by signatures of compression, kinematic lop-
+sidedness, and shifts between the optical and kinematic
+center (Lee et al. 2017; Zabel et al. 2019; Cramer et al.
+2020). Direct observations of molecular gas stripping by
+ram pressure are limited, but tails and blobs of molec-
+ular gas far from the stellar disk have been observed in
+some cluster galaxies (Vollmer et al. 2008; J´achym et al.
+2014, 2017; Lee et al. 2017; Moretti et al. 2018, 2020a),
+as well as truncated molecular gas disks and H2-deficient
+galaxies (Fumagalli et al. 2009; Boselli et al. 2014; Zabel
+et al. 2019, 2022; Lee et al. 2022). However, a few au-
+thors have found that cluster galaxies can also host a
+normal (both in size and mass) or even enhanced reser-
+voir of molecular gas (Fumagalli et al. 2009; Moretti
+et al. 2020b; Brown et al. 2021; Zabel et al. 2022), pos-
+sible indication that ram pressure can increase the effi-
+ciency of the HI-to-H2 conversion (Moretti et al. 2020a).
+In this work, we analyze the molecular gas distribution
+and kinematics in four cluster galaxies observed with
+the Atacama Large Millimeter Array (ALMA). These
+objects are part of the sample of 114 galaxies observed
+within the Large Program ”GAs Stripping Phenomena
+in galaxies with MUSE” (GASP), which is a survey
+carried out with integral-field Multi Unit Spectroscopic
+Explorer (MUSE) at the Very Large Telescope (VLT).
+The GASP survey aims at understanding the impact of
+environment on the evolution of galaxies by studying
+their stellar and ionized gas emission. Recently, follow-
+up programs have provided multi-wavelength observa-
+tions for a few galaxies in the GASP sample, allowing
+to study other ISM components, such as atomic gas (Ra-
+matsoku et al. 2019, 2020; Deb et al. 2020; Healy et al.
+2021; Deb et al. 2022; Luber et al. 2022), the molec-
+ular gas (Moretti et al. 2018, 2020a,b), and magnetic
+fields (M¨uller et al. 2021), and also young stellar pop-
+ulations (George et al. 2018). An unexpected result of
+the GASP project was the high fraction of active galac-
+tic nuclei (AGN) among ram pressure-stripped galaxies
+
+Molecular gas kinematics in jellyfish galaxies
+3
+(Poggianti et al. 2017a; Peluso et al. 2022; Poggianti &
+the GASP team 2022). This result was interpreted as an
+indication that ram pressure can drive gas flows towards
+the center and feed the AGN activity (e.g. Ricarte et al.
+2020).
+The galaxies analyzed in this work (hereafter
+referred as the GASP-ALMA sample) were studied by
+Poggianti et al. (2017a) and host indeed an AGN. This
+paper aims at answering the following open questions
+about the GASP-ALMA galaxies: What is the impact
+of ram pressure on the distribution and kinematics of
+the molecular gas? Can we detect inflows of molecular
+gas that may feed the AGN?
+This paper is organized as follows. Section 2 presents
+the GASP-ALMA sample and summarizes the relevant
+pieces of information obtained by previous studies. We
+describe the data and methods used to carry out the
+analysis in Sects. 3 and 4, respectively. For each galaxy,
+we present and discuss the results in Sect. 5. In Sect. 6,
+we compare our findings with other works in the litera-
+ture. Section 7 this work and its conclusions.
+We adopt standard cosmological parameters (h = 0.7,
+ΩM = 0.3, and Ωλ = 0.7) and a Chabrier (2003) initial
+mass function.
+2. THE GALAXY SAMPLE
+The GASP-ALMA sample consists of four late-type
+galaxies, i.e.
+JO201, JO204, JO206, and JW100, lo-
+cated in different clusters at redshift 0.04 ≲ z ≲ 0.06 and
+with relatively high stellar mass (see Table 1 and refer-
+ences therein). These galaxies are classified as “jellyfish”
+because they show one-sided tails of ionized gas longer
+than the stellar disk diameter (Poggianti et al. 2016).
+Thanks to the wealth of information provided by the
+GASP project and the availability of multi-wavelength
+observations, these galaxies have been extensively stud-
+ied in the literature (for a brief review, see Poggianti &
+the GASP team 2022). Thus, we summarize some of the
+previous works that are relevant for our analysis.
+The galaxies in our sample are moving through the
+ICM with either super-sonic or transonic line-of-sight ve-
+locities and are located close to the cluster center (Gul-
+lieuszik et al. 2020). These properties indicate that the
+galaxies are in favorable conditions for strong ram pres-
+sure and move on very radial orbits, suggesting that
+they have recently entered into the cluster for the first
+time (Yoon et al. 2017; Jaff´e et al. 2018). While JO204
+and JO206 are relatively isolated for being cluster mem-
+bers (Gullieuszik et al. 2017; Biviano et al. 2017), JO201
+and JW100 belong to a substructure of four and three
+galaxies, respectively (Bellhouse et al. 2017; Poggianti
+et al. 2019). Previous works show that, in all the GASP-
+ALMA galaxies, the stellar kinematics appears to be
+quite regular, while the ionized gas kinematics is very
+perturbed, as expected for galaxies undergoing ram pres-
+sure stripping (Bellhouse et al. 2017; Gullieuszik et al.
+2017; Poggianti et al. 2017b; Jaff´e et al. 2018; Poggianti
+et al. 2019).
+Recent works showed that these galax-
+ies host strongly asymmetric HI disks with long tails
+of atomic gas, and also have significantly reduced the
+HI content with respect to field galaxies (≳ 50 %, Ra-
+matsoku et al. 2019, 2020; Deb et al. 2020; Healy et al.
+2021; Deb et al. 2022). This HI deficiency is however
+not coupled with a deficiency in the molecular gas reser-
+voir, as these galaxies have H2 masses that are 4-5 times
+higher than expected for galaxies with similar stellar
+mass (Moretti et al. 2020a,b).
+As mentioned above, the galaxies in the GASP-ALMA
+sample host an AGN (Poggianti et al. 2017a; Radovich
+et al. 2019; Peluso et al. 2022). It has been shown that
+the AGN is the main source of gas ionization in the cen-
+tral regions of these galaxies and, except for JO206, it
+also causes a low-velocity (≈ 250 − 320 km s−1) wind
+of ionized gas (Radovich et al. 2019). Poggianti et al.
+(2017a) proposed that the AGN activity in these galax-
+ies is triggered by the ram pressure, which can decrease
+the angular momentum of the gas and favor its inflow
+toward the center. In JO201, George et al. (2019) ob-
+served a cavity of about 8.6 kpc with reduced ultravi-
+olet and CO flux around the AGN (see also Radovich
+et al. 2019). By combining optical (MUSE) and sub-
+mm (ALMA) spectroscopic observations, these authors
+proposed that the cavity is due to AGN feedback that is
+either ionizing or sweeping away the gas, possibly reduc-
+ing the star formation activity in the central regions. In
+JO204, Deb et al. (2020) found a redshifted absorption
+feature in the HI global profile, which could be ascribed
+to either a clumpy and fast rotating HI disc seen in front
+of the central radio continuum source or an inflow of
+atomic gas towards the central AGN.
+3. DATA
+This section describes the multi-wavelength observa-
+tions and data products that were used in this work,
+which primarily focuses on the molecular gas. Since the
+ram pressure can influence the kinematics and geometry
+of the molecular gas disk, we analyze the stellar kine-
+matics and use it as a reference. Sections 3.1 and 3.2
+describe the data used to study the molecular gas and
+stellar component, respectively.
+3.1. ALMA data
+We used CO(1–0) and CO(2–1) emission line obser-
+vations obtained with ALMA during Cycle 5 (project
+
+4
+Bacchini et al.
+Table 1. Properties of the galaxy sample.
+Property
+Galaxy
+JO201
+JO204
+JO206
+JW100
+Alternative names
+KAZ 364
+2MASX J10134686-0054514
+2MASX J21134738+0228347
+IC 5337
+Morphological type
+Sab
+Sab
+Sb
+Sa
+Cluster
+Abell 85
+Abell 957
+IIZW108
+Abell 2626
+zclu
+0.05568
+0.04496
+0.04889
+0.05509
+zgal
+0.044631
+0.042372
+0.051089
+0.061891
+Vgal [km s−1]
+-3138
+-743
+629
+1932
+|Vgal/σclu|
+3.7
+1.2
+0.9
+3.0
+Rclu/R200,cl
+0.18
+0.09
+0.29
+0.06
+Distance [Mpc]
+189.1
+179.8
+216.3
+261.4
+Physical scale [kpc/arcsec]
+0.88
+0.84
+1.00
+1.19
+Center R.A. [J2000]
+00:41:30.30
+10:13:46.84
+21:13:47.41
+23:36:25.05
+Center DEC [J2000]
+-09:15:45.9
+-00:54:51.27
++02:28:35.50
++21:09:02.64
+M⋆ [1010 M⊙]
+6.2 ± 0.8
+4.1 ± 0.6
+9.1 ± 0.9
+29 ± 7
+MHI [109 M⊙]
+1.7 ± 0.5
+≳ 1.3 ± 0.1
+3.2 ± 0.9
+2.8 ± 0.8
+MH2 [109 M⊙]
+11.5 ± 5.8
+5.7 ± 2.9
+5.6 ± 2.8
+16.5 ± 8.3
+Note—Galaxy names are in GASP convention; alternative names are also provided. Morphological types are from Fasano et al.
+(2012).
+Cluster redshifts (zclu) are from Biviano et al. (2017).
+Galaxy redshifts (zgal) and distances from the cluster center
+(Rclu/R200,cl) are from Bellhouse et al. (2017); Gullieuszik et al. (2017); Poggianti et al. (2017b, 2019). Galaxy velocities relative
+to cluster are calculated as Vgal = c(zgal − zclu)/(1 + zclu). The optical center coordinates are from Poggianti et al. (2017a).
+Stellar masses (M⋆) and effective radii (Reff) are from Vulcani et al. (2018) and Franchetto et al. (2020), respectively. Atomic gas
+masses (MHI) are from Ramatsoku et al. (2019, 2020) and Deb et al. (2020, 2022); a conservative uncertainty of 30% is assumed.
+Molecular gas masses (MH2) are from Moretti et al. (2020a); a conservative uncertainty of 50% is assumed.
+2017.1.00496.S; PI: Poggianti). These observations were
+already used by Moretti et al. (2020b) to study the
+molecular gas content of the GASP-ALMA galaxies.
+The datacubes used in this work are different from those
+used by Moretti et al. (2020b), as the imaging proce-
+dure was re-performed to increase the spectral resolu-
+tion (Mingozzi et al. to be submitted). Here, we use
+ALMA datacubes with spatial resolution of ≈ 1−2′′(see
+Fig. 1) and velocity resolution of 10 km s−1. Figure 1
+shows, for each galaxy, the moment maps of the CO(1–
+0) datacubes.
+These maps were obtained from the
+ALMA datacubes by applying a mask made by all pixels
+with signal-to-noise ratio (S/N) above 3 in a datacube
+smoothed by a factor 2 (i.e. in which each channel map
+is convolved with a beam 2 times larger than the original
+one).
+We note that Moretti et al. (2020a,b) detected faint
+CO emission coming from the regions outside the stel-
+lar disk and coinciding with the ionized gas tails. The
+emission is not visible in the maps used in this work
+(Fig. 1), despite we used the same ALMA observations.
+This difference is due to the fact that our datacubes
+have better velocity resolution (∆υ = 10 km s−1) but
+lower S/N than those used by Moretti et al. (2020a,b),
+which have ∆υ = 20 km s−1and to the different masking
+procedure adopted in the two works. For this work, we
+used the datacubes with ∆υ = 10 km s−1, being the best
+compromise to have good velocity resolution and S/N in
+the regions within (or close to) the stellar disk. We note
+that we do not find significant differences in mass and
+size of the molecular gas disk with respect to the results
+obtained by Moretti et al. (2020a,b).
+3.2. MUSE data
+To analyze the stellar component, we used the MUSE
+observations obtained by the GASP survey (Poggianti
+et al. 2017b). The data reduction and processing is de-
+tailed in Poggianti et al. (2017b). The wavelength cov-
+erage and spectral resolution of the final datacubes are
+4800 ˚A < λ < 9300˚A and 1770 < R < 3590, respec-
+tively. The pixel size is 0.2 ′′×0.2 ′′with a natural seeing
+of ≈ 1 ′′. In this work, we use the I-band images and
+the stellar velocity fields extracted from the MUSE dat-
+acubes.
+The I-band images are very useful to identify stellar
+substructures, such as bulges and bars. These are typ-
+
+Molecular gas kinematics in jellyfish galaxies
+5
+0h41m31.0s30.5s
+30.0s
+29.5s
+-9°15'35"
+40"
+45"
+50"
+55"
+16'00"
+RA (ICRS)
+Dec (ICRS)
+JO201
+CO(1-0) total intensity map
+5 kpc
+0.001
+0.002
+0.003
+0.004
+0.005
+0.006
+0.007
+FCO(1
+0) [Jy beam
+1 km/s]
+0h41m31.0s30.5s
+30.0s
+29.5s
+-9°15'35"
+40"
+45"
+50"
+55"
+16'00"
+RA (ICRS)
+JO201
+2.04"x1.6"
+CO(1-0) velocity field
+250
+200
+150
+100
+50
+0
+50
+100
+150
+VLOS [km/s]
+0h41m31.0s30.5s
+30.0s
+29.5s
+-9°15'35"
+40"
+45"
+50"
+55"
+16'00"
+RA (ICRS)
+JO201
+CO(1-0) velocity dispersion map
+10
+15
+20
+25
+30
+35
+40
+45
+50
+CO [km/s]
+10h13m47.5s 47.0s
+46.5s
+46.0s
+-0°54'40"
+45"
+50"
+55"
+55'00"
+RA (ICRS)
+Dec (ICRS)
+JO204
+CO(1-0) total intensity map
+5 kpc
+0.002
+0.004
+0.006
+0.008
+0.010
+FCO(1
+0) [Jy beam
+1 km/s]
+10h13m47.5s 47.0s
+46.5s
+46.0s
+-0°54'40"
+45"
+50"
+55"
+55'00"
+RA (ICRS)
+JO204
+1.66"x1.39"
+CO(1-0) velocity field
+200
+100
+0
+100
+200
+VLOS [km/s]
+10h13m47.5s 47.0s
+46.5s
+46.0s
+-0°54'40"
+45"
+50"
+55"
+55'00"
+RA (ICRS)
+JO204
+CO(1-0) velocity dispersion map
+10
+20
+30
+40
+50
+60
+CO [km/s]
+21h13m48.0s47.3s
+46.7s
+46.0s
+2°28'50"
+40"
+30"
+20"
+RA (ICRS)
+Dec (ICRS)
+JO206
+CO(1-0) total intensity map
+5 kpc
+0.002
+0.003
+0.004
+0.005
+0.006
+0.007
+FCO(1
+0) [Jy beam
+1 km/s]
+21h13m48.0s47.3s
+46.7s
+46.0s
+2°28'50"
+40"
+30"
+20"
+RA (ICRS)
+JO206
+1.87"x1.73"
+CO(1-0) velocity field
+100
+0
+100
+200
+300
+VLOS [km/s]
+21h13m48.0s47.3s
+46.7s
+46.0s
+2°28'50"
+40"
+30"
+20"
+RA (ICRS)
+JO206
+CO(1-0) velocity dispersion map
+10
+15
+20
+25
+30
+35
+40
+45
+50
+CO [km/s]
+23h36m25.3s
+24.7s
+24.0s
+21°09'15"
+10"
+05"
+00"
+08'55"
+50"
+RA (ICRS)
+Dec (ICRS)
+JW100
+CO(1-0) total intensity map
+5 kpc
+0.0050
+0.0075
+0.0100
+0.0125
+0.0150
+0.0175
+0.0200
+FCO(1
+0) [Jy beam
+1 km/s]
+23h36m25.3s
+24.7s
+24.0s
+21°09'15"
+10"
+05"
+00"
+08'55"
+50"
+RA (ICRS)
+JW100
+2.09"x1.78"
+CO(1-0) velocity field
+200
+100
+0
+100
+200
+300
+400
+500
+VLOS [km/s]
+23h36m25.3s
+24.7s
+24.0s
+21°09'15"
+10"
+05"
+00"
+08'55"
+50"
+RA (ICRS)
+JW100
+CO(1-0) velocity dispersion map
+10
+20
+30
+40
+50
+60
+70
+80
+CO [km/s]
+Figure 1. Total intensity map (left column), velocity field (central column) and velocity dispersion map (right column) obtained
+from the CO(1-0) emission line datacubes for the four galaxies in the sample. The stars and the white dashed ellipse indicate the
+kinematic center and the region used for modelling the gas kinematics, respectively. In JW100, the grey cross shows the optical
+center. In the total intensity map, the red contours are at 2nσtot, where σtot is the noise in the total map (Lelli et al. 2014;
+Iorio et al. 2017), n = 1...10, and σtot = 0.9, 1.4, 1.4, 2.7 mJy/beam km s−1for JO201, JO204, JO206, and JW100, respectively.
+In the velocity field, the black curves are the iso-velocity contours, with the thick one being at the galaxy systemic velocity (see
+Sect. 4.2 for details). The white dotted line in the velocity field is the kinematic major axis. The bar and the ellipse in the
+bottom left corner respectively show the physical scale and beam of the observations. The grey contours show the stellar disc.
+East is to the left and North to the top.
+
+6
+Bacchini et al.
+ically dominated by intermediate-age (> 1 Gyr) stellar
+populations and hence generally brighter in I-band than
+at short wavelengths (e.g. Knapen et al. 2000).
+Fig-
+ure 2 shows, for each galaxy, the I-band images. These
+were obtained by Franchetto et al. (2020) from the inte-
+grated MUSE datacubes using the Cousins I-band filter
+response curve.
+Franchetto et al. (2020) also derived
+the center coordinates, the position angle, and the incli-
+nation of these galaxies by fitting the galaxy isophotes
+with a series of concentric ellipses using the iraf task
+ELLIPSE (Jedrzejewski 1987).
+The stellar velocity fields are used to analyze the stel-
+lar kinematics, which is useful to interpret the kinemat-
+ics of the molecular gas.
+The stellar kinematics was
+extracted from the MUSE datacube using the Penal-
+ized Pixel-Fitting (pPXF) code (Cappellari & Emsellem
+2004).
+As a preliminary step, the observations were
+masked to remove spurious sources, such as stars and
+background galaxies. Spaxels in the MUSE data were
+binned through the Voronoi algorithm in order to reach
+S/N> 10 in each bin. The observed spectra were fitted
+with the stellar population templates by Vazdekis et al.
+(2010) and using of single stellar populations. More de-
+tails on the procedure can be found in Poggianti et al.
+(2017b) and Moretti et al. (2018).
+4. METHOD
+Our approach relies on the software 3DBarolo1 (v.6.1
+Di Teodoro & Fraternali 2015; Di Teodoro & Peek 2021),
+which simulates galaxy observations assuming a tilted-
+ring model. This consists of a series of concentric annuli
+described by a set of geometric and kinematic parame-
+ters, which can all vary with the galactocentric distance
+R. The geometrical parameters are the coordinates of
+the center x0 and y0, the position angle φ, and the disc
+inclination i. The kinematic parameters are the systemic
+velocity Vsys, the rotation velocity Vrot, the velocity dis-
+persion σ, and the radial velocity in the disc plane Vrad.
+The observed line-of-sight velocity is then (e.g. Begeman
+1987)
+Vlos = Vsys + (Vrot cos θ + Vrad sin θ) sin i ;
+(1)
+where θ is the azimuthal angle in the plane of the disc.
+3DBarolo (hereafter 3DB) was mainly designed to
+fit emission line observations working in 3D, meaning
+that the model is fitted to the datacube channel-by-
+channel. This approach allows us to use all the infor-
+mation in the datacube and to take into account both
+the spatial resolution and the spectral resolution of the
+1 https://editeodoro.github.io/Bbarolo/
+instrument. In a step prior to the fitting, 3DB convolves
+the model with the point spread function (PSF) or the
+beam of the instrument, while the instrumental spec-
+tral broadening is included in the model construction.
+The convolution with the PSF is required to correct for
+the so-called “beam smearing” (Bosma 1981; Begeman
+1987; Di Teodoro & Fraternali 2015). The finite size of
+the PSF smears the line emission on adjacent regions
+where the emitting material has different line-of-sight
+velocity, causing an artificial broadening of the profile.
+As a consequence, the rotation velocity and the velocity
+dispersion can be respectively underestimated and over-
+estimated, if beam smearing is not correctly accounted
+for. This effect is particularly important if the angu-
+lar resolution of the observations is low and where there
+are strong velocity gradients, as in the case of the inner
+regions of massive galaxies with steeply rising rotation
+curve. Moreover, the beam smearing effect is expected
+to become more and more relevant as the inclination an-
+gle of the galaxy increases. 3DB normalizes the model
+using either the flux in each pixel of the total intensity
+map or the azimuthally-averaged flux in each ring. Fi-
+nally, the model is fitted to the observations in order
+to find the set of free parameters that minimizes the
+residuals.
+With respect to 2D methods, which fit the velocity
+field, this 3D procedure not only corrects for the beam
+smearing effect, but also breaks the degeneracy between
+the rotation velocity and the velocity dispersion (e.g.
+Bosma 1981; Begeman 1987; Di Teodoro & Fraternali
+2015). The 3DB task 3DFIT is designed to model emis-
+sion line datacubes working in 3D. The software also
+includes the task 2DFIT, which can be used to model
+the 2D velocity fields. In this work, we use 3DFIT and
+2DFIT to model the kinematics of the molecular gas disk
+and the stellar disk, respectively. For each component,
+we adopted an ad-hoc methodology, that is described in
+Sects. 4.1 and 4.2.
+Before proceeding with the methodology presentation,
+a brief disclaimer is due. We stress that 3DB, like sev-
+eral other kinematic modelling software (e.g. Begeman
+1987; Kamphuis et al. 2015), is specifically designed to
+model radially symmetric gas flows in discs. However,
+the galaxies studied in this work are subject to various
+local disturbances due to internal (bar, AGN feedback)
+and external (ram pressure) mechanisms, which are ex-
+pected to produce deviations from this idealised kine-
+matics.
+Our strategy here is to use 3DB to quantify
+the large-scale ordered motions (i.e., rotation and radial
+flows) in the molecular gas component, and to interpret
+possible deviations from such simple kinematics in terms
+of internal or external mechanisms.
+
+Molecular gas kinematics in jellyfish galaxies
+7
+0h41m32s
+31s
+30s
+-9°15'30"
+45"
+16'00"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO201 I-band
+5 kpc
+20
+40
+60
+80
+100
+F  [10
+20 erg/s/cm2/Angstrom]
+10h13m48.0s47.5s
+47.0s
+46.5s
+46.0s
+45.5s
+-0°54'30"
+40"
+50"
+55'00"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO204 I-band
+5 kpc
+20
+40
+60
+80
+100
+F  [10
+20 erg/s/cm2/Angstrom]
+21h13m48s
+47s
+46s
+2°28'45"
+30"
+15"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO206 I-band
+5 kpc
+20
+40
+60
+80
+100
+F  [10
+20 erg/s/cm2/Angstrom]
+23h36m27s
+26s
+25s
+24s
+23s
+21°09'30"
+15"
+00"
+08'45"
+RA (ICRS)
+Dec (ICRS)
+1"
+JW100 I-band
+5 kpc
+20
+40
+60
+80
+100
+F  [10
+20 erg/s/cm2/Angstrom]
+Figure 2. I-band images, extracted from the MUSE observations. The red contours are at 2n with n going from 1 to 20
+with steps of 0.5 (same units as colorbars). The white stars show the galaxy center. For JO201 and JO206, the white dotted
+ellipses indicate the regions influenced by the bar (see text). The light-blue contour shows the most external isophote (≈ 1.5σ
+above the background) encompassing the Hα emission traced by MUSE, and it indicates the stellar disk defined by Gullieuszik
+et al. (2020). The black dot in the bottom right corner shows the angular resolution of the MUSE observations. The inset
+in the JO204 panel shows a zoom-in of the central regions of the galaxy, with the white circle showing the resolution of the
+observations. East is to the left and north to the top.
+4.1. Modeling the stellar kinematics
+We model the stellar kinematics using the task 2DFIT
+on the velocity field (see Sect. 3.2). We fixed the kine-
+matic center at the optical center reported in Poggianti
+et al. (2017a) and Vrad = 0 km s−1. Since stars are not
+subject to the effect of ram pressure, we expect this to
+be a good approximation everywhere in the galaxy with
+the possible exception of the bar region (but see Sect. 5).
+We adopt the following three-step approach.
+1. We performed a preliminary run with φ, i, Vsys,
+and Vrot as free parameters. The initial values of
+φ and i were taken from Franchetto et al. (2020).
+2. We made a second run with φ, i, and Vrot as free
+parameters, fixing Vsys at the median of the best-
+fit values from the first step.
+3. We run again 3DB with Vrot as the free parameter,
+while φ and i are regularized using a polynomial
+function with degree from zero to three, in order
+to avoid numerical oscillations.
+The ring spacing is fixed to 1′′, which approximately
+corresponds to the spatial resolution of the MUSE ob-
+servations. This choice is also reasonable based on the
+size of the Voronoi bins. In all 3DB runs, we chose to
+give more weight to the regions close to the disc major
+
+8
+Bacchini et al.
+axis (i.e. wfunc=2), in order to maximize the signal from
+the rotational motion.
+We recall that the results obtained with the 2D ap-
+proach are affected by beam-smearing. The angular res-
+olution of the MUSE observations is about 1 ′′, corre-
+sponding to about 1 kpc in our galaxy sample. Hence,
+we expect that the PSF smearing has a mild effect on the
+GASP-ALMA galaxies, except JW100. In this galaxy,
+the PSF smearing is likely important due to its high
+inclination with respect to the line of sight.
+We also note that the assumption of circular orbits
+might be inappropriate for the innermost regions of
+barred galaxies, as the stars in the bar move along
+elongated orbits (e.g. Sellwood & Wilkinson 1993; Ko-
+rmendy & Kennicutt 2004). However, only galaxies for
+which the bar is inclined to both the projected ma-
+jor and minor axes show non-circular motions clearly
+(Sellwood & Wilkinson 1993). Hence, we do not expect
+visible signatures of non-circular motions in JO201 and
+JO206. In Sanchez-Garcia et al. (in preparation), the
+stellar velocity field of the galaxies in the GASP sample
+is fitted using an ad-hoc approach to include large-scale
+non-circular motions induced by bars. Preliminary re-
+sults show that, for the GASP-ALMA galaxies, the re-
+covered stellar rotation velocity obtained by Sanchez-
+Garcia et al. is overall consistent with ours, suggesting
+that the non-circular motions are small compared to ro-
+tation.
+4.2. Modeling the molecular gas kinematics
+We model the molecular gas kinematics using the task
+3DFIT on the ALMA datacubes (see Sect. 3.1). To re-
+duce the free parameters in the model, we first fixed
+the kinematic center at the optical center reported in
+Poggianti et al. (2017a).
+However, since the interac-
+tion with the ICM can displace the kinematic center of
+the gas from that of the stars (e.g. Kronberger et al.
+2008b; Boselli et al. 2022b), we adjusted the kinematic
+center of the molecular gas when necessary.
+We also
+set Vsys at the value obtained from the global profile of
+the emission line. When necessary, Vsys was refined by
+a few km s−1after inspecting the position-velocity dia-
+grams (see Sect. 5).
+1. We performed a first run with Vrad = 0 km s−1and
+leaving free the geometrical and kinematical pa-
+rameters. By setting the 3DB parameter wfunc=2,
+we chose to give more weight to the emission along
+the disc major axis, where most of the information
+on rotational motions lies (θ = 0° in Eq. 1).
+2. We made a second run (i.e. twostage=True) in
+which the geometrical parameters are regularized
+using either a suitable function or the median
+value.
+3. Vrad is left free in the last run, while the other pa-
+rameters are fixed to the best-fit values obtained
+previously.
+By setting wfunc=-2, we give more
+weight to the emission along the disc minor axis,
+where the contribution of radial motions is the
+strongest (θ = 90° in Eq. 1).
+This procedure is substantially based on the approach
+developed by Di Teodoro & Peek (2021), who used
+3DB to model the atomic gas kinematics in a sample of
+nearby galaxies in order to measure gas radial motions
+and mass flows. These authors used 21-cm observations
+with higher spatial resolution and better velocity reso-
+lution than our ALMA data. Radial motions are pos-
+sibly stronger and easier to detect for galaxies affected
+by the ram pressure than in the case of Di Teodoro &
+Peek (2021)’s galaxies, in which radial motions are of
+the order of a few km s−1. We stress that the approach
+adopted in this work takes into account the radial mo-
+tions within the galaxy disk, while motions perpendicu-
+lar to the disk midplane are not considered (Di Teodoro
+& Peek 2021).
+We used the 3DB task ELLPROF to derive the
+azimuthally-averaged radial profiles of the CO surface
+brightness. These profile were adopted for the normal-
+ization procedure of 3DB models and to derive the H2
+surface density ΣH2.
+We also used the 3DB task spacepar to fully explore
+the parameter space for Vrot and σ. This test is useful
+to check whether the model fitting converges to a good
+minimum of the parameter space. We anticipate that,
+while the best-fit Vrot is generally well constrained, it
+is not always the case for σ. This is likely due to the
+complex shape of the emission line profiles.
+A possible caveat in our methodology is that the
+tilted-ring model is based on the assumption of concen-
+tric orbits, which might not be valid for the gas in galax-
+ies affected by strong ram pressure or in an advanced
+stripping stage (e.g. Kronberger et al. 2008b). In these
+cases, the results of our analysis are very uncertain and
+should be taken with caution. However, if stripping is
+not too dramatic, modeling the gas kinematics using the
+tilted-ring approach may be possible for the disk regions
+where some or most of the gas has preserved its original
+motion. Stellar bars are also expected to induce non-
+circular motions due to the gas streaming along the bar
+(e.g. Sellwood & Wilkinson 1993). Indeed, the gas kine-
+matics in barred galaxies is usually modeled using tools
+that are specifically designed to take into account non-
+axisymmetric distortions in the 2D velocity field (e.g.
+
+Molecular gas kinematics in jellyfish galaxies
+9
+Schoenmakers 1999; Spekkens & Sellwood 2007). How-
+ever, these methods fail when the bar is perpendicular
+to or parallel the disk major axis, being unable to break
+the degeneracy between the tangential and radial ve-
+locity components (e.g. Sellwood & S´anchez 2010; Ran-
+driamampandry et al. 2015). We thus decided to adopt
+the tilted-ring approach also in the case of JO201 and
+JO206, which host stellar bars aligned with the disk ma-
+jor axis.
+5. RESULTS AND DISCUSSION
+In this section, we present the best-fit models for the
+molecular gas kinematics and we then compare the stel-
+lar and molecular gas rotation curves. We discuss each
+galaxy individually in Sects. 5.1–5.4 and summarize our
+findings in Sect. 5.5. We analyzed both the CO(1–0)
+and the CO(2–1) datacubes, obtaining essentially the
+same results. Thus, we show the best-fit models for the
+CO(1–0) data, as they have a S/N and angular resolu-
+tion more suitable for modeling the kinematics. From
+here on, CO indicates CO(1–0) unless otherwise stated.
+Since the focus of this work is on the molecular gas, we
+show the best-fit model for the stellar kinematics only
+for JO201 in Fig 3, while the models for the rest of the
+sample can be found in Appendix A.
+5.1. JO201
+The I-band image in Fig. 2 shows that JO201 has
+a stellar bulge. Moreover, the elongated shape of the
+isophotes in the inner regions suggests that JO201 hosts
+a stellar bar, as reported by George et al. (2019).
+Sanchez-Garcia et al. (submitted) estimated that the
+bar length is ≈ 4.6 kpc. We also note that the stellar
+disc of JO201 seems morphologically lopsided, being the
+east side slightly more extended than the west one.
+The top panels in Fig 3 show, from left to right, the
+observed stellar velocity field, the best-fit model, and
+the map of the residuals between the data and the best-
+fit model. The bottom panels display the radial profile
+of the best-fit rotation velocity (left), inclination (cen-
+ter), and PA (right). The stellar velocity field is very
+well reproduced by the model. The residuals in the disk
+outskirts, where the Voronoi bins are the largest, tend
+to be higher than in the inner regions, but still within
+the velocity resolution of the MUSE observations, that
+is ∆v ≈ 50 km s−1. We note that, for R ≲ 5 kpc, the ro-
+tation velocity is much lower than expected for a galaxy
+with stellar mass M⋆ ≈ 9 × 1010 M⊙ and hosting a stel-
+lar bulge. This feature can be explained by the fact that
+the stellar bar is aligned along the disk major axis. In
+a scenario where a large fraction of the stars in the bar
+move on elliptical orbits aligned parallel to the bar (so
+called x1 type; Sellwood 2014), the velocity component
+along the line of sight has its minimum at the apocentre
+and then increases along the major axis. This can result
+in an underestimation of the rotation velocity in the re-
+gions influenced by the bar (e.g. Dicaire et al. 2008; Sell-
+wood & S´anchez 2010; Randriamampandry et al. 2015).
+The total CO intensity map (top left panel in Fig. 1)
+gives useful indications about the effect and direction of
+ram pressure. In JO201, the west side of the disk shows
+compressed contours and regions with bright CO emis-
+sion, possibly suggesting the ram pressure compressed
+this part of the disk (Bellhouse et al. 2017). The most
+evident feature in Fig. 1 is arguably the presence of the
+ring-like structure surrounding the hole in the CO dis-
+tribution in the innermost ≈ 3 kpc (see also George
+et al. 2018, 2019). The ring-like structure is also visible
+in the MUSE images shown by Bellhouse et al. (2017).
+This feature can be explained by the presence of the bar
+driving the formation of a molecular gas ring around the
+co-rotation radius (i.e. where the bar pattern equals the
+angular frequency of circular motions; see Sellwood &
+Wilkinson 1993; Kormendy & Kennicutt 2004). At radii
+well inside co-rotation, gas is expected to fall toward
+the center.
+The molecular gas distribution in barred
+galaxies is typically very concentrated in the center (e.g.
+Kormendy & Kennicutt 2004), while Figure 1 clearly
+shows the lack of CO emission in the innermost regions
+of JO201. George et al. (2019) attribute the CO cavity
+to AGN feedback, which ionizes the molecular hydro-
+gen (i.e. radiative feedback) and sweeps the gas from
+the center (i.e. mechanical feedback). The connection
+between nuclear activity and the gas distribution and
+kinematics is specifically tackled in the companion pa-
+per (Mingozzi et al. to be submitted).
+The CO velocity field of JO201 (2nd panel in the top
+row of Fig. 1) shows that the galaxy is kinematically lop-
+sided, meaning that the velocity gradient in the receding
+and approaching sides of the disc are significantly differ-
+ent from each other (e.g. Richter & Sancisi 1994; Swa-
+ters et al. 1999; Schoenmakers 1999; Shafi et al. 2015).
+For this reason, we modeled the approaching side and
+receding side separately. We compare the observations
+with our best-fit models in Fig. 4, where the left and the
+right panels are for the approaching and receding sides
+of the disc, respectively. The first and second rows in
+Fig. 4 are the position-velocity diagrams (PVDs) along
+the major and minor axis of the disc, respectively. Our
+rotating disc model can reproduce reasonably well the
+observations, indicating that the molecular gas in the
+disk preserved its original rotation, despite the interac-
+tion with the ICM. There is however some gas, which is
+
+10
+Bacchini et al.
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [kpc]
+0
+50
+100
+150
+200
+250
+Rotation velocity [km/s]
+Bar region
+2nd fit
+3rd fit
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [kpc]
+20
+30
+40
+50
+60
+70
+80
+Inclination [degrees]
+Bar region
+2nd fit
+Median
+3rd fit
+± MAD
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [kpc]
+160
+170
+180
+190
+200
+210
+Position angle [degrees]
+Bar region
+2nd fit
+Median
+3rd fit
+± MAD
+0h41m32s
+31s
+30s
+29s
+-9°15'30"
+45"
+16'00"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO201 - Data
+5 kpc
+150
+100
+50
+0
+50
+100
+150
+VLOS [km/s]
+0h41m32s
+31s
+30s
+29s
+RA (ICRS)
+JO201 - Model
+150
+100
+50
+0
+50
+100
+150
+VLOS [km/s]
+0h41m32s
+31s
+30s
+29s
+RA (ICRS)
+JO201 - Residuals
+40
+20
+0
+20
+40
+Data-Model [km/s]
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+15.0
+17.5
+R [arcsec]
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+15.0
+17.5
+R [arcsec]
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+15.0
+17.5
+R [arcsec]
+Figure 3. Top row: stellar velocity field (left), its best-fit model (center), and residual map (right) for JO201. The white
+star indicates the disc center. The black curves are the iso-velocity contours with steps of 50 km s−1. The thick black contour
+indicates Vsys. The white contours in the left panel shows the best-fit model on the data. The bar and the circle in the bottom
+left and right corners respectively show the physical scale and the PSF of the observations. Bottom row: rotation velocity (left),
+inclination (center) , and position angle (right) as a function of the galactocentric distance for the best-fit models of the stellar
+velocity field. The grey dashed area indicates the region influenced by the stellar bar. The empty circles and the red points are
+for the 2nd and the 3rd steps of our procedure (see Sect. 4.1), respectively. The dashed black lines and the grey area indicate
+the median and the median absolute deviation, respectively.
+indicated by the red arrow in Fig. 4, moving with lower
+velocities than those predicted by the model. Since this
+gas is located at galactocentric distances smaller than
+the bar length, its anomalous kinematics is plausibly
+due to the bar influence.
+By exploring the parameter space, we found that
+the best-fit value of the CO velocity dispersion is not
+well-constrained for the outermost ring, likely because
+of the low S/N. For R ≲ 5 kpc, we obtain σCO ≈
+25 − 40 km s−1, which can be explained by the non-
+circular motions due to the stellar bar. Outside the bar
+regions, we find σCO ≈ 20 km s−1, which is about a fac-
+tor 2 higher than the typical values of the molecular gas
+velocity dispersion in local isolated, unbarred galaxies
+(e.g. Bacchini et al. 2020a). This enhancement of σCO
+may be due to ram pressure increasing the molecular gas
+turbulence, either directly or by enhancing the star for-
+mation rate (SFR; see Sect. 5.5 for further discussion).
+We note that the best-fit values of radial velocity are
+consistent with zero, suggesting that the inclusion of
+radial motions does not significantly improve the fit.
+Hence, these values should be taken with caution. The
+direction (either inward or outward) of these radial flows
+cannot be determined unless the near/far sides of the
+galaxy are known. This can be inferred by assuming that
+spiral arms trail the galaxy rotation. Based on the RGB
+image shown by (Bellhouse et al. 2017), the direction of
+spiral arms indicate that JO201 rotates clockwise. Then,
+in 3DB’s convention (Di Teodoro & Peek 2021), radial
+motions with Vrad < 0 point inward, while those with
+Vrad > 0 point outward. Taken at face value, the inflow
+radial velocities at R ≲ 5 kpc are Vrad ≳ −10 km s−1,
+which is comparable with the average values measured in
+the inner regions of nearby spiral galaxies (Di Teodoro &
+Peek 2021). Beyond the bar region, the radial outflow
+with Vrad ≳ 20 km s−1is consistent with being caused
+by ram pressure. However, since non-circular motions
+can be induced by any perturbation of the gravitational
+potential, we cannot exclude a different origin (e.g. Sell-
+wood & S´anchez 2010).
+In Fig. 5 (top left), we compare the circular velocities
+inferred from the kinematics of the stellar and molecular
+gas disks. The stellar circular velocity was obtained from
+the rotation velocity shown in Fig. 3 by correcting for
+the contribution of pressure support (asymmetric drift
+
+Molecular gas kinematics in jellyfish galaxies
+11
+10
+5
+0
+5
+10
+Offset ["]
+300
+200
+100
+0
+100
+VLOS [km/s]
+= 178°
+Model fitted on the approaching side
+10
+5
+0
+5
+10
+Offset ["]
+300
+200
+100
+0
+100
+VLOS [km/s]
+= 180°
+Model fitted on the receding side
+10.0
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+10.0
+Offset ["]
+300
+200
+100
+0
+100
+VLOS [km/s]
+= 268°
+10.0
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+10.0
+Offset ["]
+300
+200
+100
+0
+100
+VLOS [km/s]
+= 270°
+0
+2
+4
+6
+8
+40
+60
+i [deg]
+0
+2
+4
+6
+8
+40
+60
+i [deg]
+0
+2
+4
+6
+8
+180
+200
+PA [deg]
+0
+2
+4
+6
+8
+180
+200
+PA [deg]
+0
+2
+4
+6
+8
+R [kpc]
+0
+50
+Vrad [km/s]
+Outflow
+Inflow
+0
+2
+4
+6
+8
+R [kpc]
+0
+50
+Vrad [km/s]
+Outflow
+Inflow
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+10
+5
+0
+5
+10
+R [kpc]
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+R [kpc]
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+10
+5
+0
+5
+10
+R [kpc]
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+R [kpc]
+JO201
+Figure 4. Best-fit models of the molecular gas kinematics for JO201 using CO(1–0) emission line observations. The left and the
+right panels are for the approaching and the receding sides of the disc (the other side is shaded), respectively. The first and the
+second rows show the PVD along the major and the minor axis, respectively. The observed CO(1–0) emission is shown in blue
+with black and grey contours, while the red contours show the best-fit model. All the contours are at 2nσch with n = 1, ..., 10
+and σch = 0.7 mJy/beam. The yellow points indicate the projected rotation curves of the best-fit models. The vertical blue
+dotted lines and the red arrows indicate the bar extent and the gas with anomalous kinematics (see text), respectively. In the
+last three rows, the panels show the profiles of inclination, PA, and radial velocity of the best-fit models. The red points are
+the parameters from the 1st fitting step and the dark-red lines are the regularized profiles (see Sect. 4.2). The orange and green
+areas in the bottom panels indicate whether positive/negative values for Vrad mean radial gas outflow/inflow.
+
+12
+Bacchini et al.
+0
+5
+10
+15
+0
+100
+200
+300
+Vcirc [km/s]
+JO201
+CO, app. side
+CO, rec. side
+Stars
+5
+10
+0
+100
+200
+300
+JO204
+CO
+Stars
+0
+5
+10
+15
+20
+R [kpc]
+0
+100
+200
+300
+Vcirc [km/s]
+JO206
+CO
+Stars
+0
+10
+20
+R [kpc]
+0
+100
+200
+300
+400
+JW100
+CO, app. side
+CO, rec. side
+Stars
+Figure 5. Comparison of the stellar (yellow stars) and the
+CO (darkred points) circular velocities for each galaxy in
+our sample.
+When the approaching side and the receding
+side of the disc are modelled separately, the resulting pro-
+files are shown by the blue squares and the red diamonds,
+respectively.
+correction)2. Within R ≈ 5 kpc, the molecular gas and
+stellar circular velocities essentially coincide, but the ve-
+locity gradient is too shallow for a massive galaxy with a
+bulge such as JO201. As mentioned above, this is likely
+due to the stellar bar aligned along the major axis (e.g.
+Dicaire et al. 2008; Sellwood & S´anchez 2010; Randria-
+mampandry et al. 2015). Beyond the bar regions, the
+stellar velocity field of JO201 (Fig. 3) does not show any
+indication of the kinematic lopsidedness, contrary to the
+molecular gas. The receding side of the CO disc reaches
+slightly higher rotation velocities than the stellar disc,
+while the approaching side shows a lower velocity gradi-
+ent. The kinematic lopsidedness in disc galaxies is typ-
+ically ascribed to a triaxial potential, as in the presence
+of a stellar bar (e.g. Swaters et al. 1999; Schoenmakers
+1999; Rhee et al. 2004). However, the regular kinematics
+of the stellar disk seems to suggest that the molecular
+gas kinematics may be perturbed by some mechanisms
+that does not affect the stars, like ram pressure. The
+distortions appear in the outer parts of the galaxy and
+in a symmetric way, as expected for face-on ram pressure
+(Kronberger et al. 2008b; Bellhouse et al. 2017, 2019).
+Indeed, JO201 is moving towards the observer at very
+2 We used Eq. A1 from Posti et al. (2018) for the asymmetric
+drift velocity and Eq. 3 from Mancera Pi˜na et al. (2021a) for the
+central velocity dispersion. We note that the asymmetric drift
+correction is essentially negligible for JO201 and all the other
+galaxies, as expected given their high rotation velocities.
+high velocity (see Table 1), implying that the approach-
+ing and receding sides of the disk move in the opposite
+and the same direction as the ram pressure, respectively.
+The ram pressure is thus expected to decelerate the ap-
+proaching side of the molecular disk and accelerate the
+receding side (Kronberger et al. 2008b), which is consis-
+tent with our results.
+We conclude that the molecular gas kinematics in the
+inner regions of JO201 is mainly dominated by the per-
+turbations due to the stellar bar.
+In the outer parts
+of the molecular gas disk, the kinematic lopsidedness
+and radial motions (although rather uncertain) seem to
+suggest that the molecular gas in JO201 is affected by
+face-on ram pressure, despite other mechanisms cannot
+be ruled out.
+5.2. JO204
+Before focusing on the molecular gas kinematics, it
+is worth noting two features of the stellar component.
+First, the innermost isophotes in the I-band image
+(Fig. 2) show a boxy shape that might indicate the pres-
+ence of a bar seen with high inclination with respect to
+the line-of-sight (e.g. Combes et al. 1990; Bettoni & Gal-
+letta 1994; Kuijken & Merrifield 1995; Bureau & Free-
+man 1999; Merrifield & Kuijken 1999). Unfortunately,
+dust obscuration and projection effects hamper any at-
+tempt to estimate the bar length from the optical im-
+ages. The second feature is visible in the stellar velocity
+field, which shows slightly distorted iso-velocity contours
+in the innermost regions (see Fig. 11). This S-shaped
+feature indicates the presence of non-circular motions
+and, possibly, of a stellar bar (e.g. Bettoni 1989; Vau-
+terin & Dejonghe 1997; Kormendy & Kennicutt 2004;
+Cort´es et al. 2015, Sanchez-Garcia et al. in preparation).
+Indeed, the top right panel of Fig. 11 shows residuals of
+a few tens of km s−1in the regions close to the disc mi-
+nor axis, indicating that a model based on circular orbits
+cannot fully reproduce the observations.
+In Fig. 1, the CO total intensity map shows that the
+molecular gas distribution is strongly concentrated in
+the center and two arm-like structures. Both features
+are typical of barred galaxies (e.g. Athanassoula 1992a;
+Bureau & Freeman 1999; Merrifield & Kuijken 1999; Ko-
+rmendy & Kennicutt 2004; Hogarth et al. 2021). The
+iso-velocity contours in the CO velocity field (Fig. 1) are
+visibly distorted in the inner regions, which typically in-
+dicates the presence of non-circular motions. The CO
+velocity dispersion is also quite high in the inner regions
+of disk.
+To model the CO kinematics, we modified the pro-
+cedure described in Sec. 4.2.
+After various tests, we
+decided to fit the data by fixing all the geometrical pa-
+
+Molecular gas kinematics in jellyfish galaxies
+13
+rameters and leaving free Vrot, Vrad, and σCO, as this
+choice improved the comparison between the model and
+the data. We run 3DB using the reverse option, which
+performs the fit starting from the most external ring
+and then moving inward. This algorithm was designed
+to improve the fit for galaxies seen with high inclination
+(i ≳ 70°). Fig. 6 compares the best-fit model with the
+observations. In Fig. 6, the PVD along the major axis
+shows that, overall, the model reproduces well the ob-
+servations, except for two features. The first feature is
+indicated by the red arrow and consists in gas moving at
+VLOS ≈ 270 km s−1at about 1 kpc from the center. One
+possibility is that this CO emission is probing the inner
+rise of the rotation curve of the molecular disk if the nu-
+clear CO distribution is asymmetric between approach-
+ing and receding sides (see for example Lelli et al. 2022).
+Alternatively, this central emission can be ascribed to
+complex non-circular motions caused by the stellar bar
+(the so-called x2 orbits aligned perpendicular to the bar;
+see Sancisi et al. 1979; Kormendy & Kennicutt 2004;
+Randriamampandry et al. 2015) or even feedback from
+stars or the AGN (e.g. Stuber et al. 2021). Our finding
+is in agreement with the results obtained by Deb et al.
+(2020), who revealed an absorption feature in the HI
+global profile that could be explained by high-velocity
+gas seen in front of the continuum emission from the
+AGN. The second feature that is not reproduced by the
+model is indicated by the magenta arrows. This emis-
+sion comes from gas that moves at lower velocities than
+those predicted by our model. A possible explanation
+is that this gas is decelerated by the ram pressure com-
+ponent in the sky plane. We note that the PVD along
+the major axis (top panel of Fig. 6) shows the charac-
+teristic X-shaped pattern, that is typical of a bar seen
+at high inclination along the line of sight (e.g. Bureau
+& Freeman 1999; Merrifield & Kuijken 1999; Kormendy
+& Kennicutt 2004; Alatalo et al. 2013; Hogarth et al.
+2021).
+In Fig. 6, the PVD along the minor axis shows ex-
+tended gas emission in the lower left quadrant, which
+can only be reproduced by a model with strong radial
+motions of Vrad ≳ 50 km s−1. However, the same feature
+is not observed in the upper right quadrant, indicating
+that the CO distribution (or kinematics) is asymmetric.
+Unfortunately, JO204 does not have visible spiral arms
+and the dust lanes in the optical MUSE and Hubble
+Space Telescope (HST) images (Gullieuszik et al. 2017,
+Gullieuszik et al., submitted) do not allow to clearly
+identify the nearest side of the disk.
+Hence, we can-
+not infer the direction of rotation and radial motions.
+Since these non-circular motions are detected in the in-
+ner parts of the galaxy, one may speculate that they
+10
+5
+0
+5
+10
+Offset ["]
+300
+200
+100
+0
+100
+200
+300
+VLOS [km/s]
+= 327°
+JO204
+10.0
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+10.0
+Offset ["]
+300
+200
+100
+0
+100
+200
+300
+VLOS [km/s]
+= 237°
+1
+2
+3
+4
+5
+6
+7
+8
+R [kpc]
+0
+100
+Vrad [km/s]
+300
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+10
+5
+0
+5
+10
+R [kpc]
+300
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+7.5
+5.0
+2.5
+0.0
+2.5
+5.0
+7.5
+R [kpc]
+Figure 6. Same as Fig. 4 but for JO204. The model fitting is
+performed on the approaching and receding sides at the same
+time, and the inclination and PA are fixed to the values of
+75° and 327°, respectively. The arrows indicate the gas with
+anomalous kinematics (see text). Here σch = 0.9 mJy/beam.
+are inflows driven by a stellar bar. The magnitude of
+radial motions in JO204 is consistent with the values es-
+timated in simulated barred galaxies (see Randriamam-
+pandry et al. 2015), but about 2 times higher than those
+measured by Di Teodoro & Peek (2021) in the atomic
+gas of real barred galaxies.
+The blue arrow indicates
+another feature that is not reproduced by our model.
+However, since this emission is very faint, it is unclear
+whether this is real emission from the galaxy. We find
+σCO ≈ 10 km s−1, but this value is rather uncertain
+based on the inspection of the parameters space.
+
+14
+Bacchini et al.
+Overall, our model can reproduce the molecular gas
+kinematics in JO204 reasonably well, despite the com-
+plexities due to the stellar bar and/or ram pressure. Fig-
+ure 5 (top right panel) shows that the CO circular veloc-
+ity is compatible within the uncertainties with the stel-
+lar circular velocity for R ≳ 3 kpc, indicating that the
+molecular gas has retained most of its original motion.
+The difference in the innermost regions is likely due to
+a combination of dust extinction and resolution effects,
+which may smooth the gradient of the stellar rotation
+curve (see Sect. 4). Similarly to the case of JO201, we
+conclude that the molecular gas kinematics is rotation-
+dominated in JO204.
+Then, the stellar bar plays an
+important role in perturbing the gas kinematics in the
+inner regions and driving radial gas flows, while the ram
+pressure may be a possible explanation for the gas with
+anomalous kinematics in the outskirts of JO204.
+5.3. JO206
+The I-band images in Fig. 2 shows that JO206 hosts
+a stellar bulge. In addition, the elongated shape of the
+isophotes in the inner regions indicate the presence of
+a stellar bar aligned with the disk major axis, as for
+JO201.
+The CO total intensity map in Fig. 1 shows
+that the morphology of the molecular gas distribution is
+asymmetric, suggesting that the ram pressure is directed
+towards south-east. Hence, we expect the molecular gas
+kinematics to be particularly complex in JO206, as a
+consequence of the combined effects of bar perturbations
+and ram pressure stripping. Indeed, the iso-velocity con-
+tours in the CO velocity field (2nd panel in the third row
+in Fig. 1) are even more distorted than those of JO204,
+indicating stronger perturbations.
+In the light of these considerations, we modeled only
+the regions of the molecular gas disk within R ≈ 6 ′′,
+which essentially corresponds to the extent of its re-
+ceding side (Fig. 1). We also adjusted the position of
+the kinematic center with respect to the optical center
+by applying a small shift of ≈ 0.23 ′′. Figure 7 shows
+that our model is able to reproduce reasonably well the
+observations, except for the molecular gas with anoma-
+lous kinematics. The CO emission indicated by the blue
+arrow (offset ≈ 10 − 20 ′′and -200 km s−1≲ VLOS ≲
+−100 km s−1) belongs to the tail of stripped gas (see also
+Fig. 1). Probably, this portion of gas disc was detached
+from the approaching side of the disc and decelerated by
+ram pressure. Another possibility is that the ram pres-
+sure displaced a portion of the disc at larger radii, thus
+its rotation velocity is lowered by conservation of angular
+momentum. The red arrow indicates the receding side
+of the molecular gas disk that has not been stripped. In
+the PVD along the minor axis (second panel in Fig. 7),
+the CO emission indicated by the orange arrow belongs
+to the molecular gas in the stripped tail left behind by
+the galaxy.
+By exploring the parameter space, we found that the
+best-fit value of σCO is well constrained only for the
+2nd and 3rd rings, where we obtained σCO ≈ 30 −
+40 km s−1(see also Fig. 1). These values are higher than
+those typically measured in nearby galaxies using CO
+observations with similar resolution (e.g. Bacchini et al.
+2020a), which is not surprising given the complex kine-
+matics of the molecular gas in JO206.
+We tentatively detect radial motions of ≈ −25 km s−1.
+However, including radial motions does not improve the
+best-fit model, as indicated by the fact that radial veloc-
+ities are consistent with zero. In JO206, the spiral arms
+can be identified from the MUSE optical images (Pog-
+gianti et al. 2017b; Bellhouse et al. 2019).
+Assuming
+trailing spiral arms, we can infer that the galaxy ro-
+tates clockwise, implying that Vrad < 0 for inflows and
+Vrad > 0 for outflows.
+The bottom left panel in Fig. 5 shows that the stellar
+and CO circular velocities coincide within R ≈ 6.5 kpc.
+As in the case of JO201 (see Sect. 5.1), the slow rise of
+the inner rotation curve is plausibly due to the fact that
+the stellar bar is aligned parallel to the disk major axis.
+This suggest that the kinematics of both the molecular
+gas and the stars is dominated by the stellar bar in these
+regions3. We also note that the position and velocity of
+the molecular gas emission indicated by the red arrow
+(Fig. 7, top panel) is perfectly compatible with the cir-
+cular velocity profile of the stars (see Fig. 5). On the
+contrary, the stripped tail indicated by the blue arrow
+(Fig. 7, top panel) is decelerated of about 70km s−1with
+respect to the stars at the same galactocentric distance,
+suggesting that this material is decoupled from the disk
+rotation. The asymmetric perturbations on the molec-
+ular gas kinematics and the displaced kinematic center
+are signatures of edge-on ram pressure stripping (Kron-
+berger et al. 2008b).
+Overall, we conclude that the molecular gas kinemat-
+ics is mainly perturbed by the stellar bar.
+Taken at
+face value, the radial motion in JO206 can be inter-
+preted as a gas inflows driven by the bar, as they are
+within its region of influence. We also find clear indi-
+cations of edge-on ram pressure stripping based on the
+presence of molecular gas emission detached from the
+galaxy and with kinematics decoupled from the main
+disk. This suggests that the ram pressure has a stronger
+3 This result is consistent with the preliminary estimate of the bar
+length obtain by Sanchez-Garcia et al. (in preparation), that is
+approximately 6.7 kpc.
+
+Molecular gas kinematics in jellyfish galaxies
+15
+10
+0
+10
+20
+Offset ["]
+300
+200
+100
+0
+100
+200
+300
+400
+VLOS [km/s]
+= 120°
+JO206
+10
+5
+0
+5
+10
+Offset ["]
+300
+200
+100
+0
+100
+200
+300
+400
+VLOS [km/s]
+= 210°
+0
+1
+2
+3
+4
+5
+6
+7
+60
+80
+i [deg]
+0
+1
+2
+3
+4
+5
+6
+7
+100
+150
+PA [deg]
+0
+1
+2
+3
+4
+5
+6
+7
+R [kpc]
+50
+0
+Vrad [km/s]
+Outflow
+Inflow
+300
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+10
+0
+10
+20
+R [kpc]
+300
+200
+100
+0
+100
+200
+300
+VLOS (km/s)
+10
+5
+0
+5
+10
+R [kpc]
+Figure 7. Same as Fig. 4 but for JO206. The model fitting
+is performed on both the approaching and receding sides, at
+the same time. Here σch = 0.8 mJy/beam.
+effect on the molecular gas disk in JO206 than in JO201
+and JO204.
+5.4. JW100
+The I-band image in Fig. 2 seems to suggest that
+JW100 hosts a stellar bulge. Moreover, despite the fact
+that JW100 is strongly affected by projection effects and
+dust obscuration, we can tentatively identify the pres-
+ence of a warp in the stellar disk based on the S-shape
+of the isophotes. Regarding the stellar kinematics, our
+model can successfully reproduce the observations and
+recover the stellar rotation curve (see Fig. 13 in Append-
+inx A). However, we found quite high residuals in a ring
+at R ≈ 6 ′′and in the disk outskirts. After various trails,
+we found no significant improvement in the residual map
+using different geometrical parameters and allowing for
+radial motions. This can be due to the combined effects
+of low S/N of the observations in the disk outskirts,
+strong projection effects due to the radial variation in
+disk inclination and PA, and asymmetric dust lanes (see
+Gullieuszik et al., submitted). Since JW100 belongs to
+a substructure of three galaxies in Abel 2626, we cannot
+rule out that the stellar kinematics is perturbed by tidal
+interaction.
+Figure 1 clearly shows that the distribution and kine-
+matics of the molecular gas in JW100 are strongly dis-
+turbed, suggesting that the ram pressure component in
+the sky plane is directed westward and contributes in
+pushing the gas outside the stellar disk.
+The case of
+JW100 may seem surprising, as the high mass of this
+galaxy is expected to produce a strong gravitational pull
+that can efficiently contrast the ram pressure stripping.
+However, the supersonic speed and the close proximity
+to the cluster center (see Table 1) indicate that JW100 is
+in the most favorable conditions for experiencing strong
+ram pressure. Indeed, the iso-velocity contours in the
+CO velocity field (2nd panel in the last row in Fig. 1) are
+even more distorted than the rest of the GASP-ALMA
+sample. Also the 2nd moment map suggests that the
+molecular gas velocity dispersion is very high through-
+out the disk, indicating very complex line profiles.
+We attempt to model the gas kinematics with the aim
+of understanding whether some gas has retained its orig-
+inal rotation. Hence, we run 3DB using the reverse
+option for highly inclined galaxies.
+We fixed the in-
+clination and PA at the values obtained for the stellar
+disc and shifted the kinematic center ≈ 1.6′′westward
+from the optical center.
+We performed the fitting on
+the approaching and receding sides separately, as the
+PVD along the major axis is asymmetric with respect
+to Vsys. The resulting best-fit models are shown in the
+left and right panels of Fig. 8, respectively. The models
+well reproduce the observations, except for the emission
+indicated by the blue arrow in the minor axis PVD. This
+emission comes from the molecular gas in the tail that is
+left behind by JW100 as it falls into the cluster receding
+from the observer. Indeed, the bottom panel in Fig. 8
+shows the profiles of the radial velocity, which reaches
+Vrad ≈ 50 − 100 km s−1in the disk outskirts. Taken at
+face value, the radial velocities are larger than the Vrad
+values of a few km s−1that are typically measured in
+
+16
+Bacchini et al.
+nearby galaxies (e.g. Di Teodoro & Peek 2021). Also
+the skewed shape of the CO emission in the PVD along
+the minor axis (blue arrows in Fig. 8) seem to suggest
+the presence of radial motions. We note that the emis-
+sion from the stripped gas indicated by the blue arrow
+reaches even higher velocities (∆VLOS ≈ −200 km s−1)
+than the model emission. The dust lanes in the HST im-
+ages (Gullieuszik et al., submitted) seem to suggest that
+the west side of JW100 is the nearest one and the galaxy
+is rotating clockwise. This implies that Vrad > 0 indi-
+cates an outward radial flow. This is in agreement with
+the morphology of the molecular gas disk, that clearly
+suggests an ongoing large-scale removal of molecular gas
+by ram pressure. We obtained σCO ≈ 30 − 60 km s−1,
+possibly indicating that the molecular gas is highly tur-
+bulent (see also Fig. 1).
+This is not surprising given
+the strong perturbations affecting the molecular gas in
+JW100.
+The bottom right panel in Fig. 5 compares the circu-
+lar velocity profile of the stellar disk and the molecular
+gas in JW100. We recall that different kinematic centers
+were used for the stellar and molecular gas components.
+Interestingly, the circular velocity of the approaching
+side of the molecular gas disk coincides with that of
+the stellar disk, flattening at Vcirc ≈ 300 km s−1. On
+the contrary, the circular velocity of the receding side
+keeps on growing and reaches Vcirc ≈ 400 km s−1. Sim-
+ilarly to JO206, the asymmetric perturbations on the
+molecular gas disk and the displaced kinematic center
+are signatures of edge-on ram pressure stripping (Kro-
+nberger et al. 2008b). This is consistent with the fact
+that JW100 is falling into the cluster at very high ve-
+locity and its disk is seen at high inclination by the ob-
+server. We note that the circular velocity of JW100 rises
+less steeply than what is typically found in galaxies with
+similar stellar mass. Moreover, Figure 2 seems to sug-
+gest that JW100 potentially hosts a stellar bulge, which
+is expected to produce high circular velocities in the in-
+nermost regions of the galaxy. The shallow and rather
+unusual gradient of the circular velocity might be ex-
+plained by either the presence of a stellar bar aligned
+with the major axis or a dark matter halo with lower-
+than-average concentration (Randriamampandry et al.
+2015).
+Disentangling between these two possibilities
+would require a dedicated mass modelling of the system
+which goes beyond the purpose of this study.
+In conclusion, our results indicate that the molecular
+gas disk of JW100 is dramatically affected by ram pres-
+sure. The morphology and kinematics of the molecular
+gas disk indicate strong ram pressure both in the sky
+plane and along the line of sight. Gravitational inter-
+actions with other members in the same substructure
+may play a role, but we speculate that these effects are
+milder than ram pressure, as the stellar component is
+not as strongly perturbed as the molecular gas.
+5.5. Summary
+In Sect. 5.1, we showed that the molecular gas kine-
+matics in JO201 is dominated by the bar for R ≲ 5 kpc.
+At larger galactocentric distances, the rotation curve
+gradient is modified by some physical mechanisms, that
+is possibly face-on ram pressure. We note that, since
+JO201 belongs to a cluster substructure, we cannot ex-
+clude a different origin (e.g.
+tidal interactions).
+We
+do not find clear signature of ram pressure stripping
+(i.e. molecular gas removed from the main disk), but
+we tentatively identify outward radial flow of gas plau-
+sibly due to ram pressure. Both within and beyond the
+region influenced by the bar, the velocity dispersion of
+the molecular gas is enhanced with respect to the typ-
+ical values measured in field galaxies (Bacchini et al.
+2020b), suggesting strong turbulence motions. Beyond
+the bar region, this enhancement is about a factor 2
+(σCO ≈20 km s−1), which can be either a direct or indi-
+rect consequence of ram pressure increasing (or a com-
+bination of both). Indeed, the ram pressure can directly
+increase the gas kinetic energy, but it can also enhance
+the SFR (e.g. Kronberger et al. 2008a) and thus the ve-
+locity dispersion due to the transferring of the supernova
+energy to the gas (Bacchini et al. 2020b). The SFR of
+JO201 is about 2 times higher than field galaxies with
+similar stellar mass, which supports the second scenario.
+In Sect. 5.2, we found clear signatures of the pres-
+ence of a bar in JO204 based on the molecular gas dis-
+tribution (central concentration, arm-like overdensities)
+and kinematics (PVD shape, radial motions), and the
+stellar kinematics (velocity field). Radial motions are
+clearly present, but we cannot identify their direction
+with the available observations. A bar-driven inflow is a
+reasonable hypothesis. The molecular gas kinematics is
+dominated by rotation, while the ram pressure plays a
+secondary role and we do not find signatures of ram pres-
+sure stripping. We detect molecular gas with anomalous
+kinematics that is compatible with being decelerated by
+face-on ram pressure. We also find some molecular gas
+with high velocity in the central regions of the galaxy,
+but its origin is unclear. The estimated values of the
+molecular gas velocity dispersion (σCO ≈10 km s−1) are
+rather uncertain, but overall consistent with those typ-
+ical of field galaxies (Bacchini et al. 2020b). This is in
+line with the fact that JO204 does not show enhanced
+SFR with respect to field galaxies (Vulcani et al. 2018).
+Similarly to JO201, the molecular gas kinematics in
+JO206 is dominated by the bar for R ≲ 6 kpc (Sect. 5.3).
+
+Molecular gas kinematics in jellyfish galaxies
+17
+15
+10
+5
+0
+5
+10
+15
+Offset ["]
+200
+0
+200
+400
+600
+VLOS [km/s]
+= 269°
+Model fitted on the approaching side
+15
+10
+5
+0
+5
+10
+15
+Offset ["]
+200
+0
+200
+400
+600
+VLOS [km/s]
+= 269°
+Model fitted on the receding side
+10
+5
+0
+5
+10
+15
+Offset ["]
+200
+0
+200
+400
+600
+VLOS [km/s]
+= 179°
+10
+5
+0
+5
+10
+15
+Offset ["]
+200
+0
+200
+400
+600
+VLOS [km/s]
+= 179°
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+R [kpc]
+0
+100
+Vrad [km/s]
+Outflow
+Inflow
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+R [kpc]
+0
+100
+Outflow
+Inflow
+600
+400
+200
+0
+200
+400
+VLOS (km/s)
+10
+0
+10
+R [kpc]
+600
+400
+200
+0
+200
+400
+VLOS (km/s)
+10
+5
+0
+5
+10
+15
+600
+400
+200
+0
+200
+400
+VLOS (km/s)
+10
+0
+10
+R [kpc]
+600
+400
+200
+0
+200
+400
+VLOS (km/s)
+10
+5
+0
+5
+10
+15
+JW100
+Figure 8. Same as Fig. 4 but for JW100. In the left and right panels, the model fitting is respectively done for the approaching
+and receding sides, and the kinematic center is ≈ 1.6′′westward from the optical center. The inclination and PA are fixed to the
+values of 77° and 179°, respectively. Here σch = 1.1 mJy/beam.
+This seems also to drive inward radial flows of molecular
+gas. We find clear signatures of edge-on ram pressure
+stripping for R > 6 kpc.
+The velocity dispersion of
+the molecular gas is significantly enhanced (σCO ≈30-
+40 km s−1), a likely consequence of the complex motions
+due to the combined influence of the bar and the ram
+pressure.
+In JW100 (Sect. 5.4), the molecular gas distribution
+and kinematics indicate ongoing ram pressure stripping.
+Since JW100 belongs to a cluster substructure and prob-
+ably hosts a warped stellar disk, we cannot exclude that
+gravitational interactions may also play a role. We de-
+tect radial motions that are compatible with an outward
+gas flow. The shallow gradient of the circular velocity
+in the inner regions of JW100 may be explained by a
+stellar bar aligned with the disk major axis, although
+other possibilities cannot be excluded (e.g. combination
+of resolution effects and ram pressure, low-concentration
+dark matter halo). The velocity dispersion of the molec-
+ular gas is quite enhanced (σCO ≈30-60 km s−1), but the
+SFR of JW100 is about 2.5 times lower than field galax-
+ies with similar stellar mass (Vulcani et al. 2018). These
+properties favours the scenario in which the gas turbu-
+lence is directly enhanced by the ram pressure.
+6. COMPARISON WITH PREVIOUS WORKS
+6.1. The connection between stellar bars and AGN
+At least three out of four galaxies in the GASP-ALMA
+sample host a stellar bar. In the case of JW100, the
+presence of the bar is difficult to confirm but arguably
+plausible, given that about 60% of the disk galaxies with
+10 ≲ log(M⋆/M⊙) ≲ 11 host a stellar bar (Aguerri et al.
+2009; Masters et al. 2012; D´ıaz-Garc´ıa et al. 2016). The
+fraction of barred galaxies may be even higher in the
+central regions of clusters (e.g. Andersen 1996; Barazza
+et al. 2009; M´endez-Abreu et al. 2012; Lansbury et al.
+2014; Alonso et al. 2014), but this is likely due to the
+increase of early-type galaxies (which are less likely to
+
+18
+Bacchini et al.
+host a bar) with decreasing clustercentric distance (e.g.
+Tawfeek et al. 2022).
+The non-axisymmetric potential of a stellar bar can
+trigger radial inflow of gas by inducing torques and
+shocks (e.g. Athanassoula 1992b,a; Sellwood & Wilkin-
+son 1993; Sellwood 2014; Marasco et al. 2018), often en-
+hancing the molecular gas concentration in the central
+regions of galaxies (e.g. Sheth et al. 2005; Regan et al.
+2006; Yu et al. 2022).
+Bar-driven inflows of gas may
+play an important role in fueling the central black hole
+and triggering the AGN activity (e.g. Alonso et al. 2013,
+2018; Rosas-Guevara et al. 2020; Silva-Lima et al. 2022).
+However, this topic is debated and some authors showed,
+for instance, that the excess of AGN-hosts among barred
+galaxies vanishes when the dependence on the galaxy
+stellar mass and color are taken into account (e.g. Ho
+et al. 1997; Lee et al. 2012). Moreover, there are indica-
+tions that the bar alone is not always sufficient to feed
+the black hole in an efficient way, requiring the contribu-
+tion of other mechanisms (Combes 2008; Sellwood 2014;
+Fanali et al. 2015; Galloway et al. 2015). This is because,
+in order to feed the black hole, the molecular gas in the
+disk needs to lose almost all its angular momentum (e.g.
+Sellwood & Wilkinson 1993; Krolik 1999; Sellwood 2014;
+Capelo et al. 2022). Using a sample of spiral galaxies,
+Alonso et al. (2014) found that their location within the
+group or cluster influences both the AGN and bar frac-
+tion. This result suggests that the external mechanisms
+affecting galaxies in dense environments may give a sig-
+nificant contribution to triggering the AGN activity. For
+the specific case of jellyfish galaxies, this external mech-
+anism might be the interaction with the ICM (Poggianti
+et al. 2017a; Peluso et al. 2022). Indeed, the ram pres-
+sure can not only compress the gas in the disk, but it
+can also make the gas lose its angular momentum and
+eventually move inward (Ramos-Mart´ınez et al. 2018;
+Ricarte et al. 2020; Farber et al. 2022, Akerman et al.
+submitted).
+Thus, the gas could easily reach the re-
+gion influenced by the bar, which may drag it further
+inward, perhaps reaching the black hole. This picture is
+in agreement with the enhanced fraction of AGN in ram
+pressure stripped galaxies (e.g. Poggianti et al. 2017a;
+Peluso et al. 2022, but see Roman-Oliveira et al. 2019
+for a different conclusion). The relative importance of
+internal mechanisms, such as bars, and external pro-
+cesses, such as ram pressure, in fueling the AGN activity
+is a compelling and debated topic (Alonso et al. 2018;
+Kim & Choi 2020; Boselli et al. 2022a), which would
+require higher statistics than the four galaxies studied
+here. This task goes beyond the scope of this paper and
+we leave it to future studies.
+6.2. Comparison with Virgo galaxies
+There is growing evidence that the ram pressure can
+affect the molecular gas in cluster galaxies. In this sec-
+tion, we compare the GASP-ALMA sample with the
+galaxies in Virgo cluster, in order to increase the statis-
+tics. Other cases of ram pressure affecting the molecu-
+lar disk have been found in Coma (J´achym et al. 2017),
+Norma (J´achym et al. 2014), and Fornax (Zabel et al.
+2019), just to mention some examples.
+Lee et al. (2017) studied the molecular gas kinemat-
+ics in three disk galaxies.
+These author did not find
+clear signs of molecular gas stripping, but they showed
+that the morphological and kinematical disturbances in
+the molecular and atomic gas disks are closely related
+to each other, suggesting that the molecular gas can be
+also affected by strong ram pressure even if it is not
+globally stripped. They also ascribed the perturbation
+in the innermost regions of their galaxies to the pres-
+ence of a stellar bar, rather than to ram pressure. As
+discussed in Sects. 5.1 and 5.2, our results for JO201
+and JO204 are consistent with Lee et al. (2017)’s find-
+ings. Interestingly, all the molecular gas disks in Lee
+et al. (2017) sample are kinematically lopsided, at least
+to some degree, indicating that the molecular gas was
+either accelerated or decelerated by ram pressure (see
+also Cramer et al. 2020). They also found CO clumps
+that are kinematically decoupled from the molecular gas
+disk, suggesting that this gas was displaced by the ram
+pressure, as in the case of JO206 (see Sect. 5.3).
+Recently, Brown et al. (2021) presented the first re-
+sults of the Virgo Environment Traced in CO (VER-
+TICO) survey, which maps CO emission in 51 galaxies
+in Virgo cluster using ALMA. This authors derived the
+mass-size relation for the molecular gas disk for VER-
+TICO galaxies.
+They showed that the scatter in the
+relation is minimized if the disk size is defined as the ra-
+dius where the azimuthally-averaged H2 surface density
+reaches ΣH2 = 5 M⊙pc−2 (R5). As a control sample,
+Brown et al. (2021) used the field galaxies in the Het-
+erodyne Receiver Array CO Line Extragalactic Survey
+(HERACLES, Leroy et al. 2009). Brown et al. (2021)
+found that the best-fit relations for the galaxies in Virgo
+and in the field are consistent. They concluded that R5-
+MH2 relation does not depend on the environment, in
+agreement with the studies on the HI size–mass relation
+(Wang et al. 2016; Stevens et al. 2019), and that galax-
+ies affected by environmental processes move along the
+size-mass relation rather than deviating from it.
+In Fig. 9, we compare our galaxies with the R5-MH2 re-
+lation from Brown et al. (2021). We assumed the Milky
+Way CO-to-H2 conversion factor for consistency with
+Brown et al. (2021). Our galaxies are within the scatter
+
+Molecular gas kinematics in jellyfish galaxies
+19
+of the R5-MH2 relation derived by Brown et al. (2021),
+confirming that this scaling relation does not show any
+clear dependence on environment, even in extreme ram
+pressure cases as the galaxies of our sample. We note
+that the GASP-ALMA sample tend to be slightly below
+the relation, suggesting that the molecular gas distri-
+bution is more centrally concentrated than the average
+for these samples.
+This can be due to the combined
+effect of stellar bars, which tend to increase the gas den-
+sity in the inner regions of the disk (e.g. Kormendy &
+Kennicutt 2004), and ram pressure, which compresses
+the molecular disk. The GASP-ALMA galaxies stand
+out against the other two samples because of their high
+MH2, being up to ≈ 0.5 dex more massive than the Virgo
+and control samples (see also Moretti et al. 2020a,b). On
+the other hand, it has been shown that our galaxies are
+up to 50% deficient in HI with respect to field galax-
+ies with similar mass and size (Ramatsoku et al. 2019,
+2020; Deb et al. 2020; Healy et al. 2021; Deb et al. 2022).
+Taken together, these results suggest an unusually ef-
+ficient conversion of HI to H2 (Moretti et al. 2020b).
+These properties are in agreement with the recent re-
+sults by Zabel et al. (2022) for Virgo galaxies.
+They
+found that the galaxies showing clear signs of ongoing
+ram pressure stripping affecting the HI disk are from
+H2-normal to H2-rich. This was interpreted as an indi-
+cation that ram pressure stripping is not effective at re-
+ducing global molecular gas fractions on the timescales
+in which such features are still clearly visible. This is
+likely because the stripping is less severe on H2 than on
+HI, as the molecular gas is denser and more gravitation-
+ally bound to the galaxy than the atomic gas (Lee et al.
+2017; Boselli et al. 2022a). The atomic gas disk of our
+galaxies show indeed signs of truncation and the ram
+pressure stripping is much more dramatic than for the
+molecular gas disk (Ramatsoku et al. 2019, 2020; Deb
+et al. 2020, 2022)
+6.3. Baryonic Tully-Fisher relation
+Rotation curves of disk galaxies are typically used
+to derive fundamental scaling relations (e.g. Verheijen
+2001; Lelli et al. 2016b; Ponomareva et al. 2017; Io-
+rio et al. 2017; Posti et al. 2018; Mancera Pi˜na et al.
+2021a,b; Di Teodoro & Peek 2021). In particular, the
+baryonic Tully-Fisher relation (hereafter BTFR) is a
+very tight correlation between the mass of baryons and
+the rotation velocity of galaxies, being a useful test-case
+to check the robustness of the stellar rotation derived
+in this work.
+The BTFR is usually derived using HI
+rotation curves, as the atomic gas disk is the most ex-
+tended baryonic component, allowing to probe the flat
+part of the galaxy rotation curve. In jellyfish galaxies,
+6.5
+7.0
+7.5
+8.0
+8.5
+9.0
+9.5
+10.0
+10.5
+11.0
+log[MH2/M
+]
+1.0
+0.5
+0.0
+0.5
+1.0
+1.5
+log[R5/kpc]
+Molecular gas size-mass relation using R5
+Brown+2021
+±
+JO201
+JO204
+JO206
+JW100
+Virgo
+Field
+Figure 9.
+Molecular gas mass-size relation based on R5
+(see Sect. 6.2).
+Each galaxy in the GASP-ALMA sample
+is indicated by a colored symbol. Grey diamonds and pink
+points show galaxies in the Virgo cluster and nearby field
+galaxies (see text), respectively.
+The best-fit relation ob-
+tained by Brown et al. (2021) for the VERTICO and HER-
+ACLES samples is shown by the dash-dotted line, while its
+scatter is represented by the shaded area.
+the atomic gas disk is stripped or truncated by the ram
+pressure and the HI kinematics is strongly perturbed,
+hampering the usage of HI observations to study scal-
+ing relations.
+The ionized gas is not a good alterna-
+tive to HI, as not only it is less spatially extended but
+also more diffuse and thus easier to strip. The results
+of this work suggest that the molecular gas is more re-
+silient to ram pressure, but its spatial extend is still very
+limited. Therefore, the stellar component is likely the
+best way to derive scaling relations in the case of jelly-
+fish galaxies, provided that observations with high spa-
+tial resolution and sensitivity are available. The GASP
+sample is ideal to perform this exercise, thanks to the
+high spatial resolution and sensitivity of the MUSE ob-
+servations.
+In Fig. 10, we show that the galaxies in
+the GASP-ALMA sample closely follow the BTFR de-
+rived by Di Teodoro et al. (2021) using a sample of
+about 200 galaxies from high-mass disks to dwarf galax-
+ies (Lelli et al. 2019). We calculated the velocity in the
+flat part of the rotation curve (Vflat) as the average of
+the outermost 5 measurements of the stellar rotation ve-
+locity (see Fig. 5). The baryonic mass was calculated as
+Mbar = M⋆ + 1.33 (MHI + MH2), where the masses of
+atomic gas (MHI) and molecular gas (MH2) are taken
+from Table 1 and the multiplicative factor 1.36 accounts
+for the Helium content.
+We checked that considering
+only the gas mass within the stellar disk or the total gas
+mass (including the gas in the stripped tail) does not
+
+20
+Bacchini et al.
+1.00
+1.25
+1.50
+1.75
+2.00
+2.25
+2.50
+2.75
+3.00
+log[Vflat/(km/s)]
+7
+8
+9
+10
+11
+12
+13
+log[Mbar/M
+]
+Baryonic Tully-Fisher relation
+Best-fit (Di Teodoro+21)
+y = 3.6x + 2.49
+JO201
+JO204
+JO206
+JW100
+= 0.1 dex
+Lelli+19
+Di Teodoro+21
+Figure 10.
+Baryonic Tully-Fisher relation for the four
+galaxies in the GASP-ALMA sample (triangles, diamond,
+and cross). The grey points show the spiral and dwarf galax-
+ies from Lelli et al. (2019), while the pink stars are for the
+massive disks from Di Teodoro et al. (2021).
+The dashed
+line is their best-fit relation with the shaded area showing
+the orthogonal intrinsic scatter.
+change the results, as the gas mass is largely dominated
+by molecular gas component which is mostly concen-
+trated within the galaxy disk.
+We also checked that
+our galaxies fall on the stellar Tully-Fisher relation (not
+shown here), which is not surprising given that the bary-
+onic mass is largely dominated by the stellar component.
+These simple tests indicate that the GASP sample can
+be used to study important scaling relations of baryons
+and, potentially, dark matter (e.g. Lelli et al. 2016b;
+Posti et al. 2018; Mancera Pi˜na et al. 2021a; Di Teodoro
+et al. 2022). This will be addressed in future work by
+fully exploiting the richness and quality of the MUSE
+observations obtained with the GASP survey (Bacchini
+et al., in preparation).
+7. SUMMARY AND CONCLUSIONS
+Galaxies in dense environments, such as clusters, can
+be affected by the ram pressure due to the interaction
+with the ICM. This process leaves the stellar disk es-
+sentially unperturbed, but it can have a strong impact
+on the morphology, kinematics and overall gas content,
+with important consequences on the evolution of galax-
+ies (Cortese et al. 2021). In this context, jellyfish galax-
+ies are ideal cases to study the impact of ram pressure
+on the gas components. In this work, we have studied
+the distribution and kinematics of the molecular gas in
+a sample of four jellyfish galaxies in the GASP sample
+(Poggianti et al. 2017b). These galaxies were observed
+with ALMA to detect the CO(1–0) and CO(2–1) emis-
+sion Moretti et al. (2020a,b). Thanks to the wealth of
+information obtained from MUSE and ALMA observa-
+tions provided by the GASP survey, we could analyze
+the stellar and CO distribution and kinematics. We used
+the software 3DB based on the tilted-ring approach to
+model the stellar velocity field and the CO emission line
+datacubes. We identified the gas with anomalous veloc-
+ity that cannot be explained by a rotation disk and used
+the information on the stellar distribution and kinemat-
+ics to understand the origin of this anomalous gas. We
+reached the following conclusions.
+1. At least three (JO201, JO204, and JO206) out
+of four galaxies in the GASP-ALMA sample are
+barred.
+In JO201 and JO206, the bars aligned
+with the disk major axis are visible in the I-band
+images and explain the shallow gradient of the cir-
+cular velocity in the inner regions of these galax-
+ies. In JO204, various bar signatures are found in
+the distribution of the molecular gas and the kine-
+matics of both the molecular gas and the stars. In
+JW100, the disk inclination and dust obscuration
+do not allow us to unambiguously identify a bar.
+2. The molecular gas kinematics in JO201 and JO206
+is mainly dominated by non-circular motions in
+the region influenced by the bar, while the ram
+pressure becomes important at larger galactocen-
+tric distance. The ram pressure plays a secondary
+role for the molecular gas kinematics of JO204,
+which is mainly rotation-dominated. Clear indi-
+cations of molecular gas stripping are found in
+two galaxies, JO206 and JW100. In JO206, some
+molecular gas is detached and kinematically de-
+coupled from the main disk. In JW100, the molec-
+ular gas disk is displaced with respect to the stel-
+lar disk and its kinematics is strongly perturbed.
+Since JO201 and JW100 belong to cluster sub-
+structures, other mechanisms than ram pressure
+might be also at play.
+3. Radial flows of molecular gas are manifestly
+present in two galaxies (JO204 and JW100), but
+this is less clear in the other two objects (JO201
+and JO206).
+These gas flows are consistent
+with being bar-driven inflows in JO206 and ram
+pressure-driven outflows in JO201 and JW100.
+The direction of radial motions remains unclear
+for JO204.
+4. The molecular gas velocity dispersion in JO201,
+JO206, and JW100 tends to be enhanced with re-
+spect to field galaxies, suggesting that the gas is
+very turbulent. In the case of JO201 and JO206,
+
+Molecular gas kinematics in jellyfish galaxies
+21
+this can be explained by the complex motions in-
+duced by the bar within its region of influence
+or, beyond the bar region, by the the ram pres-
+sure, which can enhance the gas turbulence di-
+rectly and/or by increasing the SFR. In the case
+of JW100, the most likely scenario is that the gas
+turbulence is directly enhanced by the ram pres-
+sure.
+5. Our galaxies fall within the scatter of the molec-
+ular gas mass-size relation derived for field and
+Virgo galaxies by (Brown et al. 2021), confirming
+that the relation is essentially independent of en-
+vironment.
+Overall, our results are consistent with a scenario in
+which the molecular gas is affected by ram pressure on
+different timescales and less severely than the atomic
+and ionized gas, likely because the molecular gas is
+denser and more gravitationally bound to the galaxy
+than the other gas phases. The galaxies in the GASP-
+ALMA sample host an AGN (Poggianti et al. 2017a;
+Peluso et al. 2022). Both stellar bars and ram pressure
+can contribute to efficiently drive molecular gas towards
+the galaxy center, possibly feeding the central black hole
+and triggering the nuclear activity. Since the relative im-
+portance of bars and ram pressure in fueling the AGN
+has not been fully understood yet, we hope that our
+work may foster future studies. In this work, we have
+shown that high-resolution observations of the molecular
+gas emission can be very useful in identifying stellar bars
+and radial flows. Future effort will be devoted to fur-
+ther study the bar-AGN connection by expanding the
+GASP-ALMA sample. Moreover, we have shown that
+the GASP sample is potentially very useful to investi-
+gate the impact of environment on scaling relations of
+galaxies. In future work, we plan to address this topic
+by fully exploiting the richness and quality of the MUSE
+observations obtained with the GASP survey.
+This paper makes use of the following ALMA data:
+ADS/JAO.ALMA#2017.1.00496.S. ALMA is a partner-
+ship of ESO (representing its member states), NSF
+(USA) and NINS (Japan), together with NRC (Canada)
+and NSC and ASIAA (Taiwan), in cooperation with the
+Republic of Chile. The Joint ALMA Observatory is op-
+erated by ESO, AUI/NRAO and NAOJ. CB acknowl-
+edges financial support from the European Research
+Council (ERC) under the European Union’s Horizon
+2020 research and innovation programme (grant agree-
+ment No.
+833824).
+CB would like to thank E. Di
+Teodoro, F. Rizzo, and F. Fraternali, for useful discus-
+sions and the help with the kinematic modeling.
+Facility: ALMA, MUSE@VLT
+Software:
+3DBarolo (Di Teodoro & Fraternali
+2015), APLpy (Robitaille & Bressert 2012), Astropy (As-
+tropy Collaboration et al. 2013, 2018).
+APPENDIX
+A. BEST-FIT MODELS OF THE STELLAR VELOCITY FIELD
+This section provides the best-fit model of the stellar disk for JO204, JO206, and JW100.
+The top panels in
+Figs. 11, 12, and 13 show the observed stellar velocity field, the best-fit model, and the map of the residuals. The
+bottom panels display the stellar rotation curve and the radial profiles of the PA and inclination. Overall, the stellar
+kinematics is well reproduced by our models. However, the residual map of JO204 clearly shows a pattern in the
+central regions of the disk, which likely indicates the presence of a stellar bar (see also Sect. 5.2). The residual map
+of JW100 highlights some regions where the model does not fully reproduces the observations. The origin of these
+differences is tricky to understand and may be due to asymmetric dust observation or the warp along the line of sight,
+or both (see also Sect. 5.4).
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+Alonso, M. S., Coldwell, G., & Lambas, D. G. 2013, A&A,
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+Alonso, S., Coldwell, G., Duplancic, F., Mesa, V., &
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+22
+Bacchini et al.
+0
+2
+4
+6
+8
+10
+12
+R [kpc]
+0
+50
+100
+150
+200
+250
+Rotation velocity [km/s]
+2nd fit
+3rd fit
+0
+2
+4
+6
+8
+10
+12
+R [kpc]
+70
+72
+74
+76
+78
+80
+Inclination [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+0
+2
+4
+6
+8
+10
+12
+R [kpc]
+318
+320
+322
+324
+326
+328
+Position angle [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+10h13m48.0s 47.5s
+47.0s
+46.5s
+46.0s
+-0°54'35"
+40"
+45"
+50"
+55"
+55'00"
+05"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO204 - Data
+5 kpc
+200
+150
+100
+50
+0
+50
+100
+150
+200
+VLOS [km/s]
+10h13m48.0s 47.5s
+47.0s
+46.5s
+46.0s
+RA (ICRS)
+JO204 - Model
+200
+150
+100
+50
+0
+50
+100
+150
+200
+VLOS [km/s]
+10h13m48.0s 47.5s
+47.0s
+46.5s
+46.0s
+RA (ICRS)
+JO204 - Residuals
+40
+20
+0
+20
+40
+Data-Model [km/s]
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [arcsec]
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [arcsec]
+0
+2
+4
+6
+8
+10
+12
+14
+16
+R [arcsec]
+Figure 11. Same as Fig. 3 but for JO204.
+0
+5
+10
+15
+20
+R [kpc]
+0
+50
+100
+150
+200
+250
+Rotation velocity [km/s]
+2nd fit
+3rd fit
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+15.0
+17.5
+20.0
+R [kpc]
+35
+40
+45
+50
+55
+60
+65
+70
+Inclination [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+0.0
+2.5
+5.0
+7.5
+10.0
+12.5
+15.0
+17.5
+20.0
+R [kpc]
+106
+108
+110
+112
+114
+116
+118
+120
+122
+Position angle [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+21h13m49s
+48s
+47s
+46s
+2°28'45"
+30"
+15"
+RA (ICRS)
+Dec (ICRS)
+1"
+JO206 - Data
+5 kpc
+200
+150
+100
+50
+0
+50
+100
+150
+200
+VLOS [km/s]
+21h13m49s
+48s
+47s
+46s
+RA (ICRS)
+JO206 - Model
+200
+150
+100
+50
+0
+50
+100
+150
+200
+VLOS [km/s]
+21h13m49s
+48s
+47s
+46s
+RA (ICRS)
+JO206 - Residuals
+40
+20
+0
+20
+40
+Data-Model [km/s]
+0
+5
+10
+15
+20
+R [arcsec]
+0
+5
+10
+15
+20
+R [arcsec]
+0
+5
+10
+15
+20
+R [arcsec]
+Figure 12. Same as Fig. 3 but for JO206.
+
+Molecular gas kinematics in jellyfish galaxies
+23
+0
+5
+10
+15
+20
+25
+R [kpc]
+0
+50
+100
+150
+200
+250
+300
+350
+400
+Rotation velocity [km/s]
+2nd fit
+3rd fit
+0
+5
+10
+15
+20
+25
+R [kpc]
+67.5
+70.0
+72.5
+75.0
+77.5
+80.0
+82.5
+Inclination [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+0
+5
+10
+15
+20
+25
+R [kpc]
+177
+178
+179
+180
+181
+182
+183
+184
+Position angle [degrees]
+2nd fit
+Median
+3rd fit
+± MAD
+23h36m26s
+25s
+24s
+21°09'15"
+00"
+08'45"
+RA (ICRS)
+Dec (ICRS)
+1"
+JW100 - Data
+5 kpc
+300
+200
+100
+0
+100
+200
+300
+VLOS [km/s]
+23h36m26s
+25s
+24s
+RA (ICRS)
+JW100 - Model
+300
+200
+100
+0
+100
+200
+300
+VLOS [km/s]
+23h36m26s
+25s
+24s
+RA (ICRS)
+JW100 - Residuals
+40
+20
+0
+20
+40
+Data-Model [km/s]
+0
+5
+10
+15
+20
+R [arcsec]
+0
+5
+10
+15
+20
+R [arcsec]
+0
+5
+10
+15
+20
+R [arcsec]
+Figure 13. Same as Fig. 3 but for JW100.
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