alx-ai/arxiv_papers · Datasets at Hugging Face

text stringlengths 0 44.4k
Tran,K.,et al. 2010, ApJin press,arXiv:0909.4079
WadaT.,etal., 2008, PASJ,60,517
arXiv:1001.0006v2 [astro-ph.CO] 4 May 2010Draft version November 2, 2018
Preprint typeset using L ATEX style emulateapj v. 11/10/09
COMPARISON OF HECTOSPEC VIRIAL MASSES WITH SZE MEASUREMENT S
Kenneth Rines1,2, Margaret J. Geller2, and Antonaldo Diaferio3,4
Draft version November 2, 2018
ABSTRACT
We present the ﬁrst comparison of virial masses of galaxy clusters with their Sunyaev-Zel’dovich
Eﬀect (SZE) signals. We study 15 clusters from the Hectospec Clus ter Survey (HeCS) with
MMT/Hectospec spectroscopy and published SZE signals. We measu re virial masses of these clusters
from an average of 90 member redshifts inside the radius r100. The virial masses of the clusters are
strongly correlated with their SZE signals (at the 99% conﬁdence lev el using a Spearman rank-sum
test). This correlation suggests that YSZcan be used as a measure of virial mass. Simulations predict
a powerlaw scaling of YSZ∝Mα
200withα≈1.6. Observationally, we ﬁnd α=1.11±0.16, signiﬁcantly
shallower (given the formal uncertainty) than the theoretical pr ediction. However, the selection func-
tion of our sample is unknown and a bias against less massive clusters c annot be excluded (such a
selection bias could artiﬁcially ﬂatten the slope). Moreover, our sam ple indicates that the relation
between velocity dispersion (or virial mass estimate) and SZE signal has signiﬁcant intrinsic scatter,
comparable to the range of our current sample. More detailed stud ies of scaling relations are therefore
needed to derive a robust determination of the relation between clu ster mass and SZE.
Subject headings: galaxies: clusters: individual — galaxies: kinematics and dynamics — co smology:
observations
1.INTRODUCTION
Clusters of galaxies are the most massive virialized
systems in the universe. The normalization and evo-
lution of the cluster mass function is therefore a sen-
sitive probe of the growth of structure and thus cos-
mology (e.g., Rines et al. 2007, 2008; Vikhlinin et al.
2009; Henry et al. 2009; Mantz et al. 2008; Rozo et al.
2008, and references therein). Many methods exist
to estimate cluster masses, including dynamical masses
from either galaxies (Zwicky 1937) or intracluster gas
(e.g., Fabricant et al. 1980), gravitational lensing (e.g.,
Smith et al.2005;Richard et al.2010), andthe Sunyaev-
Zel’dovich eﬀect (SZE Sunyaev & Zeldovich 1972). In
practice, these estimates are often made using simple
observables, such as velocity dispersion for galaxy dy-
namics or X-ray temperature for the intracluster gas.
If one of these observable properties of clusters has a
well-deﬁned relation to the cluster mass, a large survey
can yield tight constraints on cosmological parameters
(e.g., Majumdar & Mohr 2004). There is thus much
interest in identifying cluster observables that exhibit
tight scaling relations with mass (Kravtsov et al. 2006;
Rozo et al. 2008). Numerical simulations indicate that
X-ray gas observables (Nagai et al. 2007) and SZE sig-
nals (Motl et al. 2005) are both candidates for tight scal-
ing relations. Both methods are beginning to gain ob-
servational support (e.g., Henry et al. 2009; Lopes et al.
2009; Mantz et al. 2009; Locutus Huang et al. 2009).
Dynamical masses from galaxy velocities are unbiased
kenneth.rines@wwu.edu
1Department of Physics & Astronomy, Western Washington
University, Bellingham, WA 98225; kenneth.rines@wwu.edu
2Smithsonian Astrophysical Observatory, 60 Garden St, Cam-
bridge, MA 02138
3Universit` a degli Studi di Torino, Dipartimento di Fisica G en-
erale “Amedeo Avogadro”, Torino, Italy
4Istituto Nazionale di Fisica Nucleare (INFN), Sezione di
Torino, Torino, Italyin numerical simulations (Diaferio 1999; Evrard et al.
2008), and recent results from hydrodynamical simula-
tions indicate that virial masses may have scatter as
small as ∼5% (Lau et al. 2010).
Previous studies have compared SZE signals to hydro-
staticX-raymasses(Bonamente et al.2008;Plagge et al.
2010) and gravitational lensing masses (Marrone et al.
2009, hereafter M09). Here, we make the ﬁrst compar-
ison between virial masses of galaxy clusters and their
SZE signals. We use SZE measurements from the lit-
erature and newly-measured virial masses of 15 clus-
ters from extensive MMT/Hectospec spectroscopy. This
comparison tests the robustness of the SZE as a proxy
for cluster mass and the physical relationship between
the SZE signal and cluster mass. Large SZ cluster sur-
veys are underway and are beginning to yield cosmologi-
calconstraints(Carlstrom et al.2010;Hincks et al.2010;
Staniszewski et al. 2009).
We assume a cosmology of Ω m=0.3, Ω Λ=0.7, and
H0=70 km s−1Mpc−1for all calculations.
2.OBSERVATIONS
2.1.Optical Photometry and Spectroscopy
We are completing the Hectospec Cluster Survey
(HeCS), a study of an X-ray ﬂux-limited sample of 53
galaxy clusters at moderate redshift with extensive spec-
troscopy from MMT/Hectospec. HeCS includes all clus-
ters with ROSAT X-ray ﬂuxes of fX>5×10−12erg
s−1at [0.5-2.0]keVfrom the Bright Cluster Survey (BCS
Ebeling et al.1998)orREFLEXsurvey(B¨ ohringer et al.
2004) with optical imaging in the Sixth Data Release
(DR6) of SDSS (Adelman-McCarthy et al. 2008). We
use DR6 photometry to select Hectospec targets. The
HeCS targets are all brighter than r=20.8 (SDSS cata-
logs are 95% complete for point sources to r≈22.2). Out
of the HeCS sample, 15 clusters have published SZ mea-
surements.2 Rines, Geller, & Diaferio
2.1.1.Spectroscopy: MMT/Hectospec and SDSS
HeCS is a spectroscopic survey of clusters in the red-
shift range 0.10 ≤z≤0.30. We measure spectra with

Tran,K.,et al. 2010, ApJin press,arXiv:0909.4079

WadaT.,etal., 2008, PASJ,60,517

arXiv:1001.0006v2 [astro-ph.CO] 4 May 2010Draft version November 2, 2018

Preprint typeset using L ATEX style emulateapj v. 11/10/09

COMPARISON OF HECTOSPEC VIRIAL MASSES WITH SZE MEASUREMENT S

Kenneth Rines1,2, Margaret J. Geller2, and Antonaldo Diaferio3,4

Draft version November 2, 2018

ABSTRACT

We present the ﬁrst comparison of virial masses of galaxy clusters with their Sunyaev-Zel’dovich

Eﬀect (SZE) signals. We study 15 clusters from the Hectospec Clus ter Survey (HeCS) with

MMT/Hectospec spectroscopy and published SZE signals. We measu re virial masses of these clusters

from an average of 90 member redshifts inside the radius r100. The virial masses of the clusters are

strongly correlated with their SZE signals (at the 99% conﬁdence lev el using a Spearman rank-sum

test). This correlation suggests that YSZcan be used as a measure of virial mass. Simulations predict

a powerlaw scaling of YSZ∝Mα

200withα≈1.6. Observationally, we ﬁnd α=1.11±0.16, signiﬁcantly

shallower (given the formal uncertainty) than the theoretical pr ediction. However, the selection func-

tion of our sample is unknown and a bias against less massive clusters c annot be excluded (such a

selection bias could artiﬁcially ﬂatten the slope). Moreover, our sam ple indicates that the relation

between velocity dispersion (or virial mass estimate) and SZE signal has signiﬁcant intrinsic scatter,

comparable to the range of our current sample. More detailed stud ies of scaling relations are therefore

needed to derive a robust determination of the relation between clu ster mass and SZE.

Subject headings: galaxies: clusters: individual — galaxies: kinematics and dynamics — co smology:

observations

1.INTRODUCTION

Clusters of galaxies are the most massive virialized

systems in the universe. The normalization and evo-

lution of the cluster mass function is therefore a sen-

sitive probe of the growth of structure and thus cos-

mology (e.g., Rines et al. 2007, 2008; Vikhlinin et al.

2009; Henry et al. 2009; Mantz et al. 2008; Rozo et al.

2008, and references therein). Many methods exist

to estimate cluster masses, including dynamical masses

from either galaxies (Zwicky 1937) or intracluster gas

(e.g., Fabricant et al. 1980), gravitational lensing (e.g.,

Smith et al.2005;Richard et al.2010), andthe Sunyaev-

Zel’dovich eﬀect (SZE Sunyaev & Zeldovich 1972). In

practice, these estimates are often made using simple

observables, such as velocity dispersion for galaxy dy-

namics or X-ray temperature for the intracluster gas.

If one of these observable properties of clusters has a

well-deﬁned relation to the cluster mass, a large survey

can yield tight constraints on cosmological parameters

(e.g., Majumdar & Mohr 2004). There is thus much

interest in identifying cluster observables that exhibit

tight scaling relations with mass (Kravtsov et al. 2006;

Rozo et al. 2008). Numerical simulations indicate that

X-ray gas observables (Nagai et al. 2007) and SZE sig-

nals (Motl et al. 2005) are both candidates for tight scal-

ing relations. Both methods are beginning to gain ob-

servational support (e.g., Henry et al. 2009; Lopes et al.

2009; Mantz et al. 2009; Locutus Huang et al. 2009).

Dynamical masses from galaxy velocities are unbiased

kenneth.rines@wwu.edu

1Department of Physics & Astronomy, Western Washington

University, Bellingham, WA 98225; kenneth.rines@wwu.edu

2Smithsonian Astrophysical Observatory, 60 Garden St, Cam-

bridge, MA 02138

3Universit` a degli Studi di Torino, Dipartimento di Fisica G en-

erale “Amedeo Avogadro”, Torino, Italy

4Istituto Nazionale di Fisica Nucleare (INFN), Sezione di

Torino, Torino, Italyin numerical simulations (Diaferio 1999; Evrard et al.

2008), and recent results from hydrodynamical simula-

tions indicate that virial masses may have scatter as

small as ∼5% (Lau et al. 2010).

Previous studies have compared SZE signals to hydro-

staticX-raymasses(Bonamente et al.2008;Plagge et al.

2010) and gravitational lensing masses (Marrone et al.

2009, hereafter M09). Here, we make the ﬁrst compar-

ison between virial masses of galaxy clusters and their

SZE signals. We use SZE measurements from the lit-

erature and newly-measured virial masses of 15 clus-

ters from extensive MMT/Hectospec spectroscopy. This

comparison tests the robustness of the SZE as a proxy

for cluster mass and the physical relationship between

the SZE signal and cluster mass. Large SZ cluster sur-

veys are underway and are beginning to yield cosmologi-

calconstraints(Carlstrom et al.2010;Hincks et al.2010;

Staniszewski et al. 2009).

We assume a cosmology of Ω m=0.3, Ω Λ=0.7, and

H0=70 km s−1Mpc−1for all calculations.

2.OBSERVATIONS

2.1.Optical Photometry and Spectroscopy

We are completing the Hectospec Cluster Survey

(HeCS), a study of an X-ray ﬂux-limited sample of 53

galaxy clusters at moderate redshift with extensive spec-

troscopy from MMT/Hectospec. HeCS includes all clus-

ters with ROSAT X-ray ﬂuxes of fX>5×10−12erg

s−1at [0.5-2.0]keVfrom the Bright Cluster Survey (BCS

Ebeling et al.1998)orREFLEXsurvey(B¨ ohringer et al.

2004) with optical imaging in the Sixth Data Release

(DR6) of SDSS (Adelman-McCarthy et al. 2008). We

use DR6 photometry to select Hectospec targets. The

HeCS targets are all brighter than r=20.8 (SDSS cata-

logs are 95% complete for point sources to r≈22.2). Out

of the HeCS sample, 15 clusters have published SZ mea-

surements.2 Rines, Geller, & Diaferio

2.1.1.Spectroscopy: MMT/Hectospec and SDSS

HeCS is a spectroscopic survey of clusters in the red-

shift range 0.10 ≤z≤0.30. We measure spectra with