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simulation.
8µm LF.Monochromatic 8 µm luminosity ( L8µm) is known to correlate well with
the TIR luminosity [1, 6], especially for star-forming gala xies because the rest-frame
8µmfluxaredominatedbyprominentPAHfeaturessuchasat6.2,7 .7and8.6 µm.The
leftpanelofFig.1showsastrongevoltuionof8 µmLFs.Overplottedpreviousworkhad
torelyonSEDmodelstoestimate L8µmfromtheSpitzer S24µmintheMIRwavelengths
whereSEDmodelingisdifficultduetothecomplicatedPAHemi ssions.Here,AKARI’s
mid-IR bands are advantageous in directly observing redshi fted restframe 8 µm flux in
one of the AKARI’s filters, leading to more reliable measurem ent of 8µm LFs without
uncertaintyfromtheSED modeling.
12µm LF.12µm luminosity ( L12µm) represents mid-IR continuum, and known to
correlate closely with TIR luminosity [11]. The middle pane l of Fig.1 shows a strong
evoltuion of 12 µm LFs. Here the agreement with previous work is better becaus e (i)
12µm continuum is easier to be modeled, and (ii) the Spitzer also captures restframe
12µm inS24µmat z=1.
TIRLF.Lastly,weshowtheTIRLFsintherightpanelofFig.1.Weused Lagache,
Dole, & Puget [8]’s SED templates to fit the photometry using t he AKARI bands
at>6µm (S7,S9W,S11,L15,L18WandL24). The TIR LFs show a strong evolution
comparedto localLFs. At 0 .25<z<1.3,L∗
TIRevolvesas ∝(1+z)4.1±0.4.FIGURE2. Evolutionof TIRluminositydensitybasedon TIRLFs (redcir cles),8µmLFs (stars), and
12µm LFs (filled triangles). The blue open squares and orange fill ed squares are for LIRG and ULIRGs
only,alsobasedonour LTIRLFs.Overplotteddot-dashedlinesareestimatesfromtheli terature:LeFloc’h
et al. [9], Magnelli et al. [10] , Pérez-González et al. [11], Caputi et al. [2], and Babbedge et al. [1] are
in cyan, yellow, green, navy, and pink, respectively. The pu rple dash-dotted line shows UV estimate by
Schiminovichet al.[13].Thepinkdashedlineshowsthe tota lestimateofIR(TIRLF)andUV [13].
Cosmic star formation history .We fit LFs in Fig.1 with a double-power law, then
integrate to estimate total infrared luminosity density at various z. The restframe 8
and 12µm LFs are converted to LTIRusing [11, 2] before integration. The resulting
evolution of the TIR density is shown in Fig.2. The right axis shows the star formation
densityassumingKennicutt[7].We obtain ΩIR(z)∝(1+z)4.4±1.0. Comparisonto ΩUV
[13] suggests that ΩTIRexplains 70% of Ωtotalatz=0.25, and that by z=1.3, 90% of
the cosmic SFD is explained by the infrared. This implies tha tΩTIRprovides good
approximationofthe Ωtotalatz>1.
In Fig.2, we also show the contributions to ΩTIRfrom LIRGs and ULIRGs. From
z=0.35 to z=1.4,ΩIRby LIRGs increases by a factor of ∼1.6, andΩIRby ULIRGs
increases byafactorof ∼10. Moredetailsarein Gotoet al. [3].
Spatially-Resolved Spectroscopy of an E+A (post-starburs t) System .We per-
formed a spatially-resolved medium resolution long-slit s pectroscopy of a nearby E+A
(post-starburst) galaxy system with FOCAS/Subaru [4]. Thi s E+A galaxy has an obvi-
ous companion galaxy 14kpc in front (Fig.3, left) with the ve locity difference of 61.8
km/s.
WefoundthatH δequivalentwidth(EW)oftheE+Agalaxyisgreaterthan7Å gal axy
wide (8.5 kpc) with no significant spatial variation. We dete cted a rotational velocity in
the companion galaxy of >175km/s. The progenitor of the companion may have beenFIGURE 3. (left) The SDSS g,r,i-composite image of the J1613+5103. The long-slit position s are
overlayed.The E+A galaxy is to the right (west), with bluer c olour. The companion galaxy is to the left
(east). (right) H δEW is plotted against D4000. The diamonds and triangles are f or the E+A core/north
spectra, respectively. The squares and crosses are for the c ompanion galaxy’s core/north spectra. Gray
lines are population synthesis models with 5-100% delta bur st population added to the 10G-year-old
exponentially-decaying( τ=1Gyr)underlyingstellarpopulation.SalpeterIMFandmet allicityof Z=0.008
areassumed.Onthe models,burstagesof0.1,0.25,0.5and2 G yraremarkedwiththefilled circles.
a rotationally-supported, but yet passive S0 galaxy. The ag e of the E+A galaxy after
quenching the star formation is estimated to be 100-500Myr, with its centre having
slightly younger stellar population. The companion galaxy is estimated to have older
stellarpopulationof >2 Gyrs ofagewithnosignificantspatialvariation(Fig.3, ri ght).
Thesefindingsareinconsistentwithasimplepicturewheret hedynamicalinteraction
createsinfallofthegasreservoirthatcausesthecentrals tarburst/post-starburst.Instead,
ourresultspresentanimportantexamplewherethegalaxy-g alaxyinteractioncantrigger
agalaxy-widepost-starburstphenomena.
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arXiv:1001.0008v2 [hep-th] 6 Jan 2010Multi-Stream Inflation: Bifurcations and Recombinations i n the Multiverse
Yi Wang∗
Physics Department, McGill University, Montreal, H3A2T8, Canada
In this Letter, we briefly review the multi-stream inflation s cenario, and discuss its implications in
the string theory landscape and the inflationary multiverse . In multi-stream inflation, the inflation
trajectory encounters bifurcations. If these bifurcation s are in the observable stage of inflation, then
interesting observational effects can take place, such as do main fences, non-Gaussianities, features
and asymmetries in the CMB. On the other hand, if the bifurcat ion takes place in the eternal stage
of inflation, it provides an alternative creation mechanism of bubbles universes in eternal inflation,
as well as a mechanism to locally terminate eternal inflation , which reduces the measure of eternal
inflation.
I. INTRODUCTION
Inflation [1] has become the leading paradigm for the
very early universe. However, the detailed mechanism
for inflation still remains unknown. Inspired by the pic-
ture of string theory landscape [2], one could expect that
the inflationary potential has very complicated structure
[3]. Inflation in the string theory landscape has impor-
tantimplicationsinbothobservablestageofinflationand
eternal inflation.
The complicated inflationary potentials in the string
theory landscape open up a great number of interest-
ing observational effects during observable inflation. Re-
searchesinvestigatingthecomplicatedstructureofthein-
flationary potential include multi-stream inflation [4, 5],
quasi-single field inflation [6], meandering inflation [7],
old curvaton [8], etc.