Eight billion years of galaxy evolution Eric Bell Borch, Zheng, Wolf, Papovich, Le Floc’h, &...

Eight billion years of galaxy Eight billion years of galaxy evolutionevolution

Eric BellEric BellBorch, Zheng, Wolf, Papovich, Le Floc’h, & Borch, Zheng, Wolf, Papovich, Le Floc’h, &

COMBO-17, MIPS, and GEMS teamsCOMBO-17, MIPS, and GEMS teams

Venice 28.03.06Venice 28.03.06

Eric Bell

Eric Bell Eric Bell Venice 28.03.06Venice 28.03.06

Some demographicsSome demographics

A bimodal galaxy A bimodal galaxy populationpopulation Red sequenceRed sequence

Non-star-formingNon-star-forming ~ color of ancient stars~ color of ancient stars

Blue cloudBlue cloud Star-formingStar-forming

-18 -20 -22-18 -20 -22Absolute magnitude in i-bandAbsolute magnitude in i-band

Blanton et al. 2003; ApJ, 594, 186Blanton et al. 2003; ApJ, 594, 186


Evolution I Evolution I

LabbLabbéé et al. 2006 et al. 2006

(M(M2

20

02

20

0 –

V)

– V

) rest

rest

-2-2

-2-2

-2-2

00

00

00

22

44

22

44

22

44

-22-22 -20-20 -18-18MMVV

Always a blue cloudAlways a blue cloud

Emergence of the red Emergence of the red sequencesequence-Some massive galaxiesSome massive galaxiesat all times…at all times…

z ~ 1z ~ 1

z ~ 1.8z ~ 1.8

z ~ 2.6z ~ 2.6


Evolution IIEvolution II

Bell et al. 2004Bell et al. 2004


Mass function: color splitMass function: color split

Borch et al.Borch et al.20062006

Local MFsLocal MFs

Weak evolutionWeak evolutionin blue guysin blue guys(~ disks)(~ disks)

Strong evolution Strong evolution in red guys at in red guys at L<2L* at leastL<2L* at least(~ spheroids)(~ spheroids)

Blue cloudBlue cloud

Red sequenceRed sequenceBundy et al.Bundy et al.

20062006


Evolution IVEvolution IV Always a pronounced blue Always a pronounced blue

cloudcloud Color redder with timeColor redder with time

Red sequence builds up with Red sequence builds up with timetime Color of ancient stars at every Color of ancient stars at every

epochepoch Build-up of x3 or so since z~1 Build-up of x3 or so since z~1

(Bell et al. 2004; Chen et al. (Bell et al. 2004; Chen et al. 2003; Willmer, Faber et al. 2003; Willmer, Faber et al. 2006; Blanton 2006; Bundy et 2006; Blanton 2006; Bundy et al. 2006)al. 2006)

In agreement with at least In agreement with at least some models (Cole et al. 00; some models (Cole et al. 00; Somerville et al. in prep)Somerville et al. in prep)

Chen et al. 03Chen et al. 03

Borch et al. 2006Borch et al. 2006

Blue cloudBlue cloud

Red sequenceRed sequence

Bundy et al.Bundy et al.20062006


Spitzer: new insights Spitzer: new insights

Spitzer 24Spitzer 24μμm data from the MIPS m data from the MIPS instrument team for the CDFSinstrument team for the CDFS

8383μμJy limit corresponding to 3MJy limit corresponding to 3M yr yr-1-1 at at

z~0.7 (Kroupa IMF ~ 0.5x Salpeter)z~0.7 (Kroupa IMF ~ 0.5x Salpeter)

Spitzer imageSpitzer image

COMBO-17 andCOMBO-17 andGEMS coverageGEMS coverage

Rieke et al. 2004; data described in Papovich et al. 2004Rieke et al. 2004; data described in Papovich et al. 2004


IR luminosity from 24IR luminosity from 24μμm fluxm flux

Rest-frame 12-15Rest-frame 12-15μμm m correlates strongly with correlates strongly with total IR luminosity in the total IR luminosity in the local Universe, with < x2 local Universe, with < x2 scatterscatter

Will be able to test IR flux Will be able to test IR flux estimates with Spitzer estimates with Spitzer 70,16070,160μμm, Apex 350m, Apex 350μμm m and 870and 870μμm and Herschel m and Herschel PACS and SPIREPACS and SPIRE

Chary & Elbaz 2001; Papovich & Bell 2002;Chary & Elbaz 2001; Papovich & Bell 2002;See also Dale et al. 2005See also Dale et al. 2005

Log

Log 1

010

L LIRIR

/L/L

LogLog1010 ννLLνν,15,15μμmm/L/L

<0.3 dex scatter<0.3 dex scatter


Evolution of IR LFEvolution of IR LF

IR LF very stronglyIR LF very stronglyevolvingevolving

Almost all SF is Almost all SF is in blue disksin blue disks

TotalTotal

Blue / diskBlue / diskLocalLocal

RedRed

Le Floc’h et al. 2005Le Floc’h et al. 2005Bell et al. 2005Bell et al. 2005


Split by colorSplit by color

Can compare Can compare integrated SFR integrated SFR with observed with observed mass growth: IR-mass growth: IR-derivedderived

Blue disks form Blue disks form starsstars

Stars end up in red Stars end up in red spheroid-spheroid-dominated galaxiesdominated galaxies

Bell et al., in prep., Le Floc’h et al. 2005Bell et al., in prep., Le Floc’h et al. 2005


The evolution of the mass The evolution of the mass function…function…

Can estimate evolution of the mass Can estimate evolution of the mass function function with timewith time

tt

t+dtt+dtFor each mass bin:For each mass bin:

Work out average dM*/dt Work out average dM*/dt - stacking - stacking averageaverage SFR SFR

Multiply by Multiply by ΔΔt to work out t to work out ΔΔM*M*


ResultsResults

Hypothesis 1: SF in red Hypothesis 1: SF in red red red

SF in blue SF in blue blue blue

log spacelog spacedensitydensity

log stellar masslog stellar mass

All galaxiesAll galaxies

Red galaxiesRed galaxies

Blue galaxiesBlue galaxies

z = 0.9 0.7 0.5 0.3 0.0z = 0.9 0.7 0.5 0.3 0.0

Obs. MFObs. MF

Pred. MFPred. MF


ResultsResults

Hypothesis 1: All SF Hypothesis 1: All SF red red

log spacelog spacedensitydensity

log stellar masslog stellar mass

All galaxiesAll galaxies

Red galaxiesRed galaxies

Blue galaxiesBlue galaxies

z = 0.9 0.7 0.5 0.3 0.0z = 0.9 0.7 0.5 0.3 0.0

Obs. MFObs. MF

Pred. MFPred. MF


The role of mergersThe role of mergers

Merger ratesMerger rates Morphologically-Morphologically-

messed up thingsmessed up things Close galaxy pairsClose galaxy pairs

Neither are perfectNeither are perfect

Patton et al. 2002Patton et al. 2002Bundy et al. 2004Bundy et al. 2004Le Fevre et al. 2000Le Fevre et al. 2000Conselice et al. 2003Conselice et al. 2003

Somerville et al. in prep.Somerville et al. in prep.

**



The role of mergersThe role of mergers

Merger ratesMerger rates Morphologically-Morphologically-

messed up thingsmessed up things Close galaxy pairsClose galaxy pairs

Neither are perfectNeither are perfect Current estimates Current estimates

suggest ~1/3 merger suggest ~1/3 merger per L* galaxyper L* galaxy

Patton et al. 2002Patton et al. 2002Bundy et al. 2004Bundy et al. 2004Le Fevre et al. 2000Le Fevre et al. 2000Conselice et al. 2003Conselice et al. 2003

Somerville et al. in prep.Somerville et al. in prep.

**



ConclusionsConclusions Galaxies come in 2 flavoursGalaxies come in 2 flavours

BlueBlue Star-forming (often very intense)Star-forming (often very intense) Disk-dominatedDisk-dominated Food for the red sequenceFood for the red sequence

Red Red Largely non-star-formingLargely non-star-forming Bulge-dominatedBulge-dominated Constant growth of red population through global suppression of SF Constant growth of red population through global suppression of SF

in blue guysin blue guys Physical mechanisms of suppressionPhysical mechanisms of suppression

EnvironmentEnvironment Gas consumptionGas consumption Mergers Mergers

~1/3 merger per L* galaxy~1/3 merger per L* galaxy


SFR vs. SFHSFR vs. SFH

Borch et al. 2006Borch et al. 2006


Always a pronounced Always a pronounced blue cloudblue cloud Color redder with timeColor redder with time

Red sequence builds Red sequence builds up with timeup with time Color of ancient stars Color of ancient stars

at every epochat every epoch

Evolution IIIEvolution IIIFaber, Willmer, Wolf et al. 2005Faber, Willmer, Wolf et al. 2005

Passive evolutionPassive evolution

See also Bell et al. 2004See also Bell et al. 2004

Eight billion years of galaxy evolution Eric Bell Borch, Zheng, Wolf, Papovich, Le Floc’h, &...

Documents

Transcript of Eight billion years of galaxy evolution Eric Bell Borch, Zheng, Wolf, Papovich, Le Floc’h, &...