october 2006galaxy mergers workshop stsci starbursts, agn, and quiescent star formation in high...

October 2006 Galaxy Mergers WorkshopSTScI

Starbursts, AGN, and Quiescent Star Formation in

High Redshift Galaxy Clusters

Nicole HomeierACS Science Team

Johns Hopkins University


ACS Science Team ACS Science Team CollaboratorsCollaborators

Cluster/Galaxy EvolutionCluster/Galaxy EvolutionPI:PI: Holland Ford (JHU) Holland Ford (JHU) Co-PI:Co-PI: Garth Illingworth (UCSC) Garth Illingworth (UCSC)Ricardo Demarco Ricardo Demarco (JHU)(JHU)

Marijn Franx Marijn Franx (Leiden)(Leiden)

Brad Holden Brad Holden (UCSC)(UCSC)

Nicole Homeier Nicole Homeier (JHU)(JHU)

Simona Mei Simona Mei (JHU)(JHU)

Marc Postman Marc Postman (STScI)(STScI)

Alessandro Rettura (JHU)Alessandro Rettura (JHU)Piero Rosati Piero Rosati (ESO)(ESO)

Arjen van der Wel (JHU)Arjen van der Wel (JHU)Andrew Zirm (JHU)Andrew Zirm (JHU)


Do we need major gas-rich mergers to build up the RCS?

• Let’s look back ~8Gyr, z=1, and see what’s happening


z z ~ 1 Cluster Survey Targets~ 1 Cluster Survey Targets

ClusterCluster RedshiftsRedshiftsVelocityVelocity

DispersionDispersionX-ray Lum. X-ray Lum. (10(104444 erg/s) erg/s) ACS FiltersACS Filters Total Total

OrbitsOrbits

MS1054MS1054 0.831 0.831 (154)(154) 11121112 23.323.3 V,i,zV,i,z 24+1624+16

CL0152CL0152 0.837 0.837 (102)(102) 12501250 7.87.8 r,i,zr,i,z 24+1624+16

CL1604 CL1604 +4304+4304 0.897 0.897 (22)(22) ~100~100 2.02.0 V,IV,I 44

CL1604 CL1604 +4321+4321 0.924 0.924 (44)(44) 935935 <1.2<1.2 V,IV,I 44

CL0910CL0910 1.101 1.101 (10+)(10+) N/AN/A 1.51.5 i,zi,z 88

CL1252CL1252 1.235 1.235 (36)(36) 755755 2.52.5 i,zi,z 3232

CL0848-CL0848-A,BA,B

1.265 1.265 (~40)(~40) 640 (A)640 (A) 1.5 (A), 1.5 (A),

~1 (B)~1 (B) i,zi,z 2424


The Red Sequence in z ~ 1 Clusters

Elliptical

S0

Spiral

Blakeslee et al. 2003, Mei et al. 2006 a,b, Blakeslee et Blakeslee et al. 2003, Mei et al. 2006 a,b, Blakeslee et al. 2006, Homeier et al. 2006al. 2006, Homeier et al. 2006

Mean ZMean Zff>2.2-2.6>2.2-2.6


Mean Ages from the Scatter about the RCS

•use the intrinsic scatter about the CMR to constrain the average age and formation redshift

Homeier et al. 2006

Bursts, tmax<t<tend, BC03


The Red Sequence in z ~ 1 Clusters

Mean ZMean Zff>2.2-2.6>2.2-2.6

If these early-type galaxies formed via‘mergers’, it’s at highredshift, and not frommajor mergers of the type we see in the localuniverse.

Cluster E/S0s passivelyevolving to present day.

But there is evolution, not everything in massive cluster halosis passively evolving between z=1 and z=0.


Morphology-densityrelation for our sample at z ~ 1

Ellipticals haveabout same fractionas found locally.

S0 fraction islower at these redshifts.

Population built up by infalling spirals?

Postman + ACS Postman + ACS Team 2005Team 2005


How are the massive galaxies (not) evolving?

Comaz=0.33z=0.59z=0.83

Holden et al. 2006


• We don’t need gas-rich mergers to build up the high mass early-types in clusters from z=1 to z=0 (although some could be accommodated).

• Do the rest of the observations agree with this? Do we observe a significant fraction of gas-rich mergers in clusters?


Massive X-ray clusters at z=1

ClJ0152-1357, z=0.84 MS1054, z=0.831


Locating star-forming galaxies at z=1

• [OII] is available for the most galaxies, get it for free with a redshift survey– Spec surveys (e.g. Lubin et al. 2001,

Homeier, Demarco et al. 2005, Tran et al. 2005)

– Narrow-band imaging surveys (e.g. Crawford et al. 2006, Sato & Martin et al. 2006, Lotz et al. 2003)


Example: Morphologies of [OII] Example: Morphologies of [OII] galaxies in CL J0152galaxies in CL J0152

Homeier et al. 2005Homeier et al. 2005

15% merger candidates

30% in RCS 20% early-type

(but sub-L*)

70% visual spirals(3/5 compact early-typeshave Sersic n=1-2)


Looking for star formation at z=1

• [OII] is available for the most galaxies, get it for free with a redshift survey– Spec surveys (e.g. Lubin et al. 2001, Homeier, Demarco et al.

2005, Tran et al. 2005)– Imaging surveys (e.g. Crawford et al. 2006, Sato & Martin et al.

2006, Lotz et al. 2003)

Cluster galaxy SFRs from [OII] are already lower than field galaxy SFRs at z~1 (e.g. Lubin et al. 2001).

Extinction? Are we missing significant numbers of Extinction? Are we missing significant numbers of star-forming galaxies?star-forming galaxies?


Halpha SFRs forHalpha SFRs for4 lower mass EDisCS 4 lower mass EDisCS clusters @z~0.7clusters @z~0.7

Show lower SFRs than the field population

Starburst fraction within0.5R_200 < 5%

But no morphological info

Finn et al. 2005


Rest-frame U-B ColorsRest-frame U-B Colors

At a given absolute B At a given absolute B magnitude, the cluster magnitude, the cluster galaxies are significantly galaxies are significantly redder.redder.

Homeier et al. 2006Homeier et al. 2006

Even the bluest cluster populationEven the bluest cluster population(excluding the RCS late-types)(excluding the RCS late-types)is redder than the field population.is redder than the field population.

clustercluster

field

Sample of late-type galaxiesSample of late-type galaxiesin 4 clusters, and a comparisonin 4 clusters, and a comparisonfield samplefield sample


Halpha selection for MS1054

Can select SF galaxies, and alsoget an upper limit of the SFRsof the late-type spec. members

Blue - detectedOrange - undetected

Upper Limit ~8-10 M_sun/yr

Homeier, Finn, et al., in prep


35 Halpha sourcesin MS1054 field

13 spec. confirmedcluster members

6 obvious non-mem

7 spec non-mem

= 9 probable new


For Cl0152:15% of the [OII] population are merger/interaction candidates[OII] population is ~20% of the total cluster population >> gas-rich merger candidates are only ~3% of the total cluster population MB<-20.5

For MS1054:In the strongest Halphagalaxies, ~20% aremerger/interaction candidates


But what about optically completely obscured starbursts?

• Let’s check with MIPS– 24 micron = ~13 micron rest-frame– On a weak PAH feature


MIPS source extraction

• Cl0152 and MS1054, z=0.84• 2 overlapping pointings for each

cluster• 268 sources in Cl0152, 244 in

MS1054-- 70% in MS1054 have an ACS counterpart within (5” matching radius) – Only 4 (Cl0152) and 11 (MS1054) are

spec. cluster members


Negligible “hidden” star formation

7 sources with both MIPS and Halpha, 2 spec members

For the single galaxy with an Halpha- and MIR-derivedSFR, they agree quite well.

Still have to sift through all the MIPS-only detections, but most appear not to be cluster members (either too big or too faint), and most of the Halpha sources are not detected.

Conclusion: Negligible number of obscured starbursts in massive clusters at z=0.84


But a significant number of AGN?

9 MIPS sources that are either a spec mem, 9 MIPS sources that are either a spec mem, have a radio, or X-ray detection, and no Halphahave a radio, or X-ray detection, and no Halpha


Evolution in the AGN fraction?

Dressler et al. 1995, 1999, optical onlyDressler et al. 1995, 1999, optical only

Martini et al. 2006Martini et al. 2006X-ray selectedX-ray selected

Homeier et al., in prep

Optical, X-ray, Radio, MIR

But selection important


Starbursts, AGN, and Quiescent Star Formation in Massive Galaxy Clusters at

z=0.84


Close, Red Pair CandidatesClose, Red Pair Candidates

MS1054: 9 pairs observed; 5.5 expected

CL0152: 12 pairs observed; 5.7 expected

In both clusters, the number of pairs with sep < 20 kpc In both clusters, the number of pairs with sep < 20 kpc is ~2 times that predicted from MC simsis ~2 times that predicted from MC sims

Postman, Bartko et al., in preparationPostman, Bartko et al., in preparation


Monte Carlo SimulationsMonte Carlo Simulations1.1. Create a reference galaxy distribution that has the Create a reference galaxy distribution that has the

same global clustering properties as the actual data on same global clustering properties as the actual data on scales > 150 kpc but which erases correlations on scales > 150 kpc but which erases correlations on smaller scales. smaller scales.

2.2. This is achieved by shifting the observed positions This is achieved by shifting the observed positions using offsets randomly drawn from a Gaussian using offsets randomly drawn from a Gaussian distribution with distribution with ~ 50 - 100 kpc. ~ 50 - 100 kpc.

3.3. Compute the average of and standard deviation in the Compute the average of and standard deviation in the number of pairs as a function of separation and local number of pairs as a function of separation and local galaxy surface density from 1,000 such simulations.galaxy surface density from 1,000 such simulations.

4.4. Use the above results to estimate the significance of Use the above results to estimate the significance of features in the observed galaxy density vs pair features in the observed galaxy density vs pair separation relationship.separation relationship.

Postman, Bartko et al., in prep


Red Pair Sim ResultsKinematic pairs confirmedTran et al. 2006


Classification MethodologyClassification Methodology• Visual classification by Bartko done in F775W Visual classification by Bartko done in F775W

(Rest-frame B). (Rest-frame B). • Two classification categories:Two classification categories:

– Interaction:Interaction: galaxy with interaction feature (tidal tail, galaxy with interaction feature (tidal tail, irregular disk, etc.) even if no companion seenirregular disk, etc.) even if no companion seen

– Merger:Merger: at least 2 galaxies in close proximity with at least 2 galaxies in close proximity with interaction features (tidal tail, irregular disk, etc.)interaction features (tidal tail, irregular disk, etc.)

• Reliable automated merger classification is Reliable automated merger classification is challenging but becoming more feasible (e.g., challenging but becoming more feasible (e.g., Lotz et al. 2006). Nonetheless, visual Lotz et al. 2006). Nonetheless, visual classification is a competitive approach when classification is a competitive approach when sample size <5,000 objects.sample size <5,000 objects.


Classification MethodologyClassification Methodology

All galaxies with i < 24 magAll galaxies with i < 24 mag RCS galaxies with i < 24 magRCS galaxies with i < 24 mag

AS

YM

ME

TR

Y

CONCENTRATION CONCENTRATION

BU

MP

INE

SS

MS1054-0321 & RXJ0152-1357


Classification MethodologyClassification Methodology


Merger and/or Interacting System Candidates

CL0152

MS1054

Green highlights the spectroscopically confirmed cluster members; others are Green highlights the spectroscopically confirmed cluster members; others are cluster member candidates based on their photo-z’s.cluster member candidates based on their photo-z’s.


Merger Fraction by Morphology Class and Cluster RadiusMerger Fraction by Morphology Class and Cluster Radius

MS1054-0321 (z = 0.831)

<f200> = 0.13 0.08

RXJ0152-1357 (z = 0.836)

<f200> = 0.20 0.07

R/R200


Merger Fraction & RateMerger Fraction & Rate• Completeness & projection corrected fraction Completeness & projection corrected fraction

of mergers (and excess close-pairs) within Rof mergers (and excess close-pairs) within R200 200

and with Mand with MVV < -20.3 are: < -20.3 are:– ffm m = 0.13 +/- 0.08 in MS1054 (Lum frac = 0.08) = 0.13 +/- 0.08 in MS1054 (Lum frac = 0.08)

– ffm m = 0.20 +/- 0.07 in CL0152 (Lum frac = 0.11)= 0.20 +/- 0.07 in CL0152 (Lum frac = 0.11)

• Merger rate = nMerger rate = nclcl f fmmTTmm-1 -1

(e.g., Lotz et al. 2006)(e.g., Lotz et al. 2006)

– 2.5 (± 2.0)2.5 (± 2.0) GyrGyr-1-1 Mpc Mpc-2-2 in MS1054 in MS1054– 7.9 (± 4.8) Gyr7.9 (± 4.8) Gyr-1-1 Mpc Mpc-2-2 in CL0152 in CL0152

• Early type mergers are largely confined to the Early type mergers are largely confined to the central ~600 kpc, consistent with the known central ~600 kpc, consistent with the known morphology-density relation. morphology-density relation.

Postman, Bartko et al., in prep


Brightest Cluster Brightest Cluster GalaxiesGalaxies

CL0152-13 CL0152-13 z = 0.837z = 0.837

EE

EE

EE EE

EE

S0/ES0/E

S0/SaS0/Sa

Sb/ScSb/Sc

MS1054-03 MS1054-03 z = 0.831z = 0.831

CL1226+3CL1226+33 3 z = 0.888z = 0.888

CL16h+43CL16h+430404 z = 0.895z = 0.895

CL0848+4CL0848+44 4 z = 1.265z = 1.265

CL1252-29 CL1252-29 z = 1.235z = 1.235

CL0910+5CL0910+544 z = 1.10z = 1.10

CL16h+43CL16h+4321 21 z = 0.924z = 0.924

z ~ 1 BCG exhibit a broader morphological z ~ 1 BCG exhibit a broader morphological distribution than their z=0 counterparts.distribution than their z=0 counterparts.

MM22 - M - M11 in the majority z~1 clusters is in the majority z~1 clusters is smaller (<0.35 mag) than that in ~85% of smaller (<0.35 mag) than that in ~85% of the z~0 rich Abell clustersthe z~0 rich Abell clusters

Evidence for eventual near equal mass Evidence for eventual near equal mass merger with BCG seen in at least 2 of merger with BCG seen in at least 2 of these 8 clusters (CL1252 and CL0848). these 8 clusters (CL1252 and CL0848). Significant tail of underluminous BCGs Significant tail of underluminous BCGs relative to low-z BCG luminosity relative to low-z BCG luminosity distribution (after modeling expected distribution (after modeling expected evolution).evolution).

Many of these BCGs will undergo a Many of these BCGs will undergo a significant increase in mass before z~0.5.significant increase in mass before z~0.5.

Postman et al., in prep


ConclusionsConclusions• Negligible number of starbursts, but there is quiescent SF and

AGN at z=1 in clusters at z=0.84.

• Dust levels and extinction levels are low in most SF-galaxies, and SFRs are low.– for the 1 galaxy in MS1054 where we have an Halpha SFR

and a mid-IR SFR, they agree very well • We do observe mergers. MS1054 & CL0152 have comparable

merger fractions within R200. The mergers account for ~10% of the cluster light.

• Early-type mergers are generally confined to central regions. • BCGs in many z~1 clusters still undergoing significant mass

assembly.


Quasars and RCS Galaxies

• If all massive early-types have SMBHs

• And all SMBHs and their hosts go through a quasar phase

• And massive clusters have 50-100 RS members at z=1 with zf=2-5, span of ~3Gyr

• # of galaxies going through a quasar phase >(50-100*tau)/3, tau=0.3, #>5-10 for some significant length of time

3

10

tau100Myr 300Myr


BCG Luminosity EvolutionBCG Luminosity Evolution

LeftLeft:: The rest frame absolute B-band metric magnitude (14 kpc aperture) as a function of redshift for our The rest frame absolute B-band metric magnitude (14 kpc aperture) as a function of redshift for our z~1 sample and for solar metallicity models with varying star formation histories.z~1 sample and for solar metallicity models with varying star formation histories.

RightRight:: The magnitude difference between the tau=0.6, z The magnitude difference between the tau=0.6, zFF=4.5 model and other models and the data. The =4.5 model and other models and the data. The flux ratio corresponding to the magnitude difference is shown on the right ordinate. Also shown is the flux ratio corresponding to the magnitude difference is shown on the right ordinate. Also shown is the histogram of z~0 BCG magnitude differences (similarly normalized) along with the location of the Coma histogram of z~0 BCG magnitude differences (similarly normalized) along with the location of the Coma cluster BCG. Horizontal dashed lines show the 1 and 2 sigma levels. cluster BCG. Horizontal dashed lines show the 1 and 2 sigma levels. Different from Gaussian at 98% C.L.Different from Gaussian at 98% C.L.


Use 8mum to identify probable AGN

- also to help matching accuracy

Brand et al. 2006


From observed 24mum to SFR

• Go from observed 12mum to 15mum flux density by using Dale et al. 2001 SEDs (factor of 2.7 difference in 13/15 flux densities over the range of SEDs, from quiescent to active)

• Empirical 15mum flux density vs. FIR luminosity (Elbaz et al. 2002)

• Use LFIR-SFR relation (Kennicutt 1998)


From observed 24mum to SFR

SEDs from Dale et al. 2001


What are the “new” late-type galaxies?

Red - ellipticals

Blue - spiralsBlack - mergers

Orange - S0s

Zooming in on z=0.8


How are the massive galaxies evolving?

Comaz=0.33z=0.59z=0.83

Holden et al. 2006


How are the massive galaxies (not) evolving?

Comaz=0.33z=0.59z=0.83

Holden et al. 2006


Conclusions

• Fraction of massive early-type galaxies flat with redshift.

• The evolution predominately occurs in lower mass systems.

• Typical mass of the late-types that appear at cluster outskirts similar to that S0 galaxies at z=0

• Galaxies at z=0 of the mass of late-type galaxies at z=0.8, have ages of 5-7 Gyr, less than the lookback time to z=0.8


Butcher-Oemler effectButcher-Oemler effect

Ellingson et al 2001, see also Andreon & Ettori 2004Ellingson et al 2001, see also Andreon & Ettori 2004

B-O effect is detected if one countsB-O effect is detected if one countswithin rwithin r200200, but the effect disappears if , but the effect disappears if 0.5r0.5r200200 is used is used

Determining population fractions is Determining population fractions is uncertain,uncertain,without a large spec sample one must usewithout a large spec sample one must usestatistical background subtraction, then statistical background subtraction, then therethereis the problem with what is “blue”.is the problem with what is “blue”.

Possibly a better method for quantifyingPossibly a better method for quantifyingcluster galaxy evolution is to look at the cluster galaxy evolution is to look at the total cluster star formation rate.total cluster star formation rate.

october 2006galaxy mergers workshop stsci starbursts, agn, and quiescent star formation in high...

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