Galaxy and Quasar Clustering at z=1

Alison CoilAlison CoilUniversity of ArizonaUniversity of Arizona

April 2007April 2007

Large-Scale Structure

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Why do galaxies cluster?

- initial fluctuations in early universe- gravity- cosmology- physics: galaxy formation

Why high redshift?

- time leverage- earlier phase of galaxy evolution- additional constraint on models

SDSS:

DEEP2: A Redshift Survey at z=1

Observational details:

• 3 sq. degrees • 4 fields on sky• primary z~0.7-1.4• ~7-9 Gyr ago • 40k redshifts

Collaboration b/w UC-Berkeley and UC-Santa Cruz using the DEIMOS spectrograph on the Keck II

telescope to study both galaxy properties and large-scale structure at z=1.

•~5·106 h-3 Mpc3

• 80 Keck nights - 3 years• One-hour exposures• RAB=24.1• high resolution - robust z’s

Survey is done - data is released!

DEEP2 Redshift Survey: z=0.7-1.3

Cone diagram of 1/12 of the full DEEP2 sample

Clustering Primer

(r) follows a ~power-law prescription locally: (r) = (r0/r) with r0~5 Mpc/h and ~1.8

r0 = scale where the prob. of a galaxy pair is 2x random

larger r0 = more clustered

Quantify clustering:-probability of two galaxies separated by r-relative to a random unclustered distribution-large on small scales, small on large scales

Clustering Primer

Trace different physics on different scales: - small scales (r < 100 kpc/h):

mergers + galaxy-galaxy interactions

- intermediate scales (100 kpc/h < r < 2 Mpc/h): radial profiles of galaxies w/in halos / clusters

- large scales (r > 2 Mpc/h): large-scale density field / cosmology /

host dark matter halo mass

Galaxies Come in 2 Distinct Types

Blue: star-forming, gas+dust, spiral, ‘late-type’

Red: non-star-forming, little gas/dust, elliptical, ‘early-type’

SDSS:Blanton et al.

2003

Bi-modal color distribution

colo

r

magnitude

red sequence

blue cloud

why?evolution?

DEEP2: same color bi-modality to z>1

Willmer et al. 2006 ApJ / Faber et al. 2006 ApJ

red

blue

bright faint redshift

# density red gals

Build-up of red galaxies since z=1 - galaxies moving from blue cloud to red sequence.

Galaxy Clustering as a Function of Color

Red galaxies are more clustered and havelarger velocity dispersion/fingers of god:

reside in overdense environments + groups. Detect coherent infall on large scales for blue and red galaxies.

First time this has been seen at z=1! Need precise z’s.

Blue Red

Galaxy Clustering as a Function of Color

Color-density relation strongly in place at z=1.

No color dependence w/in red sequence, but there is

w/in blue cloud. Green galaxies as clustered as red.

Which galaxies move to the red sequence by z=0?

Redder of the blue cloud + green galaxies.

Coil et al. in prep

(for MB<-20, L>L*, z=0.7-1.0)

red: r0=5.17 (0.26) =1.97 (0.04)

blue: r0=3.83 (0.19) =1.67 (0.05)

redblue

green

Galaxy Clustering as a Function of ColorQuantify minimum dark matter halos mass as a function of

galaxy color (for MB<-20): red: b=1.6, Mhalo>2 1012 Mo/h blue: b=1.3, Mhalo>4 1011 Mo/h- important for color bimodality theories and simulations of

gas accretion and star formation

Color-density relation is not caused by clusters - very few clusters at z=1. Either caused by groups or intrinsic galaxy or

halo property such as age/stellar mass/halo mass.

The ‘green’ population is distinct - as clustered as red galaxies, but kinematics of blue galaxies. Shows infall on large scales - likely at the edges of groups/filaments and falling in. Likely a

transition population moving to red sequence. Coil et al. in prep

QSO/AGN and Galaxy Evolution

QSO/AGN may be important in how galaxies evolve:

- many/most galaxies have SMBH- mBH-bulge relation

- simulations: feedback from AGN or SNe is needed to shut off SF and create the color-mag diagram

- mergers are needed to create ellipticals - may involve quasars as disk galaxies collide

Can test galaxy and QSO/AGN formation and evolution models with observed clustering

SDSS QSOs in DEEP2 fields

36 SDSS + 16 DEEP2 spectroscopic broad-line QSOs in the DEEP2 fields between z=0.6-1.4:

SDSS

DEEP2

(near M*)

Clustering of Galaxies around QSOs

Cross-correlation of DEEP2 galaxies and SDSS QSOs.

Errors include Poisson errors + cosmic variance.

Similar errors as surveys with 1000s of QSOs (eg. 2dF).

Divide by the clustering of DEEP2 galaxies around DEEP2 galaxies to get the bias of QSO hosts…

Coil et al. 2007 ApJ

Relative bias of QSOs to DEEP2 galaxiesQSO relative bias = 0.9 (0.2)

QSO absolute bias = 1.2 (0.3)

Cluster more like blue galaxies than red! (2) ---not what is found locally at z=0.

Constrains host type for QSOs (blue) and QSO host halo masses:

Min. halo mass = 5x1011 M0

Mean halo mass = 3x1012 M0

No dependence is seen on magnitude or redshift.

Coil et al. 2007 ApJ

Clustering of X-ray AGN in AEGIS

-24-16 MB

color

red

Nandra et al. 2006 ApJLBarger et al. 2003 AJ

Chandra survey in the EGS: 200 ks depth

Have ~10,000 galaxies and ~200 (so far) X-ray sources w/ redshifts.

Can measure the cross-correlation of X-ray AGN

with galaxies.

X-ray AGN hosts are bright and on red

sequence or massive end of blue cloud.

(even the faint ones: Lx~1042-44 erg/s,

fx~1.5 x 10-15 erg/s/cm2)

quasars

z=0.7-1.4

blue

Clustering of X-ray AGN in AEGISFirst results:-significant dependence with optical luminosity: brighter AGN (-20.5>MB>-23) are ~50% more

biased/clustered than fainter AGN (-17.5>MB>-20.5)

-X-ray AGN cluster more like red than blue galaxies -cluster more than QSOs!-redder X-ray AGN cluster more than bluer AGN-consistent w/ galaxies undergoinga QSO phase before settling on thered sequence w/ an AGN

Coil et al. in prep

QSO/AGN Formation and Evolution

Competing QSO/AGN formation and evolution models predict different clustering properties, through assumed accretion and lifetimes:

- all begin with major mergers- Kauffmann and Haenelt 2001 predict a strong luminosity-dependence to QSO clustering:

- assume an exponentially declining light curve, time=- M_B ~ gas mass accreted / - gas mass accreted ~ host halo mass - luminosity~halo mass

brighter QSOs cluster more

QSO Formation and EvolutionLidz, Hopkins et al. 2005 predict less luminosity-dependence (but still some), as the light curve is not exponential - bright and faint QSOs are similar objects in same halos, but in different stages of their evolution - similar clustering - bias at z~1 is too high (b~2) - X-ray AGN cluster like quasars

Croton et al. 2006 include a second mode for low-L AGN: if halo M > Mthreshold then no gas accretion (~5 1011 M0)

- gas is shock heated, shuts off SF, creates color bimodality, shuts off black hole accretion - no QSO - but there is a low-L AGN - predict blue galaxies have QSOs at z<2 and red galaxies have low-L AGN - good qualitative agreement with our results!

Clustering of QSOs constrains lifetimes, host halo mass, host galaxy type and differentiates between formation models.

Summary•Galaxies have a bimodal color distribution at z=1, similar to z=0. LF studies show that red galaxies have been forming since z=1.

•Red galaxies are more clustered than blue galaxies at z=1, with a steeper slope and stronger fingers of god.

•Galaxies that are likely to evolve from blue to red are the reddest of the blue galaxies and green galaxies.

•Color-density relation is not due to clusters!

•Galaxies that host QSOs at z=1 reside in the same mass halos as typical DEEP2 galaxies and have blue host galaxies.

•X ray-selected AGN cluster like red galaxies at z=1 - at later stage in evolution from QSOs?

•Place strong constraints on QSO/AGN formation models.