# Presentation: 659149

## High redshift (z~4) galaxies& clustering

- Lexi Moustakas
- STScI

- 17 may 04

## credit

- Everybody at GOODS & ODT!
- Soo Lee (JHU)
- (advisor: M. Giavalisco)
-  Paul Allen (MSO, PhD@Oxf)
-  Emily MacDonald (Oxf)
- (advisor: G. Dalton)

- 17 may 04

## see M. Giavalisco talk tomorrow!

**  ****GOODS: Giavalisco et al 2004**
**Montage courtesy of F. Summers**

**total GOODS: ~320 arcmin****2**

*see M. Giavalisco talk tomorrow!*

- 17 may 04

## Finding high-z galaxies: z~4

*Finding high-z galaxies: z~4*

- The Lyman-dropout technique, B-V vs V-z (for z~4) -- multiwavelength is KEY
- The space-based GOODS data use the z-band & are extremely deep compared to the ground -- ~2-3 mag fainter.
- In total GOODS ACS area, ~2000 z~4 galaxies

**B-dropouts, z~4**

**Giavalisco et al. 2004**

- 17 may 04

## LBG redshift distributions,from monte carlo simulations

- The redshift distributions are well-constrained through simulations.
- The completeness is more difficult to pin down.
- (The B-drops are the z~4).

**Giavalisco & S. Lee 2004**

- 17 may 04

## morphologies of faint z~4 galaxies

- The sizes of star forming galaxies above z~1 are sub-arcsec (Ferguson et al 2004)
- As shown here, the morphologies are varied and can be complex
- The pair/group statistics are crucial for characterizing environment

*Viz*

*1''*

**from the v1.0 GOODS data**

- Check out the scale!

- 17 may 04

## clustering of faint z~4 galaxies

- With the angular correlation function measured directly, and a simulated N(z), we invert & calculate the spatial correlation function
-                (r) = (r/r0)- ,
-      usually assumed to be a power-law on relatively large scales, with characteristic scale r0.

**S. Lee et al. 2004, in prep.**

**w(theta) vs angular separation**

**}**

- nb: many neighbors
- within 10-20arcsec!

- 17 may 04

## clustering with app. magnitude

- Clustering measured in the GOODS data to different magnitude limits.  (The error bars are smaller than the points!)
- There is evidence for stronger clustering in the brighter samples...  (See also Giavalisco & Dickinson 2001).

**GOODS data from S. Lee et al. 2004, in prep.**

**   ****spatial clustering vs **
**limiting apparent magnitude**

- 17 may 04

## clustering with abs. magnitude

- Transform (approximately) to rest-frame BJ magnitudes
- The brightest point is sub-L*
- What happens if one goes to much brighter absolute magnitudes??
- => We don't know from GOODS! Area is not large enough to find very rare objects...

**   ****spatial clustering vs **
**    ****absolute magnitude**
**       ****(approximate)**

- 17 may 04

## The Oxford-Dartmouth Thirty-Degree (ODT) SurveyMacDonald et al 2004, MNRAS, in press

- 5 limits           completion
-    ***vega***                  to date
- U > 25
- B    26.0
- V    25.5
- R    25.25           >23 deg2
*i*     24.5
- Z    22
- K  < 19               > 3.5 deg2

**MacDonald et al. 2004**
**Moustakas et al in prep (K-band part)**

- andr  0018+3452
- lynx  0909+4050
- herc  1639+4524
- virgo 1200+0300

- 17 may 04

## The ODT Survey: A wide-field multi- survey

- The Andromeda field of the ODT Survey

**A GOODS Field**

**MacDonald et al. 2004**

- 17 may 04

## clustering of bright z~4 galaxies

- Clustering measurements of B-drops in ODT Survey, from a ~2deg2 subset
-     Allen et al. 2004, MNRAS
- N(z)'s 'realized', and angular correlation function inverted.
- These LBG samples are bright, with i<24.5 (2mag brighter than GOODS)

**Allen et al. 2004**

**}**

-   nb: no neighbors
- within 10-20arcsec!

- 17 may 04

## L-dependent clustering at z~4

*L-dependent clustering at z~4*

**GOODS: S. Lee et al.**
**ODT:     P. Allen et al.**

- 17 may 04

## L-dependent clustering at z~4

- L* is around here

**GOODS: S. Lee et al.**
**ODT:     P. Allen et al.**

- 17 may 04

## L-dependent clustering at z~0

**z~0**

**GOODS: S. Lee et al.**
**ODT:     P. Allen et al.**
**2dF:      Norberg et al. 2002**

- 17 may 04

## cosmic variance in this result

- Assuming simple galaxy-halo correlation
- larger volumes      = less cosmic variance
- smaller clustering = less cosmic variance
- We calculate a *similar *level of cosmic variance across the z~4 result --
- GOODS: small volume but small clustering -> cv~20%
- ODT-S:  large volume but large clustering -> cv~40%
- To bring the high-L variance down to 20%, need >10 times more area!  But even that isn't enough.
- Why is that? -- Onwards, to:

- 17 may 04

## beyond sweet peas

- Clustering, (dark matter) masses, and environment
- With analytic LCDM, we can connect the clustering to the *minimum** dark matter halo **mass**.*
- Combining the clustering with the space densities, a Halo Occupation Distribution (HOD) formalism can constrain the number of galaxies per halo vs halo-mass
- Adding luminosity information to this, the Conditional Luminosity Function (CLF)
- Let's quickly consider the Halo Occupation formalism

- 17 may 04

## dark matter halo masses

**Moustakas & Somerville 2002**

- There can be many galaxies in each
- dark matter "halo", or none.  The
*average* behavior can be parametrized
- with the Halo Occupation Function,
- or Distribution
-    N(M>Mmin) = (M/M1)****
- Mmin - threshold halo mass
-                     ** from clustering
- M1   - 'typical' mass
-           ** from clustering & density
-      - mass function slope
-             **  from small-scale clustering!

**    ****"bias" comes from the clustering,**
**which fixes the 'minimum' DM halo mass**

**space density**

**bias**

- 17 may 04

## galaxies' dark matter halos

- Here we plot the results for z~0 ellipticals, z~1.2 EROs, and z~3 LBGs (LAM & Somerville '02)
- The occupation function parameters can be constrained through the measured clustering strength and the space density
- The SLOPE (a 'free' parameter in this plot), can be constrained by very small-scale statistics

**M&S02**

- 17 may 04

## clustering evolution

- The simplest model hasa galaxies following the dark matter they're associated with -- 'galaxy conserving model' (Fry 1996)
- See the behavior of populations with properties established at different redshifts.  Do they 'connect'?

**correlation scale**

**linear bias**

- 17 may 04

## Conclusions

- There is evidence for luminosity- dependent clustering in galaxies, at z~4 as well as locally
- Need 'complete' census at all scales
-                        => DEPTH
- >10s of square degrees or more will be required to characterize this:
-              => LARGE SOLID ANGLE
- To constrain the SLOPE of the occupation function, we need very sub-few-arcsec pair/group info.:
- 	  => HIGH SPATIAL RESOLUTION
- A multi-wavelength SNAP/JDEM/LEGASY type mission would clean this up...

- 17 may 04