Z-FOURGE - the FourStar Galaxy Evolution Survey

Status Report at the 1.3-year mark

Team

• Ivo Labbe (PI) & Caroline Straatman - Leiden

• Persson, Murphy, Monson, Kelson, McCarthy, Quadri - Carnegie

• Lee Spitler, Karl Glazebrook, Glenn Kacprzak, Greg Poole - Swinburne

• Casey Papovich, Kim-Vy Tran, Vithal Tilvi - Texas A&M

• Pieter van Dokkum - Yale

Galaxy evolution at 1 < z < 3.5

• Redshifts and high quality imaging for thousands of galaxies

• Redshifts, photometry plus models give the following:• Luminosity and LF • Stellar Mass and MF• Star Formation Rate• Extinction• Formation redshift

• Imaging data gives:• Galaxy size• Morphology• Environment

The key: Photometric Redshifts

Enable large samples of galaxies (not feasible with NIR spectroscopy)

• Observations

• Medium bandwidth (/ ~ 10) near-IR filters enable:• z/(1+z) = 0.01 - 0.02• More accurate photo-z than broadband filters

• Existing ground-based optical, Hubble, and Spitzer data

• Techniques

• 4000 or Balmer break in near-IR, overall SED

Model SEDs and Filters

FourStar Observations

• FOV 10.8’ x 10.8’ (4K x 4K)

• scale 0.159”/pixel

• Six filters: J1, J2, J3, Hs, Hl, plus Ks

• ~10 hours per filter

• Median seeing in Ks: 0.5” FWHM

• Deepest Ks image: 25.4 AB, 5 total for a point source

First result - a z ~ 2.2 cluster in COSMOS(Spitler et al. 2012, ApJ, 148, L21)

Deep Optical HST

FourStar J1,J2,J3

FourStar Ks, 10 hr / ACS I, 1 hr

Data and SED fits(medium bands are red points)

Results

• A & B are robust, C slightly less so. Possible overdensity D has the most luminous galaxy in the vicinity.

• Spectra of 4 galaxies confirm cluster redshift.

• Halo mass estimates 6x, 1x, and 1x 1013 Msun; may grow 10x to z = 0.

• Simulations suggest high probability that one or more of ABC will merge by z = 0.

Two interesting objects

A Z-band (Ly) dropout at z ~ 7.1 A T7 brown dwarf

Project Status

• COSMOS: 13,500 galaxies, 6500 at z > 1, several at z ~ 3.5 (age of universe ~ 1.8 Gyr).

• CDF-S: 9,000 galaxies, no large mature cluster detected (expect 1±1 over the three fields).

• UDS: next and final field in 2012B.

• Upon completion, we will have > 15,000 with z > 1 – Divided into 5 bins of mass, redshift, and environment gives 120/bin

=> robust statistics

Metal-poor star-forming galaxies

[OIII]5007 in J3 filter and H in Hl filter in a RGB display. z ~ 1.5

Results pertaining to this cluster

1. First, clusters are found by slicing redshift catalog, then using nearest neighbor statistic of Papovich et al. (2010, ApJ, 716, 1503):

for each galaxy measure the angular distance to 7th nearest neighbor, then compute the corresponding surface density.

2. 7, 13, 9 galaxies within 30” of A, B, C in a 2.1 - 2.3 slice (313 total). Different statistical tests indicate that A & B are robust, C slightly less so. E.g., surface densities in adjacent slices are ~ 2.5 arcmin-2

More …

6. No new large mature cluster in CDF-S; expect 1±1 over the three fields (variance method of Somerville et al. 2004, ApJ 600, L171).

7. Other high-z clusters are either blue protoclusters, e.g., AzTEC-3, or the one mature one of Gobat et al. (2011, A&A, 526, 133), z ~ 2.07.

8. Finally, spectra of 4 galaxies confirm cluster at z = 2.09. (z due to filters)

Observations

Three fields: COSMOS, CDF-S, UDS.

(these have a large amount of ancillary data (deep optical, Spitzer) and more to come from Alma and Herschel).

COSMOS: 70 hours 56 t(eff) hours

CDF-S: 45 41

UDS: (50 hopefully)

FourStar vs ACS/HST(Core of A)

Model SEDs and Filters