Post on 18-Jan-2016
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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