First Results from the 3D-HST Survey: The Striking Diversity of Massive Galaxies at z > 1

We present first results from the 3D-HST program, a near-IR spectroscopic survey performed with the Wide Field Camera 3 (WFC3) on the HST. We have used 3D-HST spectra to measure redshifts and H Delta *a equivalent widths (EWH Delta *a) for a complete, stellar mass-limited sample of 34 galaxies at 1...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2011-12, Vol.743 (1), p.L15-jQuery1323914556192='48'
Main Authors: van Dokkum, Pieter G, Brammer, Gabriel, Fumagalli, Mattia, Nelson, Erica, Franx, Marijn, Rix, Hans-Walter, Kriek, Mariska, Skelton, Rosalind E, Patel, Shannon, Schmidt, Kasper B, Bezanson, Rachel, Bian, Fuyan, da Cunha, Elisabete, Erb, Dawn K, Fan, Xiaohui, Förster Schreiber, Natascha, Illingworth, Garth D, Labbé, Ivo, Lundgren, Britt, Magee, Dan, Marchesini, Danilo, McCarthy, Patrick, Muzzin, Adam, Quadri, Ryan, Steidel, Charles C, Tal, Tomer, Wake, David, Whitaker, Katherine E, Williams, Anna
Format: Article
Language:English
Subjects:
ABSORPTION
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CAMERAS
COSMOLOGY
EMISSION SPECTROSCOPY
GALAXIES
INDEXES
INFRARED SPECTRA
MASS
NEAR INFRARED RADIATION
RED SHIFT
STARS
UNIVERSE
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Summary:We present first results from the 3D-HST program, a near-IR spectroscopic survey performed with the Wide Field Camera 3 (WFC3) on the HST. We have used 3D-HST spectra to measure redshifts and H Delta *a equivalent widths (EWH Delta *a) for a complete, stellar mass-limited sample of 34 galaxies at 1 < z < 1.5 with M star > 1011 M in the COSMOS, GOODS, and AEGIS fields. We find that a substantial fraction of massive galaxies at this epoch are forming stars at a high rate: the fraction of galaxies with EWH Delta *a >10 A is 59%, compared to 10% among Sloan Digital Sky Survey galaxies of similar masses at z = 0.1. Galaxies with weak H Delta *a emission show absorption lines typical of 2-4 Gyr old stellar populations. The structural parameters of the galaxies, derived from the associated WFC3 F140W imaging data, correlate with the presence of H Delta *a; quiescent galaxies are compact with high Sersic index and high inferred velocity dispersion, whereas star-forming galaxies are typically large two-armed spiral galaxies, with low Sersic index. Some of these star-forming galaxies might be progenitors of the most massive S0 and Sa galaxies. Our results challenge the idea that galaxies at fixed mass form a homogeneous population with small scatter in their properties. Instead, we find that massive galaxies form a highly diverse population at z > 1, in marked contrast to the local universe.
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/743/1/L15