Astrophys. J., 739, L33 (2011/September-3)
Expanded very large array observations of a proto-cluster of molecular gas-rich galaxies at z = 4.05.
CARILLI C.L., HODGE J., WALTER F., RIECHERS D., DADDI E., DANNERBAUER H. and MORRISON G.E.
Abstract (from CDS):
We present observations of the molecular gas in the GN20 proto-cluster of galaxies at z = 4.05 using the Expanded Very Large Array (EVLA). This group of galaxies is the ideal laboratory for studying the formation of massive galaxies via luminous, gas-rich starbursts within 1.6 Gyr of the big bang. We detect three galaxies in the proto-cluster in CO 2-1 emission, with gas masses (H2) between 1010 and 1011x(α/0.8) M☉. The emission from the brightest source, GN20, is resolved with a size ∼2'' and has a clear north-south velocity gradient, possibly indicating ordered rotation. The gas mass in GN20 is comparable to the stellar mass (1.3x1011x(α/0.8) M☉ and 2.3x1011 M☉, respectively), and the sum of gas plus stellar mass is comparable to the dynamical mass of the system (∼3.4x1011[sin (i)/sin (45°)]–2 M☉), within a 5 kpc radius. There is also evidence for a tidal tail extending another 2'' north of the galaxy with a narrow velocity dispersion. GN20 may be a massive, gas-rich disk that is gravitationally disturbed, but not completely disrupted. There is one Lyman-break galaxy (BD29079) in the GN20 proto-cluster with an optical spectroscopic redshift within our search volume, and we set a 3σ limit to the molecular gas mass of this galaxy of 1.1x1010x(α/0.8) M☉.
galaxies: evolution - galaxies: ISM - galaxies: starburst - submillimeter: galaxies
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