# EVLA observations of a proto-cluster of molecular gas rich galaxies at z = 4.05

Abstract : 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 (H$_2$) between $10^{10}$ and $10^{11} \times (\alpha/0.8)$ M$_\odot$. The emission from the brightest source, GN20, is resolved with a size $\sim 2"$, and has a clear north-south velocity gradient, possibly indicating ordered rotation. The gas mass in GN20 is comparable to the stellar mass ($1.3\times 10^{11} \times (\alpha/0.8)$ M$_\odot$ and $2.3\times 10^{11}$ M$_\odot$, respectively), and the sum of gas plus stellar mass is comparable to the dynamical mass of the system ($\sim 3.4\times 10^{11} [sin(i)/sin(45^o)]^{-2}$ M$_\odot$), within a 5kpc 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 3$\sigma$ limit to the molecular gas mass of this galaxy of $1.1\times 10^{10} \times (\alpha/0.8)$ M$_\odot$.
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https://hal-cea.archives-ouvertes.fr/cea-01001848
Contributor : Bruno Savelli <>
Submitted on : Thursday, June 5, 2014 - 10:09:16 AM
Last modification on : Thursday, August 1, 2019 - 10:42:20 AM

### Citation

C. L. Carilli, J. Hodge, F. Walter, D. Riechers, E. Daddi, et al.. EVLA observations of a proto-cluster of molecular gas rich galaxies at z = 4.05. Astrophysical Journal Letters, 2011, 739, pp.L33. ⟨10.1088/2041-8205/739/1/L33⟩. ⟨cea-01001848⟩

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