Astrophys. J., 720, L131-L136 (2010/September-2)
A massive molecular gas reservoir in the z = 5.3 submillimeter galaxy AzTEC-3.
RIECHERS D.A., CAPAK P.L., CARILLI C.L., COX P., NERI R., SCOVILLE N.Z., SCHINNERER E., BERTOLDI F. and YAN L.
Abstract (from CDS):
We report the detection of CO J = 2->1, 5->4, and 6->5 emission in the highest-redshift submillimeter galaxy (SMG) AzTEC-3 at z = 5.298, using the Expanded Very Large Array and the Plateau de Bure Interferometer. These observations ultimately confirm the redshift, making AzTEC-3 the most submillimeter-luminous galaxy in a massive z =~ 5.3 protocluster structure in the COSMOS field. The strength of the CO line emission reveals a large molecular gas reservoir with a mass of 5.3x1010(αCO/0.8) M☉, which can maintain the intense 1800 M☉/yr starburst in this system for at least 30 Myr, increasing the stellar mass by up to a factor of six in the process. This gas mass is comparable to "typical" z ∼ 2 SMGs and constitutes ≳80% of the baryonic mass (gas+stars) and 30%-80% of the total (dynamical) mass in this galaxy. The molecular gas reservoir has a radius of <4 kpc and likely consists of a "diffuse", low-excitation component, containing (at least) 1/3 of the gas mass (depending on the relative conversion factor αCO), and a "dense", high-excitation component, containing ∼2/3 of the mass. The likely presence of a substantial diffuse component besides highly excited gas suggests different properties between the star-forming environments in z > 4 SMGs and z > 4 quasar host galaxies, which perhaps trace different evolutionary stages. The discovery of a massive, metal-enriched gas reservoir in an SMG at the heart of a large z = 5.3 protocluster considerably enhances our understanding of early massive galaxy formation, pushing back to a cosmic epoch where the universe was less than 1/12 of its present age.
cosmology: observations - galaxies: active - galaxies: formation - galaxies: high-redshift - galaxies: starburst - radio lines: galaxies
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