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Published September 10, 2010 | Accepted Version + Published
Journal Article Open

A Massive Molecular Gas Reservoir in the z = 5.3 Submillimeter Galaxy AzTEC-3


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 5.3 × 10^(10)(α_(CO)/0.8) M_☉ sun, which can maintain the intense 1800 M_☉ sun yr^(–1) 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.

Additional Information

© 2010 American Astronomical Society. Received 2010 June 28; accepted 2010 July 30; published 2010 August 16. We thank Josh Younger for the SMA image of AzTEC-3, Christian Henkel for the original version of the LVG code, and the referee for a helpful report. D.R. acknowledges support from NASA through Hubble Fellowship grant HST-HF-51235.01 awarded by STScI, operated by AURA for NASA, under contract NAS 5-26555. The IRAM PdBI is supported by INSU/CNRS (France),MPG (Germany), and IGN (Spain). The EVLA is a facility of NRAO, operated by AUI, under a cooperative agreement with the NSF.

Attached Files

Published - Riechers2010p11446Astrophys_J_Lett.pdf

Accepted Version - 1008.0389.pdf


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August 22, 2023
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