VERY LARGE ARRAY MAPPING OF THE CO(1-0) LINE IN SMM J14011+0252

Journal Article · Fri Mar 01 04:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/765/1/6· OSTI ID:22167671

Sharon, Chelsea E.; Baker, Andrew J. ^[1]; Harris, Andrew I. ^[2]

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1. Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8019 (United States)
2. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

We present high-resolution CO(1-0) observations of the lensed submillimeter galaxy (SMG) SMM J14011+0252 at z = 2.6. Comparison to the previously detected CO(3-2) line gives an intensity ratio of r {sub 3,1} = 0.97 {+-} 0.16 in temperature units, larger than is typical for SMGs but within the range seen in the low-z ultraluminous infrared galaxy population. Combining our new data with previous mid-J CO observations, we perform a single-phase large velocity gradient (LVG) analysis to constrain the physical conditions of the molecular gas. Acceptable models have significant degeneracies between parameters, even when we rule out all models that produce optically thin emission, but we find that the bulk of the molecular gas has T {sub kin} = 20-60 K, n{sub H{sub 2}}{approx}10{sup 4}-10{sup 5} cm{sup -3}, and N {sub CO}/{Delta}v = 10{sup 17.00{+-}0.25} cm{sup -2} km{sup -1} s. For our best-fit models to self-consistently recover a typical CO-to-H{sub 2} abundance and a plausible degree of virialization, the local velocity gradient in the molecular gas must be substantially larger than its galaxy-wide average. This conclusion is consistent with a scenario in which SMM J14011+0252 has a fairly face-on orientation and a molecular interstellar medium composed of many unresolved clouds. Using previous H{alpha} observations, we find that SMM J14011+0252 has a spatially resolved star formation rate versus molecular gas surface density relation inconsistent with those of 'normal' local star-forming galaxies, even if we adopt a local 'disk-like' CO-to-H{sub 2} conversion factor as motivated by our LVG analysis. This discrepancy supports the inference of a star formation relation for high-z starbursts distinct from the local relation that is not solely due to differing choices of gas mass conversion factor.

• OSTI ID: 22167671
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 765; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
CARBON MONOXIDE
COMPARATIVE EVALUATIONS
CONVERSION
ELEMENT ABUNDANCE
GALAXIES
GRAVITATIONAL LENSES
HYDROGEN
MAPPING
MOLECULES
ORIENTATION
PHOTON EMISSION
RED SHIFT
STARS