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High Dense Gas Fraction in Intensely Star-forming Dusty Galaxies

Oteo, I; Zhang, ZY; Yang, C; Ivison, RJ; Omont, A; Bremer, M; Bussmann, S; ... Werf, PVD; + view all (2017) High Dense Gas Fraction in Intensely Star-forming Dusty Galaxies. Astrophysical Journal , 850 (2) , Article 170. 10.3847/1538-4357/aa8ee3. Green open access

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We present ALMA J = 3-2 and VLA J = 1-0 observations of the dense molecular gas tracers HCN, HCO+, and HNC in two lensed, high-redshift starbursts selected from the Herschel-ATLAS survey: H-ATLAS J090740.0-004200 (SDP.9, z spec = 1.575) and H-ATLAS J091043.1-000321 (SDP.11, z spec = 1.786). In SDP.9 we have detected all J = 3-2 transitions and also HCN(1-0) and HCO+(1-0). In SDP.11 we have detected HCN(3-2) and HCO+(3-2). The amplification factors for both galaxies have been determined from subarcsecond-resolution CO and dust emission observations carried out with NOEMA and the SMA. The HNC(1-0)/HCN(1-0) line ratio in SDP.9 suggests the presence of photon-dominated regions, as happens in most local (U)LIRGs. The CO, HCN, and HCO+ spectral line energy distribution (SLEDs) of SDP.9 are compatible to those found for many local, IR-bright galaxies, indicating that the molecular gas in local and high-redshift dusty starbursts can have similar excitation conditions. We obtain that the correlation between total IR (L IR ) and dense line (L dense ) luminosity in SDP.9 and SDP.11 and local star-forming galaxies can be represented by a single relation. We argue that the scatter of the L IR -L dense correlation, together with the lack of sensitive dense molecular gas tracer observations for a homogeneous sample of high-redshift galaxies, prevents us from distinguishing differential trends with redshift. Our results suggest that the intense star formation found in some high-redshift, dusty, luminous starbursts is associated with more massive dense molecular gas reservoirs and higher dense molecular gas fractions.

Type: Article
Title: High Dense Gas Fraction in Intensely Star-forming Dusty Galaxies
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4357/aa8ee3
Publisher version: https://doi.org/10.3847/1538-4357/aa8ee3
Language: English
Additional information: This is the published version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: galaxies: high-redshift; galaxies: ISM; galaxies: starburst; galaxies: star formation
URI: http://discovery.ucl.ac.uk/id/eprint/10041321
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