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Dense Gas and Star Formation in Nearby Infrared-bright Galaxies: APEX Survey of HCN and HCO+ J=2 -> 1

Zhou, Jing (författare)
Nanjing University
Zhang, Zhi-Yu (författare)
Nanjing University
Gao, Yu (författare)
Xiamen University,Chinese Academy of Sciences
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Wang, Junzhi (författare)
Guangxi University,Chinese Academy of Sciences
Shi, Yong (författare)
Nanjing University
Gu, Qiusheng (författare)
Nanjing University
Yang, Chentao, 1988 (författare)
Chalmers tekniska högskola,Chalmers University of Technology
Wang, Tao (författare)
Nanjing University
Tan, Qing-Hua (författare)
Chinese Academy of Sciences
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 (creator_code:org_t)
2022-08-30
2022
Engelska.
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 936:1
Relaterad länk:
https://research.cha... (primary) (free)
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https://doi.org/10.3...
https://research.cha...
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  • Tidskriftsartikel (refereegranskat)
Abstract Ämnesord
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  • Both Galactic and extragalactic studies of star formation suggest that stars form directly from dense molecular gas. To trace such high volume density gas, HCN and HCO+ J = 1 -> 0 have been widely used for their high dipole moments, relatively high abundances, and often being the strongest lines after CO. However, HCN and HCO+ J = 1 -> 0 emission could arguably be dominated by the gas components at low volume densities. The HCN J = 2 -> 1 and HCO+ J = 2 -> 1 transitions, with more suitable critical densities (1.6 x 10(6) and 2.8 x 10(5) cm(-3)) and excitation requirements, would trace typical dense gas closely related to star formation. Here we report new observations of HCN J = 2 -> 1 and HCO+ J = 2 -> 1 toward 17 nearby infrared-bright galaxies with the APEX 12 m telescope. The correlation slopes between the luminosities of HCN J = 2 -> 1 and HCO+ J = 2 -> 1 and total infrared emission are 1.03 +/- 0.05 and 1.00 +/- 0.05, respectively. The correlations of their surface densities, normalized with the area of radio/submillimeter continuum, show even tighter relations (slopes: 0.99 +/- 0.03 and 1.02 +/- 0.03). The eight active galactic nucleus (AGN)-dominated galaxies show no significant difference from the 11 star-formation-dominated galaxies in the above relations. The average HCN/HCO+ ratios are 1.15 +/- 0.26 and 0.98 +/- 0.42 for AGN- and star-formation-dominated galaxies, respectively, without obvious dependencies on infrared luminosity, dust temperature, or infrared pumping. The Magellanic Clouds roughly follow the same correlations, expanding to 8 orders of magnitude. On the other hand, ultraluminous infrared galaxies with AGNs systematically lie above the correlations, indicating potential biases introduced by AGNs.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
NATURVETENSKAP  -- Fysik -- Atom- och molekylfysik och optik (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Atom and Molecular Physics and Optics (hsv//eng)
NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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