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arXiv · 1402.1039

Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J=4-3, HCO+ J=4-3, and CS J=7-6

Zhi-Yu Zhang·Yu Gao·Christian Henkel·Yinghe Zhao·Junzhi Wang·Karl M. Menten·Rolf Guesten
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Abstract

We report HCN J=4-3, HCO+ J=4-3, and CS J=7-6 observations in 20 nearby star-forming galaxies with the Acatama Pathfinder EXperiment 12-m telescope. Combined with 4 HCN, 3 HCO+, and 4 CS detections in literature, we probe the empirical link between the luminosity of molecular gas (L_gas) and that of infrared emission (L_IR), up to the highest gas densities (10^6 - 10^8 cm-3) that have been probed so far. For nearby galaxies with large radii, we measure the IR luminosity within the submm beam-size (14"-18") to match the molecular emission. We find linear slopes for L_CS76-L_IR and L_HCN43-L_IR, and a slightly super-linear slope for L_HCO+43-L_IR. The correlation of L_CS76-L_IR even extends over eight orders of luminosity magnitude down to Galactic dense cores, with a fit of log(L_IR)=1.00(\pm 0.01) \times log(L_CS76) + 4.03(\pm 0.04). Such linear correlations appear to hold for all densities >10^4 cm-3, and indicate that star formation rate is not related to free-fall time scale for dense molecular gas.

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Zhi-Yu Zhang, Yu Gao, Christian Henkel, Yinghe Zhao, Junzhi Wang, Karl M. Menten, Rolf Guesten. 2014-02-05. Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J=4-3, HCO+ J=4-3, and CS J=7-6. https://doi.org/10.1088/2041-8205%2F784%2F2%2Fl31

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