Possibility of Using 3.3 μm Polycyclic Aromatic Hydrocarbon Luminosity as a Molecular Gas Mass Estimator

초록

We present CO(1-0) observations of 50 star-forming galaxies at 0.01 < z < 0.35, for which 3.3 mu m polycyclic aromatic hydrocarbon (PAH) emission flux or its upper limit is available. A scaling relation between 3.3 mu m PAH luminosity and CO(1-0) luminosity is established covering similar to 2 orders of magnitude in total IR luminosity and CO luminosity, with a scatter of similar to 0.23 dex: logL(3.3)/L-circle dot = (1.00 +/- 0.07)xlog LCO(1-0)'/(Kkms(-1)pc(2)) +(-1.10 +/- 0.70). The slope is near unity, allowing the use of a single value of < log(L-3.3/L-CO(1-0)')> =-1.09 +/- 0.36 [L-circle dot/(K km s(-1) pc(2))] in the conversion between 3.3 mu m PAH and CO luminosities. The variation in the L-3.3/L-CO ' ratio is not dependent on the galaxy properties, including total IR luminosity, stellar mass, and star formation rate excess. The total gas mass, estimated using the dust-to-gas ratio and dust mass, is correlated with 3.3 mu m PAH luminosity, in line with the prescription using alpha(CO) = 0.8-4.5 covering both normal star-forming galaxies and starburst galaxies. Active galactic nucleus (AGN)-dominated galaxies tend to have a lower L-3.3/L-CO ' than non-AGN galaxies, which needs to be investigated further with an increased sample size. The established L-3.3-L-CO ' correlation is expected to be applicable to wide-field near-infrared spectrophotometric surveys that allow the detection of 3.3 mu m emission from numerous low-redshift galaxies.

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