2011MNRAS.418.1753J -
Mon. Not. R. Astron. Soc., 418, 1753-1763 (2011/December-2)
Dense molecular gas in nearby gas-rich active galaxies.
JIANG X., WANG J. and GU Q.
Abstract (from CDS):
We present 3-mm observations obtained with the Institut de Radioastronomie Millimétrique (IRAM) 30-m telescope for 10 nearby gas-rich active galaxies spanning three orders of magnitude in infrared luminosity. Emission lines of HCO
+(1–0), HCN(1–0) and C
2H(1–0) were simultaneously detected in most galaxies of our sample. We also tentatively detected the rare isotopic species H
13CN, HC
15N and H
13CO
+ in up to four galaxies (IC 694, NGC 3690, NGC 4258 and NGC 6240). Our estimation shows that the optical depth of HCN is low to moderate in these galaxies (τ ∼ 1–5). After comparing the intensity ratios of different molecular emission lines (HCN/HCO
+, C
2H/HCN and C
2H/HCO
+) with the infrared luminosity (
LIR), we find that in the infrared luminous sample of five composite (AGN+starburst) galaxies these ratios vary with
LIR: the HCN/HCO
+ ratio increases with
LIR, which is consistent with previous studies, while there is a slight trend in the composite galaxies that both C
2H/HCN and C
2H/HCO
+ ratios decrease with increasing
LIR. Although our sample is limited, this trend may possibly imply a relation between the overall gas density and the infrared luminosity of galaxies.
Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
Abstract Copyright:
2011 The Authors Monthly Notices of the Royal Astronomical Society2011 RAS
Journal keyword(s):
ISM: molecules - galaxies: active - galaxies: evolution - galaxies: ISM
Simbad objects:
20
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