Submillimeter HCN and HCO(+) emission from galaxies

Abstract

view Abstract Citations (53) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Submillimeter HCN and HCO + Emission from Galaxies Jackson, James M. ; Paglione, Timothy A. D. ; Carlstrom, John E. ; Rieu, Nguyen-Q. Abstract We report the first detection of extragalactic HCN and HCO^+^ J = 4 - 3 emission at λ = 850 microns. Because their critical densities (n~10^7^ cm^-3^) and excitation energies (E_u_ ~ 45 K) are large, these lines trace dense, warm gas. We have detected HCN J = 4 - 3 toward NGC 253, NGC 4945, and IC 342 and report a sensitive upper limit toward M82. We have also detected HCO^+^ J = 4 - 3 in both NGC 253 and M82. The HCN J = 4 - 3/J = 1 - 0 intensity ratio, which is larger for higher gas densities, is at least 12 times larger in NGC 253 than that in M82. Single-component gas excitation model calculations for NGC 253 show that, averaged over the central 300 pc, the molecular gas is warm (T ~> 50 K) and dense (n ~ 5 x 10^5^ cm^-3^). For M82, the lower HCN J = 4 - 3/J = 1 - 0 line ratio requires an average gas density at least 10 times smaller. In both M82 and NGC 253, the J = 4 - 3/J = 1 - 0 line ratios peak at the nucleus. Consequently, molecular gas is densest in the central 300 pc. The submillimeter HCN and HCO^+^ lines reveal large differences in the dense gas properties, despite similar CO and far-infrared luminosities. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175113 Bibcode: 1995ApJ...438..695J Keywords: Interstellar Matter; Molecular Clouds; Molecular Gases; Star Formation; Starburst Galaxies; Carbon Monoxide; Gas Density; Molecular Excitation; Stellar Physics; Astrophysics; GALAXIES: ISM; ISM: MOLECULES; GALAXIES: INDIVIDUAL ALPHANUMERIC: IC 342; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 253; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4945 full text sources ADS | data products SIMBAD (6) NED (6)