Dense circum-nuclear molecular gas in starburst galaxies

Abstract

We present results from a study of the dense circum-nuclear molecular gas of starburst galaxies. The study aims to investigate the interplay between starbursts, active galactic nuclei and molecular gas. We characterise the dense gas traced by HCN, HCO${}^{+}$ and HNC and examine its kinematics in the circum-nuclear regions of nine starburst galaxies observed with the Australia Telescope Compact Array. We detect HCN (1$-$0) and HCO${}^{+}$ (1$-$0) in seven of the nine galaxies and HNC (1$-$0) in four. Approximately 7 arcsec resolution maps of the circum-nuclear molecular gas are presented. The velocity integrated intensity ratios, HCO${}^{+}$ (1$-$0)/HCN (1$-$0) and HNC (1$-$0)/HCN (1$-$0), are calculated. Using these integrated intensity ratios and spatial intensity ratio maps we identify photon dominated regions (PDRs) in NGC 1097, NGC 1365 and NGC 1808. We find no galaxy which shows the PDR signature in only one part of the observed nuclear region. We also observe unusually strong HNC emission in NGC 5236, but it is not strong enough to be consistent with X-ray dominated region (XDR) chemistry. Rotation curves are derived for five of the galaxies and dynamical mass estimates of the inner regions of three of the galaxies are made.

Accepted for publication in MNRAS, 22 December 2015. Main manuscript is 13 pages, containing 3 figures. Also has 4 appendices of 13 pages total containing numerous figures and details of calculations

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Cited by in corpus (9)

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• Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253
• Molecular line emission in NGC 4945, imaged with ALMA
• Molecular transitions as probes of the physical conditions of extragalactic environments
• Dense molecular gas in the starburst nucleus of NGC 1808
• Central molecular zones in galaxies: multitransition survey of dense gas tracers HCN, HNC, and HCO+
• History-independent tracers: Forgetful molecular probes of the physical conditions of the dense interstellar medium
• Tracing circumnuclear dense gas in H2O maser galaxies