Detection of the 13CO(J=6-5) Transition in the Starburst Galaxy NGC 253

• Published in: arXiv.org
• Main Authors: Hailey-Dunsheath, S, Nikola, T, Stacey, G J, Oberst, T E, Parshley, S C, Bradford, C M, Ade, P A R, Tucker, C E
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 24.10.2008
• Subjects: Cosmic rays; Galaxies; Heat sources; Molecular gases; Photons; Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics; Red shift; Starburst galaxies; Starbursts; Turbulence; Universe
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0810.4514

We report the detection of 13CO(J=6-5) emission from the nucleus of the starburst galaxy NGC 253 with the redshift (z) and Early Universe Spectrometer (ZEUS), a new submillimeter grating spectrometer. This is the first extragalactic detection of the 13CO(J=6-5) transition, which traces warm, dense molecular gas. We employ a multi-line LVG analysis and find ~ 35% - 60% of the molecular ISM is both warm (T ~ 110 K) and dense (n(H2) ~ 10^4 cm^-3). We analyze the potential heat sources, and conclude that UV and X-ray photons are unlikely to be energetically important. Instead, the molecular gas is most likely heated by an elevated density of cosmic rays or by the decay of supersonic turbulence through shocks. If the cosmic rays and turbulence are created by stellar feedback within the starburst, then our analysis suggests the starburst may be self-limiting.