2018/04/01 by Mark Gorski, Jürgen Ott, Richard J. Rand +5 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble sequence #Luminous infrared galaxy #Maser #Metastability #Physics #Star formation #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aab3cc
published as The Astrophysical Journal, volume 856, number 2, 2018, page 134
openalex publication_date 2018/04/01 · arxiv created 2018/04/02 · arxiv updated 2018/04/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Abstract The Survey of Water and Ammonia in Nearby galaxies (SWAN) studies atomic and molecular species across the nuclei of four star-forming galaxies: NGC 253, IC 342, NGC 6946, and NGC 2146. As part of this survey, we present Karl G. Jansky Very Large Array molecular line observations of three galaxies: IC 342, NGC 6946, and NGC 2146. NGC 253 is covered in a previous paper. These galaxies were chosen to span an order of magnitude in star formation rates and to select a variety of galaxy types. We target the metastable transitions of ammonia NH 3 (1, 1) to (5, 5), the 22 GHz water (H 2 O) (6 16 –5 23 ) transition, and the 36.1 GHz methanol (CH 3 OH) (4 −1 –3 0 ) transition. We use the NH 3 metastable lines to perform thermometry of the dense molecular gas. We show evidence for uniform heating across the central kiloparsec of IC 342 with two temperature components for the molecular gas, similar to NGC 253, of 27 and 308 K, and that the dense molecular gas in NGC 2146 has a temperature <86 K. We identify two new water masers in IC 342, and one new water maser in each of NGC 6946 and NGC 2146. The two galaxies NGC 253 and NGC 2146, with the most vigorous star formation, host H 2 O kilomasers. Lastly, we detect the first 36 GHz CH 3 OH masers in IC 342 and NGC 6946. For the four external galaxies the total CH 3 OH luminosity in each galaxy suggests a correlation with galactic star formation rate, whereas the morphology of the emission is similar to that of HNCO, a weak shock tracer.