High Resolution Observations of Molecular Lines in Arp 220: Kinematics, Morphology, and Limits on the Applicability of the Ammonia Thermometer

Abstract

We observe Arp 220, the nearest Ultra-Luminous Infrared Galaxy (ULIRG), over 4 GHz in the K and Ka bands. We provide constraints for the kinematics,morphology, and identify molecular species on scales resolving both nuclei (0.6" or 230 pc). We detect multiple molecular species, including hydroxyl in both cores. We tentatively detect H2O at 21.84 GHz in both nuclei, indicating the likely presence of maser emission. The observed frequency range also contains metastable ammonia transitions from (J,K) = (1,1) to (5,5), as well as the (9,9) inversion line, which, together are a well-known thermometer of dense molecular gas. Furthermore, the non-metastable (4,2) and (10,9) and possibly the (3,1) lines are also detected. We apply a standard temperature analysis to Arp 220. However, the analysis is complicated in that standard LTE assumptions do not hold. There are indications that a substantial fraction of ammonia could be in the non-metastable transitions as opposed to only the metastable ones. Thus, the non-metastable transitions could be essential to constraining the temperature. We compare all of these data to ALMA observations of this source, confirming the outflow previously observed by other tracers in both nuclei.

arXiv commentAccepted to ApJ, 10 pages, 6 figures

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Cited by in corpus (11)

• A Review of Recent Observations of Galactic Winds Driven by Star Formation
• The Survey of Water and Ammonia in the Galactic Center (SWAG): Molecular Cloud Evolution in the Central Molecular Zone
• Resolved Structure of Arp 220 Nuclei at λ~3 mm
• Comparing Models for IMF Variation Across Cosmological Time in Milky Way-like Galaxies
• Sub-arcsecond imaging of the water emission in Arp 220
• PdBI U/LIRG Survey (PULS): Dense Molecular Gas in Arp 220 and NGC 6240
• The galaxy-wide stellar initial mass function in the presence of cluster-to-cluster IMF variations
• JWST/NIRSpec insights into the circumnuclear region of Arp 220: A detailed kinematic study
• Discovery of Methanimine Megamasers Toward Compact Obscured Galaxy Nuclei
• A Spectral Analysis of the Centimeter Regime of Nearby Galaxies: RRLs, Excited OH, and NH${}_3$
• Extragalactic maser surveys