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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 731452.0, MPI für Astronomie / Publikationen_mpia
High-resolution observations of molecular lines in Arp 220: Kinematics, morphology, and limits on the applicability of the ammonia thermometer
Authors:Zschaechner, L. K.; Ott, J.; Walter, F.; Meier, D. S.; Momjian, E.; Scoville, N.
Date of Publication (YYYY-MM-DD):2016
Title of Journal:The Astrophysical Journal
Issue / Number:1
Start Page:id. 41 (10 pp)
Audience:Not Specified
Abstract / Description:We observe Arp 220, the nearest ultra-luminous infrared galaxy, over 4 GHz in the K and Ka bands, providing constraints for the kinematics and morphology, and identifying molecular species on scales resolving both nuclei (0.″6 or 230 pc). We detect multiple molecular species, including hydroxyl (OH {}2{{{\Pi }}}3/2J=9/2F=4-4;5-5) in both cores, and tentatively detect H2O(615-523) 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)–(5, 5), as well as the (9, 9) inversion line; together, they 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 local thermal equilibrium (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.
Free Keywords:astrochemistry; galaxies: evolution; galaxies: individual: Arp 220; galaxies: ISM; galaxies: nuclei; galaxies: starburst
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.3847/1538-4357/833/1/41
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