Water, methanol and dense gas tracers in the local ULIRG Arp 220: Results from the new SEPIA Band 5 Science Verification campaign

Abstract

We present a line survey of the ultra-luminous infrared galaxy Arp 220, taken with the newly installed SEPIA Band 5 instrument on APEX. We illustrate the capacity of SEPIA to detect the 183.3 GHz H2O 31,3-22,0 line against the atmospheric H2O absorption feature. We confirm the previous detection of the HCN(2-1) line, and detect new transitions of standard dense gas tracers such as HNC(2-1), HCO+(2-1), CS(4-3), C34S(4-3), HC3N(20-19). We also detect HCN(2-1) v2=1 and the 193.5 GHz methanol (4-3) group for the first time. The absence of time variations in the megamaser water line compared to previous observations seems to rule out an AGN nuclear origin for the line. It could, on the contrary, favor a thermal origin instead, but also possibly be a sign that the megamaser emission is associated with star-forming cores washed-out in the beam. We finally discuss how the new transitions of HCN, HNC, HCO+ refine our knowledge of the ISM physical conditions in Arp 220.

5 pages, 2 figures, 1 table, accepted for publication in MNRAS

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Cited by in corpus (10)

• SEPIA - a new single pixel receiver at the APEX Telescope
• Detection of 183 GHz water megamaser emission towards NGC 4945
• Sub-arcsecond imaging of the water emission in Arp 220
• Dense-gas tracers and carbon isotopes in five 2.5<z<4 lensed dusty star forming galaxies from the SPT SMG sample
• PdBI U/LIRG Survey (PULS): Dense Molecular Gas in Arp 220 and NGC 6240
• Second Epoch ALMA Observations of 321 GHz Water Maser Emission in NGC 4945 and the Circinus Galaxy
• Dense Gas and Star Formation in Nearby Infrared Bright Galaxies: APEX survey of HCN and HCO+ J=2-1
• ALMA detection of millimetre 183 GHz H2O maser emission in the Superantennae galaxy at z ~ 0.06
• ALMA Sub-arcsec-resolution 183 GHz H2O and Dense Molecular Line Observations of Nearby Ultraluminous Infrared Galaxies
• Extragalactic maser surveys