Subarcsecond imaging of the water emission in Arp 220
Journal article, 2017
Aims. Extragalactic observations of water emission can provide valuable insight into the excitation of the interstellar medium. In particular they allow us to investigate the excitation mechanisms in obscured nuclei, that is, whether an active galactic nucleus or a starburst dominates.
Methods. We use subarcsecond resolution observations to tackle the nature of the water emission in Arp 220. ALMA Band 5 science verification observations of the 183 GHz H2O 313 − 220 line, in conjunction with new ALMA Band 7 H2O 515 − 422 data at 325 GHz, and supplementary 22 GHz H2O 616 − 523 VLA observations, are used to better constrain the parameter space in the excitation modeling of the water lines.
Results. We detect 183 GHz H2O and 325 GHz water emission toward the two compact nuclei at the center of Arp 220, being brighter in Arp 220 West. The emission at these two frequencies is compared to previous single-dish data and does not show evidence of variability. The 183 and 325 GHz lines show similar spectra and kinematics, but the 22 GHz profile is significantly different in both nuclei due to a blend with an NH3 absorption line.
Conclusions. Our findings suggest that the most likely scenario to cause the observed water emission in Arp 220 is a large number of independent masers originating from numerous star-forming regions.
galaxies: individual: Arp 220 / galaxies: ISM / galaxies: starburst / ISM: molecules
Author
Sabine König
Astronomy and Plasmaphysics
S. Martín
Atacama Large Millimeter-submillimeter Array (ALMA)
European Southern Observatory Santiago
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
Jose Cernicharo
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
K. Sakamoto
Academia Sinica
Laura Zschaechner
Max Planck Society
E. M. Humphreys
European Southern Observatory (ESO)
Tony Mroczkowski
European Southern Observatory (ESO)
Melanie Krips
Institut de Radioastronomie Millimétrique (IRAM)
Maud Galametz
The French Alternative Energies and Atomic Energy Commission (CEA)
European Southern Observatory (ESO)
Susanne Aalto
Astronomy and Plasmaphysics
Wouter Vlemmings
Astronomy and Plasmaphysics
Jürgen Ott
National Radio Astronomy Observatory Socorro
D. S. Meier
New Mexico Institute of Mining and Technology
A. Fuente
Spanish National Observatory (OAN)
S. G. Burillo
Spanish National Observatory (OAN)
Roberto Neri
Institut de Radioastronomie Millimétrique (IRAM)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 602 42- 30331Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1051/0004-6361/201630331