SIMBAD references

Aims. We probe the physical conditions in the core of Arp 299A and try to put constraints on the nature of its nuclear power source.
Methods. We used Herschel Space Observatory far-infrared and submillimeter observations of H₂O and OH rotational lines in Arp 299A to create a multi-component model of the galaxy. In doing this, we employed a spherically symmetric radiative transfer code.
Results. Nine H₂O lines in absorption and eight in emission, as well as four OH doublets in absorption and one in emission, are detected in Arp 299A. No lines of the ¹⁸O isotopologues, which have been seen in compact obscured nuclei of other galaxies, are detected. The absorption in the ground state OH ²Π_3/2-²Π_3/2(5/2)⁺-(3/2)^– doublet at 119µm is found redshifted by ∼175kms compared with other OH and H₂O lines, suggesting a low excitation inflow. We find that at least two components are required in order to account for the excited molecular line spectrum. The inner component has a radius of 20-25pc, a very high infrared surface brightness (≥3x10¹³L_☉/kpc²), warm dust (T_d>90K), and a large H₂ column density (N_H2>10²⁴cm^–2). The modeling also indicates high nuclear H₂O (1-5x10^–6) and OH (0.5-5x10^–5) abundances relative to H nuclei. The outer component is larger (50-100pc) with slightly cooler dust (70-90K) and molecular abundances that are approximately one order of magnitude lower. In addition to the two components that account for the excited OH and H₂O lines, we require a much more extended inflowing component to account for the OH ²Π_3/2-²Π_3/2(5/2)⁺-(3/2)^– doublet at 119µm.
Conclusions. The Compton-thick nature of the core makes it difficult to determine the nature of the buried power source, but the high surface brightness indicates that it is an active galactic nucleus and/or a dense nuclear starburst. Our results are consistent with a composite source. The high OH/H₂O ratio in the nucleus indicates that ion-neutral chemistry induced by X-rays or cosmic-rays is important. Finally we find a lower limit to the ¹⁶O/¹⁸O ratio of 400 in the nuclear region, possibly indicating that the nuclear starburst is in an early evolutionary stage, or that it is fed through a molecular inflow of, at most, solar metallicity.