Infrared 2-4 Micrometer Spectroscopy and Millimeter Interferometric HCN and HCO+ Observations of the Individual Merging Components of Arp 299
Abstract
We present ground-based infrared K-(2-2.5μm) and L-band (2.8-4.1μm) spectroscopy, as well as interferometric observations at λ∼3mm, for the individual merging components (A, B, and C) of the luminous infrared galaxy Arp 299. The presence and location of a buried active galactic nucleus (AGN) are investigated. Our sub-arcsec-resolution infrared spectra clearly reveal that the putative buried AGN resides in the nucleus B1 (a subcomponent of B), based on a very low equivalent width of 3.3μm polycyclic aromatic hydrocarbon emission, a weak 2.3μm CO absorption feature, and a large time variation of the K- and L-band continuum fluxes. Our interferometric observations simultaneously obtain HCN (J = 1-0) and HCO+ (J = 1-0) emission lines with ∼ 4'' resolution, and we find the HCN to HCO+ brightness-temperature ratios to be as low as those found in starburst nuclei in all of the major merging components of Arp 299. The low ratio even in the AGN-hosting nucleus B may be due to the presence of a large amount of high-density molecular gas whose chemistry is dominated by coexisting starbursts and/or shocks, rather than by the central strong X-ray-emitting AGN.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- October 2006
- DOI:
- 10.1093/pasj/58.5.813
- arXiv:
- arXiv:astro-ph/0608309
- Bibcode:
- 2006PASJ...58..813I
- Keywords:
-
- galaxies: active;
- galaxies: individual (Arp 299);
- galaxies: ISM;
- galaxies: nuclei;
- infrared: galaxies;
- radio lines: galaxies;
- Astrophysics
- E-Print:
- 20 pages, 8 figures, Accepted for publication in PASJ (Vol. 58, No. 5, 2006 Oct 25 issue)