Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418

Details Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418 Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418

2004-07-22

arxiv.org/abs/astro-ph/0407469v2

Astronomy and Astrophysics

Astrophysics

31 pages, 9 figures, Accepted for publication in Astronomical Journal (2004 November issue)

Scientific paper

10.1086/424620

We present near-infrared and millimeter investigations of the nucleus of the infrared luminous galaxy NGC 4418, which previous observations suggest possesses a powerful buried AGN. We found the following main results: (1) The infrared K-band spectrum shows CO absorption features at 2.3-2.4 micron owing to stars and very strong H2 emission lines. The luminosity ratios of H2 emission lines are suggestive of a thermal origin, and the equivalent width of the H2 1-0 S(1) line is the second largest observed to date in an external galaxy, after the well-studied strong H2-emitting galaxy NGC 6240. (2) The infrared L-band spectrum shows a clear polycyclic aromatic hydrocarbon (PAH) emission feature at 3.3 micron, which is usually found in star-forming galaxies. The estimated star-formation luminosity from the observed PAH emission can account for only a small fraction of the infrared luminosity. (3) Millimeter interferometric observations of the nucleus reveal a high HCN (1-0) to HCO+ (1-0) luminosity ratio of 1.8, as has been previously found in pure AGNs. (4) The measurements of HCN (1-0) luminosity using a single-dish millimeter telescope show that the HCN (1-0) to infrared luminosity ratio is slightly larger than the average, but within the scattered range, for other infrared luminous galaxies. All of these results can be explained by the scenario in which, in addition to energetically-insignificant, weakly-obscured star-formation at the surface of the nucleus, a powerful X-ray emitting AGN deeply buried in dust and high density molecular gas is present.

Affiliated with

Also associated with

No associations

Rating

Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Near-infrared and Millimeter Constraints on the Nuclear Energy Source of the Infrared Luminous Galaxy NGC 4418 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-277545