Open AccessInvestigating the central engine and excitation mechanisms of ultraluminous infrared galaxies: near‐infrared spectroscopy
Author(s) -
Burston A.J.,
Ward M.J.,
Davies R.I.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04623.x
Subject(s) - physics , astrophysics , infrared , galaxy , luminous infrared galaxy , line (geometry) , emission spectrum , thermal emission , hydrogen molecule , spectroscopy , excitation , astronomy , spectral line , hydrogen , thermal , geometry , mathematics , quantum mechanics , meteorology
We present near‐infrared observations of a sample of mainly interacting ultraluminous infrared galaxies, comprising H ‐ and K ‐band spectra. Our main aims are to investigate the power source of these extremely luminous objects and the various excitation mechanisms of the strong molecular hydrogen emission often seen in such objects. Broadened emission lines were only detected in one object, IRAS 23498, consistent with the previous results for this galaxy. The [Si vi ] emission line was detected in IRAS 17179 and 20210, both classified as Sy2s. Two of the samples were unclassified, IRAS 00150 and 23420, which exhibit neither [Si vi ] emission nor broadened H i emission. However this does not rule out the presence of an obscured AGN. Analysis of the molecular hydrogen emission showed that the major excitation mechanism for most objects was thermal. Modelling of the more luminous objects indicates that for IRAS 20210 10 per cent, and for both IRAS 23365 and IRAS 23420 30 per cent, of the 1–0 S(1) line emission has a non‐thermal origin.