Astrophys. J., 527, 778-794 (1999/December-3)
Near-infrared line observations of Arp 299 as a tracer of activity in the nuclei.
SUGAI H., DAVIES R.I., MALKAN M.A., McLEAN I.S., USUDA T. and WARD M.J.
Abstract (from CDS):
We have obtained images of the molecular hydrogen (H2) and Brγ emission lines in the interacting galaxy system Arp 299. In order to investigate the nuclear activities, we also have obtained H- and K-band spectra for three of its 2 µm continuum peaks and also J-band spectra for one of them. From the line ratios of Paγ, Paβ, Br10, and Brγ, and also those between [Fe II] 1.26 µm and [Fe II] 1.64 µm, we have successfully modeled the extinction for component A as a combination of AK=2.6 mag region(s) and AK=0.3 mag region(s). The extinction corrected Brγ luminosity requires 5x1054 s–1 of Lyman photons, which corresponds to 3x105 ``O6 stars.'' The mean stellar density within its 100 pc core is comparable to those for the cores in blue compact dwarf galaxies even though the luminosity is almost 2 orders of magnitude larger. The starbursts at the nucleus of component A are probably the most dominant source for the far-infrared emission from this component. In this component, we have found large [Fe II]/H I ratios, which are at the higher end of starburst galaxies and are typical for AGNs or AGN/starburst composites. The nucleus must be in a starburst phase that includes many supernova remnants. The spatial distribution of the H2 emission for this interacting system is similar to that of the 12CO 1-0 emission mapped by Aalto et al. The H2 intensity, however, is not proportional to the CO intensity among components, because of the difference in the H2 excitation mechanism among them. We report the first possible detection of J-band H2 lines in infrared luminous galaxies in component A, which suggests a significant contribution of nonthermal excitation mechanisms.
ISM: Dust, Extinction - galaxies: individual (Arp 299) - Galaxies: Interactions - Galaxies: Nuclei - Infrared: Galaxies - Line: Formation
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