A DEEP CHANDRA VIEW OF THE NGC 404 CENTRAL ENGINE
- Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
- Department of Astronomy and Astrophysics and Center for Gravitational Wave Physics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138 (United States)
- Astronomy Department, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States)
We present the results of a 100 ks Chandra observation of the NGC 404 nuclear region. The long exposure and excellent spatial resolution of Chandra have enabled us to critically examine the nuclear environment of NGC 404, which is known to host a nuclear star cluster and potentially an intermediate-mass black hole (IMBH; on the order of a few times 10{sup 5} M{sub sun}). We find two distinct X-ray sources: a hard, central point source coincident with the optical and radio centers of the galaxy, and a soft extended region that is coincident with areas of high H{alpha} emission and likely recent star formation. When we fit the 0.3-8 keV spectra of each region separately, we find the hard nuclear point source to be dominated by a power law ({Gamma} = 1.88), while the soft off-nuclear region is best fit by a thermal plasma model (kT = 0.67 keV). We therefore find evidence for both a power-law component and hot gas in the nuclear region of NGC 404. We estimate the 2-10 keV luminosity to be 1.3{sup +0.8}{sub -0.5} x 10{sup 37} erg s{sup -1}. A low level of diffuse X-ray emission was detected out to {approx}15'' ({approx}0.2 kpc) from the nucleus. We compare our results to the observed relationships between power-law photon index and Eddington ratio for both X-ray binaries and low-luminosity active galaxies and find NGC 404 to be consistent with other low-luminosity active galaxies. We therefore favor the conclusion that NGC 404 harbors an IMBH accreting at a very low level.
- OSTI ID:
- 21579920
- Journal Information:
- Astrophysical Journal, Vol. 737, Issue 2; Other Information: DOI: 10.1088/0004-637X/737/2/77; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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