SIMBAD references

1999ApJ...519...89C - Astrophys. J., 519, 89-107 (1999/July-1)

The nature of accreting black holes in nearby galaxy nuclei.


Abstract (from CDS):

We have found compact X-ray sources in the center of 21 (54%) of 39 nearby face-on spiral and elliptical galaxies with available ROSAT HRI data. ROSAT X-ray luminosities (0.2-2.4 keV) of these compact X-ray sources are ∼1037-1040 ergs.s–1 (with a mean of 3x1039 ergs.s–1). The mean displacement between the location of the compact X-ray source and the optical photometric center of the galaxy is ∼390 pc. The fact that compact nuclear sources were found in nearly all (five of six) galaxies with previous evidence for a black hole or an active galactic nucleus (AGN) indicates that at least some of the X-ray sources are accreting supermassive black holes. ASCA spectra of six of the 21 galaxies show the presence of a hard component with relatively steep (Γ~2.5) spectral slope. A multicolor disk blackbody model fits the data from the spiral galaxies well, suggesting that the X-ray object in these galaxies may be similar to a black hole candidate in its soft (high) state. ASCA data from the elliptical galaxies indicate that hot (kT~0.7 keV) gas dominates the emission.

The fact that (for both spiral and elliptical galaxies) the spectral slope is steeper than in normal type 1 AGNs and that relatively low absorbing columns (NH~1021 cm–2) were found to the power-law component indicates that these objects are somehow geometrically and/or physically different from AGNs in normal active galaxies. The X-ray sources in the spiral and elliptical galaxies may be black hole X-ray binaries, low-luminosity AGNs, or possibly young X-ray luminous supernovae. Assuming the sources in the spiral galaxies are accreting black holes in their soft state, we estimate black hole masses ∼102-104 M.

Abstract Copyright:

Journal keyword(s): Galaxies: Active - X-Rays: Galaxies

Simbad objects: 52

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