2017ApJ...836...20B -
Astrophys. J., 836, 20-20 (2017/February-2)
X-ray and ultraviolet properties of AGNs in nearby dwarf galaxies.
BALDASSARE V.F., REINES A.E., GALLO E. and GREENE J.E.
Abstract (from CDS):
We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies (z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad Hα emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad Hα and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L0.5–7keV ≃ 5 x 1039 to 1 x 1042 ergs–1. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ∼7 x 104 to 1 x 106 M☉), we find inferred Eddington fractions ranging from ∼0.1% to 50%, i.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e., αOX values an average of 0.36 lower than expected based on the relation between αOX and 2500 A luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.
Abstract Copyright:
© 2017. The American Astronomical Society. All rights reserved.
Journal keyword(s):
galaxies: active - galaxies: dwarf - quasars: supermassive black holes - ultraviolet: galaxies - X-rays: galaxies - X-rays: galaxies
Simbad objects:
13
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2017ApJ...836...20B and select 'bookmark this link' or equivalent in the popup menu