Poster Presentation
A UNIFORMLY SELECTED SAMPLE OF LOW-MASS BLACK HOLES IN SEYFERT 1 GALAXIES
Presenter: Heyang Liu (NAOC)
Here we present a new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) with black hole masses in the range of (1 − 20) × 105 M⊙. The AGNs are selected from a systematic search among galaxies in the Data Release (DR) 7 of the Sloan Digital Sky Survey (SDSS), by careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from the SDSS DR 4 (Dong et al. 2012) makes it the largest LMBH sample so far, totaling over 500 objects. We briefly discussed some of the statistical properties of the combined LMBH AGN sample, in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [O III] luminosity. The effective optical-to-X-ray spectral indices α_ox, albeit a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L2500Å. Interestingly, a correlation of α_ox with black hole mass is also found in the sense that α_ox is statistically flatter (stronger X-ray relative to optical) for lower black hole mass. Only 26 objects, mostly radio loud, were detected in radio at 20 cm in the FIRST survey, making a radio loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 10^(8.8−12.4) M⊙ and optical colors typical of Sbc spirals. They are dominated by young stellar populations which seem to have undergone a continuous star formation history.
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