Get access

The size of broad-line regions of low-luminosity active galactic nuclei

Authors

  • Xue-Guang Zhang,

    Corresponding author
    1. Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo Postal 70-264, México DF 04510, Mexico
    2. Centre for Astrophysics, Department of Astronomy and Applied Physics, University of Science and Technology of China, Hefei, Anhui, China
    Search for more papers by this author
  • Deborah Dultzin-Hacyan,

    1. Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo Postal 70-264, México DF 04510, Mexico
    Search for more papers by this author
  • Ting-Gui Wang

    1. Centre for Astrophysics, Department of Astronomy and Applied Physics, University of Science and Technology of China, Hefei, Anhui, China
    Search for more papers by this author

E-mail: xguang@astroscu.unam.mx

ABSTRACT

We study the size of broad-line regions (BLRs) of low-luminosity active galactic nuclei (AGN), also called ‘dwarf AGN’, defined as having L≤ 1041 erg s−1. We more than double the sample size analysed previously by Wang & Zhang. In this study we first confirm our previous result that the sizes of BLRs of low-luminosity AGN are larger than those expected from the empirical relation RBLRsL valid for ‘normal’ AGN (Seyfert 1s and quasars), except for objects with accretion rate inline image. Secondly, we find a positive correlation between the linewidth of the narrow emission lines (as a tracer of velocity dispersion and thus bulge and black hole mass) and the size of BLRs for both normal and low-luminosity AGN. In this paper we find a non-linear dependence of the BLR sizes of low-luminosity AGN on black hole masses. We also show that the sizes of BLRs are more strongly dominated by the ‘specific accretion rate’inline image, defined as inline image, than by the masses of their central black holes. An expected result of this is that the size of the emission regions of low-ionization broad Hα of NGC 4395 should be consistent with the value from the empirical relation of RBLRsL, according to the high accretion rate.

Ancillary