Investigating AGN black hole masses and the MBH-σe relation for low surface brightness galaxies

Abstract

We present an analysis of the optical nuclear spectra from the active galactic nuclei (AGN) in a sample of low surface brightness (LSB) galaxies. Using data from the Sloan Digital Sky Survey (SDSS), we derived the virial black hole (BH) masses of 24 galaxies from their broad H α parameters. We find that our estimates of nuclear BH masses lie in the range 10 5 – 10 7 M

, with a median mass of 5.62 × 10 6 M

. The bulge stellar velocity dispersion σ e was determined from the underlying stellar spectra. We compared our results with the existing BH mass–velocity dispersion ( M BH – σ e ) correlations and found that the majority of our sample lie in the low BH mass regime and below the M BH – σ e correlation. We analysed the effects of any systematic bias in the M BH estimates, the effects of galaxy orientation in the measurement of σ e and the increase of σ e due to the presence of bars and found that these effects are insufficient to explain the observed offset in M BH – σ e correlation. Thus, the LSB galaxies tend to have low-mass BHs which probably are not in co-evolution with the host galaxy bulges. A detailed study of the nature of the bulges and the role of dark matter in the growth of the BHs is needed to further understand the BH-bulge co-evolution in these poorly evolved and dark matter dominated systems.