A Comparative Analysis of Virial Black Hole Mass Estimates of Moderate-luminosity Active Galactic Nuclei Using Subaru/FMOS

July 2013 • 2013ApJ...771...64M

Authors • Matsuoka, K. • Silverman, J. D. • Schramm, M. • Steinhardt, C. L. • Nagao, T. • Kartaltepe, J. • Sanders, D. B. • Treister, E. • Hasinger, G. • Akiyama, M. • Ohta, K. • Ueda, Y. • Bongiorno, A. • Brandt, W. N. • Brusa, M. • Capak, P. • Civano, F. • Comastri, A. • Elvis, M. • Lilly, S. J. • Mainieri, V. • Masters, D. • Mignoli, M. • Salvato, M. • Trump, J. R. • Taniguchi, Y. • Zamorani, G. • Alexander, D. M. • Schawinski, K.

Abstract • We present an analysis of broad emission lines observed in moderate-luminosity active galactic nuclei (AGNs), typical of those found in X-ray surveys of deep fields, with the goal of testing the validity of single-epoch virial black hole mass estimates. We have acquired near-infrared spectra of AGNs up to z ~ 1.8 in the COSMOS and Extended Chandra Deep Field-South Survey, with the Fiber Multi-Object Spectrograph mounted on the Subaru telescope. These near-infrared spectra provide a significant detection of the broad Hα line, shown to be a reliable probe of black hole mass at low redshift. Our sample has existing optical spectroscopy that provides a detection of Mg II, typically used for black hole mass estimation at z >~ 1. We carry out a spectral-line fitting procedure using both Hα and Mg II to determine the virial velocity of gas in the broad-line region, the continuum luminosity at 3000 Å, and the total Hα line luminosity. With a sample of 43 AGNs spanning a range of two decades in luminosity, we find a tight correlation between the ultraviolet and emission-line luminosity. There is also a close one-to-one relationship between the full width at half-maximum of Hα and Mg II. Both of these then lead to there being very good agreement between Hα- and Mg II-based masses over a wide range in black hole mass, i.e., M BH ~ 107-9 M . In general, these results demonstrate that local scaling relations, using Mg II or Hα, are applicable for AGNs at moderate luminosities and up to z ~ 2.


IPAC Authors


Elise Furlan

Associate Scientist

Daniel Masters

Assistant Scientist