Determining Stellar Velocity Dispersion in Active Galaxies: Is the [OIII] Width a Valid Surrogate?

ORAL

Abstract

The tight empirical relation between the stellar velocity dispersion ($\sigma$) of the bulge and the mass of the supermassive black hole (BH) at its center indicates a close connection between galactic evolution and BH growth. The evolution of this relation with cosmic time provides valuable clues to its origin. While the mass of the BH can be easily estimated using the Doppler broadening of the H$\beta$ emission line in type-1 active galactic nuclei (AGNs), measuring $\sigma$ simultaneously is challenging, since the nuclear emission outshines the host galaxy. Thus, it is highly desirable to find an alternative way to estimate $\sigma$. In the literature, the width of the [OIII] emission line has been used as a surrogate, assuming that the narrow-line region follows the gravitational potential of the bulge. While the [OIII] line has the great advantage of being easily measurable in AGNs out to large redshifts, it is also known to be affected by outflows and jets. For a sample of about 100 nearby active galaxies, we determine the width of the [OIII] line using two Gaussians to exclude any outflowing component. The resulting width is compared to $\sigma$ measurements previously compiled from Keck spectroscopy for the entire sample to determine the method's viability.

–

Authors

  • Kelsi Flatland

    Cal Poly San Luis Obispo

  • Vardha N. Bennert

    Cal Poly San Luis Obispo

  • Nilgun Sungar

    Department of Physics and Astronomy, University of California, Irvine, University of California, Irvine, California State University, Fresno, Physics Department, University of California, Santa Cruz, CA, 95064, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, Seogang University, Pohang University of Science \& Technology, UC Santa Cruz, Trinity College, Hartford, Los Alamos National Laboratory, University of Connecticut, Storrs, CSU Long Beach, Physics/Hokkaido University, Japan, Physics/University of California, San Deigo, Physics/California State University, Fresno, CSU Stanislaus, University of California, Santa Barbara, Instituted of Astronomy, University of Cambridge, UK, Max-Planck Institute for Radio Astronomy, Bonn, Germany, Institute of Astronomy, University of Cambridge, UK, California Polytechnic State University, San Luis Obispo, SpaceX, Northrop-Grumman, Cal Poly San Luis Obispo, Department of Physics, University of California at Davis, Davis 95616, United States Department of Agriculture-Agriculture Research Service, Chemistry/California State University Fresno, Physics/California State University Fresno, University of California Santa Barbara, University of California Merced, UC Merced, Stanford University, New Economic School, California Polytechnic State University San Luis Obispo, Indiana University - Purdue University Indianapolis, California Polytechnic State University, San Luis Obispo, Chair of the Physics Department

  • Nilgun Sungar

    Department of Physics and Astronomy, University of California, Irvine, University of California, Irvine, California State University, Fresno, Physics Department, University of California, Santa Cruz, CA, 95064, Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, Seogang University, Pohang University of Science \& Technology, UC Santa Cruz, Trinity College, Hartford, Los Alamos National Laboratory, University of Connecticut, Storrs, CSU Long Beach, Physics/Hokkaido University, Japan, Physics/University of California, San Deigo, Physics/California State University, Fresno, CSU Stanislaus, University of California, Santa Barbara, Instituted of Astronomy, University of Cambridge, UK, Max-Planck Institute for Radio Astronomy, Bonn, Germany, Institute of Astronomy, University of Cambridge, UK, California Polytechnic State University, San Luis Obispo, SpaceX, Northrop-Grumman, Cal Poly San Luis Obispo, Department of Physics, University of California at Davis, Davis 95616, United States Department of Agriculture-Agriculture Research Service, Chemistry/California State University Fresno, Physics/California State University Fresno, University of California Santa Barbara, University of California Merced, UC Merced, Stanford University, New Economic School, California Polytechnic State University San Luis Obispo, Indiana University - Purdue University Indianapolis, California Polytechnic State University, San Luis Obispo, Chair of the Physics Department