Medium Resolution Near-Infrared Spectra of the Host Galaxies of Nearby Quasars

TL;DR

This study presents near-infrared spectra of host galaxies of nearby quasars, measuring velocity dispersions and estimating black hole masses, demonstrating the effectiveness of adaptive optics in resolving quasar-host spectra.

Contribution

It provides new near-infrared spectral data of quasar host galaxies and applies an improved data reduction method to measure velocity dispersions and black hole masses.

Findings

Velocity dispersions measured for two quasars.

Black hole masses estimated using the M_BH-sigma relation.

Results consistent with previous broad emission line estimates.

Abstract

We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844 + 349 (z=0.064), PG 1226 + 023 (z=0.158), and PG 1426+015 (z=0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 um), Si I (1.589 um) and CO (6-3) (1.619 um), and measured the velocity dispersions of PG 0844 + 349 to be 132+/-110 km s-1 and PG 1426 + 015 to be 264+/-215 km s-1. By using an M_BH-sigma relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349, log(M_BH/M_SUN) = 7.7+/-5.5 and PG 1426+015, log(M_BH/M_SUN) = 9.0+/-7.5. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5.