Stellar velocity dispersions in AGN – II: Methods

Abstract

Stellar velocity dispersions in AGN are useful indicators of the black-hole mass (through the M_{[bull ]}−σ_{[sstarf ]} relation) and nuclear stellar populations (through the M/L ratio). We have collected near-infrared spectra of ∼40 Seyferts in the CaII triplet range in order to measure σ_{[sstarf ]} and investigate the connection between stellar populations and AGN properties. In this poster we present a comparison between two methods to measure velocity dispersions: (1) direct fitting (DFM) and (2) cross-correlation (CCM). (1) In DFM the spectra in the CaII triplet range is modeled as a combination of a broadened and shifted stellar spectrum (observed through the same instrumental setup) and a featureless continuum. This method has the advantage of making it easy to mask out noisy regions and sky residuals. (2) CCM converts the width of the star-galaxy cross-correlation function onto a velocity dispersion. We find that these methods yield velocity dispersions consistent to within 20 km s⁻¹ on-average. Our results are consistent to within 20 km s⁻¹ with those objects available in the literature.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html