CALIBRATING STELLAR VELOCITY DISPERSIONS BASED ON SPATIALLY RESOLVEDH-BAND SPECTRA FOR IMPROVING THEMBH-σ*RELATION

To calibrate stellar velocity dispersion measurements from optical and near-IR stellar lines, and to improve the black hole mass ( M BH )–stellar velocity dispersion (σ * ) relation, we measure σ * based on high-quality H -band spectra for a sample of 31 nearby galaxies, for which dynamical M BH is available in the literature. By comparing velocity dispersions measured from stellar lines in the H -band with those measured from optical stellar lines, we find no significant difference, suggesting that optical and near-IR stellar lines represent the same kinematics and that dust effect is negligible for early-type galaxies. Based on the spatially resolved rotation and velocity dispersion measurements along the major axis of each galaxy, we find that a rotating stellar disk is present for 80% of galaxies in the sample. For galaxies with a rotation component, σ * measured from a single aperture spectrum can vary by up to ∼20%, depending on the size of the adopted extraction aperture. To correct for the rotational broadening, we derive luminosity-weighted σ * within the effective radius of each galaxy, providing uniformly measured velocity dispersions to improve the M BH –σ * relation.