Calibrating stellar velocity dispersions based on spatially resolved h-band spectra for improving the mbh–σ∗ relation

To calibrate stellar velocity dispersion measurements from optical and near-IR stellar lines, and to improve the black hole mass (MBH)–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 MBH 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 MBH–σ∗ relation