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2019MNRAS.483...57P - Mon. Not. R. Astron. Soc., 483, 57-69 (2019/February-2)

A catalogue of nuclear stellar velocity dispersions of nearby galaxies from Hα STIS spectra to constrain supermassive black hole masses.


Abstract (from CDS):

We present new measurements for the nuclear stellar velocity dispersion σ* within sub-arcsecond apertures for 28 nearby galaxies. Our data consist of Space Telescope Imaging Spectrograph (STIS) long-slit spectra obtained with the G750M grating centred on the Hα spectral range. We fit the spectra using a library of single stellar population models and Gaussian emission lines, while constraining in most cases the stellar-population content from an initial fit to G430L STIS spectra. We illustrate how these σ* measurements can be useful for constraining the mass M* of supermassive black holes (SBHs) by concentrating on the cases of the lenticular galaxies NGC 4435 and NGC 4459. These are characterized by similar ground-based half-light radii stellar velocity dispersion σe values but remarkably different M* as obtained from modelling their central ionized-gas kinematics, where NGC 4435 appears to host a significantly undermassive SBH compared to what is expected from the M* - σe relation. For both galaxies, we build Jeans axisymmetric dynamical models to match the ground-based stellar kinematics obtained with Spectrographic Areal Unit for Research on Optical Nebulae integral-field spectrograph, including an SBH with M* value as predicted by the M* - σe relation and using high-resolution HST images taken with the Advanced Camera for Surveys to construct the stellar-mass model. By mimicking the HST observing conditions we use such reference models to make a prediction for the nuclear σ* value. Whereas this was found to agree with our nuclear σ* measurement for NGC 4459, for NGC 4435 the observed σ* is remarkably smaller than the predicted one, which further suggests that this galaxy could host an undermassive SBH.

Abstract Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): black hole physics - galaxies: fundamental parameters - galaxies: kinematics and dynamics - galaxies: photometry

Simbad objects: 40

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