A catalogue of nuclear stellar velocity dispersions of nearby galaxies from  Hα STIS spectra to constrain supermassive black hole masses. Issue 1 (27th October 2018)

• Record Type: Journal Article
• Authors: Pagotto, Ilaria; Corsini, Enrico Maria; Sarzi, Marc; Pagani, Bruno; Dalla Bontà, Elena; Morelli, Lorenzo; Pizzella, Alessandro
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 483:Issue 1(2019)
• Page Start: 57
• Page End: 69
• Publication Date: 2018-10-27
• Subjects: black hole physics -- galaxies: fundamental parameters -- galaxies: kinematics and dynamics -- galaxies: photometry; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2918
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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.