A catalogue of nuclear stellar velocity dispersions of nearby galaxies from H$alpha$ STIS spectra to constrain supermassive black hole masses. (arXiv:1811.03160v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pagotto_I/0/1/0/all/0/1">I. Pagotto</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Corsini_E/0/1/0/all/0/1">E. M. Corsini</a> (1 and 2), <a href="http://arxiv.org/find/astro-ph/1/au:+Sarzi_M/0/1/0/all/0/1">M. Sarzi</a> (3 and 4), <a href="http://arxiv.org/find/astro-ph/1/au:+Pagani_B/0/1/0/all/0/1">B. Pagani</a> (5), <a href="http://arxiv.org/find/astro-ph/1/au:+Bonta_E/0/1/0/all/0/1">E. Dalla Bontà</a> (1 and 2), <a href="http://arxiv.org/find/astro-ph/1/au:+Morelli_L/0/1/0/all/0/1">L. Morelli</a> (6), <a href="http://arxiv.org/find/astro-ph/1/au:+Pizzella_A/0/1/0/all/0/1">A. Pizzella</a> (1 and 2) ((1) Dipartimento di Fisica e Astronomia "G. Galilei'', Università di Padova, Italy, (2) INAF-Osservatorio Astronomico di Padova, Italy, (3) Armagh Observatory and Planetarium, UK, (4) Centre for Astrophysics Research, University of Hertfordshire, UK, (5) Département Sciences de la Matière, ENS de Lyon, France, (6) Instituto de Astronomia y Ciencias Planetarias, Universidad de Atacama, Chile)
We present new measurements for the nuclear stellar velocity dispersion
$sigma_{ast}$ 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 H$alpha$ 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
$sigma_{ast}$ measurements can be useful for constraining the mass
$M_{bullet}$ of supermassive black holes (SBHs) by concentrating on the cases
of the lenticular galaxies NGC4435 and NGC4459. These are characterized by
similar ground-based half-light radii stellar velocity dispersion $sigma_{rm
e}$ values but remarkably different $M_{bullet}$ as obtained from modelling
their central ionised-gas kinematics, where NGC4435 appears to host a
significantly undermassive SBH compared to what is expected from the
$M_{bullet}-sigma_{rm e}$ relation. For both galaxies, we build Jeans
axisymmetric dynamical models to match the ground-based stellar kinematics
obtained with SAURON integral-field spectrograph, including a SBH with
$M_{bullet}$ value as predicted by the $M_{bullet}-sigma_{rm e}$ 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
$sigma_{ast}$ value. Whereas this was found to agree with our nuclear
$sigma_{ast}$ measurement for NGC4459, for NGC4435 the observed
$sigma_{ast}$ is remarkably smaller than the predicted one, which further
suggests that this galaxy could host an undermassive SBH.
We present new measurements for the nuclear stellar velocity dispersion
$sigma_{ast}$ 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 H$alpha$ 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
$sigma_{ast}$ measurements can be useful for constraining the mass
$M_{bullet}$ of supermassive black holes (SBHs) by concentrating on the cases
of the lenticular galaxies NGC4435 and NGC4459. These are characterized by
similar ground-based half-light radii stellar velocity dispersion $sigma_{rm
e}$ values but remarkably different $M_{bullet}$ as obtained from modelling
their central ionised-gas kinematics, where NGC4435 appears to host a
significantly undermassive SBH compared to what is expected from the
$M_{bullet}-sigma_{rm e}$ relation. For both galaxies, we build Jeans
axisymmetric dynamical models to match the ground-based stellar kinematics
obtained with SAURON integral-field spectrograph, including a SBH with
$M_{bullet}$ value as predicted by the $M_{bullet}-sigma_{rm e}$ 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
$sigma_{ast}$ value. Whereas this was found to agree with our nuclear
$sigma_{ast}$ measurement for NGC4459, for NGC4435 the observed
$sigma_{ast}$ is remarkably smaller than the predicted one, which further
suggests that this galaxy could host an undermassive SBH.
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