摘要：Context. We present the largest catalog of detailed stellar kinematics
of the central parts of nearby galaxies, which includes higher moments of the
line-of-sight velocity distribution (LOSVD) function represented by the Gauss-Hermite
series. The kinematics is measured on a sample of galaxies selected from the Arecibo
Legacy Fast ALFA (Alfalfa) survey using spectroscopy from the Sloan Digital Sky Survey
(SDSS DR7).
Aims. The SDSS DR7 offers measurements of the LOSVD based on the
assumption of a pure Gaussian shape of the broadening function caused by the combination
of rotational and random motion of the stars in galaxies. We discuss the consequences of
this oversimplification since the velocity dispersion, one of the measured quantities,
often serves as the proxy to important modeling parameters such as the black-hole mass and
the virial mass of galaxies.
Methods. The publicly available pPXF code is used to calculate the full
kinematical profile for the sample galaxies including higher moments of their LOSVD. Both
observed and synthetic stellar libraries were used and the related template mismatch
problem is discussed.
Results. For the whole sample of 2180 nearby galaxies reflecting
morphological distribution characteristic for the local Universe, we successfully
recovered stellar kinematics of their central parts, including higher order moments of the
LOSVD function, for signal-to-noise above 50.
Conclusions. We show the consequences of the oversimplification of the
LOSVD function with Gaussian function on the velocity dispersion for the empirical and the
synthetic stellar library. For the empirical stellar library, this approximation leads to
an increase in the virial mass of 13% on average, while for the synthetic library the
effect is weaker, with an increase of 9% on average. Systematic erroneous estimates of the
velocity dispersion comes from the use of the synthetic stellar library instead of the
empirical one and is much larger than the value imposed by the use of the Gaussian
function. Only after a careful analysis of the template mismatch problem does one need to
address the issue of the deviation of the LOSVD from the Gaussian function. We also show
that the kurtotic parameter describing symmetrical departures from the Gaussian seems to
increase along the continuous morphological sequence from late- to early-type
galaxies.
关键词：catalogs;gravitation;galaxies: spiral;galaxies: elliptical and lenticular, cD;galaxies: kinematics and dynamics
