49 research outputs found
Does the stellar disc flattening depend on the galaxy type?
We analyze the dependence of the stellar disc flatness on the galaxy
morphological type using 2D decomposition of galaxies from the reliable
subsample of the Edge-on Galaxies in SDSS (EGIS) catalogue. Combining these
data with the retrieved models of the edge-on galaxies from the Two Micron All
Sky Survey (2MASS) and the Spitzer Survey of Stellar Structure in Galaxies
(SG) catalogue, we make the following conclusions:
(1) The disc relative thickness in the near- and mid-infrared
passbands correlates weakly with morphological type and does not correlate with
the bulge-to-total luminosity ratio in all studied bands.
(2) Applying an 1D photometric profile analysis overestimates the disc
thickness in galaxies with large bulges making an illusion of the relationship
between the disc flattening and the ratio .
(3) In our sample the early-type disc galaxies (S0/a) have both flat and
"puffed" discs. The early spirals and intermediate-type galaxies have a large
scatter of the disc flatness, which can be caused by the presence of a bar:
barred galaxies have thicker stellar discs, on average. On the other hand, the
late-type spirals are mostly thin galaxies, whereas irregular galaxies have
puffed stellar discs.Comment: 17 pages, 17 figures, accepted for publication in MNRA
Polar-bulge galaxies
Based on SDSS data, we have selected a sample of nine edge-on spiral galaxies
with bulges whose major axes show a high inclination to the disk plane. Such
objects are called polar-bulge galaxies. They are similar in their morphology
to polar-ring galaxies, but the central objects in them have small size and low
luminosity. We have performed a photometric analysis of the galaxies in the g
and r bands and determined the main characteristics of their bulges and disks.
We show that the disks of such galaxies are typical for the disks of spiral
galaxies of late morphological types. The integrated characteristics of their
bulges are similar to the parameters of normal bulges. The stellar disks of
polar-bulge galaxies often show large-scale warps, which can be explained by
their interaction with neighboring galaxies or external accretion from outside.Comment: 8 pages, 3 figure
The Catalog of Edge-on Disk Galaxies from SDSS. Part I: the catalog and the Structural Parameters of Stellar Disks
We present a catalog of true edge-on disk galaxies automatically selected
from the Seventh Data Release (DR7) of the Sloan Digital Sky Survey. A visual
inspection of the , and images of about 15000 galaxies allowed us to
split the initial sample of edge-on galaxy candidates into 4768 (31.8% of the
initial sample) genuine edge-on galaxies, 8350 (55.7%) non-edge-ons, and 1865
(12.5%) edge-on galaxies not suitable for simple automatic analysis because
these objects show signs of interaction, warps, or nearby bright stars project
on it. We added more candidate galaxies from RFGC, EFIGI, RC3, and Galaxy Zoo
catalogs found in the SDSS footprints. Our final sample consists of 5747
genuine edge-on galaxies. We estimate the structural parameters of the stellar
disks (the stellar disk thickness, radial scale length, and central surface
brightness) in the galaxies by analyzing photometric profiles in each of the g,
r, and i images. We also perform simplified 3-D modeling of the light
distribution in the stellar disks of edge-on galaxies from our sample. Our
large sample is intended to be used for studying scaling relations in the
stellar disks and bulges and for estimating parameters of the thick disks in
different types of galaxies via the image stacking. In this paper we present
the sample selection procedure and general description of the sample.Comment: Accepted for publication in Ap
A new, purely photometric method for determination of resonance locations in spiral galaxies
The knowledge of the positions of the corotation resonance in spiral arms is
a key way to estimate their pattern speed, which is a fundamental parameter
determining the galaxy dynamics. Various methods for its estimation have been
developed, but they all demonstrate certain limitations and a lack of agreement
with each other. Here, we present a new method for estimating the corotation
radius. This method takes into account the shape of the profile across the arm
and its width and, thus, only photometric data is needed. The significance of
the method is that it can potentially be used for the farthest galaxies with
measurable spiral arms. We apply it to a sample of local galaxies from
Savchenko et al. and compare the obtained corotation radii with those
previously measured in the literature by other methods. Our results are in good
agreement with the literature. We also apply the new method to distant galaxies
from the COSMOS field. For the first time, corotation locations for galaxies
with photometric redshifts up to are measured.Comment: accepted in MNRAS Letter
Gravitational stability and dynamical overheating of stellar disks of galaxies
We use the marginal stability condition for galactic disks and the stellar
velocity dispersion data published by different authors to place upper limits
on the disk local surface density at two radial scalelengths .
Extrapolating these estimates, we constrain the total mass of the disks and
compare these estimates to those based on the photometry and color of stellar
populations. The comparison reveals that the stellar disks of most of spiral
galaxies in our sample cannot be substantially overheated and are therefore
unlikely to have experienced a significant merging event in their history. The
same conclusion applies to some, but not all of the S0 galaxies we consider.
However, a substantial part of the early type galaxies do show the stellar
velocity dispersion well in excess of the gravitational stability threshold
suggesting a major merger event in the past. We find dynamically overheated
disks among both seemingly isolated galaxies and those forming pairs. The ratio
of the marginal stability disk mass estimate to the total galaxy mass within
four radial scalelengths remains within a range of 0.4---0.8. We see no
evidence for a noticeable running of this ratio with either the morphological
type or color index.Comment: 25 pages, 5 figures, accepted to Astronomy Letter