602 research outputs found
Photometric structure of polar-ring galaxies
The results of B, V, R surface photometry of three polar-ring galaxies (PRGs)
-- A0017+2212, UGC1198, UGC4385 -- are presented. The data were acquired at the
6-m telescope of the Special Astrophysical Observatory of the Russian Academy
of Sciences. It was shown that all three galaxies are peculiar late-type
spirals in the state of ongoing interaction or merging. We discuss available
photometric properties of the PRGs with spiral hosts and consider the
Tully-Fisher relation for different types of PRGs. In agreement with Iodice et
al. (2003), we have shown that true PRGs demonstrate ~1/3 larger maximum
rotation velocities than spiral galaxies of the same luminosity. Peculiar
objects with forming polar structures satisfy, on average, the Tully-Fisher
relation for disk galaxies but with large scatter.Comment: 12 pages, A&A accepte
Tidal Tails and Galaxy Evolution
We review recent results on the tidal structures of spiral galaxies. Topics
included are general characteristics of tails; kinematics of tidal structures
and dark haloes of host galaxies; frequency of tidal distortions at z~1.Comment: 5 pages, "Morphology and Dynamics of Stellar Systems: Star Clusters,
Galactic Arms and Rings", Proc. JENAM-2000, in pres
Sky surveys and deep fields of ground-based and space telescopes
Selected results obtained in major observational sky surveys (DSS, 2MASS,
2dF, SDSS) and deep field observations (HDF, GOODS, HUDF, etc.) are reviewed.
Modern surveys provide information on the characteristics and space
distribution of millions of galaxies. Deep fields allow one to study galaxies
at the stage of formation and to trace their evolution over billions of years.
The wealth of observational data is altering the face of modern astronomy: the
formulation of problems and their solutions are changing and all the previous
knowledge, from planetary studies in the solar system to the most distant
galaxies and quasars, is being revised.Comment: 22 pages, 18 figure
Polar-ring galaxies: the SDSS view on the symbiotic galaxies
Polar-ring galaxies are multi-spin systems, showing star formation in a blue
late-type component, perpendicular to a red early-type one, revealing how
galaxy formation can sometimes occur in successive steps. We perform
two-dimensional decomposition in the , , bandpasses of 50 polar-ring
galaxies (PRGs) from the Sloan Digital Sky Survey. Each object was fit with a
S\'ersic host galaxy and a S\'ersic ring. Our general results are: (i) The
central (host) galaxies of the PRGs are non-dwarf sub- galaxies with
colors typical for early-type galaxies. (ii) Polar structures in our sample
are, on average, fainter and bluer than their host galaxies. (iii) In most
galaxies, the stellar mass M of the polar component is not negligible in
comparison with that of the host. (iv) The distributions of the host galaxies
on the size -- luminosity and Kormendy diagrams are shifted by to
fainter magnitudes in comparison with E/S0 galaxies. It means that the PRGs
hosts are more similar to quenched disks than to ordinary early-type galaxies.
(v) All the PRGs in our sample are detected in mid-infrared by WISE, and we
derive from the 22m luminosity their star formation rate (SFR). Their
SFR/M ratio is larger than for the early-type galaxy sample of Atlas, showing that the star forming disk brings a significant contribution to
the new stars. Globally, PRGs appear frequently on the green valley in the
mass-color diagram, revealing the symbiotic character between a red-sequence
host and a blue cloud ring.Comment: 8 pages, 11 figures, accepted for publication in MNRA
The polar-ring galaxies NGC 2685 and NGC 3808B (VV 300)
Polar-ring galaxies (PRG) are among the most interesting examples of interaction between galaxies. A PRG is a galaxy with an elongated main body surrounded by a ring (or a disk) of stars, gas, and dust rotating in a near-polar plane (Schweizer, Whitmore, and Rubin, 1983). Accretion of matter by a massive lenticular galaxy from either intergalactic medium or a companion galaxy is usually considered as an explanation of the observed structure of PRG. In the latter case there are two possibilities: capture and merging of a neighbor galaxy, and accretion of mass from a companion galaxy during a close encounter. Two PRG formation scenarios just mentioned are illustrated here by the results of our observations of the peculiar galaxies NGC 2685 and NGC 3808B
UGC 7388: a galaxy with two tidal loops
We present the results of spectroscopic and morphological studies of the
galaxy UGC7388 with the 8.1-m Gemini North telescope. Judging by its observed
characteristics, UGC7388 is a giant late-type spiral galaxy seen almost
edge-on. The main body of the galaxy is surrounded by two faint (\mu(B) ~ 24
and \mu(B) ~ 25.5) extended (~20-30 kpc) loop-like structures. A large-scale
rotation of the brighter loop about the main galaxy has been detected. We
discuss the assumption that the tidal disruption of a relatively massive
companion is observed in the case of UGC7388. A detailed study and modeling of
the observed structure of this unique galaxy can give important information
about the influence of the absorption of massive companions on the galactic
disks and about the structure of the dark halo around UGC7388.Comment: 8 pages, 5 figure
The modified dynamics is conducive to galactic warp formation
There is an effect in the modified dynamics (MOND) that is conducive to
formation of warps. Because of the nonlinearity of the theory the internal
dynamics of a galaxy is affected by a perturber over and above possible tidal
effects. For example, a relatively distant and light companion or the mean
influence of a parent cluster, with negligible tidal effects, could still
produce a significant warp in the outer part of a galactic disk. We present
results of numerical calculations for simplified models that show, for
instance, that a satellite with the (baryonic) mass and distance of the
Magellanic clouds can distort the axisymmetric field of the Milky Way enough to
produce a warp of the magnitude (and position) observed. Details of the warp
geometry remain to be explained: we use a static configuration that can produce
only warps with a straight line of nodes. In more realistic simulations one
must reckon with the motion of the perturbing body, which sometimes occurs on
time scales not much longer than the response time of the disk.Comment: Latex, 9 pages, 3 embedded figures, to be published in ApJ
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