arXiv subjects

A. V. Moiseev

Publications and source records attributed to A. V. Moiseev.

At least 73 records · Page 4Linked to original sources

arXiv2010

RXJ 0921+4529: a binary quasar or gravitational lens?

We report the new spectroscopic observations of the gravitational lens RXJ 021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6-m telescope. The new spectral observations were compared with the previously observed spectra of components A and B of RXJ 0921+4529, i.e. the same components observed in different epochs. We found a significant difference in the spectrum between the components that cannot be explained with microlensing and/or spectral variation. We conclude that RXJ 0921+4529 is a binary quasar system, where redshifts of quasars A and B are 1.6535 +/- 0.0005 and 1.6625 +/- 0.0015, respectively.

astro-ph.CO↗

arXiv2010

Seyfert galaxies that are undergoing merging but appear non-interacting

We present new broad-band optical images of some merging Seyfert galaxies that were earlier considered to be non-interacting objects. On our deep images obtained at the Russian 6-m telescope we have detected elongated tidal envelopes belonging to satellites debris with a surface R-band brightness about 25-26.5 mag/arcsec^2. These structures are invisible in Sloan Digital Sky Survey (SDSS) pictures because of their photometric limit. We found that 35 per cent of the sample of isolated galaxies has undergone merging during the last 0.5-1 Gyr. Our results suggest that statistic studies based on popular imaging surveys (SDSS or Second Palomar Observatory Sky Survey (POSS-II)) can lead to underestimation of the fraction of minor mergers among galaxies with active nuclei (AGN). This fact impacts on statistics and must be taken into consideration when finding connection between minor/major merging or interactions and nucleus activity.

astro-ph.CO↗

arXiv2010

Malin 1: interacting galaxy pair?

Malin 1 is a unique, extraordinarily large low surface brightness galaxy. The structure and the origins of the galaxy are poorly understood. The reason for such a situation is an absence of detailed observational data, especially, of high-resolution kinematics. In this Letter we study the stellar kinematics of the inner part (r < 15 kpc) of Malin 1. We present spectroscopic arguments in favour of a small galaxy - Malin 1B - being a companion probably interacting with the main galaxy - Malin 1. This object is clearly seen in many published images of Malin 1 but is not mentioned in any astronomical databases. Malin 1B is located at the projected distance of 14 kpc from the Malin 1's nucleus and has small - 65$\pm$16 km/s - relative velocity, which we determined for the first time. We suggest that ongoing interaction with Malin 1B can explain main morphological features of the Malin 1's central region - two-armed spiral structure, a bar, and an external one-armed spiral pattern. We also investigated the large scale environment of Malin 1 and postulate that the galaxy SDSS J123708.91+142253.2 might be responsible for the formation of extended low-surface brightness envelope by means of head-on collision with Malin 1 (in the framework of collision scenario proposed by Mapelli et al. 2008). To test the collisional origins of Malin 1 global structure, more observational data and new numerical models are needed.

astro-ph.CO↗

arXiv2010

A Region of Violent Star Formation in the Irr Galaxy IC 10: Structure and Kinematics of Ionized and Neutral Gas

We have used observations of the galaxy IC 10 at the 6-m telescope of the Special Astrophysical Observatory with the SCORPIO focal reducer in the Fabry-Perot interferometer mode and with the MPFS spectrograph to study the structure and kinematics of ionized gas in the central region of current intense star formation. Archive VLA 21-cm observations are used to analyze the structure and kinematics of neutral gas in this region. High-velocity wings of the H-alpha and [SII] emission lines were revealed in the inner cavity of the nebula HL 111 and in other parts of the complex of violent star formation. We have discovered local expanding neutral-gas shells around the nebulae HL 111 and HL 106.

astro-ph.CO↗

arXiv2010

Very metal-poor galaxies: ionized gas kinematics in nine objects

The study of ionized gas morphology and kinematics in nine eXtremely Metal-Deficient (XMD) galaxies with the scanning Fabry-Perot interferometer on the SAO 6-m telescope is presented. Some of these very rare objects (with currently known range of O/H of 7.12 < 12+log(O/H) < 7.65, or Zo/35 < Z < Zo/10) are believed to be the best proxies of `young' low-mass galaxies in the high-redshift Universe. One of the main goals of this study is to look for possible evidence of star formation (SF) activity induced by external perturbations. Recent results from HI mapping of a small subsample of XMD star-forming galaxies provided confident evidence for the important role of interaction-induced SF. Our observations provide complementary or new information that the great majority of the studied XMD dwarfs have strongly disturbed gas morphology and kinematics or the presence of detached components. We approximate the observed velocity fields by simple models of a rotating tilted thin disc, which allow us the robust detection of non-circular gas motions. These data, in turn, indicate the important role of current/recent interactions and mergers in the observed enhanced star formation. As a by-product of our observations, we obtained data for two LSB dwarf galaxies: Anon J012544+075957 that is a companion of the merger system UGC 993, and SAO 0822+3545 which shows off-centre, asymmetric, low SFR star-forming regions, likely induced by the interaction with the companion XMD dwarf HS 0822+3542.

astro-ph.CO↗

arXiv2009

Gas Emission Spectrum in the Irr Galaxy IC 10

Spectroscopic long-slit observations of the dwarf Irr galaxy IC 10 were conducted at the 6-m Special Astrophysical Observatory telescope with the SCORPIO focal reducer. The ionized-gas emission spectra in the regions of intense current star formation were obtained for a large number of regions in IC 10. The relative abundances of oxygen, N+, and S+ in about twenty HII regions and in the synchrotron superbubble were estimated. We found that the galaxy-averaged oxygen abundance is 12 + log(O/H) = 8.17 +- 0.35 and the metallicity is Z = 0.18 +- 0.14 Z_sun. Our abundances estimated from the strong emission lines are found to be more reliable than those obtained by comparing diagnostic diagrams with photoionization models.

astro-ph.CO↗

arXiv2009

3D spectroscopy of merger Seyfert galaxy Mrk 334: nuclear starburst, superwind and the circumnuclear cavern

We are presenting new results on kinematics and structure of the Mrk 334 Seyfert galaxy. Panoramic (3D) spectroscopy is performed at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences using the MPFS integral-field spectrograph and scanning Fabry--Perot interferometer. The deep images have revealed that Mrk 334 is observed during the final stage of its merging with a massive companion. A possible mass ratio ranges from 1/5 to 1/3. The merger has triggered mass redistribution in the disk resulting in an intensification of nuclear activity and in a burst of star formation in the inner region of the galaxy. The circumnuclear starburst is so intense that its contribution to the gas ionization exceeds that contribution of the AGN. We interpret the nuclear gas outflow with velocities of ~200 km/s as a galactic superwind that accompanies the violent star formation. This suggestion is consistent with the asymmetric X-ray brightness distribution in Mrk 334. The trajectory of the fragments of the disrupted satellite in the vicinity of the main galaxy nucleus can be traced. In the galaxy disk a cavern is found that is filled with a low-density ionized gas. We consider this region to be the place where the remnants of the companion have recently penetrated through the gaseous disk of the main galaxy.

astro-ph.CO↗

arXiv2009

3D spectroscopic study of galactic rings: formation and kinematics

In this review we consider various ring structures that are observed in galaxies. Formation and evolution of the rings are interesting problems in studies of galactic morphology. They are related to such fundamental aspects of galactic evolution and dynamics as the nature and distribution of the dark matter in galaxies, galactic interactions and internal secular evolution of galactic substructures. A significant fraction of galactic rings forms in the disks due to gravitational torques from bar-like patterns. In contrast to this internally driven origin, the phenomenon of the polar-ring galaxies is closely connected with the processes of intergalactic interactions and merging. A rare class of collisional rings reveals the density waves triggered in the stellar and gaseous disks after a strong head-on collision with a companion. We briefly review the status of studies of gas kinematics in the rings of different origin. We stress that velocity fields of the ionized gas obtained with the Fabry-Perot interferometers provide a very important information for these studies.

astro-ph.CO↗

arXiv2008

Two more disk galaxies with global gas counterrotation

We report a discovery of extended counterrotating gaseous disks in early-type disk galaxies NGC 2551 and NGC 5631. To find them, we have undertaken complex spectral observations including integral-field spectroscopy for the central parts of the galaxies and long-slit deep spectroscopy to probe the external parts. The line-of-sight velocity fields have been constructed and compared to the photometric structure of the galaxies. As a result, we have revealed full-size counterrotating gaseous disks, the one coplanar to the stellar disk in NGC 2551 and the other inclined to the main stellar disk in NGC 5631. We suggest that we observe the early stages of minor-merger events which may be two different stages of the process of lenticular galaxy formation in rather sparse environments.

astro-ph↗

arXiv2008

3D spectroscopy of candidate double-barred lenticular galaxies

Significant fraction of barred galaxies hosts secondary bar-like structures on optical and NIR images. The circumnuclear dynamics of double-barred objects are still not well understood, observational data concerning kinematics are incomplete and inconsistent. In order to compare the simulations results with observations, we have started new spectroscopic studying of stellar kinematics in lenticular galaxies from Peter Erwin's catalog of secondary bars. We present first results concerning their stellar kinematics based on the observations performed with the integral-field spectrograph MPFS at the Russian 6-m telescope.

astro-ph↗

arXiv2008

Warped polar ring in the Arp 212 galaxy

The Fabry-Perot scanning interferometer mounted on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences is used to study the distribution and kinematics of ionized gas in the peculiar galaxy Arp 212 (NGC 7625, III Zw 102). Two kinematically distinct subsystems - the inner disk and outer emission filaments, are found within the optical radius of the galaxy. The first subsystem, at galactocentric distances r<3.5 kpc, rotates in the plane of the stellar disk. The inner part of the ionized-gas disk (r<1.5-2 kpc) exactly coincides with the previously known disk consisting of molecular gas. The second subsystem of ionized gas is located at galactocentric distances 2-6 kpc. This subsystem rotates in a plane tilted by a significant angle to the stellar disk. The angle of orbital inclination in the outer disk increases with galactocentric distance and reaches 50 degrees at r=6 kpc. The ionized fraction of the gaseous disk does not show up beyond this galactocentric distance, but we believe that the HI disk continues to warp and approaches the plane that is polar with respect to the inner disk of the galaxy. Hence Arp 212 can be classified as a galaxy with a polar ring (or a polar disk). The observed kinematics of the ionized and neutral gas can be explained assuming that the distribution of gravitational potential in the galaxy is not spherically symmetric. Most probably, the polar ring have formed via accretion of gas from the dwarf satellite galaxy UGC 12549.

astro-ph↗

arXiv2008

Kinematics of the Nebular Complex MH9/10/11 Associated with HoIX X-1

We report the results of our observations of the nebular complex MH9/10/11, associated with the ULX HoIX X-1, with scanning Fabry-Perot Interferometer. Two regions differing by their kinematics and line ratios may be distinguished, roughly corresponding to the bubble nebula MH9/10 and fainter HII-region MH11. For MH9/10 we find the expansion rate of 20-70km/s that is different for the approaching and receding parts. MH11 is characterised by very low velocity dispersion (less than or about 15km/s) and nearly constant line-of-sight velocities. Properties of MH11 may be explained by photoionization of gas with hydrogen density of about 0.2cm^-3. Luminosity required for that should be of the order of 10^39erg/s. Similar power source is required to explain the expansion rate of MH9/10. Modelling results also indicate that oxygen abundance in MH11 is about solar.

astro-ph↗

arXiv2008

Reduction of CCD observations obtained with the Fabry-Perot scanning interferometer. II. Additional Procedures

We describe a software package used at the Special Astrophysical Observatory of the Russian Academy of Sciences to reduce and analyze the data obtained with the Fabry-Perot scanning interferometer. We already described most of the algorithms employed in our earlier Paper I (Moiseev, 2002). In this paper we focus on extra procedures required in the case of the use of a high-resolution Fabry-Perot interferometer: removal of ghosts and measurement of the velocity dispersion of ionized gas in galactic and extragalactic objects.

astro-ph↗

arXiv2008

Synchrotron superbubble in the galaxy IC10: the ionized gas structure, kinematics, and emission spectrum

We have investigated the structure, kinematics, and emission spectrum of the ionized gas in the synchrotron superbubble in the irregular galaxy IC 10 based on observations with the 6-m Special Astrophysical Observatory telescope with the SCORPIO focal reducer in three modes: direct imaging in the [SII](6717+6731)A lines, long-slit spectroscopy, and spectroscopy with a scanning Fabry--Perot interferometer. We have identified a bright (in the [SII] lines) filamentary optical shell and determined its expansion velocity, mass, and kinetic energy. The nature of the object is discussed.

astro-ph↗

arXiv2008

Early-Type Disk Galaxies: Structure and Kinematics

Spectroscopic observations of three lenticular (S0) galaxies (NGC 1167, NGC 4150, and NGC 6340) and one SBa galaxy (NGC 2273) have been taken with the 6-m telescope of the Special AstrophysicalObservatory of the Russian Academy of Sciences aimed to study the structure and kinematic properties of early-type disk galaxies. The radial profiles of the stellar radial velocities and the velocity dispersion are measured. N-body simulations are used to construct dynamical models of galaxies containing a stellar disk, bulge, and halo. The masses of individual components are estimated formaximum-mass disk models. A comparison of models with estimated rotational velocities and the stellar velocity dispersion suggests that the stellar disks in lenticular galaxies are "overheated"; i.e., there is a significant excess velocity dispersion over the minimum level required to maintain the stability of the disk. This supports the hypothesis that the stellar disks of S0 galaxies were subject to strong gravitational perturbations. The relative thickness of the stellar disks in the S0 galaxies considered substantially exceed the typical disk thickness of spiral galaxies.

astro-ph↗

arXiv2008

3D spectroscopy of the ionized gas kinematics in galactic rings

The kinematics of galactic rings were studied with a scanning Fabry-Perot interferometer mounted in the multi-mode focal reducer SCORPIO (Afanasiev & Moiseev 2005) at the SAO RAS 6-m telescope. The analysis of the ionized gas velocity fields allows us to understand the nature of the ring formation in several galaxies. The different types of the rings in the presented objects (resonanced, collisional, polar) were caused by the various sorts of interactions: merging, head-on collisions.

astro-ph↗

arXiv2008

Merging as a key to reforming of disk and AGN triggering in Sy galaxy Mrk334

We have studied the kinematics of the ionized gas and stellar component in Mrk334 using methods of panoramic (3D) spectroscopy. The observations were performed at the prime focus of the SAO RAS 6-m telescope with the integral-field spectrograph MPFS (Afanasiev et al. 2001) and with a scanning Fabry-Perot interferometer (FPI), installed on the multimode device SCORPIO (Afanasiev & Moiseev 2005). Based on these data, the monochromatic maps and velocity fields in different emission lines of the ionized gas were constructed. The diagnostic diagrams have been made based on the emission lines ratios.

astro-ph↗

arXiv2007

The gas emission spectrum in a star-forming region in the BCD galaxy VII Zw 403 (UGC 6456)

Observations with the 6-m telescope of the Special Astrophysical Observatory obtained with the MPFS integral-field spectrograph and a longslit spectrograph with the SCORPIO focal reducer are used to analyze the emission spectrum of the ionized gas in a star-forming region in the BCD galaxy VII Zw 403. We present images of the galactic central region in the H-alpha, H-beta, [SII], and [OIII] emission lines, together with maps of the relative [OIII]/H-beta and [SII]/H-alpha intensities. We have determined the parameters of the gas in bright ionized supershells, and estimated the relative abundances of oxygen, nitrogen, and sulfur; a low relative N/O abundance was detected.

astro-ph↗