Search

We present a study of the nearby low-metallicity dwarf galaxy IC 1613, focusing on the search for massive stars and related feedback processes, as well as for faint supernova remnants (SNR) in late stages of evolution. We obtained the deepest images of IC 1613 in the narrow-band H{\alpha}, He II and [S II] emission lines and new long-slit spectroscopy observations using several facilities (6-m BTA, 2.5m SAI MSU, and 150RTT telescopes), in combination with the multi-wavelength archival data from MUSE/VLT, VLA, XMM-Newton, and Swift/XRT. Our deep narrow-band photometry identifies several faint shells in the galaxy, and we further investigate their physical characteristics with the new long-slit spectroscopy observations and the archival multi-wavelength data. Based on energy balance calculations and assumptions about their possible nature, we propose that one of the shells is a possible remnant of a supernova explosion. We study five out of eight Wolf-Rayet (WR) star candidates previously published for this galaxy using the He ii emission line mapping, MUSE/VLT archival spectra, and new long-slit spectra. Our analysis discards the considered WR candidates and finds no new ones. We found P Cyg profiles in H{\alpha} line in two stars, which we classify as Luminous Blue Variable (LBV) star candidates. Overall, the galaxy IC 1613 may have a lower rate of WR star formation than previously suggested.

We investigated the ionised and atomic gas kinematics and excitation state in the central region of ongoing star formation of the nearby low-metallicity dwarf galaxy Sextans B. The analysis is based on the new observations performed in Ha emission line with high resolution ($R \sim 16000$) scanning Fabry-Perot interferometer at the 6-m BTA SAO RAS telescope, and on the long-slit spectral observations at the 9.2-m SALT and 2.5-m CMO SAI MSU telescopes. Strong non-circular gas motions detected in the studied regions probably resulted from the off-plane gas motions and impact of stellar feedback. We identified six regions of elevated Ha velocity dispersion, five of which exhibit asymmetric or two-component Ha line profiles. Three of these regions are young ($<1.1$ Myr) expanding ($V_{\rm exp} \sim 25-50\ {\rm km\ s^{-1}}$) superbubbles. We argue that at least three regions in the galaxy could be supernova remnants. We conclude that supernovae feedback is the dominant source of energy for superbubbles in Sextans B, which is expected for such a low metallicity, although we cannot rule out a strong impact of pre-supernova feedback for one superbubble., Comment: 16 pages, 6+6 figures, 4 tables. submitted to MNRAS after revision

Ionization cones and relativistic jets give us one of the most large-scale example of active galactic nuclei (AGN) influence on the surrounding gas environment in galaxies and beyond. The study of ionization cones makes it possible not only to test the predictions of the unified model of galactic activity, but also to probe galaxy gas environment and trace how the luminosity of the nucleus changes over time (a light echo). In the external galactic or even extragalactic gas ionization cones create Extended Emission-Line Regions (EELRs) which can span distances from several to hundreds kpc away a host galaxy. We review the recent results of studying the gas kinematics and its ionization properties in EELRs with a special attention to search of fading AGN radiation on the time scale $\mbox{few}\times(10^4-10^5)$ yr. The role of modern narrow-band and integral-field surveys in these researches is also considered., Comment: 20 pages, 8 figures, 1 table. Accepted to Galaxies, comments welcome before proofreading. Mostly based on lectures given at the 50th conferences "Space physics" (Kourovka, Russia) and 14th Serbian Conference on Spectral Line Shapes in Astrophysics (Bajina Basta, Serbia)

Mrk 783 is a narrow-line Seyfert 1 galaxy that possesses a relatively large two-sided radio emission extending up to 14 kpc from the active nucleus possibly connected with a large-scale ionized gas emission. We obtained a deep [OIII] image that revealed an extended system of emission knots and diffuse ionized gas surrounding the main galaxy. The high-excited gas is related not only with the radio structure, but also with tidal features illuminated by the active nucleus radiation up to the projected distance 41 kpc as it follows from the emission lines intensities and kinematics derived from the long-slit spectroscopic data. Moreover the part of the disk of the companion galaxy SDSS J130257.20+162537.1 located at 99 kpc projected distances to the north of Mrk 783 also falls in the AGN ionizing cone. It is possible that Mrk 783 can be considered as `Hanny's Voorwerp precursor', i.e. a galaxy that demonstrates signs of sequential switching from radio-loud to radio-quiet nuclear activity, in the moment before falling of its ionization luminosity., Comment: 15 pages, 7 figures, 2 table. Submitted to Universe after revision, comments welcome

The S254-258 star-forming complex is a place of massive star formation where five OB-stars have created HII regions, visible as optical nebulae, and disrupted the parental molecular gas. In this work, we study the 3D structure of these \HII regions using optical spectroscopy and tunable-filter photometry with the 6-m and 1-m telescopes of the Special Astrophysical Observatory of the Russian Academy of Sciences. We construct maps of the optical extinction, and find that the HII emission is attenuated by neutral material with $2 \leq A_V \leq 5$ mag. The typical electron density in S255, and S257 is $\approx 100$ cm$^{-3}$, with enhancements up to 200 cm$^{-3}$ in their borders, and up to 400 cm$^{-3}$ toward the dense molecular cloud between them, where active star formation is taking place. We show that either a model of a clumpy dense neutral shell, where UV~photons penetrate through and ionize the gas, or a stellar wind, can explain the shell-like structure of the ionized gas. S255 is surrounded by neutral material from all sides, but S257 is situated on the border of a molecular cloud and does not have dense front and rear walls. The compact HII regions S256 and S258 are deeply embedded in the molecular clouds., Comment: accepted by MNRAS

New results on the radio-quiet type 2 quasar known as the Teacup galaxy (SDSSJ1430+1339) based on the long-slit and 3D spectroscopic data obtained at the Russian 6-m telescope are presented. The ionized gas giant nebula extending up to r=56 kpc in the [O III] emission line was mapped with the scanning Fabry-Perot interferometer. The direct estimation of the emission line ratios confirmed that the giant nebula is ionized by the AGN. Stars in the inner r<5 kpc are significantly younger than the outer host galaxy and have a solar metallicity. The central starburst age (~1 Gyr) agrees with possible ages for the galactic merger events and the previous episode of the quasar outflow produced two symmetric arcs visible in the [O III[ emission at the distances r=50-55 kpc. The ionized gas velocity field can be fitted by the model of a circular rotating disk significantly inclined or even polar to the stellar host galaxy., Comment: 11 pages, 6 figures, 1 table. The final version accepted to Universe

The new observational data concerning distribution, excitation, and kinematics of the ionized gas in the giant early-type disk galaxy NGC 2655 obtained at the 6m telescope of the Special Astrophysical Observatory (SAO RAS) and at the 2.5m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute (CMO SAI MSU) are presented in this work. The joint analysis of these and earlier spectral observations has allowed us to make a conclusion about multiple nature of the gas in NGC 2655. Together with a proper large gaseous disk experiencing regular circular rotation in the equatorial plane of the stellar potential of the galaxy for billions years, we observe also remnants of a merged small satellite having striked the central part of NGC 2655 almost vertically for some 10 million years ago., Comment: 22 pages, 8 figures, to appear in the Astrophysical Bulletin 2022, no.4

Feedback from massive stars shapes the ISM and affects the evolution of galaxies, but its mechanisms acting at the small scales ($\sim 10$ pc) are still not well constrained observationally, especially in the low-metallicity environments. We present the analysis of the ionized gas (focusing on its kinematics, which were never studied before), and its connection to the massive stars in the nearby ($D \sim 1.4$ Mpc) star-forming very metal-poor ($Z\sim 0.07 Z_\odot$) galaxy Sextans A. The analysis is based on the observations with a scanning Fabry-Perot interferometer, long-slit spectroscopy and imaging in emission lines with narrow-band tunable filters. We found 10 expanding superbubbles of ionized gas with ages of 1-3 Myr. We argue that 3 of them are probable supernovae remnants, while the pre-supernovae feedback is an important source of energy for blowing-out the remaining superbubbles. The two brightest sites of star formation exhibit signs of outflowing ionized gas, which is traced by its ionized and atomic gas kinematics and (in one case) by its emission line flux ratios. Overall, the ionized gas kinematics in Sextans A is highly affected by the feedback from several generations of massive stars and inconsistent with the mere solid-body rotation observed in atomic hydrogen., Comment: 19 pages, 12 figures, 5 tables. Accepted for publication in MNRAS

We report the identification of the unusual emission-line stellar-like object in the nearby low-metallicity (Z ~ 0.1Zsun) dwarf galaxy NGC 4068. Our observations performed with long-slit spectrograph and Fabry-Perot interferometer demonstrate high velocity dispersion in Ha line, presence of HeII4686A line and peculiarly low [SII]/[NII] fluxes ratio for this object. From observational data, we derived that the object represents a single star of high bolometric luminosity L~1.5*10^6 Lsun surrounded by an expanding nebula with kinematical age of t ~ 0.5Myr. The nebula exhibits significant nitrogen overabundance (log(N/O) ~ -0.05, that is by ~1.4dex higher than expected for low-metallicity galaxies). We suggested that this is a massive blue supergiant (BSG) or Wolf-Rayet (WR) star surrounded by its ejecta interacting with the interstellar medium. We calculated the models of the nebula using CLOUDY photoionization code, applying CMFGEN-modelled BSG and WR stars as ionisation sources. We found a best agreement between the modelled and observed spectra for the model assuming ionization by low-metallicity WR star of mass M*~80Msun, ionizing the nebula through the strong wind and enriching the interstellar medium with nitrogen., Comment: Minor revision

The emission-line intensity ratios are used to distinguish the main sources of gas ionization to study the state of galactic interstellar medium (ISM). In intermediate cases, when the contributions of radiation from some sources mix, the identification becomes uncertain. As an extra parameter, the gas velocity dispersion in the line-of-sight can be added to classical diagnostic diagrams (i.e., "BPT-sigma" relations) to help finding an appropriate solution. The minimum distance from the curve that bounds the H II-type ionization region for each point in BPT-sigma diagram can be used to characterize the excitation mechanism of the ionized gas. The shock excitation in the diffuse ionized gas (DIG) can be realized by the correlation between sigma and rho, while the H II regions with low level turbulent motions can be characterized by the absence of this correlation. We consider the "BPT-sigma" relation and the correlation between sigma and rho to determine the ionized gas excitation in several nearby star-forming galaxies. Distributions of the velocity dispersion are obtained from the scanning Fabry-Perot interferometer observations at the SAO RAS 6-m telescope, whereas the emission-line ratios are calculated from the archival long-slit spectroscopic data. The results of this study are reported for Mrk 370, NGC 4068, UGC 8313, and UGC 8508.

We present the results of a multiwavelength study of the nearby dwarf galaxy DDO 53 - a relatively isolated member of the M 81 group. We analyse the atomic and ionised gas kinematics (based on the observations with Fabry-Perot interferometer in H$\alpha$ line and archival data in HI 21 cm line), distribution, excitation and oxygen abundance of the ionised gas (based on the long-slit and integral-field spectroscopy and on imaging with narrow-band filters), and their relation with the young massive stars (based on archival HST data). We detect a faint 2-kpc sized supershell of ionised gas surrounding the galaxy. Most probably, this structure represents a large-scale gas outflow, however it could be also created by the ionising quanta leaking from star-forming regions to the marginally detected atomic hydrogen surrounding the galactic disc. We analyse the properties of the anomalous HI in the north part of the galaxy and find that its peculiar kinematics is also traced by ionised gas. We argue that this HI feature is related to the accreting gas cloud captured from the intergalactic medium or remaining after the merger event occurred >1 Gyr ago. The infalling gas produces shocks in the interstellar medium and could support the star formation activity in the brightest region in DDO 53., Comment: 20 pages, 13 figures, 4 tables. Accepted by MNRAS

Galaxies in dense environments, such as groups and clusters, experience various processes by which galaxies gain and lose gas. Using data from the SDSS-IV MaNGA survey, we previously reported the discovery of a giant (6 -- 8 kpc in diameter) H$\alpha$ blob, Totoro, about 8 kpc away from a pair of galaxies (Satsuki and Mei) residing in a galaxy group which is experiencing a group-group merger. Here, we combine interferometric $^{12}$CO(1--0) molecular gas data, new wide-field H$\alpha$, $u$-band data, and published X-ray data to determine the origin of the blob. Several scenarios are discussed to account for its multi-wavelength properties, including (1) H$\alpha$ gas being stripped from galaxy Satsuki by ram-pressure; (2) a separated low-surface-brightness galaxy; (3) gas being ejected or ionized by an active galactic nucleus (AGN); and (4) a cooling intra-group medium (IGM). Scenarios (1) and (2) are less favored by the present data. Scenario (3) is also less likely as there is no evidence for an active ongoing AGN in the host galaxy. We find that the CO (cold) and H$\alpha$ (warm) gas coexist with X-ray (hot) structures; moreover, the derived cooling time is within the regime where molecular and H$\alpha$ gas are expected. The coexistence of gas with different temperatures also agrees with that of cooling gas in other systems. Our multi-wavelength results strongly suggest that the CO and H$\alpha$ gas are the product of cooling from the IGM at its current location, i.e., cooling has occurred, and may be ongoing, well outside the host-galaxy core., Comment: 23 pages, 10 figures, Accepted for publication in ApJ

We present results of long-slit and panoramic spectroscopy of extended gaseous disks in 18 nearby S0 galaxies, mostly in groups. The gas in our S0s is found to be often accreted from outside that is implied by its decoupled kinematics: at least 5 galaxies demonstrate strongly inclined large-scale ionized-gas disks smoothly coupled with their outer HI disks, 7 galaxies reveal circumnuclear polar ionized-gas disks, and in NGC 2551 the ionized gas though confined to the main galactic plane however counterrotates the stellar component. The ionized-gas excitation analysis reveals the gas ionization by young stars in 12 of 18 S0 galaxies studied here; the current star formation in these galaxies is confined to the ring-like zones coinciding with the UV-rings. The gas oxygen abundance estimates in the rings are closely concentrated around the value of 0.7 $Z_\odot$ and do not correlate either with the ring radius nor with the metallicity of the underlying stellar population. By applying the tilted-ring analysis to the 2D velocity fields of the ionized gas, we have traced the orientation of the gas rotation-plane lines of nodes along the radius. We have found that current star formation proceeds usually just where the gas lies strictly in the stellar disk planes and rotates there circularly; the sense of the gas rotation does not matter (the counterrotating gas in NGC 2551 form stars currently). In the galaxies without signs of current star formation the extended gaseous disks are either in steady-state quasi-polar orientation (NGC 2655, NGC 2787, NGC 3414, UGC 9519), or are acquired recently through the highly inclined external filaments provoking probably shock-like excitation (NGC 4026, NGC 7280). Our data imply crucial difference of the external-gas accretion regime in S0s with respect to spiral galaxies: the geometry of the gas accretion in S0s is typically off-plane., Comment: 47 pages, re-submitted to ApJS after second revision. Comments welcome!

The ionization state and oxygen abundance distribution in a sample of polar-ring galaxies (PRGs) were studied from the long-slit spectroscopic observations carried out with the SCORPIO-2 focal reducer at the Russian 6-m telescope. The sample consists of 15 PRGs classified as `the best candidates' in the SDSS-based Polar Ring Catalogue. The distributions of line-of-sight velocities of stellar and gaseous components have given kinematic confirmation of polar structures in 13 galaxies in the sample. We show that ionization by young stars dominates in the external parts of polar discs, while shocks have a significant contribution to gas excitation in the inner parts of polar structures. This picture was predicted earlier in a toy model implying the collision between gaseous clouds on polar orbits with the stellar disc gravitational potential well. The exception is a moderately inclined ring to the host galaxy NGC 5014: the accreted gas in the centre has already settled on the main plane and ionized by young stars, while the gas in the internal part of the ring is excited by shocks. The present study three times increases the number of polar structures with an available oxygen abundance estimation. The measured values of the gas metallicity almost do not depend on the galaxy luminosity. The radial [O/H] gradient in the considered polar rings is shallow or absent. No metal-poor gas was detected. We ruled out the scenario of the formation of polar rings due to cold accretion from cosmic filaments for the considered sample of PRGs., Comment: 13 pages, accepted for publication in MNRAS

We present a sample of 17 objects from the CALIFA survey where we find initial evidence of galactic winds based on their off-axis ionization properties. We identify the presence of outflows using various optical diagnostic diagrams (e.g., EW(H$\alpha$), [Nii]/H$\alpha$, [Sii]/H$\alpha$, [Oi]/H$\alpha$ line-ratio maps). We find that all 17 candidate outflow galaxies lie along the sequence of active star formation in the M$_\star$ vs. star-formation rate diagram, without a clear excess in the integrated SFR. The location of galaxies along the star-formation main sequence (SFMS) does not influence strongly the presence or not of outflows. The analysis of the star-formation rate density ($\Sigma_{\rm SFR}$) reveals that the CALIFA sources present higher values when compared with normal star-forming galaxies. The strength of this relation depends on the calibrator used to estimate the SFR. This excess in $\Sigma_{\rm SFR}$ is significant within the first effective radius supporting the idea that most outflows are driven by processes in the inner regions of a galaxy. We find that the molecular gas mass density ($\Sigma_\mathrm{gas}$) is a key parameter that plays an important role in the generation of outflows through its association with the local SFR. The canonical threshold reported for the generation of outflows -- $\Sigma_{\rm SFR}>0.1$ $\mathrm{M}_\odot \mathrm{yr}^{-1} \mathrm{kpc}^{-2}$ -- is only marginally exceeded in our sample. Within the Kennicutt-Schmidt diagram we propose a domain for galaxies hosting starburst-driven outflows defined by $\Sigma_{\rm SFR}>10^{-2} \,\mathrm{M}_\odot \mathrm{yr}^{-1} \mathrm{kpc}^{-2}$ and $\Sigma_\mathrm{gas}>10^{1.2} \, \mathrm{M}_\odot \mathrm{pc}^{-2}$ within a central kiloparcec region., Comment: 25 pages, 16 figues, accepted for publishing in MNRAS

We present the results of observations of the galaxy Holmberg I carried out at the Russian 6-m telescope in the narrow-band imaging, long-slit spectroscopy, and scanning Fabry-Perot interferometer modes. A detailed analysis of gas kinematics, ionization conditions, and metallicity of star-forming regions in the galaxy is presented. The aim of the paper is to analyse the propagation of star formation in the galaxy and to understand the role of the ongoing star formation in the evolution of the central 'galaxy-sized' supergiant HI shell (SGS), where all regions of star formation are observed. We show that star formation in the galaxy occurs in large unified complexes rather than in individual giant HII regions. Evidence of the triggered star formation is observed both on scales of individual complexes and of the whole galaxy. We identified two supernova-remnant candidates and one late-type WN star and analysed their spectrum and surrounding-gas kinematics. We provide arguments indicating that the SGS in Holmberg I is destructing by the influence of star formation occurring on its rims., Comment: Accepted by MNRAS; 25 pages, 16 figures, 5 tables

We consider AGN photoionization of gas in companion galaxies (cross-ionization) as a way to sample the intensity of AGN radiation in both direction and time, independent of the gas properties of the AGN host galaxies. From an initial set of 212 AGN+companion systems, identified with the help of Galaxy Zoo participants, we obtained long-slit optical spectra of 32 pairs which were a priori likely to show cross-ionization based on projected separation or angular extent of the companion. From emission-line ratios, 10 of these systems are candidates for cross-ionization, roughly the fraction expected if most AGN have ionization cones with 70-degree opening angles. Among these, Was 49 remains the strongest nearby candidate. NGC 5278/9 and UGC 6081 are dual-AGN systems with tidal debris, complicating identification of cross-ionization. The two weak AGN in the NGC 5278/9 system ionize gas filaments to a projected radius 14 kpc from each galaxy. In UGC 6081, an irregular high-ionization emission region encompasses both AGN, extending more than 15 kpc from each. The observed AGN companion galaxies with and without signs of external AGN photoionization have similar distributions in estimated incident AGN flux, suggesting that geometry of escaping radiation or long-term variability control this facet of the AGN environment. This parallels conclusions for luminous QSOs based on the proximity effect among Lyman-alpha absorbers. In some galaxies, mismatch between spectroscopic classifications in the common BPT diagram and the intensity of weaker He II and [Ne V] emission lines highlights the limits of common classifications in low-metallicity environments., Comment: Accepted version to appear in MNRAS. New version has spectra showing AGN ionization in NGC 5278/9 filaments and tunable-filter mapping of clouds around UGC 6081 system

We describe a device (adapter) for off-axis guiding and photometric calibration of wide-angle spectrographs operating in the prime focus of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. To compensate coma in off-axis star images an achromatic lens corrector is used, which ensures maintaining image quality (FWHM) at a level of about 1'' within 15' from the optical axis. The device has two 54'-diameter movable guiding fields, which can move in 10' x 4'.5 rectangular areas. The device can perform automatic search for guiding stars, use them to control the variations of atmospheric transmittance, and focus the telescope during exposure. The limiting magnitude of potential guiding stars is mR ~17 mag. The calibration path whose optical arrangement meets the telecentrism condition allows the spectrograph to be illuminated both by a source of line spectrum (a He-Ne-Ar filled lamp) and by a source of continuum spectrum. The latter is usually represented either by a halogen lamp or a set of light-emitting diodes, which provide illumination of approximately uniform intensity over the wavelength interval from 350 to 900 nm. The adapter is used for observations with SCORPIO-2 multimode focal reducer., Comment: Accepted to Astrophysical Bulletin. 11 pages, 11 figures, 1 table

We analyse the structure and kinematics of ionized gas in the vicinity of the ultraluminous X-ray source (ULX) HoII X-1 in the Holmberg II galaxy using observational data obtained with a scanning Fabry-Perot interferometer in the H$\alpha$, [SII] and [OIII] emission lines at the Russian 6-m telescope. Decomposition of the line profiles allows us to identify the broad component of emission lines caused by the ULX action. We found evidence of an expanding superbubble around the young star cluster located in the studied region. We conclude that the blue-shifted 'arc' around the ULX observed in the line-of-sight velocity field may correspond to a bow shock caused by the ULX movement from that nearby young star cluster. If this interpretation is correct, it will be the first kinematic evidence of ULX's escape from their parent star clusters., Comment: 5 pages, 3 figures, submitted to MNRAS Letters after second revision

We report a detailed analysis of all regions of current star formation in the walls of the supergiant HI shell (SGS) in the galaxy Holmberg II based on observations with a scanning Fabry-Perot interferometer at the 6-m SAO RAS telescope. We compare the structure and kinematics of ionized gas with that of atomic hydrogen and with the stellar population of the SGS. Our deep H$\alpha$ images and archival images taken by the HST demonstrate that current star formation episodes are larger and more complicated than previously thought: they represent unified star-forming complexes with sizes of several hundred pc rather than 'chains' of separate bright nebulae in the walls of the SGS. The fact that we are dealing with unified complexes is evidenced by identified faint shell-like structures of ionized and neutral gas which connect several distinct bright HII regions. Formation of such complexes is due to the feedback of stars with very inhomogeneous ambient gas in the walls of the SGS. The arguments supporting an idea about the triggering of star formation in SGS by the HI supershells collision are presented. We also found a faint ionized supershell inside the HI SGS expanding with a velocity of no greater than 10-15 km/s. Five OB stars located inside the inner supershell are sufficient to account for its radiation, although a possibility of leakage of ionizing photons from bright HII regions is not ruled out as well., Comment: 23 pages, 14 figures, 4 tables. Accepted for publication in MNRAS

In this paper, we present results of a photometric and kinematic study for a sample of 13 edge-on spiral galaxies with pronounced integral-shape warps of their stellar discs. The global structure of the galaxies is analyzed on the basis of the Sloan Digital Sky Survey (SDSS) imaging, in the g, r and i passbands. Spectroscopic observations are obtained with the 6-m Special Astrophysical Observatory telescope. In general, galaxies of the sample are typical bright spiral galaxies satisfying the Tully-Fisher relation. Most of the galaxies reside in dense spatial environments and, therefore, tidal encounters are the most probable mechanism for generating their stellar warps. We carried out a detailed analysis of the galaxies and their warps and obtained the following main results: (i) maximum angles of stellar warps in our sample are about 20{\deg}; (ii) warps start, on average, between 2 and 3 exponential scale lengths of a disc; (iii) stronger warps start closer to the center, weak warps start farther; (iv) warps are asymmetric, with the typical degree of asymmetry of about several degrees (warp angle); (v) massive dark halo is likely to preclude the formation of strong and asymmetric warps., Comment: 15 pages, 8 figures, accepted for publication in MNRAS

We present the first results of our search for transiting exoplanet candidates as part of the Kourovka Planet Search (KPS) project. The primary objective of the project is to search for new hot Jupiters which transit their host stars, mainly in the Galactic plane, in the $R_c$ magnitude range of 11 to 14 mag. Our observations were performed with the telescope of the MASTER robotic network, installed at the Kourovka astronomical observatory of the Ural Federal University (Russia), and the Rowe-Ackermann Schmidt Astrograph, installed at the private Acton Sky Portal Observatory (USA). As test observations, we observed three celestial fields of size $2\times2$ deg$^2$ during the period from 2012 to 2015. As a result, we discovered four transiting exoplanet candidates among the 39000 stars of the input catalogue. In this paper, we provide the description of the project and analyse additional photometric, spectral, and speckle interferometric observations of the discovered transiting exoplanet candidates. Three of the four transiting exoplanet candidates are most likely astrophysical false positives, while the nature of the fourth (most promising) candidate remains to be ascertained. Also, we propose an alternative observing strategy that could increase the project's exoplanet haul., Comment: 11 pages, 16 figures; Accepted for publication in Monthly Notices of the Royal Astronomical Society 2016

NGC 6946, known as the Fireworks galaxy because of its high supernova rate and high star formation, is embedded in a very extended HI halo. Its northern spiral arm is well detached from the galactic main body. We found that this arm contains a large (~300 pc in size) Red Ellipse, named according to a strong contamination of the H-alpha emission line on its optical images. The ellipse is accompanied by a short parallel arc and a few others still smaller and less regular; a bright star cluster is seen inside these features. The complicated combination of arcs seems to be unique, it is only a bit similar to some SNRs. However, the long-slit spectral data obtained with the Russian 6-m telescope did not confirm the origin of the nebula as a result of a single SN outburst. The emission-line spectrum corresponds to the photoionization by young hot stars with a small contribution of shock ionization. The most likely explanation of the Red Ellipse is a superbbuble created by a collective feedback of massive stars in the star cluster located in the NE side of the Red Ellipse. However, the very regular elliptical shape of the nebulae seems strange., Comment: 8 pages, 6 figures. Submitted to MNRAS after revision. Comments welcome

Using 3D numerical simulations we study the evolution of the H$\alpha$ intensity and velocity dispersion for single and multiple supenova (SN) explosions. We find that the $I_{\rm H\alpha}-\sigma$ diagram obtained for simulated gas flows is similar in shape to that observed in dwarf galaxies. We conclude that colliding SN shells with significant difference in age are resposible for high velocity dispersion that reaches values high as $\simgt 100$kms$^{-1}$. Such a high velocity dispersion could be hardly got for a single SN remnant. Peaks of velocity dispersion on the $I_{\rm H\alpha}-\sigma$ diagram may correspond to several stand-alone or merged SN remnants with moderately different ages. The procedure of the spatial resolution degrading in the H$\alpha$ intensity and velocity dispersion maps makes the simulated $I_{\rm H\alpha}-\sigma$ diagrams close to those observed in dwarf galaxies not only in shape, but also quantitatively., Comment: 7 pages, 5 figures, submitted to Baltic Astronomy

Using 3D spectroscopy with a scanning Fabry-Perot interferometer, we study the ionized gas kinematics in 59 nearby dwarf galaxies. Combining our results with data from literature, we provide a global relation between the gas velocity dispersion (sigma) and the star formation rate (SFR) and H\alpha luminosity for galaxies in a very broad range of star formation rates SFR=0.001-300 Msun/yr. We find that the SFR-sigma relation for the combined sample of dwarf galaxies, star forming, local luminous, and ultra-luminous infrared galaxies can be fitted as sigma~ SFR^(5.3+-0.2). This implies that the slope of the L-sigma relation inferred from the sample of rotation supported disc galaxies (including mergers) is similar to the L-sigma relation of individual giant HII regions. We present arguments that the velocity dispersion of the ionized gas does not reflect the virial motions in the gravitational potential of dwarf galaxies, and instead is mainly determined by the energy injected into the interstellar medium by the ongoing star formation., Comment: 15 pages, major revision of the previous version, accepted to MNRAS

We review our current knowledge about a particular case of decoupled gas kinematics -- inner ionized-gas polar disks. Though more difficult to be noticed, they seem to be more numerous than their large-scale counterparts; our recent estimates imply about 10 per cent of early-type disk galaxies to be hosts of inner polar disks. Since in the most cases the kinematics of the inner polar gaseous disks is decoupled from the kinematics of the outer large-scale gaseous disks and since they nested around very old stellar nuclei, we speculate that the inner polar disks may be relics of very early events of external gas accretion several Gyr ago. Such view is in agreement with our new paradigm of the disk galaxies evolution., Comment: 8 pages, 3 figures, to be published in the proceedings of the conference "Multi-Spin Galaxies" held in Napoli in October 2013

We used deep long-slit spectra and integral-field spectral data to study the stars and ionized gas kinematics and stellar population properties in the lenticular barred galaxy NGC 7743. We have shown that ionized gas at the distances larger than 1.5 kpc from the nucleus settles in the disk which is significantly inclined to the stellar disk of the galaxy. Making different assumptions about the geometry of the disks and involving different sets of emission lines into the fitting, under the assumption of thin flat disk circular rotation, we obtain the full possible range of angle between the disks to be 34+/-9 or 77+/-9 deg. The most probable origin of the inclined disk is the external gas accretion from a satellite, orbiting the host galaxy with a corresponding angular momentum direction. The published data on the HI distribution around NGC 7743 suggest that the galaxy has a gas-rich environment. The emission-line ratio diagrams imply the domination of shock waves in the ionization state of the gaseous disk, whereas the contribution of photoionization by recent star formation seems to be negligible. In some parts of the disk a difference between the velocities of the gas emitting in the forbidden lines and in the Balmer lines is detected. It may be caused by the fact that the inclined disk is mainly shock-excited, whereas some fraction of the Balmer-line emission is produced by a small amount of gas excited by young stars in the main stellar disk of NGC 7743. In the circumnuclear region (R< 200 pc) some evidences of the AGN jet interaction with an ambient interstellar medium were found., Comment: 11 pages, 7 figures, accepted by Astrophysical Journal

BV-bands photometric data obtained at the 6-m telescope of the Special Astrophysical Observatory are used to analyze the structure of 13 large disk galaxies in the NGC 80 group. Nine of the 13 galaxies under consideration are classified by us as lenticular galaxies. The stellar populations in the galaxies are very different, from old ones with ages of T>10 Gyrs (IC 1541) to relatively young, with the ages of T<2-3 Gyr (IC 1548, NGC 85). In one case, current star formation is known (UCM 0018+2216). In most of the galaxies, more precisely in all of them more luminous than M(B) -18, two-tiered (`antitruncated') stellar disks are detected, whose radial surface brightness profiles can be fitted by two exponential segments with different scalelengths -- shorter near the center and longer at the periphery. All dwarf S0 galaxies with single-scalelength exponential disks are close companions to giant galaxies. Except for this fact, no dependence of the properties of S0 galaxies on distance from the center of the group is found. Morphological traces of minor merger are found in the lenticular galaxy NGC 85. Basing on the last two points, we conclude that the most probable mechanisms for the transformation of spirals into lenticular galaxies in groups are gravitational ones, namely, minor mergers and tidal interactions., Comment: 24 pages, 9 figures, slightly improved version of the paper published in the December, 2009, issue of the Astronomy Reports

Here we present the analysis of 3D spectroscopic data of three Blue Compact Galaxies (Mrk324, Mrk370, and IIIZw102). Each of the more than 22500 spectra obtained for each galaxy has been fitted by a single gaussian from which we have inferred the velocity dispersion (sigma), the peak intensity (Ipeak), and the central wavelength (lambda_c). The analysis shows that the sigma vs Ipeak diagrams look remarkably similar to those obtained for giant extragalactic HII regions. They all present a supersonic narrow horizontal band that extends across all the range of intensities and that result from the massive nuclear star-forming regions of every galaxy. The sigma vs Ipeak diagrams present also several inclined bands of lower intensity and an even larger sigma, arising from the large galactic volumes that surround the main central emitting knots. Here we also show that the sigma vs lambda_c and lambda_c vs Ipeak diagrams, are powerful tools able to unveil the presence of high and low mass stellar clusters, and thus allow for the possibility of inferring the star formation activity of distant galaxies, even if these are not spatially resolved., Comment: 15 pages, 3 figures, accepted for publication in The Astronomical Journal