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The Orion Molecular Cloud complex, one of the nearest (D = 406 pc) and most extensively studied massive star-forming regions, is ideal for constraining the physics of stellar feedback, but its ~12 deg diameter on the sky requires a dedicated approach to mapping ionized gas structures within and around the nebula. The Sloan Digital Sky Survey (SDSS-V) Local Volume Mapper (LVM) is a new optical integral field unit (IFU) that will map the ionized gas within the Milky Way and Local Group galaxies, covering 4300 deg^2 of the sky with the new LVM Instrument. We showcase optical emission line maps from LVM covering 12 deg^2 inside of the Orion belt region, with 195,000 individual spectra combined to produce images at 0.07 pc (35.3") resolution. This is the largest IFU map made (to date) of the Milky Way, and contains well-known nebulae (the Horsehead Nebula, Flame Nebula, IC 434, and IC 432), as well as ionized interfaces with the neighboring dense Orion B molecular cloud. We resolve the ionization structure of each nebula, and map the increase in both the [SII]/Ha and [NII]/Ha line ratios at the outskirts of nebulae and along the ionization front with Orion B. [OIII] line emission is only spatially resolved within the center of the Flame Nebula and IC 434, and our ~0.1 pc scale line ratio diagrams show how variations in these diagnostics are lost as we move from the resolved to the integrated view of each nebula. We detect ionized gas emission associated with the dusty bow wave driven ahead of the star sigma Orionis, where the stellar wind interacts with the ambient interstellar medium. The Horsehead Nebula is seen as a dark occlusion of the bright surrounding photo-disassociation region. This small glimpse into Orion only hints at the rich science that will be enabled by the LVM., Comment: 13 pages, 10 figures, accepted for publication in A&A

We present the results of a study of young unresolved stellar groupings (clusters, OB associations, and their complexes) associated with HII regions, based on the coupling of spectroscopic, photometric and H{\alpha} spectrophotometric observations of star formation regions. Along with our own observations, we use a part of the spectroscopic and H{\alpha} data from the literature and open databases. The study is based on the catalogue of 1510 star formation regions with ages ~10-20 Myr in 19 spiral galaxies, compiled by us earlier. We study the morphology of stellar groupings and their relation with the associated H{\alpha} emission region. Extinctions, gas chemical abundances, and sizes of star formation regions are measured. Using numerical SSP models computed for metallicities fixed from observations to intrinsic colours of the studied star formation regions, we estimated ages and masses of stellar population of 400 young stellar groupings. Different relations between observational and physical parameters of the young stellar population in star formation regions are discussed., Comment: 19 pages, 20 figures, 1 table, 1 online table. Accepted for publication in MNRAS

We present a first study based on the analysis of the DEep Spectra of Ionized REgions Database (DESIRED). This is a compilation of 190 high signal-to-noise ratio optical spectra of HII regions and other photoionized nebulae, mostly observed with 8-10m telescopes and containing $\sim$29380 emission lines. We find that the electron density --$n_{\rm e}$-- of the objects is underestimated when [SII] $\lambda6731/\lambda6716$ and/or [OII] $\lambda3726/\lambda3729$ are the only density indicators available. This is produced by the non-linear density dependence of the indicators in the presence of density inhomogeneities. The average underestimate is $\sim 300$ cm$^{-3}$ in extragalactic HII regions, introducing systematic overestimates of $T_{\rm e}$([OII]) and $T_{\rm e}$([SII]) compared to $T_{\rm e}$([NII]). The high-sensitivity of [OII] $\lambda\lambda7319+20+30+31/\lambda\lambda3726+29$ and [SII] $\lambda\lambda4069+76/\lambda\lambda6716+31$ to density makes them more suitable for the diagnosis of the presence of high-density clumps. If $T_{\rm e}$([NII]) is adopted, the density underestimate has a small impact in the ionic abundances derived from optical spectra, being limited to up to $\sim$0.1 dex when auroral [SII] and/or [OII] lines are used. However, these density effects are critical for the analysis of infrared fine structure lines, such as those observed by the JWST in local star forming regions, implying strong underestimates of the ionic abundances. We present temperature relations between $T_{\rm e}$([OIII]), $T_{\rm e}$([ArIII]), $T_{\rm e}$([SIII]) and $T_{\rm e}$([NII]) for the extragalactic HII regions. We confirm a non-linear dependence between $T_{\rm e}$([OIII])-$T_{\rm e}$([NII]) due to a more rapid increase of $T_{\rm e}$([OIII]) at lower metallicities., Comment: Accepted for publication in MNRAS

Star formation and stellar feedback are interlinked processes that redistribute energy and matter throughout galaxies. When young, massive stars form in spatially clustered environments, they create pockets of expanding gas termed superbubbles. As these processes play a critical role in shaping galaxy discs and regulating the baryon cycle, measuring the properties of superbubbles provides important input for galaxy evolution models. With wide coverage and high angular resolution (50-150 pc) of the PHANGS-ALMA $^{12}$CO (2-1) survey, we can now resolve and identify a statistically representative number of superbubbles with molecular gas in nearby galaxies. We identify superbubbles by requiring spatial correspondence between shells in CO with stellar populations identified in PHANGS-HST, and combine the properties of the stellar populations with CO to constrain feedback models and quantify their energetics. We visually identify 325 cavities across 18 PHANGS-ALMA galaxies, 88 of which have clear superbubble signatures (unbroken shells, central clusters, kinematic signatures of expansion). We measure their radii and expansion velocities using CO to dynamically derive their ages and the mechanical power driving the bubbles, which we use to compute the expected properties of the parent stellar populations driving the bubbles. We find consistency between the predicted and derived stellar ages and masses of the stellar populations if we use a supernova blast wave model that injects energy with a coupling efficiency of 10%, whereas continuous models fail to explain stellar ages we measure. Not only does this confirm molecular gas accurately traces superbubble properties, but it also provides key observational constraints for superbubble models. We also find evidence that the bubbles sweep up gas as they expand and speculate that these sites have the potential to host new generations of stars., Comment: 21 pages, 15 figures, 3 tables. Accepted to A&A. Abstract abridged for arXiv

Ionized nebulae provide critical insights into the conditions of the interstellar medium (ISM). Their bright emission lines enable the measurement of physical properties, such as the gas-phase metallicity, across galaxy disks and in distant galaxies. The PHANGS--MUSE survey has produced optical spectroscopic coverage of the central star-forming discs of 19 nearby main-sequence galaxies. Here, we use the H{\alpha} morphology from this data to identify 30,790 distinct nebulae, finding thousands of nebulae per galaxy. For each nebula, we extract emission line fluxes and, using diagnostic line ratios, identify the dominant excitation mechanism. A total of 23,244 nebulae (75%) are classified as HII regions. The dust attenuation of every nebulae is characterised via the Balmer decrement and we use existing environmental masks to identify their large scale galactic environment (centre, bar, arm, interarm and disc). Using strong-line prescriptions, we measure the gas-phase oxygen abundances (metallicity) and ionization parameter for all HII regions. With this new catalogue, we measure the radial metallicity gradients and explore second order metallicity variations within each galaxy. By quantifying the global scatter in metallicity per galaxy, we find a weak negative correlation with global star formation rate and stronger negative correlation with global gas velocity dispersion (in both ionized and molecular gas). With this paper we release the full catalogue of strong line fluxes and derived properties, providing a rich database for a broad variety of ISM studies., Comment: 27 pages, accepted by MNRAS

One of the fundamental factors regulating the evolution of galaxies is stellar feedback. However, we still do not have strong observational constraints on the relative importance of the different feedback mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving HII region evolution and molecular cloud disruption. In this letter, we constrain the relative importance of the various feedback mechanisms from young massive star populations by resolving HII regions across the disk of the nearby star-forming galaxy NGC 1672. We combine measurements of ionised gas nebular lines obtained by PHANGS-MUSE, with high-resolution imaging from the HST in both the narrow-band H{\alpha} and broad-band filters. We identify a sample of 40 isolated, compact HII regions in the HST H{\alpha} image, for which we measure the sizes that were previously unresolved in seeing-limited ground-based observations. Additionally, we identify the ionisation source(s) for each HII region from catalogues produced as part of the PHANGS-HST survey. We find that the HII regions investigated are mildly dominated by thermal or wind pressure, yet their elevation above the radiation pressure is within the expected uncertainty range. We see that radiation pressure provides a substantially higher contribution to the total pressure than previously found in the literature over similar size scales. In general, we find higher pressures within more compact HII regions, which is driven by the inherent size scaling relations of each pressure term, albeit with significant scatter introduced by the variation in the stellar population properties (e.g. luminosity, mass, age, metallicity). For nearby galaxies, here we provide a promising approach that could yield the statistics required to map out how the importance of different stellar feedback mechanisms evolve over the lifetime of an HII region., Comment: 5(+4) pages, 6 figures, 1 table (available online), accepted for publication in A&A Letters

The low-mass low-surface brightness (LSB) disc galaxy Arakelian 18 (Ark 18) resides in the Eridanus void and because of its isolation represents an ideal case to study the formation and evolution mechanisms of such a galaxy type. Its complex structure consists of an extended blue LSB disc and a bright central elliptically-shaped part hosting a massive off-centered star-forming clump. We present the in-depth study of Ark 18 based on observations with the SCORPIO-2 long-slit spectrograph and a scanning Fabry-Perot interferometer at the Russian 6-m telescope complemented by archival multi-wavelength images and SDSS spectra. Ark 18 appears to be a dark matter dominated gas-rich galaxy without a radial metallicity gradient. The observed velocity field of the ionised gas is well described by two circularly rotating components moderately inclined with respect to each other and a possible warp in the outer disc. We estimated the age of young stellar population in the galaxy centre to be ~140 Myr, while the brightest star-forming clump appears to be much younger. We conclude that the LSB disc is likely the result of a dwarf-dwarf merger with a stellar mass ratio of the components at least ~5:1 that occurred earlier than 300 Myr ago. The brightest star forming clump was likely formed later by accretion of a gas cloud., Comment: 19 pages, 13 figures, 5 tables. Submitted to MNRAS after minor revision, comments are welcome

The nearby dwarf galaxy NGC 3077 is known for its peculiar morphology, which includes numerous dust lanes and emission-line regions. The interstellar medium in this galaxy is subject to several perturbing factors. These are primarily the central starburst and tidal structures in the M 81 group. We present a comprehensive study of the state of ionization, kinematics, and chemical composition of ionized gas in NGC 3077, including both star-forming regions and diffuse ionized gas (DIG) at the periphery. We study gas motions in the H$\alpha$ line via high-resolution ($R\approx15\,000$) 3D spectroscopy with the scanning Fabry-Perot interferometer installed into SCORPIO-2 instrument attached to the 6-m telescope of the SAO RAS. Images in the main optical emission lines were acquired with MaNGaL photometer with a tunable filter at the 2.5-m telescope of the Caucasian Mountain Observatory of SAI MSU. We also used SCORPIO-2 to perform long-slit spectroscopy of the galaxy with a resolution of $R\approx1\,000$. Our estimate of the gas metallicity, $Z=0.6Z_\odot$, is significantly lower than the earlier determination, but agrees with the "luminosity--metallicity" dependence. Spatially resolved diagnostic diagrams of the emission-line ratios do not show correlations between the gas ionization state and its velocity dispersion, and this is most likely due to strong ionization by young stars, whereas the contribution of shocks to the excitation of emission lines is less important. We also studied the locations of multicomponent H$\alpha$ profiles and provide arguments suggesting that they are mostly associated with individual kinematic components along the line of sight and not with expanding shells as it was believed earlier. We also observe there a combination of wind outflow from star-forming regions and accretion from interstellar gas clouds in the M 81 group., Comment: 14 pages, 6 figures

Two star-forming regions are studied: the young embedded open cluster vdB 130 and the protocluster neighbourhood observed in the head and tail of the cometary molecular cloud located in the wall of the expanding supershell surrounding the Cyg OB1 association. The GAIA DR2 catalogue is employed to verify the stellar composition of the vdB 130 cluster whose members were earlier selected using the UCAC4 catalogue. The new sample of vdB 130 members contains 68 stars with close proper motions (within 1 mas yr$^{-1}$) and close trigonometric parallaxes (ranging from 0.50 to 0.70 mas). The relative parallax error is shown to increase with distance to objects and depend on their magnitude. At a distance of 1.5-2 kpc it is of about 3-7 per cent and 20-30 per cent for bright and faint stars, respectively. The cluster is not older than ~10 Myr. New spectroscopic and photometric observations carried out on Russian telescopes are combined with GAIA DR2 to search for optical components in the protocluster region - a new starburst. An analysis of 20 stars in the vicinity of the protocluster revealed no concentration of either proper motions or parallaxes. According to spectroscopic, photometric, and trigonometric estimates, the distances to these stars range from 0.4 to 2.5 kpc, and colour excess is shown to increase with a distance D (kpc) in accordance with the law: $E(B-V)\simeq 0.6\times D$ mag., Comment: 14 pages, 11 figures, 5 tables; accepted for publication in MNRAS

In this paper we present new optical observations of the galaxy NGC 185 intended to reveal the status of supernova remnants (SNRs) in this dwarf companion of the Andromeda galaxy. Previously, it was reported that this galaxy hosts one SNR. Our deep photometric study with the 2m telescope at Rozhen National Astronomical Observatory using narrow-band H$\alpha$ and [SII] filters revealed complex structure of the interstellar medium in the center of the galaxy. To confirm the classification and to study the kinematics of the detected nebulae, we carried out spectroscopic observations using the SCORPIO multi-mode spectrograph at the 6m telescope at the Special Astrophysical Observatory of the Russian Academy of Science, both in low- and high-resolution modes. We also searched the archival X-ray and radio data for counterparts of the candidate SNRs identified by our optical observations. Our observations imply the presence of one more SNR, one possible HII region previously cataloged as part of an SNR, and the presence of an additional source of shock ionization in one low-brightness PN. We detected enhanced [SII]/H_alpha and [NII]/H_alpha line ratios, as well as relatively high (up to 90 km s$^{-1}$) expansion velocities of the two observed nebulae, motivating their classification as SNRs (with diameters of 45 pc and 50 pc), confirmed by both photometric and spectral observations. The estimated electron density of emission nebulae is 30 - 200 cm$^{-3}$. Archival XMM-Newton observations indicate the presence of an extended, low-brightness, soft source in projection of one of the optical SNRs, whereas the archival VLA radio image shows weak, unresolved emission in the center of NGC 185., Comment: 15 pages, 14 figures, accepted for publication in A&A

We present an observational study of small-scale feedback processes operating in the star-forming region located in the wall of the expanding supershell around the Cyg OB1 association. The interstellar gas and dust content and pre-stellar populations in the vicinity of the open star cluster vdB 130 are analysed based on new optical and IR observations performed with the 6-m (3D spectroscopic mapping in the [SII] doublet) and 2.5-m (optical and NIR images) Russian telescopes along with the archival data of Spitzer and Herschel space telescopes. Analysing ionized gas kinematics and emission spectra, we discovered a compact region with supersonic motions. These motions may be caused either by stellar wind, or a bipolar outflow from a protostellar disc. Young stellar objects were identified and classified in the area under study. Two star-forming regions were identified. One of them is a region of ongoing star formation in the head of the molecular cloud observed there and another one is a burst of star formation in the cloud tail., Comment: accepted for publication in MNRAS; 15 pages, 14 figures, 1 table

We present the first results of a project aimed at searching for gas accretion events and interactions between late-type galaxies in the void environment. The project is based on long-slit spectroscopic and scanning Fabry-Perot interferometer observations performed with the SCORPIO and SCORPIO-2 multimode instruments at the Russian 6-m telescope, as well as archival multiwavelength photometric data. In the first paper of the series we describe the project and present a sample of 18 void galaxies with oxygen abundances that fall below the reference `metallicity-luminosity' relation, or with possible signs of recent external accretion in their optical morphology. To demonstrate our approach, we considered the brightest sample galaxy NGC 428, a late-type barred spiral with several morphological peculiarities. We analysed the radial metallicity distribution, the ionized gas line-of-sight velocity and velocity dispersion maps together with WISE and SDSS images. Despite its very perturbed morphology, the velocity field of ionized gas in NGC 428 is well described by pure circular rotation in a thin flat disc with streaming motions in the central bar. We also found some local non-circular gas motions clearly related to stellar feedback processes. At the same time, we revealed a circumnuclear inclined disc in NGC 428 and a region with significant residual velocities that could be considered as a result of a recent (<0.5 Gyr) accretion event. The observed oxygen abundance gradient does not contradict this conclusion., Comment: Accepted for publication in MNRAS; 13 pages, 10 figures, 4 tables

We describe the scheme and design features of the new IFU unit (Integral Field Unit) meant to perform integral-field spectroscopy as a part of SCORPIO-2 focal reducer, which is mounted in the prime focus of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The design of the unit is based on the principle of the formation of array spectra using a lens raster combined with optical fibers. The unit uses a rectangular raster consisting of 22x22 square 2-mm diameter lenses. The image of the object is transferred by an optical system with a 23x magnification from the focal plane of the telescope to the plane of the lens raster. The image scale is 0.75"/lens and the field of view of the instrument has the size of 16.5"x16.5". The raster also contains two extra 2x7 lens arrays to acquire the night-sky spectra whose images are offset by $\pm$3' from the center. Optical fibers are used to transform micropupil images into two pseudoslits located at the IFU collimator entrance. When operating in the IFU mode a set of volume phase holographic gratings (VPHG) provides a spectral range of 4600-7300 \AA\ and a resolution $\lambda/\delta\lambda$ of 1040 to 2800. The quantum efficiency of SCORPIO-2 field spectroscopy is 6-13% depending on the grating employed. We describe the technique of data acquisition and reduction using IFU unit and report the results of test observations of the Seyfert galaxy Mrk 78 performed on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences., Comment: 17 pages, 14 figures, 1 table; accepted for publication in Astrophysical Bulletin, vol. 73 (3)

On the basis of the SDSS survey and spectral observations with the 6-m telescope of SAO RAS, we have peformed a detailed study of SDSS J170745+302056. By combination of its characteristics -- exponential surface brightness distribution, central surface brightness of stellar disk $\mu_0(B) = 23.25\,^m/\square"$, blue colors, low metallicity and low star formation rate -- the galaxy is a typical low surface brightness spiral galaxy. Exponential scalelength of the galaxy is $\approx$3 kpc, its optical diameter exceeds 20 kpc. SDSS J170745+302056 is a member of a group of five galaxies and probably it is in interaction with UGC 10716. The existence of a large low surface brightness galaxy in such a dense environment is very unusual., Comment: 8 pages, 4 figures

We considered the regions of triggered star formation inside kpc-sized HI supershells in three dwarf galaxies: IC 1613, IC 2574 and Holmberg II. The ionized and neutral gas morphology and kinematics were studied based on our observations with scanning Fabry-Perot interferometer at the SAO RAS 6-m telescope and 21 cm archival data of THINGS and LITTLE THINGS surveys. The qualitative analysis of the observational data performed in order to highlight the two questions: why the star formation occurred very locally in the supershells, and how the ongoing star formation in HI supershells rims influence its evolution? During the investigation we discovered the phenomenon never observed before in galaxies IC 2574 and Holmberg II: we found faint giant (kpc-sized) ionized shells in H-alpha and [SII]6717,6731 lines inside the supergiant HI shells., Comment: Published in proceedings of the conference "Galaxies" (Essentuki, Russia, November 24-28, 2014). 9 pages, 4 figures

Stellar population and the interstellar gas-dust medium in the vicinity of the open star cluster vdB 130 are analysed using optical observations taken with the 6-m telescope of the SAO RAS and the 125-cm telescope of the SAI MSU along with the data of Spitzer and Herschel. Based on proper motions and BV and JHKs 2MASS photometric data, we select additional 36 stars as probable cluster members. Some stars in vdB 130 are classified as B stars. Our estimates of minimum colour excess, apparent distance modulus and the distance are consistent with young age (from 5 to 10 Myrs) of the cluster vdB 130. We suppose the large deviations from the conventional extinction law in the cluster direction, with $R_V$ ~ 4 - 5. The cluster vdB 130 appears to be physically related to the supershell around Cyg OB1, a cometary CO cloud, ionized gas, and regions of infrared emission. There are a few regions of bright mid-infrared emission in the vicinity of vdB 130. The largest of them is also visible on H-alpha and [SII] emission maps. We suggest that the infrared blobs that coincide in projection with the head of the molecular cloud are HII regions, excited by the cluster B-stars. Some signatures of a shock front are identified between these IR-bright regions., Comment: 17 pages, 14 figures, 2 tables. Accepted by MNRAS

We present an analysis of optical spectroscopy and infrared aperture photometry of more than 100 H II complexes in nine galaxies. Spectra obtained with the 6-m telescope of SAO RAS are used along with archival data from Spitzer and several ground-based telescopes to infer a strength of polycyclic aromatic hydrocarbon (PAH) emission, age, properties of the UV radiation field, and metallicity of studied H II complexes. Physical properties (age, radiation field parameters, metallicity) are related to the $F_{8}/F_{24}$ ratio used as a proxy for the PAH abundance in order to reveal factors that may influence the PAH evolution in H II complexes. The well-known correlation between the $F_{8}/F_{24}$ ratio and metallicity is confirmed in the studied complexes. The infrared flux ratio also correlates with the [O III]$\lambda 5007/\mathrm{H\beta}$ ratio which is often considered as an indicator of the radiation field hardness, but this correlation seems to be a mere reflection of a correlation between [O III]$\lambda 5007/\mathrm{H\beta}$ and metallicity. In separate metallicity bins, the $F_{8}/F_{24}$ ratio is found to correlate with an age of an H II complex, which is estimated from the equivalent width of $\mathrm{H}\beta$ line. The correlation is positive for low metallicity complexes and negative for high metallicity complexes. Analysing various mechanisms of PAH formation and destruction in the context of found correlations, we suggest that PAH abundance is likely altered by the UV radiation within H II complexes, but this is not necessarily due to their destruction. If PAHs can also form in H II complexes due to some processes like aromatisation, photodestruction, shattering and sputtering of very small grains, the net $F_{8}/F_{24}$ ratio is determined by a balance between all these processes that can be different at different metallicities., Comment: Accepted to MNRAS

A detailed photometric study of star-forming regions (SFRs) in the galaxy Holmberg II has been carried out using archival observational data from the far infrared to ultraviolet obtained with the GALEX, Spitzer, and Herschel telescopes. Spectroscopic observations with the 6-m telescope of Special Astrophysical Observatory of the Russian Academy of Sciences are used to estimate ages and metallicities of SFRs. For the first time, the ages of SFRs have been related to their emission parameters in a wide spectral range and with the physical parameters determined by fitting the observed spectra. It is shown that fluxes at 8 and 24 micron characterizing the emission of polycyclic aromatic hydrocarbons (PAHs) and hot dust grains decrease with age, but their ratio increases. This implies that the relative PAH contribution to the total infrared flux increases with age. It is suggested that the detected increase in the ratio of the fluxes at 8 and 24 micron is related to the growth in the PAH mass due to destruction of larger grains., Comment: 15 pages, 8 figures, 3 tables. Published in Astronomy Letters

We analyse the ionized gas kinematics in the star formation regions of the supergiant shell (SGS) of the IC 2574 galaxy using observations with the Fabry-Perot interferometer at the 6-m telescope of SAO RAS; the data of the THINGS survey are used to analyze the neutral gas kinematics in the area. We perform the 'derotation' of the H-alpha and HI data cubes and show its efficiency in kinematics analysis. We confirm the SGS expansion velocity 25 km/s obtained by Walter & Brinks (1999) and conclude that the SGS is located at the far side of the galactic disc plane. We determine the expansion velocities, kinematic ages, and the required mechanical energy input rates for four star formation complexes in the walls of the SGS; for the remaining ones we give the limiting values of the above parameters. A comparison with the age and energy input of the complexes' stellar population shows that sufficient energy is fed to all HII regions except one. We discuss in detail the possible nature of this region and that of another one, which was believed to be an SNR according to radio observations. We measured the expansion velocity of the latter and confirm its identification as an old SNR. Our observations allowed us to identify a faint diffuse H-alpha emission inside the SGS which was never observed before., Comment: 17 pages, 17 figures, 2 tables. Accepted for publication in MNRAS

The interstellar medium in the region of a family of cometary globules including the reflection nebula GM 2-39 has been analyzed basing on our observations with the slit spectrograph, the results of our previous observations with a Fabry-Perot interferometer in the H-alpha line, Spitzer archival data together with CO microwave data. The structure of globules' IR emission, velocity field of ionized gas in the H-alpha line and of molecular gas in the CO line have been considered. We have detected a CO cavern around the eastern globules and faint high-velocity H-alpha features of surrounding gas. The most probable sources of ionizing radiation and wind of the Cyg OB1 association responsible for the globules' formation are proposed. Based on our multicolour photometry, it has been found that the brightest compact source in the southern 'head' of the cometary globule - the star HBHA 3703-01 (IRAS 20153+3850) - is a B(5-6)V star with E(B-V)=1.18 mag. The strong and broad H-alpha emission line was revealed in its spectrum. The spectral energy distribution of HBHA 3703-01 in the 0.44-24 micron range has been modeled. It is shown that the star has a hot dust envelope with T(dust)=1400 K and tau(V)=1.1. Besides, the star HBHA 3703-01 illuminates the encompassing diffuse nebula GM 2-39 with a diameter of about 30 arcsec. With regard to all obtained observational data for HBHA 3703-01, this object may be classified as the Herbig Ae/Be star., Comment: Accepted by MNRAS. 12 pages, 8 figures (Fig 1 and 6 are color), 3 tables

We study the ionized gas spectrum of star forming regions in the Holmberg II galaxy using the optical long-slit spectroscopic observations made at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). We estimate the oxygen, nitrogen, sulphur, neon, and argon abundances in individual HII regions and find the average metallicity in the galaxy to be Z=0.1 or 0.3 Zsun depending on the estimation method employed. We use these observations combined with the results of our earlier studies of the Irr galaxy IC 10 and BCD galaxy VII Zw 403 to compare the currently most popular methods of gas metallicity estimation in order to select among them the techniques that are most reliable for analysing Irr galaxies. To this end, we use the "direct" Te method and six empirical and theoretical methods. The results of our observations mostly confirm the conclusions of Lopez-Sanchez et al. (2012) based on the analysis of systematic deviations of metallicity estimates derived by applying different methods to "model" HII regions., Comment: 17 pages, 8 figures, 4 tables. Landscape tables 2 and 3 are on the last pages. Accepted by MNRAS

The parameters of the ionized gas in NGC 6946 (in the [NII]6548,6583, H-alpha and [SII]6717,6731 lines) are investigated with the SAO RAS BTA telescope along three positions of the long slit of the SCORPIO focal reducer, passing through a number of large and small cavities of the gaseous disc of the galaxy. Most of these cavities correspond exactly to the cavities in warm dust. We found that everywhere in the direction of NGC 6946 the lines of ionized gas are decomposed into two Gaussians, one of which shows almost constant [SII]/H-alpha and [NII]/H-alpha ratios, as well as an almost constant radial velocity within the measurement errors (about -35 - -50 km/s). This component is in fact the foreground radiation from the diffuse ionized gas of our Galaxy; a similar component is also present in the emission of neutral hydrogen. The analysis of the component of ionized gas, occurring in NGC 6946, has revealed that it shows signs of shock excitation in the cavities of the gaseous disc of the galaxy. It is as well typical for the extraplanar diffuse ionized gas (EDIG), observed in a number of spiral galaxies at their high Z-coordinates. This can most likely be explained by low density of the gas in the NGC 6946 disc (with the usual photoionization) inside the cavities, due to what we see the spectral features of the EDIG gas of NGC 6946, projected onto them. In the absence of separation of ionized gas into two components by radial velocities, there is an increasing contribution to the integral line parameters by the EDIG of our Galaxy when the gas density in NGC 6946 decreases, which explains some strange results, obtained in the previous studies. The morphology of warm dust, visible in the infrared range and HI is almost the same. The shock excitation of the ionized gas is detected also in the smallest holes, well distinguishable only in the IR images., Comment: 16 pages, 11 figures, accepted by Astrophysical Bulletin; corrected version

Based on the results of the earlier spectroscopic observations with the 6-m BTA telescope of the SAO RAS we refine the metallicity estimates of the complexes of ionized gas in the VII Zw 403 galaxy. Infrared observations from the Spitzer Space Telescope are used to search for a possible correlation of the mass fraction distribution of the polycyclic aromatic hydrocarbons (PAH) with the distribution of ionized and neutral hydrogen, and with the metallicity of gas in the HII regions of the galaxy., Comment: 10 pages, 4 figures, 3 tables

Infrared observations from the Spitzer Space Telescope archive are used to study the dust component of the interstellar medium in the IC~10 irregular galaxy. Dust distribution in the galaxy is compared to the distributions of H$\alpha$ and [SII] emission, neutral hydrogen and CO clouds, and ionizing radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH) in the galaxy is shown to be highly non-uniform with the mass fraction of these particles in the total dust mass reaching 4%. PAHs tend to avoid bright HII regions and correlate well with atomic and molecular gas. This pattern suggests that PAHs form in the dense interstellar gas. We propose that the significant decrease of the PAH abundance at low metallicity is observed not only globally (at the level of entire galaxies), but also locally (at least, at the level of individual HII regions). We compare the distribution of the PAH mass fraction to the distribution of high-velocity features, that we have detected earlier in wings of H$\alpha$ and SII lines, over the entire available galaxy area. No conclusive evidence for shock destruction of PAHs in the IC~10 galaxy could be found., Comment: Accepted for publication in Astronomy Reports

We present the results of observations of the Irr galaxy IC 10 at the 6-m SAO telescope with the panoramic Multi-Pupil Fiber Spectrograph (MPFS). Based on the results of these observations and our long-slit spectroscopy performed previously, we have investigated the ionized-gas emission spectrum in the region of intense star formation and refined the gas metallicity estimates. We show that the "diagnostic diagrams" constructed from our observations agree best with the new improved ionization models by Martin-Manjon et al. Using these models, we have determined the electron density and gas ionization parameter and ionizing-cluster characteristics, the age and mass, from the spectra of the investigated HII regions. The cluster age and mass are shown to be within the ranges 2.5 - 5 Myr and (0.2 - 1)*10^5 M(sun), respectively., Comment: 22 pages, 8 figures, 5 tables; the extended version of the paper accepted for publication in Astronomy Letters, Vol. 37, No. 2 (2011)

IC 10 is the nearest starburst irregular galaxy remarkable for its anomalously high number of WR stars. We report the results of an analysis of the emission spectra of HII-regions ionized by star clusters and WR stars based on observations made with the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences using MPFS field spectrograph and SCORPIO focal reducer operating in the slit spectrograph mode. We determine the masses and ages of ionizing star clusters in the violent star-forming region of the galaxy in terms of the new evolutionary models of emission-line spectra of HII-regions developed by Martin-Manjon et al. (2010). We estimate the amount of stars needed to ionize the gas in the brightest HII-region HL 111 and report new determinations of oxygen abundance in HII regions., Comment: To appear in the proceedings of the conference "A Universe of dwarf galaxies" (Lyon, June 14-18, 2010)

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., Comment: 22 pages, 10 figures; accepted in Astronomy Reports

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., Comment: Abridged; accepted in Astronomy Letters

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., Comment: Corrected version, 11 pages, 9 EPS figures

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., Comment: 9 pages, 6 EPS figures

The structure and kinematics of ionized gas in the star-forming region in the BCD galaxy VIIZw403 (UGC6456) are analyzed using observations with the SCORPIO focal reducer on the 6-m Special Astrophysical Observatory telescope in three modes: direct imaging (in the H-alpha, [OIII], and [SII] lines), long-slit spectroscopy, and spectroscopy with a scanning Fabry-Perot interferometer. In addition to the previously known bright HII regions and the faint giant ring that surrounds the entire star-forming region, many new faint diffuse and arc structures have been detected. Fine structure of the giant ring has been revealed. We do not confirm the previously detected expansion of the bright shells around young stellar associations with a velocity of 50-70 km/s. We have estimated their expansion velocities to be no higher than 15-20 km/s; the corresponding kinematic age, no younger than 3-4 Myr, agrees well with the age of the compact OB associations related to them. We associate the faint extended filamentary and diffuse regions of ionized gas identified in nearly the entire central region of the galaxy and the giant HII ring with the older (10 Myr) stellar population of the most recent starburst. Weak high-velocity [OIII] and H-alpha line wings (up to 300 km/s from the line center) have been detected in the brightest HII region. Such velocities have been observed in the galaxy for the first time. The previously published H-alpha luminosity measurements for the galaxy are refined., Comment: to appear in Astronomy Letters, 13 pages, 6 postscript figures, 1 in colour