Ionized gas and sources of its ionization in the Irr galaxy IC 10

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

Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10

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 Report

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

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.Comment: Abridged; accepted in Astronomy Letter

SRAO CO Observation of 11 Supernova Remnants in l = 70 to 190 deg

We present the results of 12CO J = 1-0 line observations of eleven Galactic supernova remnants (SNRs) obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. The observation was made as a part of the SRAO CO survey of SNRs between l = 70 and 190 deg, which is intended to identify SNRs interacting with molecular clouds. The mapping areas for the individual SNRs are determined to cover their full extent in the radio continuum. We used halfbeam grid spacing (60") for 9 SNRs and full-beam grid spacing (120") for the rest. We detected CO emission towards most of the remnants. In six SNRs, molecular clouds showed a good spatial relation with their radio morphology, although no direct evidence for the interaction was detected. Two SNRs are particularly interesting: G85.4+0.7, where there is a filamentary molecular cloud along the radio shell, and 3C434.1, where a large molecular cloud appears to block the western half of the remnant. We briefly summarize the results obtained for individual SNRs.Comment: Accepted for publication in Astrophysics & Space Science. 12 pages, 12 figures, and 3 table

Wind-Blown Bubbles around Evolved Stars

Most stars will experience episodes of substantial mass loss at some point in their lives. For very massive stars, mass loss dominates their evolution, although the mass loss rates are not known exactly, particularly once the star has left the main sequence. Direct observations of the stellar winds of massive stars can give information on the current mass-loss rates, while studies of the ring nebulae and HI shells that surround many Wolf-Rayet (WR) and luminous blue variable (LBV) stars provide information on the previous mass-loss history. The evolution of the most massive stars, (M > 25 solar masses), essentially follows the sequence O star to LBV or red supergiant (RSG) to WR star to supernova. For stars of mass less than 25 solar masses there is no final WR stage. During the main sequence and WR stages, the mass loss takes the form of highly supersonic stellar winds, which blow bubbles in the interstellar and circumstellar medium. In this way, the mechanical luminosity of the stellar wind is converted into kinetic energy of the swept-up ambient material, which is important for the dynamics of the interstellar medium. In this review article, analytic and numerical models are used to describe the hydrodynamics and energetics of wind-blown bubbles. A brief review of observations of bubbles is given, and the degree to which theory is supported by observations is discussed.Comment: To be published as a chapter in 'Diffuse Matter from Star Forming Regions to Active Galaxies' - A volume Honouring John Dyson. Eds. T. W. Harquist, J. M. Pittard and S. A. E. G. Falle. 22 pages, 12 figure

Asymmetrical nebula of the M33 variable GR290 (WR/LBV)

© ESO 2020. Context. GR 290 (M 33 V0532 = Romano's star) is a luminous M 33 object undergoing photometric variability typical for luminous blue variable stars. It lies inside the Wolf-Rayet region in the Hertzsprung-Russell diagram and possesses a WN8-type spectrum at the light minima. Analysis of Gran Telescopio Canarias spectra obtained in 2016 led to the conclusion that it is surrounded by an unresolved H II region formed mostly of ejected material from the central star and revealed the presence of a second, more extended asymmetrical emission region. Aims. The aim of this paper is to further explore the structure of the nearby environment of GR 290. Methods. Long-slit spectra of GR 290 were obtained with three slit orientations in the visual and red spectral regions. The emission-line distribution for each slit was analyzed. Results. We confirm the presence of an asymmetric H II region that extends ~50 pc to the south; ~30 pc to the north, and southeast; ~20 pc to the east and northwest; and ~10 pc to the west. We also present the first spectrum to be acquired of a star belonging to the neighboring OB 88 association, J013501.87+304157.3, which we classify as a B-type supergiant with a possible binary companion