- ID:
- ivo://CDS.VizieR/J/A+A/624/A100
- Title:
- HII region G24.78+0.08 A1 images
- Short Name:
- J/A+A/624/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The earliest phases of the evolution of a massive star are closely related to the developement of an HII region. Hypercompact HII regions are the most interesting in this respect because they are very young, and hence best suited to study the beginning of the expansion of the ionised gas inside the parental core. We have analysed the geometrical and physical structure of the hypercompact HII region G24.78+0.08 A1, making use of new continuum and hydrogen recombination line data (H41{alpha}, H63{alpha}, H66{alpha}, H68{alpha}) and data from the literature (H30{alpha}, H35{alpha}). We fit the continuum spectrum with a homogenous, isothermal shell of ionised gas at 10^4^K and derive the size of the HII region and the Lyman continuum luminosity of the ionising star. We also fit the recombination line spectra emitted from the same shell with a model taking into account expansion at constant speed. The best fits to the continuum and line spectra allow the derivation of the Lyman continuum luminosity of the ionising star, HII region size, geometrical thickness of the shell, and expansion velocity. Comparison between the 5cm and 7mm brightness temperature distributions demonstrates that a thin layer of ionised gas of a few 1000K at the surface of the HII region is necessary to reproduce the morphology of the continuum emission at both wavelengths. We confirm that the G24 A1 hypercompact HII region consists of a thin shell ionised by an O9.5 star. The shell is expanding at a speed comparable to the sound speed in the ionised gas. The radius of the HII region exceeds the critical value needed to trap the ionised gas by the gravitational field of the star, consistent with the observed expansion.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/774/117
- Title:
- HII region kinematic distances
- Short Name:
- J/ApJ/774/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We make a comprehensive study of H I absorption toward H II regions located within |l|<10{deg}. Structures in the extreme inner Galaxy are traced using the longitude-velocity space distribution of this absorption. We find significant H I absorption associated with the Near and Far 3kpc Arms, the Connecting Arm, Bania's Clump 1, and the HI Tilted Disk. We also constrain the line-of-sight distances to H II regions, by using H I absorption spectra together with the H II region velocities measured by radio recombination lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/602/200
- Title:
- HII regions abundances in blue compact galaxies
- Short Name:
- J/ApJ/602/200
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use spectroscopic observations of a sample of 82 HII regions in 76 blue compact galaxies to determine the primordial helium abundance Yp and the slope dY/dZ from the Y-O/H linear regression. To improve the accuracy of the dY/dZ measurement, we have included new spectrophotometric observations of 33 HII regions that span a large metallicity range, with oxygen abundance 12+log(O/H) varying between 7.43 and 8.30 (Z_{sun}_/30<=Z<=Z_{sun}_/4). Most of the new galaxies were selected from the First Byurakan, the Hamburg/SAO, and the University of Michigan objective prism surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/1412
- Title:
- HII regions and GMC in the Antennae
- Short Name:
- J/MNRAS/445/1412
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have combined observations of the Antennae galaxies from the radio interferometer ALMA (Atacama Large Millimeter/submillimeter Array) and from the optical interferometer GH{alpha}FaS (Galaxy H{alpha} Fabry-Perot System). The two sets of observations have comparable angular and spectral resolutions, enabling us to identify 142 giant molecular clouds (GMCs) and 303 HII regions. We have measured, and compared, their basic physical properties (radius, velocity dispersion, luminosity).
6315. HII regions catalogue
- ID:
- ivo://CDS.VizieR/J/A+AS/131/319
- Title:
- HII regions catalogue
- Short Name:
- J/A+AS/131/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several galaxies were studied at Observatoire de Marseille using the films obtained at the 6m telescope with the Great Focal Reducer installed at the prime focus of the russian telescope. We thought that before we retire, it should be of some interest for the astronomical community to find in a single catalogue all the data we published to facilitate the research. (see hereunder the references). We give in this catalogue the data of the following galaxies: M 33, M 51, M 81, NGC 2403, NGC 4258 and NGC 7331. NGC 4258 was not studied with the 6m telescope, but we added its results because it was published by the same team using the same softwares. For NGC 7331 (see Petit 1998, Cat. J/A+AS/131/317). The flux values are followed by*; that means that they are not absolute fluxes like in the other publications. In order to make the catalogue easier to consult, we homogeneised the data. So, one can find some slight differences between the original data and the catalogue ones. The details of these modifications are precised in the Readme file associated to the catalogue in the data base. We did not keep the remarks so it is necessary to look at the original publication to find the full information. We give the whole references hereunder to facilitate the research of the original articles.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A2
- Title:
- HII regions detected in absorption
- Short Name:
- J/A+A/636/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cosmic rays (CRs) and the Galactic magnetic field (GMF) are fundamental actors in many processes in the Milky Way. The observed interaction product of these actors is Galactic synchrotron emission integrated over the line of sight (LOS). A comparison to simulations can be made with this tracer using existing GMF models and CR density models. This probes the GMF strength and morphology and the CR density. Our aim is to provide insight into the Galactic CR density and the distribution and morphology of the GMF strength by exploring and explaining the differences between the simulations and observations of synchrotron intensity. At low radio frequencies HII regions become opaque due to free-free absorption. Using these HII regions we can measure the synchrotron intensity over a part of the LOS through the Galaxy. The measured intensity per unit path length, that is, the emissivity, for HII regions at different distances, allows us to probe the variation in synchrotron emission not only across the sky but also in the third dimension of distance. Performing these measurements on a large scale is one of the new applications of the window opened by current low-frequency arrays. Using a number of existing GMF models in conjunction with the Galactic CR modeling code GALPROP, we can simulate these synchrotron emissivities. We present an updated catalog, compiled from the literature, of low-frequency absorption measurements of HII regions, their distances, and electron temperatures. We report a simulated emissivity that shows a compatible trend for HII regions that are near the observer. However, we observe a systematically increasing synchrotron emissivity for HII regions that are far from the observer, which is not compatible with the values simulated by the GMF models and GALPROP. Current GMF models plus a GALPROP generated CR density model cannot explain low-frequency absorption measurements. One possibility is that distances to all HII regions catalogued at the kinematic "far" distance are erroneously determined, although this is unlikely since it ignores all evidence for far distances in the literature. However, a detection bias due to the nature of this tracer requires us to keep in mind that certain sources may be missed in an observation. The other possibilities are an enhanced emissivity in the outer Galaxy or a diminished emissivity in the inner Galaxy.
- ID:
- ivo://CDS.VizieR/J/ApJ/709/424
- Title:
- HII regions identified with WMAPS and GLIMPSE
- Short Name:
- J/ApJ/709/424
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Wilkinson Microwave Anisotropy Probe (WMAP) maximum entropy method foreground emission map combined with previously determined distances to giant HII regions to measure the free-free flux at Earth and the free-free luminosity of the Galaxy. We find a total flux f_{nu}_=54211Jy and a flux from 88 sources of f_{nu}_=36043Jy. The bulk of the sources are at least marginally resolved, with mean radii ~60pc, electron density n_e_~9cm^-3^, and filling factor {Phi}HII~0.005 (over the Galactic gas disk). We use GLIMPSE and Midcourse Space Experiment (MSX) 8um images to show that the bulk of the free-free luminosity is associated with bubbles having radii r~5-100pc, with a mean of ~20pc. These bubbles are leaky, so that ionizing photons emitted inside the bubble escape and excite free-free emission beyond the bubble walls, producing WMAP sources that are larger than the 8um bubbles. We suggest that the WMAP sources are the counterparts of the extended low density HII regions described by Mezger (1978A&A....70..565M). The 18 most luminous WMAP sources emit half the total Galactic ionizing flux.
- ID:
- ivo://CDS.VizieR/J/ApJ/636/214
- Title:
- HII regions in dwarf irregular galaxies
- Short Name:
- J/ApJ/636/214
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present long-slit optical spectroscopy of 67 HII regions in 21 dwarf irregular galaxies to investigate the enrichment of oxygen, nitrogen, neon, sulfur, and argon in low-mass galaxies. Oxygen abundances are obtained via direct detection of the temperature-sensitive emission lines for 25 HII regions; for the remainder of the sample, oxygen abundances are estimated from strong-line calibrations. The direct abundance determinations are compared to the strong-line abundance calibrations of both McGaugh (1991ApJ...380..140M) and Pilyugin (2000A&A...362..325P).
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/1307
- Title:
- HII regions in 10 galaxies
- Short Name:
- J/MNRAS/451/1307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed 10 interacting galaxy pairs using the Fabry-Perot interferometer GH{alpha}FaS (Galaxy H{alpha} Fabry-Perot system) on the 4.2m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos, La Palma. We present here the H{alpha} surface brightness, velocity and velocity dispersion maps for the 10 systems we have not previously observed using this technique, as well as the physical properties (sizes, H{alpha} luminosities and velocity dispersion) of 1259 HII regions from the full sample. We also derive the physical properties of 1054 HII regions in a sample of 28 isolated galaxies observed with the same instrument in order to compare the two populations of HII regions. We find a population of the brightest HII regions for which the scaling relations, for example the relation between the H{alpha} luminosity and the radius, are clearly distinct from the relations for the regions of lower luminosity. The regions in this bright population are more frequent in the interacting galaxies. We find that the turbulence, and also the star formation rate, are enhanced in the HII regions in the interacting galaxies. We have also extracted the H{alpha} equivalent widths for the HII regions of both samples, and we have found that the distribution of HII region ages coincides for the two samples of galaxies. We suggest that the SFR enhancement is brought about by gas flows induced by the interactions, which give rise to gravitationally bound gas clouds which grow further by accretion from the flowing gas, producing conditions favourable to star formation.
- ID:
- ivo://CDS.VizieR/J/other/Ser/187.11
- Title:
- HII regions in IC342 galaxy
- Short Name:
- J/other/Ser/187.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present HII regions in the portion of the nearby spiral galaxy IC342. In this table we report coordinates, diameters, Hα and [SII] fluxes for 203 HII regions detected in two fields of view. The number of detected HII regions is 5 times higher than previously known in these two parts of the galaxy.