- ID:
- ivo://CDS.VizieR/J/A+A/391/809
- Title:
- HII regions in NGC 5457 and NGC 4395
- Short Name:
- J/A+A/391/809
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Line intensities, visual extinction, abundances and ionization hardness parameter for HII regions in two spiral galaxies are presented. The following galaxies have been observed: NGC 5457 and NGC 4395. In NGC 5457 have been obtained data for 338 regions. In NGC 4395 have been obtained data for 158 regions. For each region position, visual extinction, H-alpha flux, H-alpha equivalent width, H-beta flux, H-beta equivalent width, [OII] flux, [OIII] flux, [SII] flux, [SIII] flux (only for NGC 5457), R23 parameter, oxygen abundance and ionization hardness parameter (only for NGC 5457) are given.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/545/A43
- Title:
- HII regions in NGC 628 and NGC 6946
- Short Name:
- J/A+A/545/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here two HII region catalogues with azimuthal resolution for the two grand design galaxies NGC 628 and NGC 6946. With the help of these catalogues, we study several properties of the star-forming processes occurring in spiral galaxies. We obtained direct imaging in the narrow-band filters centred at H{alpha}, H{beta}, [OII]{lambda}3727, and [OIII]{lambda}{lambda}4959, 5007 and their respective continua. After the calibration and correction of the data, we obtained for each HII region the de-reddened fluxes in the aforementioned lines, the size, the H{alpha} equivalent width, and, using two different empirical calibrations, the metallicity. Employing a method based on the Delaunay triangulation, a two-dimensional (2D) representation of the metallicity was obtained.
- ID:
- ivo://CDS.VizieR/J/PASP/123/649
- Title:
- HII regions in OB associations
- Short Name:
- J/PASP/123/649
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the data from the NOAO Local Group Survey, we have measured the H{alpha} fluxes of 291 nebulae associated with 21 of the van den Bergh OB associations. We have combined these data together with six-color HST WFPC2 photometry, in order to identify the most UV-bright stars in the region. The simple purpose of this article is to explore the spatial relationships between these components.
- ID:
- ivo://CDS.VizieR/J/ApJS/101/287
- Title:
- H II Regions in Seyfert galaxies. I.
- Short Name:
- J/ApJS/101/287
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data on positions, effective diameters, and absolute fluxes of H II regions on 21 Seyfert spiral galaxies are presented together with the H{alpha} + [N II] images and identification charts. The objects are selected from a larger emission-line survey of a distance-limited sample of southern Seyfert galaxies. Statistical analysis of the data as well as discussion and comparison of the H II region populations in Seyfert and normal galaxies will be presented in forthcoming papers.
- ID:
- ivo://CDS.VizieR/J/ApJS/112/29
- Title:
- HII regions in southern spiral galaxies
- Short Name:
- J/ApJS/112/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By using narrow-band filters to measure the H{alpha} flux, a catalog of H II regions in several spiral galaxies was made, consisting of the position and flux of the objects. For each galaxy the H{alpha} luminosity function was derived. From the observed sample, two galaxies were found to have type II luminosity functions. Some simple models were made in order to understand the nature of the luminosity function (both type I and type II). The goal of our work was to simulate how a change of star-forming region, the cluster-mass distribution, or the initial mass function (in an evolutionary environment) can change the shape of the luminosity function.
- ID:
- ivo://CDS.VizieR/J/A+A/441/981
- Title:
- HII regions in 5 spiral galaxies
- Short Name:
- J/A+A/441/981
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained spectroscopic observations from 3600{AA} to 9200{AA} with FORS at the Very Large Telescope for approximately 70 HII regions located in the spiral galaxies NGC 1232, NGC 1365, NGC 2903, NGC 2997 and NGC 5236. These data are part of a project aiming at measuring the chemical abundances and characterizing the massive stellar content of metal-rich extragalactic HII regions. In this paper we describe our dataset, and present emission line fluxes for the whole sample. In 32 HII regions we measure at least one of the following auroral lines: [S II]4072, [N II]5755, [S III]6312 and [O II]7325. From these we derive electron temperatures, as well as oxygen, nitrogen and sulphur abundances, using classical empirical methods (both so-called "Te-based methods" and "strong line methods"). Under the assumption that the temperature gradient does not introduce severe biases, we find that the most metal-rich nebulae with detected auroral lines are found at 12+log(O/H)~8.9, i.e. about 60% larger than the adopted solar value. However, classical abundance determinations in metal-rich HII regions may be severely biased and must be tested with realistic photoionization models. The spectroscopic observations presented in this paper will serve as a homogeneous and high-quality database for such purpose.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2805
- Title:
- H II regions in spiral galaxies
- Short Name:
- J/AJ/116/2805
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of low-dispersion optical spectroscopy of 186 HII regions spanning a range of radius in 13 spiral galaxies. Abundances for several elements (oxygen, nitrogen, neon, sulfur, and argon) were determined for 185 of the HII regions. As expected, low metallicities were found for the outlying HII regions of these spiral galaxies. Radial abundance gradients were derived for the 11 primary galaxies; similar to results for other spiral galaxies, the derived abundance gradients are typically -0.04 to -0.07dex/kpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/40
- Title:
- HII regions in the Magellanic clouds from MCELS
- Short Name:
- J/ApJ/755/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We exploit ionization-parameter mapping (IPM) as a powerful tool to measure the optical depth of star-forming H II regions. Our simulations using the photoionization code CLOUDY and our new, SURFBRIGHT surface-brightness simulator demonstrate that this technique can directly diagnose most density-bounded, optically thin nebulae using spatially resolved emission-line data. We apply this method to the Large and Small Magellanic Clouds (LMC and SMC), using the data from the Magellanic Clouds Emission Line Survey. We generate new H II region catalogs based on photoionization criteria set by the observed ionization structure in the [S II]/[O III] ratio and H{alpha} surface brightness. The luminosity functions from these catalogs generally agree with those from H{alpha}-only surveys. We then use IPM to crudely classify all the nebulae into optically thick versus optically thin categories, yielding fundamental new insights into Lyman-continuum (LyC) radiation transfer.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2246
- Title:
- HII regions in UGCA 86, 92, 105 and UGC 4115
- Short Name:
- J/AJ/116/2246
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Luminosity functions in H{alpha} have been measured for H II regions in the four dwarf galaxies UGCA 86, UGCA 92, UGCA 105, and UGC 4115 using both the traditional flux measurement method of fixed-threshold photometry (FTP) and the new method, percentage-of-peak photometry (PPP). The UGCA galaxies are members of the IC 342-Maffei 1 group. These two methods give significantly different results in galaxies in which significant numbers of peaks are associated with H II region complexes. The work demonstrates that fluxes from FTP can lead to biased luminosity functions and that PPP should, in general, be preferred. It is also shown that PPP luminosity functions are not very sensitive to atmospheric transparency, whereas those constructed from FTP can be, based on data taken under different atmospheric conditions. Results to date for six galaxies show that spirals and dwarfs have luminosity functions of similar shape, which implies that the distribution of the masses of star formation sites is largely independent of the mass, and by implication, the metallicity, of the host galaxy. As measured by PPP, the mean surface brightness of the lower luminosity H II regions grows as the one-third power of the flux grows, exactly as predicted for an ensemble in which the gas density does not vary systematically with the mass of the star cluster. For the brightest H II regions, however, the relation steepens, which implies that the most massive star clusters are formed out of the densest clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/141/113
- Title:
- HII regions of M51 and NGC 4449
- Short Name:
- J/AJ/141/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used images from the Advanced Camera for Surveys on the Hubble Space Telescope in H{alpha}, and in the neighboring continuum, to produce flux-calibrated images of the large spiral galaxy M51 and the dwarf irregular NGC 4449. From these images, we have derived the absolute luminosities in H{alpha}, the areas, and the positions with respect to the galactic centers as reference points of over 2600 HII regions in M51 and over 270 HII regions in NGC 4449.
