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1571. HII Regions in NGC 4258
ID:
ivo://CDS.VizieR/J/A+A/268/419
Title:
HII Regions in NGC 4258
Short Name:
J/A+A/268/419
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
1572. HII regions in NGC 628
ID:
ivo://CDS.VizieR/J/A+A/466/905
Title:
HII regions in NGC 628
Short Name:
J/A+A/466/905
Date:
21 Oct 2021
Publisher:
CDS
Description:
Properties of HII region populations in spiral galaxies provide important information about the physics of star formation as well as regional turbulent motions in the interstellar medium. We present a set of 376 photometrically calibrated HII regions in the nearby late-type spiral galaxy NGC 628. We have studies the mean velocity and velocity dispersion for the H-alpha-emitting gas in NGC 628 and found with widely distributed star formation in the disc plane. The H-alpha emission from the HII regions dominates any emission from the diffuse component in this galaxy.
1573. HII regions in NGC 5055
ID:
ivo://CDS.VizieR/J/other/RMxAA/44.161
Title:
HII regions in NGC 5055
Short Name:
J/other/RMxAA/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, using CCD observations of the galaxy NGC 5055 in the emission lines of Halpha and Hbeta (Rozas, 2007RMxAA, submitted), together with CCD observations in the narrow-band filters of [OII], [OIII], [SII], and S[III] lines we have calculated the equivalent widths, excitations, ionization hardness, ionization parameters and metallicities for the regions catalogued in Rozas (2007RMxAA, submitted).
1574. HII regions in NGC 628 and NGC 6946
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.
1575. H II Regions in Seyfert galaxies. I.
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.
1576. HII regions in 5 spiral galaxies
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.
1577. H II regions in spiral galaxies
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.
1578. HII regions in UGCA 86, 92, 105 and UGC 4115
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.
1579. HII regions of M51 and NGC 4449
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.
1580. HII Regions Properties in M101
ID:
ivo://CDS.VizieR/J/AJ/104/92
Title:
HII Regions Properties in M101
Short Name:
J/AJ/104/92
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectrophotometrically calibrated CCD imagery of two overlapping 16 arc min fields in the SAB(rs)cdI galaxy M101 in the emission of H alpha, [O III] lambda 5007, H beta, and [S II] lambda 6723 are used to study various physical properties of the H II region population. Individual H II regions are identified and mapped using an automated algorithm, thus eliminating personal bias in the measurements. Characteristics of the population studied include the H II region luminosity function and radial variations in extinction, [O III]/H beta, O/H, [S II]/H alpha, ionization parameter, and numbers of ionizing photons. In addition, radial and azimuthal variations in the H II surface density are studied in comparison to that of H I and H_2 inferred from radio 21 cm and CO observations. It is demonstrated that the magnitude of trends and ``gradients'' found from such analyses depend on the surface brightness threshold set in defining the H II region boundaries; so results are presented for both low (log S(H alpha) = -15.7 ergs/s/cm^2/arcsec^2; 625 H II regions) and high (-15.0; 248 H II regions) thresholds. Radial gradients in both extinction, C(H beta), and O/H are seen in the H II region population -- with a distinct flattening in the O/H gradient seen in the outer disk beginning at about 10 kpc. The luminosity function of the H II region population found is similar to previous studies, though both the high and low ends are sensitive to the threshold levels set. Other parameters, such as the ionization parameters, luminosities, and size distribution, show no evidence for systematic variations with galactocentric distance. Current star formation processes active in the disk of M101 are analyzed two-dimensionally by comparison of the distribution of ionized and neutral hydrogen. The star formation efficiency shows considerable variation across the disk, suggesting significant spatial variation in the critical density for cloud collapse across the disk of M101 and thus departures from the simple Toomre model.

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