- 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.
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- 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/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.
1575. HII regions of M33. II.
- ID:
- ivo://CDS.VizieR/J/PASP/111/685
- Title:
- HII regions of M33. II.
- Short Name:
- J/PASP/111/685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified a total of 1272 newly recognized emission regions in M33. Combined with the previously cataloged total of 1066 H II regions and supernova remnants, this brings M33's total to 2338 emission regions. This paper provides photometry of the new objects in H{alpha}, which is combined with data from previous catalogs to produce a global H II region luminosity function (corrected for incompleteness) that reaches a faint luminosity limit of 2x10^34^ergs/s and shows a broad maximum with a peak frequency at luminosities of 6x10^35^ergs/s. We also plot the H II region size distribution and comment on unusual morphologies.
- ID:
- ivo://CDS.VizieR/J/A+AS/25/25
- Title:
- HII regions of the Northern Milky Way
- Short Name:
- J/A+AS/25/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nineteen H{alpha} photographs and a catalogue of HII regions in the northern Milky Way are presented. This atlas reveals 85 new regions of faint emission.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/627/A106
- Title:
- HI observations of AT 2018cow
- Short Name:
- J/A+A/627/A106
- Date:
- 23 Mar 2022 16:27:48
- Publisher:
- CDS
- Description:
- Unusual stellar explosions represent an opportunity to learn about both stellar and galaxy evolution. Mapping the atomic gas in host galaxies of such transients can lead to an understanding of the conditions triggering them. We provide resolved atomic gas observations of the host galaxy, CGCG137-068, of the unusual, poorly-understood transient AT2018cow searching for clues to understand its nature. We test whether it is consistent with a recent inflow of atomic gas from the intergalactic medium, as suggested for host galaxies of gamma-ray bursts (GRBs) and some supernovae (SNe). We observed the HI hyperfine structure line of the AT2018cow host with the Giant Metrewave Radio Telescope. There is no unusual atomic gas concentration near the position of AT2018cow. The gas distribution is much more regular than those of GRB/SN hosts. The AT2018cow host has an atomic gas mass lower by 0.24dex than predicted from its star formation rate (SFR) and is at the lower edge of the galaxy main sequence. In the continuum we detected the emission of AT2018cow and of a star-forming region in the north-eastern part of the bar (away from AT2018cow). This region hosts a third of the galaxy's SFR. The absence of atomic gas concentration close to AT2018cow, along with a normal SFR and regular HI velocity field, sets CGCG137-068 apart from GRB/SN hosts studied in HI. The environment of AT2018cow therefore suggests that its progenitor may not have been a massive star. Our findings are consistent with an origin of the transient that does not require a connection between its progenitor and gas concentration or inflow: an exploding low-mass star, a tidal disruption event, a merger of white dwarfs, or a merger between a neutron star and a giant star. We interpret the recently reported atomic gas ring in CGCG137-068 as a result of internal processes connected with gravitational resonances caused by the bar.
- ID:
- ivo://CDS.VizieR/J/A+A/319/67
- Title:
- HI observations of dwarf galaxies in voids
- Short Name:
- J/A+A/319/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report HI-observations of a sample of 43 optically selected galaxies from the Heidelberg-void project. Only emission-line galaxies have been selected. The HI-detection rate was 67%. The observed sample is a mix in late-type morphology objects with a spread in luminosity. They were compared to other samples with similar selection effects and mixtures. The detected galaxies have a high HI content and their M_HI_/L_B_ values are systematically higher than expected from a local field comparison sample. Especially, for the 10 dwarfs in our sample (8.2<=logL_B_<=9.2) which appear to be highly isolated, a mean M_HI_/L_B_=1.8 was derived which is higher than for all comparison samples, including those with the same restricted luminosity range. We discuss a trend in our data between the relative HI-content and the surrounding galaxy density holding from very high densities (Virgo-cluster) to the very isolated objects at the rims of the voids. We also present HI observations of 7 HII-galaxies of the University of Michigan (UM) sample.
- ID:
- ivo://CDS.VizieR/J/PAZh/31/563
- Title:
- HI observations of flat galaxies
- Short Name:
- J/PAZh/31/563
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of HI observations with the 100-m Effelsberg radio telescope are presented for 94 edge-on spiral galaxies from the Revised Flat Galaxy Catalog (Karachentsev et al., 1999, Cat. <VII/219>) and 14 galaxies from the 2MASS-selected Flat Galaxy Catalog (Mitronova et al., 2004, Bull. Spec. Astron. Obs. Russ. Acad. Sci. 57, 5). The HI line fluxes, heliocentric radial velocities and the HI line widths are given for 65 detected galaxies. Their HI profiles are shown as a mosaic. We calculated some global parameters of the galaxies and discuss linear correlations between them. Total (indicative) mass-to-luminosity ratio for the sample galaxies is ranked within 0.4-8.2 with the mean value 3.8 (M_{sun}_/L_{sun}_), and the mean fraction of hydrogen mass is 0.13. For 43 undetected objects their rms noise is also given.
