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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A14
- Title:
- HI observations of the MATLAS dwarfs
- Short Name:
- J/A+A/659/A14
- Date:
- 25 Feb 2022 07:33:51
- Publisher:
- CDS
- Description:
- The presence of HI gas in galaxies is inextricably linked to their morphology and evolution. This paper aims to understand the HI content of the already identified 2210 dwarfs located in the low-to-moderate density environments of the MATLAS deep imaging survey. We combine the HI observations from the ATLAS3D survey, with the extragalactic HI sources from the ALFALFA survey, to extract the HI line width, velocity and mass of the MATLAS dwarfs. From the 1773 dwarfs in our sample with available HI observations, 8% (145) have an HI line detection. The majority of the dwarfs show irregular morphology, while 29% (42) are ellipticals, the largest sample of HI-bearing dwarf ellipticals (dEs) to date. Of the HI dwarf sample, 2% (3) are ultra-diffuse galaxies (UDGs), 12% have a transition-type morphology, 5% are tidal dwarf candidates, and 10% appear to be disrupted objects. In our optically selected sample, 9.5% of the dEs, 7% of the UDGs and 10% of the classical dwarfs are HI-bearing. The HI-bearing dwarfs have on average bluer colors than the dwarfs without detected HI. We find relations between the stellar and HI masses, gas fraction, color and absolute magnitude consistent with previous studies of dwarfs probing similar masses and environments. For 79% of the dwarfs identified as satellites of massive early-type galaxies, we find that the HI mass increases with the projected distance to the host. Using the HI line width, we estimate dynamical masses and find that 5% (7) of the dwarfs are dark matter deficient.
1587. HIPASS catalogue. III.
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/34
- Title:
- HIPASS catalogue. III.
- Short Name:
- J/MNRAS/361/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest catalogue to date of optical counterparts for H i radio-selected galaxies, HOPCAT. Of the 4315 H i radio-detected sources from the HI Parkes All Sky Survey (HIPASS) catalogue, we find optical counterparts for 3618 (84 per cent) galaxies. Of these, 1798 (42 per cent) have confirmed optical velocities and 848 (20 per cent) are single matches without confirmed velocities. Some galaxy matches are members of galaxy groups. From these multiple galaxy matches, 714 (16 per cent) have confirmed optical velocities and a further 258 (6 per cent) galaxies are without confirmed velocities. For 481 (11 per cent), multiple galaxies are present but no single optical counterpart can be chosen and 216 (5 per cent) have no obvious optical galaxy present. Most of these "blank fields" are in crowded fields along the Galactic plane or have high extinctions. Isolated "dark galaxy" candidates are investigated using an extinction cut of A_Bj_<1mag and the blank-fields category. Of the 3692 galaxies with an A+Bj_ extinction <1mag, only 13 are also blank fields. Of these, 12 are eliminated either with follow-up Parkes observations or are in crowded fields. The remaining one has a low surface brightness optical counterpart. Hence, no isolated optically dark galaxies have been found within the limits of the HIPASS survey.
- ID:
- ivo://CDS.VizieR/J/A+AS/144/45
- Title:
- Hipparcos astrometry for 257 stars
- Short Name:
- J/A+AS/144/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present improved Hipparcos astrometry for 257 Hipparcos stars, resolved into 342 components. For 64 of the stars no astrometry was obtained in the Hipparcos Catalogue, while for the remaining stars additional components have been added by this solution or the positions have been revised considerably. We have used the published Hipparcos transit data for the new solutions, together with results from the second reduction of the Tycho data for defining better initial values.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/L72
- Title:
- Hipparcos calibration of the TRGB
- Short Name:
- J/ApJ/703/L72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected the tip of the red giant branch (TRGB) in the solar neighborhood using near-infrared photometry from the Two Micron All Sky Survey (II/246) and DIRBE (J/ApJS/154/673) catalogs, and revised Hipparcos parallaxes. We confirm that the revised Hipparcos parallaxes are superior to the original ones, and that this improvement is necessary to detect the TRGB. We find a tip absolute magnitude of M_K_=-6.85+/-0.03, in agreement with that expected from previous tip measurements of the Large Magellanic Cloud, Small Magellanic Cloud, and Bulge. This represents the first geometric calibration of the TRGB and extends previous calibrations, based on metal-poor globular clusters, to solar metallicities. We attempted to use the TRGB to confirm the presence of the Lutz-Kelker bias, with inconclusive results. Attempts to detect the tip in the I band also produced inconsistent results, due to a lack of precise, homogeneous photometry for these bright stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/42
- Title:
- Hipparcos-Gaia (EDR3) Catalog of Accelerations
- Short Name:
- J/ApJS/254/42
- Date:
- 28 Oct 2021 07:00:25
- Publisher:
- CDS
- Description:
- We present a cross-calibration of Hipparcos and Gaia EDR3 intended to identify astrometrically accelerating stars and to fit orbits to stars with faint, massive companions. The resulting catalog, the EDR3 edition of the Hipparcos-Gaia Catalog of Accelerations (HGCA), provides three proper motions with calibrated uncertainties on the EDR3 reference frame: the Hipparcos proper motion, the Gaia EDR3 proper motion, and the long-term proper motion given by the difference in position between Hipparcos and Gaia EDR3. Our approach is similar to that for the Gaia DR2 edition of the HGCA but offers a factor of ~3 improvement in precision thanks to the longer time baseline and improved data processing of Gaia EDR3. We again find that a 60/40 mixture of the two Hipparcos reductions outperforms either reduction individually, and we find strong evidence for locally variable frame rotations between all pairs of proper motion measurements. The substantial global frame rotation seen in DR2 proper motions has been removed in EDR3. We also correct for color- and magnitude-dependent frame rotations at a level of up to ~50{mu}as/yr in Gaia EDR3. We calibrate the Gaia EDR3 uncertainties using a sample of radial velocity standard stars without binary companions; we find an error inflation factor (a ratio of total to formal uncertainty) of 1.37. This is substantially lower than the position-dependent factor of ~1.7 found for Gaia DR2 and reflects the improved data processing in EDR3. While the catalog should be used with caution, its proper motion residuals provide a powerful tool to measure the masses and orbits of faint, massive companions to nearby stars.
