- ID:
- ivo://CDS.VizieR/J/A+A/486/697
- Title:
- Hydra I Cluster Catalogue (HCC)
- Short Name:
- J/A+A/486/697
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse the properties of the early-type dwarf galaxy population in the Hydra I cluster. We investigate the galaxy luminosity function, the colour-magnitude relation, and the magnitude-surface brightness relation down to M_V_=-10mag. Deep VLT/FORS1 images in V and I bands were examined. We identify cluster members by radial velocity measurements and select other cluster galaxy candidates by their morphology. The candidates' total magnitudes and central surface brightnesses were derived from the analysis of their surface brightness profiles.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/3355
- Title:
- Hydrogen volume densities in nearby galaxies
- Short Name:
- J/MNRAS/428/3355
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic discs. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate the total hydrogen volume densities of the giant molecular clouds surrounding sites of recent star formation. Until now this was only possible on a galaxy-by-galaxy basis using by-eye analysis of candidate photodissociation regions. We test the automated method by adopting various models for the dust-to-gas ratio and comparing the resulting densities for M74, including a new metallicity map of M74 produced by integral field spectroscopy. We test the procedure against previously published M83 volume densities based on the same method and find no significant differences. The range of total hydrogen volume densities obtained for M74 is approximately 5-700cm^-3^. Different dust-to-gas ratio models do not result in measurably different densities. The cloud densities presented here mean that M74 is added to the list of galaxies analysed using the assumption of photodissociated atomic hydrogen occurring near sites of recent star formation, and consolidate the method. For the first time, full metallicity maps are included in the analysis as opposed to metallicity gradients. The results will need to be compared with other tracers of the interstellar medium and photodissociation regions, such as CO and CII, in order to test our basic assumptions, specifically our assumption that the HI we detect originates in photodissociation regions.
- ID:
- ivo://CDS.VizieR/VII/237
- Title:
- HYPERLEDA. I. Catalog of galaxies
- Short Name:
- VII/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the new catalog of principal galaxies (PGC2003). It constitutes the framework of the HYPERLEDA database that supersedes the LEDA one, with more data and more capabilities. The catalog is still restricted to confirmed galaxies, i.e. about one million galaxies, brighter than ~18B-mag. In order to provide the best possible identification for each galaxy we give: accurate coordinates (typical accuracy better than 2 arcsec), diameter, axis ratio and position angle. Diameters and axis ratios have been homogenized to the RC2 system at the limiting surface brightness of 25B-mag/arcsec^2^, using a new method, the EPIDEMIC method. In order to provide the best designation for each galaxy, we collected the names from 50 catalogues. The compatibility of the spelling is tested against NED and SIMBAD, and, as far as possible we used a spelling compatible with both. For some cases, where no consensus exists between NED, SIMBAD and LEDA, we propose some changes that could make the spelling of names fully compatible. The full catalog is distributed through the CDS and can be extracted from HYPERLEDA, http://leda.univ-lyon1.fr/ .
- ID:
- ivo://CDS.VizieR/VII/238
- Title:
- HYPERLEDA. II. Homogenized HI data
- Short Name:
- VII/238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After a compilation of HI data from 611 references and new observations made in Nancay, we produce a catalog of homogenized HI data for 16781 galaxies. The homogenization is made using the EPIDEMIC method from which all data are progressively converted into the adopted standard. The result is a catalog giving: 1) the logarithm of twice the maximum rotation velocity, log2V_M_^sini^, converted to the system of Mathewson et al. (1996ApJS..107...97M). This quantity is given without correction for inclination; 2) the HI magnitude, m_21_, (area of the 21-cm line width expressed in magnitude) converted to the flux system of Theureau et al. (1998A&AS..130..333T); 3) the HI velocity, V_HI_, expressed with the optical definition (i.e., using wavelengths instead frequencies). The typical uncertainties are: 0.04 for log2V_M_^sini^, 0.25mag for m_21_ and 9km/s for V_HI_.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/117
- Title:
- HyperLeda sample of nearby elliptical galaxies
- Short Name:
- J/ApJ/756/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the effect of the environment on the Faber-Jackson (FJ) relation, using a sample of 384 nearby elliptical galaxies and estimating objectively their environment on the typical scale of galaxy clusters. We show that the intrinsic scatter of the FJ relation is significantly reduced when ellipticals in high-density environments are compared to ellipticals in low-density ones. This result, which holds in a limited range of overdensities, is likely to provide an important observational link between scaling relations and formation mechanisms in galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/181
- Title:
- Hyper-luminous X-ray sources from SDSS and CSC2
- Short Name:
- J/ApJ/882/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hyper-luminous X-ray sources (HLXs; L_X_>10^41^erg/s) are off-nuclear X-ray sources in galaxies and strong candidates for intermediate-mass black holes (IMBHs). We have constructed a sample of 169 HLX candidates by combining X-ray detections from the Chandra Source Catalog (Version 2) with galaxies from the Sloan Digital Sky Survey and registering individual images for improved relative astrometric accuracy. The spatial resolution of Chandra allows for the sample to extend out to z~0.9. Optical counterparts are detected among one-fourth of the sample, one-third of which are consistent with dwarf galaxy stellar masses. The average intrinsic X-ray spectral slope indicates efficient accretion, potentially driven by galaxy mergers, and the column densities suggest one-third of the sample has significant X-ray absorption. We find that 144 of the HLX candidates have X-ray emission that is significantly in excess of the expected contribution from star formation and hot gas, strongly suggesting that they are produced by accretion onto black holes more massive than stars. After correcting for an average background or foreground contamination rate of 8%, we estimate that at least ~20 of the HLX candidates are consistent with IMBH masses, and this estimate is potentially several times higher assuming more efficient accretion. This catalog currently represents the largest sample of uniformly selected, off-nuclear IMBH candidates. These sources may represent scenarios in which a low-mass galaxy hosting an IMBH has merged with a more massive galaxy and provide an excellent sample for testing models of low-mass BH formation and merger-driven growth.
1747. Hypervelocity stars. II.
- ID:
- ivo://CDS.VizieR/J/ApJ/660/311
- Title:
- Hypervelocity stars. II.
- Short Name:
- J/ApJ/660/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hypervelocity stars (HVSs) are stars ejected completely out of the Milky Way by three-body interactions with the massive black hole in the Galactic center. We describe 643 new spectroscopic observations from our targeted survey for HVSs. We find a significant (3.5{sigma}) excess of B-type stars with large velocities +275km/s<V_rf_<450km/s and distances d>10kpc that are most plausibly explained as a new class of HVSs: stars ejected from the Galactic center on bound orbits. If a Galactic center ejection origin is correct, the distribution of HVSs on the sky should be anisotropic for a survey complete to a fixed limiting apparent magnitude. The unbound HVSs in our survey have a marginally anisotropic distribution on the sky, consistent with the Galactic center ejection picture.
1748. Hypervelocity stars. III
- ID:
- ivo://CDS.VizieR/J/ApJ/671/1708
- Title:
- Hypervelocity stars. III
- Short Name:
- J/ApJ/671/1708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of three new unbound hypervelocity stars (HVSs), stars travelling with such extreme velocities that dynamical ejection from a massive black hole (MBH) is their only suggested origin. We also detect a population of possibly bound HVSs.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/102
- Title:
- I-band GALFIT analysis of luminous infrared galaxies
- Short Name:
- J/ApJ/768/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L_IR_>10^11.4^ L_{sun}_) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W "I-band" images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64+/-0.62 mag (1.8_-0.4_^+1.4^ L_1_^*^), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger advances. In contrast, the fraction of nuclear PSFs increases toward later merger stages and is highest in late-stage systems with a single nucleus. Thus, light from an active galactic nucleus or compact nuclear star cluster is more visible at I band as ULIRGs enter their latter stages of evolution. Finally, both GOALS elliptical hosts and nearby Sloan Digital Sky Survey (SDSS) ellipticals occupy the same part of the surface brightness versus half-light radius plot (i.e., the "Kormendy Relation") and have similar slopes, consistent with the possibility that the GOALS galaxies belong to the same parent population as the SDSS ellipticals.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/1753
- Title:
- I-band light curves of SNe II from OGLE-IV
- Short Name:
- J/MNRAS/449/1753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 11 Type II supernovae (SNe) discovered by the OGLE-IV survey. All objects have well-sampled I-band light curves, and at least one spectrum. We find that two or three of the 11 SNe have a declining light curve, and spectra consistent with other SNe II-L, while the rest have plateaus that can be as short as 70 d, unlike the 100 d typically found in nearby galaxies. The OGLE SNe are also brighter, and show that magnitude-limited surveys find SNe that are different than usually found in nearby galaxies. We discuss this sample in the context of understanding Type II SNe as a class and their suggested use as standard candles.