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1201. HUDF galaxy properties at z~2
ID:
ivo://CDS.VizieR/J/ApJ/735/L22
Title:
HUDF galaxy properties at z~2
Short Name:
J/ApJ/735/L22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use ultra-deep Hubble Space Telescope Wide Field Camera 3/infrared imaging of the Hubble Ultra Deep Field to investigate the rest-frame optical morphologies of a mass-selected sample of galaxies at z~2. We find a large variety of galaxy morphologies, ranging from large, blue, disk-like galaxies to compact, red, early-type galaxies. We derive rest-frame u-g color profiles for these galaxies and show that most z~2 galaxies in our sample have negative color gradients such that their cores are red.
1202. Hydra/Antlia extension redshifts
ID:
ivo://CDS.VizieR/J/A+A/297/617
Title:
Hydra/Antlia extension redshifts
Short Name:
J/A+A/297/617
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectroscopic observations have been carried out for galaxies in the Milky Way with the 1.9m telescope of the South African Astronomical Observatory (SAAO). The galaxies were selected from a deep optical galaxy search covering 266deg<~l<~296deg, |b|<~10deg (Kraan-Korteweg 1994). This is in the extension of the Hydra and Antlia clusters and in the approximate direction of the dipole anisotropy in the Cosmic Microwave Background radiation.
1203. HydraI galaxy cluster dwarf catalog (HCDC)
ID:
ivo://CDS.VizieR/J/A+A/659/A92
Title:
HydraI galaxy cluster dwarf catalog (HCDC)
Short Name:
J/A+A/659/A92
Date:
10 Mar 2022 07:25:32
Publisher:
CDS
Description:
Due to their relatively low stellar mass content and diffuse nature, the evolution of dwarf galaxies can be strongly affected by their environment. Analyzing the properties of the dwarf galaxies over a wide range of luminosities, sizes, morphological types, and environments, we can obtain insights about their evolution. At ~50Mpc, the Hydra I cluster of galaxies is among the closest cluster in the z=~0 Universe, and an ideal environment to study dwarf galaxy properties in a cluster environment. We exploit deep imaging data of the Hydra I cluster to construct a new photometric catalog of dwarf galaxies in the cluster core, which is then used to derive properties of the Hydra I cluster dwarf galaxy population as well as to compare it with other clusters. Moreover, we investigate the dependency of dwarf galaxy properties on their surrounding environment. The new wide-field g- and r-band images of the Hydra I cluster obtained with the OmegaCAM camera on the VLT Survey Telescope (VST) in the context of the VST Early-type GAlaxy Survey (VEGAS) were used to study the dwarf galaxy population in the Hydra I cluster core down to r-band magnitude Mr=-11.5mag. We used an automatic detection tool to identify dwarf galaxies from a ~1deg^2^ field centered on the Hydra I core, covering almost half of the cluster virial radius. The photometric pipeline was used to estimate the principal photometric parameters for all targets. Scaling relations and visual inspection were used to assess the cluster membership and construct a new dwarf galaxy catalog. Finally, based on the new catalog, we studied the structural (Sersic index n, effective radius Re, and axis ratio) and photometric (colors and surface brightness) properties of the dwarf galaxies, also investigating how they vary as a function of clustercentric distance. The new Hydra I dwarf catalog contains 317 galaxies with a luminosity between -18.5<Mr<-11.5mag, a semi-major axis larger than ~200pc (a=0.84"), of which 202 are new detections, and previously unknown dwarf galaxies in the Hydra I central region. We estimate that our detection efficiency reaches 50% at the limiting magnitude Mr=-11.5mag, and at the mean effective surface brightness <{mu}_e,r_=26.5mag/arcsec^2^. We present the standard scaling relations for dwarf galaxies, which are color-magnitude, size-luminosity, and Sersic n-magnitude relations, and compare them with other nearby clusters. We find that there are no observational differences for dwarfs scaling relations in clusters of different sizes. We study the spatial distribution of galaxies, finding evidence for the presence of substructures within half the virial radius. We also find that mid- and high-luminosity dwarfs (Mr<-14.5mag) become, on average, redder toward the cluster center, and that they have a mild increase in Re with increasing clustercentric distance, similar to what is observed for the Fornax cluster. No clear clustercentric trends are reported for surface brightness and Sersic index. Considering galaxies in the same magnitude bins, we find that for high and mid-luminosity dwarfs (Mr<-13.5mag), the g-r color is redder for the brighter surface brightness and higher Sersic n index objects. This finding is consistent with the effects of harassment and/or partial gas stripping.
1204. Hydra I wide-field imaging and spectroscopy obs.
ID:
ivo://CDS.VizieR/J/ApJ/818/39
Title:
Hydra I wide-field imaging and spectroscopy obs.
Short Name:
J/ApJ/818/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Eastern Banded Structure (EBS) and Hydra I halo overdensities are very nearby (d~10kpc) objects discovered in Sloan Digital Sky Survey (SDSS) data. Previous studies of the region have shown that EBS and Hydra I are spatially coincident, cold structures at the same distance, suggesting that Hydra I may be the EBS's progenitor. We combine new wide-field Dark Energy Camera (DECam) imaging and MMT/Hectochelle spectroscopic observations of Hydra I with SDSS archival spectroscopic observations to quantify Hydra I's present-day chemodynamical properties, and to infer whether it originated as a star cluster or dwarf galaxy. While previous work using shallow SDSS imaging assumed a standard old, metal-poor stellar population, our deeper DECam imaging reveals that Hydra I has a thin, well-defined main sequence turnoff of intermediate age (~5-6Gyr) and metallicity ([Fe/H]=-0.9dex). We measure statistically significant spreads in both the iron and alpha-element abundances of {sigma}_[Fe/H]_=0.13+/-0.02dex and {sigma}_[{alpha}/Fe]_=0.09+/-0.03dex, respectively, and place upper limits on both the rotation and its proper motion. Hydra I's intermediate age and [Fe/H] --as well as its low [{alpha}/Fe], apparent [Fe/H] spread, and present-day low luminosity-- suggest that its progenitor was a dwarf galaxy, which has subsequently lost more than 99.99% of its stellar mass.
1205. Hydrogen-Line Absorption in Early-Type Stars
ID:
ivo://CDS.VizieR/II/40
Title:
Hydrogen-Line Absorption in Early-Type Stars
Short Name:
II/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photoelectric determinations of H-{gamma} absorption line intensity have been made of stars in selected clusters and associations as well as in the general galactic field. Interference filters having a width at half intensity of 45{AA} were used to isolate spectral regions centered on 4280{AA}, H-{gamma} and 4410{AA}. The {Gamma} indices derived, which represent a measure of H-{gamma} absorption, can be used in conjunction with unreddened values of either (U-B) or (B-V) for spectral and luminosity class determinations of stars in the spectral range O6 to A0.
1206. Hyper-luminous X-ray sources from SDSS and CSC2
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.
1207. 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.
1208. 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.
1209. IAC Stripe 82 Legacy Project: Photometry
ID:
ivo://CDS.VizieR/J/MNRAS/456/1359
Title:
IAC Stripe 82 Legacy Project: Photometry
Short Name:
J/MNRAS/456/1359
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new deep co-adds of data taken within Stripe 82 of the Sloan Digital Sky Survey (SDSS), especially stacked to reach the faintest surface brightness limits of this data set. Stripe 82 covers 275 square degrees within -50{deg}<=RA<=+60{deg} and -1.26{deg}<=DE<=+1.25{deg}. We discuss the steps of our reduction which puts special emphasis on preserving the characteristics of the background (sky + diffuse light) in the input images using a non-aggressive sky subtraction strategy. Our reduction reaches a limit of ~28.5 mag/arcsec^2^ (3{sigma}, 10x10 arcsec^2^) in the r band. The effective surface brightness limit (50 per cent completeness for exponential light distribution) lies at <{mu}e(r)>~25.5mag/arcsec^2^. For point sources, we reach 50 per cent completeness limits (3{sigma} level) of (24.2, 25.2, 24.7, 24.3, 23.0) mag in (u, g, r, i, z). This is between 1.7 and 2.0mag deeper than the single-epoch SDSS releases. The co-adds show point spread functions (PSFs) with median full width at half-maximum values ranging from 1-arcsec in i and z to 1.3-arcsec in the u band. The imaging data are made publicly available at http://www.iac.es/proyecto/stripe82. The release includes deep co-adds and representations of the PSF for each field. Additionally, we provide object catalogues with stars and galaxies confidently separated until g~23mag. The IAC Stripe 82 co-adds offer a rather unique possibility to study the low surface brightness Universe, exemplified by the discovery of stellar streams around NGC 0426 and NGC 0936. We also discuss further science cases like stellar haloes and disc truncations, low surface brightness galaxies, the intracluster light in galaxy clusters and the diffuse emission of Galactic dust known as Galactic Cirrus.
1210. I-band light curves of OGLE LMC Miras
ID:
ivo://CDS.VizieR/J/AJ/152/164
Title:
I-band light curves of OGLE LMC Miras
Short Name:
J/AJ/152/164
Date:
21 Oct 2021
Publisher:
CDS
Description:
We develop a nonlinear semi-parametric Gaussian process model to estimate periods of Miras with sparsely sampled light curves. The model uses a sinusoidal basis for the periodic variation and a Gaussian process for the stochastic changes. We use maximum likelihood to estimate the period and the parameters of the Gaussian process, while integrating out the effects of other nuisance parameters in the model with respect to a suitable prior distribution obtained from earlier studies. Since the likelihood is highly multimodal for period, we implement a hybrid method that applies the quasi-Newton algorithm for Gaussian process parameters and search the period/frequency parameter space over a dense grid. A large-scale, high-fidelity simulation is conducted to mimic the sampling quality of Mira light curves obtained by the M33 Synoptic Stellar Survey. The simulated data set is publicly available and can serve as a testbed for future evaluation of different period estimation methods. The semi-parametric model outperforms an existing algorithm on this simulated test data set as measured by period recovery rate and quality of the resulting period-luminosity relations.