Search

Start Over Subject photometry Capability Type Simple Cone Search
2111. Hyades brown dwarfs and very low mass stars
ID:
ivo://CDS.VizieR/J/A+A/481/661
Title:
Hyades brown dwarfs and very low mass stars
Short Name:
J/A+A/481/661
Date:
21 Oct 2021
Publisher:
CDS
Description:
We conducted a search for brown dwarfs (BDs) and very low mass (VLM) stars in the 625Myr-old Hyades cluster in order to derive the cluster's mass function across the stellar-substellar boundary. We performed a deep (I=23, z=22.5) photometric survey over 16deg^2^ around the cluster center and followed up with K-band photometry to measure the proper motion of candidate members and with optical and near-IR spectroscopy of probable BD and VLM members.
2112. Hyades single stars fiducial photometry
ID:
ivo://CDS.VizieR/J/A+A/585/A7
Title:
Hyades single stars fiducial photometry
Short Name:
J/A+A/585/A7
Date:
21 Oct 2021
Publisher:
CDS
Description:
Age and mass determinations for isolated stellar objects remain model-dependent. While stellar interior and atmospheric theoretical models are rapidly evolving, we need a powerful tool to test them. Open clusters are good candidates for this role. We aim to create a fiducial sequence of stellar objects for testing stellar and atmospheric models. We complement previous studies on the Hyades multiplicity by Lucky Imaging observations with the AstraLux Norte camera. This allows us to exclude possible binary and multiple systems with companions outside 2-7AU separation and to create a "single-star sequence" for the Hyades. The sequence encompasses 250 main-sequence stars ranging from A5V to M6V. Using the "Tool for Astrophysical Data Analysis" (TA-DA), we create various theoretical isochrones applying different combinations of interior and atmospheric models. We compare the isochrones with the observed Hyades single-star sequence on J vs. J-Ks, J vs. J-H and Ks vs. H-Ks color-magnitude diagrams. As a reference we also compute absolute fluxes and magnitudes for all stars from X-ray to mid-infrared based on photometric measurements available in the literature (ROSAT X-ray, GALEX UV, APASS gri, 2MASS JHKs, and WISE W1 to W4). We find that combinations of both PISA and DARTMOUTH stellar interior models with BT-Settl 2010 atmospheric models describe the observed sequence well. We use PISA in combination with BT-Settl 2010 models to derive theoretical predictions for physical parameters (Teff, mass, logg) of 250 single stars in the Hyades. The full sequence covers the mass range 0.13 to 2.3M_{sun}_, and effective temperatures between 3060K and 8200K. Conclusions. Within the measurement uncertainties, the current generation of models agree well with the single-star sequence. The primary limitations are the uncertainties in the measurement of the distance to individual Hyades members, and uncertainties in the photometry. Gaia parallaxes, photometry and spectroscopy will greatly reduce the uncertainties in particular at the lowest mass range, and will enable us to test model predictions with greater confidence. Additionally, a small (~0.05mag) systematic offset can be noted on J vs. J-K and K vs. H-K diagrams - the observed sequence is shifted to redder colors from the theoretical predictions.
2113. Hydra I Cluster Catalogue (HCC)
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.
2114. 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.
2115. 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.
2116. 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.
2117. 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.
2118. 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.
2119. 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.
2120. I-band GALFIT analysis of luminous infrared galaxies
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.