- ID:
- ivo://CDS.VizieR/J/ApJ/707/1417
- Title:
- HST view of YSOs in the LMC
- Short Name:
- J/ApJ/707/1417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used archival Hubble Space Telecope (HST) H{alpha} images to study the immediate environments of massive and intermediate-mass young stellar object (YSO) candidates in the Large Magellanic Cloud (LMC). The sample of YSO candidates, taken from Gruendl & Chu (2009, Cat. J/ApJS/184/172), was selected based on Spitzer IRAC and MIPS observations of the entire LMC and complementary ground-based optical and near-infrared observations. We found HST H{alpha} images for 99 YSO candidates in the LMC, of which 82 appear to be genuine YSOs. More than 95% of the YSOs are found to be associated with molecular clouds. YSOs are seen in three different kinds of environments in the H{alpha} images: in dark clouds, inside or on the tip of bright-rimmed dust pillars, and in small HII regions. Comparisons of spectral energy distributions for YSOs in these three different kinds of environments suggest that YSOs in dark clouds are the youngest, YSOs with small HII regions are the most evolved, and YSOs in bright-rimmed dust pillars span a range of intermediate evolutionary stages. This rough evolutionary sequence is substantiated by the presence of silicate absorption features in the Spitzer Infrared Spectrograph spectra of some YSOs in dark clouds and in bright-rimmed dust pillars, but not those of YSOs in small HII regions. We present a discussion on triggered star formation for YSOs in bright-rimmed dust pillars or in dark clouds adjacent to HII regions. As many as 50% of the YSOs are resolved into multiple sources in high-resolution HST images.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/624/A25
- Title:
- HST WFC3 photometry of NGC 2419
- Short Name:
- J/A+A/624/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W-F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of {Delta}Y~=0.05, but the P2 stars exhibit a significant spread in He content and some may reach {Delta}Y~=0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances ([Mg/Fe]<0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p~=0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2081
- Title:
- Hubble Deep Field catalog of color-based redshift
- Short Name:
- J/AJ/116/2081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive simple empirical color-redshift relations for z<~4 galaxies in the Hubble Deep Field (HDF) using a linear function of three photometric colors (U-B, B-V, V-I). The dispersion between the estimated redshifts and the spectroscopically observed ones is small for relations derived in several separate color regimes; the dispersions range from {sigma}_z_~=0.03 to 0.1 for z<~2 galaxies, and from {sigma}_z_~=0.14 to 0.25 for z>~2 galaxies. We apply the color-redshift relations to the HDF photometric catalog and obtain estimated redshifts that are consistent with those derived from spectral template fitting methods. The advantage of these color-redshift relations is that they are simple and easy to use and do not depend on the assumption of any particular spectral templates; they provide model independent redshift estimates for z<~4 galaxies using only multiband photometry, and they apply to about 90% of all galaxies. We provide a color-based estimated redshift catalog of HDF galaxies to z<~4. We use the estimated redshifts to investigate the redshift distribution of galaxies in the HDF; we find peaks in the redshift distribution that suggest large-scale clustering of galaxies to at least z~1 and that are consistent with those identified in spectroscopic probes of the HDF.
- ID:
- ivo://CDS.VizieR/J/ApJ/548/127
- Title:
- Hubble Deep Field-South region
- Short Name:
- J/ApJ/548/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the galaxy-galaxy angular correlations as a function of photometric redshift in a deep, wide galaxy survey centered on the Hubble Deep Field-South (HDF-S). Images were obtained with the Big Throughput Camera on the Blanco 4-m telescope at CTIO, of 1/2 square degree in broadband uBVRI, reaching ~24mag. Approximately 40,000 galaxies are detected in the survey. We determine photometric redshifts using galaxy template fitting to the photometry.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2549
- Title:
- HW Per UBV differential photometry
- Short Name:
- J/AJ/116/2549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A complete photometric analysis for the eclipsing binary candidate HW Persei is presented. The UBV observations were taken at Lowell Observatory in 1996 January. Three epochs of minimum light were determined, and an improved linear ephemeris was calculated. The O-C residuals, spanning some 60 years, show no evidence of a period change. Standard magnitudes are given, and reddening estimates are made. The first published synthetic light curve solutions of HW Per reveal that it is near a state of critical contact, which we define as both components exactly filling their respective Roche lobes. The primary component is of A8 spectral type, and the secondary component is a K3-K4 spectral type. The nature of the model is discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3181
- Title:
- HW Vir differential VR light curves
- Short Name:
- J/AJ/137/3181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the very short period subdwarf B eclipsing binary HW Vir, we present new CCD photometry made from 2000 through 2008. In order to obtain consistency of the binary parameters, our new light curves, showing sharp eclipses and a striking reflection effect, were analyzed simultaneously with previously published radial velocity data. The secondary star parameters of M_2_=0.14M_{sun}_, R_2_=0.18R_{sun}_, and T_2_=3084K are consistent with those of an M6-7 main-sequence star. A credibility issue regarding bolometric corrections is emphasized. More than 250 times of minimum light, including our 41 timings and spanning more than 24yr, were used for a period study. From a detailed analysis of the O-C diagram, it emerged that the orbital period of HW Vir has varied as a combination of a downward-opening parabola and two sinusoidal variations, with cycle lengths of P_3_=15.8yr and P_4_=9.1yr and semiamplitudes of K_3_=77s and K_4_=23s, respectively. The continuous period decrease with a rate of -8.28x10^-9^d/yr may be produced by angular momentum loss due to magnetic stellar wind braking but not by gravitational radiation.
1658. Hyades binaries
- ID:
- ivo://CDS.VizieR/J/A+A/310/879
- Title:
- Hyades binaries
- Short Name:
- J/A+A/310/879
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived accurate and homogeneous lithium abundances in 49 Main Sequence binary systems belonging to the Hyades open cluster by using a deconvolution method to determine individual magnitudes and colors for the primary and secondary components of the binary. The input parameters of the model are the observed Li equivalent width, the actual distance to the binary, the integrated apparent magnitude and the integrated colors of the binaries -BV(RI)_K_. We show that the general behavior is the same in binaries and in single stars (Li is depleted faster in K stars than in G stars and there is a deep dip for mid-F stars). However, there is a larger scatter in the abundances of binary systems than in single stars. Moreover, in general, binary systems have an overabundance, which is more conspicuous in close binaries. In fact, there is a cut-off period, which can be estimated as P_orb_~9d. This value is in excellent agreement with the theoretical prediction of Zahn (1994).
1659. Hyades membership
- ID:
- ivo://CDS.VizieR/J/A+A/331/81
- Title:
- Hyades membership
- Short Name:
- J/A+A/331/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use absolute trigonometric parallaxes from the Hipparcos Catalogue (Cat. <I/239>) to determine individual distances to members of the Hyades cluster, from which the 3-dimensional structure of the cluster can be derived. Inertially-referenced proper motions are used to rediscuss distance determinations based on convergent-point analyses. A combination of parallaxes and proper motions from Hipparcos, and radial velocities from ground-based observations, are used to determine the position and velocity components of candidate members with respect to the cluster centre, providing new information on cluster membership: 13 new candidate members within 20pc of the cluster centre have been identified. Farther from the cluster centre there is a gradual merging between certain cluster members and field stars, both spatially and kinematically. Within the cluster, the kinematical structure is fully consistent with parallel space motion of the component stars with an internal velocity dispersion of about 0.3km/s. The spatial structure and mass segregation are consistent with N-body simulation results, without the need to invoke expansion, contraction, rotation, or other significant perturbations of the cluster. The quality of the individual distance determinations permits the cluster zero-age main sequence to be accurately modelled. The helium abundance for the cluster is determined to be Y=0.26+/-0.02 which, combined with isochrone modelling including convective overshooting, yields a cluster age of 625+/-50Myr. The distance to the observed centre of mass (a concept meaningful only in the restricted context of the cluster members contained in the Hipparcos Catalogue) is 46.34+/-0.27pc, corresponding to a distance modulus m-M=3.33+/-0.01mag for the objects within 10pc of the cluster centre (roughly corresponding to the tidal radius). This distance modulus is close to, but significantly better determined than, that derived from recent high-precision radial velocity studies, somewhat larger than that indicated by recent ground-based trigonometric parallax determinations, and smaller than those found from recent studies of the cluster convergent point. These discrepancies are investigated and explained.
- 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.
