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2781. HST survey of ONC in H20 1.4um abs. band. I.
ID:
ivo://CDS.VizieR/J/ApJ/896/79
Title:
HST survey of ONC in H20 1.4um abs. band. I.
Short Name:
J/ApJ/896/79
Date:
11 Mar 2022
Publisher:
CDS
Description:
In order to obtain a complete census of the stellar and substellar population, down to a few M_Jup_ in the ~1Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4{mu}m H2O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m130=14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen- burning limit mass (M~0.072M_{sun}_) at ~1Myr. Of these, however, only 742 sources have a negative F130M-F139N color index, indicative of the presence of H2O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T<~2850K at an assumed 1Myr cluster age. On our color-magnitude diagram (CMD), this population of sources with H2O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M-F139N color index and can be traced down to the sensitivity limit of our survey, m130~21.5, corresponding to a 1Myr old ~3M_Jup_ planetary-mass object under about 2mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ~1M_Jup_ fail to reproduce the observed H2O color index at M<~20M_Jup_. We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.
2782. HST survey of young clusters in M31. III.
ID:
ivo://CDS.VizieR/J/AJ/138/1667
Title:
HST survey of young clusters in M31. III.
Short Name:
J/AJ/138/1667
Date:
21 Oct 2021
Publisher:
CDS
Description:
Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fitted to two types of models to determine the clusters' structural properties. The clusters are primarily young (~108yr) and massive (~104.5M_{sun}_), with median half-light radius 7pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane (FP) relations as old clusters; if confirmed with velocity dispersion measurements, this would be a strong indication that the star cluster FP reflects universal cluster formation conditions.
2783. HST Treasury Program on the ONC
ID:
ivo://CDS.VizieR/J/ApJS/207/10
Title:
HST Treasury Program on the ONC
Short Name:
J/ApJS/207/10
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Hubble Space Telescope (HST) Treasury Program on the Orion Nebula Cluster (ONC) has used 104 orbits of HST time to image the Great Orion Nebula region with the Advanced Camera for Surveys (ACS), the Wide-Field/Planetary Camera 2 (WFPC2), and the Near-Infrared Camera and Multi-Object Spectrograph (NICMOS) instrument in 11 filters ranging from the U band to the H band equivalent of HST. The program has been intended to perform the definitive study of the stellar component of the ONC at visible wavelengths, addressing key questions like the cluster initial mass function, age spread, mass accretion, binarity, and circumstellar disk evolution. The scanning pattern allowed us to cover a contiguous field of approximately 600 arcmin2 with both ACS and WFPC2, with a typical exposure time of approximately 11 minutes per ACS filter, corresponding to a point source depth AB(F435W) = 25.8 and AB(F775W) = 25.2 with 0.2 mag of photometric error. We describe the observations, data reduction, and data products, including images, source catalogs, and tools for quick look preview. In particular, we provide ACS photometry for 3399 stars, most of them detected at multiple epochs; WFPC2 photometry for 1643 stars, 1021 of them detected in the U band; and NICMOS JH photometry for 2116 stars. We summarize the early science results that have been presented in a number of papers.
2784. HST UBVI photometry of NGC 3081 inner regions
ID:
ivo://CDS.VizieR/J/AJ/127/1982
Title:
HST UBVI photometry of NGC 3081 inner regions
Short Name:
J/AJ/127/1982
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Hubble Space Telescope Wide Field Planetary Camera 2 images of the inner regions of NGC 3081, an absolute magnitude M_B_=-20.0 early-type barred spiral having four well-defined resonance rings: a nuclear ring, an inner ring, an outer R_1_ ring, and an outer R'_2_ pseudoring. Here we focus on a photometric study of the inner ring, a feature likely associated with an inner 4:1 resonance near the ends of the bar. The ring is notable for its high contrast and sharp definition, which is due to a significant degree of active star formation. The ring is also notable for its significant intrinsic elongation and parallel alignment with the bar.
2785. HST UVI photometry of M15. II.
ID:
ivo://CDS.VizieR/J/AJ/107/1745
Title:
HST UVI photometry of M15. II.
Short Name:
J/AJ/107/1745
Date:
21 Oct 2021
Publisher:
CDS
Description:
The projected density distribution of resolved stars near the center of M15 is shown to be consistent with either a power-law cusp N(r) ~ r^{alpha}^, with {alpha} ~ -0.85+/-0.2, or with a King model with a core of radius <~ 2" (best fit r(core)=1.3"). The inferred slope is in agreement with the theoretical value, {alpha}=-0.75, calculated by Bahcall and Wolf for the distribution of equal-mass stars surrounding a massive black hole and is also consistent with the radial profile expected from core collapse without a central black hole. The object AC 214 is a candidate for the central density cusp. Analysis of Monte Carlo simulations of the diffuse light indicates that, using current analysis techniques and available data, the residual light is not a reliable indicator of the true density distribution. This is contrary to earlier work. Photometric measurements in V and I of more than 5x10^3^ stars (and in U, V, and I of >~1500 stars) are used to construct color-magnitude diagrams in the central 1' of M15. Fourteen blue straggler candidates are identified in the inner 20". The central color gradient noticed by previous researchers is caused by a central depletion of bright red giant stars rather than an excess of blue stragglers or blue horizontal branch stars.
2786. HST UV-IR photometry in CLASH galaxy clusters
ID:
ivo://CDS.VizieR/J/ApJ/848/37
Title:
HST UV-IR photometry in CLASH galaxy clusters
Short Name:
J/ApJ/848/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new method for photometering objects in galaxy clusters. We introduce a mode-filtering technique for removing spatially variable backgrounds, improving both detection and photometric accuracy (roughly halving the scatter in the red sequence compared to previous catalogs of the same clusters). This method is based on robustly determining the distribution of background pixel values and should provide comparable improvement in photometric analysis of any crowded fields. We produce new multiwavelength catalogs for the 25 CLASH cluster fields in all 16 bandpasses from the UV through the near-IR, as well as rest-frame magnitudes. A comparison with spectroscopic values from the literature finds a ~30% decrease in the redshift deviation from previously released CLASH photometry. This improvement in redshift precision, in combination with a detection scheme designed to maximize purity, yields a substantial upgrade in cluster member identification over the previous CLASH galaxy catalog. We construct luminosity functions for each cluster, reliably reaching depths of at least 4.5mag below M* in every case, and deeper still in several clusters. We measure M* , {alpha}, and their redshift evolution, assuming the cluster populations are coeval, and find little to no evolution of {alpha}{<~}-0.9<~{alpha}{<~}-0.8, and M* values consistent with passive evolution. We present a catalog of galaxy photometry, photometric and spectroscopic redshifts, and rest-frame photometry for the full fields of view of all 25 CLASH clusters. Not only will our new photometric catalogs enable new studies of the properties of CLASH clusters, but mode-filtering techniques, such as those presented here, should greatly enhance the data quality of future photometric surveys of crowded fields.
2787. HST UV,V,I photometry of NGC7673 star clusters
ID:
ivo://CDS.VizieR/J/A+A/391/857
Title:
HST UV,V,I photometry of NGC7673 star clusters
Short Name:
J/A+A/391/857
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate the star cluster system in the starburst galaxy NGC 7673 using archival Hubble Space Telescope WFPC2 broad-band images. For the first time we are able to examine the internal structures of the prominent optical clumps in this galaxy. The clumps are composed of young stars, 16-33% of which are in bright star clusters. We identify 268 star cluster candidates in both the F555W and F814W images, and 50 clusters with the F255W filter. These data allow us to estimate ages and masses using color-magnitude and two-color diagrams for our sample. We find a population of young, <6Myr clusters located throughout the galaxy with concentrations in the clumps. Star cluster mass estimates are 5-50x10^4^M_{sun}_ for the brightest objects. The starburst remains active in physically well-separated regions, indicating a widespread starburst trigger. We discuss clump lifetimes, their implications for the future evolution of NGC 7673, and possible relationships to high redshift starbursts.
2788. HST view of YSOs in the LMC
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.
2789. HST VI photometry and proper motions in NGC 6528
ID:
ivo://CDS.VizieR/J/A+A/385/67
Title:
HST VI photometry and proper motions in NGC 6528
Short Name:
J/A+A/385/67
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using two epochs of HST/WFPC2 images of the metal-rich globular cluster NGC 6528 we derive the proper motions of the stars and use them to separate the stars belonging to NGC 6528 from those of the Galactic bulge. The stellar sequences in the resulting colour-magnitude diagram for the cluster are significantly better determined than in previously published data. From comparison of the colour-magnitude diagram with the fiducial line for NGC 6553 from Zoccali et al. (2001AJ....121.2638Z) we conclude that the two globular clusters have the same age. Further, using alpha-enhanced stellar isochrones, NGC 6528 is found to have an age of 11+/-2Gyr. This fitting of isochrones also give that the cluster is 7.2kpc away from us. From the measured velocities both the proper motion of the cluster and the velocity dispersion in the Galactic bulge are found. NGC 6528 is found to have a proper motion relative to the Galactic bulge of <mu_l_>=0.006 and <mu_b_>=0.044 arcsec per century. Using stars with 14<V_555_<19 (i.e. the red giant branch and horizontal branch) we find, for the Galactic bulge, sigma_l_=0.33+/-0.03 and sigma_b_=0.25+/-0.02 arcsec per century. This give sigma_l/sigma_b=1.32+/-0.16, consistent both with previous proper motion studies of K giants in the Galactic bulge as well as with predictions by models of the kinematics of bulge stars.
2790. HST VI photometry of Bol 514 in M31
ID:
ivo://CDS.VizieR/J/A+A/473/429
Title:
HST VI photometry of Bol 514 in M31
Short Name:
J/A+A/473/429
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the density profile of the remote M 31 globular cluster B514, obtained from HST/ACS observations.