- ID:
- ivo://CDS.VizieR/J/ApJ/766/20
- Title:
- HST photometry of star clusters in M82
- Short Name:
- J/ApJ/766/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of star clusters in the nearby starburst galaxy M82 based on the UBVI-, YJ- and H-band Hubble Space Telescope images. We find 1105 star clusters with V<23mag. Of those, 1070 are located in the disk region, while 35 star clusters are in the halo region. The star clusters in the disk are composed of a dominant blue population with a color peak at (B-V)_0_~0.45, and a weaker red population. The luminosity function of the disk clusters shows a power-law distribution with a power-law index {alpha}=-2.04+/-0.03, and the scale height of their distribution is h_z_=9.64"+/-0.40" (164+/-7pc), similar to that of the stellar thin disk of M82. We have derived the ages of ~630 star clusters using the spectral energy distribution fit method by comparing UBVI(YJ)H-band photometric data with the simple stellar population models. The age distribution of the disk clusters shows that the most dominant cluster population has ages ranging from 100Myr to 1Gyr, with a peak at about 500Myr. This suggests that M82 has undergone a disk-wide star formation about 500Myr ago, probably through the interaction with M81. The brightest star clusters in the nuclear region are much brighter than those in other regions, indicating that more massive star clusters are formed in the denser environments. On the other hand, the colors of the halo clusters are similar to those of globular clusters in the Milky Way, and their ages are estimated to be older than 1Gyr. These are probably genuine old globular clusters in M82.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/122/3046
- Title:
- HST photometry of star clusters in NGC 5236
- Short Name:
- J/AJ/122/3046
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric catalog of 45 massive star clusters in the nuclear starburst of M83 (NGC 5236), observed with the Hubble Space Telescope Wide Field Planetary Camera 2, in both broadband (F300W, F547M, and F814W) and narrowband (F656N and F487N) filters, in two separate visits one week apart during April and May 2000 .
- ID:
- ivo://CDS.VizieR/J/AJ/151/23
- Title:
- HST photometry of stars in HD 97950
- Short Name:
- J/AJ/151/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use photometry in the F220W, F250W, F330W, F435W filters from the High Resolution Channel of the Advanced Camera for Surveys and photometry in the F555W, F675W, and F814W filters from the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope to derive individual stellar reddenings and extinctions for stars in the HD97950 cluster in the giant HII region NGC 3603. The mean line of sight reddening for about a hundred main-sequence member stars inside the cluster is E(F435W-F555W)=1.33+/-0.12mag. After correcting for foreground reddening, the total to selective extinction ratio is R_F555W_=3.75+/-0.87 in the cluster. Within the standard deviation associated with E({lambda}-F555W)/E(F435W-F555W) in each filter, the cluster extinction curve at ultraviolet wavelengths tends to be grayer than the average Galactic extinction laws from Cardelli et al. and Fitzpatrick. It is closer to the extinction law derived by Calzetti et al. for starburst galaxies, where the 0.2175{mu}m bump is absent. This indicates an anomalous extinction in the HD97950 cluster, which may due to the clumpy dust distribution within the cluster, and the size of dust grains being larger than the average Galactic ISM.
- ID:
- ivo://CDS.VizieR/J/A+A/381/941
- Title:
- HST photometry of stars in N160A
- Short Name:
- J/A+A/381/941
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using high-resolution imaging with the Hubble Space Telescope, we study the Large Magellanic Cloud 2 region N160A and uncover several striking features of this complex massive star-forming site. The two compact high excitation 2 blobs (HEBs) A1 and A2 are for the first time resolved and their stellar content and morphology is revealed. A1, being of higher excitation, is powered by a single massive star whose strong wind has created a surrounding bubble. A2 harbors several exciting stars enshrouded by large quantities of dust. The whole N160A nebula is energized by three star clusters for which we obtain photometry and study their color-magnitude diagram. The 2 region is particularly dusty, with extinction values reaching an A_V_~2.5mag in the visible, and it is separated from the molecular cloud by an outstanding ionization front. A previously detected infrared young stellar object is also accurately located with respect to the 2 region (N160A).
- ID:
- ivo://CDS.VizieR/J/AJ/136/2259
- Title:
- HST photometry of stars in NGC 2419
- Short Name:
- J/AJ/136/2259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of optical and ultraviolet Hubble Space Telescope photometry for evolved stars in the core of the distant massive globular cluster NGC 2419. We characterize the horizontal branch (HB) population in detail including corrections for incompleteness on the long blue tail. The majority of the HB stars can be identified with two main groups (one slightly bluer than the instability strip, and the other at the extreme end of the HB). We present a method for removing (to first-order) lifetime effects from the distribution of HB stars to facilitate more accurate measurements of helium abundance for clusters with blue HBs and to clarify the distribution of stars reaching the zero-age HB.
- ID:
- ivo://CDS.VizieR/J/ApJ/673/143
- Title:
- HST photometry of TN J1338-1942
- Short Name:
- J/ApJ/673/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep HST ACS observations in g_475_r_625_i_775_z_850_ toward the z=4.1 radio galaxy TN J1338-1942 and its overdensity of >30 spectroscopically confirmed Ly{alpha} emitters (LAEs). We select 66 g_475_ band dropouts to z_850,5sigma_=27, 6 of which are also LAEs.
- ID:
- ivo://CDS.VizieR/J/AJ/133/917
- Title:
- HST photometry of two NGC 4214 clusters
- Short Name:
- J/AJ/133/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the data and methods that we have used to perform a detailed UV-optical study of the nearby dwarf starburst galaxy NGC 4214 using multifilter Hubble Space Telescope WFPC2 and STIS photometry. We explain the process followed to obtain high-quality photometry and astrometry of the stellar and cluster populations of this galaxy. We describe the procedure used to transform magnitudes and colors into physical parameters using spectral energy distributions. The data show the existence of both young and old stellar populations that can be resolved at the distance of NGC 4214 (2.94Mpc), and we perform a general description of those populations.
- ID:
- ivo://CDS.VizieR/J/ApJS/128/99
- Title:
- HST photometry of 4 Virgo LSB galaxies
- Short Name:
- J/ApJS/128/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the F814W and F300W filters, Hubble Space Telescope Wide Field Planetary Camera-2 (WFPC2) images were taken of four low surface brightness galaxies in the direction of the Virgo Cluster - V7L3, V2L8, V1L4, and Malin 1. The high resolution of the WFPC2 combined with the extremely diffuse nature of the four galaxies makes them essentially transparent, allowing for the serendipitous discovery of 139 background galaxies visible through both the disks and nuclei of the foreground galaxies. Surface photometry was done on the newly discovered galaxies through the F814W (I-band) filter. The detected galaxies have both r1/4 and exponential-type profiles with radii (to the {mu}_F814W_=25.0mag/arcsec^2^ limit) less than 5.0". Their total magnitudes range from 18.9 through the survey cutoff at 25.0 in the F814W filter.
- ID:
- ivo://CDS.VizieR/J/AJ/144/142
- Title:
- HST photometry of young stellar populations in M31
- Short Name:
- J/AJ/144/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied the young stellar populations of 22 star-forming regions in the Andromeda galaxy (M31), with Hubble Space Telescope (HST) multi-band imaging from far-UV to I. The regions were selected from Galaxy Evolution Explorer (GALEX) wide-field far-UV imaging; they sample different environments and galactocentric distances from 6 to 22kpc. They were imaged with 30 HST fields (360 distinct images, in six bandpasses), with a pixel scale of 0.38pc projected on the sky, at the distance of M31. This study is part of HST treasury survey program HST-GO-11079, which includes star-forming regions in eight Local Group galaxies. We provide a merged catalog of six-band stellar photometry in the 30 M31 fields, containing 118036 sources brighter than V and B~23mag. Each HST field covers about 0.3kpc^2^ in M31, and contains up to ~7000 stars, of which the number varies by a factor of >7 among the target regions; a large fraction of the sample are hot massive stars, due to our choice of filters and exposures. We derived stellar physical parameters and interstellar extinction for individual sources by spectral energy distribution analysis with model-atmosphere colors, and used the results to infer ages, massive stars content, and extinction of the star-forming regions. Reddening is up to E(B-V)<~0.6mag in some OB associations, and lowest in the outermost regions (average of <~0.12mag in OB184 at 21.9kpc). We examined the spatial distribution (clustering) of the hot massive stars, and defined OB associations on various spatial scales from compact to wider, more spread out ones. A hierarchical structuring is observed, with small compact groups arranged within large complexes. Their areas vary from less than 10 to 10^5^pc^2^, and masses are up to {approx}10^5^M_{sun}_, in the scales sampled by our analysis. Their cumulative mass distribution follows a power law, at least in part of the sampled regime. Hot-star counts in the young regions compare very well with integrated measurements of UV flux from GALEX.
- ID:
- ivo://CDS.VizieR/J/ApJ/861/99
- Title:
- HSTPROMO cat. VI. Improved analysis of NGC362
- Short Name:
- J/ApJ/861/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an improved data-reduction technique to obtain high-precision proper motions (PMs) of globular clusters (GCs) using Hubble Space Telescope data. The new reduction is superior to the one presented in the first paper of this series for the faintest sources in very crowded fields. We choose the GC NGC 362 as a benchmark to test our new procedures. We measure PMs of 117450 sources in the field, showing that we are able to obtain a PM precision better than 10{mu}as/yr for bright stars. We make use of this new PM catalog of NGC 362 to study the cluster's internal kinematics. We investigate the velocity dispersion profiles of the multiple stellar populations hosted by NGC 362 and find new pieces of information on the kinematics of first- and second- generation stars. We analyze the level of energy equipartition of the cluster and find direct evidence for its post-core-collapsed state from kinematic arguments alone. We refine the dynamical mass of the blue stragglers (BSs) and study possible kinematic differences between BSs formed by collisions and mass transfer. We also measure no significant cluster rotation in the plane of the sky. Finally, we measure the absolute PM of NGC 362 and of the background stars belonging to the Small Magellanic Cloud, finding a good agreement with previous estimates in the literature. We make the PM catalog publicly available.
