- ID:
- ivo://CDS.VizieR/J/ApJ/703/42
- Title:
- HST photometry of M87 globular clusters
- Short Name:
- J/ApJ/703/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the M87 GC system using deep, archival HST/ACS imaging with the F606W and F814W filters, in which we find a significant color-magnitude relation for the metal-poor globular clusters (GCs). The slope of this relation in the I versus V-I color-magnitude diagram ({gamma}_I_=-0.024+/-0.006) is perfectly consistent with expectations based on previously published results using data from the ACS Virgo Cluster Survey. We show that previously measured half-light radii of M87 GCs from best-fit PSF-convolved King models are consistent with the more accurate measurements in this study, and we also explain how the color-magnitude relation for metal-poor GCs is real and cannot be an artifact of the photometry. We fit Gaussian and evolved Schechter functions to the luminosity distribution of GCs across all colors, as well as divided into blue and red subpopulations, finding that the blue GCs have a brighter mean luminosity and a narrower distribution than the red GCs. Finally, we present a catalog of astrometry and photometry for 2250 M87 GCs.
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- ID:
- ivo://CDS.VizieR/J/A+A/544/A155
- Title:
- HST photometry of M31 globular clusters
- Short Name:
- J/A+A/544/A155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have derived a new calibration of the MV(HB)-[Fe/H] relation by exploiting the large photometric database of old GCs in M31 in the HST archive. We collected BVI data for 48 old GCs in M31 and analysed them by applying the same methods and procedures to all objects. We obtained a set of homogeneous colour-magnitude diagrams (CMDs) that were best-fitted with the fiducial CMD ridge lines of selected Milky Way template GCs. Reddening, metallicity, horizontal branch (HB) luminosity and distance were determined self-consistently for each cluster. There are three main results of this study: i) the relation MV(HB)=0.25(+/-0.02)[Fe/H]+0.89(+/-0.03), which is obtained from the above parameters and is calibrated on the distances of the template Galactic GCs; ii) the distance modulus to M31 of (m-M)_0_=24.42+/-0.06mag, that is the first determination of the distance to M31 based on the characteristics of its GC system, and is calibrated on Galactic GCs, iii) the distance to the Large Magellanic Cloud (LMC), which is estimated to be 18.54+/-0.07mag as a consequence of the previous results.
- ID:
- ivo://CDS.VizieR/J/ApJ/768/137
- Title:
- HST photometry of M84 globular clusters
- Short Name:
- J/ApJ/768/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Color distributions of globular clusters (GCs) in most massive galaxies are bimodal. Assuming linear color-to-metallicity conversions, bimodality is viewed as the presence of merely two GC subsystems with distinct metallicities, which serves as a critical backbone of various galaxy formation theories. Recent studies, however, revealed that the color-metallicity relations (CMRs) often used to derive GC metallicities (e.g., CMRs of g-z, V-I, and C-T_1_) are in fact inflected. Such inflection can create bimodal color distributions if the underlying GC metallicity spread is simply broad as expected from the hierarchical merging paradigm of galaxy formation. In order to test the nonlinear-CMR scenario for GC color bimodality, the u-band photometry is proposed because the u-related CMRs (e.g., CMRs of u-g and u-z) are theoretically predicted to be least inflected and most distinctive among commonly used optical CMRs. Here, we present Hubble Space Telescope (HST)/WFC3 F336W (u-band) photometry of the GC system in M84, a giant elliptical in the Virgo galaxy cluster. Combining the u data with the existing HST ACS/WFC g and z data, we find that the u-z and u-g color distributions are different from the g-z distribution in a very systematic manner and remarkably consistent with our model predictions based on the nonlinear-CMR hypothesis. The results lend further confidence to the validity of the nonlinear-CMR scenario as an explanation for GC color bimodality. There are some GC systems showing bimodal spectroscopic metallicity, and in such systems the inflected CMRs often create stronger bimodality in the color domain.
- ID:
- ivo://CDS.VizieR/J/AcA/59/47
- Title:
- HST photometry of M33 stellar clusters
- Short Name:
- J/AcA/59/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used deep ACS/WFC images of M33 to check the nature of extended objects detected by the ground based survey of Zloczewski et al. (2008, Cat. J/AcA/58/23). A total of 24 candidates turned out to be genuine compact stellar clusters. In addition we detected 91 new clusters. Equatorial coordinates, integrated magnitudes and angular sizes are listed for all 115 objects. Forty-two clusters have sufficiently red colors to be candidates for old globulars. For four clusters we extracted resolved stellar photometry. Object 33-3-018 located in the outer disk of M33 turned out to be a young cluster with an age estimated at 200-350Myr. Cluster ZK-90 has an age of 3-5Gyr. The remaining two clusters have intermediate ages ranging from one to a few Gyr.
- ID:
- ivo://CDS.VizieR/J/AJ/141/126
- Title:
- HST photometry of NGC 5471
- Short Name:
- J/AJ/141/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We show that star formation in the giant HII region NGC 5471 has been ongoing during the past 100 Myr. Using Hubble Space Telescope/Wide-Field Planetary Camera 2 F547M and F675W, ground-based JHKs, and GALEX FUV and NUV images, we have conducted a photometric study of the star formation history (SFH) in the massive giant extragalactic HII region NGC 5471 in M101. We perform a photometric study of the color-magnitude diagram (CMD) of the resolved stars and an integrated analysis of the main individual star-forming clusters and of NGC 5471 as a whole.
- ID:
- ivo://CDS.VizieR/J/AJ/142/129
- Title:
- HST photometry of NGC 4449 clusters
- Short Name:
- J/AJ/142/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the star cluster population in the starburst irregular galaxy NGC 4449 based on B, V, I, and H{alpha} images taken with the Advanced Camera for Surveys on the Hubble Space Telescope. We derive cluster properties such as size, ellipticity, and total magnitude. Cluster ages and masses are derived fitting the observed spectral energy distributions with different population synthesis models.
- ID:
- ivo://CDS.VizieR/J/ApJ/668/209
- Title:
- HST photometry of NGC 5866 globulars
- Short Name:
- J/ApJ/668/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a detailed study of the globular cluster (GC) system in the galaxy NGC 5866 based on F435W, F555W, and F625W (~B, V, and R) Hubble Space Telescope Advanced Camera for Surveys images. Adopting color, size, and shape selection criteria, the final list of GC candidates comprises 109 objects, with small estimated contamination from background galaxies, and foreground stars.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A7
- Title:
- HST photometry of Sculptor group dwarf galaxies
- Short Name:
- J/A+A/550/A7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We focus on the resolved stellar populations of one early-type and four transition-type dwarf galaxies in the Sculptor group, with the aim to examine the potential presence of population gradients and place constraints on their mean metallicities. We use deep Hubble Space Telescope images to construct color-magnitude diagrams, from which we select stellar populations that trace different evolutionary phases in order to constrain their range of ages and metallicities, as well as to examine their spatial distribution. In addition, we use the resolved stars in the red giant branch in order to derive photometric metallicities.
- 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.
- 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 .
