- ID:
- ivo://CDS.VizieR/J/A+A/643/A116
- Title:
- HR study of massive supergiants in Per OB1
- Short Name:
- J/A+A/643/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Perseus OB1 association, including the h and chi Persei double cluster, is an interesting laboratory for the investigation of massive star evolution as it hosts one of the most populous groupings of blue and red supergiants (Sgs) in the Galaxy at a moderate distance and extinction. We discuss whether the massive O-type, and blue and red Sg stars located in the Per OB1 region are members of the same population, and examine their binary and runaway status. We gathered a total of 405 high-resolution spectra for 88 suitable candidates around 4.5 deg from the center of the association, and compiled astrometric information from Gaia DR2 for all of them. This was used to investigate membership and identify runaway stars. By obtaining high-precision radial velocity (RV) estimates for all available spectra, we investigated the RV distribution of the global sample (as well as different subsamples) and identified spectroscopic binaries (SBs). Most of the investigated stars belong to a physically linked population located at d=2.5+/-0.4kpc. We identify 79 confirmed or likely members, and 5 member candidates. No important differences are detected in the distribution of parallaxes when stars in h and chi Persei or the full sample are considered. In contrast, most O-type stars seem to be part of a differentiated population in terms of kinematical properties. In particular, the percentage of runaways among them (45%) is considerable higher than for the more evolved targets (which is lower than ~5% in all cases). A similar tendency is also found for the percentage of clearly detected SBs, which already decreases from 15% to 10% when the O star and B Sg samples are compared, respectively, and practically vanishes in the cooler Sgs. Concerning this latter result, our study illustrates the importance of taking the effect of the ubiquitous presence of intrinsic variability in the blue-to-red Sg domain into account to avoid the spurious identification of pulsating stars as SBs. All but 4 stars in our working sample (including 10 O giants/Sgs, 36 B Sgs, 9 B giants, 11 A/F Sgs, and 18 red Sgs) can be considered as part of the same (interrelated) population. However, any further attempt to describe the empirical properties of this sample of massive stars in an evolutionary context must take into account that an important fraction of the O stars is or likely has been part of a binary/multiple system. In addition, some of the other more evolved targets may have also been affected by binary evolution. In this line of argument, it is also interesting to note that the percentage of spectroscopic binaries within the evolved population of massive stars in Per OB1 is lower by a factor 4-5 than in the case of dedicated surveys of O-type stars in other environments that include a much younger population of massive stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/2385
- Title:
- HST/ACS Coma Cluster Survey. X.
- Short Name:
- J/MNRAS/445/2385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present scaling relations between structural properties of nuclear star clusters and their host galaxies for a sample of early-type dwarf galaxies observed as part of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Coma Cluster Survey. We have analysed the light profiles of 200 early-type dwarf galaxies in the magnitude range 16.0<m_F814W_<22.6mag, corresponding to -19.0<M_F814W_<-12.4mag. Nuclear star clusters are detected in 80 percent of the galaxies, thus doubling the sample of HST-observed early-type dwarf galaxies with nuclear star clusters. We confirm that the nuclear star cluster detection fraction decreases strongly towards faint magnitudes. The luminosities of nuclear star clusters do not scale linearly with host galaxy luminosity. A linear fit yields L_nuc_~L_gal_^0.57^+/-0.05. The nuclear star cluster-host galaxy luminosity scaling relation for low-mass early-type dwarf galaxies is consistent with formation by globular cluster (GC) accretion. We find that at similar luminosities, galaxies with higher Sersic indices have slightly more luminous nuclear star clusters. Rounder galaxies have on average more luminous clusters. Some of the nuclear star clusters are resolved, despite the distance of Coma. We argue that the relation between nuclear star cluster mass and size is consistent with both formation by GC accretion and in situ formation. Our data are consistent with GC inspiralling being the dominant mechanism at low masses, although the observed trend with Sersic index suggests that in situ star formation is an important second-order effect.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/290
- Title:
- HST/ACS photometry in the SMC
- Short Name:
- J/ApJ/681/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our photometric study of the stellar association NGC 602 in the wing of the Small Magellanic Cloud (SMC). The data were taken in the filters F555W and F814W using the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). Photometry was performed using the ACS module of the stellar photometry package DOLPHOT. We detected more than 5500 stars with a magnitude range of 14<~m_555_<~28mag. Three prominent stellar concentrations are identified with star counts in the observed field, the association NGC 602 itself, and two clusters, one of them not being currently in any known catalog. The color-magnitude diagrams (CMDs) of both clusters show features typical for young open clusters, while that of the association reveals bright main-sequence (MS) and faint pre-main-sequence (PMS) stars as the members of the system.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/2937
- Title:
- HST BVI catalogue of star clusters in 5 HCGs
- Short Name:
- J/MNRAS/449/2937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric catalogue of star cluster candidates in Hickson compact groups (HCGs) 7, 31, 42, 59, and 92, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. The catalogue contains precise cluster positions (right ascension and declination), magnitudes, and colours in the BVI filters. The number of detected sources ranges from 2200 to 5600 per group, from which we construct the high-confidence sample by applying a number of criteria designed to reduce foreground and background contaminants. Furthermore, the high-confidence cluster candidates for each of the 16 galaxies in our sample are split into two subpopulations: one that may contain young star clusters and one that is dominated by globular older clusters. The ratio of young star cluster to globular cluster candidates varies from group to group, from equal numbers to the extreme of HCG 31 which has a ratio of 8 to 1, due to a recent starburst induced by interactions in the group. We find that the number of blue clusters with M_V_<-9 correlates well with the current star formation rate in an individual galaxy, while the number of globular cluster candidates with M_V_<-7.8 correlates well (though with large scatter) with the stellar mass. Analyses of the high-confidence sample presented in this paper show that star clusters can be successfully used to infer the gross star formation history of the host groups and therefore determine their placement in a proposed evolutionary sequence for compact galaxy groups.
- ID:
- ivo://CDS.VizieR/J/AJ/122/1330
- Title:
- HST BVI photometry of M 81 star clusters
- Short Name:
- J/AJ/122/1330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the discovery of 114 compact star clusters in the nearby spiral galaxy M81 from B-, V-, and I-band Hubble Space Telescope Wide Field Planetary Camera 2 imaging in eight fields, covering a total area of ~40arcmin^2^. The fields sample a variety of environments (both spiral and interarm regions), as well as a range of projected galactocentric distances from 2 to 12kpc. The sample is complete to V~22, deeper by ~1mag than any previous cluster survey in M81. We present details of the separation of clusters from both stellar sources and background galaxies, which has been based solely on structural parameters and morphology and not using any color cuts, as is necessary for ground-based surveys. We present magnitudes and colors of detected clusters. Surface brightness profiles are compared with single-mass King models, giving a range of core radii for the clusters in our sample between 0.2 and 7pc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/1049
- Title:
- HST gz magnitude of NGC 1023 star clusters
- Short Name:
- J/MNRAS/442/1049
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Faint fuzzies (FFs) are a relatively new class of star cluster, first found in the nearby S0 galaxy NGC 1023 by Larsen & Brodie (2000AJ....120.2938L) using Wide Field Planetary Camera 2 (WFPC2) images from the Hubble Space Telescope (HST). Here, we investigate the star cluster system of NGC 1023 using an eight pointing mosaic of Advanced Camera for Surveys (ACS) images from HST. We identify blue and red normal globular clusters (two of which are particularly luminous and dense) and two ultracompact dwarf objects (with effective radius ~10pc). With our more complete spatial coverage, we also find 81 red and 27 blue FFs. We confirm the association of the red FFs with the disc of NGC 1023, consistent with them being long-lived open clusters. Half of the blue FFs appear to be associated with the dwarf satellite galaxy NGC 1023A (which was largely absent from the original HST/WFPC2 coverage), while the remainder are spatially coincident with the densest HI gas that surrounds NGC 1023. The blue FFs have colours that are consistent with young (few 100Myr old) star clusters that formed during the most recent interaction between NGC 1023 and its satellite NGC 1023A.
- ID:
- ivo://CDS.VizieR/J/A+A/532/A147
- Title:
- HST photometry in extragalactic star clusters
- Short Name:
- J/A+A/532/A147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present colour-magnitude diagrams (CMDs) for a sample of seven young massive clusters in the galaxies NGC 1313, NGC 1569, NGC 1705 and NGC 5236. The clusters have ages in the range 5-50 million years and masses of 10^5^-10^6^M_{sun}_. Although crowding prevents us from obtaining photometry in the inner regions of the clusters, we are still able to measure up to 30-100 supergiant stars in each of the richest clusters, along with the brighter main sequence stars. The resulting CMDs and luminosity functions are compared with photometry of artificially generated clusters, designed to reproduce the photometric errors and completeness as realistically as possible. In agreement with previous studies, our CMDs show no clear gap between the H-burning main sequence and the He-burning supergiant stars, contrary to predictions by common stellar isochrones. In general, the isochrones also fail to match the observed number ratios of red-to-blue supergiant stars, although the difficulty of separating blue supergiants from the main sequence complicates this comparison. In several cases we observe a large spread (1-2mag) in the luminosities of the supergiant stars that cannot be accounted for by observational errors. This spread can be reproduced by including an age spread of 10-30 million years in the models. However, age spreads cannot fully account for the observed morphology of the CMDs and other processes, such as the evolution of interacting binary stars, may also play a role.
- ID:
- ivo://CDS.VizieR/J/ApJ/672/914
- Title:
- HST photometry in NGC 346
- Short Name:
- J/ApJ/672/914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the third part of our photometric study of the star-forming region NGC 346/N66 and its surrounding field in the Small Magellanic Cloud (SMC), we focus on the large number of low-mass pre-main-sequence (PMS) stars revealed by the Hubble Space Telescope observations with the Advanced Camera for Surveys. We investigate the origin of the observed broadening of the PMS population in the V-I,V color-magnitude diagram. The most likely explanations are either the presence of differential reddening or an age spread among the young stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/603/503
- Title:
- HST photometry in NGC 5253 and NGC 3077
- Short Name:
- J/ApJ/603/503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multicolor photometry of bright star cluster candidates in the nearby starburst galaxies NGC 3077 and NGC 5253, observed with the Hubble Space Telescope Wide Field Planetary Camera 2 in both broadband (F300W, F547M, and F814W) and narrowband (F487N and F656N) filters on three visits between 1996 and 2001. By comparing the photometry with theoretical population synthesis models, we estimate the age and mass of each star cluster, which provides constraints on the recent star formation histories of the host galaxies. We compare the star cluster populations in these dwarf starburst galaxies with those of the nuclear starburst in the barred spiral M83 and discuss the implications for our understanding of the nature and evolution of starburst events.
- ID:
- ivo://CDS.VizieR/J/AJ/143/16
- Title:
- HST photometry of IC 883 star clusters
- Short Name:
- J/AJ/143/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New optical Hubble Space Telescope (HST), Spitzer Space Telescope, Galaxy Evolution Explorer, and Chandra observations of the single-nucleus, Luminous InfraRed Galaxy (LIRG) merger IC 883 are presented. The galaxy is a member of the Great Observatories All-sky LIRG Survey (GOALS) and is of particular interest for a detailed examination of a luminous late-stage merger due to the richness of the optically visible star clusters and the extended nature of the nuclear X-ray, mid-IR, CO, and radio emission. In the HST Advanced Camera for Surveys images, the galaxy is shown to contain 156 optically visible star clusters distributed throughout the nuclear regions and tidal tails of the merger, with a majority of visible clusters residing in an arc ~3-7kpc from the position of the mid-infrared core of the galaxy. The luminosity functions of the clusters have an {alpha}_F435W_~-2.17 +/-0.22 and {alpha}_F814W_~-2.01+/-0.21, compared with V-band-derived values measured for the well-studied LIRG NGC 34 and the Antennae Galaxy of {alpha}~-1.7+/-0.1 and -2.13+/-0.07, respectively.
