- ID:
- ivo://CDS.VizieR/J/A+A/637/A40
- Title:
- HMSCs classification and physical parameters
- Short Name:
- J/A+A/637/A40
- Date:
- 07 Dec 2021 10:47:33
- Publisher:
- CDS
- Description:
- The role of ionization feedback on high-mass (>8M_{sun}_) star formation is still highly debated. Questions remain concerning the presence of nearby HII regions changes the properties of early high-mass star formation and whether H ii regions promote or inhibit the formation of high-mass stars. To characterize the role of HII regions on the formation of high-mass stars, we study the properties of a sample of candidates high-mass starless clumps (HMSCs), of which about 90% have masses larger than 100 Msun. These high-mass objects probably represent the earliest stages of high-mass star formation; we search if (and how) their properties are modified by the presence of an HII region. We took advantage of the recently published catalog of HMSC candidates. By cross matching the HMSCs and HII regions, we classified HMSCs into three categories: 1) The HMSCs associated with HII regions both in the position in the projected plane of the sky and in velocity; 2) HMSCs associated in the plane of the sky, but not in velocity; and 3) HMSCs far away from any HII regions in the projected sky plane. We carried out comparisons between associated and non-associated HMSCs based on statistical analyses of multiwavelength data from infrared to radio. We show that there are systematic differences of the properties of HMSCs in different environments. Statistical analyses suggest that HMSCs associated with HII regions are warmer, more luminous, more centrally-peaked and turbulent. We also clearly show, for the first time, that the ratio of bolometric luminosity to envelope mass of HMSCs (L/M) could not be a reliable evolutionary probe for early massive star formation due to the external heating effects of the HII regions. We show HMSCs associated with HII regions present statistically significant differences from HMSCs far away from HII regions, especially for dust temperature and L/M. More centrally peaked and turbulent properties of HMSCs associated with HII regions may promote the formation of high-mass stars by limiting fragmentation. High-resolution interferometric surveys toward HMSCs are crucial to reveal how HII regions impact the star formation process inside HMSCs.
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122. HR-PYPOPSTAR model
- ID:
- ivo://CDS.VizieR/J/MNRAS/506/4781
- Title:
- HR-PYPOPSTAR model
- Short Name:
- J/MNRAS/506/4781
- Date:
- 06 Dec 2021 20:15:01
- Publisher:
- CDS
- Description:
- We present the HR-PYPOPSTAR model, which provides a complete set (in ages) of high-resolution (HR) spectral energy distributions of Single Stellar Populations. The model uses the most recent high-wavelength-resolution theoretical atmosphere libraries for main-sequence, post-AGB/planetary nebulae and Wolf-Rayet stars. The spectral energy distributions are given for more than a hundred ages ranging from 0.1Myr to 13.8Gyr, at four different values of the metallicity (Z = 0.004, 0.008, 0.019, and 0.05), considering four different IMFs. The wavelength range goes from 91 to 24000{AA} in linear steps {delta}{lambda}=0.1{AA}, giving a theoretical resolving power R_th,5000_~50000 at 5000{AA}. This is the main novelty of these spectra, unique for their age and wavelength ranges. The models include the ionizing stellar populations that are relevant at both young (massive hot stars) and old (planetary nebulae) ages. We have tested the results with some examples of HR spectra recently observed with MEGARA at GTC. We highlight the importance of wavelength resolution in reproducing and interpreting the observational data from the last and forthcoming generations of astronomical instruments operating at 8-10m class telescopes, with higher spectral resolution than their predecessors.
- 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.
- 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.
