- ID:
- ivo://CDS.VizieR/J/AJ/135/726
- Title:
- Spitzer SAGE observations of LMC PNe
- Short Name:
- J/AJ/135/726
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAC and MIPS images and photometry of a sample of previously known planetary nebulae (PNe) from the Surveying the Agents of a Galaxy's Evolution (SAGE) survey of the Large Magellanic Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in the survey field, 185 objects were detected in at least two of the IRAC bands, and 161 detected in the MIPS 24um images. Color-color and color-magnitude diagrams are presented using several combinations of IRAC, MIPS, and Two Micron All Sky Survey magnitudes. The location of an individual PN in the color-color diagrams is seen to depend on the relative contributions of the spectral components which include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared forbidden line emission from the ionized gas, warm dust continuum, and emission directly from the central star. The sample of LMC PNe is compared to a number of Galactic PNe and found not to significantly differ in their position in color-color space. We also explore the potential value of IR PNe luminosity functions (LFs) in the LMC. IRAC LFs appear to follow the same functional form as the well-established [OIII] LFs although there are several PNe with observed IR magnitudes brighter than the cut-offs in these LFs.
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- ID:
- ivo://CDS.VizieR/J/ApJ/845/56
- Title:
- Star clusters automatically detected in the LMC
- Short Name:
- J/ApJ/845/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramirez-Siordia+ (2017, in prep.), estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7deg^2^ we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring ~310Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1Gyr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1446
- Title:
- Star clusters in Magellanic Clouds
- Short Name:
- J/MNRAS/463/1446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have introduced a semi-automated quantitative method to estimate the age and reddening of 1072 star clusters in the Large Magellanic Cloud (LMC) using the Optical Gravitational Lensing Experiment (OGLE) III survey data. This study brings out 308 newly parameterised clusters. In a first of its kind, the LMC clusters are classified into groups based on richness/mass as very poor, poor, moderate and rich clusters, similar to the classification scheme of open clusters in the Galaxy. A major cluster formation episode is found to happen at 125+/-25Myr in the inner LMC. The bar region of the LMC appears prominently in the age range 60-250Myr and is found to have a relatively higher concentration of poor and moderate clusters. The eastern and the western ends of the bar are found to form clusters initially, which later propagates to the central part. We demonstrate that there is a significant difference in the distribution of clusters as a function of mass, using a movie based on the propagation (in space and time) of cluster formation in various groups. The importance of including the low mass clusters in the cluster formation history is demonstrated. The catalog with parameters, classification, and cleaned and isochrone fitted CMDs of 1072 clusters, which are available as online material, can be further used to understand the hierarchical formation of clusters in selected regions of the LMC.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A89
- Title:
- Star clusters in the Magellanic Clouds
- Short Name:
- J/A+A/602/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To produce an homogeneous catalog of astrophysical parameters of 239 resolved star clusters located in the Small and Large Magellanic Clouds, observed in the Washington photometric system. The cluster sample was processed with the recently introduced Automated Stellar Cluster Analysis (ASteCA) package, which ensures both an automatized and a fully reproducible treatment, together with a statistically based analysis of their fundamental parameters and associated uncertainties. The fundamental parameters determined with this tool for each cluster, via a color-magnitude diagram (CMD) analysis, are: metallicity, age, reddening, distance modulus, and total mass. We generated an homogeneous catalog of structural and fundamental parameters for the studied cluster sample, and performed a detailed internal error analysis along with a thorough comparison with values taken from twenty-six published articles. We studied the distribution of cluster fundamental parameters in both Clouds, and obtained their age-metallicity relationships. The ASteCA package can be applied to an unsupervised determination of fundamental cluster parameters; a task of increasing relevance as more data becomes available through upcoming surveys.
- ID:
- ivo://CDS.VizieR/J/ApJS/161/304
- Title:
- Star clusters in the Milky Way and satellites
- Short Name:
- J/ApJS/161/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a database of structural and dynamical properties for 153 spatially resolved star clusters in the Milky Way, the Large and Small Magellanic Clouds, and the Fornax dwarf spheroidal. This database complements and extends others in the literature, such as those of Harris (Cat. <VII/202>) and Mackey & Gilmore (2003MNRAS.338...85M, 2003MNRAS.338..120M, 2003MNRAS.340..175M). Our cluster sample comprises 50 "young massive clusters" in the LMC and SMC, and 103 old globular clusters between the four galaxies. The parameters we list include central and half-light-averaged surface brightnesses and mass densities; core and effective radii; central potentials, concentration parameters, and tidal radii; predicted central velocity dispersions and escape velocities; total luminosities, masses, and binding energies; central phase-space densities; half-mass relaxation times; and "{kappa}-space" parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1531
- Title:
- Star formation history of SMC
- Short Name:
- J/AJ/127/1531
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spatially resolved star formation and chemical enrichment history of the Small Magellanic Cloud (SMC) across the entire central 4{deg}x4.5{deg} area of the main body, based on UBVI photometry from our Magellanic Clouds Photometric Survey.
- ID:
- ivo://CDS.VizieR/J/AJ/103/1205
- Title:
- Stellar Content of LH 9 and 10 in the LMC
- Short Name:
- J/AJ/103/1205
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry and spectroscopy for stars in Lucke-Hodge 9 and 10, two adjacent OB association in the northwest corner of the LMC. Our catalog contains UBV photometry (complete to ~18mag in all three filters) for 795 stars and BV-only photometry (complete to ~19mag in both filters) for an additional 434 stars.
- ID:
- ivo://CDS.VizieR/J/AJ/98/1305
- Title:
- Stellar content of NGC 346
- Short Name:
- J/AJ/98/1305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using CCD UBV photometry and spectroscopy, we have investigated the stellar content of NGC 346, the brightest H II region in the SMC. Spectra of 42 stars confirm that 33 are of O type, of which 11 are of type O6.5 or earlier; this is as many early-type O stars as is known in the rest of the SMC. From the spectroscopy and photometry we are able to construct an H-R diagram which is essentially complete down to ~10M_{sun}_. We find an initial mass-function slope {GAMMA}=-1.9, similar to that found for massive stars near the Sun and in the LMC: the presence of six stars in the mass range 40-85M_{sun}_ suggests that the upper-mass limit of the IMF is also not appreciably lower in the SMC than it is in the Galaxy. Our photometry has identified five probable red supergiants of which one was previously known. These stars, plus two B supergiants, are evolved stars of considerably lower mass (15M_{sun}_) than many of the unevolved cluster members. Most of these lower-mass, evolved stars form a spatially distinct subgroup; we believe that NGC 346 thus provides an example of sequential star formation in the SMC. We also have identified a background field population of 5M_{sun}_ stars. We find that the ionizing flux from the hot stars is consistent with the previously known Half nebular luminosity. Finally, we discuss the enigmatic W-R binary HD 5980, which our point-spread-function fitting has identified as a close visual double.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A103
- Title:
- Stellar models with rotation. 0.8<M<120, Z=0.002
- Short Name:
- J/A+A/558/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the impact of a subsolar metallicity on various properties of non-rotating and rotating stars, such as surface velocities and abundances, lifetimes, evolutionary tracks, and evolutionary scenarios. We provide a grid of single star models covering a mass range of 0.8 to 120M_{sun_} with an initial metallicity Z=0.002 with and without rotation. We discuss the impact of a change in the metallicity by comparing the current tracks with models computed with exactly the same physical ingredients but with a metallicity Z=0.014 (solar). We show that the width of the main-sequence (MS) band in the upper part of the Hertzsprung-Russell diagram (HRD), for luminosity above log(L/L_{sun}_)>5.5, is very sensitive to rotational mixing. Strong mixing significantly reduces the MS width. Here for the first time over the whole mass range, we confirm that surface enrichments are stronger at low metallicity provided that comparisons are made for equivalent initial mass, rotation, and evolutionary stage. We show that the enhancement factor due to a lowering of the metallicity (all other factors kept constant) increases when the initial mass decreases. Present models predict an upper luminosity for the red supergiants (RSG) of log (L/L_{sun}_) around 5.5 at Z=0.002 in agreement with the observed upper limit of RSG in the Small Magellanic Cloud. We show that models using shear diffusion coefficient, which is calibrated to reproduce the surface enrichments observed for MS B-type stars at Z=0.014, can also reproduce the stronger enrichments observed at low metallicity. In the framework of the present models, we discuss the factors governing the timescale of the first crossing of the Hertzsprung gap after the MS phase. We show that any process favouring a deep localisation of the H-burning shell (steep gradient at the border of the H-burning convective core, low CNO content), and/or the low opacity of the H-rich envelope favour a blue position in the HRD for the whole, or at least a significant fraction, of the core He-burning phase.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A104
- Title:
- Stellar parameters of OB stars in SMC wing
- Short Name:
- J/A+A/625/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stars which start their lives with spectral types O and early-B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 massive stars of spectral types O (23 stars) and B (297 stars) in the Wing of the Small Magellanic Cloud (SMC). The spectra, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models, and the stellar parameters were determined. We find that the stellar winds of our sample stars are generally much weaker than theoretically expected. The stellar rotation rates show broad, tentatively bi-modal distribution. The upper Hertzsprung-Russell diagram (HRD) is well populated by the stars of our sample from a specific field in the SMC Wing. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additionally massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggest a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below ~30M_{sun}_ seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with initially more than ~30M_{sun}_ol appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measure the key parameters of stellar feedback and establish the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments the stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of stochastic mode of massive star-formation, where the resulting stellar population is fully capable of producing large scale structures like the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long time scales.
