- ID:
- ivo://CDS.VizieR/J/AJ/142/199
- Title:
- Sizes and luminosities of stellar systems
- Short Name:
- J/AJ/142/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a combined imaging and spectroscopic survey of the nearby central cluster galaxy, M87, to assemble a sample of 34 confirmed UltraCompact Dwarfs (UCDs) with half-light radii of >=10pc measured from Hubble Space Telescope (HST) images. This doubles the existing sample in M87, making it the largest such sample for any galaxy, while extending the detection of UCDs to unprecedentedly low luminosities (MV=-9). With this expanded sample, we find no correlation between size and luminosity, in contrast to previous suggestions, and no general correlation between size and galactocentric distance. We explore the relationships between UCDs, less luminous extended clusters (including faint fuzzies), Globular Clusters (GCs), as well as early-type galaxies and their nuclei, assembling an extensive new catalog of sizes and luminosities for stellar systems. Most of the M87 UCDs follow a tight color-magnitude relation, offset from the metal-poor GCs. This, along with kinematical differences, demonstrates that most UCDs are a distinct population from normal GCs, and not simply a continuation to larger sizes and higher luminosities. The UCD color-magnitude trend couples closely with that for Virgo dwarf elliptical nuclei. We conclude that the M87 UCDs are predominantly stripped nuclei. The brightest and reddest UCDs may be the remnant nuclei of more massive galaxies while a subset of the faintest UCDs may be tidally limited and related to more compact star clusters. In the broader context of galaxy assembly, blue UCDs may trace halo build-up by accretion of low-mass satellites, while red UCDs may be markers of metal-rich bulge formation in larger galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/451/2625
- Title:
- SLUGGS Globular Cluster CaT and [Z/H]
- Short Name:
- J/MNRAS/451/2625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using the DEep Imaging Multi-Object Spectrograph on the Keck, we have been able to measure the metallicities of the stellar and globular cluster components in 12 early-type galaxies out to more than 10Re.
- ID:
- ivo://CDS.VizieR/J/ApJS/101/41
- Title:
- SMC and Bridge extended catalog
- Short Name:
- J/ApJS/101/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A survey of extended objects in the Magellanic System was carried out on the ESO/SERC R and J Sky Survey Atlases. The present work is dedicated to the Small Magellanic Cloud and to the inter-Magellanic Cloud region ("Bridge") totaling 1188 objects, of which 554 are classified as star clusters, 343 are emissionless associations, and 291 are related to emission nebulae. The survey includes cross-identifications among catalogs, and we present 284 new objects. We provide accurate positions, classification, homogeneous sizes, and position angles, as well as information on cluster pairs and hierarchical relation for superimposed objects. Two clumps of extended objects in the Bridge and one at the Small Magellanic Cloud wing tip might be currently forming dwarf spheroidal galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A187
- Title:
- SMC clusters age-dating & classification
- Short Name:
- J/A+A/616/A187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to estimate the age and reddening parameters of already identified star clusters within the Small Magellanic Cloud (SMC) in a consistent way using available photometric data, classify them based on their mass and strength, and study their spatio-temporal distribution. We have used a semi-automated quantitative method, developed in the first paper of this series (Paper I), to estimate the cluster parameters using the V and I band photometric data from the Optical Gravitational Lensing Experiment (OGLE) III survey. We estimated parameters of 179 star clusters (17 are newly parameterised) and classified them into four groups. We present an online catalogue of parameters as well as cleaned and isochrone-fitted colour magnitude diagrams of 179 clusters. We compiled age information of 468 clusters by combining previous studies with our catalogue, to study their spatio-temporal distribution. Most of the clusters located in the southern part of the SMC are in the age range 600Myr-1.25Gyr, whereas, the clusters younger than 100Myr are mostly found in the northern SMC, with the central SMC showing continuous cluster formation. The peak of the cluster age distribution is identified at 130+/-35Myr, very similar to the Large Magellanic Cloud (LMC) in Paper I. We suggest that the burst of cluster formation at 130Myr is due to the most recent LMC-SMC interaction. 90% of the studied sample is found to have mass <1700M_{sun}_, suggesting that the SMC is dominated by low mass clusters. There is tentative evidence for compact clusters in the LMC when compared to those in the Galaxy and the SMC. A progressive shifting of cluster location from the south to north of the SMC is identified in last ~600Myr. The details of spatio-temporal distribution of clusters presented in two videos as part of this study can be used as a tool to constrain details of the recent LMC-SMC interactions.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/67
- Title:
- Smoothed amplitudes from Kepler, K2 and TESS phot.
- Short Name:
- J/ApJ/893/67
- Date:
- 03 Dec 2021 00:35:27
- Publisher:
- CDS
- Description:
- We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10Myr to 4Gyr. We show that a simple light-curve statistic called the "smoothed amplitude" is proportional to stellar age as t^-1/2^, following a Skumanich-like spin-down relation. We marginalize over the unknown stellar inclinations by forward modeling the ensemble of light curves for direct comparison with the Kepler, K2, and TESS photometry. We sample the posterior distributions for spot coverage with approximate Bayesian computation. We find typical spot coverages in the range 1%-10%, which decrease with increasing stellar age. The spot coverage is proportional to t^n^ where n=-0.37+/-0.16, also statistically consistent with a Skumanich-like t^-1/2^ decay of starspot coverage with age. We apply two techniques to estimate the spot coverage of young exoplanet-hosting stars likely to be targeted for transmission spectroscopy with the James Webb Space Telescope, and estimate the bias in exoplanet radius measurements due to varying starspot coverage.
- ID:
- ivo://CDS.VizieR/J/AJ/147/85
- Title:
- Solar neighborhood. XXXIII. 45 M dwarfs
- Short Name:
- J/AJ/147/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present basic observational data and association membership analysis for 45 young and active low-mass stellar systems from the ongoing Research Consortium On Nearby Stars photometry and astrometry program at the Cerro Tololo Inter-American Observatory. Most of these systems have saturated X-ray emission (log(L_X_/L_bol_)>-3.5) based on X-ray fluxes from the ROSAT All-Sky Survey, and many are significantly more luminous than main-sequence stars of comparable color. We present parallaxes and proper motions, Johnson-Kron-Cousins VRI photometry, and multiplicity observations from the CTIOPI program on the CTIO 0.9m telescope. To this we add low-resolution optical spectroscopy and line measurements from the CTIO 1.5m telescope, and interferometric binary measurements from the Hubble Space Telescope Fine Guidance Sensors. We also incorporate data from published sources: JHK_S_ photometry from the Two Micron All Sky Survey point source catalog, X-ray data from the ROSAT All-Sky Survey, and radial velocities from literature sources. Within the sample of 45 systems, we identify 21 candidate low-mass pre-main-sequence members of nearby associations, including members of {beta} Pictoris, TW Hydrae, Argus, AB Doradus, two ambiguous {approx}30Myr old systems, and one object that may be a member of the Ursa Major moving group. Of the 21 candidate young systems, 14 are newly identified as a result of this work, and six of those are within 25pc of the Sun.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A172
- Title:
- Solar neighbourhood young stars 3D mapping
- Short Name:
- J/A+A/620/A172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the three dimensional arrangement of young stars in the solar neighbourhood using the second release of the Gaia mission (Gaia DR2) and we provide a new, original view of the spatial configuration of the star forming regions within 500pc from the Sun. By smoothing the star distribution through a gaussian filter, we construct three dimensional density maps for early-type stars (upper-main sequence, UMS) and pre-main sequence (PMS) sources. The PMS and the UMS samples are selected through a combination of photometric and astrometric criteria. A side product of the analysis is a three dimensional, G-band extinction map, which we use to correct our colour-magnitude diagram for extinction and reddening. Both density maps show three prominent structures, Scorpius-Centaurus, Orion, and Vela. The PMS map shows a plethora of lower mass star forming regions, such as Taurus, Perseus, Cepheus, Cassiopeia and Lacerta, which are less visible in the UMS map, due to the lack of large numbers of bright, early-type stars. We report the finding of a candidate new open cluster towards l, b ~218.5{deg}, -2{deg}, which could be related to the Orion star forming complex. We estimate ages for the PMS sample and we study the distribution of PMS stars as a function of their age. We find that younger stars cluster in dense, compact clumps, and are surrounded by older sources, whose distribution is instead more diffuse. The youngest groups that we find are mainly located in Scorpius-Centaurus, Orion, Vela and Taurus. Cepheus, Cassiopeia, and Lacerta are instead more evolved and less numerous. Finally, we find that the three dimensional density maps show no evidence for the existence of the ring-like structure which is usually referred to as the Gould Belt.
- ID:
- ivo://CDS.VizieR/J/ApJ/785/159
- Title:
- SONYC census of substellar objects in Lupus 3
- Short Name:
- J/ApJ/785/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- SONYC -Substellar Objects in Nearby Young Clusters- is a survey program to investigate the frequency and properties of substellar objects in nearby star-forming regions. We present a new imaging and spectroscopic survey conducted in the young (~1 Myr), nearby (~200 pc) star-forming region Lupus 3. Deep optical and near-infrared images were obtained with MOSAIC-II and NEWFIRM at the CTIO 4 m telescope, covering ~1.4 deg^2^ on the sky. The i-band completeness limit of 20.3 mag is equivalent to 0.009-0.02 M_{sun}_, for A_V_<=5. Photometry and 11-12 yr baseline proper motions were used to select candidate low-mass members of Lupus 3. We performed a spectroscopic follow-up of 123 candidates, using VIMOS at the Very Large Telescope, and we identify 7 probable members, among which 4 have spectral type later than M6.0 and T_eff_<=3000 K, i.e., are probably substellar in nature. Two of the new probable members of Lupus 3 appear underluminous for their spectral class and exhibit emission line spectrum with strong H_{alpha}_ or forbidden lines associated with active accretion. We derive a relation between the spectral type and effective temperature: T_eff_=(4120+/-175)-(172+/-26)xSpT, where SpT refers to the M spectral subtype between 1 and 9. Combining our results with the previous works on Lupus 3, we show that the spectral type distribution is consistent with that in other star-forming regions, as well as the derived star-to-brown dwarf ratio of 2.0-3.3. We compile a census of all spectroscopically confirmed low-mass members with spectral type M0 or later.
- ID:
- ivo://CDS.VizieR/J/ApJ/785/47
- Title:
- Sources around target stars in Upper Scorpius
- Short Name:
- J/ApJ/785/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multiplicity survey of 91 stars spanning masses of ~0.2-10 M_{sun}_ in the Upper Scorpius star-forming region, based on adaptive optics imaging with the Gemini North telescope. Our observations identified 29 binaries, 5 triples, and no higher order multiples. The corresponding raw multiplicity frequency is 0.37+/-0.05. In the regime where our observations are complete - companion separations of 0.1''-5'' (~15-800 AU) with magnitude limits ranging from K <9.3 at 0.1'' to K<15.8 at 5'' - the multiplicity frequency is 0.27_0.04_^+0.05^. For similar separations, the multiplicity frequency in Upper Scorpius is comparable to that in other dispersed star-forming regions, but is a factor of two to three higher than in denser star-forming regions or in the field. Our sample displays a constant multiplicity frequency as a function of stellar mass. Among our sample of binaries, we find that both wider (>100 AU) and higher-mass systems tend to have companions with lower companion-to-primary mass ratios. Three of the companions identified in our survey are unambiguously substellar and have estimated masses below 0.04 M_{sun}_ (two of them are new discoveries from this survey - 1RXS J160929.1-210524b and HIP 78530B - although we have reported them separately in earlier papers). These three companions have projected orbital separations of 300-900 AU. Based on a statistical analysis factoring in sensitivity limits, we calculate an occurrence rate of 5-40 M_Jup_ companions of ~4.0% for orbital separations of 250-1000 AU, compared to <1.8% at smaller separations, suggesting that such companions are more frequent on wider orbits.
- ID:
- ivo://CDS.VizieR/J/ApJ/713/871
- Title:
- Sources in star-forming region Cyg-OB2 from X-ray
- Short Name:
- J/ApJ/713/871
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cygnus OB2 is the nearest example of a massive star-forming region (SFR), containing over 50 O-type stars and hundreds of B-type stars. We have analyzed the properties of young stars in two fields in Cyg OB2 using the recently published deep catalog of Chandra X-ray point sources with complementary optical and near-IR photometry. Our sample is complete to ~1M_{sun}_ (excluding A- and B-type stars that do not emit X-rays), making this the deepest study of the stellar properties and star formation history in Cyg OB2 to date. Combining our stellar mass function (MF) and an estimate of the radial density profile of the association suggests a total mass of Cyg OB2 of ~3x10^4^M_{sun}_, similar to that of many of our Galaxy's most massive SFRs.
