- ID:
- ivo://CDS.VizieR/J/A+A/499/175
- Title:
- ^12^CO(2-1) map of NGC 2264-C
- Short Name:
- J/A+A/499/175
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role played by protostellar feedback in clustered star formation is still a matter of debate. In particular, protostellar outflows have been proposed as a source of turbulence in cluster-forming clumps, which may provide support against global collapse for several free-fall times. Here, we seek to test the above hypothesis in the case of the well-documented NGC 2264-C protocluster, by quantifying the amount of turbulence and support injected in the surrounding medium by protostellar outflows. Using the HERA heterodyne array on the IRAM 30m telescope, we carried out an extensive mapping of NGC 2264-C in the three molecular line transitions ^12^CO(2-1), ^13^CO(2-1), and C^18^O(2-1). We found widespread high-velocity 12 CO emission, testifying to the presence of eleven outflow lobes, closely linked to the compact millimeter continuum sources previously detected in the protocluster. We carried out a detailed analysis of the dynamical parameters of these outflows, including a quantitative evaluation of the overall momentum flux injected in the cluster-forming clump. These dynamical parameters were compared to the gravitational and turbulent properties of the clump. We show that the population of protostellar outflows identified in NGC 2264-C is likely to contribute a significant fraction of the observed turbulence but cannot efficiently support the protocluster against global collapse. Gravity appears to largely dominate the dynamics of the NGC 2264-C clump at the present time ; however it is possible that an increase in the star formation rate during the later evolution of the protocluster will trigger enough outflows to finally halt the contraction of the cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/136/2483
- Title:
- Comoving group associated with HD 141569
- Short Name:
- J/AJ/136/2483
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for a young stellar moving group associated with the star HD 141569 - a nearby, isolated Herbig AeBe primary member of a 5+/-3Myr-old triple star system on the outskirts of the Sco-Cen complex. Our spectroscopic survey identified a population of 21 Li-rich, >~30Myr-old stars within 30{deg} of HD 141569 which possess similar proper motions with the star. The spatial distribution of these Li-rich stars, however, is not suggestive of a moving group associated with the HD 141569 triplet, but rather this sample appears cospatial with Upper Scorpius (US) and Upper Centaurus Lupus (UCL). We apply a modified moving cluster parallax method to compare the kinematics of these youthful stars with those of the US and UCL. Eight new potential members of US and five new potential members of UCL are identified. A substantial moving group with an identifiable nucleus within 15{deg} (~30pc) of HD 141569 is not found in this sample. Evidently, the HD 141569 system formed ~5Myr ago in relative isolation, tens of parsecs away from the recent sites of star formation in the Ophiucus-Scorpius-Centaurus region.
- ID:
- ivo://CDS.VizieR/J/AJ/153/257
- Title:
- Comoving stars in Gaia DR1
- Short Name:
- J/AJ/153/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The primary sample of the Gaia Data Release 1 is the Tycho-Gaia Astrometric Solution (TGAS): {simeq}2 million Tycho-2 sources with improved parallaxes and proper motions relative to the initial catalog. This increased astrometric precision presents an opportunity to find new binary stars and moving groups. We search for high-confidence comoving pairs of stars in TGAS by identifying pairs of stars consistent with having the same 3D velocity using a marginalized likelihood ratio test to discriminate candidate comoving pairs from the field population. Although we perform some visualizations using (bias-corrected) inverse parallax as a point estimate of distance, the likelihood ratio is computed with a probabilistic model that includes the covariances of parallax and proper motions and marginalizes the (unknown) true distances and 3D velocities of the stars. We find 13085 comoving star pairs among 10606 unique stars with separations as large as 10pc (our search limit). Some of these pairs form larger groups through mutual comoving neighbors: many of these pair networks correspond to known open clusters and OB associations, but we also report the discovery of several new comoving groups. Most surprisingly, we find a large number of very wide (>1pc) separation comoving star pairs, the number of which increases with increasing separation and cannot be explained purely by false-positive contamination. Our key result is a catalog of high-confidence comoving pairs of stars in TGAS. We discuss the utility of this catalog for making dynamical inferences about the Galaxy, testing stellar atmosphere models, and validating chemical abundance measurements.
- ID:
- ivo://CDS.VizieR/J/MNRAS/405/1293
- Title:
- Compact star clusters in M81
- Short Name:
- J/MNRAS/405/1293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the population of compact star clusters (CSCs) in M81, using the Hubble Space Telescope/Advanced Camera for Surveys (ACS) images in the filters F435W, F606W and F814W covering, for the first time, the entire optical extent of the galaxy. Our sample contains 435 clusters of full width at half-maximum less than 10 ACS pixels (9pc). The sample shows the presence of two cluster populations, a blue group of 263 objects brighter than B=22mag, and a red group of 172 objects, brighter than B=24mag. On the basis of analysis of colour-magnitude diagrams and making use of simple stellar population models,
- ID:
- ivo://CDS.VizieR/J/MNRAS/382/1342
- Title:
- Compact stellar systems around NGC 1399
- Short Name:
- J/MNRAS/382/1342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained spectroscopic redshifts of colour-selected point sources in four wide area VLT-FLAMES (Very Large Telescope-Fibre Large Array Multi Element Spectrograph) fields around the Fornax cluster giant elliptical galaxy NGC 1399, identifying as cluster members 27 previously unknown faint (-10.5<M_g'_<-8.8) compact stellar systems (CSS), and improving redshift accuracy for 23 previously catalogued CSS.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A46
- Title:
- Compiled photometry for Cham I and II members
- Short Name:
- J/A+A/551/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a proper motion study aiming at providing further evidence on the origin of the proposed stellar members of the Chamaeleon I and II clouds and to identify interlopers from the foreground young clusters {epsilon} Cha and {eta} Cha. We compiled lists of spectroscopically confirmed members of the four associations, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-matched these lists with the UCAC3 (Cat. I/315) catalogue to get proper motions for the objects. In the vector point diagram, we identified the different moving groups, and used this information to study the membership of proposed candidate members of the associations from the literature. For those objects with available radial velocities, we computed their Galactic space velocities. We compiled photometry from public data archives and from the literature for the Cha I and II objects. We looked for correlations between the properties of the objects and their proper motions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/1059
- Title:
- Complete sample of Galactic clump properties
- Short Name:
- J/MNRAS/473/1059
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) is an unbiased 870um submillimetre survey of the inner Galactic plane (|l|<60{deg} with |b|<1.5{deg}). It is the largest and most sensitive ground-based submillimetre wavelength Galactic survey to date and has provided a large and systematic inventory of all massive, dense clumps in the Galaxy (>=1000M_{sun}_ at a heliocentric distance of 20kpc) and includes representative samples of all of the earliest embedded stages of high-mass star formation. Here, we present the first detailed census of the properties (velocities, distances, luminosities and masses) and spatial distribution of a complete sample of ~8000 dense clumps located in the Galactic disc (5{deg}<|l|<60{deg}). We derive highly reliable velocities and distances to ~97 per cent of the sample and use mid- and far-infrared survey data to develop an evolutionary classification scheme that we apply to the whole sample. Comparing the evolutionary subsamples reveals trends for increasing dust temperatures, luminosities and linewidths as a function of evolution indicating that the feedback from the embedded protoclusters is having a significant impact on the structure and dynamics of their natal clumps. We find that the vast majority of the detected clumps are capable of forming a massive star and 88 per cent are already associated with star formation at some level. We find the clump mass to be independent of evolution suggesting that the clumps form with the majority of their mass in situ. We estimate the statistical lifetime of the quiescent stage to be ~5x10^4^yr for clump masses >1000M_{sun}_ decreasing to ~1x10^4^yr for clump masses >10000M_{sun}_. We find a strong correlation between the fraction of clumps associated with massive stars and peak column density. The fraction is initially small at low column densities, but reaching 100 per cent for column densities above 10^23^cm^x2^; there are no clumps with column densities above this value that are not already associated with massive star formation. All of the evidence is consistent with a dynamic view of star formation wherein the clumps form rapidly and are initially very unstable so that star formation quickly ensues.
- ID:
- ivo://CDS.VizieR/J/AJ/158/187
- Title:
- Confirmed members of nearby young moving groups
- Short Name:
- J/AJ/158/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first statistical analysis of exoplanet direct imaging surveys combining adaptive optics (AO) imaging at small separations with deep seeing-limited observations at large separations allowing us to study the entire orbital separation domain from 5 to 5000 au simultaneously. Our sample of 344 stars includes only confirmed members of nearby young associations and is based on all AO direct-imaging detection limits readily available online, with addition of our own previous seeing-limited surveys. Assuming that the companion distribution in mass and a semimajor axis follows a power-law distribution and adding a dependence on the mass of the host star, such as d^2^{prop.to}fM^{alpha}^a^{beta}^(M_*_/M_{sun}_)^{gamma}^dMda, we constrain the parameters to obtain {alpha}=-0.18_-0.65_^+0.77^, {beta}=-1.43_-0.24_^+0.23^, and {gamma}=0.62_-0.50_^+0.56^ at a 68% confidence level, and we obtain f=0.11_-0.05_^+0.11^ for the overall planet occurrence rate for companions with masses between 1 and 20 M_Jup_ in the range of 5-5000 au. Thus, we find that occurrence of companions is negatively correlated with a semimajor axis and companion mass (marginally) but is positively correlated with the stellar host mass. Our inferred mass distribution is in good agreement with other distributions found previously from direct imaging surveys for planets and brown dwarfs, but is shallower as a function of mass than the distributions inferred by radial velocity surveys of gas giants in the 1-3 au range. This may suggest that planets at these wide and very wide separations represent the low-mass tail of the brown dwarfs and stellar companion distribution rather than an extension of the distribution of the inner planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/37
- Title:
- CO observations in giant molecular clouds of M33
- Short Name:
- J/ApJ/761/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a giant molecular cloud (GMC) catalog of M33 (NGC598), containing 71 GMCs in total, based on wide-field and high-sensitivity CO(J=3-2) observations with a spatial resolution of 100pc using the ASTE 10m telescope. Employing archival optical data, we identify 75 young stellar groups (YSGs) from the excess of the surface stellar density, and estimate their ages by comparing with stellar evolution models. A spatial comparison among the GMCs, YSGs, and H II regions enable us to classify GMCs into four categories: Type A, showing no sign of massive star formation (SF); Type B, being associated only with H II regions; Type C, with both H II regions and <10Myr old YSGs; and Type D, with both H II regions and 10-30Myr YSGs. Out of 65 GMCs (discarding those at the edges of the observed fields), 1 (1%), 13 (20%), 29 (45%), and 22 (34%) are Types A, B, C, and D, respectively. We interpret these categories as stages in a GMC evolutionary sequence. Assuming that the timescale for each evolutionary stage is proportional to the number of GMCs, the lifetime of a GMC with a mass >10^5^M_{sun}_ is estimated to be 20-40Myr. In addition, we find that the dense gas fraction as traced by the CO(J=3-2)/CO(J=1-0) ratio is enhanced around SF regions. This confirms a scenario where dense gas is preferentially formed around previously generated stars, and will be the fuel for the next stellar generation. In this way, massive SF gradually propagates in a GMC until gas is exhausted.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A84
- Title:
- Coronae of nearby star clusters
- Short Name:
- J/A+A/645/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a novel view on the morphology and dynamical state of ten prominent, nearby (<=500pc), and young (~30-300Myr) open star clusters with Gaia DR2: Per, Blanco 1, IC 2602, IC 2391, Messier 39, NGC 2451A, NGC 2516, NGC 2547, Platais 9, and the Pleiades. We introduce a pioneering member-identification method that is informed by cluster bulk velocities and deconvolves the spatial distribution with a mixture of Gaussians. Our approach enables inferring the true spatial distribution of the clusters by effectively filtering field star contaminants while at the same time mitigating the effect of positional errors along the line of sight. This first application of the method reveals vast stellar coronae that extend for >~100pc and surround the cluster cores, which are comparatively tiny and compact. The coronae and cores form intertwined, coeval, and comoving extended cluster populations, each encompassing tens of thousands of cubic parsec and stretching across tens of degrees on the sky. Our analysis shows that the coronae are gravitationally unbound but largely comprise the bulk of the stellar mass of the populations. Most systems are in a highly dynamic state, showing evidence of expansion and sometimes simultaneous contraction along different spatial axes. The velocity field of the extended populations for the cluster cores appears asymmetric but is aligned along a spatial axis unique to each cluster. The overall spatial distribution and the kinematic signature of the populations are largely consistent with the differential rotation pattern of the Milky Way. This finding underlines the important role of global Galactic dynamics in the fate of stellar systems. Our results highlight the complexity of the Milky Way's open cluster population and call for a new perspective on the characterization and dynamical state of open clusters.
