- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A26
- Title:
- Cosmography of OB stars in the solar neighbourhood
- Short Name:
- J/A+A/584/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a 3D map of the spatial density of OB stars within 500pc from the Sun using the Hipparcos catalogue and find three large-scale stream-like structures that allow a new view on the solar neighbourhood. The spatial coherence of these blue streams and the monotonic age sequence over hundreds of parsecs suggest that they are made of young stars, similar to the young streams that are conspicuous in nearby spiral galaxies. The three streams are 1) the Scorpius to Canis Majoris stream, covering 350pc and 65Myr of star formation history; 2) the Vela stream, encompassing at least 150pc and 25Myr of star formation history; and 3) the Orion stream, including not only the well-known Orion OB1abcd associations, but also a large previously unreported foreground stellar group lying only 200pc from the Sun. The map also reveals a remarkable and previously unknown nearby OB association, between the Orion stream and the Taurus molecular clouds, which might be responsible for the observed structure and star formation activity in this cloud complex. This new association also appears to be the birthplace of Betelgeuse, as indicated by the proximity and velocity of the red giant. If this is confirmed, it would solve the long-standing puzzle of the origin of Betelgeuse. The well-known nearby star-forming low-mass clouds, including the nearby T and R associations Lupus, Cha, Oph, CrA, Taurus, Vela R1, and various low-mass cometary clouds in Vela and Orion, appear in this new view of the local neighbourhood to be secondary star formation episodes that most likely were triggered by the feedback from the massive stars in the streams. We also recover well-known star clusters of various ages that are currently cruising through the solar neighbourhood. Finally, we find no evidence of an elliptical structure such as the Gould belt, a structure we suggest is a 2D projection effect, and not a physical ring.
- ID:
- ivo://CDS.VizieR/J/A+A/501/585
- Title:
- CT1 photometry in five LMC star clusters
- Short Name:
- J/A+A/501/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Aims: We present CCD photometry in the Washington system C and T1 passbands down to T1~22.5 in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Methods: Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of the field star contamination and derive cluster colour-magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (T1, C-T_1_) CMDs, the {delta}(T1) index and the Standard Giant Branch procedure, we derive metallicities and ages for the five clusters. We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. Results: With the exception of NGC 1697 (age=0.7Gyr, [Fe/H]=0.0dex), the remaining four clusters are of intermediate-age (from 2.2 to 3.0Gyr) and relatively metal-poor ([Fe/H]=0.7dex). The cluster and field age-metallicty realtions show evidence for a metallicity offset but do overlap, particularly on the upper envelope side of the cluster age-metallicity relation. Conclusions: We confirm previous results that clusters younger than ~1Gyr were formed during an outside-in process; this occurred after a bust of cluster formation that took place mainly in the outer disk and peaked at ~2Gyr ago.
- ID:
- ivo://CDS.VizieR/J/PASP/123/519
- Title:
- C,T1 photometry of 6 LMC clusters
- Short Name:
- J/PASP/123/519
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of an ongoing project to investigate the cluster formation and chemical evolution history in the Large Magellanic Cloud (LMC), we have used the CTIO 0.9m telescope to obtain CCD imaging in the Washington system of NGC 2161, SL 874, and KMHK 1719 - three unstudied star clusters located in the outer region of the LMC. We measured T1 magnitudes and C-T1 colors for a total of 9611 stars distributed throughout cluster areas of 13.6x13.6arcmin^2^. Cluster radii were estimated from star counts distributed throughout the entire observed fields. Careful attention was paid to setting apart the cluster and field star distributions so that statistically cleaned color-magnitude diagrams (CMDs) were obtained. Based on the best fits of isochrones computed by the Padova group to the (T1, C-T1) CMDs, the {delta}T1 index, and the standard giant branch procedure, ages and metallicities were derived for the three clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/1215
- Title:
- CT1 photometry of 10 SMC clusters
- Short Name:
- J/MNRAS/358/1215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Colour-magnitude diagrams (CMDs) are presented for the first time for 10 star clusters projected on to the Small Magellanic Cloud (SMC). The photometry was carried out in the Washington system C and T1 filters allowing the determination of ages by means of the magnitude difference between the red giant clump and the main-sequence turnoff (MSTO), and metallicities from the red giant branch (RGB) locus.
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/429
- Title:
- CT1 photometry of 7 young SMC star clusters
- Short Name:
- J/MNRAS/389/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Washington system C and T1 passbands down to T1~22 in the fields of L35, L45, L49, L50, L62, L63 and L85, seven poorly studied star clusters in the inner region of the Small Magellanic Cloud (SMC). We measured T1 magnitudes and C-T1 colours for a total of 114826 stars distributed throughout cluster areas of 13.7x13.7arcmin^2^ each. Cluster radii were estimated from star counts distributed throughout the entire observed fields.
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/1559
- Title:
- CT1T2 photometry in 14 SMC star clusters
- Short Name:
- J/MNRAS/417/1559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD photometry in the Washington system C, T1 and T2 passbands down to T1~23 in the fields of L3, L28, HW 66, L100, HW 79, IC 1708, L106, L108, L109, NGC 643, L112, HW 84, HW 85 and HW 86, 14 Small Magellanic Cloud (SMC) clusters, most of them poorly studied objects. We measured T1 magnitudes and C-T1 and T1-T2 colours for a total of 213 516 stars spread throughout cluster areas of 14.7x14.7arcmin^2^ each. We carried out an in-depth analysis of the field star contamination of the colour-magnitude diagrams (CMDs) and statistically cleaned the cluster CMDs.
