- ID:
- ivo://CDS.VizieR/J/A+A/590/A13
- Title:
- New candidate members in young associations
- Short Name:
- J/A+A/590/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young associations offer us one of the best opportunities to study the properties of young stellar and sub-stellar objects and directly image planets thanks to their proximity (<200pc) and age (5-150Myr). However, many previous works have been limited to identifying the brighter, more active members (1Msun) due to photometric survey sensitivities limiting the detections of lower-mass objects. We search the field of view of 542 previously identified members of the young associations to identify wide / extremely wide (1000-100,000au in physical separation) companions. Methods. We have combined 2MASS near-infrared photometry (J, H, K) with proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literature and conducted our own high-resolution spectroscopic observations for a sub-sample of candidate members. This complementary information allowed us to assess the efficiency of our method. We identified 84 targets (45:0.2-1.3M_{sun}_, 17:0.08-0.2M_{sun}_, 22:<0.08M_{sun}_) in our analysis, 10 of which have been identified from spectroscopic analysis in previous young association works. For 33 of these 84 we were able to further assess their membership using a variety of properties (X-ray emission, UV excess, H{alpha}, lithium and KI equivalent widths, radial velocities, and CaH indices). We derive a success rate of 76-88% for this technique based on the consistency of these properties. Once confirmed, the targets identified in this work would significantly improve our knowledge of the lower-mass end of the young associations. Additionally, these targets would make an ideal new sample for the identification and study of planets around nearby young stars. Given the predicted sub-stellar mass of the majority of these new candidate members and their proximity, high-contrast imaging techniques would facilitate the search for new low-mass planets.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/1545
- Title:
- New compact star cluster candidates in GP
- Short Name:
- J/MNRAS/469/1545
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sample of known star clusters, the fundamental building blocks of galaxies, in the Milky Way is still extremely incomplete for objects beyond a distance of 1-2kpc. Many of the more distant and young clusters are compact and hidden behind large amounts of extinction. We thus utilized the deep high-resolution near-infrared surveys UGPS and VVV to uncover so far unknown compact clusters and to analyse their properties. Images of all objects in the area covered by these two surveys, which are listed as galaxy in SIMBAD, have been inspected and 125 so far unknown stellar clusters and candidate clusters have been identified. Based on the frequent associations with star formation indicators (nebulosities, IRAS sources, HII regions, masers) we find that the typical cluster in our sample is young, at distances between 1-10 kpc and has a typical apparent radius of 25-arcsec. We suggest more systematic searches, e.g. at all positions of 2MASS extended sources to increase the completeness of the known cluster sample beyond distances of 2kpc.
- ID:
- ivo://CDS.VizieR/J/other/NewA/34.84
- Title:
- New Galactic embedded cluster candidates
- Short Name:
- J/other/NewA/34.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out a search for new infrared star clusters, stellar groups and candidates using WISE images, which are very sensitive to dust emission nebulae. We report the discovery of 437 embedded clusters and stellar groups that show a variety of structures, both in the stellar and nebular components. Pairs or small groupings of clusters are observed, suggesting multiple generations at the early formation stages. The resulting catalogue provides Galactic and equatorial coordinates, together with angular sizes for all objects. The nature of a representative test sub-sample of 14 clusters is investigated in detail by means of 2MASS photometry. The colour magnitude diagrams and radial density distributions characterise them as stellar clusters. The 437 new objects were found in the ranges 145{deg}<.l<=290{deg} and -25{deg}<=b<=20{deg}, and they appear to be a major object source for future studies of star cluster formation and their early evolution. WISE is a powerful tool to further probe for very young clusters throughout the disk.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/3126
- Title:
- New Galactic star clusters and candidates
- Short Name:
- J/MNRAS/455/3126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of 652 star clusters, stellar groups and candidates in the Milky Way with Wide-field Infrared Survey Explorer (WISE). Most of the objects are projected close to Galactic plane and are embedded clusters. The present sample complements a similar study (Paper I, Bica et al., 2015, Cat. J/other/NewA/34.84) which provided 437 star clusters and alike. We find evidence that star formation processes span a wide range of sizes, from populous dense clusters to small compact embedded ones, sparse stellar groups or in relative isolation. The present list indicates multiple stellar generations during the embedded phase, with giant molecular clouds collapsing into several clumps composing an embedded cluster aggregate. We investigate the field star decontaminated colour-magnitude diagrams and radial density profiles of nine cluster candidates in the list, and derive their parameters, confirming them as embedded clusters.
- ID:
- ivo://CDS.VizieR/J/PAZh/21/13
- Title:
- New list of OB associations
- Short Name:
- J/PAZh/21/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new partition into associations of OB stars within 3kpc of the Sun is derived using Battinelli's modification of the cluster analysis method. We have found 58 associations, of which only 10% may be considered as a random clusters of field stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/32
- Title:
- Newly identified star clusters in Gaia DR2
- Short Name:
- J/ApJS/245/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Star cluster Hunting Pipeline (SHiP) that can identify star clusters in Gaia second data release (DR2) data and establish a star cluster catalog for the Galactic disk. A friend-of-friend-based cluster finder method is used to identify star clusters using five-dimensional stellar parameters, l,b,{omega},{mu}_{alpha}_cos{delta}, and {mu}_{delta}_. Our new catalog contains 2443 star cluster candidates identified from disk stars located within |b|=25{deg} and with G<18mag. An automatic isochrone fitting scheme is applied to all cluster candidates. With a combination of parameters obtained from isochrone fitting, we classify cluster candidates into three classes (Class 1, 2, and 3). Class 1 clusters are the most probable star cluster candidates with the most stringent criteria. Most of these clusters are nearby (within 4kpc). Our catalog is crossmatched with three Galactic star cluster catalogs, Kharchenko+ (2013, J/A+A/558/A53), Cantat-Gaudin+ (2018, J/A+A/618/A93 and 2019, J/A+A/624/A126), and Bica+ (2019, J/AJ/157/12). The proper motion and parallax of matched star clusters are in good agreement with these earlier catalogs. We discover 76 new star cluster candidates that are not listed in these three catalogs. The majority of these are clusters older than log(age/yr)=8.0 and are located in the inner disk with |b|<5{deg}. The recent discovery of new star clusters suggests that current Galactic star cluster catalogs are still incomplete. Among the Class 1 cluster candidates, we find 56 candidates for star cluster groups.
- ID:
- ivo://CDS.VizieR/J/PASP/125/636
- Title:
- Newly identified star clusters in M 31
- Short Name:
- J/PASP/125/636
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the HST archives, we have searched portions of the southern half and northwest quarter of the Andromeda Galaxy (M 31, NGC 224) for previously unrecognized star clusters. The result is a table of the characteristics of 71 newly identified star clusters. Most are moderately faint, low-mass clusters. Absolute magnitudes range from M(V)=-6.3 to -2.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/839
- Title:
- Newly identified star clusters in M33. II.
- Short Name:
- J/ApJ/699/839
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present integrated photometry and color-magnitude diagrams (CMDs) for 161 star clusters in M33, of which 115 were previously uncataloged, using the Advanced Camera For Surveys Wide Field Channel onboard the Hubble Space Telescope. The integrated V-band magnitudes of these clusters range from M_V_~-9 to as faint as M_V_~-4, extending the depth of the existing M33 cluster catalogs by ~1mag. Comparisons of theoretical isochrones to the CMDs using the Padova models yield ages for 148 of these star clusters. The ages range from log(t)~7.0 to log(t)~9.0. Our CMDs are not sensitive to clusters older than ~1Gyr. We find that the variation of the clusters' integrated colors and absolute magnitudes with age is consistent with the predictions of simple stellar population models. These same models suggest that the masses of the clusters in our sample range from 5x10^3^ to 5x10^4^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A50
- Title:
- New massive members of Cygnus OB2
- Short Name:
- J/A+A/612/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cygnus complex is one of the most powerful star forming regions at a close distance from the Sun (~1.4kpc). Its richest OB association Cygnus OB2 is known to harbor many tens of O-type stars and hundreds of B-type stars, providing a large homogeneous population of OB stars that can be analyzed. Many studies of its massive population have been developed in the last decades, although the total number of OB stars is still incomplete. Our aim is to increase the sample of O and B members of Cygnus OB2 and its surroundings by spectroscopically classifying 61 candidates as possible OB-type members of Cygnus OB2, using new intermediate resolution spectroscopy. We have obtained intermediate resolution (R~5000) spectra for all of the OB-type candidates between 2013 and 2017. We thus performed a spectral classification of the sample using HeI-II and metal lines rates, as well as the Marxist Ghost Buster (MGB) software for O-type stars and the IACOB standards catalog for B-type stars. From the whole sample of 61 candidates, we have classified 42 stars as new massive OB-type stars, earlier than B3, in Cygnus OB2 and surroundings, including 11 O-type stars. The other candidates are discarded as they display later spectral types inconsistent with membership in the association. We have also obtained visual extinctions for all the new confirmed massive OB members, placing them in a Hertzsprung-Russell Diagram using calibrations for Teff and luminosity. Finally, we have studied the age and extinction distribution of our sample within the region. We have obtained new blue intermediate-resolution spectra suitable for spectral classification of 61 OB candidates in Cygnus OB2 and surroundings. The confirmation of 42 new OB massive stars (earlier than B3) in the region allows us to increase the young massive population known in the field. We have also confirmed the correlation between age and Galactic longitude previously found in the region. We conclude that many O and early B stars at B>16mag are still undiscovered in Cygnus.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A51
- Title:
- New M31 star cluster candidates
- Short Name:
- J/A+A/658/A51
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Identification of new star cluster candidates in M 31 is fundamental for the study of the M 31 stellar cluster system. The machine-learning method convolutional neural network (CNN) is an efficient algorithm for searching for new M 31 star cluster candidates from tens of millions of images from wide-field photometric surveys. We search for new M 31 cluster candidates from the high-quality g- and i-band images of 21 245 632 sources obtained from the Pan-Andromeda Archaeological Survey (PAndAS) through a CNN. We collected confirmed M 31 clusters and noncluster objects from the literature as our training sample. Accurate double-channel CNNs were constructed and trained using the training samples. We applied the CNN classification models to the PAndAS g- and i-band images of over 21 million sources to search new M 31 cluster candidates. The CNN predictions were finally checked by five experienced human inspectors to obtain high-confidence M 31 star cluster candidates. After the inspection, we identified a catalogue of 117 new M 31 cluster candidates. Most of the new candidates are young clusters that are located in the M 31 disk. Their morphology, colours, and magnitudes are similar to those of the confirmed young disk clusters. We also identified eight globular cluster candidates that are located in the M 31 halo and exhibit features similar to those of confirmed halo globular clusters. The projected distances to the M 31 centre for three of them are larger than 100kpc.
