Denilso da Silva Camargo

Probing FSR star cluster candidates in bulge/disc directions with 2MASS colour–magnitude diagrams

We analyse 20 star cluster candidates projected mostly in the bulge direction (|� | < 60 ◦ ). The sample contains all candidates in that sector classified by Froebrich, Scholz & Raftery with quality flags denoting high probability of being star clusters. Bulge contamination in the colour‐magnitude diagrams (CMDs) is in general important, while at lower Galactic latitudes disc stars contribute as well. Properties of the candidates are investigated with Two Micron All Sky Survey (2MASS) CMDs and stellar radial density profiles (RDPs) built with field star decontaminated photometry. To uncover the nature of the structures we decontaminate the CMDs from field stars using tools that we previously developed to deal with objects in dense fields. We confirm in all cases excesses in the RDPs with respect to the background level, as expected from the method the candidates were originally selected. CMDs and RDPs taken together revealed six open clusters, five uncertain cases that require deeper observations, while nine objects are possibly field density fluctuations.

Towards a census of the Galactic anticentre star clusters: colour–magnitude diagram and structural analyses of a sample of 50 objects

Aims. In this work we investigate the nature of 50 overdensities from the catalogue of Froebrich, Scholz, and Raftery (FSR) projected towards the Galactic anticentre, in the sector 160 ◦ ≤ � ≤ 200 ◦ . The sample contains candidates with |b |≤ 20 ◦ classified by FSR as probable open cluster (OC) and labelled with quality flags 2 and 3. Our main purpose is to determine the nature of these OC candidates and the fraction of these objects that are unknown OCs, as well as to derive astrophysical parameters (age, reddening, distance, core and cluster radii) for the clusters and to investigate the relationship among parameters. Methods. The analysis is based on 2MASS J ,( J − H), and (J − Ks) colour‐magnitude diagrams (CMDs), and stellar radial density profiles (RDPs) built with decontamination tools. The tools are a field star decontamination algorithm, used to uncover the cluster’s intrinsic CMD morphology, and colour‐magnitude filters to isolate stars with a high probability of being cluster members. Results. Out of the 50 objects, 16 (32%) are star clusters. We show that 9 (18%) overdensities are new OCs (FSR 735, FSR 807, FSR 812, FSR 826, FSR 852, FSR 904, FSR 941, FSR 953, and FSR 955) and 7 (14%) are previously studied or catalogued OCs (KKC1, FSR 795, Cz 22, FSR 828, FSR 856, Cz 24, and NGC 2234). These are OCs with ages in the range 5 Myr to 1 Gyr, at distances from the Sun 1.28 < d� (kpc) < 5.78 and Galactocentric distances 8.5 < RGC(kpc) < 12.9. We also derive parameters for the previously analysed OCs Cz 22 and NGC 2234. Five (10%) candidates are classified as uncertain cases, and the remaining objects are probable field fluctuations.

Astrophysical parameters of 14 open clusters projected close to the Galactic plane

Aims. Astrophysical parameters (age, reddening, distance, core and cluster radii) of 14 open clusters (OCs) projected close to the Galactic plane are derived with 2MASS photometry. The OCs are Be 63, Be 84, Cz 6, Cz 7, Cz 12, Ru 141, Ru 144, Ru 172, FSR 101, FSR 1430, FSR 1471, FSR 162, FSR 178, and FSR 198. The OCs Be 63, Be 84, Ru 141, Ru 144, and Ru 172 are studied in more detail than in previous works, while the others have astrophysical parameters derived for the first time. Methods. We analyse the colour−magnitude diagrams (CMDs) and stellar radial density profiles (RDPs) built after field-star decontamination and colour-magnitude filtered photometry. Field-star decontamination is applied to uncover the cluster’s intrinsic CMD morphology, and colour−magnitude filters are used to isolate stars with a high probability of being cluster members in view of structural analyses. Results. The open clusters of the sample are located at d� = 1.6−7.1 kpc from the Sun and at Galactocentric distances 5.5−11.8 kpc, with age in the range 10 Myr to 1.5 Gyr and reddening E(B−V) in the range 0.19−2.56 mag. The core and cluster radii are in the range 0.27−1.88 pc and 2.2−11.27 pc, respectively. Cz 6 and FSR 198 are the youngest OCs of this sample, with a population of pre-main sequence (PMS) stars, while FSR 178 is the oldest cluster.

Tracing the Galactic spiral structure with embedded clusters

In the present work we investigate the properties of 18 embedded clusters (ECs). The sample includes 11 previously known clusters and we report the discovery of 7 ECs on WISE images, thus complementing our recent list of 437 new clusters. The main goal is to use such clusters to shed new light on the Galactic structure by tracing the spiral arms with cluster distances. Our results favour a four-armed spiral pattern tracing three arms, Sagitarius-Carina, Perseus, and the Outer arm. The SagitariusCarina spiral arm is probed in the borderline of the third and fourth quadrants at a distance from the Galactic centre of d1 � 6.4 kpc adopting R⊙ = 7.2 kpc, or d2 � 7.2 kpc for R⊙ = 8.0 kpc. Most ECs in our sample are located in the Perseus arm that is traced in the second and third quadrants and appear to be at Galactocentric distances in the range d1 = 9 10.5 kpc or d2 = 9.8 11.3 kpc. Dolidze 25, Bochum 2, and Camargo 445 are located in the Outer arm that extends along the second and third Galactic quadrants with a distance from the Galactic centre in the range of d1 = 12.5 14.5 kpc or d2 = 13.5 15.5 kpc. We find further evidence that in the Galaxy ECs are predominantly located within the thin disc and along spiral arms. They are excellent tools for tracing these Galactic features and therefore new searches for ECs can contribute to a better understanding of the Galactic structure. We also report an EC aggregate located in the Perseus arm.

Towards a census of the Galactic anticentre star clusters – III. Tracing the spiral structure in the outer disc

In this paper we investigate the nature of 27 star cluster candidates, most of them projected towards the Galactic anticentre. We derive fundamental parameters for 20 confirmed clusters, among these 7 are new identifications. Four of the remaining are uncertain cases that require deeper photometry to establish their nature, and 4 are probably field fluctuations. In addition, we provide a partial census of the open clusters towards the Galactic anticentre. We also include in this study some interesting objects outside the anticentre region, in the second and third Galactic quadrants, mainly in the Perseus and Outer arms. These clusters confirm the extension of the Outer arm along the third quadrant. We also point out that the embedded cluster FSR 486, at a distance of 7.2 +/- 1.3 kpc from de Sun, is projected on the line of sight of the Local Group irregular dwarf galaxy IC 10. Thus, part of the unusual properties of IC 10 may be explained by a Galactic contamination. We point out the importance of embedded clusters in tracing the spiral structure.

New Galactic embedded clusters and candidates from a WISE Survey

Abstract 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 ° ⩽ l ⩽ 290 ° and - 25 ° ⩽ b ⩽ 20 ° , 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.

Towards a census of the Galactic anticentre star clusters – II. Exploring lower overdensities

We investigate the nature of 48 low-level stellar overdensities (from Froebrich, Scholz and Raftery catalogue – FSR07) projected towards the Galactic anticentre and derive fundamental parameters for the confirmed clusters, thus improving the open cluster (OC) census in that direction. Parameters are derived with field-star decontaminated photometry, colour–magnitude filters and stellar radial density profiles. Among the 48 targets, we identified 18 star clusters, six previously studied OCs and seven probable clusters that require deeper photometry to establish the nature. We discovered seven new clusters, six of them forming an association of clusters with BPI 14, FSR 777, Kronberger 1 and Stock 8 in the region of the nebula IC 417 and related to the Aur OB2 association, and one embedded in the nebula Sh2-229. We also derive parameters for these three non-FSR07 clusters, because they are important in determining the structure of the Galactic anticentre. Thus, 58 objects are analysed in this work and we could derive fundamental parameters for 28 of them. The scenario in the IC 417 star-forming region is consistent with a sequential event. FSR 888 and FSR 890 are embedded in Sh2-249 within the Gem OB1 association. According to the distance derived for these clusters and those in the association of clusters, both Aur OB2 and Gem OB1 are located in the Perseus arm.

Discovery of two embedded clusters with WISE in the high Galactic latitude cloud HRK 81.4−77.8

Molecular clouds at very high latitude (b > 60 ◦ ) away from the Galactic plane are rare and in general are expected to be non-star-forming. However, we report the discovery of two embedded clusters (Camargo 438 and Camargo 439) within the highlatitude molecular cloud HRK 81.4-77.8 using WISE. Camargo 439 with Galactic coordinates l = 81.11 ◦ and b = 77.84 ◦ is an � 2 Myr embedded cluster (EC) located at a distance from the Sun of d⊙ = 5.09±0.47 kpc. Adopting the distance of the Sun to the Galactic centre R⊙ = 7.2 kpc we derive for Camargo 439 a Galactocentric distance of RGC = 8.70±0.26 kpc and a vertical distance from the plane of 4.97±0.46 kpc. Camargo 438 at l = 79.66 ◦ and b = 78.86 ◦ presents similar values. The derived parameters for these two ECs put HRK 81.4-77.8 in the halo at a distance from the Galactic centre of � 8.7 kpc and � 5.0 kpc from the disc. Star clusters provide the only direct means to determine the high latitude molecular cloud distances. The present study shows that the molecular cloud HRK 81.4-77.8 is currently forming stars, apparently an unprecedented event detected so far among high latitude clouds. We carried out a preliminary orbit analysis. It shows that this ECs are the most distant known embedded clusters from the plane and both cloud and clusters are probably falling ballistically from the halo onto the Galactic disc, or performing a flyby.

New detections of embedded clusters in the Galactic halo

Until recently it was thought that high Galactic latitude clouds were a non-star-forming ensemble. However, in a previous study we reported the discovery of two embedded clusters (ECs) far away from the Galactic plane (

Characterizing star cluster formation with WISE: 652 newly found star clusters and candidates

\sim5