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We analyse the nature of a sample of stellar overdensities that we found projected on the Carina complex. This study is based on the Two Micron All Sky Survey photometry and involves the photometry decontamination of field stars, elaboration of intrinsic colour-magnitude diagrams [CMDs; J × (J - Ks)], colour-colour diagrams (J - H) × (H - Ks), and radial density profiles, in order to determine the structure and the main astrophysical parameters of the best candidates. The verification of an overdensity as an embedded cluster requires a CMD consistent with a PMS content and MS stars, if any. From these results, we are able to verify if they are, in fact, embedded clusters. The results were, in general, rewarding: in a sample of 101 overdensities, the analysis provided 15 candidates, of which three were previously catalogued as clusters (CCCP-Cl 16, Treasure Chest, and FSR 1555), and the 12 remaining are discoveries that provided significant results, with ages not above 4.5Myr and distances compatible with the studied complex. The resulting values for the differential reddening of most candidates were relatively high, confirming that these clusters are still (partially or fully) embedded in the surrounding gas and dust, as a rule within a shell. Histograms with the distribution of the masses, ages, and distances were also produced, to give an overview of the results. We conclude that all the 12 newly found embedded clusters are related to the Carina complex. [ABSTRACT FROM AUTHOR]

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 high-latitude 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 CLQ = 5.09 ± 0.47 kpc. Adopting the distance of the Sun to the Galactic Centre R8857; = 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&#176.86 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 these ECs are the most distant known ECs from the plane and both cloud and clusters are probably falling ballistically from the halo on to the Galactic disc, or performing a flyby. [ABSTRACT FROM AUTHOR]

Context. VISTA Variables in the Vía Láctea (VVV) is one of six ESO Public Surveys using the 4 meter Visible and Infrared Survey Telescope for Astronomy (VISTA). The VVV survey covers the Milky Way bulge and an adjacent section of the disk, and one of the principal objectives is to search for new star clusters within previously unreachable obscured parts of the Galaxy. Aims. The primary motivation behind this work is to discover and analyze obscured star clusters in the direction of the inner Galactic disk and bulge. Methods. Regions of the inner disk and bulge covered by the VVV survey were visually inspected using composite JHKS color images to select new cluster candidates on the basis of apparent overdensities. DR1, DR2, CASU, and point spread function photometry of 10 × 10 arcmin fields centered on each candidate cluster were used to construct color-magnitude and color-color diagrams. Follow-up spectroscopy of the brightest members of several cluster candidates was obtained in order to clarify their nature. Results. We report the discovery of 58 new infrared cluster candidates. Fundamental parameters such as age, distance, and metallicity were determined for 20 of the most populous clusters. [ABSTRACT FROM AUTHOR]

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

ABSTRACT It is currently widely accepted that open star clusters and stellar associations result from the evolution of embedded star clusters. Parameters such star formation efficiency, time-scale of gas removal and velocity dispersion can be determinants of their future as bound or unbound systems. Finding objects at an intermediate evolution state can provide constraints to model the embedded cluster evolution. In the H ii region IC 1396, Trumpler 37 is an extended young cluster that presents characteristics of an association. We employed the Two Micron All Sky Survey (2MASS) photometry for analysing its structure and stellar content, and determining its astrophysical parameters. We also analysed 11 bright-rimmed clouds in IC 1396 in order to search for young infrared star clusters, and the background open star cluster Teutsch 74, to verify whether it has any contribution to the observed stellar density profile of Trumpler 37. The derived parameters and comparison with template objects from other studies lead us to conclude that Trumpler 37, rather than as a star cluster, will probably emerge from its molecular cloud as an OB association. [ABSTRACT FROM AUTHOR]

ABSTRACT We investigate the nature of 14 embedded clusters (ECs) related to a group of four H ii regions, Sh2-235, Sh2-233, Sh2-232 and Sh2-231, in the giant molecular cloud G174 + 2.5. Projected towards the Galactic anticentre, these objects are possible examples of the collect-and-collapse scenario. We derive astrophysical parameters ( age, reddening, distance, core and cluster radii) for the ECs and investigate the relationship between these parameters. Parameters are derived with field-star-decontaminated 2MASS colour-magnitude diagrams (CMDs) and stellar radial density profiles. The CMDs of these young clusters are characterized by a poorly populated main sequence and a significant number of pre-main-sequence stars, affected by differential reddening. The ECs are KKC 11, FSR 784, Sh2-235 East2, Sh2-235 Cluster, Sh2-233 SE Cluster, BDSB 73, Sh2-235B Cluster, BDSB 72, BDSB 71, Sh2-232 IR Cluster, PCS 2, and the newly found clusters CBB 1 and CBB 2. We were able to derive fundamental parameters for all ECs in the sample. Structural parameters are derived for FSR 784, Sh2-235 Cluster and Sh2-235 East2. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper investigates the star formation rate (SFR) in the solar neighbourhood. First, we build the local age distribution function (ADF) with an updated sample of 442 star clusters located at less than 1 kpc from the Sun. Next, we define the SFR, compute the individual mass evolution of a population of artificial clusters covering the broad range of parameters observed in actual clusters, and assume 100 M ⊙ as the low-mass limit for effective cluster observation. This leads to a simulated ADF, which is compared to the low-noise solar neighbourhood ADF. The best match corresponds to a non-constant SFR presenting two conspicuous excesses for ages ≤9 Myr and between 220-600 Myr (the local starburst). The average SFR is , corresponding to the average surface SFR . These values are consistent with the SFR inferred from embedded clusters (ECs), but much lower (≲16 per cent) than that implied by field stars. Both the local starburst and the recent star formation period require to be described. The simulations show that 91.2 ± 2.7 per cent of the clusters created in the solar neighbourhood do not survive the first 10 Myr, which is consistent with the rate of EC dissolution. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]

We investigate the degree of spatial correlation among extended structures in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). To this purpose, we work with subsamples characterized by different properties such as age and size, taken from the updated catalogue of Bica et al. or gathered in the present work. The structures are classified as star clusters or non-clusters (basically, nebular complexes and their stellar associations). The radius distribution functions follow power laws with slopes and maximum radius ( Rmax) that depend on object class (and age). Non-clusters are characterized by and , while young clusters (age ≲10 Myr) have and and old ones (age ≳600 Myr) have and . Young clusters present a high degree of spatial self-correlation and, especially, correlate with star-forming structures, which does not occur with the old ones. This is consistent with the old clusters having been heavily mixed up, since their ages correspond to several LMC and SMC crossing times. On the other hand, with ages corresponding to fractions of the respective crossing times, the young clusters still trace most of their birthplace structural pattern. Also, small clusters , as well as small non-clusters , are spatially self-correlated, while their large counterparts of both classes are not. The above results are consistent with a hierarchical star formation scenario for the LMC and SMC. [ABSTRACT FROM AUTHOR]

We employ Infrared Telescope Facility SpeX near-infrared (NIR; 0.8–2.4 μm) spectra to investigate the stellar population (SP), active galactic nuclei (AGN) featureless continuum (FC) and hot dust properties in nine Sy 1 and 15 Sy 2 galaxies. Both thestarlight code and the hot dust as an additional base element were used for the first time in this spectral range. We found evidence of correlation among the equivalent widths Si i 1.59 μm × Mg i 1.58 μm, equally for both kinds of activity. Part of the and strengths may be related to galaxy inclination. Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies: the hot dust component is required to fit the K-band spectra of ∼90 per cent of the Sy 1 galaxies, and only of ∼25 per cent of the Sy 2; about 50 per cent of the Sy 2 galaxies require an FC component contribution ≳20 per cent, while this fraction increases to about 60 per cent in the Sy 1; also, in about 50 per cent of the Sy2, the combined FC and young components contribute with more than 20 per cent, while this occurs in 90 per cent of the Sy1, suggesting recent star formation in the central region. The central few hundred parsec of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1 μm CN band can be used as a tracer of intermediate-age SPs. The simultaneous fitting of SP, FC and hot dust components increased in ∼150 per cent the number of AGNs with hot dust detected and the mass estimated. The NIR emerges as an excellent window to study the SP of Sy 1 galaxies, as opposed to the usually heavily attenuated optical range. Our approach opens a new way to investigate and quantify the individual contribution of the three most important NIR continuum components observed in AGNs. [ABSTRACT FROM AUTHOR]

The stellar population, metallicity distribution and ionized gas in the elliptical galaxies NGC 6868 and 5903 are investigated in this paper by means of long-slit spectroscopy and stellar population synthesis. Lick indices in both galaxies present a negative gradient indicating an overabundance of Fe, Mg, Na and TiO in the central parts with respect to the external regions. We found that Mg2 correlates both with Fe i λ5270 and Fe i λ5335, suggesting that these elements probably underwent the same enrichment process in NGC 6868. However, only a marginal correlation of Mg2 and Fe i λ5270 occurs in NGC 5903. The lack of correlation between computed galaxy mass and the Mg2 gradient suggests that these elliptical galaxies were formed by merger events. The stellar population synthesis shows the presence of at least two populations with ages of 13 and 5 Gyr old in both galaxies. We have estimated the metallicity of the galaxies using single-aged stellar population (SSP) models. The central region of NGC 6868 presents a deficiency of alpha elements with respect to iron and solar metallicity. The external parts present a roughly uniform distribution of ratios and metallicities ranging from and solar. A similar conclusion applies to NGC 5903. Concerning the emitting gas conspicuously detected in NGC 6868, we test three hypotheses as ionizing source: an H ii region, post-AGB (asymptotic giant branch) stars and an active galactic nucleus (AGN). Diagnostic diagrams involving the ratios and indicate that values measured in the central region of NGC 6868 are typical of LINERs (Low-Ionization Nuclear Emission-Line Regions). Together with the stellar population synthesis, this result suggests that the main source of gas ionization in NGC 6868 is non-thermal, produced by a low-luminosity AGN, probably with some contribution of shocks to explain ionization at distances of from the nucleus. [ABSTRACT FROM AUTHOR]