F. F. S. Maia

Characterization and photometric membership of the open cluster NGC 1981

Open clusters belonging to star-forming complexes are the leftovers from the initial stellar generations. The study of these young systems provides constraints to models of star formation and evolution as well as to the properties of the Galactic disc. We aimed at investigating NGC 1981, a young open cluster in the Orion nebula region, using near-IR and BV(RI) c photometric data. We devised a method that accounts for the field contamination and allows to derive photometric membership for the cluster stars. A new cluster centre was determined by Gaussian fittings to the 2D stellar distribution on the sky, and has been used to obtain the radial stellar density profile and the structural parameters. Mass functions were computed for stars inside the cluster limiting radius and total mass estimated from them. Although more easily distinguished by its grouping of six relatively bright stars, an underlying population of faint pre-main-sequence stars is evident in the cluster area. We showed that this population is related to the cluster itself rather than to the nearby Orion nebula cluster. Additionally, a fraction of the cluster low mass stars may have been evaporated from the region in its early evolution leading to the present sparse, loose structure. The estimated parameters of NGC 1981 are core radius R c = 0.09 ± 0.04 pc, limiting radius R lim = 1.21 ± 0.11 pc, age t = 5 ± 1 Myr, distance modulus (m - M) o = 7.9 ± 0.1(380 ± 17 pc), reddening E(B - V) = 0.07 ± 0.03 and total mass m = 137 ± 14 M⊙.

Mass distribution and structural parameters of Small Magellanic Cloud star clusters

In this work we estimate, for the first time, the total masses and mass function slopes of a sample of 29 young and intermediate-age SMC clusters from CCD Washington photometry. We also derive age, interstellar reddening and structural parameters for most of the studied clusters by employing a statistical method to remove the unavoidable field star contamination. Only these 29 clusters out of 68 originally analysed cluster candidates present stellar overdensities and coherent distribution in their colour-magnitude diagrams compatible with the existence of a genuine star cluster. We employed simple stellar population models to derive general equations for estimating the cluster mass based only on its age and integrated light in the B, V, I, C and T1 filter. These equations were tested against mass values computed from luminosity functions, showing an excellent agreement. The sample contains clusters with ages between 60 Myr and 3 Gyr and masses between 300 and 3000 Mo distributed between ~0.5 deg. and ~2 deg. from the SMC optical centre. We determined mass function slopes for 24 clusters, of which 19 have slopes compatible with that of Kroupa IMF (2.3 +/- 0.7), considering the uncertainties. The remaining clusters - H86-188, H86-190, K47, K63 and NGC242 - showed flatter MFs. Additionally, only clusters with masses lower than ~1000 Mo and flatter MF were found within ~0.6 deg. from the SMC rotational centre.

GeMs/GSAOI observations of La Serena 94: an old and far open cluster inside the solar circle

Physical properties were derived for the candidate open cluster La Serena 94, recently unveiled by the VVV collaboration. Thanks to the exquisite angular resolution provided by GeMS/GSAOI, we could characterize this system in detail, for the first time, with deep photometry in JHK

Investigation of Galactic open cluster remnants: the case of NGC 7193*

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Catching Galactic open clusters in advanced stages of dynamical evolution

- bands. Decontaminated JHK

Open cluster characterization via cross-correlation with a spectral library

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Membership probability via control-field colour–magnitude decontamination †

diagrams reach about 5 mag below the cluster turnoff in H. The locus of red clump giants in the colour - colour diagram, together with an extinction law, was used to obtain an average extinction of

Basis for a SOAR Optical Imager Pipeline

A_V =14.18 \pm 0.71

Optical polarimetric and near-infrared photometric study of the RCW95 Galactic H ii region

. The same stars were considered as standard - candles to derive the cluster distance,

Astrophysical parameters of Small Magellanic Cloud star clusters

8.5 \pm 1.0