Stellar populations in the Carina region. The Galactic plane at l = 291º

MOLINA LERA, JOSÉ ALEJO; BAUME, GUSTAVO LUIS; GAMEN, ROBERTO; COSTA, E.; CARRARO, GIOVANNI

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2016 vol. 592

0004-6361

Context. Previous studies of the Carina region have revealed itscomplexity and richness as well as a significant number of early-typestars. However, in many cases, these studies only concentrated on thecentral region (Trumpler 14/16) or were not homogeneous. This latteraspect, in particular, is crucial because very different ages anddistances for key clusters have been claimed in recent years. Aims: The aim of this work is to study in detail an area of the Galacticplane in Carina, eastward η Carina. We analyze the properties ofdifferent stellar populations and focus on a sample of open clusters andtheir population of young stellar objects and highly reddened earlystars. We also studied the stellar mass distribution in these clustersand the possible scenario of their formation. Finally, we outline theGalactic spiral structure in this direction. Methods: We obtaineddeep and homogeneous photometric data (UBVIKC) for six youngopen clusters: NGC 3752, Trumpler 18, NGC 3590, Hogg 10, 11, and 12,located in Carina at l ~ 291°, and their adjacent stellar fields,which we complemented with spectroscopic observations of a few selectedtargets. We also culled additional information from the literature,which includes stellar spectral classifications and near-infraredphotometry from 2MASS. We finally developed a numerical code thatallowed us to perform a homogeneous and systematic analysis of the data.Our results provide more reliable estimates of distances, colorexcesses, masses, and ages of the stellar populations in this direction. Results: We estimate the basic parameters of the studied clustersand find that they identify two overdensities of young stellarpopulations located at about 1.8 kpc and 2.8 kpc, with EB - V~ 0.1 - 0.6. We find evidence of pre-main-sequence populations insidethem, with an apparent coeval stellar formation in the most conspicuousclusters. We also discuss apparent age and distance gradients in thedirection NW-SE. We study the mass distributions of the covered clustersand several others in the region (which we took form the literature).They consistently show a canonical IMF slope (the Salpeter one). Wediscover and characterise an abnormally reddened massive stellarpopulation, scattered between 6.6 and 11 kpc. Spectroscopic observationsof ten stars of this latter population show that all selected targetswere massive OB stars. Their location is consistent with the position ofthe Carina-Sagittarius spiral arm.