Multiwavelenght study in the region of IRAS sources 16571-4029 and 16575-4023

Abstract

We studied the stellar populations and their associated interstellar medium structures located in the region of IRAS 16571-4029 and 16575-4023 sources, aiming to evaluate their distance and their main physical parameters. We focused our attention on the embedded cluster DBS 113 and its associated HII region RCW 116B.For the study, optical images were obtained using wide band and narrow band filters (ugri andOIII, OIIIC, H, HC, SII respectively) together with infrared (K band) spectra for several starsin the region of DBS 113. These data were complemented with available information from the literature and photometric multi-band data from several surveys at optical (VPHAS+), infrared (2MASS, VVV, WISE) and radio (SGPS, PMN) spectral ranges. Astrometic and photometric data from GAIA DR2 in the region were also taken into account.All the obtained spectra in DBS 113 region correspond to early type stars (OB). In general, weidentified in this region 2 O-type, í 20 B-type stars, í 25 probable pre-main sequence ones, and 10 candidates to young stellar objects. We also built their stellar energy distributions ranging from 0.3 to 22 m. We found an abnormal behaviour of the reddening law (RV = 4:0) and a corresponding spectrophotometric distance from optical/infrared data consistent with the distance computed from GAIA measurements (d í 2 kpc). This value locates this cluster at the inner side of the Sagittarius-Carina Galactic arm and is different from the traditionally adopted kinematic distance of 1-1.2 kpc, based on hydrogen recombination line at millimeter wavelengths. This difference was explained by the presence of an hydrogen expanding bubble with a central velocity relative the molecular cloud.The new proposed distance value allowed to estimate more precisely the parameter values of the HII region RCW116B and to describe the energetic balance among the emission of most massive stars, the ionization of the region and the heated dust. Regarding the IRAS 16575-4023 source, we found that the brightest star in this region is a foreground object andwe also identified a set of OB stars candidates with high absorption values (AV í 23), located behind the molecular cloud AGAL345.336+01.021.