A deep and wide-field view at the IC 2944 / 2948 complex in Centaurus

TL;DR

This study provides a comprehensive deep-field analysis of the IC 2944/2948 complex, revealing multiple star groups at different distances, their properties, and kinematic deviations from the Milky Way rotation curve.

Contribution

It offers new detailed photometric, spectroscopic, and kinematic data on star groups in the IC 2944/2948 region, including their ages, masses, and spatial distribution.

Findings

Identified two young star groups at 2.3 and 3.2 kpc with pre-main sequence populations.

Derived initial mass functions with slopes slightly shallower than Salpeter.

Detected a third distant group possibly in the Sagittarius-Carina arm.

Abstract

We employed the ESO MPI wide-field camera and obtained deep images in the VIc pass-bands in the region of the IC 2944/2948 complex (l ~ 294; b ~ -1), and complemented them with literature and archival data. We used this material to derive the photometric, spectroscopic and kinematic properties of the brightest (V < 16) stars in the region. The VI deep photometry on the other end, helped us to unravel the lower main sequence of a few, possibly physical, star groups in the area. Our analysis confirmed previous suggestions that the extinction toward this line of sight follows the normal law (Rv = 3.1). We could recognize B-type stars spread in distance from a few hundred pc to at least 2 kpc. We found two young groups (age ~ 3 Myr) located respectively at about 2.3 and 3.2 kpc from the Sun. They are characterized by a significant variable extinction (E(B-V) ranging from 0.28 to 0.45 mag), and host a significant pre-main sequence population. We computed the initial mass functions for these groups and obtained slopes Gamma from -0.94 to -1.02 (e_Gamma = 0.3), in a scale where the classical Salpeter law is -1.35. We estimated the total mass of both main stellar groups in ~ 1100$ and ~ 500$ Mo, respectively. Our kinematic analysis indicated that both groups of stars deviate from the standard rotation curve of the Milky Way, in line with literature results for this specific Galactic direction. Finally, along the same line of sight we identified a third group of early-type stars located at ~ 8 kpc from the Sun. This group might be located in the far side of the Sagittarius-Carina spiral arm.