Young stars in the Carina Nebula Complex

The Carina Nebula Complex is known to be an active star-formation
region. This work presents a large catalogue of point-like sources
assembled from archive data of the Infrared Array Camera (IRAC)
onboard the Spitzer Space Telescope. This catalogue covers a region
of 2.3 deg × 3.0 deg, which makes it the most extendended
mid-infrared survey undertaken of the Carina Nebula Complex to
date. From the catalogue a subsample of candidate young stellar
objects is extracted utilising the fact that young stellar objects
exhibit typical mid-infrared excesses. These catalogues are
employed to characterise the young stellar population of the Carina
Nebula Complex. Using them, it was possible to identify three new
extended green objects and five compact green objects and find the
probable sources for 28 further objects connected with jets emitted
from young stars, such as molecular hydrogen emission-line objects
and Herbig-Haro jets. For 17 of them, observational data from the
near-infrared (from HAWK-I and 2MASS) to the far-infrared (from the
Herschel Space Observatory) could be collected and their spectral
energy distributions fitted. From the fit parameters, stellar
characteristics such as stellar and disk masses could be estimated.
No young stellar objects with masses above 10 M_sol could be
evidenced, pointing towards an intermediate-mass population
currently forming. It could be shown that the Gum 31 region on the
outer periphery of the Carina Nebula Complex is not only part of
the complex but also an important centre of star formation. A large
sample of candidate young stellar object was obtained from the WISE
All-Sky Data Release, which allowed a detailed comparison with both
the candidate young stellar objects from the IRAC catalogue and
those identified from Herschel observations. Evidence could be
found that two modes of triggered star formation are going on in
the HII region: Young stellar objects are found in and in front of
dust pillars, which is an indicator of radiative triggering, and a
‘collect and collapse’ model of the region was shown to produce
results in agreement with the observations. An objective and
large-scale search for clusters of young stellar objects in the
complex was performed using a nearest-neighbour algorithm. This
search derived 22 clusters not described before. Nine of those are
new detections in the fields of previous studies of clusters while
the majority are found in fields surveyed for clusters for the
first time here. Clusters are also found in agreement with previous
studies where study fields overlap, thus corroborating the validity
of the study. It is found that ∼40% of the young stellar objects in
the Carina Nebula Complex occur in clusters while up to 60% are
part of a distributed population. A total population for the 2.3
deg × 3.0 deg study field of ∼200 000 young stars is estimated.