TY  - GEN
ID  - heidok22559
TI  - Revealing the secrets of Westerlund 2 - A young massive star cluster observed with the Hubble Space Telescope
Y1  - 2017///
AV  - public
N2  - We present a detailed study of the Galactic young massive star cluster Westerlund 2 (Wd2) using an optical and near-infrared high resolution multi-band survey observed with the Hubble Space Telescope. Images obtained in H? and Pa? filters allowed us to derive a high-resolution pixel-to-pixel E(B ? V)_g gas extinction map. This map helped us to individually deredden the stellar photometry, to identify the cluster population, and to determine the properties of Wd2, such as distance (d = 4.16 kpc), total-to-selective extinction (RV = 3.95), and age (1.04 ± 0.72Myr). We identified 240 bona fide pre-main-sequence H? excess emitters indicating active disk accretion. A careful analysis of the radial dependence of the H? excess emission shows a 60% lower mass accretion rate in the cluster center, indicating a more rapid disk dispersal in close proximity to the massive OB-stars. We performed state-of-the-art artificial star tests to study the completeness-corrected spatial distribution of the stars. This revealed that Wd2 consists of two subclusters. Additionally, we determined the present-day mass function (PDMF) with a slope of G = ?1.53 ± 0.05, which translates to a total
stellar cluster mass of (3.6±0.3)·10^4 M_sun. The spatial analysis of the PDMF and the young age of Wd2 indicates that the cluster is, most likely primordial, mass segregated. A spatially uniformly distributed low-mass (< 0.15 M_sun) population, extending into the gas and dust cloud, as well as a confined region of reddened stars, most likely caused by a foreground CO cloud, suggests that cloud-cloud collision might be the origin of the formation of Wd2.
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/22559/
A1  - Zeidler, Peter
ER  -