eprintid: 22559
rev_number: 13
eprint_status: archive
userid: 2947
dir: disk0/00/02/25/59
datestamp: 2017-01-26 08:53:11
lastmod: 2017-03-14 15:54:35
status_changed: 2017-01-26 08:53:11
type: doctoralThesis
metadata_visibility: show
creators_name: Zeidler, Peter
title: Revealing the secrets of Westerlund 2 - A young massive star cluster observed with the Hubble Space Telescope
subjects: ddc-520
divisions: i-714000
adv_faculty: af-13
abstract: 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 Hα and Paβ 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 Hα excess emitters indicating active disk accretion. A careful analysis of the radial dependence of the Hα 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.
date: 2017
id_scheme: DOI
id_number: 10.11588/heidok.00022559
ppn_swb: 1656886049
own_urn: urn:nbn:de:bsz:16-heidok-225598
date_accepted: 2017-01-18
advisor: HASH(0x561a62857168)
language: eng
bibsort: ZEIDLERPETREVEALINGT2017
full_text_status: public
citation:   Zeidler, Peter  (2017) Revealing the secrets of Westerlund 2 - A young massive star cluster observed with the Hubble Space Telescope.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/22559/1/PhD_Thesis_final.pdf