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Young Massive Clusters Near the Galactic Center: Initial Mass Function and Stellar Evolution.

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Title:Young Massive Clusters Near the Galactic Center: Initial Mass Function and Stellar Evolution.
Authors:Hosek, Matthew W., Jr
Contributors:Astronomy (department)
Date Issued:Aug 2018
Publisher:University of Hawaiʻi at Mānoa
Abstract:With projected distances of just ~30 pc from Sgr A*, the Arches and Quintuplet clusters are
valuable probes of star formation in the extreme Galactic Center (GC) environment. Of particular
interest is the Initial Mass Function (IMF), which yields critical insight into the physics driving
star formation and is a vital ingredient in many areas of astronomy. We use multi-epoch Hubble
Space Telescope (HST) observations to obtain high-precision proper motions of stars beyond the
central 25” of these clusters for the first time, calculating cluster membership probabilities down
to ~2 M. We achieve significantly cleaner cluster samples than is possible through photometric
methods due to severe differential extinction in the field. For the Arches cluster, we 1) measure
the stellar radial density profile out to 3 pc for the first time, finding no evidence of a tidal radius
and demonstrating that the cluster is much larger than predicted; 2) combine this sample with
HST observations of Westerlund 1 to measure the extinction law of highly reddened stars in the
Galactic plane between 0.8 μm – 2.2 μm, revealing it to be inconsistent with a single power-law
(contrary to long-held assumptions) and significantly steeper than commonly-used extinction laws;
and 3) use these observations with K-band spectroscopy to make the first proper motion-based
IMF measurement of the cluster, finding significant deviations from the local IMF and suggesting
that the IMF of the GC is non-standard. In addition, we show current progress on the analysis of
the Quintuplet cluster along with a science case for future studies of both clusters with the James
Webb Space Telescope.
Description:Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018.
Rights:All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: Ph.D. - Astronomy

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