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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorNewberg, Heidi
dc.contributorRoberge, W. G. (Wayne G.)
dc.contributorBrown, Ethan
dc.contributorHenshaw, William D.
dc.contributor.authorMartin, Charles
dc.date.accessioned2021-11-03T08:39:00Z
dc.date.available2021-11-03T08:39:00Z
dc.date.created2016-09-27T14:07:52Z
dc.date.issued2016-08
dc.identifier.urihttps://hdl.handle.net/20.500.13015/1748
dc.descriptionAugust 2016
dc.descriptionSchool of Science
dc.description.abstractThe focus of this thesis is the mapping of substructure in the Milky Way Galaxy using data from the Sloan Digital Sky Survey (SDSS), in particular Blue Horizontal Branch stars (BHBs) and stars on the red giant branch. These bright stars are useful when mapping the spatial distribution and properties of gravitationally disrupted galaxies and globular clusters in the Milky Way. The bright absolute magnitude of these stars allows spectral observations of stars stretching out to about 75 kpc from the Sun. Using spectra of BHB stars we are able to kinematically distinguish moving groups and the spatial overdensities to which they belong. This is in turn useful in the fitting of an orbit and mapping mass distribution of the Milky Way.
dc.description.abstractThe use of BHBs as tracers of stellar debris streams is a common practice and has been useful in the confirmation of kinematic properties of previously identified streams. This work explores less common ways of untangling the velocity signatures of streams traveling radially to our line of sight, and to peer toward the higher density region of the Galactic Center.
dc.description.abstractThrough analysis of blue spectral templates from the SDSS, this thesis proposes that the A0p spectral template selects extreme horizontal branch (EHB) stars, instead of just BHB stars as previously believed. These EHB stars have a bluer color than BHBs and occur less frequently in stellar populations such as globular clusters. Due to the decreased number of stellar populations containing these EHB stars, we show they should be a useful population for mapping nearby galactic moving groups. This thesis identifies several moving groups of EHBs in the Milky Way halo. Some of these have spatial and kinematic similarities to the Virgo Overdensity, Hercules Halo Stream, and Hyllus Stream.
dc.description.abstractThe results of this thesis advance our knowledge of the following stellar halo substructures: the Pisces Stellar Stream, the Hercules-Aquila Cloud, the Hercules Halo Stream, and the Hermus Stream. A study of red giant stars led to the kinematic discovery of the Pisces Stellar Stream. Red giant stars were also examined to determine that the previously identified velocity signature that was suggested for the Hercules-Aquila Cloud was due to disk star contamination and errors in preliminary SDSS velocities. The Hercules Halo Stream is a previously unidentified structure that could be related to the Hercules-Aquila Cloud, and was discovered as a velocity excess of SDSS BHB stars. It is suggested that the Hermus Stream is embedded in the disrupted remain of a dwarf galaxy of mass $\sim10^6M_{Sun}$. This finding is the result of identification of a moving group of BHBs around the narrow spatial distribution of the Hermus Stream. Under the assumption that the Hermus Stream results from a globular cluster originally within that dwarf galaxy progenitor, an orbit is fit to the Hermus Stream that rules out a connection with the Phoenix Stream.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectPhysics
dc.titleMapping Milky Way halo structure with blue horizontal branch stars
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid177469
dc.digitool.pid177470
dc.digitool.pid177471
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Physics, Applied Physics, and Astronomy


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