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A Spectroscopic Survey of Chemical E...

Vargus, Luis Carlos.

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A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies./
作者:	Vargus, Luis Carlos.
面頁冊數:	229 p.
附註:	Source: Dissertation Abstracts International, Volume: 76-11(E), Section: B.
Contained By:	Dissertation Abstracts International76-11B(E).
標題:	Astronomy. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3663720
ISBN:	9781321988932

A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies.
Vargus, Luis Carlos.

A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies. - 229 p.

Source: Dissertation Abstracts International, Volume: 76-11(E), Section: B.

Thesis (Ph.D.)--Yale University, 2015.

Dwarf spheroidal galaxies (dSphs, Mv [special characters omitted] --13) are the most abundant galaxy type in the Local Group, and more continue to be discovered especially towards lower luminosities. Chemical abundances beyond the overall stellar metallicity have been limited to small samples in the Milky Way ultra-faint dSphs (UFDs), and have not been measured in the M31 dSphs. Thus, many chemical evolution properties of these galaxies remain poorly understood. To better constrain the chemical evolution timescale of these systems, we undertake a spectroscopic study of their [alpha/Fe] abundance distribution. We implement a technique to measure [alpha/Fe] and [Fe/H] abundances from medium resolution individual stellar spectra by fitting them against a grid of template spectra.

ISBN: 9781321988932Subjects--Topical Terms:

517668
Astronomy.

A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies.
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245 1 2 $a A Spectroscopic Survey of Chemical Evolution in Local Group Dwarf Satellite Galaxies.
300 $a 229 p.
500 $a Source: Dissertation Abstracts International, Volume: 76-11(E), Section: B.
500 $a Adviser: Marla C. Geha.
502 $a Thesis (Ph.D.)--Yale University, 2015.
520 $a Dwarf spheroidal galaxies (dSphs, Mv [special characters omitted] --13) are the most abundant galaxy type in the Local Group, and more continue to be discovered especially towards lower luminosities. Chemical abundances beyond the overall stellar metallicity have been limited to small samples in the Milky Way ultra-faint dSphs (UFDs), and have not been measured in the M31 dSphs. Thus, many chemical evolution properties of these galaxies remain poorly understood. To better constrain the chemical evolution timescale of these systems, we undertake a spectroscopic study of their [alpha/Fe] abundance distribution. We implement a technique to measure [alpha/Fe] and [Fe/H] abundances from medium resolution individual stellar spectra by fitting them against a grid of template spectra.
520 $a In the first part of the thesis, we apply our technique to seven UFDs (--1.5 > Mv > --7.1) and measure [alpha/Fe] vs. [Fe/H] for at least five stars per galaxy. With the exception of two faint systems, we measure a decrease in [alpha/Fe] with increasing [Fe/H]. Using the [alpha/Fe] ratio as a chemical clock tracing the (delayed) Type Ia supernovae enrichment, we suggest the observed trend is evidence for internal evolution on a timescale of at least 100 Myr, implying that UFDs were able to retain a non-negligible fraction of their baryonic content after the initial burst of star formation, in spite of their shallow gravitational potentials.
520 $a In the second part of the thesis, we measure [alpha/Fe] and [Fe/H] for more than 200 member stars of eight M31 satellites (five dSphs as well as three brighter dwarf ellipticals; --7.4 > Mv > --16.4). We find that not all M31 dSphs follow the trend of decreasing [alpha/Fe] with rising [Fe/H] observed in MW dSphs with comparable luminosities, hinting at a larger degree of diversity in the chemical evolution of dwarf satellites than previously observed. We calculate galaxy-wide average [alpha/Fe] values between ~ 0.0 and ~ +0.5, suggesting a wide range in the satellites' chemical evolution timescales. We then compare the M31 satellite population to the halo of the MW, and find that a present day M31 satellite population has different chemical properties from the satellites that formed the bulk of the MW outer (accreted) halo. Our MW and M31 satellite dataset represents one of the largest spectroscopic sample available to date, and will be applicable to comparisons with detailed chemical evolution models.
520 $a Motivated by the M31 satellite to MW halo comparison, we identify four M31 outer halo stars for which we are able to measure [alpha/Fe] abundance ratios. We find that, as in the MW halo, the average [alpha/Fe] value is enhanced, and thus is marginally discrepant from the chemical abundance pattern seen in the M31 satellite population. While we are restricted by small number statistics, our measurements lends some support to the idea that the satellites that formed the present day stellar halos were formed from a population of satellites different than those known in the present day.
590 $a School code: 0265.
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