A5087158618- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Astronomical and nuclear sciences
University of Notre Dame
2017-2021
Joint Institute for Nuclear Astrophysics
2017-2021
Abstract Understanding the evolution of carbon and iron in Milky Way’s halo is importance because these two elements play crucial roles constraining star formation, Galactic assembly, chemical early universe. Here we explore spatial distributions carbonicity, [C/Fe], metallicity, [Fe/H], system based on medium-resolution ( R ∼ 1300) spectroscopy ∼58,000 stars southern hemisphere from AAOmega Evolution Structure (AEGIS) survey. The AEGIS carbonicity map exhibits a positive gradient with...
We obtain estimates of stellar atmospheric parameters for a previously published sample 1777 relatively bright (9 < B 14) metal-poor candidates from the Hamburg/ESO Survey. The original Frebel et al. analysis these stars was only able to derive [Fe/H] and [C/Fe] subset sample, due limitations in methodology then available. A new spectroscopic pipeline has been used Teff, log g, [Fe/H], almost entire dataset. This is very local - about 90% are located within 0.5 kpc Sun. consider...
We present an examination of the metallicity distribution function outermost stellar halo Galaxy based on analysis both local (within 4 kpc Sun, ~16,500 stars) and non-local (~21,700 samples. These samples were compiled using spectroscopic metallicities from Sloan Digital Sky Survey photometric SkyMapper Southern Survey. detect a negative gradient in (r > 35 Galactic center), find that frequency very metal-poor ([Fe/H] < -2.0) stars outer-halo region reaches up to ~60% our most distant...
Abstract We present a chemodynamical analysis of low-resolution ( R ∼ 1300) spectroscopy ∼50,000 stars from the AAOmega Evolution Galactic Structure survey, focusing on two key populations (in total) 650 carbon-enhanced metal-poor (CEMP) within disk system Milky Way: mildly prograde population L z < 1000 kpc km s −1 ) and strongly > ). Based their chemical kinematic characteristics, comparisons with similar found in recent literature, we tentatively associate former an ex situ...
Abstract We derive dynamical parameters for a large sample of 446 r -process-enhanced (RPE) metal-poor stars in the halo and disk systems Milky Way, based on data releases from R -Process Alliance, supplemented by additional literature samples. This represents more than 10-fold increase size relative to that previously considered Roederer et al. and, design, covers larger range -process-element enrichment levels. test number clustering analysis methods derived orbital energies other this...
Abstract We present the first release of a large-scale study relatively bright ( V < 13.5) metal-poor stars observed with Southern African Large Telescope (SALT), based on high-resolution spectra 50 resolving power R ∼ 40,000 and S/N 20 per pixel at 4300 Å. The elemental abundances C, Sr, Ba, Eu are reported, as well several α -elements (Mg, Ca, Sc, Ti, V) iron-peak elements (Mn, Co, Ni, Zn). find diverse array abundance patterns, including consistent signatures carbon-enhanced CEMP- i r...
Abstract The study of extremely metal-poor (EMP; [Fe/H] &lt;−3.0) and ultra (UMP; &lt;−4.0) stars is crucial for better understanding first-star nucleosynthesis constraining the initial mass function in early Universe. However, UMP discovered past 25 years only number ~25. A few recent theoretical studies have pointed out that there likely to exist large numbers EMP periphery Galactic halo, at distances exceeding 30-50 kpc. We present identifications several new EMP/UMP introduce a...
Abstract The RAVE survey obtains moderate-resolution (R ~ 7500) spectroscopy of relatively bright stars in the region Ca triplet, and derives estimates stellar atmospheric parameters (Teff, log g, [Fe/H]) abundance for a limited number elements. sample is selected on apparent magnitude, effectively removing biases typically associated with searches metal-poor such as metallicity, evolutionary status, or Galactic population membership. For past several years, we have been obtaining...
Abstract The AAOmega Evolution of Galactic Structure (AEGIS) survey (P.I. Keller) was a moderate scale (45 nights) spectroscopic carried out with the multi-fiber spectrograph at Anglo-Australian Telescope. input catalogue for observations derived from photometry approximately 200 two-degree diameter fields obtained during commissioning SkyMapper survey. data consists medium-resolution (R ~ 2,000) spectroscopy 70,000 thick disk and halo stars spanning footprint 4,900 square degrees. We plan...