Publications (41)
DES Science Portal: Computing Photometric Redshifts
Julia Gschwend, Aurelio Carnero Rosell, Ricardo Ogando +68
A significant challenge facing photometric surveys for cosmological purposes is the need to produce reliable redshift estimates. The estimation of photometric redshifts (photo-zs)…
Metal-poor stars observed with the automated planet finder telescope. I. Discovery of five carbon-enhanced metal-poor stars from LAMOST
Mohammad K. Mardini, Haining Li, Vinicius M. Placco +6
We report on the discovery of five carbon-enhanced metal-poor (CEMP) stars in the metallicity range of [Fe/H] . These stars were selected from the LAMOST DR3 low-res…
The Dark Energy Survey Supernova Program results: Type Ia Supernova brightness correlates with host galaxy dust
Cole Meldorf, Antonella Palmese, Dillon Brout +68
Cosmological analyses with type Ia supernovae (SNe Ia) often assume a single empirical relation between color and luminosity () and do not account for varying host-galaxy dust…
OzDES Reverberation Mapping Program: Lag recovery reliability for 6-year CIV analysis
Andrew Penton, Umang Malik, Tamara Davis +66
We present the statistical methods that have been developed to analyse the OzDES reverberation mapping sample. To perform this statistical analysis we have created a suite of custo…
The Case for the Dual Halo of the Milky Way
Timothy C. Beers, Daniela Carollo, Zeljko Ivezic +11
Carollo et al. have recently resolved the stellar population of the Milky Way halo into at least two distinct components, an inner halo and an outer halo. This result has been crit…
High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE: I. Atmospheric Parameters and Chemical Compositions
Wako Aoki, Timothy C. Beers, Young Sun Lee +8
Chemical compositions are determined based on high-resolution spectroscopy for 137 candidate extremely metal-poor (EMP) stars selected from the Sloan Digital Sky Survey (SDSS) and…
Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey
Yu-Ching Chen, Xin Liu, Wei-Ting Liao +62
Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confir…
Bright Metal-Poor Stars from the Hamburg/ESO Survey. II. A Chemodynamical Analysis
Timothy C. Beers, Vinicius M. Placco, Daniela Carollo +6
We obtain estimates of stellar atmospheric parameters for a previously published sample of 1777 relatively bright (9 < B < 14) metal-poor candidates from the Hamburg/ESO Survey. Th…
Searches for the Most Metal-Poor Candidates from SDSS and SEGUE
Timothy C. Beers, Daniela Carollo
We report on efforts to identify large samples of very and extremely metal-poor stars based on medium-resolution spectroscopy and ugriz photometry obtained during the course of the…
Constraints on the Galactic Inner Halo Assembly History from the Age Gradient of Blue Horizontal-branch Stars
Devin D. Whitten, Timothy C. Beers, Vinicius M. Placco +6
We present an analysis of the relative age distribution of the Milky Way halo, based on samples of blue horizontal-branch (BHB) stars obtained from the Panoramic Survey Telescope a…
Observational Constraints on First-Star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-no Stars
Jinmi Yoon, Timothy C. Beers, Vinicius M. Placco +6
We investigate anew the distribution of absolute carbon abundance, (C) (C), for carbon-enhanced metal-poor (CEMP) stars in the halo of the Milky Way, based on high-r…
CN Anomalies in the Halo System and the Origin of Globular Clusters in the Milky Way
Daniela Carollo, Sarah Martell, Timothy Beers +1
We explore the kinematics and orbital properties of a sample of red giants in the halo system of the Milky Way that are thought to have formed in globular clusters, based on their…
Dark Energy Survey Identification of A Low-Mass Active Galactic Nucleus at Redshift 0.823 from Optical Variability
Hengxiao Guo, Colin J. Burke, Xin Liu +56
We report the identification of a low-mass AGN, DES J02180430, in a redshift galaxy in the Dark Energy Survey (DES) Supernova field. We select DES J02180430 as an…
Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy
Timothy C. Beers, Deokkeun An, Jennifer A. Johnson +7
We describe the methodology required for estimation of photometric estimates of metallicity based on the SDSS gri passbands, which can be used to probe the properties of main-seque…
Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
Wako Aoki, Timothy C. Beers, Thirupathi Sivarani +6
The chemical compositions of seven Carbon-Enhanced Metal-Poor (CEMP) turn-off stars are determined from high-resolution spectroscopy. Five of them are selected from the SDSS/SEGUE…
The Origin of the Milky Way's Halo Age Distribution
Daniela Carollo, Patricia B. Tissera, Timothy C. Beers +4
We present an analysis of the radial age gradients for the stellar halos of five Milky Way mass-sized systems simulated as part of the Aquarius Project. The halos show a diversity…
Chemical Cartography. I. A Carbonicity Map of the Galactic Halo
Young Sun Lee, Timothy C. Beers, Young Kwang Kim +5
We present the first map of carbonicity, [C/Fe], for the halo system of the Milky Way, based on a sample of over 100,000 main-sequence turnoff stars with available spectroscopy fro…
Structure and Kinematics of the Stellar Halos and Thick Disks of the Milky Way Based on Calibration Stars from SDSS DR7
Daniela Carollo, Timothy C. Beers, Masashi Chiba +6
The structure and kinematics of the recognized stellar components of the Milky Way are explored, based on well-determined atmospheric parameters and kinematic quantities for 32360…
Evidence for the Third Stellar Population in the Milky Way's Disk
Daniela Carollo, Masashi Chiba, Miho Ishigaki +6
The Milky Way is a unique laboratory, where stellar properties can be measured and analyzed in detail. In particular, stars in the older populations encode information on the mecha…
Carbon-enhanced Metal-poor Stars in SDSS/SEGUE. I. Carbon Abundance Estimation and Frequency of CEMP Stars
Young Sun Lee, Timothy C. Beers, Thomas Masseron +8
We describe a method for the determination of stellar [C/Fe] abundance ratios using low-resolution (R = 2000) stellar spectra from the SDSS and SEGUE. By means of a star-by-star co…
The Fractions of Inner- and Outer-Halo Stars in the Local Volume
Deokkeun An, Timothy C. Beers, Rafael M. Santucci +4
We obtain a new determination of the metallicity distribution function (MDF) of stars within - kpc of the Sun, based on recently improved co-adds of photometry f…
The Assembly of the Halo System of the Milky Way as Revealed by SDSS/SEGUE -- The CEMP Star Connection
Timothy C. Beers, Daniela Carollo
In recent years, massive new spectroscopic data sets, such as the over half million stellar spectra obtained during the course of SDSS (in particular its sub-survey SEGUE), have pr…
The Stellar Metallicity Distribution Function of the Galactic Halo from SDSS Photometry
Deokkeun An, Timothy C. Beers, Jennifer A. Johnson +6
We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of severa…
The GALAH Survey: Stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere and metallicity
Alice C. Quillen, Gayandhi De Silva, Sanjib Sharma +30
Using GALAH survey data of nearby stars, we look at how structure in the planar (u,v) velocity distribution depends on metallicity and on viewing direction within the Galaxy. In ne…
The Dichotomy of the Halo of the Milky Way
Daniela Carollo, Timothy C. Beers
We summarize evidence that the halo of the Milky Way comprises two different, and broadly overlapping, stellar components. The two structures exhibit different chemical composition…
Extreme Enhancements of r-process Elements in the Cool Metal-Poor Main-Sequence Star SDSS J2357-0052
Wako Aoki, Timothy C. Beer, Satoshi Honda +1
We report the discovery of a cool metal-poor, main-sequence star exhibiting large excesses of r-process elements. This star is one of two newly discovered cool subdwarfs (effective…
Population Studies. XIII. A New Analysis of the Bidelman-MacConnell "Weak-Metal" Stars - Confirmation of Metal-Poor Stars in the Thick Disk of the Galaxy
Timothy C. Beers, John E. Norris, Vinicius M. Placco +4
A new set of very high signal-to-noise (S/N > 100/1), medium-resolution (R~3000) optical spectra have been obtained for 302 of the candidate "weak-metal" stars selected by Bidelman…
Possible Evidence for Metal Accretion onto the Surfaces of Metal-Poor Main-Sequence Stars
Kohei Hattori, Yuzuru Yoshii, Timothy C. Beers +2
The entire evolution of the Milky Way, including its mass-assembly and star-formation history, is imprinted onto the chemo-dynamical distribution function of its member stars, f(x,…
The nature of the Milky Way's stellar halo revealed by the three integrals of motion
Daniela Carollo, Masashi Chiba
We developed a new selection method of halo stars in the phase-space distribution defined by the three integrals of motion in an axisymmetric Galactic potential, (, , …
A Multiply-Imaged z 6.3 Lyman Alpha Emitter candidate behind Abell 2261
Claes-Erik Rydberg, Adi Zitrin, Erik Zackrisson +6
While the Lyman- () emission line serves as an important tool in the study of galaxies at , finding Ly emitters (LAE) at significantly higher re…
Understanding the early stages of galaxy formation using very metal-poor stars from the Hamburg/ESO survey
Daniela Carollo, Norbert Christlieb, Patricia B. Tissera +1
We explore the chemo-dynamical properties of a sample of very metal-poor (VMP) stars selected from the Hamburg/ESO survey, matched with Gaia EDR3, in the phase-space identified by…
The central spheroids of Milky Way mass-sized galaxies
Patricia B. Tissera, Rubens E. G. Machado, Daniela Carollo +4
We study the properties of the central spheroids located within 10 kpc of the centre of mass of Milky Way mass-sized galaxies simulated in a cosmological context. The simulated cen…
First Light Results from the Hermes Spectrograph at the AAT
Andrew Sheinis, Borja Anguiano, Martin Asplund +60
The High Efficiency and Resolution Multi Element Spectrograph, HERMES, is a facility-class optical spectrograph for the Anglo-Australian Telescope (AAT). It is designed primarily f…
Carbon-Enhanced Metal-Poor Stars: CEMP-s and CEMP-no Sub-Classes in the Halo System of the Milky Way
Daniela Carollo, Ken Freeman, Timothy Beers +3
We explore the kinematics and orbital properties of a sample of 323 very metal-poor stars in the halo system of the Milky Way, selected from the high-resolution spectroscopic follo…
Unlocking the physics of dwarf galaxies in the 2040s: The case for a next-generation wide-field spectroscopic facility with fibres and IFUs
Crescenzo Tortora, Daniela Carollo, Leslie Hunt +25
Dwarf galaxies () are the most numerous galaxies in the Universe and critical probes of dark matter, baryonic feedback, and galaxy formation. D…
The GALAH survey: a catalogue of carbon-enhanced stars and CEMP candidates
Klemen Äotar, Tomaž Zwitter, Janez Kos +19
Swan bands - characteristic molecular absorption features of the C molecule - are a spectroscopic signature of carbon-enhanced stars. They can also be used to identify carbon-e…
The Frequency of Field Blue-Straggler Stars in the Thick Disk and Halo System of the Galaxy
Rafael M. Santucci, Vinicius M. Placco, Silvia Rossi +5
We present an analysis of a new, large sample of field blue-straggler stars (BSSs) in the thick disk and halo system of the Galaxy, based on stellar spectra obtained during the Slo…
Lithium Abundances of Extremely Metal-Poor Turn-off Stars
Wako Aoki, Paul S. Barklem, Timothy C. Beers +5
We have determined Li abundances for eleven metal-poor turn-off stars, among which eight have [Fe/H]<-3, based on LTE analyses of high-resolution spectra obtained with the HDS on t…
The GALAH Survey: Observational Overview and Gaia DR1 companion
Sarah Martell, Sanjib Sharma, Sven Buder +30
The Galactic Archaeology with HERMES (GALAH) Survey is a massive observational project to trace the Milky Way's history of star formation, chemical enrichment, stellar migration an…
Very Metal-Poor Outer-Halo Stars with Round Orbits
Kohei Hattori, Yuzuru Yoshii, Timothy C. Beers +2
The orbital motions of halo stars in the Milky Way reflect the orbital motions of the progenitor systems in which they formed, making it possible to trace the mass-assembly history…
Lithium in NGC 2243 and NGC 104
Misa Aoki, Francesca Primas, Luca Pasquini +3
Our aim was to determine the initial Li content of two clusters of similar metallicity but very different ages, the old open cluster NGC 2243 and the metal-rich globular cluster NG…