A5049898816- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Material Science and Thermodynamics
- Scientific Research and Discoveries
- Spacecraft and Cryogenic Technologies
- Adaptive optics and wavefront sensing
- Atmospheric Ozone and Climate
- Crystal Structures and Properties
- X-ray Diffraction in Crystallography
- Geochemistry and Geologic Mapping
- Impact of Light on Environment and Health
- Spectroscopy and Laser Applications
- Astrophysical Phenomena and Observations
- Historical Geography and Cartography
- Intraocular Surgery and Lenses
- Ophthalmology and Visual Impairment Studies
- SAS software applications and methods
- Space Exploration and Technology
- Molecular Spectroscopy and Structure
Yale University
2008-2024
Cerro Tololo Inter-American Observatory
1995
Universities Space Research Association
1992
Mount Wilson Observatory
1980
view Abstract Citations (1732) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Composition of halo clusters and the formation galactic halo. Searle, L. ; Zinn, R. A method abundance determination based on reddening-independent properties low-resolution spectral scans is described applied to 177 red giants in 19 globular clusters, most which are at galactocentric distances excess 8 kpc. The general halo-cluster system inferred from results...
view Abstract Citations (1333) References (43) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The globular cluster system of the Galaxy. III. Measurements radial velocity and metallicity for 60 clusters a compilation metallicities 121 clusters. Zinn, R. ; West, M. J. Spectrograms (121 A mm `)have been obtained galactic three in Small Magellanic Cloud. velocities measured from these spectrograms by cross-correlation technique have an accuracy +20 km are good...
view Abstract Citations (1120) References (88) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Globular Cluster System of the Galaxy. IV. Halo and Disk Subsystems Zinn, R. spatial distributions, kinematics, metallicities 121 globular clusters are examined for evidence distinct subpopulations in cluster system. Clusters more metal-poor than (Fe/H) = -0.8 constitute familiar halo population, while metal-rich have properties a disk There is shallow but...
view Abstract Citations (445) References (151) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Horizontal-Branch Stars in Globular Clusters. II. Second Parameter Phenomenon Lee, Young-Wook ; Demarque, Pierre Zinn, Robert Using synthetic horizontal-branch models, we have investigated the origin of systematic variation (HB) morphology with galactocentric distance (RG) among globular clusters. variations He abundance, CNO and core mass required separately to...
view Abstract Citations (450) References (106) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Horizontal-Branch Stars in Globular Clusters. I. Period-Shift Effect, the Luminosity of Horizontal Branch, and Age-Metallicity Relation Lee, Young-Wook ; Demarque, Pierre Zinn, Robert Synthetic models horizontal branches globular clusters are constructed from a grid standard branch evolutionary tracks. used to study period shifts at constant T(eff) between RR...
view Abstract Citations (358) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Integrated-Light Spectroscopy of Globular Clusters at the Infrared CA II Lines Armandroff, Taft E. ; Zinn, Robert Integrated-light spectroscopy has been obtained for 27 globular clusters Ca IR triplet. Line strengths and radial velocities have measured from spectra. For well-studied in sample, strength lines is very well correlated with previous metallicity...
We have measured the periods and light curves of 148 RR Lyrae variables from V = 13.5 to 19.7 first 100 deg2 Quasar Equatorial Survey Team survey. Approximately 55% these stars belong clump detected earlier by Sloan Digital Sky Survey. According our measurements, this feature has ~10 times background density halo stars, spans at least 375 35 in α δ (≥30 ≥3 kpc), lies ~50 kpc Sun, a depth along line sight ~5 (1 σ). These properties are consistent with recent models that suggest it is tidal...
The first catalog of the RR Lyrae stars (RRLSs) in Galactic halo by Quasar Equatorial Survey Team (QUEST) has been searched for significant overdensities that may be debris from disrupted dwarf galaxies or globular clusters. These RRLSs are contained a band ∼23 wide declination spans ∼165° right ascension and lie ∼4 to ∼60 kpc Sun. Away major overdensities, distribution these is adequately fitted smooth model, which flattening decreases with increasing galactocentric distance (as reported...
Eighteen RR Lyrae variables (RRLs) that lie in the "124 clump" identified by Quasar Equatorial Survey Team (QUEST) have been observed spectroscopically to measure their radial velocities and metal abundances. Ten blue horizontal branch (BHB) stars Sloan Digital Sky (SDSS) were added this sample. Six of nine densest region clump a mean velocity Galactic rest frame (Vgsr) 99.8 σ = 17.3 km s-1, which is slightly smaller than average error measurements. The whole sample contains eight RRLs five...
Ca ii triplet spectroscopy has been used to derive stellar metallicities for individual stars in four Large Magellanic Cloud fields situated at galactocentric distances of 3°, 5°, 6°, and 8° the north bar. Observed metallicity distributions show a well-defined peak, with tail toward low metallicities. The mean remains constant until 6° ([Fe/H] ∼−0.5 dex), while outermost field, 8°, is substantially lower than rest disk ∼−0.8 dex). combination deep CCD photometry allowed us break RGB...
view Abstract Citations (441) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The globular cluster system of the galaxy. I. metal abundances and reddenings 79 clusters from integrated light measurements. Zinn, R. Photoelectric photometry integrand in selected filter passbands has been used to derive estimates their interstellar (i.e., [Fe/H]). uncertainties these average ±0.03 E(B - V) ±0.10 [Fe/H], which are not much larger than derived best...
With the 1 m Schmidt telescope of Llano del Hato Observatory and QUEST CCD camera, 380 deg2 sky have been surveyed for RR Lyrae variables in a band 23 wide declination (centered at δ = -1°) covering right ascensions from 41 to 61 80 170. The bright limit (due saturation) faint are V ∼ 13.5 ∼19.7, respectively, which correspond ∼4 ∼60 kpc Sun. We present catalog positions, amplitudes, mean magnitudes, periods, light curves 498 that identified this region sky. majority these stars (86%) new...
Context.Recently, Carraro (2005) drew attention to the remarkable star cluster Whiting 1 by showing that it lies about 40 kpc from Sun and is therefore unquestionably a member of Galactic halo ( deg). Its Color Magnitude Diagram (CMD) indicated very young (~5 Gyr) for globular cluster. It likely originated in dwarf galaxy has since been disrupted Milky Way.
view Abstract Citations (117) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The masses of the anomalous cepheids in Draco system. Zinn, R. ; Searle, L. From spectrophotometric observations, we have determined mean effective temperatures seven variable stars dwarf spheroidal galaxy. Five these variables are Cepheids that do not obey period-luminosity relations for either classical or found globular clusters. other two RR Lyrae variables. and...
We present global metallicity properties, distribution functions (MDFs), and radial profiles for the six most luminous M31 dwarf galaxy satellites: M32, NGC 205, 185, 147, Andromeda VII, II. The results presented are first spectroscopic MDFs systems surrounding a host other than Milky Way (MW). Our sample consists of individual measurements 1243 red giant branch member stars spread across these systems. determine metallicities based on strength Ca ii triplet lines using empirical calibration...
Using observations from the Hubble Space Telescope archive, color-magnitude diagrams (CMDs) have been constructed for globular cluster 4 in Fornax dwarf spheroidal galaxy and its surrounding field. These extend below main-sequence turnoffs yielded measurements of ages populations. The most prominent features CMD field population are a heavily populated red clump horizontal-branch (HB) stars, broad giant branch (RGB), main sequence that spans large range luminosity. In this CMD, there very...
From observations with the Hubble Space Telescope, color-magnitude diagrams (CMDs) have been constructed for four most metal-poor globular clusters in Fornax dSph galaxy. These confirm that cluster 1 has a redder horizontal-branch (HB) morphology than other three despite its similarity metallicity (the second parameter effect). The near coincidence of fiducial lines CMDs indicates ages are identical to within Gyr. Since larger range is predicted if age parameter, we conclude either...
From observations of almost 500 red giant branch stars in 29 Galactic open and globular clusters, we have investigated the behavior infrared Ca II triplet (8498, 8542, 8662 Å) age range 13 Gyr ≤ 0.25 metallicity -2.2 [Fe/H] +0.47. These are widest ranges ages metallicities which lines has been a homogeneous way. We report first empirical study variation lines' strength, for given metallicities, with respect to luminosity. find that sequence defined by each cluster luminosity-ΣCa plane is not...
view Abstract Citations (206) References (74) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The globular cluster system of the Galaxy. II. spatial and metallicity distributions, second parameter phenomenon, formation system. Zinn, R. Metal abundance measurements that were made for 84 clusters are used to describe There is a metal gradient between within 9 kpc galactic center more distant than kpc. with distance from plane among center. strength phenomenon...
A search for RR Lyrae stars (RRLSs) in ∼840 deg2 of the sky right ascension 150°–210° and declination −10° to + 10° yielded 1013 type ab 359 c RRLS. This sample is used study density profile Galactic halo, halo substructures, Oosterhoff over distances (d☉) from ∼5 ∼80 kpc. The flattened toward plane, its steepens slope at galactocentric greater than ∼25 RRLS stellar stream Sagittarius dwarf spheroidal (dSph) galaxy match well model Law & Majewski that were stripped 1.3–3.2 Gyr ago, but not...
A grid of synthetic horizontal-branch (SHB) models based on (HB) evolutionary tracks with improved physics has been constructed to reconsider the theoretical calibration dependence Mv(RR) metallicity in globular clusters and slope mean ⟨MV(RR)⟩-[Fe/H] relation. The SHB confirm Lee's earlier finding that relation is itself a function range considered that, addition, for given [Fe/H] RR Lyrae luminosities depend HB morphology. This due fact stars pass through instability strip at different...
We use a complete sample of RR Lyrae stars discovered by the Quasar Equatorial Survey Team survey using light curves to design selection criteria based on Sloan Digital Sky (SDSS) colors. Thanks sensitivity u - g color surface gravity and r effective temperature small photometric errors (∼0.02 mag) delivered SDSS, can be efficiently robustly recognized even with single-epoch data. In 100% color-selected sample, efficiency (the fraction in candidate sample) is 6%, and, adjusting cuts, it...
To explore the complex halo substructure that has been reported in direction of Virgo constellation, radial velocities and metallicities have measured for 82 RR Lyrae stars (RRLS) were identified by QUEST survey. These are distributed over 90 square degrees sky, lie from 4 to 23 kpc Sun. Using an algorithm finding groups phase space modeling smooth component region, we 5 most significant RRLS groups, some which previously known or suspected. We examined SEKBO Catalina catalog (with available...
Near-infrared spectra were obtained for 117 red giants in the Fornax dwarf spheroidal galaxy with FORS1 spectrograph on VLT, order to study metallicity distribution of stars and lift age-metallicity degeneracy giant branch (RGB) color-magnitude diagram (CMD). Metallicities are derived from equivalent widths infrared calcium triplet lines at 8498, 8542, 8662 Å, calibrated data globular clusters, open cluster M67, LMC. For a substantial portion sample, strength is unexpectedly high, clearly...
Sixteen RR Lyrae variables from the QUEST survey that lie in leading arm of tidal stream Sagittarius dSph galaxy have been observed spectroscopically to measure their radial velocities and metal abundances. The systemic 14 stars, which were determined by fitting a standard velocity curve individual measurements, sharply peaked distribution with mean 33 km s-1 deviation only 25 s-1. [Fe/H] these stars has -1.76 0.22. These measurements are good agreement previous ones smaller samples stars....