A5064585353- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Seismic Waves and Analysis
- Calibration and Measurement Techniques
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Image and Object Detection Techniques
- Medical Imaging Techniques and Applications
- CCD and CMOS Imaging Sensors
- Sesquiterpenes and Asteraceae Studies
- Dynamics and Control of Mechanical Systems
- Archaeology and Natural History
- Image Processing and 3D Reconstruction
- Seismic Imaging and Inversion Techniques
- GNSS positioning and interference
- Optical measurement and interference techniques
Saint Martin's University
2017-2024
Cerro Tololo Inter-American Observatory
2010-2019
Leibniz Institute for Astrophysics Potsdam
2013-2018
University of Potsdam
2015
Dartmouth College
2007-2010
Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is fifth data release from a magnitude-limited (9< I < 12) survey stars randomly selected in southern hemisphere. The RAVE medium-resolution spectra ($R\sim7500$) covering Ca-triplet region (8410-8795\AA) span complete time frame start observations 2003 to their completion 2013. velocities 520,781 457,588 unique are presented, which 255,922 stellar have parallaxes and proper motions Tycho-Gaia astrometric solution (TGAS) Gaia DR1....
Bulges are commonly believed to form in the dynamical violence of galaxy collisions and mergers. Here, we model stellar kinematics Bulge Radial Velocity Assay (BRAVA) find no sign that Milky Way contains a classical bulge formed by scrambling pre-existing disks stars major Rather, appears be bar seen somewhat end-on, as hinted from its asymmetric boxy shape. We construct simple but realistic N-body Galaxy self-consistently develops bar. The immediately buckles thickens vertical direction. As...
We present new radial velocity measurements from the Bulge Radial Velocity Assay, a large-scale spectroscopic survey of M-type giants in Galactic bulge/bar region. The sample ∼4500 velocities, mostly region −10° < l +10° and b ≈ −6°, more than doubles existent published data set. Our extend our rotation curve dispersion profile to +20°, which is ∼2.8 kpc center. confirm cylindrical observed at −6° −8° are an excellent fit Shen et al. N-body bar model. measure strength TiOε molecular band as...
We present radial velocities and chemical abundances of O, Na, Mg, Al, Si, Ca, Cr, Fe, Co, Ni, Cu for a sample 156 red giant branch stars in two Galactic bulge fields centered near (l, b) = (+5.25,−3.02) (0,−12). The field also includes observations the globular cluster NGC 6553. results are based on high-resolution (R ∼ 20,000), high signal-to-noise ration (S/N ≳ 70) FLAMES–GIRAFFE spectra obtained through European Southern Observatory archive. However, we only selected subset original that...
Non-axisymmetries in the Galactic potential (spiral arms and bar) induce kinematic groups such as Hercules stream. Assuming that is caused by effects of Outer Lindblad Resonance bar, we model analytically its properties a function position Galaxy dependence on bar's pattern speed orientation. Using data from RAVE survey find azimuthal velocity structure decreases Galactocentric radius, manner consistent with our analytical model. This allows us to obtain new estimates parameters Milky Way's...
We investigate interstellar extinction curve variations toward $\sim$4 deg$^{2}$ of the inner Milky Way in $VIJK_{s}$ photometry from OGLE-III and $VVV$ surveys, with supporting evidence diffuse bands $F435W,F625W$ photometry. obtain independent measurements $\sim$2,000 sightlines $A_{I}$, $E(V-I)$, $E(I-J)$, $E(J-K_{s})$, median precision accuracy 2%. find that ratios $A_{I}/E(V-I)$, $E(I-J)/E(V-I)$ $E(J-K_{s})/E(V-I)$ are large (exceeding 20%), significant, positively correlated, as...
We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within data from ongoing Survey Magellanic Stellar History conducted with Dark Energy Camera on Blanco 4 m Telescope. The satellite is compact ( ± 11 pc) and faint 0.3), but well realm galaxies. stellar distribution II in color–magnitude diagram well-described by metal-poor () old (13 Gyr) isochrone shows distinct blue horizontal branch, some possible red clump stars, stars that are suggestive stragglers. At...
ABSTRACT We present 947 radial velocities of RR Lyrae variable stars in four fields located toward the Galactic bulge, observed within data from ongoing Bulge Radial Velocity Assay (BRAVA-RR). show that these (RRLs) exhibit hot kinematics and null or negligible rotation are therefore members a separate population bar/pseudobulge currently dominates mass luminosity inner Galaxy. Our RRLs predate structures have metallicities, kinematics, spatial distribution consistent with “classical”...
This compilation is the fourth data release from R-Process Alliance (RPA) search for r-process-enhanced stars and second based on "snapshot" high-resolution (R ∼ 30,000) spectra collected with du Pont 2.5 m Telescope. In this release, we propose a new delineation between r-I r-II stellar classes at , instead of empirically chosen level previously in use, statistical tests complete set RPA released to date. We also statistically justify minimum [Eu/Fe] definition stars, > +0.3. Redefining...
We present the first results of our analyses selected RR Lyrae stars for which data have been obtained by Kepler Mission. As expected, we find a significant fraction RRab to show Blazhko effect, still unexplained phenomenon that manifests itself as periodic amplitude and phase modulations light curve, on time scales typically tens hundreds days. The long span Mission 3.5 yrs, unprecedentedly high precision its provide unique opportunity study stars. Using modulated star observed in roll...
ABSTRACT Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of classical, pressure-supported component within part Milky Way still being debated. It should be most visible at low metallicity, regime that has not been studied in detail. Using metallicity-sensitive narrow-band photometry, Pristine Inner Survey (PIGS) collected large sample metal-poor ($\rm {[Fe/H]}\, \lt -1.0$) stars inner address this open question. We use PIGS trace kinematics as function...
The central kiloparsecs of the Milky Way are known to host an old, spheroidal stellar population, whose spatial and kinematical properties set it apart from boxy/peanut structure that constitutes most mass. nature this whether a small classical bulge, innermost halo or population disk stars with large initial velocity dispersion, remains unclear. This is also promising candidate some oldest in Galaxy. Here we address topic inner spheroid age, using spectroscopic photometric metallicities for...
We present a new set of period–absolute magnitude–metallicity (PMZ) relations for single-mode RR Lyrae stars calibrated the optical G BP , V RP near-infrared I J H and K s passbands. compiled large dataset (over 100 objects) fundamental first-overtone pulsators consisting mean intensity magnitudes, reddenings, pulsation properties, iron abundances, parallaxes measured by Gaia astrometric satellite in its third data release. Our newly PMZ encapsulate most up-to-date ingredients terms both...
Nineteen of the ~40 RR Lyr stars in Kepler field have been identified as candidate non-Blazhko (or unmodulated) stars. In this paper we present results Fourier decomposition time-series photometry these acquired during first 417 days operation (Q0-Q5) telescope. parameters based on ~18400 long-cadence observations per star (and ~150000 short-cadence for FN and AW Dra) are derived. None shows recently discovered `period-doubling' effect seen Blazhko variables; however, KIC 7021124 has found...
We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], [Ca/Fe] for 264 red giant branch (RGB) stars in three Galactic bulge off-axis fields located near (l,b)=(-5.5,-7), (-4,-9), (+8.5,+9). The results are based on equivalent width spectrum synthesis analyses moderate resolution (R~18,000), high signal-to-noise ratio (S/N~75-300) spectra obtained with the Hydra spectrographs Blanco 4m WIYN 3.5m telescopes. targets were selected from blue side to avoid cool...
The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC6656 (M22), with observations spanning a range of twenty-two years. We have also redetermined variability types and periods identified previously by photographic observations, revising number fundamental-mode variables (RR0) to 10 first-overtone (RR1) 16. mean RR0 RR1 are <P>_{RR0}=0.66 \pm 0.02 d <P>_{RR1}=0.33 0.01 d, respectively, supporting an Oosterhoff II classification...
The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform 5000 sq-degree wide field 30 supernova surveys, DES Collaboration built Camera (DECam), 3 square-degree, 570-Megapixel CCD camera that was installed prime focus Blanco 4-meter telescope Cerro Tololo Inter-American...
We use data from the Radial Velocity Experiment (RAVE) and Tycho-Gaia astrometric solution (TGAS) catalogue to compute velocity fields yielded by radial (VR), azimuthal (Vϕ),and vertical (Vz) components of associated Galactocentric velocity. search in particular for variation all three with distance above below disc mid-plane, as well how each component Vz (line-of-sight tangential projections) modifies obtained structure. To study dependence on proper motion distance, we two main samples: a...
We aim to characterize high-velocity (HiVel) stars in the solar vicinity both chemically and kinematically using fourth data release of RAdial Velocity Experiment (RAVE). used a sample 57 HiVel with Galactic rest-frame velocities larger than 275 km s$^{-1}$. With 6D position velocity information, we integrated orbits found that, on average, they reach out 13 kpc from plane have relatively eccentric consistent halo. Using stellar parameters [$\alpha$/Fe] estimates RAVE, metallicity...
Abstract The Large and Small Magellanic Clouds are unique local laboratories for studying the formation evolution of small galaxies in exquisite detail. Survey MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey mapping 480 deg 2 (distributed over ∼2400 square degrees at ∼20% filling factor) to ∼24th mag ugriz . primary goals SMASH identify low surface brightness stellar populations associated with halos tidal debris Clouds, derive spatially resolved...
The orbits, atmospheric parameters, chemical abundances, and ages of individual stars in the Milky Way provide most comprehensive illustration galaxy formation available. Tycho-Gaia Astrometric Solution (TGAS) will deliver astrometric parameters for largest ever sample stars, though its full potential cannot be realized without addition complementary spectroscopy. Among existing spectroscopic surveys, RAdial Velocity Experiment (RAVE) has overlap with TGAS ($\gtrsim$200,000 stars). We...
This paper presents the detailed abundances and r-process classifications of 126 newly identified metal-poor stars as part an ongoing collaboration, R-Process Alliance. The were candidates from RAdial Velocity Experiment (RAVE) followed-up at high spectral resolution (R~31,500) with 3.5~m telescope Apache Point Observatory. atmospheric parameters determined spectroscopically Fe I lines, taking into account <3D> non-LTE corrections using differential respect to a set standards. Of new stars,...
Radial velocities of 2768 fundamental mode RR Lyrae stars (RRLs) toward the Southern Galactic bulge are presented, spanning southern from -8 < l +8 and -3 b <-6. Distances derived pulsation properties RRLs combined with Gaia proper motions to give constraints on orbital 1389 RRLs. The majority (~75%) have orbits consistent these being permanently bound <3.5 kpc Center, similar bar. However, unlike giants, exhibit slower rotation a higher velocity dispersion. dispersion arises almost...
We created new reddening maps and derived extinction laws from visual to near-infrared passbands using improved RR~Lyrae period-absolute magnitude-metallicity relations, thus enabling distance estimates for individual bulge variables. The law is most uniform in RIK RJK the distances based on these colors are determined with an accuracy six four percent, respectively. Using only estimation we inferred Galactic center equal djk = 8.2 +- 0.001(stat) 0.53(sys)pc after geometrical correction....
RR Lyrae stars toward the Galactic bulge are used to investigate whether this old stellar population traces bar. Although bar is known dominate mass in inner Galaxy, there no consensus on star population, which constitutes some of most ancient and thus earliest epochs formation, contributes barred bulge. We create new reddening maps derive extinction laws from visual near-infrared passbands using improved period-absolute magnitude-metallicity relations, enabling distance estimates for...