A5005848430- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Molecular Spectroscopy and Structure
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Space Science and Extraterrestrial Life
- Galaxies: Formation, Evolution, Phenomena
- Scientific Research and Discoveries
- Planetary Science and Exploration
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Adaptive optics and wavefront sensing
- Atomic and Molecular Physics
- Interdisciplinary Research and Collaboration
- Particle Accelerators and Free-Electron Lasers
- Advanced optical system design
- Advanced Combustion Engine Technologies
- Nuclear Issues and Defense
- E-Learning and Knowledge Management
- Photocathodes and Microchannel Plates
- Phase Equilibria and Thermodynamics
University of Arizona
2016-2025
NASA Exoplanet Science Institute
2019-2022
Ames Research Center
2022
University of Cambridge
2016
Stony Brook University
2005
State University of New York
2005
Association of Universities For Research In Astronomy
2005
Cerro Tololo Inter-American Observatory
2005
U.S. National Science Foundation
2005
We present the discovery of seven quasars at z > 5.7, selected from ∼2000 deg2 multicolor imaging data Sloan Digital Sky Survey. The new have redshifts 5.79 to 6.13. Five are as part a complete flux-limited sample in SDSS northern Galactic cap; two larger photometric errors and not sample. One quasars, J1335+3533 (z = 5.93), exhibits no emission lines; 3 σ limit on rest-frame equivalent width Lyα+N V line is 5 Å. It highest redshift lineless quasar known could be gravitational lensed galaxy,...
(abbreviated) We report detection with the Spitzer Space Telescope of cool dust surrounding solar type stars. The observations were performed as part Legacy Science Program, ``Formation and Evolution Planetary Systems'' (FEPS). From overall FEPS sample (Meyer et al. 2006) 328 stars having ages ~0.003-3 Gyr we have selected sources 70 um flux densities indicating excess in their spectral energy distributions above expected photospheric emission........ .....The rising towards - perhaps beyond...
We present Spitzer photometric (IRAC and MIPS) spectroscopic (IRS low resolution) observations for 314 stars in the Formation Evolution of Planetary Systems Legacy program. These data are used to investigate properties evolution circumstellar dust around solar-type spanning ages from approximately 3 Myr–3 Gyr. identify 46 sources that exhibit excess infrared emission above stellar photosphere at 24 μm, 21 with excesses 70 μm. Five an have characteristics optically thick primordial disks,...
We present an analysis of spectrosopic and astrometric data from APOGEE-2 Gaia DR2 to identify structures towards the Orion Complex. By applying a hierarchical clustering algorithm 6-dimensional stellar data, we spatially and/or kinematically distinct groups young objects with ages ranging 1 12 Myr. also investigate star forming history within Complex, peculiar sub-clusters. With this method reconstruct older populations in regions that are presently largely devoid molecular gas, such as C...
We identify a sample of 74 high-redshift quasars (z > 3) with weak emission lines from the Fifth Data Release Sloan Digital Sky Survey and present infrared, optical, radio observations subsample four objects at z 4. These emission-line (WLQs) constitute prominent tail Lyα + N v equivalent width distribution, we compare them to more typical properties low-redshift active galactic nuclei weak/absent lines, namely BL Lac objects. find that WLQs exhibit hot (T ∼ 1000 K) thermal dust have...
Multiplicity is a fundamental property that set early during stellar lifetimes, and it stringent probe of the physics star formation. The distribution close companions around young stars still poorly constrained by observations. We present an analysis multiplicity derived from APOGEE-2 spectra obtained in targeted observations nearby star-forming regions. This largest homogeneously observed sample high-resolution stars. developed autonomous method to identify double lined spectroscopic...
We investigate the young stellar objects (YSOs) in Lynds~1641 (L1641) cloud using multi-wavelength data including Spitzer, WISE, 2MASS, and XMM covering ~1390 YSOs across a range of evolutionary stages. In addition, we targeted sub-sample for optical spectroscopy. use this data, along with archival photometric to derive spectral types, extinction values, masses, ages, as well accretion rates. obtain disk fraction ~50% L1641. The frequency is almost constant function mass slight peak at...
We present the results of SDSS APOGEE INfrared Spectroscopy Young Nebulous Clusters program (IN-SYNC) survey Orion A molecular cloud. This obtained high resolution near infrared (NIR) spectroscopy about 2700 young pre-main sequence stars throughout region, acquired across five distinct fields spanning 6deg field view (FOV). With these spectra, we have measured accurate stellar parameters (T_eff, log g, v sin i) and extinctions, placed sources in Hertzsprung-Russel Diagram (HRD). also...
We present the discovery of an unusual spatially resolved circumstellar structure associated with ≈90 Myr, nearby, G dwarf star HD 61005. Observations from FEPS Spitzer Legacy Science survey reveal thermal emission in excess expected stellar photospheric levels. Follow-up 0.1'' resolution HST NICMOS coronagraphic images scattered starlight ≤7'' (~240 AU) occulted (1.1 μm flux density =18 ± 3.3 mJy; and 0.77% 0.16% starlight). The extremely high near-IR scattering fraction IR luminosity f =...
Star clusters are superb astrophysical laboratories containing cospatial and coeval samples of stars with similar chemical composition. We have initiated the Sejong Open cluster Survey (SOS) - a project dedicated to providing homogeneous photometry large number open in SAAO Johnson-Cousins' $UBVI$ system. To achieve our main goal, we paid much attention observation standard order reproduce Many targets relatively small, sparse that escaped previous observations. As considered building blocks...
Abstract We train a convolutional neural network, APOGEE Net, to predict T eff , <?CDATA $\mathrm{log}g$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> and, for some stars, [Fe/H], based on the spectra. This is first pipeline adapted these data that capable of estimating parameters in self-consistent manner not only low-mass (such as main-sequence dwarfs, pre-main-sequence and red giants), but also high-mass...
Context. The Orion Molecular Cloud complex, one of the nearest (D = 406 pc) and most extensively studied massive star-forming regions, is ideal for constraining physics stellar feedback, but its ~12 deg diameter on sky requires a dedicated approach to mapping ionized gas structures within around nebula. Aims. Sloan Digital Sky Survey (SDSS-V) Local Volume Mapper (LVM) new optical integral field unit (IFU) that will map Milky Way Group galaxies, covering 4300 2 with LVM Instrument (LMV-I)....
We report the discovery of a debris system associated with ~30 Myr old G3/5V star HD 12039 using Spitzer Space Telescope observations from 3.6-160 μm. An observed infrared excess (LIR/L* = 1 × 10-4) above expected photosphere for λ ≳ 14 μm is fit by thermally emitting material color temperature T ~ 110 K, warmer than majority disks identified to date around Sun-like stars. The object not detected at 70 3 σ upper limit 6 times photospheric flux. spectrum can be explained warm, optically thin...
We present the science database produced by Formation and Evolution of Planetary Systems (FEPS) Spitzer Legacy program. Data reduction validation procedures for IRAC, MIPS, IRS instruments are described in detail. also derive stellar properties FEPS sample from available broad-band photometry spectral types, an algorithm to normalize Kurucz synthetic spectra optical near-infrared photometry. The final data products include IRAC MIPS each star calibrated spectra.
Using data from the Spitzer Space Telescope Legacy Science Program ``Formation and Evolution of Planetary Systems'' (FEPS), we have searched for debris disks around 9 FGK stars (2-10 Gyr), known radial velocity (RV) studies to one or more massive planets. Only sources, HD 38529, has excess emission above stellar photosphere; at 70 micron signal-to-noise ratio in is 4.7 while wavelengths < 30 there no evidence excess. The remaining sources show excesses any wavelengths. Applying survival...
We present a deep Spitzer/IRAC survey of the OB association IC 1795 carried out to investigate evolution protoplanetary disks in regions massive star formation. Combining data with Chandra/ACIS observations, we find 289 cluster members. An additional 340 sources an infrared excess, but without X-ray counterpart, are classified as member candidates. Both surveys complete down stellar masses about 1 Msun. pre-main sequence isochrones computed for first time colors. The age cluster, determined...
ABSTRACT One of the key questions in field star formation is role stellar feedback on subsequent process. The W3 giant molecular cloud complex at western border W4 super bubble thought to be influenced by massive stars W4. This paper presents a study activity within AFGL 333, ∼10 4 M ⊙ W3, using deep JHK s photometry obtained from NOAO Extremely Wide Field Infrared Imager combined with Spitzer IRAC and MIPS photometry. Based infrared excess, we identify 812 candidate young objects (YSOs)...
We present the discovery of seven new proplyds (i.e. sources surrounded by cometary Halpha emission characteristic offset ionization fronts) in NGC 1977, located about 30' north Orion Nebula Cluster at a distance ~400 pc. Each these are situated projected distances 0.04-0.27 pc from B1V star 42 Orionis (c Ori), which is main source UV photons region. In all cases fronts clearly pointing toward common ionizing source, Ori, and 6 7 show tails away it. These first to be found around B star,...
A recent survey of the inner $0.35\times0.35$pc NGC 2024 star forming region revealed two distinct millimetre continuum disc populations that appear to be spatially segregated by boundary a dense cloud. The eastern (and more embedded) population is $\sim0.2-0.5$Myr old, with an ALMA mm detection rate about $45\,$per cent. However this drops only $\sim15$per cent in 1Myr western population. When presenting result, van Terwisga et al. (2020) suggested main UV sources, IRS 1 (a B0.5V region)...
Abstract We present a study of the Trapezium cluster in Orion. analyze flux-calibrated Very Large Telescope/Multi-Unit Spectroscopic Explorer spectra 361 stars to simultaneously measure spectral types, reddening, and optical veiling due accretion. find that extinction law from Cardelli et al. with total-to-selective value R V = 5.5 is more suitable for this cluster. For 68% sample new types are consistent literature within two subclasses but, as expected, we derive systematically later than...
HL Tau is one of the most well-studied Class I young stellar objects, including frequent observations at near- and mid-infrared, (sub-) millimeter, X-ray wavelengths. We present results an variability monitoring campaign with XMM-Newton in 2020 gratings spectroscopy from Chandra/HETGS 2018. find that spectrum consistently hot (with characteristic plasma temperatures $T \gtrsim 30$ MK) over 31 epochs spanning 20 years, which consistent temperature YSOs. The high-resolution HETG indicates...
Abstract HL Tau is one of the most well-studied Class I young stellar objects (YSOs), including frequent observations at near- and mid-infrared, (sub)millimeter, X-ray wavelengths. We present results an variability monitoring campaign with XMM-Newton in 2020 grating spectroscopy from Chandra/HETGS 2018. find that spectrum consistently hot (with characteristic plasma temperatures T ≳ 30 MK) over 31 epochs spanning 20 yr, which consistent temperature YSOs. The high-resolution HETG indicates...
Abstract UV radiation from OB stars can drive ‘external’ photoevaporative winds discs in clusters, that have been shown to be important for disc evolution and planet formation. However, cluster dynamics complicate the interpretation of this process. A significant fraction are runaways, propagating at high velocity which might dominate over wider setting time variation field part cluster. We explore impact a runaway star on observational may have. find exposed even short periods strong...
We present the discovery of debris systems around three Sun-like stars based on observations performed with Spitzer Space Telescope as part a Legacy Science Program, "The Formation and Evolution Planetary Systems" (FEPS). also confirm presence two other stars. All exhibit infrared emission in excess expected photospheres 70 μm band but are consistent photospheric at ≤33 μm. This restricts maximum temperature equilibrium stellar radiation to T < K. find that these sources relatively old FEPS...
The kinematics and dynamics of young stellar populations enable us to test theories star formation. With this aim, we continue our analysis the SDSS-III/APOGEE IN-SYNC survey, a high resolution near infrared spectroscopic survey clusters. We focus on Orion A star-forming region, for which obtained spectra $\sim2700$ stars. In Paper IV used these data study population. Here kinematic properties through radial velocities ($v_r$). population remains kinematically associated with molecular gas,...