A5008486123- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Astro and Planetary Science
- Dark Matter and Cosmic Phenomena
- Scientific Research and Discoveries
- Astrophysics and Cosmic Phenomena
- CCD and CMOS Imaging Sensors
- Radio Astronomy Observations and Technology
- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Impact of Light on Environment and Health
- Plant Water Relations and Carbon Dynamics
- Calibration and Measurement Techniques
- Statistical and numerical algorithms
- Pulsars and Gravitational Waves Research
- Space Satellite Systems and Control
- Space Science and Extraterrestrial Life
- Advanced optical system design
Yale University
2015-2024
Campbell Collaboration
2000-2023
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
Whitney Museum of American Art
2013-2014
National Radio Astronomy Observatory
2013
European Southern Observatory
2009
Institut de Planétologie et d'Astrophysique de Grenoble
2009
Observatoire de Paris
2009
Janssen (Switzerland)
2009
We report on our search for microlensing towards the Large Magellanic Cloud (LMC). Analysis of 5.7 years photometry 11.9 million stars in LMC reveals 13 - 17 events. This is significantly more than $\sim$ 2 to 4 events expected from lensing by known stellar populations. The timescales ($\that$) range 34 230 days. estimate optical depth with $2 < \that 400$ days be 1.2 ^{+0.4}_ {-0.3} \ten{-7}$, an additional 20% 30% systematic error. spatial distribution mildly inconsistent LMC/LMC disk...
We present Keck DEIMOS spectroscopy of stars in eight the newly discovered ultra-faint dwarf galaxies around Milky Way. measure velocity dispersions Canes Venatici I, II, Coma Berenices, Hercules, Leo IV, T, Ursa Major and II from velocities 18-214 each galaxy find ranging 3.3 to 7.6 km s-1. The six with absolute magnitudes MV < -4 are highly dark matter dominated, mass-to-light ratios approaching 1000 M☉/L☉,V. For fainter we tentative evidence for tidal disruption. measured dwarfs...
We derive an accurate mass estimator for dispersion-supported stellar systems and demonstrate its validity by analyzing resolved line-of-sight velocity data globular clusters, dwarf galaxies, elliptical galaxies. Specifically, manipulating the spherical Jeans equation we show that dynamical enclosed within 3D deprojected half-light radius r_1/2 can be determined with only mild assumptions about spatial variation of dispersion anisotropy. find M_1/2 = 3 \sigma_los^2 / G ~ 4 R_eff G, where is...
We report the discovery of 47 low surface brightness objects in deep images a 3° × field centered on Coma cluster, obtained with Dragonfly Telephoto Array. The have central μ(g, 0) ranging from 24–26 mag arcsec−2 and effective radii reff = 3''–10'', as measured archival Canada–France–Hawaii Telescope images. From their spatial distribution we infer that most or all are galaxies cluster. This relatively large distance is surprising it implies very large: 1.5–4.6 kpc sizes similar to those L*...
We present a sample of 151 dwarf galaxies (108.5 ≲ M⋆ 109.5 M☉) that exhibit optical spectroscopic signatures accreting massive black holes (BHs), increasing the number known active in this stellar-mass range by more than an order magnitude. Utilizing data from Sloan Digital Sky Survey Data Release 8 and stellar masses NASA-Sloan Atlas, we have systematically searched for BHs ∼25,000 emission-line with comparable to Magellanic Clouds redshifts z < 0.055. Using narrow-line [O iii]/Hβ versus...
We demonstrate that dwarf galaxies (10^7 < M_stellar 10^9 Msun) with no active star formation are extremely rare (<0.06%) in the field. Our sample is based on NASA-Sloan Atlas which a re-analysis of Sloan Digital Sky Survey Data Release 8. examine relative number quenched versus forming galaxies, defining as having Halpha emission (EW_Halpha 2 AA) and strong 4000AA-break. The fraction decreases rapidly increasing distance from massive host, leveling off for distances beyond 1.5 Mpc. define...
We present new constraints on the star formation histories of six ultra-faint dwarf galaxies: Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I. Our analysis employs a combination high-precision photometry obtained with Advanced Camera for Surveys Hubble Space Telescope, medium-resolution spectroscopy DEep Imaging Multi-Object Spectrograph W. M. Keck Observatory, updated Victoria-Regina isochrones tailored to abundance patterns appropriate these galaxies. The...
We present the results of a comprehensive Keck/DEIMOS spectroscopic survey ultra-faint Milky Way satellite galaxy Segue 1. have obtained velocity measurements for 98.2% stars within 67 pc (10 arcmin, or 2.3 half-light radii) center 1 that colors and magnitudes consistent with membership, down to magnitude limit r=21.7. Based on photometric, kinematic, metallicity information, we identify 71 as probable members, including some far out 87 pc. After correcting influence binary using repeated...
ABSTRACT We examine the effects of stellar feedback and bursty star formation on low-mass galaxies ( M = 2 × 10 6 − 5 ⊙ ) using Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized impact dark matter profiles, we investigate component: kinematics, radial migration, size evolution, population gradients. Feedback-driven outflows/inflows drive significant migration over both short long timescales via two processes: (1) outflowing/infalling gas can remain...
We present the survey strategy and early results of "Satellites Around Galactic Analogs" (SAGA) Survey. The SAGA Survey's goal is to measure distribution satellite galaxies around 100 systems analogous Milky Way down luminosity Leo I dwarf galaxy ($ M_r < -12.3 $). define a analog based on $K$-band local environment. Here, we functions for 8 between 20 40 Mpc. These have nearly complete spectroscopic coverage candidate satellites within projected host virial radius $ r_o 20.75 using low...
We present structural parameters from a wide-field homogeneous imaging survey of Milky Way satellites carried out with the MegaCam imagers on 3.6m Canada-France-Hawaii Telescope (CFHT) and 6.5m Magellan-Clay telescope. Our targets an unbiased sample "outer halo" (i.e., substructures having Galactocentric distances greater than 25 kpc) includes classical dSph galaxies, ultra-faint dwarfs, remote globular clusters. combine deep, panoramic $gr$ for 44 archival 14 additional objects (primarily...
Abstract We present the Stage II results from ongoing Satellites Around Galactic Analogs (SAGA) Survey. Upon completion, SAGA Survey will spectroscopically identify satellite galaxies brighter than M r , o = −12.3 around 100 Milky Way (MW) analogs at z ∼ 0.01. In II, we have more quadrupled sample size of I, delivering 127 satellites 36 MW with an improved target selection strategy and deep photometric imaging catalogs Dark Energy Legacy Surveys. obtained 25,372 galaxy redshifts, peaking...
Abstract We describe the discovery of a solar neighborhood ( d = 468 pc) binary system with main-sequence sunlike star and massive noninteracting black hole candidate. The spectral energy distribution visible is described by single stellar model. derive parameters from high signal-to-noise Magellan/MIKE spectrum, classifying as T eff 5972 K, <?CDATA $\mathrm{log}g=4.54$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi>...
Abstract In this paper we describe the survey design for Ultradeep NIRSpec and NIRCam Observations before Epoch of Reionization (UNCOVER) Cycle 1 JWST Treasury program, which executed its early imaging component in 2022 November. The UNCOVER includes ultradeep (∼29–30AB) ∼45 arcmin 2 on around well-studied A2744 galaxy cluster at z = 0.308 will follow up ∼500 galaxies with extremely deep low-resolution spectroscopy NIRSpec/PRISM during summer 2023, repeat visits 2024. We science goals,...
Abstract We present the discovery of Ursa Major III/UNIONS 1, least luminous known satellite Milky Way, which is estimated to have an absolute V -band magnitude <?CDATA $+{2.2}_{-0.3}^{+0.4}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.2</mml:mn> </mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.3</mml:mn> <mml:mn>0.4</mml:mn> </mml:msubsup> </mml:math> mag, equivalent a total stellar mass ${16}_{-5}^{+6}$?>...
Abstract We present NIRCam and NIRISS modules for DOLPHOT, a widely used crowded-field stellar photometry package. describe details of the including pixel masking, astrometric alignment, star finding, photometry, catalog creation, artificial tests. tested these using images M92 (a Milky Way globular cluster), Draco II (an ultrafaint dwarf galaxy), Wolf–Lundmark–Mellote star-forming galaxy). DOLPHOT’s is highly precise, color–magnitude diagrams are deeper have better definition than...
Abstract We present the discovery of Aquarius III, an ultra-faint Milky Way satellite galaxy identified in second data release DECam Local Volume Exploration survey. Based on deeper follow-up imaging with DECam, we find that III is a low-luminosity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mi>V</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mn>2.5</mml:mn>...
We present a measurement of the systemic proper motion Large Magellanic Cloud (LMC) from astrometry with High Resolution Camera (HRC) Advanced for Surveys (ACS) on Hubble Space Telescope (HST). observed LMC fields centered 21 background QSOs that were discovered their optical variability in MACHO database. The are distributed homogeneously behind central few degrees LMC. With 2 epochs HRC data and ~2 year baseline we determine to better than 5% accuracy: mu_W = -2.03 +/- 0.08 mas/yr; mu_N...
We present new metallicity measurements for 298 individual red giant branch stars in eight of the least luminous dwarf spheroidal galaxies (dSphs) Milky Way (MW) system. Our technique is based on medium-resolution Keck DEIMOS spectroscopy coupled with spectral synthesis. first spectroscopic metallicities at [ Fe/H ] < − 3.0 a galaxy, stellar as low = 3.3. Because our [Fe/H] are not tied to empirical calibrators and sensitive arbitrarily metallicities, we able probe this extremely metal-poor...
We present spectra of six metal-poor stars in two the ultra-faint dwarf galaxies orbiting Milky Way (MW), Ursa Major II, and Coma Berenices obtained with Keck/High Resolution Echelle Spectrometer (HIRES). These observations include first high-resolution spectroscopic extremely ([Fe/H] < −3.0) not belonging to MW halo field star population. obtain abundance measurements upper limits for 26 elements between carbon europium. The entire sample spans a range −3.2 [Fe/H] −2.3, we confirm that each...
We investigate the gas content and baryonic Tully-Fisher relationship for extremely low luminosity dwarf galaxies in absolute magnitude range -13.5 > Mr -16. The sample is selected from Sloan Digital Sky Survey consists of 101 which we have obtained follow-up HI observations using Arecibo Observatory Green Bank Telescope. This represents largest homogeneous dwarfs at luminosities with well-measured optical properties. spans a environments, dense groups to truly isolated galaxies. average...
We present spatially resolved internal kinematics and stellar chemical abundances for a sample of dwarf elliptical (dE) galaxies in the Virgo Cluster observed with Keck telescope Echelle Spectrograph Imager. In combination previous measurements, we find that four out 17 dE's have major-axis rotation velocities consistent rotational flattening, while remaining no detectable rotation. Despite this difference kinematics, rotating nonrotating are remarkably similar terms their position...
We present a catalog of Fe, Mg, Si, Ca, and Ti abundances for 2961 stars in eight dwarf satellite galaxies the Milky Way (MW): Sculptor, Fornax, Leo I, Sextans, II, Canes Venatici Ursa Minor, Draco. For purposes validating our measurements, we also observed 445 red giants MW globular clusters 21 field halo. The measurements are based on Keck/DEIMOS medium-resolution spectroscopy (MRS) combined with spectral synthesis. estimate uncertainties [Fe/H] by quantifying dispersion sample...
We present a resolved-star spectroscopic survey of 15 dwarf spheroidal (dSph) satellites the Andromeda Galaxy (M31) as part Spectroscopic and Photometric Landscape Andromeda's Stellar Halo (SPLASH) project. filter foreground contamination from Milky Way (MW) stars, noting that MW substructure is evident in this contaminant sample. also M31 halo field giant identify remainder probable dSph members. then use these members to determine kinematical properties dSphs. For first time, we confirm...