A5082738705- 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
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Scientific Research and Discoveries
- Impact of Light on Environment and Health
- Solar and Space Plasma Dynamics
- Phase Equilibria and Thermodynamics
- Cosmology and Gravitation Theories
- Crystal Structures and Properties
- Ionosphere and magnetosphere dynamics
- Advanced Fluorescence Microscopy Techniques
- CCD and CMOS Imaging Sensors
- Geophysics and Gravity Measurements
- SAS software applications and methods
- Astronomical and nuclear sciences
- Spacecraft and Cryogenic Technologies
Center for Astrophysics Harvard & Smithsonian
2015-2024
Smithsonian Astrophysical Observatory
2002-2022
Harvard University Press
1998-2020
Harvard University
1993-2018
Merck & Co., Inc., Rahway, NJ, USA (United States)
2014
European Southern Observatory
2011
Institut d'Astrophysique de Paris
2011
Vrije Universiteit Brussel
2011
University of Central Lancashire
2010
University of Oxford
2010
We present early observations of the afterglow GRB 030329 and spectroscopic discovery its associated supernova SN 2003dh. obtained spectra each night from March 30.12 (0.6 days after burst) to April 8.13 (UT) (9.6 burst). The cover a wavelength range 350-850 nm. consist power-law continuum (Fν ∝ ν-0.9) with narrow emission lines originating H II regions in host galaxy, indicating low redshift z = 0.1687. However, our taken 2003 5 show broad peaks flux characteristic supernova. Correcting for...
Mid-infrared photometry provides a robust technique for identifying active galaxies. While the ultraviolet to mid-infrared continuum of normal galaxies is dominated by composite stellar black body curve and peaks at approximately 1.6 microns, power law. Consequently, with sufficient wavelength baseline, one can easily distinguish AGN from populations. Mirroring tendency be bluer than in ultraviolet, where (and stars) sample blue, rising portion spectra, tend redder mid-infrared, red, falling...
We present 1210 Johnson/Cousins B, V, R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia): SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, 1996bv. Most the photometry was obtained at Fred Lawrence Whipple Observatory Harvard-Smithsonian Center for Astrophysics in a cooperative observing plan aimed improving database Ia. The redshifts sample range from cz =...
We explore the connection between different classes of active galactic nuclei (AGNs) and evolution their host galaxies, by deriving galaxy properties, clustering, Eddington ratios AGNs selected in radio, X-ray, infrared. study a sample 585 at 0.25 < z 0.8 using redshifts from AGN Galaxy Evolution Survey (AGES) data radio (WSRT 1.4 GHz), X-rays (Chandra XBootes), mid-IR (IRAC Shallow Survey). The IR samples show modest overlap, indicating that to flux limits survey, they represent largely...
We present multiband photometry of 185 type-Ia supernovae (SNe Ia), with over 11,500 observations. These were acquired between 2001 and 2008 at the F. L. Whipple Observatory Harvard-Smithsonian Center for Astrophysics (CfA). This sample contains largest number homogeneously observed reduced nearby SNe Ia (z ≲ 0.08) published to date. It more than doubles sample, bringing SN cosmology point where systematic uncertainties dominate. Our natural system has a precision ≲0.02 mag in BVRIr'i' ≲0.04...
The Hectospec is a 300 optical fiber fed spectrograph commissioned at the MMT in spring of 2004. In configuration pioneered by Autofib instrument Anglo‐Australian Telescope, Hectospec's probes are arranged radial "fisherman on pond" geometry and held position with small magnets. A pair high‐speed, six‐axis robots move buttons between observing configurations within ∼300 s, to an accuracy ∼25 μm. fibers run for 26 m MMT's focal surface bench spectrograph, operating R∼1000–2000. Hectochelle,...
We present UBVRI photometry of 44 Type Ia supernovae (SNe Ia) observed from 1997 to 2001 as part a continuing monitoring campaign at the Fred Lawrence Whipple Observatory Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is largest homogeneously reduced sample SNe date, nearly doubling number well-observed, nearby with published multicolor CCD light curves. large U-band unique addition, important connections high redshift. decline rate SN curves...
Abstract In the ΛCDM paradigm, Galactic stellar halo is predicted to harbor accreted debris of smaller systems. To identify these systems, H3 Spectroscopic Survey, combined with Gaia, gathering 6D phase-space and chemical information in distant Galaxy. Here we present a comprehensive inventory structure within 50 kpc from center using sample 5684 giants at <?CDATA $| b| \gt 40^\circ $?> Z| 2\,\mathrm{kpc}$?> . We known structures including high- α disk, situ (disk stars heated eccentric...
The Panchromatic Hubble Andromeda Treasury is an ongoing Space Telescope Multi-Cycle program to image ∼1/3 of M31's star-forming disk in six filters, spanning from the ultraviolet (UV) near-infrared (NIR). We use Wide Field Camera 3 (WFC3) and Advanced for Surveys (ACS) resolve galaxy into millions individual stars with projected radii 0 20 kpc. full survey will cover a contiguous 0.5 deg2area 828 orbits. Imaging being obtained F275W F336W filters on WFC3/UVIS camera, F475W F814W ACS/WFC,...
Several lines of evidence suggest the Milky Way underwent a major merger at z~2 with galaxy known as Gaia-Sausage-Enceladus (GSE). Here we use H3 Survey data to argue that GSE entered Galaxy on retrograde orbit based population highly stars chemistry similar largely radial debris. We present first tailored, high-resolution N-body simulations merger. From grid ~500 find $M_{*}=5\times10^{8}\ M_{\odot}, M_{\rm{DM}}=2\times10^{11} M_{\odot}$ (a 2.5:1 total mass merger) best matches data. This...
We describe a high‐throughput optical spectrograph that has been in operation at the Cassegrain focus of 1.5‐m Tillinghast reflector since 1994 January. FAST 3 '‐long slit and is typically operated resolutions between 1 6 Å. With collimated beam diameter ∼100 mm, (with 300 lines mm−1 grating 15‐wide slit) offers 4000 Å spectral coverage resolution. FAST's optics are primarily reflective, adequately sized to prevent vignetting, use high‐performance coatings. The high measured system peak...
We present extensive optical and infrared photometry of the afterglow gamma-ray burst (GRB) 030329 its associated supernova (SN) 2003dh over first two months after detection (2003 March 30-May 29 UT). Optical spectroscopy from a variety telescopes is shown and, when combined with photometry, allows an unambiguous separation between SN contributions. The GRB initially power-law continuum but shows significant color variations during week that are unrelated to presence SN. early light curve...
We present multi-band optical photometry of 94 spectroscopically confirmed Type Ia supernovae (SNe Ia) in the redshift range 0.0055–0.073, obtained between 2006 and 2011. There are a total 5522 light-curve points. show that our natural-system SN has precision ≲ 0.03 mag BVr'i', 0.06 u', 0.07 U for points brighter than 17.5 estimate it systematic uncertainty 0.014, 0.010, 0.012, 0.046, 0.073 BVr'i'u'U, respectively. Comparisons standard-system with published light curves comparison stars...
We present new high signal-to-noise spectroscopic data on the M31 globular cluster system, obtained with Hectospec multifiber spectrograph 6.5m MMT. More than 300 clusters have been observed at a resolution of 5A. The primary focus this paper is determination mean metallicities, ages and reddenings. Metallicities were estimated using calibration Lick indices [Fe/H] provided by Galactic GCs. metallicity distribution not generally bimodal, in strong distinction bimodal distribution. Rather,...
We examine the nuclear morphology, kinematics, and stellar populations in nearby S0 galaxy NGC 404 using a combination of adaptive optics assisted near-IR integral-field spectroscopy, optical Hubble Space Telescope imaging. These observations enable study nucleus at level detail possible only nearest galaxies. The surface brightness profile suggests presence three components: bulge, star cluster (NSC), central light excess within radii < 3 pc. components have distinct kinematics with modest...
We present the widest-field resolved stellar map to date of closest ($D\sim3.8$ Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out a projected galactocentric radius $\sim150$ kpc. The dataset is part our ongoing Panoramic Imaging Survey Centaurus and Sculptor (PISCeS) utilizing Magellan/Megacam imager. resolve population old red giant branch stars down $\sim1.5$ mag below tip branch, reaching surface brightness limits as low $\mu_{V,0}\sim32$ arcsec$^{-2}$. resulting...
We present a detailed study of the nuclear star clusters (NSCs) and massive black holes (BHs) four nearest low-mass early-type galaxies: M32, NGC205, NGC5012, NGC5206. measure dynamical masses both BHs NSCs in these galaxies using Gemini/NIFS or VLT/SINFONI stellar kinematics, Hubble Space Telescope (HST) imaging, Jeans Anisotropic Models. detect NGC5102, NGC5206, while we find only an upper limit. These BH mass estimates are consistent with previous measurements M32 those NGC5102 NGC5206...
The oxygen abundance gradients among nebular emission line regions in spiral galaxies have been used as important constraints for models of chemical evolution. We present the largest-ever full-wavelength optical spectroscopic sample nebulae a galaxy (M31). collected spectra 253 H ii and 407 planetary (PNe) with Hectospec multi-fiber spectrograph MMT. measure line-of-sight extinction 199 333 PNe; we derive directly, based on electron temperature, 51 use strong-line methods to estimate 192...
Abstract We present results from MMT/Hectochelle spectroscopy of 390 red giant candidate stars along the line sight to recently discovered Galactic satellite Crater 2. Modeling joint distribution stellar positions, velocities, and metallicities as a mixture 2 foreground populations, we identify ∼62 members 2, for which resolve line-of-sight velocity dispersion <?CDATA ${\sigma }_{{v}_{\mathrm{los}}}$?> = ${2.7}_{-0.3}^{+0.3}$?> km s −1 mean $\langle {v}_{\mathrm{los}}\rangle $?>...
Abstract Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from accretion and disruption smaller systems. This hierarchical assembly is expected to produce a high degree structure in combined phase chemistry space; this should provide relatively direct probe history our Galaxy. Revealing requires precise 3D positions (including distances), velocities, for large samples stars. The Gaia satellite delivering proper motions parallaxes >1...
The Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) is constructing a wide-field map the resolved stellar populations in extended halos these two nearby, prominent galaxies. We present new Magellan/Megacam imaging $\sim3$ deg$^2$ area around A (Cen A), which filled much our coverage to its south, leaving nearly complete halo out projected radius $\sim$150 kpc allowing us identify dwarf have additionally obtained deep Hubble Space Telescope (HST) optical eleven thirteen candidate...
Abstract The archeological record of stars in the Milky Way opens a uniquely detailed window into early formation and assembly galaxies. Here we use 11,000 main-sequence turn-off with well-measured ages, , orbits from H3 Survey Gaia to time major events Galaxy. Located beyond Galactic plane, this sample contains three chemically distinct groups: low-metallicity population, low- α high- groups at higher metallicity. age orbit distributions these populations show that (1) group, which includes...
The Galactic stellar halo is predicted to have formed at least partially from the tidal disruption of accreted dwarf galaxies. This assembly history should be detectable in orbital and chemical properties stars. H3 Survey obtaining spectra for 200,000 stars, and, when combined with Gaia data, providing detailed Unlike previous surveys halo, target selection based solely on magnitude parallax; survey therefore provides a nearly unbiased view entire high latitudes. In this paper we present...
We present deep Magellan/Megacam stellar photometry of four recently discovered faint Milky Way satellites: Sagittarius II (Sgr II), Reticulum (Ret Phoenix (Phe and Tucana III (Tuc III). Our reaches ~2-3 magnitudes deeper than the discovery data, allowing us to revisit properties these new objects (e.g., distance, structural properties, luminosity measurements, signs tidal disturbance). The satellite color-magnitude diagrams show that they are all old (~13.5 Gyr) metal-poor...
Abstract The origins of most stellar streams in the Milky Way are unknown. With improved proper motions provided by Gaia EDR3, we show that orbits 23 Galactic highly clustered orbital phase space. Based on their energies and angular momenta, our sample can plausibly be associated with a specific (disrupted) dwarf galaxy host brought them into Way. For eight also identify likely globular cluster progenitors (four these associations reported here for first time). Some stream surprisingly far...