Institution
Smithsonian Astrophysical Observatory
Facility•Cambridge, Massachusetts, United States•
About: Smithsonian Astrophysical Observatory is a facility organization based out in Cambridge, Massachusetts, United States. It is known for research contribution in the topics: Galaxy & Stars. The organization has 1665 authors who have published 3622 publications receiving 132183 citations. The organization is also known as: SAO.
Topics: Galaxy, Stars, Telescope, Luminosity, Star formation
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors examined whether disrupted binary stars can fuel black hole growth in the Milky Way and found that a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole can fuel the growth of a black hole.
Abstract: We examine whether disrupted binary stars can fuel black hole growth. In this mechanism, tidal disruption produces a single hypervelocity star (HVS) ejected at high velocity and a former companion star bound to the black hole. After a cluster of bound stars forms, orbital diffusion allows the black hole to accrete stars by tidal disruption at a rate comparable to the capture rate. In the Milky Way, HVSs and the S star cluster imply similar rates of 10{sup -5} to 10{sup -3} yr{sup -1} for binary disruption. These rates are consistent with estimates for the tidal disruption rate in nearby galaxies and imply significant black hole growth from disrupted binaries on 10 Gyr timescales.
43 citations
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TL;DR: In this paper, an analysis of a 24 ks ROSAT Position Sensitive Proprtional Counter (PSPC) image of the interacting galaxies NGC 5194 (M51) and NGC5195 (NGC 5195) shows that X-ray emission is distributed across the whole of the whole galaxy, including diffuse emission and a bright nuclear region, eight individual sources with 0.2-2.2 keV luminosities from 5 to 29 x 10(exp 38) ergs/s, more than 10 times higher than typical bright Galactic X
Abstract: Our analysis of a 24 ks ROSAT Position Sensitive Proprtional Counter (PSPC) image of the interacting galaxies NGC 5194 (M51) and NGC 5195 shows that X-ray emission is distributed across the whole of NGC 5194. In addition to the diffuse emission and a bright nuclear region, eight individual sources were detected with 0.2-2.2 keV luminosities from 5 to 29 x 10(exp 38) ergs/s, more than 10 times higher than typical bright Galactic X-ray sources. The energy distribution of the luminous sources can be characterized by bremsstrahlung spectra with temperatures around 1 keV and low-energy absorption exceeding that expected from our Galaxy. Two sources lie in an inner spiral arm, while five lie along the outer edges of the outer spiral arms. Four sources (R1, R2, R4, R6) lie in or near regions of recent star formation as indicated by H II regions or CO emission from molecular clouds. However, for three of the X-ray sources which fall on the outer edge of the spiral arms (R3, R7, and R8), there is little or no associated CO or H alpha emission. We discuss the origin of the luminous X-ray sources as possibly arising from either massive black holes in binary star systems, supernova remnants, or hot gas associated with star forming regions.
43 citations
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Goddard Space Flight Center1, University of California, Berkeley2, Smithsonian Astrophysical Observatory3, University of Toulouse4, University of New Mexico5, The Catholic University of America6, George Mason University7, University of Alabama in Huntsville8, Air Force Research Laboratory9, University of Orléans10, University of Minnesota11, University of Michigan12, University of Maryland, Baltimore County13, University of Colorado Boulder14
TL;DR: The Parker Solar Probe (PSP) completed its first solar encounter in 2018 November, bringing it closer to the Sun than any previous mission as discussed by the authors, which allowed in situ investigation of the heliospheric current sheet (HCS) inside the orbit of Venus.
Abstract: The Parker Solar Probe (PSP) completed its first solar encounter in 2018 November, bringing it closer to the Sun than any previous mission. This allowed in situ investigation of the heliospheric current sheet (HCS) inside the orbit of Venus. The Parker observations reveal a well defined magnetic sector structure placing the spacecraft in a negative polarity region for most of the encounter. The observed current sheet crossings are compared to the predictions of both potential field source surface and magnetohydrodynamic models. All the model predictions are in good qualitative agreement with the observed crossings of the HCS. The models also generally agree that the HCS was nearly parallel with the solar equator during the inbound leg of the encounter and more significantly inclined during the outbound portion. The current sheet crossings at PSP are also compared to similar measurements made by the Wind spacecraft near Earth at 1 au. After allowing for orbital geometry and propagation effects, a remarkable agreement has been found between the observations of these two spacecraft underlying the large-scale stability of the HCS. Finally, the detailed magnetic field and plasma structure of each crossing is analyzed. Marked differences were observed between PSP and Wind measurements in the type of structures found near the HCS. This suggests that significant evolution of these small solar wind structures takes place before they reach 1 au.
43 citations
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TL;DR: The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey.
Abstract: The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey. Both fields are more than 94% complete to a Galactic extinction corrected R0 = 20.2. Here we describe the redshift survey of the F1 field centered at R.A. = 00h53m25.3s and Decl = 12d33m55s; like F2, the F1 field covers 4 sq deg. The redshift survey of the F1 field includes 9426 new galaxy redshifts measured with Hectospec on the MMT (published here). As a guide to future uses of the combined survey we compare the mass metallicity relation and the distributions of D4000 as a function of stellar mass and redshift for the two fields. The mass-metallicity relations differ by an insignificant 1.6 sigma. For galaxies in the stellar mass range 1.e10 to 1.e11 MSun, the increase in the star-forming fraction with redshift is remarkably similar in the two fields. The seemingly surprising 31-38% difference in the overall galaxy counts in F1 and F2 is probably consistent with the expected cosmic variance given the subtleties of the relative systematics in the two surveys. We also review the Deep Lens Survey cluster detections in the two fields: poorer photometric data for F1 precluded secure detection of the single massive cluster at z = 0.35 that we find in SHELS. Taken together the two fields include 16,055 redshifts for galaxies with R0 <= 20.2 and 20,754 redshifts for galaxies with R <= 20.6. These dense surveys in two well-separated fields provide a basis for future investigations of galaxy properties and large-scale structure.
43 citations
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TL;DR: In this paper, a grid-independent implementation of GEOS-Chem (GCHP) using the Earth System Modeling Framework (ESMF) is presented. GCHP enables the same standard model to operate in a distributed-memory framework for massive parallelization.
Abstract: . Global modeling of atmospheric chemistry is a grand
computational challenge because of the need to simulate large coupled systems
of ∼100 –1000 chemical species interacting with transport on all scales.
Offline chemical transport models (CTMs), where the chemical continuity
equations are solved using meteorological data as input, have usability
advantages and are important vehicles for developing atmospheric chemistry
knowledge that can then be transferred to Earth system models. However, they
have generally not been designed to take advantage of massively parallel
computing architectures. Here, we develop such a high-performance capability
for GEOS-Chem (GCHP), a CTM driven by meteorological data from the NASA
Goddard Earth Observation System (GEOS) and used by hundreds of research
groups worldwide. GCHP is a grid-independent implementation of GEOS-Chem
using the Earth System Modeling Framework (ESMF) that permits the same
standard model to operate in a distributed-memory framework for massive
parallelization. GCHP also allows GEOS-Chem to take advantage of the native
GEOS cubed-sphere grid for greater accuracy and computational efficiency in
simulating transport. GCHP enables GEOS-Chem simulations to be conducted with
high computational scalability up to at least 500 cores, so that global
simulations of stratosphere–troposphere oxidant–aerosol chemistry at C180
spatial resolution ( ∼ 0.5 ∘ × 0.625 ∘ ) or finer
become routinely feasible.
42 citations
Authors
Showing all 1666 results
Name | H-index | Papers | Citations |
---|---|---|---|
Lee Hartmann | 134 | 579 | 57649 |
David W. Latham | 127 | 852 | 67390 |
Chi Lin | 125 | 1313 | 102710 |
William R. Forman | 120 | 800 | 53717 |
Edo Berger | 118 | 578 | 47147 |
Joseph Silk | 108 | 1317 | 58146 |
Jon M. Miller | 107 | 706 | 50126 |
Fabrizio Fiore | 106 | 804 | 43260 |
Randall V. Martin | 105 | 396 | 57917 |
Christopher F. McKee | 103 | 368 | 44919 |
John P. Hughes | 101 | 616 | 36396 |
Wallace L. W. Sargent | 99 | 397 | 30265 |
Bryan Gaensler | 99 | 844 | 39851 |
Alexey Vikhlinin | 99 | 367 | 35822 |
Matthew J. Holman | 99 | 320 | 46577 |