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  • Lunar and Planetary Science and Exploration  (22)
  • Astrophysics  (21)
  • ASTROPHYSICS
  • 2010-2014  (43)
  • 1
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    The Crust of the Moon as Seen by GRAIL (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-23
    Description: High-resolution gravity data obtained from the dual Gravity Recovery and Interior Laboratory (GRAIL) spacecraft show that the bulk density of the Moon's highlands crust is 2550 kilograms per cubic meter, substantially lower than generally assumed. When combined with remote sensing and sample data, this density implies an average crustal porosity of 12% to depths of at least a few kilometers. Lateral variations in crustal porosity correlate with the largest impact basins, whereas lateral variations in crustal density correlate with crustal composition. The low-bulk crustal density allows construction of a global crustal thickness model that satisfies the Apollo seismic constraints, and with an average crustal thickness between 34 and 43 kilometers, the bulk refractory element composition of the Moon is not required to be enriched with respect to that of Earth.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN6865 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 339; 6120; 671-675
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  • 2
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    First Detection of the [O(sub III)] 88 Micrometers Line at High Redshifts: Characterizing the Starburst and Narrow-Line Regions in Extreme Luminosity Systems (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We have made the first detections of the 88 micrometers [O(sub III)] line from galaxies in the early universe, detecting the line from the lensed active galactic nucleus (AGN)/starburst composite systems APM 08279+5255 at z 3.911 and SMM J02399-0136 at z = 2.8076. The line is exceptionally bright from both systems, with apparent (lensed) luminosities approx.10(exp 11) Solar Luminosity, For APM 08279, the [O(sub III)] line flux can be modeled in a star formation paradigm, with the stellar radiation field dominated by stars with effective temperatures, T(sub eff) 〉 36,000 K, similar to the starburst found in M82. The model implies approx.35% of the total far-IR luminosity of the system is generated by the starburst, with the remainder arising from dust heated by the AGN. The 881,tm line can also be generated in the narrow-line region of the AGN if gas densities are around a few 1000 cu cm. For SMM J02399, the [O(sub III)] line likely arises from HII regions formed by hot (T(sub eff) 〉 40,000 K) young stars in a massive starburst that dominates the far-IR luminosity of the system. The present work demonstrates the utility of the [O(sub III)] line for characterizing starbursts and AGN within galaxies in the early universe. These are the first detections of this astrophysically important line from galaxies beyond a redshift of 0.05.s
    Keywords: Astrophysics
    Type: The Astrophysical Journal Letters; 714; 1; 147-151
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  • 3
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    Detection of the 158 Micrometers[CII] Transition at z=1.3: Evidence for a Galaxy-Wide Starburst (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the detection of 158 micrometer [C II] fine-structure line emission from MIPS J 142824.0+3526l9, a hyperluminous (L(sub IR) approx. 10(exp 13) Solar Luminosity starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L[C II]/L(sub FIR) approx. equals 2 x l0(exp -3) of the far-IR(FIR) continuum. The [C II], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n approx. 10(exp 4.2)/cu cm., and that are illuminated by a far-UV radiation field approx. 10(exp 3.2) times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L[C II]/L(sub F1R) ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C II], but the L[CII]/L(sub FIR) and L(sub CO)/L(sub FIR) ratios are similar to the values seen in nearby starburst galaxies
    Keywords: Astrophysics
    Type: The Astrophysical Journal Letters; 714; 1; 162-166
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  • 4
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    First All-Sky Search for Continuous Gravitational Waves from Unknown Sources in Binary Systems (2014)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to 2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from 0.6 10(exp 3) ls to 6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 10(exp 24) at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN22620 , Physical Review D (ISSN 0031-899X) (e-ISSN 1536-6065); 90; 6; 062010
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  • 5
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    Implications of a High Angular Resolution Image of the Sunyaev-Zel'Dovich Effect in RXJ1347-1145 (2010)
    In:  Other Sources
    Details
    Publication Date: 2018-06-06
    Description: The most X-ray luminous cluster known, RXJ1347-1145 (z = 0.45), has been the object of extensive study across the electromagnetic spectrum. We have imaged the Sunyaev-Zel'dovich effect (SZE) at 90 GHz (lambda = 33 mm) in RXJ1347-1145 at 10" resolution with the 64 pixel MUSTANG bolometer array on the Green Bank Telescope, confirming a previously reported strong, localized enhancement of the SZE 20" to the southeast of the center of X-ray emission. This enhancement of the SZE has been interpreted as shock-heated (〉20keV) gas caused by an ongoing major (low mass ratio) merger event. Our data support this interpretation. We also detect a pronounced asymmetry in the projected cluster pressure profile, with the pressure just east of the cluster core approx. 1.6x higher than just to the west. This is the highest resolution image of the SZE made to date.
    Keywords: Astrophysics
    Type: The Astrophysical Journal; Volume 716; 716-745
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  • 6
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    Spectrum and Morphology of the Two Brightest Milagro Sources in the Cygnus Region: MGRO J2019+37 and MGRO J2031+41 (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analyzed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff. The new analysis technique is based on an energy estimator that uses the fraction of photomultiplier tubes in the observatory that detect the extensive air shower. The photon spectrum is measured in the range 1-100 TeV using the last three years of Milagro data (2005-2008), with the detector in its final configuration. An F-test indicates that MGRO J2019+37 is better fit by a power law with an exponential cutoff than by a simple power law. The best-fitting parameters for the power law with exponential cutoff model are a normalization at 10 TeV of 7(sup +5 sub 2) 10(exp 10)/ s /sq m/ TeV, a spectral index of 2.0(sup +0.5 sub -10), and a cutoff energy of 29(sup +50 sub 16) TeV. MGRO J2031+41 shows no evidence of a cutoff. The best-fitting parameters for a power law are a normalization of 2.1(sup +0.6 sub 0.6) 10(exp 10)/ s/sq m/ TeV and a spectral index of 3.22(sup +0.23 sub 0.18. The overall flux is subject to a approx.. 30% systematic uncertainty. The systematic uncertainty on the power-law indices is approx. 0.1. Both uncertainties have been verified with cosmic-ray data. A comparison with previous results from TeV J2032+4130, MGRO J2031+41, and MGRO J2019+37 is also presented.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN9514 , The Astrophysical Journal; 753; 2; 159
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  • 7
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    Planetary Regolith Delivery Systems for In Situ Resource Utilization (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2012-101 , Earth and Science 2012; Apr 15, 2012 - Apr 18, 2012; Pasadena, CA; United States
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  • 8
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    Low Force Icy Regolith Penetration Technology (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Recent data from the Moon, including LCROSS data, indicate large quantities of water ice and other volatiles frozen into the soil in the permanently shadowed craters near the poles. If verified and exploited, these volatiles will revolutionize spaceflight as an inexpensive source of propellants and other consumables outside Earth's gravity well. This report discusses a preliminary investigation of a method to insert a sensor through such a soiVice mixture to verify the presence, nature, and concentration of the ice. It uses percussion to deliver mechanical energy into the frozen mixture, breaking up the ice and decompacting the soil so that only low reaction forces are required from a rover or spacecraft to push the sensor downward. The tests demonstrate that this method may be ideal for a small platform in lunar gravity. However, there are some cases where the system may not be able to penetrate the icy soil, and there is some risk ofthe sensor becoming stuck so that it cannot be retracted, so further work is needed. A companion project (ISDS for Water Detection on the Lunar Surface) has performed preliminary investigation of a dielectric/thermal sensor for use with this system.
    Keywords: Lunar and Planetary Science and Exploration
    Type: NASA/TM-2011-216302
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  • 9
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    New Concepts for Space-Based Gravitational Wave Missions (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The most astrophysically interesting sources in the gravitational wave spectrum lie in the low-frequency band (0.0001 - 1 Hz), which is only accessible from space. For two decades, the LISA concept has been the leading contender for a detector in this band. Despite a strong recommendation from Astro2010, there is strong motivation to find a less expensive concept, even at the loss of some science. We are searching for a lower cost mission concept by examining alternate orbits, less-capable measurement concepts, radically different implementations of the measurement concept and other cost-saving ideas. We report the results of our searches to date, and summarize the analyses behind them.
    Keywords: Astrophysics
    Type: GSFC.ABS.4428.2011
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  • 10
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    Detection of the 158 Micrometers[CII] Transition at z=1.3: Evidence for a Galaxy-Wide Starburst (2010)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the detection of 158 micron [C II] fine-structure line emission from MIPS J142824.0+352619, a hyperluminous ( L(sub IR) approximates 10(exp 13) L (sub solar)) starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L(sub [Cu II] L(sub Fir) approximates 2 x 10(exp -3) of the far-IR (FIR) continuum. The [C II], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n approximates 10(exp 4.2) /cm(exp 3) , and that are illuminated by a far-UV radiation field approximately 10(exp 3.2) times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L(sub [CII])/L(sub FIR) ratio is higher than observed in local ultralummous infrared galaxies or in the few high-redshift QSOs detected in [C II], but the L(sub [CII])/L(sub FIR) and L(sub CO)/L(sub FIR) ratios are similar to the values seen in nearby starburst galaxies. This suggests that MIPS J142824.0+352619 is a scaled-up version of a starburst nucleus, with the burst extended over several kiloparsecs.
    Keywords: Astrophysics
    Type: The Astrophysical Journal Letters; 714; 162-166
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