Petaluma, CA, United States
Petaluma, CA, United States

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Lee N.,Institute for Astronomy | Sanders D.B.,Institute for Astronomy | Casey C.M.,Institute for Astronomy | Scoville N.Z.,California Institute of Technology | And 19 more authors.
Astrophysical Journal | Year: 2013

We combine Herschel Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging Receiver maps of the full 2 deg2 Cosmic Evolution Survey (COSMOS) field with existing multi-wavelength data to obtain template and model-independent optical-to-far-infrared spectral energy distributions (SEDs) for 4218 Herschel-selected sources with log(L ⊙IR/L ⊙) = 9.4-13.6 and z = 0.02-3.54. Median SEDs are created by binning the optical to far-infrared (FIR) bands available in COSMOS as a function of infrared luminosity. Herschel probes rest-frame wavelengths where the bulk of the infrared radiation is emitted, allowing us to more accurately determine fundamental dust properties of our sample of infrared luminous galaxies. We find that the SED peak wavelength (λpeak) decreases and the dust mass (M dust) increases with increasing total infrared luminosity (L ⊙IR). In the lowest infrared luminosity galaxies (log(L ⊙IR/L ⊙) = 10.0-11.5), we see evidence of polycyclic aromatic hydrocarbon (PAH) features (λ ∼ 7-9 μm), while in the highest infrared luminosity galaxies (L ⊙IR > 10 12 L ⊙) we see an increasing contribution of hot dust and/or power-law emission, consistent with the presence of heating from an active galactic nucleus (AGN). We study the relationship between stellar mass and star formation rate of our sample of infrared luminous galaxies and find no evidence that Herschel-selected galaxies follow the SFR/M * "main sequence" as previously determined from studies of optically selected, star-forming galaxies. Finally, we compare the mid-infrared to FIR properties of our infrared luminous galaxies using the previously defined diagnostic, IR8 ≡ L ⊙IR/L ⊙8, and find that galaxies with L ⊙IR ≳ 1011.3 L ⊙ tend to systematically lie above (× 3-5) the IR8 "infrared main sequence," suggesting either suppressed PAH emission or an increasing contribution from AGN heating. © 2013. The American Astronomical Society. All rights reserved.

Hung C.-L.,University of Hawaii at Manoa | Sanders D.B.,University of Hawaii at Manoa | Casey C.M.,University of Hawaii at Manoa | Lee N.,University of Hawaii at Manoa | And 15 more authors.
Astrophysical Journal | Year: 2013

Galaxy interactions/mergers have been shown to dominate the population of IR-luminous galaxies (L ⊙IR ≳ 1011.6 L ⊙) in the local universe (z ≲ 0.25). Recent studies based on the relation between galaxies' star formation rates and stellar mass (the SFR-M * relation or the "galaxy main sequence") have suggested that galaxy interaction/mergers may only become significant when galaxies fall well above the galaxy main sequence. Since the typical SFR at a given M * increases with redshift, the existence of the galaxy main sequence implies that massive, IR-luminous galaxies at high z may not necessarily be driven by galaxy interactions. We examine the role of galaxy interactions in the SFR-M * relation by carrying out a morphological analysis of 2084 Herschel-selected galaxies at 0.2 < z < 1.5 in the COSMOS field. Using a detailed visual classification scheme, we show that the fraction of "disk galaxies" decreases and the fraction of "irregular" galaxies increases systematically with increasing L ⊙IR out to z ≲ 1.5 and z ≲ 1.0, respectively. At L ⊙IR >1011.5 L ⊙, ≳ 50% of the objects show evident features of strongly interacting/merger systems, where this percentage is similar to the studies of local IR-luminous galaxies. The fraction of interacting/merger systems also systematically increases with the deviation from the SFR-M * relation, supporting the view that galaxies falling above the main sequence are more dominated by mergers than the main-sequence galaxies. Meanwhile, we find that ≳ 18% of massive IR-luminous "main-sequence galaxies" are classified as interacting systems, where this population may not evolve through the evolutionary track predicted by a simple gas exhaustion model. © 2013. The American Astronomical Society. All rights reserved.

Oetjen H.,Jet Propulsion Laboratory | Oetjen H.,University of California at Los Angeles | Payne V.H.,Jet Propulsion Laboratory | Neu J.L.,Jet Propulsion Laboratory | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2016

The Tropospheric Emission Spectrometer (TES) on Aura and Infrared Atmospheric Sounding Interferometer (IASI) on MetOp-A together provide a time series of 10 years of free-tropospheric ozone with an overlap of 3 years. We characterise the differences between TES and IASI ozone measurements and find that IASI's coarser vertical sensitivity leads to a small (>5 ppb) low bias relative to TES for the free troposphere. The TES-IASI differences are not dependent on season or any other factor and hence the measurements from the two instruments can be merged, after correcting for the offset, in order to study decadal-scale changes in tropospheric ozone. We calculate time series of regional monthly mean ozone in the free troposphere over eastern Asia, the western United States (US), and Europe, carefully accounting for differences in spatial sampling between the instruments. We show that free-tropospheric ozone over Europe and the western US has remained relatively constant over the past decade but that, contrary to expectations, ozone over Asia in recent years does not continue the rapid rate of increase observed from 2004 to 2010. © 2016 Author(s).

Amblard A.,NASA | Amblard A.,BAER Institute | Riguccini L.,NASA | Riguccini L.,BAER Institute | And 6 more authors.
Astrophysical Journal | Year: 2014

We compute the properties of a sample of 221 local, early-type galaxies with a spectral energy distribution (SED) modeling software, CIGALEMC. Concentrating on the star-forming (SF) activity and dust contents, we derive parameters such as the specific star formation rate (sSFR), the dust luminosity, dust mass, and temperature. In our sample, 52% is composed of elliptical (E) galaxies and 48% of lenticular (S0) galaxies. We find a larger proportion of S0 galaxies among galaxies with a large sSFR and large specific dust emission. The stronger activity of S0 galaxies is confirmed by larger dust masses. We investigate the relative proportion of active galactic nuclei (AGNs) and SF galaxies in our sample using spectroscopic Sloan Digital Sky Survey data and near-infrared selection techniques, and find a larger proportion of AGN-dominated galaxies in the S0 sample than the E one. This could corroborate a scenario where blue galaxies evolve into red ellipticals by passing through an S0 AGN active period while quenching its star formation. Finally, we find a good agreement comparing our estimates with color indicators. © 2014. The American Astronomical Society. All rights reserved.

Riguccini L.,Federal University of Rio de Janeiro | Riguccini L.,NASA | Riguccini L.,BAER Institute | Temi P.,BAER Institute | And 5 more authors.
Astrophysical Journal | Year: 2015

We explore the properties of early-type galaxies (ETGs), including ellipticals (E) and lenticulars (S0), in rich environments, such as clusters of galaxies (Virgo and Coma). The L24/LK distribution of ETGs in both Virgo and Coma clusters shows that some S0s have a much larger L24/LK ratio (0.5 to ∼2 dex) than the bulk of the ETG population. This could be interpreted as an enhanced star formation rate in these lenticulars. We compare the optical colors of galaxies in these two clusters and investigate the nature of these sources with a large L24/LK ratio by looking at their spatial distribution within the cluster, analyzing their optical spectra, and looking at their optical colors compared to late-types. We obtain 10 Coma and 3 Virgo early-type sources with larger L24/LK ratios than the bulk of their population. We call these sources mid-infrared enhanced galaxies (MIEGs). In Coma, they are mostly located in the southwest part of the cluster where a substructure is falling onto the main cluster. MIEGs present a lower color than the rest of the ETG sample because of a blue continuum. We interpret the excess L24/LK ratio as evidence for enhanced star formation induced as a consequence of their infall into the main cluster. © 2015. The American Astronomical Society. All rights reserved.

Heldmann J.L.,NASA | Pollard W.,McGill University | McKay C.P.,NASA | Marinova M.M.,NASA | And 7 more authors.
Planetary and Space Science | Year: 2013

The high elevation valleys of the McMurdo Dry Valleys of Antarctica are the only locations on Earth known to contain dry permafrost. The Dry Valleys are a hyper-arid polar desert environment and above 1500 m elevation, air temperatures do not exceed 0 C and thus, similarly to Mars, liquid water is largely absent and instead the hydrologic cycle is dominated by frozen ice and vapor phase processes such as sublimation. These conditions make the high elevation Dry Valleys a key Mars analog location where periglacial processes and geomorphic features, and their use as a diagnostic for subsurface ice, can be studied in situ. Two valleys in the upper Dry Valleys show a diversity of subsurface ice; University Valley is dominated by dry permafrost overlying ice-cemented to ice-bonded ground and nearby middle Beacon Valley is dominated by massive ground ice. In both cases the ice is 10-60 cm below the surface. Here we compare the surface features in these two valleys to assess any correlation with the nature of the subsurface ice and compare these features to similar features seen at the Phoenix landing site on Mars. We conclude that while surface features may be indicative of ground ice, no specific correlations are possible and more direct methods are required to determine the nature of subsurface ice on Mars. © 2013 Published by Elsevier Ltd.

Roush T.L.,NASA | Colaprete A.,NASA | Elphic R.,NASA | Ennico-Smith K.,NASA | And 6 more authors.
Advances in Space Research | Year: 2015

The scientific information collected and evaluated using the Near-Infrared Volatile Spectrometer System (NIRVSS) during the 2012 In Situ Resource Utilization (ISRU) field campaign, exhibits variations related to differing surface materials and presence of volatiles during both rover traverses and auger activities demonstrating the promise of using NIRVSS for volatile prospecting on the lunar surface. © Published by Elsevier Ltd. on behalf of COSPAR.

Nuevo M.,NASA | Nuevo M.,BAER Institute | Materese C.K.,NASA | Materese C.K.,Oak Ridge Associated Universities | Sandford S.A.,NASA
Astrophysical Journal | Year: 2014

Nucleobases, together with deoxyribose/ribose and phosphoric acid, are the building blocks of DNA and RNA for all known life. The presence of nucleobase-like compounds in carbonaceous chondrites delivered to the Earth raises the question of an extraterrestrial origin for the molecules that triggered life on our planet. Whether these molecules are formed in interstellar/protostellar environments, in small parent bodies in the solar system, or both, is currently unclear. Recent experiments show that the UV irradiation of pyrimidine (C4H4N2) in H2O-rich ice mixtures that contain NH3, CH3OH, or CH4leads to the formation of the pyrimidine-based nucleobases uracil, cytosine, and thymine. In this work, we discuss the low-temperature UV irradiation of pyrimidine in realistic astrophysical ice mixtures containing H2O, CH3OH, and NH3, with or without CH4, to search for the production of nucleobases and other prebiotic compounds. These experiments show the presence of uracil, urea, glycerol, hexamethylenetetramine, small amino acids, and small carboxylic acids in all samples. Cytosine was only found in one sample produced from ices irradiated with a higher UV dose, while thymine was not found in any sample, even after irradiation with a higher UV dose. Results are discussed to evaluate the role of the photochemistry of pyrimidine in the inventory of organic molecules detected in meteorites and their astrophysical/astrobiological implications. © 2014. The American Astronomical Society. All rights reserved..

Hollingsworth J.L.,NASA | Kahre M.A.,BAER Institute | Kahre M.A.,NASA
Geophysical Research Letters | Year: 2010

A Mars GCM is utilized to investigate dust lifting and organization associated with extratropical cyclogenesis and frontal waves. The model is applied at high resolution in simulations related to Mars' dust cycle. A single extratropical synoptic weather event is examined to ascertain lifting, transport and convergence/divergence of dust by large-scale cyclonic/anticyclonic weather systems, and the sub-synoptic frontal waves that ensue. Low- and high-pressure cores develop, travel eastward and remain mostly confined within the seasonal CO 2 polar cap. The bulk of dust lifting occurs in the northern-hemisphere western highlands associated with nocturnal down-slope drainage flows, and lifting infrequently occurs near the frontal convergence zone. Dust becomes organized and transported within circulations associated with the synoptic/sub-synoptic circulations accompanying the frontal waves. Dynamical considerations are invoked regarding frontogenesis revealing correlations with regards to dust lifting, organization and transport. Implications of large-scale extratropical weather systems on the martian dust cycle are discussed. © 2010 by the American Geophysical Union.

Heldmann J.L.,NASA | Colaprete A.,NASA | Elphic R.C.,NASA | Mattes G.,NASA | And 7 more authors.
Advances in Space Research | Year: 2015

Future human exploration of the Moon will likely rely on in situ resource utilization (ISRU) to enable long duration lunar missions. Prior to utilizing ISRU on the Moon, the natural resources (in this case lunar volatiles) must be identified and characterized, and ISRU demonstrated on the lunar surface. To enable future uses of ISRU, NASA and the CSA are developing a lunar rover payload that can (1) locate near subsurface volatiles, (2) excavate and analyze samples of the volatile-bearing regolith, and (3) demonstrate the form, extractability and usefulness of the materials. Such investigations are important both for ISRU purposes and for understanding the scientific nature of these intriguing lunar volatile deposits. Temperature models and orbital data suggest near surface volatile concentrations may exist at briefly lit lunar polar locations outside persistently shadowed regions. A lunar rover could be remotely operated at some of these locations for the ∼2-14 days of expected sunlight at relatively low cost. Due to the limited operational time available, both science and rover operations decisions must be made in real time, requiring immediate situational awareness, data analysis, and decision support tools. Given these constraints, such a mission requires a new concept of operations. In this paper we outline the results and lessons learned from an analog field campaign in July 2012 which tested operations for a lunar polar rover concept. A rover was operated in the analog environment of Hawaii by an off-site Flight Control Center, a rover navigation center in Canada, a Science Backroom at NASA Ames Research Center in California, and support teams at NASA Johnson Space Center in Texas and NASA Kennedy Space Center in Florida. We find that this type of mission requires highly efficient, real time, remotely operated rover operations to enable low cost, scientifically relevant exploration of the distribution and nature of lunar polar volatiles. The field demonstration illustrated the need for science operations personnel in constant communications with the flight mission operators and the Science Backroom to provide immediate and continual science support and validation throughout the mission. Specific data analysis tools are also required to enable immediate data monitoring, visualization, and decision making. The field campaign demonstrated that this novel methodology of real-time science operations is possible and applicable to providing important new insights regarding lunar polar volatiles for both science and exploration. © Published by Elsevier Ltd. on behalf of COSPAR.

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