Pinacate-gran Desierto Region, Mexico: SIR-A Data Analysis

NASA Technical Reports Server (NTRS)

Christensen, P.; Greeley, R.; Mchone, J.; Asmerom, Y.; Barnett, S.

1984-01-01

Radar images (SIR-A) from the Columbia space shuttle were used to assess the radar returns of terrain shaped by volcanic, aeolian, and fluvial processes in northwest Sonora. Field studies and photointerpretation show that sand dunes are poorly imaged by SIR-A, in contrast to SEASAT, evidently a consequence of the greater SIR-A incidence angle; star dunes are visible only as small bright spots representing merging arms at dune apices which may act as corner reflectors. Desert grasses and bushes (approx. 2 m high) have little effect on radar brightness. Only larger trees with woody trunks approx. 0.5 m across are effective radar reflectors; their presence contributes to radar bright zones along some arroyos. The radar brightness of lava flows decreases with surface roughness and presence of mantling windblown sediments and weathering products; however, old uplifted (faulted) flows are of equal brightness to fresh, unmantled aa flows. Maar craters display circular patterns of varying radar brightness which represent a combination of geometry, slope, and distribution of surface materials. Some radar bright rings in the Pinacates resemble craters on radar but are observed to be playas encircled by trees.

SPIDERMAN: Fast code to simulate secondary transits and phase curves

NASA Astrophysics Data System (ADS)

Louden, Tom; Kreidberg, Laura

2017-11-01

SPIDERMAN calculates exoplanet phase curves and secondary eclipses with arbitrary surface brightness distributions in two dimensions. The code uses a geometrical algorithm to solve exactly the area of sections of the disc of the planet that are occulted by the star. Approximately 1000 models can be generated per second in typical use, which makes making Markov Chain Monte Carlo analyses practicable. The code is modular and allows comparison of the effect of multiple different brightness distributions for a dataset.

Ultraviolet Imaging Telescope images of the reflection nebula NGC 7023 - Derivation of ultraviolet scattering properties of dust grains

NASA Technical Reports Server (NTRS)

Witt, Adolf N.; Petersohn, Jens K.; Bohlin, Ralph C.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

1992-01-01

The Ultraviolet Imaging Telescope as part of the Astro-1 mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. From the quantitative comparison of the measured surface brightness gradients ratios of nebular to stellar flux, and detail radial surface brightness profiles with corresponding data from the visible, two major conclusions results: (1) the scattering in the near- and far-ultraviolet in this nebula is more strongly forward-directed than in the visible; (2) the dust albedo in the ultraviolet for wavelengths not less than 140 nm is identical to that in the visible, with the exception of the 220 nm bump in the extinction curve. In the wavelengths region of the bump, the albedo is reduced by 25 to 30 percent in comparison with wavelengths regions both shorter and longer. This lower albedo is expected, if the bump is a pure absorption feature.

Do Low Surface Brightness Galaxies Host Stellar Bars?

NASA Astrophysics Data System (ADS)

Cervantes Sodi, Bernardo; Sánchez García, Osbaldo

2017-09-01

With the aim of assessing if low surface brightness galaxies host stellar bars and by studying the dependence of the occurrence of bars as a function of surface brightness, we use the Galaxy Zoo 2 data set to construct a large volume-limited sample of galaxies and then segregate these galaxies as having low or high surface brightness in terms of their central surface brightness. We find that the fraction of low surface brightness galaxies hosting strong bars is systematically lower than that found for high surface brightness galaxies. The dependence of the bar fraction on the central surface brightness is mostly driven by a correlation of the surface brightness with the spin and the gas richness of the galaxies, showing only a minor dependence on the surface brightness. We also find that the length of the bars is strongly dependent on the surface brightness, and although some of this dependence is attributed to the gas content, even at a fixed gas-to-stellar mass ratio, high surface brightness galaxies host longer bars than their low surface brightness counterparts, which we attribute to an anticorrelation of the surface brightness with the spin.

Do Low Surface Brightness Galaxies Host Stellar Bars?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervantes Sodi, Bernardo; Sánchez García, Osbaldo, E-mail: b.cervantes@irya.unam.mx, E-mail: o.sanchez@irya.unam.mx

With the aim of assessing if low surface brightness galaxies host stellar bars and by studying the dependence of the occurrence of bars as a function of surface brightness, we use the Galaxy Zoo 2 data set to construct a large volume-limited sample of galaxies and then segregate these galaxies as having low or high surface brightness in terms of their central surface brightness. We find that the fraction of low surface brightness galaxies hosting strong bars is systematically lower than that found for high surface brightness galaxies. The dependence of the bar fraction on the central surface brightness ismore » mostly driven by a correlation of the surface brightness with the spin and the gas richness of the galaxies, showing only a minor dependence on the surface brightness. We also find that the length of the bars is strongly dependent on the surface brightness, and although some of this dependence is attributed to the gas content, even at a fixed gas-to-stellar mass ratio, high surface brightness galaxies host longer bars than their low surface brightness counterparts, which we attribute to an anticorrelation of the surface brightness with the spin.« less

Star-dust geometries in galaxies: The effect of interstellar matter distributions on optical and infrared properties of late-type galaxies

NASA Technical Reports Server (NTRS)

Capuano, J. M., Jr.; Thronson, H. A., Jr.; Witt, A. N.

1993-01-01

The presence of substantial amounts of interstellar dust in late-type galaxies affects observable parameters such as the optical surface brightness, the color, and the ratio of far-infrared to optical luminosity of these galaxies. We conducted radiative transfer calculations for late-type galaxy environments to examine two different scenarios: (1) the effects of increasing amounts of dust in two fixed geometries with different star distributions; and (2) the effects of an evolving dust-star geometry in which the total amount of dust is held constant, for three different star distributions. The calculations were done for ten photometric bands, ranging from the far-ultraviolet to the near-infrared (K), and scattered light was included in the galactic surface brightness at each wavelength. The energy absorbed throughout these ten photometric bands was assumed to re-emerge in the far-infrared as thermal dust emission. We also considered the evolutionary contraction of a constant amount of dust relative to pre-existing star distributions.

Comparative Analysis of Aerosol Retrievals from MODIS, OMI and MISR Over Sahara Region

NASA Technical Reports Server (NTRS)

Lyapustin, A.; Wang, Y.; Hsu, C.; Terres, O.; Leptoukh, G.; Kalashnikova, O.; Korkin, S.

2011-01-01

MODIS is a wide field-of-view sensor providing daily global observations of the Earth. Currently, global MODIS aerosol retrievals over land are performed with the main Dark Target algorithm complimented with the Deep Blue (DB) Algorithm over bright deserts. The Dark Target algorithm relies on surface parameterization which relates reflectance in MODIS visible bands with the 2.1 micrometer region, whereas the Deep Blue algorithm uses an ancillary angular distribution model of surface reflectance developed from the time series of clear-sky MODIS observations. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm has been developed for MODIS. MAIAC uses a time series and an image based processing to perform simultaneous retrievals of aerosol properties and surface bidirectional reflectance. It is a generic algorithm which works over both dark vegetative surfaces and bright deserts and performs retrievals at 1 km resolution. In this work, we will provide a comparative analysis of DB, MAIAC, MISR and OMI aerosol products over bright deserts of northern Africa.

Evidence of Titan's Climate History from Evaporite Distribution

NASA Astrophysics Data System (ADS)

MacKenzie, Shannon; Barnes, J. W.; Brown, R.; Sotin, C.; Buratti, B. J.; Clark, R.; Baines, K. H.; Nicholson, P. D.; Le Mouelic, S.; Rodriguez, S.

2013-10-01

5-μm bright material on the surface of Titan has been positively correlated with the shores of RADAR-dark (liquid-filled) and the bottoms of RADAR-bright (empty) lakebeds in the region just south of Ligea Mare by Barnes et al. (2011). This water ice-poor spectral unit was thus proposed to be evaporite, the formerly-dissolved solute deposits left behind when the solvent (here presumably a methane/ethane mixture) evaporates. Because evaporite forms under specific conditions—solute and solvent at or near saturation, no outlets or other means of affecting the solution balance, etc.—the presence of evaporite can shed light on Titan's climate history. Adding to the previously identified cases, we use the breadth of available Cassini VIMS data to comprehensively map new instances of evaporite. In particular, we found new instances of evaporite in the north polar region and the midlatitudes. Our map of the global distribution of Titan's 5-μm-bright deposits can be used to constrain the historical evolution of Titan's surface volatile inventory and may bear on the question of the time variation of the methane concentration in Titan's atmosphere. Furthermore, we explore the implications of the idea that the 5-$\\mu$m-bright areas are indeed mostly evaporitic in nature with respect to the relationship between the regional and global volatile cycles.

Flattening and surface-brightness of the fast-rotating star δ Persei with the visible VEGA/CHARA interferometer

NASA Astrophysics Data System (ADS)

Challouf, M.; Nardetto, N.; Domiciano de Souza, A.; Mourard, D.; Tallon-Bosc, I.; Aroui, H.; Farrington, C.; Ligi, R.; Meilland, A.; Mouelhi, M.

2017-08-01

Context. Rapid rotation is a common feature for massive stars, with important consequences on their physical structure, flux distribution and evolution. Fast-rotating stars are flattened and show gravity darkening (non-uniform surface intensity distribution). Another important and less studied impact of fast-rotation in early-type stars is its influence on the surface brightness colour relation (hereafter SBCR), which could be used to derive the distance of eclipsing binaries. Aims: The purpose of this paper is to determine the flattening of the fast-rotating B-type star δ Per using visible long-baseline interferometry. A second goal is to evaluate the impact of rotation and gravity darkening on the V - K colour and surface brightness of the star. Methods: The B-type star δ Per was observed with the VEGA/CHARA interferometer, which can measure spatial resolutions down to 0.3 mas and spectral resolving power of 5000 in the visible. We first used a toy model to derive the position angle of the rotation axis of the star in the plane of the sky. Then we used a code of stellar rotation, CHARRON, in order to derive the physical parameters of the star. Finally, by considering two cases, a static reference star and our best model of δ Per, we can quantify the impact of fast rotation on the surface brightness colour relation (SBCR). Results: We find a position angle of 23 ± 6 degrees. The polar axis angular diameter of δ Per is θp = 0.544 ± 0.007 mas, and the derived flatness is r = 1.121 ± 0.013. We derive an inclination angle for the star of I = 85+ 5-20 degrees and a projected rotation velocity Vsini = 175+ 8-11 km s-1 (or 57% of the critical velocity). We find also that the rotation and inclination angle of δ Per keeps the V - K colour unchanged while it decreasing its surface-brightness by about 0.05 mag. Conclusions: Correcting the impact of rotation on the SBCR of early-type stars appears feasible using visible interferometry and dedicated models.

Seasonal Changes in Titan's Surface Temperatures

NASA Technical Reports Server (NTRS)

Jennins, Donald E.; Cottini, V.; Nixon, C. A.; Flasar, F. M.; Kunde, V. G.; Samuelson, R. E.; Romani, P. N.; Hesman, B. E.; Carlson, R. C.; Gorius, N. J. P.;

Titan's Surface Brightness Temperatures and H2 Mole Fraction from Cassini CIRS

NASA Technical Reports Server (NTRS)

Jennings, Donald E.; Flasar, F. M.; Kunde, V. G.; Samuelson, R. E.; Pearl, J. C.; Nixon, C. A.; Carlson, R. C.; Mamoutkine, A. A.; Brasunas, J. C.; Guandique, E.;

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the possibility of studying the temporal evolution of a surface relief directly during exposure to high-power radiation

NASA Astrophysics Data System (ADS)

Abramov, D. V.; Arakelyan, S. M.; Galkin, A. F.; Klimovskii, Ivan I.; Kucherik, A. O.; Prokoshev, V. G.

2006-06-01

The video image of the graphite surface exposed to focused laser radiation is obtained with the help of a laser monitor. A bright ring moving over the heated surface was observed. A method for reconstructing the surface relief from the video image is proposed and realised. The method is based on the measurement of the angular distribution of the light intensity scattered by the graphite sample surface. The surface relief of the graphite sample changing in time is reconstructed. The relative change in the relief height during laser excitation is measured. The statistical characteristics of the reconstructed graphite surface shape and their variation during laser irradiation are studied. It is found that a circular convexity appears within the bright ring. The formation mechanism of this convexity requires further investigations.

Discovery of Diffuse Dwarf Galaxy Candidates around M101

NASA Astrophysics Data System (ADS)

Bennet, P.; Sand, D. J.; Crnojević, D.; Spekkens, K.; Zaritsky, D.; Karunakaran, A.

2017-11-01

We have conducted a search of a 9 deg2 region of the Canada-France-Hawaii-Telescope Legacy Survey around the Milky Way analog M101 (D ˜ 7 Mpc), in order to look for previously unknown low-surface-brightness galaxies. This search has uncovered 38 new low-surface-brightness dwarf candidates, and confirmed 11 previously reported galaxies, all with central surface brightness μ(g, 0) > 23 mag arcsec-2, potentially extending the satellite luminosity function for the M101 group by ˜1.2 mag. The search was conducted using an algorithm that nearly automates the detection of diffuse dwarf galaxies. The candidates’ small sizes and low surface brightnesses mean that the faintest of these objects would likely be missed by traditional visual or computer detection techniques. The dwarf galaxy candidates span a range of -7.1 ≥ M g ≥ -10.2 and half-light radii of 118-540 pc at the distance of M101, and they are well fit by simple Sérsic surface brightness profiles. These properties are consistent with dwarfs in the Local Group, and to match the Local Group luminosity function, ˜10-20 of these candidates should be satellites of M101. Association with a massive host is supported by the lack of detected star formation and the overdensity of candidates around M101 compared to the field. The spatial distribution of the dwarf candidates is highly asymmetric, and concentrated to the northeast of M101, therefore distance measurements will be required to determine if these are genuine members of the M101 group.

Thermal inertia mapping of Mars from 60°S to 60°N

USGS Publications Warehouse

Palluconi, Frank Don; Kieffer, Hugh H.

1981-01-01

Twenty-micrometer brightness temperatures are used to derive the thermal inertia for 81% of the Martian surface between latitudes ±60°. These data were acquired by the two Viking Infrared Thermal Mappers in 1977 and 1978 following the two global dust storms of 1977. The spatial resolution used is 2° in latitude by 2° in longitude and the total range in derived inertia is . The distribution of thermal inertia is strongly bimodal with all values of thermal inertia less than  being associated with three disjoint bright regions mostly in the northern hemisphere. Sufficient dust is raised in global storms to provide fine material adequate to produce these low-inertia areas but the specific deposition mechanism has not been defined. At the low resolution used, no complete exposures of clean rock were found. There is some tendency for darker material to be associated with higher thermal inertia, although the trend is far from one to one. The distribution of high- and low-inertia areas is sufficiently nonrandom to produce a variation in whole-disk brightness temperature with central meridian longitude. This variation and the change in surface kinetic temperature associated with dust storms are factors in establishing the whole-disk brightness temperature at radio and infrared wavelengths and will be important for those who use Mars as a calibration source.

SNR radio spectral index distribution and its correlation with polarization. a case study: the Lupus Loop

NASA Astrophysics Data System (ADS)

Borka Jovanović, V.; Jovanović, P.; Borka, D.

2017-04-01

We use radio-continuum all-sky surveys at 1420 and 408 MHz with the aim to investigate properties of the Galactic radio source Lupus Loop. The survey data at 1435 MHz, with the linear polarization of the southern sky, are also used. We calculate properties of this supernova remnant: the brightness temperature, surface brightness and radio spectral index. To determine its borders and to calculate its properties, we use the method we have developed. The non-thermal nature of its radiation is confirmed. The distribution of spectral index over its area is also given. A significant correlation between the radio spectral index distribution and the corresponding polarized intensity distribution inside the loop borders is found, indicating that the polarization maps could provide us information about the distribution of the interstellar medium, and thus could represent one additional way to search for new Galactic loops.

Atmospheric transformation of solar radiation reflected from the ocean

NASA Technical Reports Server (NTRS)

Malkevich, M. S.; Istomina, L. G.; Hovis, W. A., Jr.

1977-01-01

Airborne measurements of the brightness spectrum of the Atlantic Ocean in the wavelength region from 0.4 to 0.7 micron are analyzed. These measurements were made over a tropical region of the Atlantic from an aircraft at heights of 0.3 and 10.5 km during the TROPEX-72 experiment. The results are used to estimate the contribution of the atmosphere to the overall brightness of the ocean-atmosphere system. It is concluded that: (1) the atmosphere decreases the absolute brightness of the ocean by a factor of 5 to 10 and also strongly affects the spectral behavior of solar radiation reflected from the ocean surface; (2) the atmospheric contribution to overall brightness may vary considerably under real conditions; (3) finely dispersed particles and Rayleigh scattering affect the spectral distribution of solar radiation; and (4) the spectral composition of ocean-atmosphere brightness may be completely governed by the atmosphere.

A medium-bright quasar sample - New quasar surface densities in the magnitude range from 16.4 to 17.65 for B

NASA Technical Reports Server (NTRS)

Mitchell, K. J.; Warnock, A., III; Usher, P. D.

1984-01-01

A new medium-bright quasar sample (MBQS) is constructed from spectroscopic observations of 140 bright objects selected for varying degrees of blue and ultraviolet excess (B-UVX) in five Palomar 1.2 m Schmidt fields. The MBQS contains 32 quasars with B less than 17.65 mag. The new integral surface densities in the B range from 16.45 to 17.65 mag are approximately 40 percent (or more) higher than expected. The MBQS and its redshift distribution increase the area of the Hubble diagram covered by complete samples of quasars. The general spectroscopic results indicate that the three-color classification process used to catalog the spectroscopic candidates (1) has efficiently separated the intrinsically B-UVX stellar objects from the Population II subdwarfs and (2) has produced samples of B-UVX objects which are more complete than samples selected by (U - B) color alone.

Infrared photometric behavior and opposition effect of Mars

NASA Technical Reports Server (NTRS)

Erard, S.; Bibring, J-P.; Drossart, P.

1992-01-01

Although the instrument wasn't designed for this purpose, data from the imaging spectrometer ISM may be used for studying photometric variations of Mars reflectance, that are related to the surface materials and aerosols physical properties. ISM flew aboard the Phobos-2 spacecraft which orbited Mars from January to March, 1989. About 40,000 spectra were acquired in 128 channels ranging from 0.76 to 3.16 micro-m, with a spatial resolution of 25 km and a signal-to-noise ratio ranging up to 1000. Analysis of the results leads to the following conclusions: width variations of the opposition surge can be related to differences in porosity or grain size distribution on the various domains, with little or no effect from suspended dust. As the biggest effects are observed on dark and bright materials, intermediate behaviors on average-bright regions cannot result from a mixing process, but are more likely to come from either cementation processes or modification of the grain size distribution under the influence of wind, which under Martian conditions preferentially removes the biggest particles. Thus, a surface dust consisting in big bright and small dark grains could explain the observations.

Volcanism on Io: New insights from global geologic mapping

USGS Publications Warehouse

Williams, D.A.; Keszthelyi, L.P.; Crown, D.A.; Yff, J.A.; Jaeger, W.L.; Schenk, P.M.; Geissler, P.E.; Becker, T.L.

2011-01-01

We produced the first complete, 1:15M-scale global geologic map of Jupiter's moon Io, based on a set of monochrome and color Galileo-Voyager image mosaics produced at a spatial resolution of 1km/pixel. The surface of Io was mapped into 19 units based on albedo, color and surface morphology, and is subdivided as follows: plains (65.8% of surface), lava flow fields (28.5%), mountains (3.2%), and patera floors (2.5%). Diffuse deposits (DD) that mantle the other units cover ???18% of Io's surface, and are distributed as follows: red (8.6% of surface), white (6.9%), yellow (2.1%), black (0.6%), and green (???0.01%). Analyses of the geographical and areal distribution of these units yield a number of results, summarized below. (1) The distribution of plains units of different colors is generally geographically constrained: Red-brown plains occur >??30?? latitude, and are thought to result from enhanced alteration of other units induced by radiation coming in from the poles. White plains (possibly dominated by SO2+contaminants) occur mostly in the equatorial antijovian region (??30??, 90-230??W), possibly indicative of a regional cold trap. Outliers of white, yellow, and red-brown plains in other regions may result from long-term accumulation of white, yellow, and red diffuse deposits, respectively. (2) Bright (possibly sulfur-rich) flow fields make up 30% more lava flow fields than dark (presumably silicate) flows (56.5% vs. 43.5%), and only 18% of bright flow fields occur within 10km of dark flow fields. These results suggest that secondary sulfurous volcanism (where a bright-dark association is expected) could be responsible for only a fraction of Io's recent bright flows, and that primary sulfur-rich effusions could be an important component of Io's recent volcanism. An unusual concentration of bright flows at ???45-75??N, ???60-120??W could be indicative of more extensive primary sulfurous volcanism in the recent past. However, it remains unclear whether most bright flows are bright because they are sulfur flows, or because they are cold silicate flows covered in sulfur-rich particles from plume fallout. (3) We mapped 425 paterae (volcano-tectonic depressions), up from 417 previously identified by Radebaugh et al. (Radebaugh, J., Keszthelyi, L.P., McEwen, A.S., Turtle, E.P., Jaeger, W., Milazzo, M. [2001]. J. Geophys. Res. 106, 33005-33020). Although these features cover only 2.5% of Io's surface, they correspond to 64% of all detected hot spots; 45% of all hot spots are associated with the freshest dark patera floors, reflecting the importance of active silicate volcanism to Io's heat flow. (4) Mountains cover only ???3% of the surface, although the transition from mountains to plains is gradational with the available imagery. 49% of all mountains are lineated and presumably layered, showing evidence of linear structures supportive of a tectonic origin. In contrast, only 6% of visible mountains are mottled (showing hummocks indicative of mass wasting) and 4% are tholi (domes or shields), consistent with a volcanic origin. (5) Initial analyses of the geographic distributions of map units show no significant longitudinal variation in the quantity of Io's mountains or paterae, in contrast to earlier studies. This is because we use the area of mountain and patera materials as opposed to the number of structures, and our result suggests that the previously proposed anti-correlation of mountains and paterae (Schenk, P., Hargitai, H., Wilson, R., McEwen, A., Thomas, P. [2001]. J. Geophys. Res. 106, 33201-33222; Kirchoff, M.R., McKinnon, W.B., Schenk, P.M. [2011]. Earth Planet. Sci. Lett. 301, 22-30) is more complex than previously thought. There is also a slight decrease in surface area of lava flows toward the poles of Io, perhaps indicative of variations in volcanic activity. (6) The freshest bright and dark flows make up about 29% of all of Io's flow fields, suggesting active emplacement is occurring in less than a third of Io's

Surface brightness and color distributions in blue compact dwarf galaxies. I - Haro 2, an extreme example of a star-forming young elliptical galaxy

NASA Technical Reports Server (NTRS)

Loose, Hans-Hermann; Thuan, Trinh X.

1986-01-01

The first results of a large-scale program to study the morphology and structure of blue compact dwarf galaxies from CCD observations are presented. The observations and reduction procedures are described, and surface brightness and color profiles are shown. The results are used to discuss the morphological type of Haro 2 and its stellar populations. It is found that Haro 2 appears to be an extreme example of an elliptical galaxy undergoing intense star formation in its central regions, and that the oldest stars it contains were made only about four million yr ago. The 'missing' mass problem of Haro 2 is also discussed.

The estimation of the propagation delay through the troposphere from microwave radiometer data. [very long base interferometry

NASA Technical Reports Server (NTRS)

Moran, J. M.; Rosen, B. R.

1980-01-01

The uncertainity in propagation delay estimates is due primarily to tropospheric water, the total amount and vertical distribution of which is variable. Because water vapor both delays and attenuates microwave signals, the propagation delay, or wet path length, can be estimated from the microwave brightness temperature near the 22.235 GHz transition of water vapor. The data from a total of 240 radiosonde launches taken simultaneously were analyzed. Estimates of brightness temperature at 19 and 22 GHz and wet path length were made from these data. The wet path length in the zenith direction could be estimated from the surface water vapor density to an accuracy of 5 cm for the summer data and 2 cm for winter data. Using the brightness temperatures, the wet path could be estimated to an accuracy of 0.3 cm. Two dual frequency radiometers were refurbished in order to test these techniques. These radiometers were capable of measuring the difference in the brightness temperature at 30 deg elevation angle and at the zenith to an accuracy of about 1 K. In August 1975, 45 radiosondes were launched over an 11 day period. Brightness temperature measurements were made simultaneously at 19 and 22 GHz with the radiometers. The rms error for the estimation of wet path length from surface meteorological parameters was 3.2 cm, and from the radiometer brightness temperatures, 1.5 cm.

Size Dependence of Dust Distribution around the Earth Orbit

NASA Astrophysics Data System (ADS)

Ueda, Takahiro; Kobayashi, Hiroshi; Takeuchi, Taku; Ishihara, Daisuke; Kondo, Toru; Kaneda, Hidehiro

2017-05-01

In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting-Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI. The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μm band and 3.0% in the 18 μm band. In order to reveal dust properties causing leading-trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and a dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading-trailing asymmetry so that intermediate sized dust (˜10-100 μm) produces a greater asymmetry than zodiacal light. The leading-trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μm and 18 μm bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μm and 18 μm bands, respectively, if the maximum dust radius is set to be s max = 3000 μm. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ˜10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.

Size Dependence of Dust Distribution around the Earth Orbit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueda, Takahiro; Takeuchi, Taku; Kobayashi, Hiroshi

In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting–Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI . The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μ m band and 3.0% in the 18 μ m band. In order to reveal dust properties causing leading–trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and amore » dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading–trailing asymmetry so that intermediate sized dust (∼10–100 μ m) produces a greater asymmetry than zodiacal light. The leading–trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μ m and 18 μ m bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μ m and 18 μ m bands, respectively, if the maximum dust radius is set to be s {sub max} = 3000 μ m. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ∼10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.« less

Suppression of cooling by strong magnetic fields in white dwarf stars.

PubMed

Valyavin, G; Shulyak, D; Wade, G A; Antonyuk, K; Zharikov, S V; Galazutdinov, G A; Plachinda, S; Bagnulo, S; Machado, L Fox; Alvarez, M; Clark, D M; Lopez, J M; Hiriart, D; Han, Inwoo; Jeon, Young-Beom; Zurita, C; Mujica, R; Burlakova, T; Szeifert, T; Burenkov, A

2014-11-06

Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

Chemical abundances in low surface brightness galaxies: Implications for their evolution

NASA Technical Reports Server (NTRS)

Mcgaugh, S. S.; Bothun, G. D.

1993-01-01

Low Surface Brightness (LSB) galaxies are an important but often neglected part of the galaxy content of the universe. Their importance stems both from the selection effects which cause them to be under-represented in galaxy catalogs, and from what they can tell us about the physical processes of galaxy evolution that has resulted in something other than the traditional Hubble sequence of spirals. An important constraint for any evolutionary model is the present day chemical abundances of LSB disks. Towards this end, spectra for a sample of 75 H 2 regions distributed in 20 LSB disks galaxies were obtained. Structurally, this sample is defined as having B(0) fainter than 23.0 mag arcsec(sup -2) and scale lengths that cluster either around 3 kpc or 10 kpc. In fact, structurally, these galaxies are very similar to the high surface brightness spirals which define the Hubble sequence. Thus, our sample galaxies are not dwarf galaxies but instead have masses comparable to or in excess of the Milky Way. The basic results from these observations are summarized.

Modeling Self-subtraction in Angular Differential Imaging: Application to the HD 32297 Debris Disk

NASA Astrophysics Data System (ADS)

Esposito, Thomas M.; Fitzgerald, Michael P.; Graham, James R.; Kalas, Paul

2014-01-01

We present a new technique for forward-modeling self-subtraction of spatially extended emission in observations processed with angular differential imaging (ADI) algorithms. High-contrast direct imaging of circumstellar disks is limited by quasi-static speckle noise, and ADI is commonly used to suppress those speckles. However, the application of ADI can result in self-subtraction of the disk signal due to the disk's finite spatial extent. This signal attenuation varies with radial separation and biases measurements of the disk's surface brightness, thereby compromising inferences regarding the physical processes responsible for the dust distribution. To compensate for this attenuation, we forward model the disk structure and compute the form of the self-subtraction function at each separation. As a proof of concept, we apply our method to 1.6 and 2.2 μm Keck adaptive optics NIRC2 scattered-light observations of the HD 32297 debris disk reduced using a variant of the "locally optimized combination of images" algorithm. We are able to recover disk surface brightness that was otherwise lost to self-subtraction and produce simplified models of the brightness distribution as it appears with and without self-subtraction. From the latter models, we extract radial profiles for the disk's brightness, width, midplane position, and color that are unbiased by self-subtraction. Our analysis of these measurements indicates a break in the brightness profile power law at r ≈ 110 AU and a disk width that increases with separation from the star. We also verify disk curvature that displaces the midplane by up to 30 AU toward the northwest relative to a straight fiducial midplane.

A New Approach to Galaxy Morphology. I. Analysis of the Sloan Digital Sky Survey Early Data Release

NASA Astrophysics Data System (ADS)

Abraham, Roberto G.; van den Bergh, Sidney; Nair, Preethi

2003-05-01

In this paper we present a new statistic for quantifying galaxy morphology based on measurements of the Gini coefficient of galaxy light distributions. This statistic is easy to measure and is commonly used in econometrics to measure how wealth is distributed in human populations. When applied to galaxy images, the Gini coefficient provides a quantitative measure of the inequality with which a galaxy's light is distributed among its constituent pixels. We measure the Gini coefficient of local galaxies in the Early Data Release of the Sloan Digital Sky Survey and demonstrate that this quantity is closely correlated with measurements of central concentration, but with significant scatter. This scatter is almost entirely due to variations in the mean surface brightness of galaxies. By exploring the distribution of galaxies in the three-dimensional parameter space defined by the Gini coefficient, central concentration, and mean surface brightness, we show that all nearby galaxies lie on a well-defined two-dimensional surface (a slightly warped plane) embedded within a three-dimensional parameter space. By associating each galaxy sample with the equation of this plane, we can encode the morphological composition of the entire SDSS g*-band sample using the following three numbers: {22.451, 5.366, 7.010}. The i*-band sample is encoded as {22.149, 5.373, and 7.627}.

Europa Crescent

NASA Image and Video Library

1998-06-04

This archival image taken by NASA Voyager 2, is of Europa, the smallest Galilean satellite. The bright areas are probably ice deposits, whereas the darkened areas may be the rocky surface or areas with a more patchy distribution of ice. http://photojournal.jpl.nasa.gov/catalog/PIA00325

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang-Condell, Hannah; Wilner, David; Andrews, Sean; Kraus, Adam; Dahm, Scott;

Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk Around HD 32297

NASA Technical Reports Server (NTRS)

Currie, Thayne; Rodigas, Timothy J.; Debes, John; Plavchan, Peter; Kuchner, Marc; Jang, Condell, Hannah; Wilner, David; Andrews, Sean; Dahm, Scott; Robitaille,Thomas

2012-01-01

We present Keck/NIRC2 K(sub s) band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0.3 - 2.5" (approx equals 35 - 280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to r approx equals 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50 - 100% brighter at r = 35 - 80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model fur a single dust belt including a phase function with two components and a 5 - 10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry and the profile at wider separations (r > 110 AU). Although there may be a1ternate explanations, agreement between the SW disk brightness peak and disk's peak rom emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1 - 1 mm-sized grains at approx equal 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

V405 ANDROMEDA REVISITED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribeiro, T.; Baptista, R.; Kafka, S.

We present a multi-epoch time-resolved high-resolution optical spectroscopy study of the short-period (P{sub orb} = 11.2 hr) eclipsing M0V+M5V RS CVn binary V405 Andromeda. By means of indirect imaging techniques, namely Doppler imaging, we study the surface activity features of the M0V component of the system. A modified version of a Doppler imaging code, which takes into account the tidal distortion of the surface of the star, is applied to the multi-epoch data set in order to provide indirect images of the stellar surface. The multi-epoch surface brightness distributions show a low intensity 'belt' of spots at latitudes {+-}40{sup 0}more » and a noticeable absence of high latitude features or polar spots on the primary star of V405 Andromeda. They also reveal slow evolution of the spot distribution over {approx}4 yr. An entropy landscape procedure is used in order to find the set of binary parameters that lead to the smoothest surface brightness distributions. As a result, we find M{sub 1} = 0.51 {+-} 0.03 M{sub sun}, M{sub 2} = 0.21 {+-} 0.01 M{sub sun}, R{sub 1} = 0.71 {+-} 0.01 R{sub sun}, and an inclination i = 65{sup 0} {+-} 1{sup 0}. The resulting systemic velocity is distinct for different epochs, raising the possibility of the existence of a third body in the system.« less

The Tolman Surface Brightness Test for the Reality of the Expansion. III. Hubble Space Telescope Profile and Surface Brightness Data for Early-Type Galaxies in Three High-Redshift Clusters

NASA Astrophysics Data System (ADS)

Lubin, Lori M.; Sandage, Allan

2001-09-01

Photometric data for 34 early-type galaxies in the three high-redshift clusters Cl 1324+3011 (z=0.76), Cl 1604+4304 (z=0.90), and Cl 1604+4321 (z=0.92), observed with the Hubble Space Telescope (HST) and with the Keck 10 m telescopes by Oke, Postman, & Lubin, are analyzed to obtain the photometric parameters of mean surface brightness, magnitudes for the growth curves, and angular radii at various Petrosian η radii. The angular radii at η=1.3 mag for the program galaxies are all larger than 0.24". All the galaxies are well resolved at this angular size using HST, whose point-spread function is 0.05", half-width at half-maximum. The data for each of the program galaxies are listed at η=1.0, 1.3, 1.5, 1.7, and 2.0 mag. They are corrected by color equations and K-terms for the effects of redshift to the rest-frame Cape/Cousins I for Cl 1324+3011 and Cl 1604+4304 and R for Cl 1604+4321. The K-corrections are calculated from synthetic spectral energy distributions derived from evolving stellar population models of Bruzual & Charlot, that have been fitted to the observed broadband (BVRI) AB magnitudes of each program galaxy. The listed photometric data are independent of all cosmological parameters. They are the source data for the Tolman surface brightness test made in Paper IV.

Printing quality control automation

NASA Astrophysics Data System (ADS)

Trapeznikova, O. V.

2018-04-01

One of the most important problems in the concept of standardizing the process of offset printing is the control the quality rating of printing and its automation. To solve the problem, a software has been developed taking into account the specifics of printing system components and the behavior in printing process. In order to characterize the distribution of ink layer on the printed substrate the so-called deviation of the ink layer thickness on the sheet from nominal surface is suggested. The geometric data construction the surface projections of the color gamut bodies allows to visualize the color reproduction gamut of printing systems in brightness ranges and specific color sectors, that provides a qualitative comparison of the system by the reproduction of individual colors in a varying ranges of brightness.

Statistical theory and applications of lock-in carrierographic image pixel brightness dependence on multi-crystalline Si solar cell efficiency and photovoltage

NASA Astrophysics Data System (ADS)

Mandelis, Andreas; Zhang, Yu; Melnikov, Alexander

2012-09-01

A solar cell lock-in carrierographic image generation theory based on the concept of non-equilibrium radiation chemical potential was developed. An optoelectronic diode expression was derived linking the emitted radiative recombination photon flux (current density), the solar conversion efficiency, and the external load resistance via the closed- and/or open-circuit photovoltage. The expression was shown to be of a structure similar to the conventional electrical photovoltaic I-V equation, thereby allowing the carrierographic image to be used in a quantitative statistical pixel brightness distribution analysis with outcome being the non-contacting measurement of mean values of these important parameters averaged over the entire illuminated solar cell surface. This is the optoelectronic equivalent of the electrical (contacting) measurement method using an external resistor circuit and the outputs of the solar cell electrode grid, the latter acting as an averaging distribution network over the surface. The statistical theory was confirmed using multi-crystalline Si solar cells.

IRAS surface brightness maps of reflection nebulae in the Pleiades

NASA Technical Reports Server (NTRS)

Castelaz, Michael W.; Werner, M. W.; Sellgren, K.

1987-01-01

Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.

An analysis of source structure effects in radio interferometry measurements

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1980-01-01

To begin a study of structure effects, this report presents a theoretical framework, proposes an effective position approach to structure corrections based on brightness distribution measurements, and analyzes examples of analytical and measured brightness distributions. Other topics include the effect of the frequency dependence of a brightness distribution on bandwidth synthesis (BWS) delay, the determination of the absolute location of a measured brightness distribution, and structure effects in dual frequency calibration of charged particle delays. For the 10 measured distributions analyzed, it was found that the structure effect in BWS delay at X-band (3.6 cm) can reach 30 cm, but typically falls in the range of 0 to 5 cm. A trial limit equation that is dependent on visibility was successfully tested against the 10 measured brightness distributions (seven sources). If the validity of this particular equation for an upper limit can be established for nearly all sources, the structure effect in BWS delay could be greatly reduced without supplementary measurements of brightness distributions.

Adaptive focusing of laser radiation onto a rough reflecting surface through the turbulent and nonlinear atmosphere

NASA Astrophysics Data System (ADS)

Vorontsov, Mikhail A.; Kolosov, Valeriy V.

2004-12-01

Target-in-the-loop (TIL) wave propagation geometry represents perhaps the most challenging case for adaptive optics applications that are related with maximization of irradiance power density on extended remotely located surfaces in the presence of dynamically changing refractive index inhomogeneities in the propagation medium. We introduce a TIL propagation model that uses a combination of the parabolic equation describing outgoing wave propagation, and the equation describing evolution of the mutual coherence function (MCF) for the backscattered (returned) wave. The resulting evolution equation for the MCF is further simplified by the use of the smooth refractive index approximation. This approximation enables derivation of the transport equation for the returned wave brightness function, analyzed here using method characteristics (brightness function trajectories). The equations for the brightness function trajectories (ray equations) can be efficiently integrated numerically. We also consider wavefront sensors that perform sensing of speckle-averaged characteristics of the wavefront phase (TIL sensors). Analysis of the wavefront phase reconstructed from Shack-Hartmann TIL sensor measurements shows that an extended target introduces a phase modulation (target-induced phase) that cannot be easily separated from the atmospheric turbulence-related phase aberrations. We also show that wavefront sensing results depend on the extended target shape, surface roughness, and the outgoing beam intensity distribution on the target surface.

Extraction of topographic and material contrasts on surfaces from SEM images obtained by energy filtering detection with low-energy primary electrons.

PubMed

Nagoshi, Masayasu; Aoyama, Tomohiro; Sato, Kaoru

2013-01-01

Secondary electron microscope (SEM) images have been obtained for practical materials using low primary electron energies and an in-lens type annular detector with changing negative bias voltage supplied to a grid placed in front of the detector. The kinetic-energy distribution of the detected electrons was evaluated by the gradient of the bias-energy dependence of the brightness of the images. This is divided into mainly two parts at about 500 V, high and low brightness in the low- and high-energy regions, respectively and shows difference among the surface regions having different composition and topography. The combination of the negative grid bias and the pixel-by-pixel image subtraction provides the band-pass filtered images and extracts the material and topographic information of the specimen surfaces. Copyright © 2012 Elsevier B.V. All rights reserved.

Micromilled optical elements for edge-lit illumination panels

NASA Astrophysics Data System (ADS)

Ronny, Rahima Afrose; Knopf, George K.; Bordatchev, Evgueni; Nikumb, Suwas

2013-04-01

Edge-lit light guide panels (LGPs) with micropatterned surfaces represent a new technology for developing small- and medium-sized illumination sources for application such as automotive, residential lighting, and advertising displays. The shape, density, and spatial distribution of the micro-optical structures (MOSs) imprinted on the transparent LGP must be selected to achieve high brightness and uniform luminance over the active surface. We examine how round-tip cylindrical MOSs fabricated by precision micromilling can be used to create patterned surfaces on low-cost transparent polymethyl-methacrylate substrates for high-intensity illumination applications. The impact of varying the number, pitch, spatial distribution, and depth of the optical microstructures on lighting performance is initially investigated using LightTools™ simulation software. To illustrate the microfabrication process, several 100×100×6 mm3 LGP prototypes are constructed and tested. The prototypes include an "optimized" array of MOSs that exhibit near-uniform illumination (approximately 89%) across its active light-emitting surface. Although the average illumination was 7.3% less than the value predicted from numerical simulation, it demonstrates how LGPs can be created using micromilling operations. Customized MOS arrays with a bright rectangular pattern near the center of the panel and a sequence of MOSs that illuminate a predefined logo are also presented.

Ray craters on Ganymede: Implications for cratering apex-antapex asymmetry and surface modification processes

NASA Astrophysics Data System (ADS)

Xu, Luyuan; Hirata, Naoyuki; Miyamoto, Hideaki

2017-10-01

As the youngest features on Ganymede, ray craters are useful in revealing the sources of recent impactors and surface modification processes on the satellite. We examine craters with D > 10 km on Ganymede from images obtained by the Voyager and Galileo spacecraft to identify ray craters and study their spatial distributions. Furthermore, we carefully select images of appropriate solar and emission angles to obtain unbiased ray crater densities. As a result, we find that the density of large ray craters (D > 25 km) on the bright terrain exhibits an apex-antapex asymmetry, and its degree of asymmetry is much lower than the theoretical estimation for ecliptic comets. For large craters (D > 25 km), ecliptic comets ought to be less important than previously assumed, and a possible explanation is that nearly isotropic comets may play a more important role on Ganymede than previously thought. We also find that small ray craters (10 km < D < 25 km) on the bright terrain and ray craters (D > 10 km) on the dark terrain show no apex-antapex asymmetry. We interpret that the distribution difference between the terrain types comes from preferential thermal sublimation on the dark terrain, while the distribution difference between large and small ray craters suggests that rays of small craters are more readily erased by some surface modification processes, such as micrometeorite gardening.

The effect of precipitation on measuring sea surface salinity from space

NASA Astrophysics Data System (ADS)

Jin, Xuchen; Pan, Delu; He, Xianqiang; Wang, Difeng; Zhu, Qiankun; Gong, Fang

2017-10-01

The sea surface salinity (SSS) can be measured from space by using L-band (1.4 GHz) microwave radiometers. The L-band has been chosen for its sensitivity of brightness temperature to the change of salinity. However, SSS remote sensing is still challenging due to the low sensitivity of brightness temperature to SSS variation: for the vertical polarization, the sensitivity is about 0.4 to 0.8 K/psu with different incident angles and sea surface temperature; for horizontal polarization, the sensitivity is about 0.2 to 0.6 K/psu. It means that we have to make radiometric measurements with accuracy better than 1K even for the best sensitivity of brightness temperature to SSS. Therefore, in order to retrieve SSS, the measured brightness temperature at the top of atmosphere (TOA) needs to be corrected for many sources of error. One main geophysical source of error comes from atmosphere. Currently, the atmospheric effect at L-band is usually corrected by absorption and emission model, which estimate the radiation absorbed and emitted by atmosphere. However, the radiation scattered by precipitation is neglected in absorption and emission models, which might be significant under heavy precipitation. In this paper, a vector radiative transfer model for coupled atmosphere and ocean systems with a rough surface is developed to simulate the brightness temperature at the TOA under different precipitations. The model is based on the adding-doubling method, which includes oceanic emission and reflection, atmospheric absorption and scattering. For the ocean system with a rough surface, an empirical emission model established by Gabarro and the isotropic Cox-Munk wave model considering shadowing effect are used to simulate the emission and reflection of sea surface. For the atmospheric attenuation, it is divided into two parts: For the rain layer, a Marshall-Palmer distribution is used and the scattering properties of the hydrometeors are calculated by Mie theory (the scattering hydrometeors are assumed to be spherical). For the other atmosphere layers, which are assumed to be clear sky, Liebe's millimeter wave propagation model (MPM93) is used to calculate the absorption coefficients of oxygen, water vapor, and cloud droplets. To simulate the change of brightness temperature caused by different rain rate (0-50 mm/h), we assume a 26-layer precipitation structure corresponding to NCEP FNL data. Our radiative transfer simulations showed that the brightness temperature at TOA can be influenced significantly by the heavy precipitation, the results indicate that the atmospheric attenuation of L-band at incidence angle of 42.5° should be a positive bias, and when rain rate rise up to 50 mm/h, the brightness temperature increases are close to 0.6 K and 0.8 K for horizontally and vertically polarized brightness temperature, respectively. Thus, in the case of heavy precipitation, the current absorption and emission model is not accurate enough to correct atmospheric effect, and a radiative transfer model which considers the effect of radiation scattering should be used.

A passive microwave technique for estimating rainfall and vertical structure information from space. Part 1: Algorithm description

NASA Technical Reports Server (NTRS)

Kummerow, Christian; Giglio, Louis

1994-01-01

This paper describes a multichannel physical approach for retrieving rainfall and vertical structure information from satellite-based passive microwave observations. The algorithm makes use of statistical inversion techniques based upon theoretically calculated relations between rainfall rates and brightness temperatures. Potential errors introduced into the theoretical calculations by the unknown vertical distribution of hydrometeors are overcome by explicity accounting for diverse hydrometeor profiles. This is accomplished by allowing for a number of different vertical distributions in the theoretical brightness temperature calculations and requiring consistency between the observed and calculated brightness temperatures. This paper will focus primarily on the theoretical aspects of the retrieval algorithm, which includes a procedure used to account for inhomogeneities of the rainfall within the satellite field of view as well as a detailed description of the algorithm as it is applied over both ocean and land surfaces. The residual error between observed and calculated brightness temperatures is found to be an important quantity in assessing the uniqueness of the solution. It is further found that the residual error is a meaningful quantity that can be used to derive expected accuracies from this retrieval technique. Examples comparing the retrieved results as well as the detailed analysis of the algorithm performance under various circumstances are the subject of a companion paper.

Modeling Illumination Conditions on the Moon: Applications to LRO-LAMP

NASA Astrophysics Data System (ADS)

Byron, B. D.; Mazarico, E. M.; Retherford, K. D.; Mandt, K. E.; Greathouse, T.; Gladstone, R.

2017-12-01

LRO-LAMP is a UV spectrograph which uses illumination from Lyman-α sky glow along with UV light from bright stars to image the dark, permanently shadowed regions (PSRs) of the lunar surface. Accurate modeling of this UV illumination is essential to creating albedo maps of the lunar surface, which can shed light on lunar regolith processes and help to constrain the distribution of water ice in polar PSRs. In this study, the variation in reflected intensity received by the LAMP detector was modeled for South Pole crater Amundsen using the illumination program IllumNG. Amundsen was chosen for study due to the PSR in its Northern side and its highly illuminated equator-facing slopes on the Southern wall. The model works by tracing a ray from each LAMP detector pixel along its boresight until the point where it intersects the lunar surface, and calculating the percentage of the total source flux visible above the horizon. In this study, the three main illumination sources used are the Sun, Interplanetary Lyman-α sky glow, and bright UV starlight in the On Band (130-155 nm) and Off Band (155-190 nm) wavelength ranges. The model also has the capability to calculate incident flux received at the surface, as well as intensity reflected from the surface and received by the LAMP detector along each boresight. The study found a noticeable variation in received intensity between six month stretches for the year of 2010. Over the period of January through July, about 6% more IPM Lyman-α flux was reflected from the surface of Amundsen than for July through December. For stellar flux in the On Band, a 13% difference in flux was reflected between the six month periods. In comparing the monthly intensity maps created by the model with LAMP measured monthly brightness maps, similar crater features are apparent. Though the model brightness is generally higher than the LAMP brightness, after accounting for albedo ( 0.05 for the South Pole region) the values are in closer agreement. In the future, inclusion of the model results during pipeline processing could enable better calibration and analysis of LAMP data.

Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range of 1–2 GHz

DOE PAGES

Rajpurohit, K.; Hoeft, M.; van Weeren, R. J.; ...

2018-01-08

Here, we report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to 1 arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright "brush" of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range –0.70 ≤ α ≤ –0.80. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below 5 μG and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namelymore » $${ \\mathcal M }={3.78}_{-0.2}^{+0.3}$$. The radio halo shows an average spectral index of α = –1.16 ± 0.05 and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightness.« less

Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range of 1–2 GHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajpurohit, K.; Hoeft, M.; van Weeren, R. J.

Here, we report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to 1 arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright "brush" of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range –0.70 ≤ α ≤ –0.80. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below 5 μG and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namelymore » $${ \\mathcal M }={3.78}_{-0.2}^{+0.3}$$. The radio halo shows an average spectral index of α = –1.16 ± 0.05 and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightness.« less

Deep VLA Observations of the Cluster 1RXS J0603.3+4214 in the Frequency Range of 1–2 GHz

NASA Astrophysics Data System (ADS)

Rajpurohit, K.; Hoeft, M.; van Weeren, R. J.; Rudnick, L.; Röttgering, H. J. A.; Forman, W. R.; Brüggen, M.; Croston, J. H.; Andrade-Santos, F.; Dawson, W. A.; Intema, H. T.; Kraft, R. P.; Jones, C.; Jee, M. James

2018-01-01

We report L-band VLA observations of 1RXS J0603.3+4214, a cluster that hosts a bright radio relic, known as the Toothbrush, and an elongated giant radio halo. These new observations allow us to study the surface brightness distribution down to 1 arcsec resolution with very high sensitivity. Our images provide an unprecedented detailed view of the Toothbrush, revealing enigmatic filamentary structures. To study the spectral index distribution, we complement our analysis with published LOFAR and GMRT observations. The bright “brush” of the Toothbrush shows a prominent narrow ridge to its north with a sharp outer edge. The spectral index at the ridge is in the range ‑0.70 ≤ α ≤ ‑0.80. We suggest that the ridge is caused by projection along the line of sight. With a simple toy model for the smallest region of the ridge, we conclude that the magnetic field is below 5 μG and varies significantly across the shock front. Our model indicates that the actual Mach number is higher than that obtained from the injection index and agrees well with the one derived from the overall spectrum, namely { M }={3.78}-0.2+0.3. The radio halo shows an average spectral index of α = ‑1.16 ± 0.05 and a slight gradient from north to south. The southernmost part of the halo is steeper and possibly related to a shock front. Excluding the southernmost part, the halo morphology agrees very well with the X-ray morphology. A power-law correlation is found between the radio and X-ray surface brightness.

2D modelling of the light distribution of early-type galaxies in a volume-limited sample - II. Results for real galaxies

NASA Astrophysics Data System (ADS)

D'Onofrio, M.

2001-10-01

In this paper we analyse the results of the two-dimensional (2D) fit of the light distribution of 73 early-type galaxies belonging to the Virgo and Fornax clusters, a sample volume- and magnitude-limited down to MB=-17.3, and highly homogeneous. In our previous paper (Paper I) we have presented the adopted 2D models of the surface-brightness distribution - namely the r1/n and (r1/n+exp) models - we have discussed the main sources of error affecting the structural parameters, and we have tested the ability of the chosen minimization algorithm (MINUIT) in determining the fitting parameters using a sample of artificial galaxies. We show that, with the exception of 11 low-luminosity E galaxies, the best fit of the real galaxy sample is always achieved with the two-component (r1/n+exp) model. The improvement in the χ2 due to the addition of the exponential component is found to be statistically significant. The best fit is obtained with the exponent n of the generalized r1/n Sersic law different from the classical de Vaucouleurs value of 4. Nearly 42 per cent of the sample have n<2, suggesting the presence of exponential `bulges' also in early-type galaxies. 20 luminous E galaxies are fitted by the two-component model, with a small central exponential structure (`disc') and an outer big spheroid with n>4. We believe that this is probably due to their resolved core. The resulting scalelengths Rh and Re of each component peak approximately at ~1 and ~2kpc, respectively, although with different variances in their distributions. The ratio Re/Rh peaks at ~0.5, a value typical for normal lenticular galaxies. The first component, represented by the r1/n law, is probably made of two distinct families, `ordinary' and `bright', on the basis of their distribution in the μe-log(Re) plane, a result already suggested by Capaccioli, Caon and D'Onofrio. The bulges of spirals and S0 galaxies belong to the `ordinary' family, while the large spheroids of luminous E galaxies form the `bright' family. The second component, represented by the exponential law, also shows a wide distribution in the μ0c-log(Rh) plane. Small discs (or cores) have short scalelengths and high central surface brightness, while normal lenticulars and spiral galaxies generally have scalelengths higher than 0.5kpc and central surface brightness brighter than 20magarcsec-2 (in the B band). The scalelengths Re and Rh of the `bulge' and `disc' components are probably correlated, indicating that a self-regulating mechanism of galaxy formation may be at work. Alternatively, two regions of the Re-Rh plane are avoided by galaxies due to dynamical instability effects. The bulge-to-disc (B/D) ratio seems to vary uniformly along the Hubble sequence, going from late-type spirals to E galaxies. At the end of the sequence the ratio between the large spheroidal component and the small inner core can reach B/D~100.

Posterior uncertainty of GEOS-5 L-band radiative transfer model parameters and brightness temperatures after calibration with SMOS observations

NASA Astrophysics Data System (ADS)

De Lannoy, G. J.; Reichle, R. H.; Vrugt, J. A.

2012-12-01

Simulated L-band (1.4 GHz) brightness temperatures are very sensitive to the values of the parameters in the radiative transfer model (RTM). We assess the optimum RTM parameter values and their (posterior) uncertainty in the Goddard Earth Observing System (GEOS-5) land surface model using observations of multi-angular brightness temperature over North America from the Soil Moisture Ocean Salinity (SMOS) mission. Two different parameter estimation methods are being compared: (i) a particle swarm optimization (PSO) approach, and (ii) an MCMC simulation procedure using the differential evolution adaptive Metropolis (DREAM) algorithm. Our results demonstrate that both methods provide similar "optimal" parameter values. Yet, DREAM exhibits better convergence properties, resulting in a reduced spread of the posterior ensemble. The posterior parameter distributions derived with both methods are used for predictive uncertainty estimation of brightness temperature. This presentation will highlight our model-data synthesis framework and summarize our initial findings.

Brightness field distributions of microlens arrays using micro molding.

PubMed

Cheng, Hsin-Chung; Huang, Chiung-Fang; Lin, Yi; Shen, Yung-Kang

2010-12-20

This study describes the brightness field distributions of microlens arrays fabricated by micro injection molding (μIM) and micro injection-compression molding (μICM). The process for fabricating microlens arrays used room-temperature imprint lithography, photoresist reflow, electroforming, μIM, μICM, and optical properties measurement. Analytical results indicate that the brightness field distribution of the molded microlens arrays generated by μICM is better than those made using μIM. Our results further demonstrate that mold temperature is the most important processing parameter for brightness field distribution of molded microlens arrays made by μIM or μICM.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagen, Lea M. Z.; Hagen, Alex; Seibert, Mark

We provide evidence that UGC 1382, long believed to be a passive elliptical galaxy, is actually a giant low surface brightness (GLSB) galaxy that rivals the archetypical GLSB Malin 1 in size. Like other GLSB galaxies, it has two components: a high surface brightness disk galaxy surrounded by an extended low surface brightness (LSB) disk. For UGC 1382, the central component is a lenticular system with an effective radius of 6 kpc. Beyond this, the LSB disk has an effective radius of ∼38 kpc and an extrapolated central surface brightness of ∼26 mag arcsec{sup 2}. Both components have a combinedmore » stellar mass of ∼8 × 10{sup 10} M {sub ⊙}, and are embedded in a massive (10{sup 10} M {sub ⊙}) low-density (<3 M {sub ⊙} pc{sup 2}) HI disk with a radius of 110 kpc, making this one of the largest isolated disk galaxies known. The system resides in a massive dark matter halo of at least 2 × 10{sup 12} M {sub ⊙}. Although possibly part of a small group, its low-density environment likely plays a role in the formation and retention of the giant LSB and HI disks. We model the spectral energy distributions and find that the LSB disk is likely older than the lenticular component. UGC 1382 has UV–optical colors typical of galaxies transitioning through the green valley. Within the LSB disk are spiral arms forming stars at extremely low efficiencies. The gas depletion timescale of ∼10{sup 11} years suggests that UGC 1382 may be a very-long-term resident of the green valley. We find that the formation and evolution of the LSB disk in UGC 1382 is best explained by the accretion of gas-rich LSB dwarf galaxies.« less

Analysis of wave propagation and wavefront sensing in target-in-the-loop beam control systems

NASA Astrophysics Data System (ADS)

Vorontsov, Mikhail A.; Kolosov, Valeri V.

2004-10-01

Target-in-the-loop (TIL) wave propagation geometry represents perhaps the most challenging case for adaptive optics applications that are related with maximization of irradiance power density on extended remotely located surfaces in the presence of dynamically changing refractive index inhomogeneities in the propagation medium. We introduce a TIL propagation model that uses a combination of the parabolic equation describing outgoing wave propagation, and the equation describing evolution of the mutual intensity function (MIF) for the backscattered (returned) wave. The resulting evolution equation for the MIF is further simplified by the use of the smooth refractive index approximation. This approximation enables derivation of the transport equation for the returned wave brightness function, analyzed here using method characteristics (brightness function trajectories). The equations for the brightness function trajectories (ray equations) can be efficiently integrated numerically. We also consider wavefront sensors that perform sensing of speckle-averaged characteristics of the wavefront phase (TIL sensors). Analysis of the wavefront phase reconstructed from Shack-Hartmann TIL sensor measurements shows that an extended target introduces a phase modulation (target-induced phase) that cannot be easily separated from the atmospheric turbulence-related phase aberrations. We also show that wavefront sensing results depend on the extended target shape, surface roughness, and the outgoing beam intensity distribution on the target surface.

Spectral identification of geological units on the surface of Mars related to the presence of silicates from Earth-based near-infrared telescopic charge-coupled device imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinet, P.; Chevrel, S.

1990-08-30

During the September 1988 Mars opposition, the authors obtained new high spatial (100-150 km) and spectral ({Delta}{lambda}/{lambda} = 1%) resolution near-IR telescopic charge-coupled device images of Mars from Pic-du-Midi Observatory. These images allow the association of spectral units with morphologic surface units on Mars, especially within the dark regions which exhibit much greater variability than the bright regions. Mineralogical interpretation of the data leads to a global description of the surface state of alteration consistent with the spatial distribution of bright and dark regions, with the bright regions being more altered than the dark. Within the less altered regions, Fe{supmore » 2+} crystal field absorption bands are detected, indicative of the presence of mafic minerals (Opx, Cpx, O1) in agreement with a likely crustal basaltic composition. The most conspicuous Fe{sup 2+} absorption features are clearly related to the volcanic regions of the Syrtis Major Shield and Hesperia Planum unit. The strongest observed absorptions due to olivine and clinopyroxene are spatially associated with the restricted central caldera complex of Nili-Meroe Paterae (within Syrtis Major) and the Tyrrhena Patera unit (within Hesperia Planum) and indicate an ultramafic composition.« less

ARC-1979-AC79-7003

NASA Image and Video Library

1979-03-04

Europa , the smallest of the Galilean satellites, or Moons , of Jupiter , is seen here as taken by Voyager 1. Range : 2 million km (1.2 million miles) is centered at about the 300 degree Meridian. The bright areas are probably ice deposits, while the dark may be rocky surface or areas of more patchy ice distribution. Most unusual features are systems of linear structures crossing the surface in various directions. Of these, some of which are over 1000 km. long , & 2 or 3 hundred km. wide, may be faults which have disrupted the surface.

Performance of the K+ ion diode in the 2 MV injector for heavy ion fusion

NASA Astrophysics Data System (ADS)

Bieniosek, F. M.; Henestroza, E.; Kwan, J. W.

2002-02-01

Heavy ion beam inertial fusion driver concepts depend on the availability and performance of high-brightness high-current ion sources. Surface ionization sources have relatively low current density but high brightness because of the low temperature of the emitted ions. We have measured the beam profiles at the exit of the injector diode, and compared the measured profiles with EGUN and WARP-3D predictions. Spherical aberrations are significant in this large aspect ratio diode. We discuss the measured and calculated beam size and beam profiles, the effect of aberrations, quality of vacuum, and secondary electron distributions on the beam profile.

Color and chemistry on Triton

NASA Technical Reports Server (NTRS)

Thompson, W. Reid; Sagan, Carl

1990-01-01

The surface of Triton is very bright but shows subtle yellow to peach hues which probably arise from the production of colored organic compounds from CH4 + N2 and other simple species. In order to investigate possible relationships between chemical processes and the observed surface distribution of chromophores, the surface units are classified according to color/albedo properties, the rates of production of organic chromophores by the action of ultraviolet light and high-energy charged particles is estimated, and rates, spectral properties, and expected seasonal redistribution processes are compared to suggest possible origins of the colors seen on Triton's surface.

Characterizing the Small Scale Structure in Clusters of Galaxies

NASA Technical Reports Server (NTRS)

Forman, William R.

2001-01-01

We studied galaxy clusters Abell 119, Abell 754, and Abell 1750, using data from the ASCA and ROSAT satellites. In addition, we completed the paper "Merging Binary Clusters". In this paper we study three prominent bi-modal X-ray clusters: A3528, A1750 and A3395. Since the sub-clusters in these systems have projected separations of 0.93, 1.00 and 0.67 Mpc respectively, we examine their X-ray and optical observations to investigate the dynamics and possible merging of these sub-clusters. Using data taken with ROSAT and ASCA, we analyze the temperature and surface brightness distributions. We also analyze the velocity distributions of the three clusters using new measurements supplemented with previously published data. We examined both the overall cluster properties as well as the two sub-cluster elements in each. These results were then applied to the determination of the overall cluster masses, that demonstrate excellent consistency between the various methods used. While the characteristic parameters of the sub-clusters are typical of isolated objects, our temperature results for the regions between the two sub-clusters clearly confirm the presence of merger activity that is suggested by the surface brightness distributions. These three clusters represent a progression of equal-sized sub-cluster mergers, starting from initial contact to immediately before first core passage.

Simulation of the lunar surface emission and inversion of the lunar regolith thickness using fusion of optical and microwave remote sensing data

NASA Astrophysics Data System (ADS)

Jin, Y.-Q.

begin table htbp begin center begin tabular p 442pt hline A correspondence of the lunar regolith layer thickness to the lunar digital elevation mapping DEM is presented to construct the global distribution of lunar regolith layer thickness Based on some measurements the physical temperature distribution over the lunar surface is proposed Albedo of the lunar nearside at the wavelengths 0 42 0 65 0 75 0 95 mu m from the telescopic observation is employed to construct the spatial distribution of the FeO TiO 2 on the lunar regolith layer A statistic relationship between the DEM and FeO TiO 2 content of the lunar nearside is then extended to construction of FeO TiO 2 content of the lunar farside Thus the dielectric permittivity of global lunar regolith layer can be determined par Based on all theses conditions brightness temperature of the lunar regolith layer in passive microwave remote sensing which is planned for China s Chang-E lunar project is numerically simulated by a parallel layer model using the fluctuation dissipation theorem par Furthermore taking these simulations as observations an inversion method of the lunar regolith layer thickness is developed by using three- or two-channels brightness temperatures When the FeO TiO 2 content is low and the four channels brightness temperatures in Chang-E project are well distinguishable the regolith layer thickness and physical temperature of the underlying lunar rocky media can be inverted by the three-channels approach When the FeO TiO 2 content is so high that the

Coal lithotypes before and after saturation with CO2; insights from micro- and mesoporosity, fluidity, and functional group distribution

USGS Publications Warehouse

Mastalerz, Maria; Drobniak, A.; Walker, R.; Morse, D.

2010-01-01

Four lithotypes, vitrain, bright clarain, clarain, and fusain, were hand-picked from the core of the Pennsylvanian Springfield Coal Member (Petersburg Formation) in Illinois. These lithotypes were analyzed petrographically and for meso- and micropore characteristics, functional group distribution using FTIR techniques, and fluidity. High-pressure CO2 adsorption isotherm analyses of these lithotypes were performed and, subsequently, all samples were reanalyzed in order to investigate the effects of CO2. After the high-pressure adsorption isotherm analysis was conducted and the samples were reanalyzed, there was a decrease in BET surface area for vitrain from 31.5m2/g in the original sample to 28.5m2/g, as determined by low-pressure nitrogen adsorption. Bright clarain and clarain recorded a minimal decrease in BET surface area, whereas for fusain there was an increase from 6.6m2/g to 7.9m2/g. Using low-pressure CO2 adsorption techniques, a small decrease in the quantity of the adsorbed CO2 is recorded for vitrain and bright clarain, no difference is observed for clarain, and there is an increase in the quantity of the adsorbed CO2 for fusain. Comparison of the FTIR spectra before and after CO2 injection for all lithotypes showed no differences with respect to functional group distribution, testifying against chemical nature of CO2 adsorption. Gieseler plastometry shows that: 1) softening temperature is higher for the post-CO2 sample (389.5??C vs. 386??C); 2) solidification temperature is lower for the post-CO2 sample (443.5??C vs. 451??C); and 3) the maximum fluidity is significantly lower for the post-CO2 sample (4 ddpm vs. 14 ddpm). ?? 2010 Elsevier B.V.

Morphologic examination of CD3-CD4(bright) cells in rat liver.

PubMed

Yamamoto, Satoshi; Sato, Yosinobu; Abo, Toru; Hatakeyama, Katsuyosi

2002-01-01

Recently, we found CD3-CD4(bright) cells with comparative specificity for normal rat liver. In the current study, we investigated the type and form of both CD3-CD4(bright) cells and CD3-CD4(dull) cells in the rat liver. The surface phenotype of hepatic mononuclear cells in Lewis rats was identified by using monoclonal antibodies including anti-CD4, anti-CD3, and antimacrophage in conjunction with two- or three-color immunofluorescence analysis. CD3-CD4(bright) cells and CD3-CD4(dull) cells were examined morphologically using May-Giemsa staining and scanning electron microscopy. The distribution of CD3-CD4(bright) cells and CD3-CD4(dull) cells 48 hours after intravenous administration of liposome-encapsulated dichloromethylene diphosphate was also investigated. In comparison to CD3-CD4(dull) cells, CD3-CD4(bright) cells were slightly larger macrophages with abundant cytoplasmic granules, being present with comparative specificity for normal rat liver and showing negligible effects by intravenous liposome-encapsulated dichloromethylene diphosphate administration. These data suggest that in normal young rat liver these CD3-CD4(dull) and CD3-CD4(bright) cells may be dendritic cells and Kupffer cells that shift from the liver to the spleen or vice versa. These cells may also be able to locally proliferate in liver or spleen due to changes in the developing liver.

STS-55 Earth observation of the Timor Sea

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Earth observation taken from Columbia, Orbiter Vehicle (OV) 102, shows the Timor Sea along the south coast of Timor. The sunglint pattern shows a sharp boundary in sea surface temperature, with cooler water along the coast and warmer water offshore. The sunglint brightness reveals water surface roughness with bright indicating smooth water and dark representing rough water. Cooler water is smoother because it acts to stabilize the atmospheric boundary layer, while the warm water acts to destabilize the atmosphere. Another indication of water temperature is the cloud pattern. Advection within the atmosphere as a result of warming at the sea surface forms low-level clouds with the small, popcorn-like appearance seen in upper right corner of the photograph. The cool water, on the other hand, is relatively free of the popcorn-like clouds. The distribution of the clouds indicates that the wind is blowing toward the upper right corner of the photograph. Also note the line of low-level

Evidence for Surface and Subsurface Ice Inside Micro Cold-Traps on Mercury's North Pole

NASA Technical Reports Server (NTRS)

Rubanenko, L.; Mazarico, E.; Neumann, G. A.; Paige, D. A.

2017-01-01

The small obliquity of Mercury causes topographic depressions located near its poles to cast persistent shadows. Many [1, 9, 15] have shown these permanently shadowed regions (PSRs) may trap water ice for geologic time periods inside cold-traps. More recently, direct evidence for the presence of water ice deposits inside craters was remotely sensed in RADAR [5] and visible imagery [3]. Albedo measurements (reflectence at 1064 nm) obtained by the MErcury Space ENviroment GEochemistry and Ranging Laser Altimeter (MLA) found unusually bright and dark areas next to Mercury's north pole [7]. Using a thermal illumination model, Paige et al. [8] found the bright deposits are correlated with surface cold-traps, and the dark deposits are correlated with subsurface cold-traps. They suggested these anomalous deposits were brought to the surface by comets and were processed by the magnetospheric radiation flux, removing hydrogen and mixing C-N-O-S atoms to form a variety of molecules which will darken with time. Here we use a thermal illumination model to find the link between the cold-trap area fraction of a rough surface and its albedo. Using this link and the measurements obtained by MESSENGER we derive a surface and a subsurface ice distribution map on Mercury's north pole below the MESSENGER spatial resolution, approximately 500 m. We find a large fraction of the polar ice on Mercury resides inside micro cold-traps (of scales 10 - 100 m) distributed along the inter-crater terrain.

Optical properties of the Martian aerosols as derived from Imager for Mars Pathfinder midday sky brightness data

NASA Astrophysics Data System (ADS)

Shalygina, O. S.; Markiewicz, W. J.; Hviid, S. F.

2012-09-01

It is well known that the aerosol play a major role in the energy budget of the Martian atmosphere. The importance of the aerosols for the radiative loading of the atmosphere has hence, direct impact on the Martian present weather and its seasonal cycle as well as consequences for its long term climate. Very accurate models of the sky brightness are required to separate the atmospheric illumination from the spectrum of the Martian surface, and hence to understand the mineralogy of the surface rocks and soil. Such accurate models are only possible if the optical properties of the Martian aerosols are known. In this work we analyze the images of the brightness of the Martian sky at midday acquired from the surface of the Mars during the Mars Pathfinder mission. The Imager for Mars Pathfinder (IMP) obtained data in filters centered at 443.6, 481.0, 670.8, 896.1 and 965.3 nm. Useful data sets were returned on sols 27, 40, 56, 65, 68, 74 and 82. Although the coverage in scattering angles of this sequence is limited to about 100°, having the Sun near zenith minimizes multiple scattering. This property should help in accuracy of constraining the size distribution and material properties. The shape of the particles can be expected to be less well constrained, as scattering events at angles around 150° are only present through multiple scattering. Data from sol 56 (Figure 1) were fitted with multiple scattering radiative transfer calculations to extract the size distribution, optical properties, and shape of the aerosols suspended in the atmosphere [1].

An Ultraviolet and Near-Infrared View of NGC 4214: A Starbursting Core Embedded in a Low Surface Brightness Disk

NASA Astrophysics Data System (ADS)

Fanelli, Michael N.; Waller, William W.; Smith, Denise A.; Freedman, Wendy L.; Madore, Barry; Neff, Susan G.; O'Connell, Robert W.; Roberts, Morton S.; Bohlin, Ralph; Smith, Andrew M.; Stecher, Theodore P.

1997-05-01

During the Astro-2 Spacelab mission in 1995 March, the Ultraviolet Imaging Telescope (UIT) obtained far-UV (λ = 1500 Å) imagery of the nearby Sm/Im galaxy NGC 4214. The UIT images have a spatial resolution of ~3" and a limiting surface brightness, μ1500 > 25 mag arcsec-2, permitting detailed investigation of the intensity and spatial distribution of the young, high-mass stellar component. These data provide the first far-UV imagery covering the full spatial extent of NGC 4214. Comparison with a corresponding I-band image reveals the presence of a starbursting core embedded in an extensive low surface brightness disk. In the far-UV (FUV), NGC 4214 is resolved into several components: a luminous, central knot; an inner region (r <~ 2.5 kpc) with ~15 resolved sources embedded in bright, diffuse emission; and a population of fainter knots extending to the edge of the optically defined disk (r ~ 5 kpc). The FUV light, which traces recent massive star formation, is observed to be more centrally concentrated than the I-band light, which traces the global stellar population. The FUV radial light profile is remarkably well represented by an R1/4 law, providing evidence that the centrally concentrated massive star formation in NGC 4214 is the result of an interaction, possibly a tidal encounter, with a dwarf companion(s). The brightest FUV source produces ~8% of the global FUV luminosity. This unresolved source, corresponding to the Wolf-Rayet knot described by Sargent & Filippenko, is located at the center of the FUV light distribution, giving NGC 4214 an active galactic nucleus-like morphology. Another strong source is present in the I band, located 19" west, 10" north of the central starburst knot, with no FUV counterpart. The I-band source may be the previously unrecognized nucleus of NGC 4214 or an evolved star cluster with an age greater than ~200 Myr. The global star formation rate derived from the total FUV flux is consistent with rates derived using data at other wavelengths and lends support to the scenario of roughly constant star formation during the last few hundred million years at a level significantly enhanced relative to the lifetime averaged star formation rate. The hybrid disk/starburst-irregular morphology evident in NGC 4214 emphasizes the danger of classifying galaxies based on their high surface brightness components at any particular wavelength.

The merger remnant NGC 3610 and its globular cluster system: a large-scale study

NASA Astrophysics Data System (ADS)

Bassino, Lilia P.; Caso, Juan P.

2017-04-01

We present a photometric study of the prototype merger remnant NGC 3610 and its globular cluster (GC) system, based on new Gemini/GMOS and Advanced Camera for Surveys/Hubble Space Telescope archival images. Thanks to the large field of view of our GMOS data, larger than previous studies, we are able to detect a 'classical' bimodal GC colour distribution, corresponding to metal-poor and metal-rich GCs, at intermediate radii and a small subsample of likely young clusters of intermediate colours, mainly located in the outskirts. The extent of the whole GC system is settled as about 40 kpc. The GC population is quite poor, about 500 ± 110 members that corresponds to a low total specific frequency SN ˜ 0.8. The effective radii of a cluster sample are determined, including those of two spectroscopically confirmed young and metal-rich clusters, that are in the limit between GC and UCD sizes and brightness. The large-scale galaxy surface-brightness profile can be decomposed as an inner embedded disc and an outer spheroid, determining for both larger extents than earlier research (10 and 30 kpc, respectively). We detect boxy isophotes, expected in merger remnants, and show a wealth of fine-structure in the surface-brightness distribution with unprecedented detail, coincident with the outer spheroid. The lack of symmetry in the galaxy colour map adds a new piece of evidence to the recent merger scenario of NGC 3610.

Brightness and transparency in the early visual cortex.

PubMed

Salmela, Viljami R; Vanni, Simo

2013-06-24

Several psychophysical studies have shown that transparency can have drastic effects on brightness and lightness. However, the neural processes generating these effects have remained unresolved. Several lines of evidence suggest that the early visual cortex is important for brightness perception. While single cell recordings suggest that surface brightness is represented in the primary visual cortex, the results of functional magnetic resonance imaging (fMRI) studies have been discrepant. In addition, the location of the neural representation of transparency is not yet known. We investigated whether the fMRI responses in areas V1, V2, and V3 correlate with brightness and transparency. To dissociate the blood oxygen level-dependent (BOLD) response to brightness from the response to local border contrast and mean luminance, we used variants of White's brightness illusion, both opaque and transparent, in which luminance increments and decrements cancel each other out. The stimuli consisted of a target surface and a surround. The surround luminance was always sinusoidally modulated at 0.5 Hz to induce brightness modulation to the target. The target luminance was constant or modulated in counterphase to null brightness modulation. The mean signal changes were calculated from the voxels in V1, V2, and V3 corresponding to the retinotopic location of the target surface. The BOLD responses were significantly stronger for modulating brightness than for stimuli with constant brightness. In addition, the responses were stronger for transparent than for opaque stimuli, but there was more individual variation. No interaction between brightness and transparency was found. The results show that the early visual areas V1-V3 are sensitive to surface brightness and transparency and suggest that brightness and transparency are represented separately.

Morphology and Dynamics of Jets of Comet 67P Churyumov-Gerasimenko: Early Phase Development

NASA Astrophysics Data System (ADS)

Lin, Zhong-Yi; Ip, Wing-Huen; Lai, Ian-Lin; Lee, Jui-Chi; Pajola, Maurizio; Lara, Luisa; Gutierrez, Pedro; Rodrigo, Rafael; Bodewits, Dennis; A'Hearn, Mike; Vincent, Jean-Baptiste; Agarwal, Jessica; Keller, Uwe; Mottola, Stefano; Bertini, Ivano; Lowry, Stephen; Rozek, Agata; Liao, Ying; Rosetta Osiris Coi Team

2015-04-01

The scientific camera, OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System), onboard the Rosetta spacecraft comprises a Narrow Angle Camera (NAC) for nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field of dust and gas coma investigations. The dynamical behavior of jets in the dust coma continuously monitored by using dust filters from the arrival at the comet (August 2014) throughout the mapping phase (Oct. 2014) is described here. The analysis will cover the study of the time variability of jets, the source regions of these jets, the excess brightness of jets relative to the averaged coma brightness, and the brightness distribution of dust jets along the projected distance. The jets detected between August and September originated mostly from the neck region (Hapi). Morphological changes appeared over a time scale of several days in September. The brightness slope of the dust jets is much steeper than the background coma. This might be related to the sublimation or fragmentation of the emitted dust grains. Inter-comparison with results from other experiments will be necessary to understand the difference between the dust emitted from Hapi and those from the head and the body of the nucleus surface. The physical properties of the Hapi jets will be compared to dust jets (and their source regions) to emerge as comet 67P moves around the perihelion.

Sizing of single fluorescently stained DNA fragments by scanning microscopy

PubMed Central

Laib, Stephan; Rankl, Michael; Ruckstuhl, Thomas; Seeger, Stefan

2003-01-01

We describe an approach to determine DNA fragment sizes based on the fluorescence detection of single adsorbed fragments on specifically coated glass cover slips. The brightness of single fragments stained with the DNA bisintercalation dye TOTO-1 is determined by scanning the surface with a confocal microscope. The brightness of adsorbed fragments is found to be proportional to the fragment length. The method needs only minute amount of DNA, beyond inexpensive and easily available surface coatings, like poly-l-lysine, 3-aminoproyltriethoxysilane and polyornithine, are utilizable. We performed DNA-sizing of fragment lengths between 2 and 14 kb. Further, we resolved the size distribution before and after an enzymatic restriction digest. At this a separation of buffers or enzymes was unnecessary. DNA sizes were determined within an uncertainty of 7–14%. The proposed method is straightforward and can be applied to standardized microtiter plates. PMID:14602931

Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies AO2, AO3 and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters AO3

NASA Technical Reports Server (NTRS)

White, Raymond E., III

1998-01-01

This final report uses ROSAT observations to analyze two different studies. These studies are: Analysis of Mass Profiles and Cooling Flows of Bright, Early-Type Galaxies; and Surface Brightness Profiles and Energetics of Intracluster Gas in Cool Galaxy Clusters.

IMPACT OF SUPERNOVA AND COSMIC-RAY DRIVING ON THE SURFACE BRIGHTNESS OF THE GALACTIC HALO IN SOFT X-RAYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, Thomas; Girichidis, Philipp; Gatto, Andrea

2015-11-10

The halo of the Milky Way contains a hot plasma with a surface brightness in soft X-rays of the order 10{sup −12} erg cm{sup −2} s{sup −1} deg{sup −2}. The origin of this gas is unclear, but so far numerical models of galactic star formation have failed to reproduce such a large surface brightness by several orders of magnitude. In this paper, we analyze simulations of the turbulent, magnetized, multi-phase interstellar medium including thermal feedback by supernova explosions as well as cosmic-ray feedback. We include a time-dependent chemical network, self-shielding by gas and dust, and self-gravity. Pure thermal feedback alonemore » is sufficient to produce the observed surface brightness, although it is very sensitive to the supernova rate. Cosmic rays suppress this sensitivity and reduce the surface brightness because they drive cooler outflows. Self-gravity has by far the largest effect because it accumulates the diffuse gas in the disk in dense clumps and filaments, so that supernovae exploding in voids can eject a large amount of hot gas into the halo. This can boost the surface brightness by several orders of magnitude. Although our simulations do not reach a steady state, all simulations produce surface brightness values of the same order of magnitude as the observations, with the exact value depending sensitively on the simulation parameters. We conclude that star formation feedback alone is sufficient to explain the origin of the hot halo gas, but measurements of the surface brightness alone do not provide useful diagnostics for the study of galactic star formation.« less

Solar Insolation Effect on the Local Distribution of Lunar Hydroxyl

NASA Astrophysics Data System (ADS)

Kim, Suyeon; Yi, Yu; Hong, Ik-Seon; Sohn, Jongdae

2018-03-01

Moon mineralogy mapper (M3)'s work proved that the moon is not completely dry but has some hydroxyl/water. M3's data confirmed that the amount of hydroxyl on the lunar surface is inversely related to the measured signal brightness, suggesting the lunar surface is sensitive to temperature by solar insolation. We tested the effect of solar insolation on the local distribution of hydroxyl by using M3 data, and we found that most craters had more hydroxyl in shade areas than in sunlit areas. This means that the local distribution of hydroxyl is absolutely influenced by the amount of sunshine. We investigated the factors affecting differences in hydroxyl; we found that the higher the latitude, the larger the difference during daytime. We also measured the pyroxene content and found that pyroxene affects the amount of hydroxyl, but it does not affect the difference in hydroxyl between sunlit and shaded areas. Therefore, we confirmed that solar insolation plays a significant role in the local distribution of hydroxyl, regardless of surface composition.

Comparative study of icy patches on comet nuclei

NASA Astrophysics Data System (ADS)

Oklay, Nilda; Pommerol, Antoine; Barucci, Maria Antonietta; Sunshine, Jessica; Sierks, Holger; Pajola, Maurizio

2016-07-01

Cometary missions Deep Impact, EPOXI and Rosetta investigated the nuclei of comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko respectively. Bright patches were observed on the surfaces of each of these three comets [1-5]. Of these, the surface of 67P is mapped at the highest spatial resolution via narrow angle camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, [6]) on board the Rosetta spacecraft. OSIRIS NAC is equipped with twelve filters covering the wavelength range of 250 nm to 1000 nm. Various filters combinations are used during surface mapping. With high spatial resolution data of comet 67P, three types of bright features were detected on the comet surface: Clustered, isolated and bright boulders [2]. In the visible spectral range, clustered bright features on comet 67P display bluer spectral slopes than the average surface [2, 4] while isolated bright features on comet 67P have flat spectra [4]. Icy patches observed on the surface of comets 9P and 103P display bluer spectral slopes than the average surface [1, 5]. Clustered and isolated bright features are blue in the RGB composites generated by using the images taken in NIR, visible and NUV wavelengths [2, 4]. This is valid for the icy patches observed on comets 9P and 103P [1, 5]. Spectroscopic observations of bright patches on comets 9P and 103P confirmed the existence of water [1, 5]. There were more than a hundred of bright features detected on the northern hemisphere of comet 67P [2]. Analysis of those features from both multispectral data and spectroscopic data is an ongoing work. Water ice is detected in eight of the bright features so far [7]. Additionally, spectroscopic observations of two clustered bright features on the surface of comet 67P revealed the existence of water ice [3]. The spectral properties of one of the icy patches were studied by [4] using OSIRIS NAC images and compared with the spectral properties of the active regions observed on comet 67P. Additionally jets rising from the same clustered bright feature were detected visually [4]. We analyzed bright patches on the surface of comets 9P, 103P and 67P using multispectral data obtained by the high-resolution instrument (HRI), medium- resolution instrument (MRI) and OSIRIS NAC using various spectral analysis techniques. Clustered bright features on comet 67P have similar visible spectra to the bright patches on comets 9P and 103P. The comparison of the bright patches includes the published results of the IR spectra. References: [1] Sunshine et al., 2006, Science, 311, 1453 [2] Pommerol et al., 2015, A&A, 583, A25 [3] Filacchione et al., 2016, Nature, 529, 368-372 [4] Oklay et al., 2016, A&A, 586, A80 [5] Sunshine et al. 2012, ACM [6] Keller et al., 2007, Space Sci. Rev., 128, 433 [7] Barucci et al., 2016, COSPAR, B04

Using Simplistic Shape/Surface Models to Predict Brightness in Estimation Filters

NASA Astrophysics Data System (ADS)

Wetterer, C.; Sheppard, D.; Hunt, B.

The prerequisite for using brightness (radiometric flux intensity) measurements in an estimation filter is to have a measurement function that accurately predicts a space objects brightness for variations in the parameters of interest. These parameters include changes in attitude and articulations of particular components (e.g. solar panel east-west offsets to direct sun-tracking). Typically, shape models and bidirectional reflectance distribution functions are combined to provide this forward light curve modeling capability. To achieve precise orbit predictions with the inclusion of shape/surface dependent forces such as radiation pressure, relatively complex and sophisticated modeling is required. Unfortunately, increasing the complexity of the models makes it difficult to estimate all those parameters simultaneously because changes in light curve features can now be explained by variations in a number of different properties. The classic example of this is the connection between the albedo and the area of a surface. If, however, the desire is to extract information about a single and specific parameter or feature from the light curve, a simple shape/surface model could be used. This paper details an example of this where a complex model is used to create simulated light curves, and then a simple model is used in an estimation filter to extract out a particular feature of interest. In order for this to be successful, however, the simple model must be first constructed using training data where the feature of interest is known or at least known to be constant.

Fusion of Terra-MODIS and Landsat TM data for geothermal sites investigation in Jiangsu Province, China

NASA Astrophysics Data System (ADS)

Chen, Shengbo

2006-01-01

Geothermal resources are generally confined to areas of the Earth's crust where heat flow higher than in surrounding areas heats the water contained in permeable rocks (reservoirs) at depth. It is becoming one of attractive solutions for clean and sustainable energy future for the world. The geothermal fields commonly occurs at the boundaries of plates, and only occasionally in the middle of a plate. The study area, Jiangsu Province, as an example, located in the east of China, is a potential area of geothermal energy. In this study, Landsat thematic Mapper (TM) data were georeferenced to position spatially the geothermal energy in the study area. Multi-spectral infrared data of Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra platform were georeferenced to Landsat TM images. Based on the Wien Displacement Law, these infrared data indicate the surface emitted radiance under the same atmospheric condition, and stand for surface bright temperature respectively. Thus, different surface bright temperature data from Terra-MODIS band 20 or band 31 (R), together with Landsat TM band 4 (G) and band 3 (B) separately, were made up false color composite images (RGB) to generate the distribution maps of surface bright temperatures. Combing with geologic environment and geophysical anomalies, the potential area of geothermal energy with different geo-temperature were mapped respectively. Specially, one geothermal spot in Qinhu Lake Scenery Area in Taizhou city was validated by drilling, and its groundwater temperature is up to some 51°.

Understanding the Physical Structure of the Comet Shoemaker-Levy 9 Fragments

NASA Astrophysics Data System (ADS)

Rettig, Terrence

2000-07-01

Images of the fragmented comet Shoemaker-Levy 9 {SL9} as it approached Jupiter in 1994 provided a unique opportunity to {1} probe the comae, {2} understand the structure of the 20 cometary objects, and {3} provide limits on the Jovian impact parameters. The primary cometary questions were: how were the fragments formed and what was their central structure? There still remains a diversity of opinion regarding the structure of the 21 comet-like fragments as well as the specifics of the disruption event itself. We have shown from Monte Carlo modeling of surface brightness profiles that SL9 fragments had unusual dust size distributions and outflow velocities. Further work of a preliminary nature showed some of the central reflecting area excesses derived from surface brightness profile fitting {w/psf} appeared distributed rather than centrally concentrated as would be expected for comet- like objects, some central excesses were negative and also, the excesses could vary with time. With an improved coma subtraction technique we propose to model each coma surface brightness profile, extract central reflecting areas or central brightness excesses for the non-star-contaminated WFPC-2 SL9, to determine the behavior and characteristics of the central excesses as the fragments approached Jupiter. A second phase of the proposal will be to use numerical techniques {in conjunction with D. Richardson} to investigate the various fragment models. This is a difficult modeling process that will allow us to model the structure and physical characteristics of the fragments and thus constrain parameters for the Jovian impact events. The results will be used to constrain the structure of the central fragment cores of SL9 and how the observed dust comae were produced. The results will provide evidence to discriminate between the parent nucleus models {i.e., were the fragments solid objects or swarms of particles?} and provide better constraints on the atmospheric impact models. The physical characteristics of cometary nuclei are not well understood and the SL9 data provides an important opportunity to constrain these parameters.

Exploring the extremely low surface brightness sky: distances to 23 newly discovered objects in Dragonfly fields

NASA Astrophysics Data System (ADS)

van Dokkum, Pieter

2016-10-01

We are obtaining deep, wide field images of nearby galaxies with the Dragonfly Telephoto Array. This telescope is optimized for low surface brightness imaging, and we are finding many low surface brightness objects in the Dragonfly fields. In Cycle 22 we obtained ACS imaging for 7 galaxies that we had discovered in a Dragonfly image of the galaxy M101. Unexpectedly, the ACS data show that only 3 of the galaxies are members of the M101 group, and the other 4 are very large Ultra Diffuse Galaxies (UDGs) at much greater distance. Building on our Cycle 22 program, here we request ACS imaging for 23 newly discovered low surface brightness objects in four Dragonfly fields centered on the galaxies NGC 1052, NGC 1084, NGC 3384, and NGC 4258. The immediate goals are to construct the satellite luminosity functions in these four fields and to constrain the number density of UDGs that are not in rich clusters. More generally, this complete sample of extremely low surface brightness objects provides the first systematic insight into galaxies whose brightness peaks at >25 mag/arcsec^2.

Radiation properties of two types of luminous textile devices containing plastic optical fibers

NASA Astrophysics Data System (ADS)

Selm, Bärbel; Rothmaier, Markus

2007-05-01

Luminous textiles have the potential to satisfy a need for thin and flexible light diffusers for treatment of intraoral cancerous tissue. Plastic optical fibers (POF) with diameters of 250 microns and smaller are used to make the textiles luminous. Usually light is supplied to the optical fiber at both ends. On the textile surface light emission occurs in a woven structure via damaged straight POFs, whereas the embroidered structure radiates the light out of macroscopically bent POFs. We compared the optical properties of these two types of textile diffusers using red light laser for the embroidery and light emitting diode (LED) for the woven structure as light sources, and found efficiencies for the luminous areas of the two samples of 19 % (woven) and 32 % (embroidery), respectively. It was shown that the efficiency can be greatly improved using an aluminium backing. Additional scattering layers lower the fluence rate by around 30 %. To analyse the homogeneity we took a photo of the illuminated surface using a 3CCD camera and found, for both textiles, a slightly skewed distribution of the dark and bright pixels. The interquartile range of brightness distribution of the embroidery is more than double as the woven structure.

Microwave Brightness Of Land Surfaces From Outer Space

NASA Technical Reports Server (NTRS)

Kerr, Yann H.; Njoku, Eni G.

1991-01-01

Mathematical model approximates microwave radiation emitted by land surfaces traveling to microwave radiometer in outer space. Applied to measurements made by Scanning Multichannel Microwave Radiometer (SMMR). Developed for interpretation of microwave imagery of Earth to obtain distributions of various chemical, physical, and biological characteristics across its surface. Intended primarily for use in mapping moisture content of soil and fraction of Earth covered by vegetation. Advanced Very-High-Resolution Radiometer (AVHRR), provides additional information on vegetative cover, thereby making possible retrieval of soil-moisture values from SMMR measurements. Possible to monitor changes of land surface during intervals of 5 to 10 years, providing significant data for mathematical models of evolution of climate.

Photographer : JPL Europa , the smallest of the Galilean satellites, or Moons , of Jupiter , is seen

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Europa , the smallest of the Galilean satellites, or Moons , of Jupiter , is seen here as taken by Voyager 1. Range : 2 million km (1.2 million miles) is centered at about the 300 degree Meridian. The bright areas are probably ice deposits, while the dark may be rocky surface or areas of more patchy ice distribution. Most unusual features are systems of linear structures crossing the surface in various directions. Of these, some of which are over 1000 km. long , & 2 or 3 hundred km. wide, may be faults which have disrupted the surface.

Stellar Surface Brightness Profiles of Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Herrmann, Kimberly A.; LITTLE THINGS Team

2012-01-01

Radial stellar surface brightness profiles of spiral galaxies can be classified into three types: (I) single exponential, (II) truncated: the light falls off with one exponential out to a break radius and then falls off more steeply, and (III) anti-truncated: the light falls off with one exponential out to a break radius and then falls off less steeply. Stellar surface brightness profile breaks are also found in dwarf disk galaxies, but with an additional category: (FI) flat-inside: the light is roughly constant or increasing and then falls off beyond a break. We have been re-examining the multi-wavelength stellar disk profiles of 141 dwarf galaxies, primarily from Hunter & Elmegreen (2006, 2004). Each dwarf has data in up to 11 wavelength bands: FUV and NUV from GALEX, UBVJHK and H-alpha from ground-based observations, and 3.6 and 4.5 microns from Spitzer. In this talk, I will highlight results from a semi-automatic fitting of this data set, including: (1) statistics of break locations and other properties as a function of wavelength and profile type, (2) color trends and radial mass distribution as a function of profile type, and (3) the relationship of the break radius to the kinematics and density profiles of atomic hydrogen gas in the 41 dwarfs of the LITTLE THINGS subsample. We gratefully acknowledge funding for this research from the National Science Foundation (AST-0707563).

The Barnes-Evans color-surface brightness relation: A preliminary theoretical interpretation

NASA Technical Reports Server (NTRS)

Shipman, H. L.

1980-01-01

Model atmosphere calculations are used to assess whether an empirically derived relation between V-R and surface brightness is independent of a variety of stellar paramters, including surface gravity. This relationship is used in a variety of applications, including the determination of the distances of Cepheid variables using a method based on the Beade-Wesselink method. It is concluded that the use of a main sequence relation between V-R color and surface brightness in determining radii of giant stars is subject to systematic errors that are smaller than 10% in the determination of a radius or distance for temperature cooler than 12,000 K. The error in white dwarf radii determined from a main sequence color surface brightness relation is roughly 10%.

Retrieval and Validation of aerosol optical properties from AHI measurements: impact of surface reflectance assumption

NASA Astrophysics Data System (ADS)

Lim, H.; Choi, M.; Kim, J.; Go, S.; Chan, P.; Kasai, Y.

2017-12-01

This study attempts to retrieve the aerosol optical properties (AOPs) based on the spectral matching method, with using three visible and one near infrared channels (470, 510, 640, 860nm). This method requires the preparation of look-up table (LUT) approach based on the radiative transfer modeling. Cloud detection is one of the most important processes for guaranteed quality of AOPs. Since the AHI has several infrared channels, which are very advantageous for cloud detection, clouds can be removed by using brightness temperature difference (BTD) and spatial variability test. The Yonsei Aerosol Retrieval (YAER) algorithm is basically utilized on a dark surface, therefore a bright surface (e.g., desert, snow) should be removed first. Then we consider the characteristics of the reflectance of land and ocean surface using three visible channels. The known surface reflectivity problem in high latitude area can be solved in this algorithm by selecting appropriate channels through improving tests. On the other hand, we retrieved the AOPs by obtaining the visible surface reflectance using NIR to normalized difference vegetation index short wave infrared (NDVIswir) relationship. ESR tends to underestimate urban and cropland area, we improved the visible surface reflectance considering urban effect. In this version, ocean surface reflectance is using the new cox and munk method which considers ocean bidirectional reflectance distribution function (BRDF). Input of this method has wind speed, chlorophyll, salinity and so on. Based on validation results with the sun-photometer measurement in AErosol Robotic NETwork (AERONET), we confirm that the quality of Aerosol Optical Depth (AOD) from the YAER algorithm is comparable to the product from the Japan Aerospace Exploration Agency (JAXA) retrieval algorithm. Our future update includes a consideration of improvement land surface reflectance by hybrid approach, and non-spherical aerosols. This will improve the quality of YAER algorithm more, particularly retrieval for the dust particle over the bright surface in East Asia.

Analysis of Multi-Scale Radiometric Data Collected during the Cold Land Processes Experiment-1 (CLPX-1)

NASA Technical Reports Server (NTRS)

Tedesco, M.; Kim, E. J.; Gasiewski, A.; Stankov, B.

2005-01-01

Brightness temperature maps at 18.7 and 37 GHz collected at the Fraser and North Park Meso-Scale Areas during the Cold Land Processes Experiment by the NOAA Polarimetric Scanning Radiometer (PSWA) airborne sensor are analyzed. The Fraser site is mostly covered by forest with a typical snowpack depth of 1 m while North Park has no forest cover and is characterized by patches of shallow snow. We examine histograms of the brightness temperatures at 500 m resolution for both the Fraser and North Park areas. The histograms can be modelled by a log-normal distribution in the case of the Fraser MSA and by a bi-modal distribution in the case of the North Park MSA. The histograms of the brightness temperatures at coarser resolutions are also plotted to study the effects of sensor resolution on the shape of the distribution, on the values of the average brightness temperatures and standard deviations. Finally, the values of brightness temperatures obtained by re-sampling (aggregating) the data at 25 km resolution are compared with the values of the brightness temperatures collected by the Advanced Microwave Scanning Radiometer (AMSR-E) and Special Sensor Microwave/Imager (SSMII) satellite radiometers. The results show that in both areas for sensor footprint larger than 5000 m, the brightness temperatures show a flat distribution and the memory of the initial distribution is lost. The values of the brightness temperatures measured by the satellite radiometers are in good agreement with the values obtained averaging the airborne data, even if some discrepancies occur.

Simulating galaxies in the reionization era with FIRE-2: morphologies and sizes

NASA Astrophysics Data System (ADS)

Ma, Xiangcheng; Hopkins, Philip F.; Boylan-Kolchin, Michael; Faucher-Giguère, Claude-André; Quataert, Eliot; Feldmann, Robert; Garrison-Kimmel, Shea; Hayward, Christopher C.; Kereš, Dušan; Wetzel, Andrew

2018-06-01

We study the morphologies and sizes of galaxies at z ≥ 5 using high-resolution cosmological zoom-in simulations from the Feedback In Realistic Environments project. The galaxies show a variety of morphologies, from compact to clumpy to irregular. The simulated galaxies have more extended morphologies and larger sizes when measured using rest-frame optical B-band light than rest-frame UV light; sizes measured from stellar mass surface density are even larger. The UV morphologies are usually dominated by several small, bright young stellar clumps that are not always associated with significant stellar mass. The B-band light traces stellar mass better than the UV, but it can also be biased by the bright clumps. At all redshifts, galaxy size correlates with stellar mass/luminosity with large scatter. The half-light radii range from 0.01 to 0.2 arcsec (0.05-1 kpc physical) at fixed magnitude. At z ≥ 5, the size of galaxies at fixed stellar mass/luminosity evolves as (1 + z)-m, with m ˜ 1-2. For galaxies less massive than M* ˜ 108 M⊙, the ratio of the half-mass radius to the halo virial radius is ˜ 10 per cent and does not evolve significantly at z = 5-10; this ratio is typically 1-5 per cent for more massive galaxies. A galaxy's `observed' size decreases dramatically at shallower surface brightness limits. This effect may account for the extremely small sizes of z ≥ 5 galaxies measured in the Hubble Frontier Fields. We provide predictions for the cumulative light distribution as a function of surface brightness for typical galaxies at z = 6.

Spatio-temporal pattern of eco-environmental parameters in Jharia coalfield, India

NASA Astrophysics Data System (ADS)

Saini, V.; Gupta, R. P.; Arora, M. K.

2015-10-01

Jharia coal-field holds unequivocal importance in the Indian context as it is the only source of prime coking coal in the country. The coalfield is also known for its infamous coal mine fires which have been burning since last more than a century. Haphazard mining over a century has led to eco-environmental changes to a large extent such as changes in vegetation distribution and widespread development of surface and subsurface fires. This article includes the spatiotemporal study of remote sensing derived eco-environmental parameters like vegetation index (NDVI), tasseled cap transformation (TCT) and temperature distribution in fire areas. In order to have an estimate of the temporal variations of NDVI over the years, a study has been carried out on two subsets of the Jharia coalfield using Landsat images of 1972 (MSS), 1992 (TM), 1999 (ETM+) and 2013 (OLI). To assess the changes in brightness and greenness over the year s, difference images have been calculated using the 1992 (TM) and 2013 (OLI) images. Radiance images derived from thermal bands have been used to calculate at-sensor brightness temperature over a 23 year period from 1991 to 2013. It has been observed that during the years 1972 to 2013, moderate to dense vegetation has decreased drastically due to the intense mining going on in the area. TCT images show the areas that have undergone changes in both brightness and greenness from 1992 to 2013. Surface temperature data obtained shows a constant increase from 1991 to 2013 apparently due to coal fires. The utility of remote sensing data in such EIA studies has been emphasized.

Systematic variations in the spectral properties of bright regions on Mars

NASA Technical Reports Server (NTRS)

Murchie, Scott; Mustard, John; Bishop, Janice; Head, James; Pieters, Carle; Erard, Stephane

1992-01-01

The color and albedo of the martian surface define two basic surface units, dark gray material interpreted as relatively unaltered 'rock' and bright reddish material interpreted as weathered 'soil'. Understanding the processes contributing to soil formation first requires assessment of the soil's composition and compositional diversity. We report first results of an investigation of the character and variability of Fe- and water-bearing phases in bright reddish materials using ISM data. We also explore implications of these results for chemical evolution of martian soil. Information on the composition and distribution of bright reddish material comes from three major sources: Viking images, measurements by the XRF and GCMS instruments on the Viking Landers, and spectroscopic data. The XRF experiment found nearly identical, Fe-rich major-element compositions comparable to weathered basalt. Soil water, amounting to approximately 1-3 wt. percent as measured by the GCMS, was liberated mostly by heating to greater than or equal to 350 C, suggesting that it is present in a chemically bound form. Spectroscopic studies have detected ferric oxide, probably hematite, as well as molecular water. However, the identities of major silicate phases have been controversial, with conflicting evidence regarding phyllosilicates. Two main interpretations of this evidence have been proposed: Weathering of basaltic glasses by H2O and CO2 formed a mixture of oxides, salts, and metastable phyllosilicates such as montmorillonite and 'palagonite' formed when basaltic melt contacted ground ice or water. Palagonite is a hydrated basaltic glass containing dispersed ferric oxide, recrystallized in varying degrees to phyllosilicates. Typically it is aphanitic, although some examples contain phenocrysts. In either case, eolian redistribution is thought to have resulted in the material's global homogenization. Imaging spectroscopic data returned by the ISM instrument on Phobos 2 provide a powerful new basis for evaluating the composition and origin of martian soil because they are indicative of the presence and distribution of water- and Fe-bearing phases whose mineralogy is sensitive to the history of chemical weathering.

X-ray versus infrared selection of distant galaxy clusters: A case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-04-01

We present a comparison of two samples of z > 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray selected XMM-LSS distant cluster survey and 92 clusters from the optical-MIR selected SpARCS cluster survey. Both samples are selected from the same approximately 9 square degree sky area and we examine them using common XMM-Newton, Spitzer-SWIRE and CFHT Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: a) X-ray bright, b) X-ray faint, MIR bright, and c) X-ray faint, MIR faint clusters. We determine that X-ray and MIR selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of BCG-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally-concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

THE DISCOVERY OF SEVEN EXTREMELY LOW SURFACE BRIGHTNESS GALAXIES IN THE FIELD OF THE NEARBY SPIRAL GALAXY M101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merritt, Allison; Van Dokkum, Pieter; Abraham, Roberto, E-mail: allison.merritt@yale.edu

2014-06-01

Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of μ {sub g} ∼ 25.5-27.5 magmore » arcsec{sup –2}. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range –11.6 ≲ M{sub V} ≲ –9.3 and their effective radii are 350 pc-1.3 kpc. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (n ∼ 0.3-0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Distance measurements are required to determine whether these galaxies are in fact associated with M101 or are in its foreground or background.« less

Elemental Abundances in the Intracluster Gas and the Hot Galactic Coronae in Cluster A194

NASA Technical Reports Server (NTRS)

Forman, William R.

1997-01-01

We have completed the analysis of observations of the Coma cluster and are continuing analysis of A1367 both of which are shown to be merging clusters. Also, we are analyzing observations of the Centaurus cluster which we see as a merger based in both its temperature and surface brightness distributions. Attachment: Another collision for the coma cluster.

GLOBAL PROPERTIES OF M31'S STELLAR HALO FROM THE SPLASH SURVEY. I. SURFACE BRIGHTNESS PROFILE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, Karoline M.; Guhathakurta, Puragra; Beaton, Rachael L.

2012-11-20

We present the surface brightness profile of M31's stellar halo out to a projected radius of 175 kpc. The surface brightness estimates are based on confirmed samples of M31 red giant branch stars derived from Keck/DEIMOS spectroscopic observations. A set of empirical spectroscopic and photometric M31 membership diagnostics is used to identify and reject foreground and background contaminants. This enables us to trace the stellar halo of M31 to larger projected distances and fainter surface brightnesses than previous photometric studies. The surface brightness profile of M31's halo follows a power law with index -2.2 {+-} 0.2 and extends to amore » projected distance of at least {approx}175 kpc ({approx}2/3 of M31's virial radius), with no evidence of a downward break at large radii. The best-fit elliptical isophotes have b/a = 0.94 with the major axis of the halo aligned along the minor axis of M31's disk, consistent with a prolate halo, although the data are also consistent with M31's halo having spherical symmetry. The fact that tidal debris features are kinematically cold is used to identify substructure in the spectroscopic fields out to projected radii of 90 kpc and investigate the effect of this substructure on the surface brightness profile. The scatter in the surface brightness profile is reduced when kinematically identified tidal debris features in M31 are statistically subtracted; the remaining profile indicates that a comparatively diffuse stellar component to M31's stellar halo exists to large distances. Beyond 90 kpc, kinematically cold tidal debris features cannot be identified due to small number statistics; nevertheless, the significant field-to-field variation in surface brightness beyond 90 kpc suggests that the outermost region of M31's halo is also comprised to a significant degree of stars stripped from accreted objects.« less

KECK/LRIS SPECTROSCOPIC CONFIRMATION OF COMA CLUSTER DWARF GALAXY MEMBERSHIP ASSIGNMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiboucas, Kristin; Tully, R. Brent; Marzke, Ronald O.

2010-11-01

Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of the lowest and highest surface brightness faint (19 < R < 22) dwarf galaxy candidates in the core region of the Coma Cluster. These spectra are used to measure redshifts and establish membership for these faint dwarf populations. The primary goal of the low surface brightness sample is to test our ability to use morphological and surface brightness criteria to distinguish between Coma Cluster members and background galaxies using high resolution Hubble Space Telescope/Advanced Camera for Surveys images. Candidates were rated as expected members, uncertain, or expected background.more » From 93 spectra, 51 dwarf galaxy members and 20 background galaxies are identified. Our morphological membership estimation success rate is {approx}100% for objects expected to be members and better than {approx}90% for galaxies expected to be in the background. We confirm that low surface brightness is a very good indicator of cluster membership. High surface brightness galaxies are almost always background with confusion arising only from the cases of the rare compact elliptical (cE) galaxies. The more problematic cases occur at intermediate surface brightness. Many of these galaxies are given uncertain membership ratings, and these were found to be members about half of the time. Including color information will improve membership determination but will fail for some of the same objects that are already misidentified when using only surface brightness and morphology criteria. cE galaxies with B-V colors {approx}0.2 mag redward of the red sequence in particular require spectroscopic follow up. In a sample of 47 high surface brightness, ultracompact dwarf candidates, 19 objects have redshifts which place them in the Coma Cluster, while another 6 have questionable redshift measurements but may also prove to be members. Redshift measurements are presented and the use of indirect means for establishing cluster membership is discussed.« less

Sulfur "Bergs" and Sulfur Pools: Loki and Tupan Patera on Io

NASA Astrophysics Data System (ADS)

Howell, R. R.; Lopes, R. M.; Landis, C. E.; Allen, D. R.

2012-12-01

Loki and Tupan Patera on Io show numerous features related to the presence of volatiles. There are both striking similarities and distinct differences in the way the volatiles have acted at these two sites. At Loki numerous small bright features, colloquially known as sulfur "bergs", are distributed across the dark patera surface. We map their spatial distribution and spectral properties (Landis et al., this conference) and model sulfur vapor transport processes (Allen et al. this conference) to determine if those bright features are consistent with sulfur fumarole deposits. Alternatively, the "bergs" may represent topographic highs (kipukas) left un-resurfaced by the recurrent activity at Loki. To test this we examine Voyager, Galileo, and New Horizons images to determine if any changes in their spatial distribution have occurred over the 1979 through 2007 period. We also discuss further a statistical analysis of their size and spectral reflectance. Tupan shows an overall morphology similar to Loki, with a central island and one straight margin. It also shows linear features extending across the island. However instead of the dark eastern portion of the patera containing a myriad of small bright features like the Loki "bergs" which avoid the margins, Tupan shows higher albedo deposits concentrated at the margins. And in the higher albedo western portion of Tupan Patera numerous low albedo features can be interpreted as dark silicates erupting or eating through a volatile rich crust. Unlike Loki, these intra-patera features at Tupan clearly have sharply defined edges, indicating surface flow processes rather than possible vapor effects. However both outside the main Tupan Patera walls and on the island there are more diffuse patterns consistent with vapor transport. A detailed comparison of reflectance at violet through very near infrared wavelengths helps elucidate these effects. As also found at Loki, a low violet reflectance indicates that sulfur is abundant on many of the surfaces within the patera. That detailed comparison also helps highlight the vapor effects mentioned above. We discuss the insights into volatile processes gained from a detailed comparison of the Loki and Tupan images, and the implications those have for volcanism on Io.

Global Monitoring of Martian Surface Albedo Changes from Orbital Observations

NASA Astrophysics Data System (ADS)

Geissler, P.; Enga, M.; Mukherjee, P.

2013-12-01

Martian surface changes were first observed from orbit during the Mariner 9 and Viking Orbiter missions. They were found to be caused by eolian processes, produced by deposition of dust during regional and global dust storms and subsequent darkening of the surface through erosion and transportation of dust and sand. The albedo changes accumulated in the 20 years between Viking and Mars Global Surveyor were sufficient to alter the global circulation of winds and the climate of Mars according to model calculations (Fenton et al., Nature 2007), but little was known about the timing or frequency of the changes. Since 1999, we have had the benefit of continuous monitoring by a series of orbiting spacecraft that continues today with Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Express. Daily synoptic observations enable us to determine whether the surface albedo changes are gradual or episodic in nature and to record the seasons that the changes take place. High resolution images of surface morphology and atmospheric phenomena help identify the physical mechanisms responsible for the changes. From these data, we hope to learn the combinations of atmospheric conditions and sediment properties that produce surface changes on Mars and possibly predict when they will take place in the future. Martian surface changes are particularly conspicuous in low albedo terrain, where even a thin layer of bright dust brightens the surface drastically. Equatorial dark areas are repeatedly coated and recoated by dust, which is later shed from the surface by a variety of mechanisms. An example is Syrtis Major, suddenly buried in bright dust by the global dust storm of 2001. Persistent easterly winds blew much of the dust cover away over the course of the next Martian year, but episodic changes continue today, particularly during southern summer when regional dust storms are rife. Another such region is Solis Planum, south of the Valles Marineris, where changes take place relentlessly in all seasons as bright dust and dark sand battle to dominate the landscape. Elsewhere, gradual processes steadily shift albedo boundaries between bright and dark terrain. Dark terrain near the Spirit rover landing site is gradually spreading to the north, driven by seasonal southerly winds. A bright fringe of newly deposited dust appears ahead of the moving boundary, populated by wind streaks and dust avalanches. Dark terrain at higher latitudes gradually creeps towards the equator by the dust cleaning action of dust devils, for example at Nilosytis (43°N, 85°E). Much less obvious is the deposition and erosion of dust on already bright, dust-covered terrain. Changes in the distribution of fresh dust take place frequently in the region surrounding the Tharsis Montes. Dust in this high altitude zone is constantly on the move as faint dark streaks mark the removal of recently deposited dust that is only slightly brighter than the dust already settled on the surface. Dramatic deposition of dust onto dusty terrain took place at much lower elevations in northwestern Amazonis between 2002 and 2005. Since then, the dust has been energetically eroded by towering dust devils that cluster here each summer.

A New Bond Albedo for Performing Orbital Debris Brightness to Size Transformations

NASA Technical Reports Server (NTRS)

Mulrooney, Mark K.; Matney, Mark J.

2008-01-01

We have developed a technique for estimating the intrinsic size distribution of orbital debris objects via optical measurements alone. The process is predicated on the empirically observed power-law size distribution of debris (as indicated by radar RCS measurements) and the log-normal probability distribution of optical albedos as ascertained from phase (Lambertian) and range-corrected telescopic brightness measurements. Since the observed distribution of optical brightness is the product integral of the size distribution of the parent [debris] population with the albedo probability distribution, it is a straightforward matter to transform a given distribution of optical brightness back to a size distribution by the appropriate choice of a single albedo value. This is true because the integration of a powerlaw with a log-normal distribution (Fredholm Integral of the First Kind) yields a Gaussian-blurred power-law distribution with identical power-law exponent. Application of a single albedo to this distribution recovers a simple power-law [in size] which is linearly offset from the original distribution by a constant whose value depends on the choice of the albedo. Significantly, there exists a unique Bond albedo which, when applied to an observed brightness distribution, yields zero offset and therefore recovers the original size distribution. For physically realistic powerlaws of negative slope, the proper choice of albedo recovers the parent size distribution by compensating for the observational bias caused by the large number of small objects that appear anomalously large (bright) - and thereby skew the small population upward by rising above the detection threshold - and the lower number of large objects that appear anomalously small (dim). Based on this comprehensive analysis, a value of 0.13 should be applied to all orbital debris albedo-based brightness-to-size transformations regardless of data source. Its prima fascia genesis, derived and constructed from the current RCS to size conversion methodology (SiBAM Size-Based Estimation Model) and optical data reduction standards, assures consistency in application with the prior canonical value of 0.1. Herein we present the empirical and mathematical arguments for this approach and by example apply it to a comprehensive set of photometric data acquired via NASA's Liquid Mirror Telescopes during the 2000-2001 observing season.

Target-in-the-loop beam control: basic considerations for analysis and wave-front sensing

NASA Astrophysics Data System (ADS)

Vorontsov, Mikhail A.; Kolosov, Valeriy

2005-01-01

Target-in-the-loop (TIL) wave propagation geometry represents perhaps the most challenging case for adaptive optics applications that are related to maximization of irradiance power density on extended remotely located surfaces in the presence of dynamically changing refractive-index inhomogeneities in the propagation medium. We introduce a TIL propagation model that uses a combination of the parabolic equation describing coherent outgoing-wave propagation, and the equation describing evolution of the mutual correlation function (MCF) for the backscattered wave (return wave). The resulting evolution equation for the MCF is further simplified by use of the smooth-refractive-index approximation. This approximation permits derivation of the transport equation for the return-wave brightness function, analyzed here by the method of characteristics (brightness function trajectories). The equations for the brightness function trajectories (ray equations) can be efficiently integrated numerically. We also consider wave-front sensors that perform sensing of speckle-averaged characteristics of the wave-front phase (TIL sensors). Analysis of the wave-front phase reconstructed from Shack-Hartmann TIL sensor measurements shows that an extended target introduces a phase modulation (target-induced phase) that cannot be easily separated from the atmospheric-turbulence-related phase aberrations. We also show that wave-front sensing results depend on the extended target shape, surface roughness, and outgoing-beam intensity distribution on the target surface. For targets with smooth surfaces and nonflat shapes, the target-induced phase can contain aberrations. The presence of target-induced aberrations in the conjugated phase may result in a deterioration of adaptive system performance.

Target-in-the-loop beam control: basic considerations for analysis and wave-front sensing.

PubMed

Vorontsov, Mikhail A; Kolosov, Valeriy

2005-01-01

Target-in-the-loop (TIL) wave propagation geometry represents perhaps the most challenging case for adaptive optics applications that are related to maximization of irradiance power density on extended remotely located surfaces in the presence of dynamically changing refractive-index inhomogeneities in the propagation medium. We introduce a TIL propagation model that uses a combination of the parabolic equation describing coherent outgoing-wave propagation, and the equation describing evolution of the mutual correlation function (MCF) for the backscattered wave (return wave). The resulting evolution equation for the MCF is further simplified by use of the smooth-refractive-index approximation. This approximation permits derivation of the transport equation for the return-wave brightness function, analyzed here by the method of characteristics (brightness function trajectories). The equations for the brightness function trajectories (ray equations) can be efficiently integrated numerically. We also consider wave-front sensors that perform sensing of speckle-averaged characteristics of the wave-front phase (TIL sensors). Analysis of the wave-front phase reconstructed from Shack-Hartmann TIL sensor measurements shows that an extended target introduces a phase modulation (target-induced phase) that cannot be easily separated from the atmospheric-turbulence-related phase aberrations. We also show that wave-front sensing results depend on the extended target shape, surface roughness, and outgoing-beam intensity distribution on the target surface. For targets with smooth surfaces and nonflat shapes, the target-induced phase can contain aberrations. The presence of target-induced aberrations in the conjugated phase may result in a deterioration of adaptive system performance.

The JCMT Transient Survey: Stochastic and Secular Variability of Protostars and Disks In the Submillimeter Region Observed over 18 Months

NASA Astrophysics Data System (ADS)

Johnstone, Doug; Herczeg, Gregory J.; Mairs, Steve; Hatchell, Jennifer; Bower, Geoffrey C.; Kirk, Helen; Lane, James; Bell, Graham S.; Graves, Sarah; Aikawa, Yuri; Chen, Huei-Ru Vivien; Chen, Wen-Ping; Kang, Miju; Kang, Sung-Ju; Lee, Jeong-Eun; Morata, Oscar; Pon, Andy; Scicluna, Peter; Scholz, Aleks; Takahashi, Satoko; Yoo, Hyunju; The JCMT Transient Team

2018-02-01

We analyze results from the first 18 months of monthly submillimeter monitoring of eight star-forming regions in the JCMT Transient Survey. In our search for stochastic variability in 1643 bright peaks, only the previously identified source, EC 53, shows behavior well above the expected measurement uncertainty. Another four sources—two disks and two protostars—show moderately enhanced standard deviations in brightness, as expected for stochastic variables. For the two protostars, this apparent variability is the result of single epochs that are much brighter than the mean. In our search for secular brightness variations that are linear in time, we measure the fractional brightness change per year for 150 bright peaks, 50 of which are protostellar. The ensemble distribution of slopes is well fit by a normal distribution with σ ∼ 0.023. Most sources are not rapidly brightening or fading at submillimeter wavelengths. Comparison against time-randomized realizations shows that the width of the distribution is dominated by the uncertainty in the individual brightness measurements of the sources. A toy model for secular variability reveals that an underlying Gaussian distribution of linear fractional brightness change σ = 0.005 would be unobservable in the present sample, whereas an underlying distribution with σ = 0.02 is ruled out. Five protostellar sources, 10% of the protostellar sample, are found to have robust secular measures deviating from a constant flux. The sensitivity to secular brightness variations will improve significantly with a sample over a longer time duration, with an improvement by factor of two expected by the conclusion of our 36 month survey.

Gravity darkening in late-type stars. I. The Coriolis effect

NASA Astrophysics Data System (ADS)

Raynaud, R.; Rieutord, M.; Petitdemange, L.; Gastine, T.; Putigny, B.

2018-02-01

Context. Recent interferometric data have been used to constrain the brightness distribution at the surface of nearby stars, in particular the so-called gravity darkening that makes fast rotating stars brighter at their poles than at their equator. However, good models of gravity darkening are missing for stars that posses a convective envelope. Aim. In order to better understand how rotation affects the heat transfer in stellar convective envelopes, we focus on the heat flux distribution in latitude at the outer surface of numerical models. Methods: We carry out a systematic parameter study of three-dimensional, direct numerical simulations of anelastic convection in rotating spherical shells. As a first step, we neglect the centrifugal acceleration and retain only the Coriolis force. The fluid instability is driven by a fixed entropy drop between the inner and outer boundaries where stress-free boundary conditions are applied for the velocity field. Restricting our investigations to hydrodynamical models with a thermal Prandtl number fixed to unity, we consider both thick and thin (solar-like) shells, and vary the stratification over three orders of magnitude. We measure the heat transfer efficiency in terms of the Nusselt number, defined as the output luminosity normalised by the conductive state luminosity. Results: We report diverse Nusselt number profiles in latitude, ranging from brighter (usually at the onset of convection) to darker equator and uniform profiles. We find that the variations of the surface brightness are mainly controlled by the surface value of the local Rossby number: when the Coriolis force dominates the dynamics, the heat flux is weakened in the equatorial region by the zonal wind and enhanced at the poles by convective motions inside the tangent cylinder. In the presence of a strong background density stratification however, as expected in real stars, the increase of the local Rossby number in the outer layers leads to uniformisation of the surface heat flux distribution.

Inference of precipitation through thermal infrared measurements of soil moisture

NASA Technical Reports Server (NTRS)

Wetzel, P. J.; Atlas, D.

1981-01-01

The physics of microwave radiative transfer is well understood so that causal models can be assembled which relate the observed brightness temperatures to assumed distributions of hydrometeors (both liquid and ice), non-precipitating clouds, water vapor oxygen, and surface conditions. Present models assume a Marshall Palmer size distribution of liquid hydrometers from the surface to the freezing level (near the 0 C isotherm) and a variable thickness of frozen hydrometeors above that with various reasonable distribution of the other relevant constituents. The validity of such models is discussed. All uncertainties in the rain rate retrieval algorithms can be expressed in terms of specific model uncertainties which can be addressed through appropriate measurements. Those factors which must be known to achieve umambiguous results can be identified so that rainfall measuring algorithms can be developed and improved. The emissivity of the underlying surface significantly affects the contrast that may be measured between areas covered by rain and those which are dry. Sensing strategies for measuring rain over the ocean and rain over land are reviewed.

Hiding in the night sky

NASA Image and Video Library

2016-04-04

This striking NASA/ESA Hubble Space Telescope image captures the galaxy UGC 477, located just over 110 million light-years away in the constellation of Pisces (The Fish). UGC 477 is a low surface brightness (LSB) galaxy. First proposed in 1976 by Mike Disney, the existence of LSB galaxies was confirmed only in 1986 with the discovery of Malin 1. LSB galaxies like UGC 477 are more diffusely distributed than galaxies such as Andromeda and the Milky Way. With surface brightnesses up to 250 times fainter than the night sky, these galaxies can be incredibly difficult to detect. Most of the matter present in LSB galaxies is in the form of hydrogen gas, rather than stars. Unlike the bulges of normal spiral galaxies, the centres of LSB galaxies do not contain large numbers of stars. Astronomers suspect that this is because LSB galaxies are mainly found in regions devoid of other galaxies, and have therefore experienced fewer galactic interactions and mergers capable of triggering high rates of star formation. LSB galaxies such as UGC 477 instead appear to be dominated by dark matter, making them excellent objects to study to further our understanding of this elusive substance. However, due to an underrepresentation in galactic surveys — caused by their characteristic low brightness — their importance has only been realised relatively recently.

Electron Source Brightness and Illumination Semi-Angle Distribution Measurement in a Transmission Electron Microscope.

PubMed

Börrnert, Felix; Renner, Julian; Kaiser, Ute

2018-05-21

The electron source brightness is an important parameter in an electron microscope. Reliable and easy brightness measurement routes are not easily found. A determination method for the illumination semi-angle distribution in transmission electron microscopy is even less well documented. Herein, we report a simple measurement route for both entities and demonstrate it on a state-of-the-art instrument. The reduced axial brightness of the FEI X-FEG with a monochromator was determined to be larger than 108 A/(m2 sr V).

Moon night sky brightness simulation for the Xinglong station

NASA Astrophysics Data System (ADS)

Yao, Song; Zhang, Hao-Tong; Yuan, Hai-Long; Zhao, Yong-Heng; Dong, Yi-Qiao; Bai, Zhong-Rui; Deng, Li-Cai; Lei, Ya-Juan

2013-10-01

Using a sky brightness monitor at the Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences, we collected data from 22 dark clear nights and 90 moon nights. We first measured the sky brightness variation with time for dark nights and found a clear correlation between sky brightness and human activity. Then with a modified sky brightness model of moon nights and data from these nights, we derived the typical value for several important parameters in the model. With these results, we calculated the sky brightness distribution under a given moon condition for the Xinglong station. Furthermore, we simulated the sky brightness distribution of a moon night for a telescope with a 5° field of view (such as LAMOST). These simulations will be helpful for determining the limiting magnitude and exposure time, as well as planning the survey for LAMOST during moon nights.

Xevioso Crater on Ceres

NASA Image and Video Library

2017-09-26

Xevioso Crater is the small (5.3 miles, 8.5 kilometers in diameter) crater associated with bright ejecta toward the top of this image, taken by NASA's Dawn spacecraft. It is one of the newly named craters on Ceres. Xevioso is located in the vicinity of Ahuna Mons, the tall, lonely mountain seen toward the bottom of the picture. Given that the small impact that formed Xevioso was able to excavate bright material, scientists suspect the material may be found at shallow depth. Its nature and relationship to other bright regions on Ceres is under analysis. The asymmetrical distribution of this bright ejecta indicates Xevioso formed via an oblique impact. Another view of Xevioso can be found here. Xevioso is named for the Fon god of thunder and fertility from the Kingdom of Dahomey, which was located in a region that is now the west African country of Benin. Dawn acquired this picture on October 15, 2015, from its high altitude mapping orbit at about 915 miles (1,470 kilometers) above the surface. The center coordinates of this image are 3.8 degrees south latitude, 314 degrees east longitude, and its resolution is 450 feet (140 meters) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21907

Variable features on Mars. II - Mariner 9 global results.

NASA Technical Reports Server (NTRS)

Sagan, C.; Veverka, J.; Fox, P.; Dubisch, F.; French, R.; Gierasch, P.; Quam, L.; Lederberg, J.; Levinthal, E.; Pollack, J. B.

1973-01-01

Systematic Mariner 9 monitoring of the space and time distribution of Martian bright and dark markings, the streaks and splotches, indicates a range of global correlations. The time-variable classical dark markings owe their configurations and variability to their constituent streaks and splotches, produced by windblown dust. Streaks and splotches are consistent wind direction indicators. Correlation of global streak patterns with general circulation models shows that velocities of about 50 to 90 m/sec above the boundary layer are necessary to initiate grain motion on the surface and to produce streaks and splotches. Detailed examples of changes in Syrtis Major, Lunae Palus, and Promethei Sinus are generally consistent with removal of bright sand and dust and uncovering of darker underlying material as the active agent in such changes, although dark mobile material probably also exists on Mars. The generation of streaks and the progressive albedo changes observed require only threshold velocities of about 2 m/sec for about 1 day at the grain surface.

Photometric Modeling and VIS-IR Albedo Maps of Dione From Cassini-VIMS

NASA Astrophysics Data System (ADS)

Filacchione, G.; Ciarniello, M.; D'Aversa, E.; Capaccioni, F.; Cerroni, P.; Buratti, B. J.; Clark, R. N.; Stephan, K.; Plainaki, C.

2018-03-01

We report about visible and infrared albedo maps and spectral indicators of Dione's surface derived from the complete Visual and Infrared Mapping Spectrometer (VIMS) data set acquired between 2004 and 2017 during the Cassini tour in Saturn's system. Maps are derived by applying a photometric correction necessary to disentangle the intrinsic albedo of the surface from illumination and viewing geometry occurring at the time of the observation. The photometric correction is based on the Shkuratov et al. (2011, https://doi.org/10.1016/j.pss.2011.06.011) method which yields values of the surface equigonal albedo. Dione's surface albedo maps are rendered at five visible (VIS: 0.35, 0.44, 0.55, 0.7, and 0.95 μm) and five infrared (IR: 1.046, 1.540, 1.822, 2.050, and 2.200 μm) wavelengths in cylindrical projection with a 0.5° × 0.5° angular resolution in latitude and longitude, corresponding to a spatial resolution of 4.5 km/bin. Apart from visible and infrared albedo maps, we report about the distribution of the two visible spectral slopes (0.35-0.55 and 0.55-0.95 μm) and water ice 2.050 μm band depth computed after having applied the photometric correction. The derived spectral indicators are employed to trace Dione's composition variability on both global and local scales allowing to study the dichotomy between the bright-leading and dark-trailing hemispheres, the distribution of fresh material on the impact craters and surrounding ejecta, and the resurfacing of the bright material within the chasmata caused by tectonism.

Submillimeter wave survey of the galactic plane. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Cheung, L. H.

1980-01-01

The survey measured, over virtually the entire galactic plane, the distribution and basic physical conditions of the coolest dust component of the interstellar medium. The instrument designed for observations of extended, low surface brightness continuum emission consisted of a balloon borne, gyro stablized, 1.2 m Cassegrain telescope and a liquid cooled photometer. The design, integration, tests, and flight operation of the survey are presented.

A photometric analysis of Abell 1689: two-dimensional multistructure decomposition, morphological classification and the Fundamental Plane

NASA Astrophysics Data System (ADS)

Dalla Bontà, E.; Davies, R. L.; Houghton, R. C. W.; D'Eugenio, F.; Méndez-Abreu, J.

2018-02-01

We present a photometric analysis of 65 galaxies in the rich cluster Abell 1689 at z = 0.183, using the Hubble Space Telescope Advanced Camera for Surveys archive images in the rest-frame V band. We perform two-dimensional multicomponent photometric decomposition of each galaxy adopting different models of the surface-brightness distribution. We present an accurate morphological classification for each of the sample galaxies. For 50 early-type galaxies, we fit both a de Vaucouleurs law and a Sérsic law; S0s are modelled by also including a disc component described by an exponential law. Bars of SB0s are described by the profile of a Ferrers ellipsoid. For the 15 spirals, we model a Sérsic bulge, exponential disc and, when required, a Ferrers bar component. We derive the Fundamental Plane (FP) by fitting 40 early-type galaxies in the sample, using different surface-brightness distributions. We find that the tightest plane is that derived by Sérsic bulges. We find that bulges of spirals lie on the same relation. The FP is better defined by the bulges alone rather than the entire galaxies. Comparison with local samples shows both an offset and rotation in the FP of Abell 1689.

Erratum - the Lowest Surface Brightness Disc Galaxy Known

NASA Astrophysics Data System (ADS)

Davies, J. I.; Phillipps, S.; Disney, M. J.

1988-11-01

The paper "The lowest surface brightness disc galaxy known' by J.I. Davies, S. Phillipps and M.J. Disney was published in Mon. Not. R. astr. Soc. (1988), 231, 69p. The declination of the object given in section 2 of the paper is incorrect and should be changed to +19^deg^48'23". Thus the object cannot be identified with GP 1444 as in the original paper. To minimize confusion we propose to refer to the low surface brightness galaxy as GP 1444A.

Globular clusters as tracers of stellar bimodality in elliptical galaxies: the case of NGC 1399

NASA Astrophysics Data System (ADS)

Forte, Juan C.; Faifer, Favio; Geisler, Doug

2005-02-01

Globular cluster systems (GCSs) frequently show a bimodal distribution of cluster integrated colours. This work explores the arguments to support the idea that the same feature is shared by the diffuse stellar population of the galaxy they are associated with. The particular case of NGC 1399, one of the dominant central galaxies in the Fornax cluster, for which a new B surface brightness profile and (B-RKC) colours are presented, is discussed taking advantage of a recently published wide-field study of its GCS. The results show that the galaxy brightness profile and colour gradient, as well as the behaviour of the cumulative globular cluster specific frequency, are compatible with the presence of two dominant stellar populations, associated with the so-called `blue' and `red' globular cluster families. These globular families are characterized by different intrinsic specific frequencies (defined in terms of each stellar population): Sn= 3.3 +/- 0.3 in the case of the red globulars and Sn= 14.3 +/- 2.5 for the blue ones. We stress that this result does not necessarily conflict with recent works that point out a clear difference between the metallicity distribution of (resolved) halo stars and globulars when comparing their number statistics. The region within 0.5arcmin of the centre shows a deviation from the model profile (in both surface brightness and colour) that may be explained in terms of the presence of a bulge-like high-metallicity component. Otherwise, the model gives an excellent fit up to 12arcmin (or 66.5Kpc) from the centre, the galactocentric limit of our blue brightness profile. The inferred specific frequencies imply that, in terms of their associated stellar populations, the formation of the blue globulars took place with an efficiency about six times higher than that corresponding to their red counterparts. The similarity of the spatial distribution of the blue globulars with that inferred for dark matter, as well as with that of the X-ray-emitting hot gas associated with NGC 1399, is emphasized. The impact of a relatively inconspicuous low-metallicity population, that shares the properties of the blue globulars, as a possible source of chemical enrichment early in the formation history of the galaxy is also briefly discussed.

Iapetus: Major discoveries from the Cassini imaging experiment

NASA Astrophysics Data System (ADS)

Denk, T.; Neukum, G.; Schmedemann, N.; Roatsch, Th.; Thomas, P. C.; Helfenstein, P.; Turtle, E. P.; Porco, C. C.

2008-09-01

Over the course of more than three years orbiting Saturn, the Imaging Subsystem (ISS) [1] of the Cassini spacecraft has acquired high-resolution images of the Saturnian moon Iapetus during a number of flybys. The most recent and only targeted Iapetus flyby occured on 10 September 2007, and allowed a >50x closer look at the surface than any previous observation. The surface of Iapetus is heavily cratered down to the resolution limit of ~10 meters per pixel. The crater size-frequency distribution shows no measurable difference between the leading and the trailing hemisphere, arguing for planetocentric projectiles as the main impactor source. The equatorial ridge can now be clearly tracked along half of Iapetus's circumference, from ~50°W to ~245°W; it is mainly absent on the other hemisphere. However, we argue that it presumably spanned the full globe shortly after formation. Very small bright-ray and bright-rim craters have been detected deep within the dark hemisphere, suggestive for a dark blanket with a thickness in the order of decimeters to meters only. On the trailing side at low and mid-latitudes, very dark terrain is located immediately adjacent to bright terrain, with almost no gray shading in between. In many cases, crater walls facing towards the equator are dark, while poleward-facing walls and slopes are bright. This effect vanishes at both north and south high latitudes. We interpret these observations to indicate that thermal segregation of water ice is responsible for these complex small-scale dark-bright patterns. On the trailing side, a bright polar cap has been observed at high latitudes on both hemispheres (north and south). A global color dichotomy has been detected in addition to the long-known global brightness dichotomy, with the leading side showing a significantly redder color than the trailing side. Unlike the more ellipsoidal-shaped brightness dichotomy, the color dichotomy is quite well separated into two different hemispheres, with the sub-Saturn (~0°W) and anti-Saturn (~180°W) meridians as the approximate boundaries [2]. This global pattern indicates an exogenic origin. Earlier hypotheses for the origin of the brightness dichotomy, like the infall of dust from retrograde outer moons, might actually offer a better explanation for the color dichotomy than for the brightness dichotomy. We propose that this so far unknown process forming the color dichotomy has also reddened and somewhat darkened Hyperion, another moon of Saturn. The color dichotomy also provides a key element to the explanation of the brightness dichotomy in the model of Spencer et al. [3]. References [1] Porco, C.C. et al. (2004) Space Sci. Rev.115, 363. [2] Denk, T. et al. (2006) EGU06-A-08352. [3] Spencer, J.R. et al. (2005) 37th DPS, abstract 39.08.

Cassini ISS observations of Iapetus: Results from the primary mission

NASA Astrophysics Data System (ADS)

Denk, Tilmann; Schmedemann, Nico; Wagner, Roland; Giese, Bernd; Perry, Jason; Helfenstein, Paul; Turtle, Elizabeth; Neukum, Gerhard; Roatsch, Thomas; Porco, Carolyn

Cassini ISS images obtained over the past 4 years in orbit around Saturn provide new insights about the surface features, properties, processes and history of Iapetus, the outermost regular Saturnian moon. Particularly valuable are the non-targeted flyby on New-Year's Eve 2005 with a good view on the leading side, and the targeted flyby in September 2007 where especially the trailing side was seen in particularly fine detail. There are many questions about Iapetus to which imaging might contribute solutions: What is the reason for the unique global brightness dichotomy that has already been discovered in 1672 by G.D. Cassini? How is the global color dichotomy, which was detected by the Cassini spacecraft, related to the brightness dichotomy? How did the (also unique) equatorial ridge form, and what is its detailed morphology? What is the distribution of the craters and large basins on the surface, and how old is the surface? What geologic processes (besides cratering) took place on Iapetus? Why is there a very distinct patchy segregation of dark and bright material at local scales? What is the thickness of the dark blanket? Why are there no large bright craters within the dark hemisphere? What is the time scale for a fresh bright crater in the dark terrain to fade back to the darkness of the surrounding terrain? Attempts to answer these questions will be given in the presentation. Selected references: Buratti B.J. et al. (2002) Icarus 155, 375-381, doi:10.1006/icar.2001.6730. Castillo-Rogez J.C. et al. (2007) Icarus 190, 179-202, doi:10.1016/j.icarus.2007.02.018. Denk T. et al. (2006) EGU, abstract EGU06-A-08352. Denk T. et al. (2008) LPSC XXXIX, abstract #2533. Giese B. et al. (2008) Icarus 193, 359-371, doi:10.1016/j.icarus.2007.06.005. Porco C.C. et al. (2005) Science 307, 1243-1247. Schmedemann N. et al. (2008) LPSC XXXIX, abstract #2070. Spencer J.R. et al. (2005) 37th DPS, abstract 39.08.

Three-dimensional radiative transfer models of clumpy tori in Seyfert galaxies

NASA Astrophysics Data System (ADS)

Schartmann, M.; Meisenheimer, K.; Camenzind, M.; Wolf, S.; Tristram, K. R. W.; Henning, T.

2008-04-01

Context: Tori of Active Galactic Nuclei (AGN) are made up of a mixture of hot and cold gas, as well as dust. In order to protect the dust grains from destruction by the surrounding hot gas as well as by the energetic (UV/optical) radiation from the accretion disk, the dust is often assumed to be distributed in clouds. Aims: A new three-dimensional model of AGN dust tori is extensively investigated. The torus is modelled as a wedge-shaped disk within which dusty clouds are randomly distributed throughout the volume, by taking the dust density distribution of the corresponding continuous model into account. We especially concentrate on the differences between clumpy and continuous models in terms of the temperature distributions, the surface brightness distributions and interferometric visibilities, as well as spectral energy distributions. Methods: Radiative transfer calculations with the help of the three-dimensional Monte Carlo radiative transfer code MC3D are used in order to simulate spectral energy distributions as well as surface brightness distributions at various wavelengths. In a second step, interferometric visibilities for various inclination as well as position angles and baselines are calculated, which can be used to directly compare our models to interferometric observations with the MIDI instrument. Results: We find that the radial temperature distributions of clumpy models possess significantly enhanced scatter compared to the continuous cases. Even at large distances, clouds can be heated directly by the central accretion disk. The existence of the silicate 10 μm-feature in absorption or in emission depends sensitively on the distribution, the size and optical depth of clouds in the innermost part of the dust distribution. With this explanation, failure and success of previous modelling efforts of clumpy tori can be understood. The main reason for this outcome are shadowing effects of clouds within the central region. We underline this result with the help of several parameter variations. After adapting the parameters of our clumpy standard model to the circumstances of the Seyfert 2 Circinus galaxy, it can qualitatively explain recent mid-infrared interferometric observations performed with MIDI, as well as high resolution spectral data.

Titan's surface from the Cassini RADAR radiometry data during SAR mode

USGS Publications Warehouse

Paganelli, F.; Janssen, M.A.; Lopes, R.M.; Stofan, E.; Wall, S.D.; Lorenz, R.D.; Lunine, J.I.; Kirk, R.L.; Roth, L.; Elachi, C.

2008-01-01

We present initial results on the calibration and interpretation of the high-resolution radiometry data acquired during the Synthetic Aperture Radar (SAR) mode (SAR-radiometry) of the Cassini Radar Mapper during its first five flybys of Saturn's moon Titan. We construct maps of the brightness temperature at the 2-cm wavelength coincident with SAR swath imaging. A preliminary radiometry calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, outlining signatures that characterize various terrains and surface features. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007.

High contrast imaging through adaptive transmittance control in the focal plane

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake

2016-05-01

High contrast imaging, in the presence of a bright background, is a challenging problem encountered in diverse applications ranging from the daily chore of driving into a sun-drenched scene to in vivo use of biomedical imaging in various types of keyhole surgeries. Imaging in the presence of bright sources saturates the vision system, resulting in loss of scene fidelity, corresponding to low image contrast and reduced resolution. The problem is exacerbated in retro-reflective imaging systems where the light sources illuminating the object are unavoidably strong, typically masking the object features. This manuscript presents a novel theoretical framework, based on nonlinear analysis and adaptive focal plane transmittance, to selectively remove object domain sources of background light from the image plane, resulting in local and global increases in image contrast. The background signal can either be of a global specular nature, giving rise to parallel illumination from the entire object surface or can be represented by a mosaic of randomly orientated, small specular surfaces. The latter is more representative of real world practical imaging systems. Thus, the background signal comprises of groups of oblique rays corresponding to distributions of the mosaic surfaces. Through the imaging system, light from group of like surfaces, converges to a localized spot in the focal plane of the lens and then diverges to cast a localized bright spot in the image plane. Thus, transmittance of a spatial light modulator, positioned in the focal plane, can be adaptively controlled to block a particular source of background light. Consequently, the image plane intensity is entirely due to the object features. Experimental image data is presented to verify the efficacy of the methodology.

FC colour images of dwarf planet Ceres reveal a complicated geological history

NASA Astrophysics Data System (ADS)

Nathues, A.; Hoffmann, M.; Platz, T.; Thangjam, G. S.; Cloutis, E. A.; Reddy, V.; Le Corre, L.; Li, J.-Y.; Mengel, K.; Rivkin, A.; Applin, D. M.; Schaefer, M.; Christensen, U.; Sierks, H.; Ripken, J.; Schmidt, B. E.; Hiesinger, H.; Sykes, M. V.; Sizemore, H. G.; Preusker, F.; Russell, C. T.

2016-12-01

The dwarf planet Ceres (equatorial diameter 963km) is the largest object that has remained in the main asteroid belt (Russell and Raymond, 2012), while most large bodies have been destroyed or removed by dynamical processes (Petit et al. 2001; Minton and Malhotra, 2009). Pre-Dawn investigations (McCord and Sotin, 2005; Castillo-Rogez and McCord, 2010; Castillo-Rogez et al., 2011) suggest that Ceres is a thermally evolved, but still volatile-rich body with potential geological activity, that was never completely molten, but possibly differentiated into a rocky core, an ice-rich mantle, and may contain remnant internal liquid water. Thermal alteration should contribute to producing a (dark) carbonaceous chondritic-like surface (McCord and Sotin, 2005; Castillo-Rogez and McCord, 2010; Castillo-Rogez et al., 2011; Nathues et al., 2015) containing ammoniated phyllosilicates (King et al., 1992; De Sanctis et al., 2015 and 2016). Here we show and analyse global contrast-rich colour mosaics, derived from a camera on-board Dawn at Ceres (Russell et al., 2016). Colours are unexpectedly more diverse on global scale than anticipated by Hubble Space Telescope (Li et al., 2006) and ground-based observations (Reddy et al. 2015). Dawn data led to the identification of five major colour units. The youngest units identified by crater counting, termed bright and bluish units, are exclusively found at equatorial and intermediate latitudes. We identified correlations between the distribution of the colour units, crater size, and formation age, inferring a crustal stratigraphy. Surface brightness and spectral properties are not correlated. The youngest surface features are the bright spots at crater Occator ( Ø 92km). Their colour spectra are highly consistent with the presence of carbonates while most of the remaining surface resembles modifications of various types of ordinary carbonaceous chondrites.

Iapetus Surface Temperatures, and the Influence of Sublimation on the Albedo Dichotomy: Cassini CIRS Constraints

NASA Astrophysics Data System (ADS)

Spencer, J. R.; Pearl, J. C.; Segura, M.; Cassini CIRS Team

2005-08-01

The Composite Infrared Spectrometer (CIRS) on the Cassini orbiter obtained extensive observations of Iapetus' thermal emission during the New Year 2005 flyby, with best 8 - 16 μ m spatial resolution of 35 km per pixel. Observed subsolar temperatures on the dark terrain reach nearly 130 K, much warmer than any other satellite surface in the Saturn system, due to the combination of low albedo and slow rotation. These high temperatures mean that, uniquely in the Saturn system, water ice sublimation rates are significant at low latitudes on Iapetus' dark side, and surface water ice is probably not stable there on geological timescales. This result is consistent with the lack of water ice at low latitudes on the dark terrain inferred from Cassini UVIS UV spectra (Hendrix et al., 2005 LPSC). Thermally-controlled migration of water ice may thus contribute to the curious shape of the light/dark boundary on Iapetus, with bright poles and dark terrain extending round the equator onto the trailing side. Impacts of Saturn-centric or prograde heliocentric material cannot alone explain this shape, as their impact flux depends only on distance from the apex of motion (though the impact distribution of Oort cloud comet dust may be consistent with the observed albedo pattern (Cook and Franklin 1970)). We model the ballistic migration of water ice across the surface of Iapetus, determining temperatures and sublimation rates assuming CIRS-constrained thermal inertia and a simple dependence of albedo on distance from the apex of motion. Water ice is lost rapidly from low latitudes on the dark leading side and accumulates near the poles, and is also lost, though more slowly, in equatorial regions near the sub-Saturn and anti-Saturn points. The resulting water ice distribution pattern matches the distribution of Iapetus' bright terrain remarkably well. Albedo modification by thermal migration can thus help to reconcile Iapetus' albedo patterns with albedo control by Saturn-centric or prograde heliocentric impactors.

Planetary science: A 5-micron-bright spot on Titan: Evidence for surface diversity

USGS Publications Warehouse

Barnes, J.W.; Brown, R.H.; Turtle, E.P.; McEwen, A.S.; Lorenz, R.D.; Janssen, M.; Schaller, E.L.; Brown, M.E.; Buratti, B.J.; Sotin, Christophe; Griffith, C.; Clark, R.; Perry, J.; Fussner, S.; Barbara, J.; West, R.; Elachi, C.; Bouchez, A.H.; Roe, H.G.; Baines, K.H.; Bellucci, G.; Bibring, J.-P.; Capaccioni, F.; Cerroni, P.; Combes, M.; Coradini, A.; Cruikshank, D.P.; Drossart, P.; Formisano, V.; Jaumann, R.; Langevin, Y.; Matson, D.L.; McCord, T.B.; Nicholson, P.D.; Sicardy, B.

2005-01-01

Observations from the Cassini Visual and Infrared Mapping Spectrometer show an anomalously bright spot on Titan located at 80??W and 20??S. This area is bright in reflected tight at all observed wavelengths, but is most noticeable at 5 microns. The spot is associated with a surface albedo feature identified in images taken by the Cassini Imaging Science Subsystem. We discuss various hypotheses about the source of the spot, reaching the conclusion that the spot is probably due to variation in surface composition, perhaps associated with recent geophysical phenomena.

A 5-micron-bright spot on Titan: evidence for surface diversity.

PubMed

Barnes, Jason W; Brown, Robert H; Turtle, Elizabeth P; McEwen, Alfred S; Lorenz, Ralph D; Janssen, Michael; Schaller, Emily L; Brown, Michael E; Buratti, Bonnie J; Sotin, Christophe; Griffith, Caitlin; Clark, Roger; Perry, Jason; Fussner, Stephanie; Barbara, John; West, Richard; Elachi, Charles; Bouchez, Antonin H; Roe, Henry G; Baines, Kevin H; Bellucci, Giancarlo; Bibring, Jean-Pierre; Capaccioni, Fabrizio; Cerroni, Priscilla; Combes, Michel; Coradini, Angioletta; Cruikshank, Dale P; Drossart, Pierre; Formisano, Vittorio; Jaumann, Ralf; Langevin, Yves; Matson, Dennis L; McCord, Thomas B; Nicholson, Phillip D; Sicardy, Bruno

2005-10-07

Observations from the Cassini Visual and Infrared Mapping Spectrometer show an anomalously bright spot on Titan located at 80 degrees W and 20 degrees S. This area is bright in reflected light at all observed wavelengths, but is most noticeable at 5 microns. The spot is associated with a surface albedo feature identified in images taken by the Cassini Imaging Science Subsystem. We discuss various hypotheses about the source of the spot, reaching the conclusion that the spot is probably due to variation in surface composition, perhaps associated with recent geophysical phenomena.

Roche tomography of cataclysmic variables - VIII. The irradiated and spotted dwarf nova, SS Cygni

NASA Astrophysics Data System (ADS)

Hill, C. A.; Smith, Robert Connon; Hebb, L.; Szkody, P.

2017-12-01

We present the results of our spectroscopic study of the dwarf nova SS Cyg, using Roche tomography to map the stellar surface and derive the system parameters. Given that this technique takes into account the inhomogeneous brightness distribution on the surface of the secondary star, our derived parameters are (in principle) the most robust yet found for this system. Furthermore, our surface maps reveal that the secondary star is highly spotted, with strongly asymmetric irradiation on the inner hemisphere. Moreover, by constructing Doppler tomograms of several Balmer emission lines, we find strong asymmetric emission from the irradiated secondary star, and an asymmetric accretion disc that exhibits spiral structures.

All sky imaging observations in visible and infrared waveband for validation of satellite cloud and aerosol products

NASA Astrophysics Data System (ADS)

Lu, Daren; Huo, Juan; Zhang, W.; Liu, J.

A series of satellite sensors in visible and infrared wavelengths have been successfully operated on board a number of research satellites, e.g. NOAA/AVHRR, the MODIS onboard Terra and Aqua, etc. A number of cloud and aerosol products are produced and released in recent years. However, the validation of the product quality and accuracy are still a challenge to the atmospheric remote sensing community. In this paper, we suggest a ground based validation scheme for satellite-derived cloud and aerosol products by using combined visible and thermal infrared all sky imaging observations as well as surface meteorological observations. In the scheme, a visible digital camera with a fish-eye lens is used to continuously monitor the all sky with the view angle greater than 180 deg. The digital camera system is calibrated for both its geometry and radiance (broad blue, green, and red band) so as to a retrieval method can be used to detect the clear and cloudy sky spatial distribution and their temporal variations. A calibrated scanning thermal infrared thermometer is used to monitor the all sky brightness temperature distribution. An algorithm is developed to detect the clear and cloudy sky as well as cloud base height by using sky brightness distribution and surface temperature and humidity as input. Based on these composite retrieval of clear and cloudy sky distribution, it can be used to validate the satellite retrievals in the sense of real-simultaneous comparison and statistics, respectively. What will be presented in this talk include the results of the field observations and comparisons completed in Beijing (40 deg N, 116.5 deg E) in year 2003 and 2004. This work is supported by NSFC grant No. 4002700, and MOST grant No 2001CCA02200

New Observations of Subarcsecond Photospheric Bright Points

NASA Technical Reports Server (NTRS)

Berger, T. E.; Schrijver, C. J.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Scharmer, G.

1995-01-01

We have used an interference filter centered at 4305 A within the bandhead of the CH radical (the 'G band') and real-time image selection at the Swedish Vacuum Solar Telescope on La Palma to produce very high contrast images of subarcsecond photospheric bright points at all locations on the solar disk. During the 6 day period of 15-20 Sept. 1993 we observed active region NOAA 7581 from its appearance on the East limb to a near-disk-center position on 20 Sept. A total of 1804 bright points were selected for analysis from the disk center image using feature extraction image processing techniques. The measured FWHM distribution of the bright points in the image is lognormal with a modal value of 220 km (0.30 sec) and an average value of 250 km (0.35 sec). The smallest measured bright point diameter is 120 km (0.17 sec) and the largest is 600 km (O.69 sec). Approximately 60% of the measured bright points are circular (eccentricity approx. 1.0), the average eccentricity is 1.5, and the maximum eccentricity corresponding to filigree in the image is 6.5. The peak contrast of the measured bright points is normally distributed. The contrast distribution variance is much greater than the measurement accuracy, indicating a large spread in intrinsic bright-point contrast. When referenced to an averaged 'quiet-Sun' area in the image, the modal contrast is 29% and the maximum value is 75%; when referenced to an average intergranular lane brightness in the image, the distribution has a modal value of 61% and a maximum of 119%. The bin-averaged contrast of G-band bright points is constant across the entire measured size range. The measured area of the bright points, corrected for pixelation and selection effects, covers about 1.8% of the total image area. Large pores and micropores occupy an additional 2% of the image area, implying a total area fraction of magnetic proxy features in the image of 3.8%. We discuss the implications of this area fraction measurement in the context of previously published measurements which show that typical active region plage has a magnetic filling factor on the order of 10% or greater. The results suggest that in the active region analyzed here, less than 50% of the small-scale magnetic flux tubes are demarcated by visible proxies such as bright points or pores.

X-ray versus infrared selection of distant galaxy clusters: a case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-07-01

We present a comparison of two samples of z> 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray-selected XMM Large Scale Structure (LSS) distant cluster survey and 92 clusters from the optical-mid-infrared (MIR)-selected Spitzer Adaptation of the Red Sequence Cluster survey (SpARCS) cluster survey. Both samples are selected from the same approximately 9 sq deg sky area and we examine them using common XMM-Newton, Spitizer Wide-Area Infrared Extra-galactic (SWIRE) survey, and Canada-France-Hawaii Telescope Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: (i) X-ray bright, (ii) X-ray faint, MIR bright, and (iii) X-ray faint, MIR faint clusters. We determine that X-ray- and MIR-selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray- and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of brightest cluster galaxy-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

FORTY-SEVEN MILKY WAY-SIZED, EXTREMELY DIFFUSE GALAXIES IN THE COMA CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Dokkum, Pieter G.; Merritt, Allison; Geha, Marla

2015-01-10

We report the discovery of 47 low surface brightness objects in deep images of a 3° × 3° field centered on the Coma cluster, obtained with the Dragonfly Telephoto Array. The objects have central surface brightness μ(g, 0) ranging from 24-26 mag arcsec{sup –2} and effective radii r {sub eff} = 3''-10'', as measured from archival Canada-France-Hawaii Telescope images. From their spatial distribution we infer that most or all of the objects are galaxies in the Coma cluster. This relatively large distance is surprising as it implies that the galaxies are very large: with r {sub eff} = 1.5-4.6 kpcmore » their sizes are similar to those of L {sub *} galaxies even though their median stellar mass is only ∼6 × 10{sup 7} M {sub ☉}. The galaxies are relatively red and round, with (g – i) = 0.8 and (b/a) = 0.74. One of the 47 galaxies is fortuitously covered by a deep Hubble Space Telescope Advanced Camera for Surveys (ACS) observation. The ACS imaging shows a large spheroidal object with a central surface brightness μ{sub 475} = 25.8 mag arcsec{sup –2}, a Sérsic index n = 0.6, and an effective radius of 7'', corresponding to 3.4 kpc at the distance of Coma. The galaxy is not resolved into stars, consistent with expectations for a Coma cluster object. We speculate that these ''ultra-diffuse galaxies'' may have lost their gas supply at early times, possibly resulting in very high dark matter fractions.« less

Suzaku observations of low surface brightness cluster Abell 1631

NASA Astrophysics Data System (ADS)

Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

2018-04-01

We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

Suzaku observations of low surface brightness cluster Abell 1631

NASA Astrophysics Data System (ADS)

Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

2018-06-01

We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

The effect of monomolecular surface films on the microwave brightness temperature of the sea surface

NASA Technical Reports Server (NTRS)

Alpers, W.; Blume, H.-J. C.; Garrett, W. D.; Huehnerfuss, H.

1982-01-01

It is pointed out that monomolecular surface films of biological origin are often encountered on the ocean surface, especially in coastal regions. The thicknesses of the monomolecular films are of the order of 3 x 10 to the -9th m. Huehnerfuss et al. (1978, 1981) have shown that monomolecular surface films damp surface waves quite strongly in the centimeter to decimeter wavelength regime. Other effects caused by films are related to the reduction of the gas exchange at the air-sea interface and the decrease of the wind stress. The present investigation is concerned with experiments which reveal an unexpectedly large response of the microwave brightness temperature to a monomolecular oleyl alcohol slick at 1.43 GHz. Brightness temperature is a function of the complex dielectric constant of thy upper layer of the ocean. During six overflights over an ocean area covered with an artificial monomolecular alcohol film, a large decrease of the brightness temperature at the L-band was measured, while at the S-band almost no decrease was observed.

A Physical Model to Determine Snowfall over Land by Microwave Radiometry

NASA Technical Reports Server (NTRS)

Skofronick-Jackson, G.; Kim, M.-J.; Weinman, J. A.; Chang, D.-E.

2003-01-01

Because microwave brightness temperatures emitted by snow covered surfaces are highly variable, snowfall above such surfaces is difficult to observe using window channels that occur at low frequencies (v less than 100 GHz). Furthermore, at frequencies v less than or equal to 37 GHz, sensitivity to liquid hydrometeors is dominant. These problems are mitigated at high frequencies (v greater than 100 GHz) where water vapor screens the surface emission and sensitivity to frozen hydrometeors is significant. However the scattering effect of snowfall in the atmosphere at those higher frequencies is also impacted by water vapor in the upper atmosphere. This work describes the methodology and results of physically-based retrievals of snow falling over land surfaces. The theory of scattering by randomly oriented dry snow particles at high microwave frequencies appears to be better described by regarding snow as a concatenation of equivalent ice spheres rather than as a sphere with the effective dielectric constant of an air-ice mixture. An equivalent sphere snow scattering model was validated against high frequency attenuation measurements. Satellite-based high frequency observations from an Advanced Microwave Sounding Unit (AMSU-B) instrument during the March 5-6, 2001 New England blizzard were used to retrieve snowfall over land. Vertical distributions of snow, temperature and relative humidity profiles were derived from the Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) fifth-generation Mesoscale Model (MM5). Those data were applied and modified in a radiative transfer model that derived brightness temperatures consistent with the AMSU-B observations. The retrieved snowfall distribution was validated with radar reflectivity measurements obtained from the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) ground-based radar network.

THE STRUCTURE AND STELLAR CONTENT OF THE OUTER DISKS OF GALAXIES: A NEW VIEW FROM THE Pan-STARRS1 MEDIUM DEEP SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Zheng; Thilker, David A.; Heckman, Timothy M.

2015-02-20

We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (grizy) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis spectral energy distribution fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r {sub 90}, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples ofmore » galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r {sub 90}. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light ratio and stellar age radial profiles have a characteristic 'U' shape. There is a good correlation between the amplitude of the down-bend in the surface brightness profile and the rate of the increase in the M/L ratio in the outer disk. As we move from late- to early-type galaxies, the amplitude of the down-bend and the radial gradient in M/L both decrease. Our results imply a combination of stellar radial migration and suppression of recent star formation can account for the stellar populations of the outer disk.« less

Global Properties of M31's Stellar Halo from the SPLASH Survey. I. Surface Brightness Profile

NASA Astrophysics Data System (ADS)

Gilbert, Karoline M.; Guhathakurta, Puragra; Beaton, Rachael L.; Bullock, James; Geha, Marla C.; Kalirai, Jason S.; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Tollerud, Erik J.; Tanaka, Mikito; Chiba, Masashi

2012-11-01

We present the surface brightness profile of M31's stellar halo out to a projected radius of 175 kpc. The surface brightness estimates are based on confirmed samples of M31 red giant branch stars derived from Keck/DEIMOS spectroscopic observations. A set of empirical spectroscopic and photometric M31 membership diagnostics is used to identify and reject foreground and background contaminants. This enables us to trace the stellar halo of M31 to larger projected distances and fainter surface brightnesses than previous photometric studies. The surface brightness profile of M31's halo follows a power law with index -2.2 ± 0.2 and extends to a projected distance of at least ~175 kpc (~2/3 of M31's virial radius), with no evidence of a downward break at large radii. The best-fit elliptical isophotes have b/a = 0.94 with the major axis of the halo aligned along the minor axis of M31's disk, consistent with a prolate halo, although the data are also consistent with M31's halo having spherical symmetry. The fact that tidal debris features are kinematically cold is used to identify substructure in the spectroscopic fields out to projected radii of 90 kpc and investigate the effect of this substructure on the surface brightness profile. The scatter in the surface brightness profile is reduced when kinematically identified tidal debris features in M31 are statistically subtracted; the remaining profile indicates that a comparatively diffuse stellar component to M31's stellar halo exists to large distances. Beyond 90 kpc, kinematically cold tidal debris features cannot be identified due to small number statistics; nevertheless, the significant field-to-field variation in surface brightness beyond 90 kpc suggests that the outermost region of M31's halo is also comprised to a significant degree of stars stripped from accreted objects. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

The abundance properties of nearby late-type galaxies. II. The relation between abundance distributions and surface brightness profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilyugin, L. S.; Grebel, E. K.; Zinchenko, I. A.

2014-12-01

The relations between oxygen abundance and disk surface brightness (OH–SB relation) in the infrared W1 band are examined for nearby late-type galaxies. The oxygen abundances were presented in Paper I. The photometric characteristics of the disks are inferred here using photometric maps from the literature through bulge-disk decomposition. We find evidence that the OH–SB relation is not unique but depends on the galactocentric distance r (taken as a fraction of the optical radius R{sub 25}) and on the properties of a galaxy: the disk scale length h and the morphological T-type. We suggest a general, four-dimensional OH–SB relation with themore » values r, h, and T as parameters. The parametric OH–SB relation reproduces the observed data better than a simple, one-parameter relation; the deviations resulting when using our parametric relation are smaller by a factor of ∼1.4 than that of the simple relation. The influence of the parameters on the OH–SB relation varies with galactocentric distance. The influence of the T-type on the OH–SB relation is negligible at the centers of galaxies and increases with galactocentric distance. In contrast, the influence of the disk scale length on the OH–SB relation is at a maximum at the centers of galaxies and decreases with galactocentric distance, disappearing at the optical edges of galaxies. Two-dimensional relations can be used to reproduce the observed data at the optical edges of the disks and at the centers of the disks. The disk scale length should be used as a second parameter in the OH–SB relation at the center of the disk while the morphological T-type should be used as a second parameter in the relation at optical edge of the disk. The relations between oxygen abundance and disk surface brightness in the optical B and infrared K bands at the center of the disk and at optical edge of the disk are also considered. The general properties of the abundance–surface brightness relations are similar for the three considered bands B, K, and W1.« less

A Catalog of Galaxy Clusters Observed by XMM-Newton

NASA Technical Reports Server (NTRS)

Snowden, S. L.; Mushotzky, R. M.; Kuntz, K. D.; Davis, David S.

2007-01-01

Images and the radial profiles of the temperature, abundance, and brightness for 70 clusters of galaxies observed by XMM-Newton are presented along with a detailed discussion of the data reduction and analysis methods, including background modeling, which were used in the processing. Proper consideration of the various background components is vital to extend the reliable determination of cluster parameters to the largest possible cluster radii. The various components of the background including the quiescent particle background, cosmic diffuse emission, soft proton contamination, and solar wind charge exchange emission are discussed along with suggested means of their identification, filtering, and/or their modeling and subtraction. Every component is spectrally variable, sometimes significantly so, and all components except the cosmic background are temporally variable as well. The distributions of the events over the FOV vary between the components, and some distributions vary with energy. The scientific results from observations of low surface brightness objects and the diffuse background itself can be strongly affected by these background components and therefore great care should be taken in their consideration.

Surface-induced brightness temperature variations and their effects on detecting thin cirrus clouds using IR emission channels in the 8-12 microns region

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Wiscombe, W. J.

1994-01-01

A method for detecting cirrus clouds in terms of brightness temperature differences between narrowbands at 8, 11, and 12 microns has been proposed by Ackerman et al. In this method, the variation of emissivity with wavelength for different surface targets was not taken into consideration. Based on state-of-the-art laboratory measurements of reflectance spectra of terrestrial materials by Salisbury and D'Aria, it is found that the brightness temperature differences between the 8- and 11-microns bands for soils, rocks, and minerals, and dry vegetation can vary between approximately -8 and +8 K due solely to surface emissivity variations. The large brightness temperature differences are sufficient to cause false detection of cirrus clouds from remote sensing data acquired over certain surface targets using the 8-11-12-microns method directly. It is suggested that the 8-11-12-microns method should be improved to include the surface emissivity effects. In addition, it is recommended that in the future the variation of surface emissivity with wavelength should be taken into account in algorithms for retrieving surface temperatures and low-level atmospheric temperature and water vapor profiles.

Titan's surface from Cassini RADAR SAR and high resolution radiometry data of the first five flybys

USGS Publications Warehouse

Paganelli, F.; Janssen, M.A.; Stiles, B.; West, R.; Lorenz, R.D.; Lunine, J.I.; Wall, S.D.; Callahan, P.; Lopes, R.M.; Stofan, E.; Kirk, R.L.; Johnson, W.T.K.; Roth, L.; Elachi, C.; ,

2007-01-01

The first five Titan flybys with Cassini's Synthetic Aperture RADAR (SAR) and radiometer are examined with emphasis on the calibration and interpretation of the high-resolution radiometry data acquired during the SAR mode (SAR-radiometry). Maps of the 2-cm wavelength brightness temperature are obtained coincident with the SAR swath imaging, with spatial resolution approaching 6 km. A preliminary calibration shows that brightness temperature in these maps varies from 64 to 89 K. Surface features and physical properties derived from the SAR-radiometry maps and SAR imaging are strongly correlated; in general, we find that surface features with high radar reflectivity are associated with radiometrically cold regions, while surface features with low radar reflectivity correlate with radiometrically warm regions. We examined scatterplots of the normalized radar cross-section ??0 versus brightness temperature, finding differing signatures that characterize various terrains and surface features. Implications for the physical and compositional properties of these features are discussed. The results indicate that volume scattering is important in many areas of Titan's surface, particularly Xanadu, while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties. ?? 2007 Elsevier Inc.

Refinement in black chrome for use as a solar selective coating

NASA Technical Reports Server (NTRS)

Mcdonald, G. E.

1974-01-01

Black chrome is significant as a solar selective coating because the current extensive use of black chrome in the electroplating industry as a durable decorative finish makes black chrome widely available on a commercial scale and potentially low in cost as a solar selective coating. Black-chrome deposits were modified by underplating with dull nickel or by being plated on rough surfaces. Both of these procedures increased the visible absorptance. There was no change in the infrared reflectance for the dull-nickel - black-chrome combination from that reported for the bright-nickel - black-chrome combination. However, the bright-nickel - black-chrome coating plated on rough surfaces indicated a slight decrease in infrared reflectance. As integrated over the solar spectrum for air mass 2, the reflectance of the dull-nickel - black-chrome coating was 0.077, of the bright-nickel - black-chrome coating plated on a 0.75-micron (30-microinch) surface was 0.070, of the bright-nickel - black-chrome coating plated on a 2.5 micron (100-microinch) surface was 0.064. The corresponding values for the bright-nickel - black-chrome coating on a 0.0125-micron (0.5-microinch) surface, two samples of black nickel, and two samples of Nextrel black paint were 0.132, 0.123, 0.133, and 0.033, respectively.

Photometric properties of galaxies in the SDSS

NASA Astrophysics Data System (ADS)

Hogg, D. W.; Blanton, M.; SDSS Collaboration

2001-12-01

We analyze the number density distribution of galaxy properties in a sample of 8x 104 galaxies from the Sloan Digital Sky Survey, in the redshift range 0.02

X-ray emission from galaxies - The distribution of low-luminosity X-ray sources in the Galactic Centre region

NASA Astrophysics Data System (ADS)

Heard, Victoria; Warwick, Robert

2012-09-01

We report a study of the extended X-ray emission observed in the Galactic Centre (GC) region based on archival XMM-Newton data. The GC diffuse emission can be decomposed into three distinct components: the emission from low-luminosity point sources; the fluorescence of (and reflection from) dense molecular material; and soft (kT ~1 keV), diffuse thermal plasma emission most likely energised by supernova explosions. Here, we examine the emission due to unresolved point sources. We show that this source component accounts for the bulk of the 6.7-keV and 6.9-keV line emission. We fit the surface brightness distribution evident in these lines with an empirical 2-d model, which we then compare with a prediction derived from a 3-d mass model for the old stellar population in the GC region. We find that the X-ray surface brightness declines more rapidly with angular offset from Sgr A* than the mass-model prediction. One interpretation is that the X-ray luminosity per solar mass characterising the GC source population is increasing towards the GC. Alternatively, some refinement of the mass-distribution within the nuclear stellar disc may be required. The unresolved X-ray source population is most likely dominated by magnetic CVs. We use the X-ray observations to set constraints on the number density of such sources in the GC region. Our analysis does not support the premise that the GC is pervaded by very hot (~ 7.5 keV) thermal plasma, which is truly diffuse in nature.

Automated mapping of impervious surfaces in urban and suburban areas: Linear spectral unmixing of high spatial resolution imagery

NASA Astrophysics Data System (ADS)

Yang, Jian; He, Yuhong

2017-02-01

Quantifying impervious surfaces in urban and suburban areas is a key step toward a sustainable urban planning and management strategy. With the availability of fine-scale remote sensing imagery, automated mapping of impervious surfaces has attracted growing attention. However, the vast majority of existing studies have selected pixel-based and object-based methods for impervious surface mapping, with few adopting sub-pixel analysis of high spatial resolution imagery. This research makes use of a vegetation-bright impervious-dark impervious linear spectral mixture model to characterize urban and suburban surface components. A WorldView-3 image acquired on May 9th, 2015 is analyzed for its potential in automated unmixing of meaningful surface materials for two urban subsets and one suburban subset in Toronto, ON, Canada. Given the wide distribution of shadows in urban areas, the linear spectral unmixing is implemented in non-shadowed and shadowed areas separately for the two urban subsets. The results indicate that the accuracy of impervious surface mapping in suburban areas reaches up to 86.99%, much higher than the accuracies in urban areas (80.03% and 79.67%). Despite its merits in mapping accuracy and automation, the application of our proposed vegetation-bright impervious-dark impervious model to map impervious surfaces is limited due to the absence of soil component. To further extend the operational transferability of our proposed method, especially for the areas where plenty of bare soils exist during urbanization or reclamation, it is still of great necessity to mask out bare soils by automated classification prior to the implementation of linear spectral unmixing.

Missing mass or missing light?

NASA Astrophysics Data System (ADS)

Davies, J. I.

1990-07-01

Disney et al. (1989) have argued that the observational data are consistent with disk galaxies being optically thick, particularly in their inner regions. Here, these results are used to reinterpret the radial surface-brightness distributions of spiral galaxies. It is found that the fitting of a profile with an absorbed disk plus bulge leads to both disk and bulge masses (mass in luminous material) that are larger than previously assumed. In addition, it is shown how the rotation velocity, as determined from optical data in the central regions, may systematically underestimate the true rotational velocity in an optically thick disk. If the bulges of late-type galaxies are as large as is hypothesized, then this has important implications in models of galaxy evolution and galaxy dynamics. The model greatly reduces or even eliminates the need for dark matter within the optical radius; it removes a major argument against S0 evolution from later-type galaxies; it accounts for the similarity of rotation curve forms among galaxies of different morphological types; and it leads to a further reappraisal of the observed constancy of the extrapolated central surface brightness of galactic disks.

Effect of soil texture on the microwave emission from soils

NASA Technical Reports Server (NTRS)

Schmugge, T. J.

1980-01-01

The intensity brightness temperature of the microwave emission from the soil is determined primarily by its dielectric properties. The large difference between the dielectric constant of water and that of dry soil produces a strong dependence of the soil's dielectric constant on its moisture content. This dependence is effected by the texture of the soil because the water molecules close to the particle surface are tightly bound and do not contribute significantly to the dielectric properties. Since this surface area is a function of the particle size distribution (soil texture), being larger for clay soils with small particles, and smaller for sandy soils with larger particles; the dielectric properties will depend on soil texture. Laboratory measurements of the dielectric constant for soils are summarized. The dependence of the microwave emission on texture is demonstrated by measurements of brightness temperature from an aircraft platform for a wide range of soil textures. It is concluded that the effect of soil texture differences on the observed values can be normalized by expressing the soil moisture values as a percent field capacity for the soil.

Mercury's Na Exosphere from MESSENGER Data

NASA Technical Reports Server (NTRS)

Killen, Rosemary M.; Burger, M. H.; Cassidy, T. A.; Sarantos, M.; Vervack, R. J.; McClintock, W. El; Merkel, A. W.; Sprague, A. L.; Solomon, S. C.

2012-01-01

MESSENGER entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UWS) channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) has been observing Mercury's exosphere nearly continuously. Daily measurements of Na brightness were fitted with non-uniform exospheric models. With Monte Carlo sampling we traced the trajectories of a representative number of test particles, generally one million per run per source process, until photoionization, escape from the gravitational well, or permanent sticking at the surface removed the atom from the simulation. Atoms were assumed to partially thermally accommodate on each encounter with the surface with accommodation coefficient 0.25. Runs for different assumed source processes are run separately, scaled and co-added. Once these model results were saved onto a 3D grid, we ran lines of sight from the MESSENGER spacecraft :0 infinity using the SPICE kernels and we computed brightness integrals. Note that only particles that contribute to the measurement can be constrained with our method. Atoms and molecules produced on the nightside must escape the shadow in order to scatter light if the excitation process is resonant-light scattering, as assumed here. The aggregate distribution of Na atoms fits a 1200 K gas, with a PSD distribution, along with a hotter component. Our models constrain the hot component, assumed to be impact vaporization, to be emitted with a 2500 K Maxwellian. Most orbits show a dawnside enhancement in the hot component broadly spread over the leading hemisphere. However, on some dates there is no dawn/dusk asymmetry. The portion of the hot/cold source appears to be highly variable.

Stellar Disk Truncations: HI Density and Dynamics

NASA Astrophysics Data System (ADS)

Trujillo, Ignacio; Bakos, Judit

2010-06-01

Using HI Nearby Galaxy Survey (THINGS) 21-cm observations of a sample of nearby (nearly face-on) galaxies we explore whether the stellar disk truncation phenomenon produces any signature either in the HI gas density and/or in the gas dynamics. Recent cosmological simulations suggest that the origin of the break on the surface brightness distribution is produced by the appearance of a warp at the truncation position. This warp should produce a flaring on the gas distribution increasing the velocity dispersion of the HI component beyond the break. We do not find, however, any evidence of this increase in the gas velocity dispersion profile.

STM/STS Study of LixCoO2 Single Crystals

NASA Astrophysics Data System (ADS)

Iwaya, Katsuya; Minato, Taketoshi; Miyoshi, Kiyotaka; Takeuchi, Jun; Kim, Yousoo; Hitosugi, Taro

2012-02-01

We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on LixCoO2 (x=0.66) single crystal surfaces. A (1x1) hexagonal lattice was clearly observed and found to be moved by changing bias-voltage polarity, indicating that this could be associated with Li ions on the surface. Under the (1x1) hexagonal lattice, we imaged almost randomly distributed bright dots that were strongly dependent on bias-voltage, with insulating spectroscopic features. Different area on the surface showed a (2x2) hexagonal lattice that could be related to an ordering of Co^3+ and Co^4+ ions. These results suggest the electronic structure of LixCoO2 surface is inhomogeneous possibly due to segregation of Li ions.

Apparent Brightness and Topography Images of Vibidia Crater

NASA Image and Video Library

2012-03-09

The left-hand image from NASA Dawn spacecraft shows the apparent brightness of asteroid Vesta surface. The right-hand image is based on this apparent brightness image, with a color-coded height representation of the topography overlain onto it.

Thermal measurements of dark and bright surface features on Vesta as derived from Dawn/VIR

USGS Publications Warehouse

Tosi, Federico; Capria, Maria Teresa; De Sanctis, M.C.; Combe, J.-Ph.; Zambon, F.; Nathues, A.; Schröder, S.E.; Li, J.-Y.; Palomba, E.; Longobardo, A.; Blewett, D.T.; Denevi, B.W.; Palmer, E.; Capaccioni, F.; Ammannito, E.; Titus, Timothy N.; Mittlefehldt, D.W.; Sunshine, J.M.; Russell, C.T.; Raymond, C.A.; Dawn/VIR Team,

2014-01-01

Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1-10 km) is related to physical properties that can provide information about the origin of those materials. We use Dawn’s Visible and InfraRed (VIR) mapping spectrometer hyperspectral data to retrieve surface temperatures and emissivities, with high accuracy as long as temperatures are greater than 220 K. Some of the dark and bright features were observed multiple times by VIR in the various mission phases at variable spatial resolution, illumination and observation angles, local solar time, and heliocentric distance. This work presents the first temperature maps and spectral emissivities of several kilometer-scale dark and bright material units on Vesta. Results retrieved from the infrared data acquired by VIR show that bright regions generally correspond to regions with lower temperature, while dark regions correspond to areas with higher temperature. During maximum daily insolation and in the range of heliocentric distances explored by Dawn, i.e. 2.23-2.54 AU, the warmest dark unit found on Vesta rises to a temperature of 273 K, while bright units observed under comparable conditions do not exceed 266 K. Similarly, dark units appear to have higher emissivity on average compared to bright units. Dark-material units show a weak anticorrelation between temperature and albedo, whereas the relation is stronger for bright material units observed under the same conditions. Individual features may show either evanescent or distinct margins in the thermal images, as a consequence of the cohesion of the surface material. Finally, for the two categories of dark and bright materials, we were able to highlight the influence of heliocentric distance on surface temperatures, and estimate an average temperature rate change of 1% following a variation of 0.04 AU in the solar distance.

Stellar Populations in Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Angeletti, Lucio; Giannone, Pietro

The R1/n law for the radial surface brightness of elliptical galaxies and the "Best Accretion Model" together with the "Concentration Model" have been combined in order to determine the mass and dynamical structure of largely-populated star systems. Families of models depending on four parameters have been used to fit the observed surface radial profiles of some spectro-photometric indices of a sample of eleven galaxies. We present the best agreements of the spectral index Mg2 with observations for three selected galaxies representative of the full sample. For them we have also computed the spatial distributions of the metal abundances, which are essential to achieve a population synthesis.

THE DOMINANCE OF METAL-RICH STREAMS IN STELLAR HALOS: A COMPARISON BETWEEN SUBSTRUCTURE IN M31 AND {lambda}CDM MODELS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, Karoline M.; Font, Andreea S.; Johnston, Kathryn V.

2009-08-10

Extensive photometric and spectroscopic surveys of the Andromeda galaxy (M31) have discovered tidal debris features throughout M31's stellar halo. We present stellar kinematics and metallicities in fields with identified substructure from our on-going SPLASH survey of M31 red giant branch stars with the DEIMOS spectrograph on the Keck II 10 m telescope. Radial velocity criteria are used to isolate members of the kinematically cold substructures. The substructures are shown to be metal-rich relative to the rest of the dynamically hot stellar population in the fields in which they are found. We calculate the mean metallicity and average surface brightness ofmore » the various kinematical components in each field, and show that, on average, higher surface brightness features tend to be more metal-rich than lower surface brightness features. Simulations of stellar halo formation via accretion in a cosmological context are used to illustrate that the observed trend can be explained as a natural consequence of the observed dwarf galaxy mass-metallicity relation. A significant spread in metallicity at a given surface brightness is seen in the data; we show that this is due to time effects, namely, the variation in the time since accretion of the tidal streams' progenitor onto the host halo. We show that in this theoretical framework a relationship between the alpha-enhancement and surface brightness of tidal streams is expected, which arises from the varying times of accretion of the progenitor satellites onto the host halo. Thus, measurements of the alpha-enrichment, metallicity, and surface brightness of tidal debris can be used to reconstruct the luminosity and time of accretion onto the host halo of the progenitors of tidal streams.« less

Stellar populations of bulges in galaxies with a low surface-brightness disc

NASA Astrophysics Data System (ADS)

Morelli, L.; Corsini, E. M.; Pizzella, A.; Dalla Bontà, E.; Coccato, L.; Méndez-Abreu, J.

2015-03-01

The radial profiles of the Hβ, Mg, and Fe line-strength indices are presented for a sample of eight spiral galaxies with a low surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength indices and velocity dispersion are consistent to those known for early-type galaxies and bulges of high surface-brightness galaxies. The age, metallicity, and α/Fe enhancement of the stellar populations in the bulge-dominated region are obtained using stellar population models with variable element abundance ratios. Almost all the sample bulges are characterized by a young stellar population, on-going star formation, and a solar α/Fe enhancement. Their metallicity spans from high to sub-solar values. No significant gradient in age and α/Fe enhancement is measured, whereas only in a few cases a negative metallicity gradient is found. These properties suggest that a pure dissipative collapse is not able to explain formation of all the sample bulges and that other phenomena, like mergers or acquisition events, need to be invoked. Such a picture is also supported by the lack of a correlation between the central value and gradient of the metallicity in bulges with very low metallicity. The stellar populations of the bulges hosted by low surface-brightness discs share many properties with those of high surface-brightness galaxies. Therefore, they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that in spite of being hosted by discs with extremely different properties, the bulges of low and high surface-brightness discs are remarkably similar.

Physical properties of the ionized gas and brightness distribution in NGC4736

NASA Astrophysics Data System (ADS)

Rodrigues, I.; Dottori, H.; Cepa, J.; Vilchez, J.

1998-03-01

In this work we study the galaxy NGC4736, using narrow band interference filters imaging centered at the emission lines {Oii} {3727+3729}, Hβ, {Oiii} {5007}, Hα, {Sii} {6716+6730} and {Siii} {9070} and nearby continua. We have obtained sizes, positions, emission line absolute fluxes, and continua intensities for 90 Hii regions, mainly distributed in a ring-like structure of 3.2kpc in diameter. The Hα luminosities are in the range 37.3 <= log L_Hα <= 39.4 ergs(-1) . The Hii regions size distribution presents a characteristic diameter D_0 = 115pc and verifies the relation log (L_Hα ) ~D(3) . The temperature of the ionizing sources and the metallicity of the Hii regions are respectively in the ranges 3.410(4) <~T_⋆ <~ 4.010(4) K and 8.5 <~12 + log (O/H) <~9.3. The masses of the ionizing clusters are in the range 510(3) <~M_T/M_sun <~210(5) . The continua radial surface brightness distribution is better fitted by the superposition of a de Vaucouleurs', a thin and a thick exponential disk laws. The monochromatic colors show that outside the star forming ring the disk presents a younger stellar population than inside it. Tables 3 and 4 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Little Bright Spot

NASA Image and Video Library

2015-01-12

A bright spot can be seen on the left side of Rhea in this image. The spot is the crater Inktomi, named for a Lakota spider spirit. Inktomi is believed to be the youngest feature on Rhea (949 miles or 1527 kilometers across). The relative youth of the feature is evident by its brightness. Material that is newly excavated from below the moon's surface and tossed across the surface by a cratering event, appears bright. But as the newly exposed surface is subjected to the harsh space environment, it darkens. This is one technique scientists use to date features on surfaces. This view looks toward the trailing hemisphere of Rhea. North on Rhea is up and rotated 21 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 29, 2013. The view was obtained at a distance of approximately 1.0 million miles (1.6 million kilometers) fro http://photojournal.jpl.nasa.gov/catalog/PIA18300

Adjusting the tasseled cap brightness and greenness factors for atmospheric path radiance and absorption on a pixel by pixel basis

NASA Technical Reports Server (NTRS)

Jackson, R. D.; Slater, P. N.; Pinter, P. J. (Principal Investigator)

1982-01-01

A radiative transfer model was used to convert ground measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS7 (0.8 to 1.1 m) was multiplied by the transmission fraction for atmospheres having different levels of precipitable water. The radiance values were converted to simulated LANDSAT digital counts for four path radiance levels and four levels of precipitable water. These values were used to calculate the Kauth-Thomas brightness, greenness, yellowness, and nonsuch factors. Brightness was affected by surface conditions and path radiance. Greenness was affected by surface conditions, path radiance, and precipitable water. Yellowness was affected by path radiance and nonsuch by precipitable water, and both factors changed only slightly with surface conditions. Yellowness and nonsuch were used to adjust brightness and greenness to produce factors that were affected only by surface conditions such as soils and vegetation, and not by path radiance and precipitable water.

New Observations of Subarcsecond Photospheric Bright Points

NASA Technical Reports Server (NTRS)

Berger, T. E.; Schrijver, C. J.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Scharmer, G.

1995-01-01

We have used an interference filter centered at 4305 A within the bandhead of the CH radical (the 'G band') and real-time image selection at the Swedish Vacuum Solar Telescope on La Palma to produce very high contrast images of subarcsecond photospheric bright points at all locations on the solar disk. During the 6 day period of 1993 September 15-20 we observed active region NOAA 7581 from its appearance on the East limb to a near-disk-center position on September 20. A total of 1804 bright points were selected for analysis from the disk center image using feature extraction image processing techniques. The measured Full Width at Half Maximum (FWHM) distribution of the bright points in the image is lognormal with a modal value of 220 km (0 sec .30) and an average value of 250 km (0 sec .35). The smallest measured bright point diameter is 120 km (0 sec .17) and the largest is 600 km (O sec .69). Approximately 60% of the measured bright points are circular (eccentricity approx. 1.0), the average eccentricity is 1.5, and the maximum eccentricity corresponding to filigree in the image is 6.5. The peak contrast of the measured bright points is normally distributed. The contrast distribution variance is much greater than the measurement accuracy, indicating a large spread in intrinsic bright-point contrast. When referenced to an averaged 'quiet-Sun' area in the image, the modal contrast is 29% and the maximum value is 75%; when referenced to an average intergranular lane brightness in the image, the distribution has a modal value of 61% and a maximum of 119%. The bin-averaged contrast of G-band bright points is constant across the entire measured size range. The measured area of the bright points, corrected for pixelation and selection effects, covers about 1.8% of the total image area. Large pores and micropores occupy an additional 2% of the image area, implying a total area fraction of magnetic proxy features in the image of 3.8%. We discuss the implications of this area fraction measurement in the context of previously published measurements which show that typical active region plage has a magnetic filling factor on the order of 10% or greater. The results suggest that in the active region analyzed here, less than 50% of the small-scale magnetic flux tubes are demarcated by visible proxies such as bright points or pores.

Modeling the ejecta cloud in the first seconds after Deep Impact

NASA Astrophysics Data System (ADS)

Nagdimunov, L.; Kolokolova, L.; Wolff, M.; A'Hearn, M.; Farnham, T.

2014-07-01

Although the Deep Impact experiment was performed nine years ago, analysis of its data continues to shed light on our understanding of cometary atmospheres, surfaces, and interiors. We analyze the images acquired by the Deep Impact spacecraft High Resolution Instrument (HRI) in the first seconds after impact. These early images reflect the development of the material excavation from the cometary nucleus, enabling a study of fresh, unprocessed nuclear material, and potentially allowing a peek into the interior. Simply studying the brightness of the ejecta plume and its distribution as a function of height and time after impact could provide some insight into the characteristics of the ejecta. However, the optical thickness of the ejecta offers an additional source of information through the resultant shadow on the surface of the nucleus and brightness variations within it. Our goal was to reproduce both the distribution of brightness in the plume and in its shadow, thus constraining the characteristics of the ejecta. To achieve this, we used a 3D radiative-transfer package HYPERION [1], which allows an arbitrary spatial distribution and multiple dust components, for simulations of multiple scattering with realistic scattering and observational geometries. The parameters of our dust modeling were composition, size distribution, and number density of particles at the base of the ejecta cone (the last varied with the height, h, as h^{-3}). Composition was created as a mixture of so called Halley-like dust (silicates, carbon, and organics, see [2]), ice, and voids to account for particle porosity. We performed a parameter survey, searching for dust/ice ratios and particle porosity that could reproduce a density of the individual particles equal to the bulk density of the nucleus, 0.4 g/(cm^3), or 1.75 g/(cm^3) used in [3] to model crater development. The size distribution was taken from [4] and the number density was varied to achieve the best fit. To further constrain the results, we compared them with those of crater modeling [3]. Based on the approach given in [3] and using the crater diameter from [5], the mass of the ejecta 1 sec. after impact was estimated as 9×10^3-2×10^4 kg. The best fit to Deep Impact data and excavated mass constraints was achieved with ˜10% Halley dust, ˜20% ice, and the rest voids by volume for density 0.4 g/(cm^3) and ˜65% Halley dust with 38-8 % ice, depending on porosity, for density 1.75 g/(cm^3). Both cases result in a number density of ˜(10^4) particles/(cm^3). The dust/ice mass ratio for each density is ≥1, which is consistent with [6]. To reproduce the correct position and geometry of the shadow, we had to modify the geometry of the ejecta cone originally prescribed in [3]. This was required, in part, by the use of a revised nuclear shape model [7]. Our estimate of cone tilt differs from the previous one by 13.2°. It appeared that the observed change in brightness of the plume and shadow during the first second cannot be reproduced by a hollow cone. This is consistent with lab simulations of oblique impacts [8] which showed that hollowness of the ejecta cone can develop somewhat later in the plume evolution. Variations of brightness within the plume and the shadow can reveal the structure of the upper layers of the nucleus.

Giant Low Surface Brightness Galaxies

NASA Astrophysics Data System (ADS)

Mishra, Alka; Kantharia, Nimisha G.; Das, Mousumi

2018-04-01

In this paper, we present radio observations of the giant low surface brightness (LSB) galaxies made using the Giant Metrewave Radio Telescope (GMRT). LSB galaxies are generally large, dark matter dominated spirals that have low star formation efficiencies and large HI gas disks. Their properties suggest that they are less evolved compared to high surface brightness galaxies. We present GMRT emission maps of LSB galaxies with an optically-identified active nucleus. Using our radio data and archival near-infrared (2MASS) and near-ultraviolet (GALEX) data, we studied morphology and star formation efficiencies in these galaxies. All the galaxies show radio continuum emission mostly associated with the centre of the galaxy.

Evidence for a Multiphase ISM in Early Type Galaxies and Elliptical Galaxies with Strong Radio Continuum

NASA Technical Reports Server (NTRS)

Kim, Dong Woo

1997-01-01

We have observed NGC 1316 (Fornax A) with the ROSAT HRI. In this paper, we present the results of these observations and we complement them with the spectral analysis of the archival PSPC data. The spectral properties suggest the presence of a significant component of thermal X-ray emission (greater than 60%), amounting to approx. 10(exp 9) solar mass of hot ISM. Within 3 feet from the nucleus of NGC 1316, the HRI X-ray surface brightness falls as r(exp -2) following the stellar light. In the inner approx. 30 inch., however, the X-ray surface brightness is significantly elongated, contrary to the distribution of stellar light, which is significantly rounder within 10 inch. This again argues for a non-stellar origin of the X-ray emission. This flattened X-ray feature is suggestive of either the disk-like geometry of a rotating cooling flow and/or the presence of extended, elongated dark matter. By comparing the morphology of the X-ray emission with the distribution of optical dust patches, we find that the X-ray emission is significantly reduced at the locations where the dust patches are more pronounced, indicating that at least some of the X-ray photons are absorbed by the cold ISM. We also compare the distribution of the hot and cold ISM with that of the ionized gas, using recently obtained H(sub alpha) CCD data. We find that the ionized gas is distributed roughly along the dust patches and follows the large scale X-ray distribution at r greater than 1 foot from the nucleus. However, there is no one-to-one correspondence between ionized gas and hot gas. Both morphological relations and kinematics suggest different origins for hot and cold ISM. The radio jets in projection appear to pass perpendicularly through the central X-ray ellipsoid. Comparison of thermal and radio pressures suggests that the radio jets are confined by the surrounding hot gaseous medium.

Leonids 2017 from Norway – A bright surprise!

NASA Astrophysics Data System (ADS)

Gaarder, K.

2018-01-01

I am very pleased to have been able to observe near maximum activity of the Leonids, and clearly witnessed the unequal mass distribution during these hours. A lot of bright Leonids were seen, followed by a short period of high activity of fainter meteors, before a sharp drop in activity. The Leonids is undoubtedly a shower to watch closely, with its many variations in activity level and magnitude distribution. I already look forward to observing the next years’ display, hopefully under a dark and clear sky, filled with bright meteors!

High-Contrast Near-Infrared Imaging Polarimetry of the Protoplanetary Disk around RY Tau

NASA Technical Reports Server (NTRS)

Takami, Michihiro; Karr, Jennifer L.; Hashimoto, Jun; Kim, Hyosun; Wisenewski, John; Henning, Thomas; Grady, Carol; Kandori, Ryo; Hodapp, Klaus W.; Kudo, Tomoyuki;

Generalized dark-bright vector soliton solution to the mixed coupled nonlinear Schrödinger equations.

PubMed

Manikandan, N; Radhakrishnan, R; Aravinthan, K

2014-08-01

We have constructed a dark-bright N-soliton solution with 4N+3 real parameters for the physically interesting system of mixed coupled nonlinear Schrödinger equations. Using this as well as an asymptotic analysis we have investigated the interaction between dark-bright vector solitons. Each colliding dark-bright one-soliton at the asymptotic limits includes more coupling parameters not only in the polarization vector but also in the amplitude part. Our present solution generalizes the dark-bright soliton in the literature with parametric constraints. By exploiting the role of such coupling parameters we are able to control certain interaction effects, namely beating, breathing, bouncing, attraction, jumping, etc., without affecting other soliton parameters. Particularly, the results of the interactions between the bound state dark-bright vector solitons reveal oscillations in their amplitudes under certain parametric choices. A similar kind of effect was also observed experimentally in the BECs. We have also characterized the solutions with complicated structure and nonobvious wrinkle to define polarization vector, envelope speed, envelope width, envelope amplitude, grayness, and complex modulation. It is interesting to identify that the polarization vector of the dark-bright one-soliton evolves on a spherical surface instead of a hyperboloid surface as in the bright-bright case of the mixed coupled nonlinear Schrödinger equations.

Spectrophotometric experiment on the Verera-11 and Venera-12 descent vehicles: Some results of the analysis of the spectrum of the daytime sky of Venus

NASA Technical Reports Server (NTRS)

Moroz, V. I.; Moshkin, B. Y.; Ekonomov, A. P.; Sanko, N. F.; Parfentev, N. A.; Golovin, Y. M.

1979-01-01

The spectra of the daytime sky of Venus were recorded on the Venera-11 and Venera-12 descent vehicles at various altitudes above the planet's surface, within the interval of 4500 to 12,000 Angstroms. The angular distribution of the brightness of the scattered radiation was recorded and the ratio of water and carbon dioxide were studied, with respect to the cloud cover boundaries.

Pyroclastic Deposits on Venus as Indicators of the Youngest Volcanism

NASA Technical Reports Server (NTRS)

Campbell, B. A.; Morgan, G. A.; Whitten, J. L.; Carter, L. M.; Glaze, L. S.; Campbell, D. B.

2017-01-01

While most of the surface of Venus formed by effusive volcanic processes, deposits suggesting eruption styles that distribute airfall debris over large areas, or ground-hugging flows from plume collapse, are not common. Prior work notes radar-bright units with diffuse margins, generally consistent with a plume collapse emplacement model, in Eistla Regio, Dione Regio, and near Sappho Patera. We examine these deposits, and map additional occurrences, using Magellan data and Earth-based polarimetric radar maps from 1988, 2012, and 2015 observations.

Arecibo radar imagery of Mars: The major volcanic provinces

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, Michael C.; Husmann, Diana I.; Campbell, Bruce A.

2012-08-01

We present Earth-based radar images of Mars obtained with the upgraded Arecibo S-band (λ = 12.6 cm) radar during the 2005-2012 oppositions. The imaging was done using the same long-code delay-Doppler technique as for the earlier (pre-upgrade) imaging but at a much higher resolution (˜3 km) and, for some regions, a more favorable sub-Earth latitude. This has enabled us to make a more detailed and complete mapping of depolarized radar reflectivity (a proxy for small-scale surface roughness) over the major volcanic provinces of Tharsis, Elysium, and Amazonis. We find that vast portions of these regions are covered by radar-bright lava flows exhibiting circular polarization ratios close to unity, a characteristic that is uncommon for terrestrial lavas and that is a likely indicator of multiple scattering from extremely blocky or otherwise highly disrupted flow surfaces. All of the major volcanoes have radar-bright features on their shields, although the brightness distribution on Olympus Mons is very patchy and the summit plateau of Pavonis Mons is entirely radar-dark. The older minor shields (paterae and tholi) are largely or entirely radar-dark, which is consistent with mantling by dust or pyroclastic material. Other prominent radar-dark features include: the "fan-shaped deposits", possibly glacial, associated with the three major Tharsis Montes shields; various units of the Medusae Fossae Formation; a region south and west of Biblis Patera where "Stealth" deposits appear to obscure Tharsis flows; and a number of "dark-halo craters" with radar-absorbing ejecta blankets deposited atop surrounding bright flows. Several major bright features in Tharsis are associated with off-shield lava flows; these include the Olympus Mons basal plains, volcanic fields east and south of Pavonis Mons, the Daedalia Planum flows south of Arsia Mons, and a broad expanse of flows extending east from the Tharsis Montes to Echus Chasma. The radar-bright lava plains in Elysium are concentrated mainly in Cerberus and include the fluvio-volcanic channels of Athabasca Valles, Grjotá Valles, and Marte Valles, as well as an enigmatic region at the southern tip of the Cerberus basin. Some of the Cerberus bright features correspond to the distinctive "platy-ridged" flows identified in orbiter images. The radar-bright terrain in Amazonis Planitia comprises two distinct but contiguous sections: a northern section formed of lavas and sediments debouched from Marte Valles and a southern section whose volcanics may derive, in part, from local sources. This South Amazonis region shows perhaps the most complex radar-bright structure on Mars and includes features that correspond to platy-ridged flows similar to those in Cerberus.

Examination of in vivo tear film stability after eye blink and eye drying

NASA Astrophysics Data System (ADS)

Szczesna, Dorota H.; Kulas, Zbigniew; Kasprzak, Henryk T.; Stenevi, Ulf

2007-07-01

The purpose of this study is to investigate the kinetics of precorneal tear film stabilization process after eye blink and the process of creating the break-up of the tear film layer. The tear film of patients were examined in vivo by used the lateral shearing interferometer. The information about the distribution and stability of the tear film over the cornea is carried by the wave front reflected from the surface of tears and coded in interference fringes. Smooth and regular fringes indicate the smooth surface of tears over the cornea. Immediately after eye blink the interference fringes are observed on background of bright and dark areas. The contrast of this structure fades with time slowly and after 1-3 sec the background of interference fringes becomes uniform. The vertical orientation and instability of this structure suggests connection with eyelid movement and the spread of tears. If the eye is kept open for a long time, bright lines appear in the background of fringes after a dozen seconds. The slowly appearing structure might signify the tear film break-up. In case of eyes after a LASIK surgery the shape of the background structure has different nature and might be stable in time suggesting the stability of the corneal surface irregularities.

Polarization of Light by Leaves and Plant Canopies

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C.

2006-01-01

This talk will focus first on the information contained in the surface-scattered light from leaves, plant canopies and surface waters. This light is in general polarized and depends upon surface roughness. Thus, for example, - The surface reflection from shiny green leaves measured in the specular direction shows no chlorophyll absorption bands, no 'red edge.' - Conversely, the degree of linear polarization of such light displays marked variation with wavelength having local maxima in the chlorophyll absorption bands and an inverted red edge. - Plant canopies with shiny leaves distributed in angle like the area on a sphere, specularly reflect sunlight in the subsolar or specular direction- but also in every other view direction. - Canopies of green plants may appear white not green when viewed obliquely toward the sun. - In a light to moderate wind, the often blindingly bright glitter of sunlight off smooth water surfaces provides a strong, angularly narrow signature reflection characteristic of inundated vegetated areas that are big sources of atmospheric methane, a climatically important greenhouse gas. (Conversely, a blindingly bright glitter-type reflection is uncharacteristic of upland or wind ruffled open water areas that are poor sources of atmospheric methane.) Because some of these results may be 'head scratchers,' it's always important to properly calibrate ones instruments. Indeed, as the second portion of the talk will show, the characteristics of the light measuring instrument, particularly its entrance aperture, may affect the results and should be taken into account during across-instrument data comparisons.

Version 3 of the SMAP Level 4 Soil Moisture Product

NASA Technical Reports Server (NTRS)

Reichle, Rolf; Liu, Qing; Ardizzone, Joe; Crow, Wade; De Lannoy, Gabrielle; Kolassa, Jana; Kimball, John; Koster, Randy

2017-01-01

The NASA Soil Moisture Active Passive (SMAP) Level 4 Soil Moisture (L4_SM) product provides 3-hourly, 9-km resolution, global estimates of surface (0-5 cm) and root zone (0-100 cm) soil moisture as well as related land surface states and fluxes from 31 March 2015 to present with a latency of 2.5 days. The ensemble-based L4_SM algorithm is a variant of the Goddard Earth Observing System version 5 (GEOS-5) land data assimilation system and ingests SMAP L-band (1.4 GHz) Level 1 brightness temperature observations into the Catchment land surface model. The soil moisture analysis is non-local (spatially distributed), performs downscaling from the 36-km resolution of the observations to that of the model, and respects the relative uncertainties of the modeled and observed brightness temperatures. Prior to assimilation, a climatological rescaling is applied to the assimilated brightness temperatures using a 6 year record of SMOS observations. A new feature in Version 3 of the L4_SM data product is the use of 2 years of SMAP observations for rescaling where SMOS observations are not available because of radio frequency interference, which expands the impact of SMAP observations on the L4_SM estimates into large regions of northern Africa and Asia. This presentation investigates the performance and data assimilation diagnostics of the Version 3 L4_SM data product. The L4_SM soil moisture estimates meet the 0.04 m3m3 (unbiased) RMSE requirement. We further demonstrate that there is little bias in the soil moisture analysis. Finally, we illustrate where the assimilation system overestimates or underestimates the actual errors in the system.

Structural analysis of star-forming blue early-type galaxies. Merger-driven star formation in elliptical galaxies

NASA Astrophysics Data System (ADS)

George, Koshy

2017-02-01

Context. Star-forming blue early-type galaxies at low redshift can give insight to the stellar mass growth of L⋆ elliptical galaxies in the local Universe. Aims: We wish to understand the reason for star formation in these otherwise passively evolving red and dead stellar systems. The fuel for star formation can be acquired through recent accretion events such as mergers or flyby. The signatures of such events should be evident from a structural analysis of the galaxy image. Methods: We carried out structural analysis on SDSS r-band imaging data of 55 star-forming blue elliptical galaxies, derived the structural parameters, analysed the residuals from best-fit to surface brightness distribution, and constructed the galaxy scaling relations. Results: We found that star-forming blue early-type galaxies are bulge-dominated systems with axial ratio >0.5 and surface brightness profiles fitted by Sérsic profiles with index (n) mostly >2. Twenty-three galaxies are found to have n< 2; these could be hosting a disc component. The residual images of the 32 galaxy surface brightness profile fits show structural features indicative of recent interactions. The star-forming blue elliptical galaxies follow the Kormendy relation and show the characteristics of normal elliptical galaxies as far as structural analysis is concerned. There is a general trend for high-luminosity galaxies to display interaction signatures and high star formation rates. Conclusions: The star-forming population of blue early-type galaxies at low redshifts could be normal ellipticals that might have undergone a recent gas-rich minor merger event. The star formation in these galaxies will shut down once the recently acquired fuel is consumed, following which the galaxy will evolve to a normal early-type galaxy.

A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters

NASA Astrophysics Data System (ADS)

Muñoz, Ricardo R.; Côté, Patrick; Santana, Felipe A.; Geha, Marla; Simon, Joshua D.; Oyarzún, Grecco A.; Stetson, Peter B.; Djorgovski, S. G.

2018-06-01

We present structural parameters from a wide-field homogeneous imaging survey of Milky Way satellites carried out with the MegaCam imagers on the 3.6 m Canada–France–Hawaii Telescope and 6.5 m Magellan-Clay telescope. Our survey targets an unbiased sample of “outer halo” satellites (i.e., substructures having galactocentric distances greater than 25 kpc) and includes classical dSph galaxies, ultra-faint dwarfs, and remote globular clusters. We combine deep, panoramic gr imaging for 44 satellites and archival gr imaging for 14 additional objects (primarily obtained with the DECam instrument as part of the Dark Energy Survey) to measure photometric and structural parameters for 58 outer halo satellites. This is the largest and most uniform analysis of Milky Way satellites undertaken to date and represents roughly three-quarters (58/81 ≃ 72%) of all known outer halo satellites. We use a maximum-likelihood method to fit four density laws to each object in our survey: exponential, Plummer, King, and Sérsic models. We systematically examine the isodensity contour maps and color–magnitude diagrams for each of our program objects, present a comparison with previous results, and tabulate our best-fit photometric and structural parameters, including ellipticities, position angles, effective radii, Sérsic indices, absolute magnitudes, and surface brightness measurements. We investigate the distribution of outer halo satellites in the size–magnitude diagram and show that the current sample of outer halo substructures spans a wide range in effective radius, luminosity, and surface brightness, with little evidence for a clean separation into star cluster and galaxy populations at the faintest luminosities and surface brightnesses.

Classification of sea ice types with single-band (33.6 GHz) airborne passive microwave imagery

NASA Astrophysics Data System (ADS)

Eppler, Duane T.; Farmer, L. Dennis; Lohanick, Alan W.; Hoover, Mervyn

1986-09-01

During March 1983 extensive high-quality airborne passive Ka band (33.6 GHz) microwave imagery and coincident high-resolution aerial photography were obtained of ice along a 378-km flight line in the Beaufort Sea. Analysis of these data suggests that four classes of winter surfaces can be distinguished solely on the basis of 33.6-GHz brightness temperature: open water, frazil, old ice, and young/first-year ice. New ice (excluding frazil) and nilas display brightness temperatures that overlap the range of temperatures characteristic of old ice and, to a lesser extent, young/first-year ice. Scenes in which a new ice or nilas are present in appreciable amounts are subject to substantial errors in classification if static measures of Ka band radiometric brightness temperature alone are considered. Textural characteristics of nilas and new ice, however, differ significantly from textural features characteristic of other ice types and probably can be used with brightness temperature data to classify ice type in high-resolution single-band microwave images. In any case, open water is radiometrically the coldest surface observed in any scene. Lack of overlap between brightness temperatures characteristic of other surfaces indicates that estimates of the areal extent of open water based on only 33.6-GHz brightness temperatures are accurate.

Real time quantitative imaging for semiconductor crystal growth, control and characterization

NASA Technical Reports Server (NTRS)

Wargo, Michael J.

1991-01-01

A quantitative real time image processing system has been developed which can be software-reconfigured for semiconductor processing and characterization tasks. In thermal imager mode, 2D temperature distributions of semiconductor melt surfaces (900-1600 C) can be obtained with temperature and spatial resolutions better than 0.5 C and 0.5 mm, respectively, as demonstrated by analysis of melt surface thermal distributions. Temporal and spatial image processing techniques and multitasking computational capabilities convert such thermal imaging into a multimode sensor for crystal growth control. A second configuration of the image processing engine in conjunction with bright and dark field transmission optics is used to nonintrusively determine the microdistribution of free charge carriers and submicron sized crystalline defects in semiconductors. The IR absorption characteristics of wafers are determined with 10-micron spatial resolution and, after calibration, are converted into charge carrier density.

Pixel Color–Magnitude Diagram Analysis of the Brightest Cluster Galaxies in Dynamically Young and Old Clusters Abell 1139 and Abell 2589

NASA Astrophysics Data System (ADS)

Lee, Joon Hyeop; Oh, Sree; Jeong, Hyunjin; Yi, Sukyoung K.; Kyeong, Jaemann; Park, Byeong-Gon

2017-07-01

As a case study to understand the coevolution of Brightest Cluster Galaxies (BCGs) and their host clusters, we investigate the BCGs in dynamically young and old clusters Abell 1139 (A1139) and Abell 2589 (A2589). We analyze the pixel color–magnitude diagrams (pCMDs) using deep g- and r-band images, obtained from the Canada–France–Hawaii Telescope observations. After masking foreground/background objects and smoothing pixels in consideration of the observational seeing size, detailed pCMD features are compared between the two BCGs. (1) Although the overall shapes of the pCMDs are similar to those of typical early-type galaxies, the A2589-BCG tends to have redder mean pixel color and smaller pixel color deviation at given surface brightness than the A1139-BCG. (2) The mean pixel color distribution as a function of pixel surface brightness (pCMD backbone) indicates that the A2589-BCG formed a larger central body (∼2.0 kpc in radius) via major dry mergers at an early epoch than the A1139-BCG (a central body ∼1.3 kpc in radius), whereas they have grown commonly in subsequent minor mergers. (3) The spatial distributions of the pCMD outliers reveal that the A1139-BCG experienced considerable tidal events more recently than the A2589-BCG, whereas the A2589-BCG has an asymmetric compact core, possibly resulting from a major dry merger at an early epoch. (4) The A2589-BCG shows a very large faint-to-bright pixel number ratio, compared to early-type non-BCGs, whereas the ratio for the A1139-BCG is not distinctively large. These results are consistent with the idea that the BCG in the dynamically older cluster (A2589) formed earlier and is better relaxed.

Metre-size bright spots at the surface of comet 67P/Churyumov-Gerasimenko: Interpretation of OSIRIS data using laboratory experiments

NASA Astrophysics Data System (ADS)

Pommerol, Antoine; Thomas, Nicolas; Antonella Barucci, M.; Bertaux, Jean-Loup; Davidsson, Björn; Ramy El-Maarry, Mohamed; La Forgia, Fiorengela; Fornasier, Sonia; Gracia, Antonio; Groussin, Olivier; Jost, Bernhard; Keller, Horst Uwe; Kuehrt, Ekkehard; Marschall, Raphael; Massironi, Matteo; Motolla, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Poch, Olivier

2015-04-01

Since the beginning of Rosetta's orbital observations, over a hundred small bright spots have been identified in images returned by its OSIRIS NAC camera, in all types of morphological regions on the nucleus. Bright spots are found as clusters of several tens of individuals in the vicinity of cliffs, or isolated without clear structural relation to the surrounding terrain. They are however mostly observed in the areas of the nucleus currently receiving the lowest amount of insolation and some of the best examples appear completely surrounded by shadows. Their typical sizes are of the order of a few metres and they are often observed at the surfaces of boulders of larger dimension. The brightness of these spots is up to ten times the average brightness of the surrounding terrain and multi-spectral analyses show a significantly bluer spectrum over the 0.3-1µm range. Comparisons of images taken in September and November 2014 under similar illumination conditions do not show any significant change of these features. Analysis of the results of past and present laboratory experiments with H2O-ice/dust mixtures provide interesting insights about the nature and origin of the bright spots. In particular, recent sublimation experiments conducted at the University of Bern reproduce the spectro-photometric variability observed at the surface of the nucleus by sequences of formation and ejection of a mantle of refractory organic-rich dust at the surface of the icy material. The formation of hardened layers of ice by sintering/re-condensation below the uppermost dust layer can also have strong implications for both the photometric and mechanical properties of the subsurface layer. Based on the comparison between OSIRIS observations and laboratory results, our favoured interpretation of the observed features is that the bright spots are exposures of water ice, resulting from the removal of the uppermost layer of refractory dust that covers the rest of the nucleus. Some of the observations of clusters of bright spots are very indicative of a formation process, which involves the breakage and collapse of brittle layers of ice to form fields of large boulders, some of them showing bright spots on part of their surface. Some of the isolated spots observed elsewhere on the nucleus might as well have been formed by similar processes and then have been transported over large distances by multiple bounces. These surface exposures of water ice must be more recent than the last passage at perihelion, as they would rapidly sublimate at short heliocentric distance. The hypothesis formulated here will thus easily be tested as the comet approaches the Sun, by checking if and how fast the bright spots vanish and disappear.

A case study on large-scale dynamical influence on bright band using cloud radar during the Indian summer monsoon

NASA Astrophysics Data System (ADS)

Jha, Ambuj K.; Kalapureddy, M. C. R.; Devisetty, Hari Krishna; Deshpande, Sachin M.; Pandithurai, G.

2018-02-01

The present study is a first of its kind attempt in exploring the physical features (e.g., height, width, intensity, duration) of tropical Indian bright band using a Ka-band cloud radar under the influence of large-scale cyclonic circulation and attempts to explain the abrupt changes in bright band features, viz., rise in the bright band height by 430 m and deepening of the bright band by about 300 m observed at around 14:00 UTC on Sep 14, 2016, synoptically as well as locally. The study extends the utility of cloud radar to understand how the bright band features are associated with light precipitation, ranging from 0 to 1.5 mm/h. Our analysis of the precipitation event of Sep 14-15, 2016 shows that the bright band above (below) 3.7 km, thickness less (more) than 300 m can potentially lead to light drizzle of 0-0.25 mm/h (drizzle/light rain) at the surface. It is also seen that the cloud radar may be suitable for bright band study within light drizzle limits than under higher rain conditions. Further, the study illustrates that the bright band features can be determined using the polarimetric capability of the cloud radar. It is shown that an LDR value of - 22 dB can be associated with the top height of bright band in the Ka-band observations which is useful in the extraction of the bright band top height and its width. This study is useful for understanding the bright band phenomenon and could be potentially useful in establishing the bright band-surface rain relationship through the perspective of a cloud radar, which would be helpful to enhance the cloud radar-based quantitative estimates of precipitation.

A superior architecture of brightness enhancement for display backlighting

NASA Astrophysics Data System (ADS)

Dross, Oliver; Parkyn, William A.; Chaves, Julio; Falicoff, Waqidi; Miñano, Juan Carlos; Benitez, Pablo; Alvarez, Roberto

2006-08-01

Brightness enhancement of backlighting for displays is typically achieved via crossed micro prismatic films that are introduced between a backlight unit and a transmissive (LCD) display. Prismatic films let pass light only into a restricted angular range, while, in conjunction with other reflective elements below the backlight, all other light is recycled within the backlight unit, thereby increasing the backlight luminance. This design offers no free parameters to influence the resulting light distribution and suffers from insufficient stray light control. A novel strategy of light recycling is introduced, using a microlens array in conjunction with a hole array in a reflective surface, that can provide higher luminance, superior stray light control, and can be designed to meet almost any desired emission pattern. Similar strategies can be applied to mix light from different colored LEDs being mounted upside down to shine into a backlight unit.

Apocenter Glow in Eccentric Debris Disks: Implications for Fomalhaut and Epsilon Eridani

NASA Technical Reports Server (NTRS)

Pan, Margaret; Nesvold, Erika R.; Kuchner, Marc J.

2016-01-01

Debris disks often take the form of eccentric rings with azimuthal asymmetries in surface brightness. Such disks are often described as showing pericenter glow, an enhancement of the disk brightness in regions nearest the central star. At long wavelengths, however, the disk apocenters should appear brighter than their pericenters: in the long-wavelength limit, we find that the apocenter pericenter flux ratio scales as 1 + e for disk eccentricity e. We produce new models of this apocenter glow to explore its causes and wavelength dependence and study its potential as a probe of dust grain properties. Based on our models, we argue that several far-infrared and (sub)millimeter images of the Fomalhaut and Epsilon Eridani debris rings obtained with Herschel, JCMT, SHARC II, ALMA, and ATCA should be reinterpreted as suggestions or examples of apocenter glow. This reinterpretation yields new constraints on the disks dust grain properties and size distributions.

Synoptic maps constructed from brightness observations of Thomson scattering by heliospheric electrons

NASA Technical Reports Server (NTRS)

Hick, P.; Jackson, B.; Schwenn, R.

1991-01-01

Observations of the Thomson scattering brightness by electrons in the inner heliosphere provide a means of probing the heliospheric electron distributions. An extensive data base of Thomson scattering observations, stretching over many years, is available from the zodiacal light photometers on board the two Helios spacecraft. A survey of these data is in progress, presenting these scattering intensities in the form of synoptic maps for successive Carrington rotations. The Thomson scattering maps reflect conditions at typically several tenths of an astronomical unit from the sun. Some representative examples from the survey in comparison with other solar/heliospheric data, such as in situ observations of the Helios plasma experiment and synoptic maps constructed from magnetic field, H alpha and K-coronameter data are presented. The comparison will provide some information about the extension of solar surface features into the inner heliosphere.

X-ray morphological study of galaxy cluster catalogues

NASA Astrophysics Data System (ADS)

Democles, Jessica; Pierre, Marguerite; Arnaud, Monique

2016-07-01

Context : The intra-cluster medium distribution as probed by X-ray morphology based analysis gives good indication of the system dynamical state. In the race for the determination of precise scaling relations and understanding their scatter, the dynamical state offers valuable information. Method : We develop the analysis of the centroid-shift so that it can be applied to characterize galaxy cluster surveys such as the XXL survey or high redshift cluster samples. We use it together with the surface brightness concentration parameter and the offset between X-ray peak and brightest cluster galaxy in the context of the XXL bright cluster sample (Pacaud et al 2015) and a set of high redshift massive clusters detected by Planck and SPT and observed by both XMM-Newton and Chandra observatories. Results : Using the wide redshift coverage of the XXL sample, we see no trend between the dynamical state of the systems with the redshift.

RESPONSE OF GRANULATION TO SMALL-SCALE BRIGHT FEATURES IN THE QUIET SUN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andic, A.; Chae, J.; Goode, P. R.

2011-04-10

We detected 2.8 bright points (BPs) per Mm{sup 2} in the quiet Sun with the New Solar Telescope at Big Bear Solar Observatory, using the TiO 705.68 nm spectral line at an angular resolution {approx}0.''1 to obtain a 30 minute data sequence. Some BPs formed knots that were stable in time and influenced the properties of the granulation pattern around them. The observed granulation pattern within {approx}3'' of knots presents smaller granules than those observed in a normal granulation pattern, i.e., around the knots a suppressed convection is detected. Observed BPs covered {approx}5% of the solar surface and were notmore » homogeneously distributed. BPs had an average size of 0.''22, they were detectable for 4.28 minutes on average, and had an averaged contrast of 0.1% in the deep red TiO spectral line.« less

Three-dimensional spatial grouping affects estimates of the illuminant

NASA Astrophysics Data System (ADS)

Perkins, Kenneth R.; Schirillo, James A.

2003-12-01

The brightnesses (i.e., perceived luminance) of surfaces within a three-dimensional scene are contingent on both the luminances and the spatial arrangement of the surfaces. Observers viewed a CRT through a haploscope that presented simulated achromatic surfaces in three dimensions. They set a test patch to be ~33% more intense than a comparison patch to match the comparison patch in brightness, which is consistent with viewing a real scene with a simple lightning interpretation from which to estimate a different level of illumination in each depth plane. Randomly positioning each surface in either depth plane minimized any simple lighting interpretation, concomitantly reducing brightness differences to ~8.5%, although the immediate surrounds of the test and comparison patches continued to differ by a 5:1 luminance ratio.

Evaluations of carbon nanotube field emitters for electron microscopy

NASA Astrophysics Data System (ADS)

Nakahara, Hitoshi; Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi

2009-11-01

Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I- V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6×109 A/m 2 sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

Surface and atmosphere parameter maps from earth-orbiting radiometers

NASA Technical Reports Server (NTRS)

Gloersen, P.

1976-01-01

Earlier studies have shown that an earth-orbiting electrically scanned microwave radiometer (ESMR) is capable of inferring the extent, concentration, and age of sea ice; the extent, concentration, and thickness of lake ice; rainfall rates over oceans; surface wind speeds over open water; particle size distribution in the deep snow cover of continental ice sheets; and soil moisture content in unvegetated fields. Most other features of the surface of the earth and its atmosphere require multispectral imaging techniques to unscramble the combined contributions of the atmosphere and the surface. Multispectral extraction of surface parameters is analyzed on the basis of a pertinent equation in terms of the observed brightness temperature, the emissivity of the surface which depends on wavelength and various parameters, the sensible temperature of the surface, and the total atmospheric opacity which is also wavelength dependent. Implementation of the multispectral technique is examined. Properties of the surface of the earth and its atmosphere to be determined from a scanning multichannel microwave radiometer are tabulated.

Determination of cloud liquid water content using the SSM/I

NASA Technical Reports Server (NTRS)

Alishouse, John C.; Snider, Jack B.; Westwater, Ed R.; Swift, Calvin T.; Ruf, Christopher S.

1990-01-01

As part of a calibration/validation effort for the special sensor microwave/imager (SSM/I), coincident observations of SSM/I brightness temperatures and surface-based observations of cloud liquid water were obtained. These observations were used to validate initial algorithms and to derive an improved algorithm. The initial algorithms were divided into latitudinal-, seasonal-, and surface-type zones. It was found that these initial algorithms, which were of the D-matrix type, did not yield sufficiently accurate results. The surface-based measurements of channels were investigated; however, the 85V channel was excluded because of excessive noise. It was found that there is no significant correlation between the SSM/I brightness temperatures and the surface-based cloud liquid water determination when the background surface is land or snow. A high correlation was found between brightness temperatures and ground-based measurements over the ocean.

Calculations of microwave brightness temperature of rough soil surfaces: Bare field

NASA Technical Reports Server (NTRS)

Mo, T.; Schmugge, T. J.; Wang, J. R.

1985-01-01

A model for simulating the brightness temperatures of soils with rough surfaces is developed. The surface emissivity of the soil media is obtained by the integration of the bistatic scattering coefficients for rough surfaces. The roughness of a soil surface is characterized by two parameters, the surface height standard deviation sigma and its horizontal correlation length l. The model calculations are compared to the measured angular variations of the polarized brightness temperatures at both 1.4 GHz and 5 GHz frequences. A nonlinear least-squares fitting method is used to obtain the values of delta and l that best characterize the surface roughness. The effect of shadowing is incorporated by introducing a function S(theta), which represents the probability that a point on a rough surface is not shadowed by other parts of the surface. The model results for the horizontal polarization are in excellent agreement with the data. However, for the vertical polarization, some discrepancies exist between the calculations and data, particularly at the 1.4 GHz frequency. Possible causes of the discrepancy are discussed.

The intrinsic three-dimensional shape of galactic bars

NASA Astrophysics Data System (ADS)

Méndez-Abreu, J.; Costantin, L.; Aguerri, J. A. L.; de Lorenzo-Cáceres, A.; Corsini, E. M.

2018-06-01

We present the first statistical study on the intrinsic three-dimensional (3D) shape of a sample of 83 galactic bars extracted from the CALIFA survey. We use the galaXYZ code to derive the bar intrinsic shape with a statistical approach. The method uses only the geometric information (ellipticities and position angles) of bars and discs obtained from a multi-component photometric decomposition of the galaxy surface-brightness distributions. We find that bars are predominantly prolate-triaxial ellipsoids (68%), with a small fraction of oblate-triaxial ellipsoids (32%). The typical flattening (intrinsic C/A semiaxis ratio) of the bars in our sample is 0.34, which matches well the typical intrinsic flattening of stellar discs at these galaxy masses. We demonstrate that, for prolate-triaxial bars, the intrinsic shape of bars depends on the galaxy Hubble type and stellar mass (bars in massive S0 galaxies are thicker and more circular than those in less massive spirals). The bar intrinsic shape correlates with bulge, disc, and bar parameters. In particular with the bulge-to-total (B/T) luminosity ratio, disc g - r color, and central surface brightness of the bar, confirming the tight link between bars and their host galaxies. Combining the probability distributions of the intrinsic shape of bulges and bars in our sample we show that 52% (16%) of bulges are thicker (flatter) than the surrounding bar at 1σ level. We suggest that these percentages might be representative of the fraction of classical and disc-like bulges in our sample, respectively.

HiRISE observations of new impact craters exposing Martian ground ice

USGS Publications Warehouse

Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.; Mellon, Michael T.; Kennedy, Megan R.; Daubar, Ingrid J.; Saper, Lee

2014-01-01

Twenty small new impact craters or clusters have been observed to excavate bright material inferred to be ice at mid and high latitudes on Mars. In the northern hemisphere, the craters are widely distributed geographically and occur at latitudes as low as 39°N. Stability modeling suggests that this ice distribution requires a long-term average atmospheric water vapor content around 25 precipitable microns, more than double the present value, which is consistent with the expected effect of recent orbital variations. Alternatively, near-surface humidity could be higher than expected for current column abundances if water vapor is not well-mixed with atmospheric CO2, or the vapor pressure at the ice table could be lower due to salts. Ice in and around the craters remains visibly bright for months to years, indicating that it is clean ice rather than ice-cemented regolith. Although some clean ice may be produced by the impact process, it is likely that the original ground ice was excess ice (exceeding dry soil pore space) in many cases. Observations of the craters suggest small-scale heterogeneities in this excess ice. The origin of such ice is uncertain. Ice lens formation by migration of thin films of liquid is most consistent with local heterogeneity in ice content and common surface boulders, but in some cases nearby thermokarst landforms suggest large amounts of excess ice that may be best explained by a degraded ice sheet.

Difference in Dwarf Galaxy Surface Brightness Profiles as a Function of Environment

NASA Astrophysics Data System (ADS)

Lee, Youngdae; Park, Hong Soo; Kim, Sang Chul; Moon, Dae-Sik; Lee, Jae-Joon; Kim, Dong-Jin; Cha, Sang-Mok

2018-05-01

We investigate surface brightness profiles (SBPs) of dwarf galaxies in field, group, and cluster environments. With deep BV I images from the Korea Microlensing Telescope Network Supernova Program, SBPs of 38 dwarfs in the NGC 2784 group are fitted by a single-exponential or double-exponential model. We find that 53% of the dwarfs are fitted with single-exponential profiles (“Type I”), while 47% of the dwarfs show double-exponential profiles; 37% of all dwarfs have smaller sizes for the outer part than the inner part (“Type II”), while 10% have a larger outer than inner part (“Type III”). We compare these results with those in the field and in the Virgo cluster, where the SBP types of 102 field dwarfs are compiled from a previous study and the SBP types of 375 cluster dwarfs are measured using SDSS r-band images. As a result, the distributions of SBP types are different in the three environments. Common SBP types for the field, the NGC 2784 group, and the Virgo cluster are Type II, Type I and II, and Type I and III profiles, respectively. After comparing the sizes of dwarfs in different environments, we suggest that since the sizes of some dwarfs are changed due to environmental effects, SBP types are capable of being transformed and the distributions of SBP types in the three environments are different. We discuss possible environmental mechanisms for the transformation of SBP types. Based on data collected at KMTNet Telescopes and SDSS.

Characterization of Mineralogy Across Vesta

NASA Technical Reports Server (NTRS)

De Sanctis, M. C.; Ammannito, E.; Capria, M. T.; Capaccioni, F.; Carraro, F.; Fonte, S.; Frigeri, A.; Magni, G.; Marchi, S.; Palomba, E.;

Photometric Studies of GEO Orbital Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Rodriquez-Cowardin, Heather M.; Barker, Ed; Abercromby, Kira J.; Foreman, Gary; Horstman, Matt

2009-01-01

The photometric signature of a debris object can be useful in determining what the physical characteristics of a piece of debris are. We report on optical observations in multiple filters of debris at geosynchronous Earth orbit (GEO). Our sample is taken from GEO objects discovered in a survey with the University of Michigan's 0.6-m aperture Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope), and then followed up in real-time with the Cerro Tololo Inter- American Observatory (CTIO) 0.9-m for orbits and photometry. Our goal is to determine 6 parameter orbits and measure colors for all objects fainter than R=15th magnitude that are discovered in the MODEST survey. At this magnitude the distribution of observed angular rates changes significantly from that of brighter objects. There are two objectives: 1. Estimate the orbital distribution of objects selected on the basis of two observational criteria: brightness (magnitude) and angular rates. 2. Obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. What is the faint debris likely to be? More than 90 calibrated sequences of R-B-V-I-R magnitudes for a sample of 50 objects have been obtained with the CTIO 0.9-m. For objects that do not show large brightness variations, the colors are largely redder than solar in both B-R and R-I. The width of the color distribution may be intrinsic to the nature of the surfaces, but also could be that we are seeing irregularly shaped objects and measuring the colors at different times with just one telescope. For a smaller sample of objects we have observed with synchronized CCD cameras on the two telescopes. The CTIO 0.9-m observes in B, and MODEST in R. The CCD cameras are electronically linked together so that the start time and duration of observations are the same to better than 50 milliseconds. Thus the B-R color is a true measure of the surface of the debris piece facing the telescopes for that observation. Any change in color reflects a real change in the debris surface. We will compare our observations with models and laboratory measurements of selected surfaces.

The distribution of particulate material on Mars

NASA Technical Reports Server (NTRS)

Christensen, Philip R.

1991-01-01

The surface materials on Mars were extensively studied using a variety of spacecraft and Earth-based remote sensing observations. These measurements include: (1) diurnal thermal measurements, used to determine average particle size, rock abundance, and the presence of crusts; (2) radar observations, used to estimate the surface slope distributions, wavelength scale roughness, and density; (3) radio emission observations, used to estimate subsurface density; (4) broadband albedo measurements, used to study the time variation of surface brightness and dust deposition and removal; and (5) color observations, used to infer composition, mixing, and the presence of crusts. Remote sensing observations generally require some degree of modeling to interpret, making them more difficult to interpret than direct observations from the surface. They do, however, provide a means for examining the surface properties over the entire planet and a means of sampling varying depths within the regolith. Albedo and color observations only indicate the properties of the upper-most few microns, but are very sensitive to thin, sometimes emphemeral dust coatings. Thermal observations sample the upper skin depth, generally 2 to 10 cm. Rock abundance measurements give an indirect indication of surface mantling, where the absence of rocks suggests mantles of several meters. Finally, radar and radio emission data can penetrate several meters into the surface, providing an estimate of subsurface density and roughness.

Three-Photon Luminescence of Gold Nanorods Excited by 1040 nm Femtosecond Laser for High Contrast Tissue and In Vivo Imaging

NASA Astrophysics Data System (ADS)

Wang, Shaowei; Zhao, Xinyuan; Zhang, Hequn; Cai, Fuhong; Qian, Jun

2016-01-01

Gold Nanorods (GNRs) with tunable aspect ratios can strongly absorb and scatter light in the NIR region due to their localized surface plasmon resonance (LSPR) property, and have been demonstrated to exhibit strong plasmon enhanced multiphoton luminescence (MPL) with brightness many times stronger than the conventional organic chromophores. In this study, we synthesized GNRs with longitudinal LSPR peak at 1036 nm to match our home-built light source 1040 nm femtosecond laser, which locates in the “optical window” where the tissue absorbs relatively little light. PEGylated GNRs with great biocompatibility were intravenously injected through the tail vein into mice. Excited by 1040 nm laser, the GNRs exhibit bright three-photon luminescence (3PL) signals while circulating in the blood vessels. The use of GNRs as bright contrast agents for 3PL imaging of mouse ear blood vessels in vivo was demonstrated. And GNRs targeted in tissues can be excited by 1040 nm laser and could be clearly visualized with no autofluorescence background. These results indicated that 3PL of GNRs is very promising for deep in vivo bioimaging and assessing the distribution of GNRs in tissues with high contrast.

Analysis of Voyager images of Europa - plasma bombardment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, R.E.; Nelson, M.L.; Nccord, T.B.

1988-09-01

Voyager-derived data on the albedos of Europa are presently photometrically corrected and converted into average, single-scattering form, in order to analyze them as a function of angular distance from the apex of orbital motion. A hypothesized magnetospheric modification of the Europa surface is confirmed by the UV absorption found in the 0.35-micron filter data; this absorption directly correlates with the longitudinal ion implantation distribution in both terrain types. A red spectrum is found in both terrain types as well, and is found to be constant across the surface. A uniform increase is noted in the dark terrain absorption over thatmore » in the bright terrain. 43 references.« less

Analysis of Saturn's Thermal Emission at 2.2-cm Wavelength: Spatial Distribution of Ammonia Vapor

NASA Technical Reports Server (NTRS)

Laraia, A. L.; Ingersoll, A. P.; Janssen, Michael A.; Gulkis, Samuel; Oyafuso, Fabiano A.; Allison, Michael D.

2013-01-01

This work focuses on determining the latitudinal structure of ammonia vapor in Saturn's cloud layer near 1.5 bars using the brightness temperature maps derived from the Cassini RADAR (Elachi et al., 2004) instrument, which works in a passive mode to measure thermal emission from Saturn at 2.2-cm wavelength. We perform an analysis of five brightness temperature maps that span epochs from 2005 to 2011, which are presented in a companion paper by Janssen et al. (2013a, this issue). The brightness temperature maps are representative of the spatial distribution of ammonia vapor, since ammonia gas is the only effective opacity source in Saturn's atmosphere at 2.2-cm wavelength. Relatively high brightness temperatures indicate relatively low ammonia relative humidity (RH), and vice versa. We compare the observed brightness temperatures to brightness temperatures computed using the Juno atmospheric microwave radiative transfer (JAMRT) program which includes both the means to calculate a tropospheric atmosphere model for Saturn and the means to carry out radiative transfer calculations at microwave frequencies. The reference atmosphere to which we compare has a 3x solar deep mixing ratio of ammonia (we use 1.352x10(exp -4) for the solar mixing ratio of ammonia vapor relative to H2; see Atreya, 2010) and is fully saturated above its cloud base. The maps are comprised of residual brightness temperatures-observed brightness temperature minus the model brightness temperature of the saturated atmosphere.

Brightness masking is modulated by disparity structure.

PubMed

Pelekanos, Vassilis; Ban, Hiroshi; Welchman, Andrew E

2015-05-01

The luminance contrast at the borders of a surface strongly influences surface's apparent brightness, as demonstrated by a number of classic visual illusions. Such phenomena are compatible with a propagation mechanism believed to spread contrast information from borders to the interior. This process is disrupted by masking, where the perceived brightness of a target is reduced by the brief presentation of a mask (Paradiso & Nakayama, 1991), but the exact visual stage that this happens remains unclear. In the present study, we examined whether brightness masking occurs at a monocular-, or a binocular-level of the visual hierarchy. We used backward masking, whereby a briefly presented target stimulus is disrupted by a mask coming soon afterwards, to show that brightness masking is affected by binocular stages of the visual processing. We manipulated the 3-D configurations (slant direction) of the target and mask and measured the differential disruption that masking causes on brightness estimation. We found that the masking effect was weaker when stimuli had a different slant. We suggest that brightness masking is partly mediated by mid-level neuronal mechanisms, at a stage where binocular disparity edge structure has been extracted. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Simulated X-ray galaxy clusters at the virial radius: Slopes of the gas density, temperature and surface brightness profiles

NASA Astrophysics Data System (ADS)

Roncarelli, M.; Ettori, S.; Dolag, K.; Moscardini, L.; Borgani, S.; Murante, G.

2006-12-01

Using a set of hydrodynamical simulations of nine galaxy clusters with masses in the range 1.5 × 1014 < Mvir < 3.4 × 1015Msolar, we have studied the density, temperature and X-ray surface brightness profiles of the intracluster medium in the regions around the virial radius. We have analysed the profiles in the radial range well above the cluster core, the physics of which are still unclear and matter of tension between simulated and observed properties, and up to the virial radius and beyond, where present observations are unable to provide any constraints. We have modelled the radial profiles between 0.3R200 and 3R200 with power laws with one index, two indexes and a rolling index. The simulated temperature and [0.5-2] keV surface brightness profiles well reproduce the observed behaviours outside the core. The shape of all these profiles in the radial range considered depends mainly on the activity of the gravitational collapse, with no significant difference among models including extraphysics. The profiles steepen in the outskirts, with the slope of the power-law fit that changes from -2.5 to -3.4 in the gas density, from -0.5 to -1.8 in the gas temperature and from -3.5 to -5.0 in the X-ray soft surface brightness. We predict that the gas density, temperature and [0.5-2] keV surface brightness values at R200 are, on average, 0.05, 0.60, 0.008 times the measured values at 0.3R200. At 2R200, these values decrease by an order of magnitude in the gas density and surface brightness, by a factor of 2 in the temperature, putting stringent limits on the detectable properties of the intracluster-medium (ICM) in the virial regions.

New UBVRI colour distributions in E-type galaxies . I. The data

NASA Astrophysics Data System (ADS)

Idiart, T. P.; Michard, R.; de Freitas Pacheco, J. A.

2002-01-01

New colour distributions have been derived from wide field UBVRI frames for 36 northern bright elliptical galaxies and a few lenticulars. The classical linear representations of colours against log r were derived, with some improvements in the accuracy of the zero point colours and of the gradients. The radial range of significant measurements was enlarged both towards the galaxy center and towards the outskirts of each object. Thus, the ``central colours'', integrated within a radius of 3\\arcsec, and the ``outermost colours'' averaged near the muV =24 surface brightness could also be obtained. Some typical deviations of colour profiles from linearity are described. Colour-colour relations of interest are presented. Very tight correlations are found between the U-V colour and the Mg2 line-index, measured either at the Galaxian center or at the effective radius. Based in part on observations collected at the Observatoire de Haute-Provence. Tables 9-11 plus detailed tables for each object are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/30

Loop models of low coronal structures observed by the Normal Incidence X-Ray Telescope (NIXT)

NASA Technical Reports Server (NTRS)

Peres, G.; Reale, F.; Golub, L.

1994-01-01

The X-ray pictures obtained with the Normal Incidence X-Ray Telescope (NIXT), apart from the ubiquitous coronal loops well known from previous X-ray observations, show a new and peculiar morphology: in many active regions there are wide and apparently low-lying areas of intense emission which resemble H alpha plages. By means of hydrostatic models of coronal arches, we analyze the distribution of temperature, density, emission measure, and plasma emissivity in the spectral band to which NIXT is sensitive, and we show that the above morphology can be explained by the characteristics of high pressure loops having a thin region of high surface brightness at the base. We therefore propose that this finding might help to identify high-pressure X-ray emitting coronal regions in NIXT images, and it is in principle applicable to any imaging instrument which has high sensitivity to 10(exp 4) - 10(exp 6) K plasma within a narrow coronal-temperature passband. As a more general result of this study, we propose that the comparison of NIXT observations with models of stationary loops might provide a new diagnostic: the determination of the loop plasma pressure from measurements of brightness distribution along the loop.

WHERE ARE THE FOSSILS OF THE FIRST GALAXIES? II. TRUE FOSSILS, GHOST HALOS, AND THE MISSING BRIGHT SATELLITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bovill, Mia S.; Ricotti, Massimo, E-mail: msbovill@astro.umd.edu

We use a new set of cold dark matter simulations of the local universe to investigate the distribution of fossils of primordial dwarf galaxies within and around the Milky Way. Throughout, we build upon previous results showing agreement between the observed stellar properties of a subset of the ultra-faint dwarfs and our simulated fossils. Here, we show that fossils of the first galaxies have galactocentric distributions and cumulative luminosity functions consistent with observations. In our model, we predict {approx}300 luminous satellites orbiting the Milky Way, 50%-70% of which are well-preserved fossils. Within the Milky Way virial radius, the majority ofmore » these fossils have luminosities L{sub V} < 10{sup 6} L{sub sun}. Despite our multidimensional agreement with observations at low masses and luminosities, the primordial model produces an overabundance of bright dwarf satellites (L{sub V} > 10{sup 4} L{sub sun}) with respect to observations where observations are nearly complete. The 'bright satellite problem' is most evident in the outer parts of the Milky Way. We estimate that, although relatively bright, the primordial stellar populations are very diffuse, producing a population with surface brightnesses below surveys' detection limits, and are easily stripped by tidal forces. Although we cannot yet present unmistakable evidence for the existence of the fossils of first galaxies in the Local Group, the results of our studies suggest observational strategies that may demonstrate their existence: (1) the detection of 'ghost halos' of primordial stars around isolated dwarfs would prove that stars formed in minihalos (M < 10{sup 8} M{sub sun}) before reionization and strongly suggest that at least a fraction of the ultra-faint dwarfs are fossils of the first galaxies; and (2) the existence of a yet unknown population of {approx}150 Milky Way ultra-faints with half-light radii r{sub hl} {approx} 100-1000 pc and luminosities L{sub V} < 10{sup 4} L{sub sun}, detectable by future deep surveys. These undetected dwarfs would have the mass-to-light ratios, stellar velocity dispersions, and metallicities predicted in this work.« less

The Photometric Properties of a Vast Stellar Substructure in the Outskirts of M33

NASA Astrophysics Data System (ADS)

McConnachie, Alan W.; Ferguson, Annette M. N.; Irwin, Michael J.; Dubinski, John; Widrow, Lawrence M.; Dotter, Aaron; Ibata, Rodrigo; Lewis, Geraint F.

2010-11-01

We have surveyed approximately 40 deg2 surrounding M33 with Canada-France-Hawaii Telescope MegaCam/MegaPrime in the g and i filters out to a maximum projected radius from this galaxy of 50 kpc, as part of the Pan-Andromeda Archaeological Survey (PAndAS). Our observations are deep enough to resolve the top ~4 mag of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations of this feature are consistent with an old population with lang[Fe/H]rang ~ -1.6 dex and an interquartile range in metallicity of ~0.5 dex. We construct a surface brightness map of M33 that traces this feature to μ V ~= 33 mag arcsec-2. At these low surface brightness levels, the structure extends to projected radii of ~40 kpc from the center of M33 in both the northwest and southeast quadrants of the galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns with the orientation of the H I disk warp. We calculate a lower limit to the integrated luminosity of the structure of -12.7 ± 0.5 mag, comparable to a bright dwarf galaxy such as Fornax or Andromeda II and slightly less than 1% of the total luminosity of M33. Further, we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the H I disk that occurs at similar azimuth to the warp in H I. The data also hint at a low-level, extended stellar component at larger radius that may be an M33 halo component. We revisit studies of M33 and its stellar populations in light of these new results and discuss possible formation scenarios for the vast stellar structure. Our favored model is that of the tidal disruption of M33 in its orbit around M31.

Effects of cloud size and cloud particles on satellite-observed reflected brightness

NASA Technical Reports Server (NTRS)

Reynolds, D. W.; Mckee, T. B.; Danielson, K. S.

1978-01-01

Satellite observations allowed obtaining data on the visible brightness of cumulus clouds over South Park, Colorado, while aircraft observations were made in cloud to obtain the drop size distributions and liquid water content of the cloud. Attention is focused on evaluating the relationship between cloud brightness, horizontal dimension, and internal microphysical structure. A Monte Carlo cloud model for finite clouds was run using different distributions of drop sizes and numbers, while varying the cloud depth and width to determine how theory would predict what the satellite would view from its given location in space. Comparison of these results to the satellite observed reflectances is presented. Theoretical results are found to be in good agreement with observations. For clouds of optical thickness between 20 and 60, monitoring cloud brightness changes in clouds of uniform depth and variable width gives adequate information about a cloud's liquid water content. A cloud having a 10:1 width to depth ratio is almost reaching its maximum brightness for a specified optical thickness.

Correlations among the properties of galaxies found in a blind HI survey, which also have SDSS optical data

NASA Astrophysics Data System (ADS)

Garcia-Appadoo, D. A.; West, A. A.; Dalcanton, J. J.; Cortese, L.; Disney, M. J.

2009-03-01

We have used the Parkes Multibeam system and the Sloan Digital Sky Survey to assemble a sample of 195 galaxies selected originally from their HI signature to avoid biases against unevolved or low surface brightness objects. For each source nine intrinsic properties are measured homogeneously, as well as inclination and an optical spectrum. The sample, which should be almost entirely free of either misidentification or confusion, includes a wide diversity of galaxies ranging from inchoate, low surface brightness dwarfs to giant spirals. Despite this diversity there are five clear correlations among their properties. They include a common dynamical mass-to-light ratio within their optical radii, a correlation between surface brightness and luminosity and a common HI surface density. Such correlation should provide strong constrains on models of galaxy formation and evolution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zemcov, M.; Cooray, A.; Bock, J.

We have observed four massive galaxy clusters with the SPIRE instrument on the Herschel Space Observatory and measure a deficit of surface brightness within their central region after removing detected sources. We simulate the effects of instrumental sensitivity and resolution, the source population, and the lensing effect of the clusters to estimate the shape and amplitude of the deficit. The amplitude of the central deficit is a strong function of the surface density and flux distribution of the background sources. We find that for the current best fitting faint end number counts, and excellent lensing models, the most likely amplitudemore » of the central deficit is the full intensity of the cosmic infrared background (CIB). Our measurement leads to a lower limit to the integrated total intensity of the CIB of I{sub 250{mu}m}>0.69{sub -0.03}{sup +0.03}(stat.){sub -0.06}{sup +0.11}(sys.) MJy sr{sup -1}, with more CIB possible from both low-redshift sources and from sources within the target clusters. It should be possible to observe this effect in existing high angular resolution data at other wavelengths where the CIB is bright, which would allow tests of models of the faint source component of the CIB.« less

Radial Distribution of X-Ray Point Sources Near the Galactic Center

NASA Astrophysics Data System (ADS)

Hong, Jae Sub; van den Berg, Maureen; Grindlay, Jonathan E.; Laycock, Silas

2009-11-01

We present the log N-log S and spatial distributions of X-ray point sources in seven Galactic bulge (GB) fields within 4° from the Galactic center (GC). We compare the properties of 1159 X-ray point sources discovered in our deep (100 ks) Chandra observations of three low extinction Window fields near the GC with the X-ray sources in the other GB fields centered around Sgr B2, Sgr C, the Arches Cluster, and Sgr A* using Chandra archival data. To reduce the systematic errors induced by the uncertain X-ray spectra of the sources coupled with field-and-distance-dependent extinction, we classify the X-ray sources using quantile analysis and estimate their fluxes accordingly. The result indicates that the GB X-ray population is highly concentrated at the center, more heavily than the stellar distribution models. It extends out to more than 1fdg4 from the GC, and the projected density follows an empirical radial relation inversely proportional to the offset from the GC. We also compare the total X-ray and infrared surface brightness using the Chandra and Spitzer observations of the regions. The radial distribution of the total infrared surface brightness from the 3.6 band μm images appears to resemble the radial distribution of the X-ray point sources better than that predicted by the stellar distribution models. Assuming a simple power-law model for the X-ray spectra, the closer to the GC the intrinsically harder the X-ray spectra appear, but adding an iron emission line at 6.7 keV in the model allows the spectra of the GB X-ray sources to be largely consistent across the region. This implies that the majority of these GB X-ray sources can be of the same or similar type. Their X-ray luminosity and spectral properties support the idea that the most likely candidate is magnetic cataclysmic variables (CVs), primarily intermediate polars (IPs). Their observed number density is also consistent with the majority being IPs, provided the relative CV to star density in the GB is not smaller than the value in the local solar neighborhood.

Impact craters on Venus: An overview from Magellan observations

NASA Technical Reports Server (NTRS)

Schaber, G. G.; Strom, R. G.; Moore, H. J.; Soderblom, L. A.; Kirk, R. L.; Chadwick, D. J.; Dawson, D. D.; Gaddis, L. R.; Boyce, J. M.; Russell, J.

1992-01-01

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a database describing 842 craters on 89 percent of the planet's surface mapped through orbit 2578 (the craters range in diameter from 1.5 to 280 km). We have studied the distribution, size-frequency, morphology, and geology of these craters both in aggregate and, for some craters, in more detail. We have found the following: (1) the spatial distribution of craters is highly uniform; (2) the size-density distribution of craters with diameters greater than or equal to 35 km is consistent with a 'production' population having a surprisingly young age of about 0.5 Ga (based on the estimated population of Venus-crossing asteroids); (3) the spectrum of crater modification differs greatly from that on other planets--62 percent of all craters are pristine, only 4 percent volcanically embayed, and the remainder affected by tectonism, but none are severely and progressively depleted based on size-density distribution extrapolated from larger craters; (4) large craters have a progression of morphologies generally similar to those on other planets, but small craters are typically irregular or multiple rather than bowl shaped; (5) diffuse radar-bright or -dark features surround some craters, and about 370 similar diffuse 'splotches' with no central crater are observed whose size-density distribution is similar to that of small craters; and (6) other features unique to Venus include radar-bright or -dark parabolic arcs opening westward and extensive outflows originating in crater ejecta.

An Automatic Cloud Mask Algorithm Based on Time Series of MODIS Measurements

NASA Technical Reports Server (NTRS)

Lyapustin, Alexei; Wang, Yujie; Frey, R.

2008-01-01

Quality of aerosol retrievals and atmospheric correction depends strongly on accuracy of the cloud mask (CM) algorithm. The heritage CM algorithms developed for AVHRR and MODIS use the latest sensor measurements of spectral reflectance and brightness temperature and perform processing at the pixel level. The algorithms are threshold-based and empirically tuned. They don't explicitly address the classical problem of cloud search, wherein the baseline clear-skies scene is defined for comparison. Here, we report on a new CM algorithm which explicitly builds and maintains a reference clear-skies image of the surface (refcm) using a time series of MODIS measurements. The new algorithm, developed as part of the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm for MODIS, relies on fact that clear-skies images of the same surface area have a common textural pattern, defined by the surface topography, boundaries of rivers and lakes, distribution of soils and vegetation etc. This pattern changes slowly given the daily rate of global Earth observations, whereas clouds introduce high-frequency random disturbances. Under clear skies, consecutive gridded images of the same surface area have a high covariance, whereas in presence of clouds covariance is usually low. This idea is central to initialization of refcm which is used to derive cloud mask in combination with spectral and brightness temperature tests. The refcm is continuously updated with the latest clear-skies MODIS measurements, thus adapting to seasonal and rapid surface changes. The algorithm is enhanced by an internal dynamic land-water-snow classification coupled with a surface change mask. An initial comparison shows that the new algorithm offers the potential to perform better than the MODIS MOD35 cloud mask in situations where the land surface is changing rapidly, and over Earth regions covered by snow and ice.

The nucleus of Comet Borrelly: A study of morphology and surface brightness

USGS Publications Warehouse

Oberst, J.; Howington-Kraus, E.; Kirk, R.; Soderblom, L.; Buratti, B.; Hicks, M.; Nelson, R.; Britt, D.

2004-01-01

Stereo images obtained during the DS1 flyby were analyzed to derive a topographic model for the nucleus of Comet 19P/Borrelly for morphologic and photometric studies. The elongated nucleus has an overall concave shape, resembling a peanut, with the lower end tilted towards the camera. The bimodal character of surface-slopes and curvatures support the idea that the nucleus is a gravitational aggregate, consisting of two fragments in contact. Our photometric modeling suggests that topographic shading effects on Borrelly's surface are very minor (<10%) at the given resolution of the terrain model. Instead, albedo effects are thought to dominate Borrelly's large variations in surface brightness. With 90% of the visible surface having single scattering albedos between 0.008 and 0.024, Borrelly is confirmed to be among the darkest of the known Solar System objects. Photometrically corrected images emphasize that the nucleus has distinct, contiguous terrains covered with either bright or dark, smooth or mottled materials. Also, mapping of the changes in surface brightness with phase angle suggests that terrain roughness at subpixel scale is not uniform over the nucleus. High surface roughness is noted in particular near the transition between the upper and lower end of the nucleus, as well as near the presumed source region of Borrelly's main jets. Borrelly's surface is complex and characterized by distinct types of materials that have different compositional and/or physical properties. ?? 2003 Elsevier Inc. All rights reserved.

Thin Sea-Ice Thickness as Inferred from Passive Microwave and In Situ Observations

NASA Technical Reports Server (NTRS)

Naoki, Kazuhiro; Ukita, Jinro; Nishio, Fumihiko; Nakayama, Masashige; Comiso, Josefino C.; Gasiewski, Al

2007-01-01

Since microwave radiometric signals from sea-ice strongly reflect physical conditions of a layer near the ice surface, a relationship of brightness temperature with thickness is possible especially during the early stages of ice growth. Sea ice is most saline during formation stage and as the salinity decreases with time while at the same time the thickness of the sea ice increases, a corresponding change in the dielectric properties and hence the brightness temperature may occur. This study examines the extent to which the relationships of thickness with brightness temperature (and with emissivity) hold for thin sea-ice, approximately less than 0.2 -0.3 m, using near concurrent measurements of sea-ice thickness in the Sea of Okhotsk from a ship and passive microwave brightness temperature data from an over-flying aircraft. The results show that the brightness temperature and emissivity increase with ice thickness for the frequency range of 10-37 GHz. The relationship is more pronounced at lower frequencies and at the horizontal polarization. We also established an empirical relationship between ice thickness and salinity in the layer near the ice surface from a field experiment, which qualitatively support the idea that changes in the near-surface brine characteristics contribute to the observed thickness-brightness temperature/emissivity relationship. Our results suggest that for thin ice, passive microwave radiometric signals contain, ice thickness information which can be utilized in polar process studies.

A Method of Visualizing Three-Dimensional Distribution of Yeast in Bread Dough

NASA Astrophysics Data System (ADS)

Maeda, Tatsurou; Do, Gab-Soo; Sugiyama, Junichi; Oguchi, Kosei; Shiraga, Seizaburou; Ueda, Mitsuyoshi; Takeya, Koji; Endo, Shigeru

A novel technique was developed to monitor the change in three-dimensional (3D) distribution of yeast in frozen bread dough samples in accordance with the progress of mixing process. Application of a surface engineering technology allowed the identification of yeast in bread dough by bonding EGFP (Enhanced Green Fluorescent Protein) to the surface of yeast cells. The fluorescent yeast (a biomarker) was recognized as bright spots at the wavelength of 520 nm. A Micro-Slicer Image Processing System (MSIPS) with a fluorescence microscope was utilized to acquire cross-sectional images of frozen dough samples sliced at intervals of 1 μm. A set of successive two-dimensional images was reconstructed to analyze 3D distribution of yeast. Samples were taken from each of four normal mixing stages (i.e., pick up, clean up, development, and final stages) and also from over mixing stage. In the pick up stage yeast distribution was uneven with local areas of dense yeast. As the mixing progressed from clean up to final stages, the yeast became more evenly distributed throughout the dough sample. However, the uniformity in yeast distribution was lost in the over mixing stage possibly due to the breakdown of gluten structure within the dough sample.

49 CFR 213.113 - Defective rails.

Code of Federal Regulations, 2010 CFR

2010-10-01

... smooth, bright, or dark, round or oval surface substantially at a right angle to the length of the rail... in the head of the rail as a smooth, bright, or dark surface progressing until substantially at a... head, and extending into or through it. A crack or rust streak may show under the head close to the web...

49 CFR 213.113 - Defective rails.

Code of Federal Regulations, 2011 CFR

2011-10-01

... smooth, bright, or dark, round or oval surface substantially at a right angle to the length of the rail... in the head of the rail as a smooth, bright, or dark surface progressing until substantially at a... head, and extending into or through it. A crack or rust streak may show under the head close to the web...

49 CFR 213.113 - Defective rails.

Code of Federal Regulations, 2012 CFR

2012-10-01

... smooth, bright, or dark, round or oval surface substantially at a right angle to the length of the rail... in the head of the rail as a smooth, bright, or dark surface progressing until substantially at a... head, and extending into or through it. A crack or rust streak may show under the head close to the web...

49 CFR 213.113 - Defective rails.

Code of Federal Regulations, 2013 CFR

2013-10-01

... smooth, bright, or dark, round or oval surface substantially at a right angle to the length of the rail... in the head of the rail as a smooth, bright, or dark surface progressing until substantially at a... head, and extending into or through it. A crack or rust streak may show under the head close to the web...

Earth Observations

NASA Image and Video Library

2010-07-23

ISS024-E-009404 (23 July 2010) --- This photo taken from the International Space Station on July 23, 2010, shows the Gulf of Mexico oil spill as part of ongoing observations of the region. When this image was taken, three months after the explosion on the Deepwater Horizon oil rig, the leak had been plugged for eight days. Water surfaces appear bright and land surfaces appear dark in the image. The stark contrast is due to sun glint, in which the sun is reflected brilliantly off all water surfaces back towards the astronaut observer on board the station. The sun glint reveals various features in the Gulf of Mexico, especially sheens of oil as packets of long bright streaks seen on the left side of the image. Sediments carried by the Mississippi River have a light-yellow coloration in this image, with distinct margins between plumes that likely mark tidal pulses of river water into the Gulf of Mexico. A boat wake cuts across one of the oil packets at image lower left. Daily National Oceanic and Atmospheric Administration (NOAA) maps of oil distribution show predicted heavier and lighter oil movement near the Gulf coastline. The maps show that on the day this image was taken, the north edge of the ?oiled? zone was expected to bank up against the delta. The observed spread of the surface oil in the approximately 100 days since the explosion highlights the connectivity between the deepwater areas and coastlines of the Gulf of Mexico.

Rutgers zodiacal light experiment on OSO-6

NASA Technical Reports Server (NTRS)

Carroll, B.

1975-01-01

A detector was placed in a slowly spinning wheel on OSO-6 whose axis was perpendicular to the line drawn to the sun, to measure the surface brightness and polarization at all elongations from the immediate neighborhood of the sun to the anti-solar point. Different wavelength settings and polarizations were calculated from the known order of magnitude brightness of the zodiacal light. The measuring sequence was arranged to give longer integration times for the regions of lower surface brightness. Three types of analysis to which the data on OSO-6 were subjected are outlined; (1) photometry, (2) colorimetry and (3) polarimetry.

Recent collecting reveals new state records and the extremes in the distribution of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), in the United States

Treesearch

Steven J. Seybold; Tom W. Coleman; Paul L. Dallara; Norman L. Dart; Andrew D. Graves; Lee A. Pederson; Sven-Erik. Spichiger

2012-01-01

The walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae, sensu Wood 2007), was first described from specimens collected in 1896 in Grant Co., New Mexico (Blackman 1928). Bright (1981) and Wood & Bright (1992) reported a distribution for P. juglandis that included Arizona, California, and New Mexico...

Single quantum dot tracking reveals the impact of nanoparticle surface on intracellular state.

PubMed

Zahid, Mohammad U; Ma, Liang; Lim, Sung Jun; Smith, Andrew M

2018-05-08

Inefficient delivery of macromolecules and nanoparticles to intracellular targets is a major bottleneck in drug delivery, genetic engineering, and molecular imaging. Here we apply live-cell single-quantum-dot imaging and tracking to analyze and classify nanoparticle states after intracellular delivery. By merging trajectory diffusion parameters with brightness measurements, multidimensional analysis reveals distinct and heterogeneous populations that are indistinguishable using single parameters alone. We derive new quantitative metrics of particle loading, cluster distribution, and vesicular release in single cells, and evaluate intracellular nanoparticles with diverse surfaces following osmotic delivery. Surface properties have a major impact on cell uptake, but little impact on the absolute cytoplasmic numbers. A key outcome is that stable zwitterionic surfaces yield uniform cytosolic behavior, ideal for imaging agents. We anticipate that this combination of quantum dots and single-particle tracking can be widely applied to design and optimize next-generation imaging probes, nanoparticle therapeutics, and biologics.

Surface Relief of Mapping

NASA Astrophysics Data System (ADS)

Costa, Manuel F.; Almeida, Jose B.

1989-02-01

We will describe in this communication a noncont act method of measuring surface profile, it does not require any surface preparation, and it can be used with a very large range of surfaces from highly reflecting to non reflecting ones and as complex as textile surfaces. This method is reasonably immune to dispersion and diffraction, which usually make very difficult the application of non contact profilometry methods to a wide range of materials and situations, namely on quality control systems in industrial production lines. The method is based on the horizontal shift of the bright spot on a horizontal surface when this is illuminated with an oblique beam and moved vertically. in order to make the profilometry the sample is swept by an oblique light beam and the bright spot position is compared with a reference position. The bright spot must be as small as possible, particularly in very irregular surfaces; so the light beam diameter must be as small as possible and the incidence angle must not be too small. The sensivity of a system based on this method will be given, mostly, by the reception optical system.

Pupil size reflects the focus of feature-based attention.

PubMed

Binda, Paola; Pereverzeva, Maria; Murray, Scott O

2014-12-15

We measured pupil size in adult human subjects while they selectively attended to one of two surfaces, bright and dark, defined by coherently moving dots. The two surfaces were presented at the same location; therefore, subjects could select the cued surface only on the basis of its features. With no luminance change in the stimulus, we find that pupil size was smaller when the bright surface was attended and larger when the dark surface was attended: an effect of feature-based (or surface-based) attention. With the same surfaces at nonoverlapping locations, we find a similar effect of spatial attention. The pupil size modulation cannot be accounted for by differences in eye position and by other variables known to affect pupil size such as task difficulty, accommodation, or the mere anticipation (imagery) of bright/dark stimuli. We conclude that pupil size reflects not just luminance or cognitive state, but the interaction between the two: it reflects which luminance level in the visual scene is relevant for the task at hand. Copyright © 2014 the American Physiological Society.

SPIDERMAN: an open-source code to model phase curves and secondary eclipses

NASA Astrophysics Data System (ADS)

Louden, Tom; Kreidberg, Laura

2018-06-01

We present SPIDERMAN (Secondary eclipse and Phase curve Integrator for 2D tempERature MAppiNg), a fast code for calculating exoplanet phase curves and secondary eclipses with arbitrary surface brightness distributions in two dimensions. Using a geometrical algorithm, the code solves exactly the area of sections of the disc of the planet that are occulted by the star. The code is written in C with a user-friendly Python interface, and is optimized to run quickly, with no loss in numerical precision. Approximately 1000 models can be generated per second in typical use, making Markov Chain Monte Carlo analyses practicable. The modular nature of the code allows easy comparison of the effect of multiple different brightness distributions for the data set. As a test case, we apply the code to archival data on the phase curve of WASP-43b using a physically motivated analytical model for the two-dimensional brightness map. The model provides a good fit to the data; however, it overpredicts the temperature of the nightside. We speculate that this could be due to the presence of clouds on the nightside of the planet, or additional reflected light from the dayside. When testing a simple cloud model, we find that the best-fitting model has a geometric albedo of 0.32 ± 0.02 and does not require a hot nightside. We also test for variation of the map parameters as a function of wavelength and find no statistically significant correlations. SPIDERMAN is available for download at https://github.com/tomlouden/spiderman.

Surface and Atmospheric Contributions to Passive Microwave Brightness Temperatures

NASA Technical Reports Server (NTRS)

Jackson, Gail Skofronick; Johnson, Benjamin T.

2010-01-01

Physically-based passive microwave precipitation retrieval algorithms require a set of relationships between satellite observed brightness temperatures (TB) and the physical state of the underlying atmosphere and surface. These relationships are typically non-linear, such that inversions are ill-posed especially over variable land surfaces. In order to better understand these relationships, this work presents a theoretical analysis using brightness temperature weighting functions to quantify the percentage of the TB resulting from absorption/emission/reflection from the surface, absorption/emission/scattering by liquid and frozen hydrometeors in the cloud, the emission from atmospheric water vapor, and other contributors. The results are presented for frequencies from 10 to 874 GHz and for several individual precipitation profiles as well as for three cloud resolving model simulations of falling snow. As expected, low frequency channels (<89 GHz) respond to liquid hydrometeors and the surface, while the higher frequency channels become increasingly sensitive to ice hydrometeors and the water vapor sounding channels react to water vapor in the atmosphere. Low emissivity surfaces (water and snow-covered land) permit energy downwelling from clouds to be reflected at the surface thereby increasing the percentage of the TB resulting from the hydrometeors. The slant path at a 53deg viewing angle increases the hydrometeor contributions relative to nadir viewing channels and show sensitivity to surface polarization effects. The TB percentage information presented in this paper answers questions about the relative contributions to the brightness temperatures and provides a key piece of information required to develop and improve precipitation retrievals over land surfaces.

Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

NASA Astrophysics Data System (ADS)

Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

2018-01-01

Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

Mapping Geological Units on Mars by Analyzing the Spectral Properties of the Surface from the Mars-Express High Resolution Stereo Camera (HRSC)

NASA Astrophysics Data System (ADS)

Combe, J.; Adams, J. B.; McCord, T. B.

2006-12-01

Geological units at the surface of Mars can be investigated through the analysis of spatial changes of both its composition and its superficial structural properties. The color images provided by the High Resolution Stereo Camera (HRSC) are a multispectral dataset with an unprecedented high spatial resolution. We focused this study on the western chasmas of Valles Marineris with the neighboring plateau. Using the four-wavelength spectra of HRSC, the two types of surface color units (bright red and dark bluish material) plus a shade/shadow component can explain most of the variations [1]. An objective is to provide maps of the relative abundances that are independent of shade [2]. The spectral shape of the shade spectrum is calculated from the data. Then, Spectral Mixture Analysis of the two main materials and shade is performed. The shade gives us indications about variations in the surface roughness in the context of the mixtures of spectral/mineralogical materials. For mapping the different geological units at the surface at high spatial resolution, a correspondence between the color and the mineralogy is needed, aided by direct and more precise identifications of the composition of Mars. The joint analysis of HRSC and results from the OMEGA imaging spectrometer makes the most of their respective abilities [1]. Ferric oxides are present in bright red materials both in the chasmas and on the plateau [1] and they are often mixed with dark materials identified as basalts containing pyroxenes [4]. In Valles Marineris, salt deposits (bright) have been reported by using OMEGA [3], along with ferric oxides [4, 5] that appear relatively dark. The detailed spatial distribution of these materials is a key to understand the geology. Examples will be presented. [1] McCord T. B., et al. 2006, JGR, submitted. [2] Adams J. B. And Gillespie A. R., 2006, Cambridge University Press, 362 pp. [3] Le Mouelic S. et al., 2006, LPSC #1409. [4] Gendrin et al. (2005), LPSC #1858. [5] Gendrin A. et al., 2005, Science, 307, 1587-1591. [6] Le Deit et al., 2006, LPSC #2115.

Modelling dust rings in early-type galaxies through a sequence of radiative transfer simulations and 2D image fitting

NASA Astrophysics Data System (ADS)

Bonfini, P.; González-Martín, O.; Fritz, J.; Bitsakis, T.; Bruzual, G.; Cervantes Sodi, B.

2018-07-01

A large fraction of early-type galaxies (ETGs) hosts prominent dust features, and central dust rings are arguably the most interesting among them. We present here `Lord of the Rings', a new methodology which allows to integrate the extinction by dust rings in a 2D-fittingmodelling of the surface brightness distribution. Our pipeline acts in two steps, first using the surface-fitting software GALFIT to determine the unabsorbed stellar emission, and then adopting the radiative transfer code SKIRT to apply dust extinction. We apply our technique to NGC 4552 and NGC 4494, two nearby ETGs. We show that the extinction by a dust ring can mimic, in a surface brightness profile, a central point source (e.g. an unresolved nuclear stellar cluster or an active galactic nucleus; AGN) superimposed to a `core' (i.e. a central flattening of the stellar light commonly observed in massive ETGs). We discuss how properly accounting for dust features is of paramount importance to derive correct fluxes, especially for low-luminosity AGNs (LLAGNs). We suggest that the geometries of dust features are strictly connected with how relaxed is the gravitational potential, i.e. with the evolutionary stage of the host galaxy. Additionally, we find hints that the dust mass contained in the ring relates to the AGN activity.

Modelling dust rings in early-type galaxies through a sequence of radiative transfer simulations and 2D image fitting

NASA Astrophysics Data System (ADS)

Bonfini, P.; González-Martín, O.; Fritz, J.; Bitsakis, T.; Bruzual, G.; Sodi, B. Cervantes

2018-05-01

A large fraction of early-type galaxies (ETGs) host prominent dust features, and central dust rings are arguably the most interesting among them. We present here `Lord Of The Rings' (LOTR), a new methodology which allows to integrate the extinction by dust rings in a 2D fitting modelling of the surface brightness distribution. Our pipeline acts in two steps, first using the surface fitting software GALFIT to determine the unabsorbed stellar emission, and then adopting the radiative transfer code SKIRT to apply dust extinction. We apply our technique to NGC 4552 and NGC 4494, two nearby ETGs. We show that the extinction by a dust ring can mimic, in a surface brightness profile, a central point source (e.g. an unresolved nuclear stellar cluster or an active galactic nucleus; AGN) superimposed to a `core' (i.e. a central flattening of the stellar light commonly observed in massive ETGs). We discuss how properly accounting for dust features is of paramount importance to derive correct fluxes especially for low luminosity AGNs (LLAGNs). We suggest that the geometries of dust features are strictly connected with how relaxed is the gravitational potential, i.e. with the evolutionary stage of the host galaxy. Additionally, we find hints that the dust mass contained in the ring relates to the AGN activity.

Precise on-machine extraction of the surface normal vector using an eddy current sensor array

NASA Astrophysics Data System (ADS)

Wang, Yongqing; Lian, Meng; Liu, Haibo; Ying, Yangwei; Sheng, Xianjun

2016-11-01

To satisfy the requirements of on-machine measurement of the surface normal during complex surface manufacturing, a highly robust normal vector extraction method using an Eddy current (EC) displacement sensor array is developed, the output of which is almost unaffected by surface brightness, machining coolant and environmental noise. A precise normal vector extraction model based on a triangular-distributed EC sensor array is first established. Calibration of the effects of object surface inclination and coupling interference on measurement results, and the relative position of EC sensors, is involved. A novel apparatus employing three EC sensors and a force transducer was designed, which can be easily integrated into the computer numerical control (CNC) machine tool spindle and/or robot terminal execution. Finally, to test the validity and practicability of the proposed method, typical experiments were conducted with specified testing pieces using the developed approach and system, such as an inclined plane and cylindrical and spherical surfaces.

The HR 4796A Debris System: Discovery of Extensive Exo-ring Dust Material

NASA Astrophysics Data System (ADS)

Schneider, Glenn; Debes, John H.; Grady, Carol A.; Gáspár, Andras; Henning, Thomas; Hines, Dean C.; Kuchner, Marc J.; Perrin, Marshall; Wisniewski, John P.

2018-02-01

The optically and IR-bright and starlight-scattering HR 4796A ringlike debris disk is one of the most- (and best-) studied exoplanetary debris systems. The presence of a yet-undetected planet has been inferred (or suggested) from the narrow width and inner/outer truncation radii of its r = 1.″05 (77 au) debris ring. We present new, highly sensitive Hubble Space Telescope (HST) visible-light images of the HR 4796A circumstellar debris system and its environment over a very wide range of stellocentric angles from 0.″32 (23 au) to ≈15″ (1100 au). These very high-contrast images were obtained with the Space Telescope Imaging Spectrograph (STIS) using six-roll PSF template–subtracted coronagraphy suppressing the primary light of HR 4796A, with three image-plane occulters, and simultaneously subtracting the background light from its close angular proximity M2.5V companion. The resulting images unambiguously reveal the debris ring embedded within a much larger, morphologically complex, and biaxially asymmetric exo-ring scattering structure. These images at visible wavelengths are sensitive to and map the spatial distribution, brightness, and radial surface density of micron-size particles over 5 dex in surface brightness. These particles in the exo-ring environment may be unbound from the system and interacting with the local ISM. Herein, we present a new morphological and photometric view of the larger-than-prior-seen HR 4796A exoplanetary debris system with sensitivity to small particles at stellocentric distances an order of magnitude greater than has previously been observed.

The night sky brightness at McDonald Observatory

NASA Technical Reports Server (NTRS)

Kalinowski, J. K.; Roosen, R. G.; Brandt, J. C.

1975-01-01

Baseline observations of the night sky brightness in B and V are presented for McDonald Observatory. In agreement with earlier work by Elvey and Rudnick (1937) and Elvey (1943), significant night-to-night and same-night variations in sky brightness are found. Possible causes for these variations are discussed. The largest variation in sky brightness found during a single night is approximately a factor of two, a value which corresponds to a factor-of-four variation in airglow brightness. The data are used to comment on the accuracy of previously published surface photometry of M 81.

A map of the day-night contrast of the extrasolar planet HD 189733b.

PubMed

Knutson, Heather A; Charbonneau, David; Allen, Lori E; Fortney, Jonathan J; Agol, Eric; Cowan, Nicolas B; Showman, Adam P; Cooper, Curtis S; Megeath, S Thomas

2007-05-10

'Hot Jupiter' extrasolar planets are expected to be tidally locked because they are close (<0.05 astronomical units, where 1 au is the average Sun-Earth distance) to their parent stars, resulting in permanent daysides and nightsides. By observing systems where the planet and star periodically eclipse each other, several groups have been able to estimate the temperatures of the daysides of these planets. A key question is whether the atmosphere is able to transport the energy incident upon the dayside to the nightside, which will determine the temperature at different points on the planet's surface. Here we report observations of HD 189733, the closest of these eclipsing planetary systems, over half an orbital period, from which we can construct a 'map' of the distribution of temperatures. We detected the increase in brightness as the dayside of the planet rotated into view. We estimate a minimum brightness temperature of 973 +/- 33 K and a maximum brightness temperature of 1,212 +/- 11 K at a wavelength of 8 mum, indicating that energy from the irradiated dayside is efficiently redistributed throughout the atmosphere, in contrast to a recent claim for another hot Jupiter. Our data indicate that the peak hemisphere-integrated brightness occurs 16 +/- 6 degrees before opposition, corresponding to a hotspot shifted east of the substellar point. The secondary eclipse (when the planet moves behind the star) occurs 120 +/- 24 s later than predicted, which may indicate a slightly eccentric orbit.

DIFFUSE Ly{alpha} EMITTING HALOS: A GENERIC PROPERTY OF HIGH-REDSHIFT STAR-FORMING GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steidel, Charles C.; Bogosavljevic, Milan; Shapley, Alice E.

2011-08-01

Using a sample of 92 UV continuum-selected, spectroscopically identified galaxies with (z) = 2.65, all of which have been imaged in the Ly{alpha} line with extremely deep narrow-band imaging, we examine galaxy Ly{alpha} emission profiles to very faint surface brightness limits. The galaxy sample is representative of spectroscopic samples of Lyman break galaxies (LBGs) at similar redshifts in terms of apparent magnitude, UV luminosity, inferred extinction, and star formation rate and was assembled without regard to Ly{alpha} emission properties. Approximately 45% (55%) of the galaxy spectra have Ly{alpha} appearing in net absorption (emission), with {approx_equal} 20% satisfying commonly used criteriamore » for the identification of 'Ly{alpha} emitters' (LAEs; W{sub 0}(Ly{alpha}) {>=} 20 A). We use extremely deep stacks of rest-UV continuum and continuum-subtracted Ly{alpha} images to show that all sub-samples exhibit diffuse Ly{alpha} emission to radii of at least 10'' ({approx}80 physical kpc). The characteristic exponential scale lengths for Ly{alpha} line emission exceed that of the {lambda}{sub 0} = 1220 A UV continuum light by factors of {approx}5-10. The surface brightness profiles of Ly{alpha} emission are strongly suppressed relative to the UV continuum light in the inner few kpc, by amounts that are tightly correlated with the galaxies' observed spectral morphology; however, all galaxy sub-subsamples, including that of galaxies for which Ly{alpha} appears in net absorption in the spectra, exhibit qualitatively similar diffuse Ly{alpha} emission halos. Accounting for the extended Ly{alpha} emission halos, which generally would not be detected in the slit spectra of individual objects or with typical narrow-band Ly{alpha} imaging, increases the total Ly{alpha} flux (and rest equivalent width W{sub 0}(Ly{alpha})) by an average factor of {approx}5, and by a much larger factor for the 80% of LBGs not classified as LAEs. We argue that most, if not all, of the observed Ly{alpha} emission in the diffuse halos originates in the galaxy H II regions but is scattered in our direction by H I gas in the galaxy's circum-galactic medium. The overall intensity of Ly{alpha} halos, but not the surface brightness distribution, is strongly correlated with the emission observed in the central {approx}1''-more luminous halos are observed for galaxies with stronger central Ly{alpha} emission. We show that whether or not a galaxy is classified as a giant 'Ly{alpha} blob' (LAB) depends sensitively on the Ly{alpha} surface brightness threshold reached by an observation. Accounting for diffuse Ly{alpha} halos, all LBGs would be LABs if surveys were sensitive to 10 times lower Ly{alpha} surface brightness thresholds; similarly, essentially all LBGs would qualify as LAEs.« less

Subwavelenght Light Localization in Nanostructured Surfaces

NASA Astrophysics Data System (ADS)

Coello, V.; Wang, S.; Siqueiros, J.; Bozhevolnyi, S. I.

Using a photon scanning tunneling microscope, we studied near field optical images obtained with a surface plasmon polariton (SPP) being resonantly excited along a surface with a random introduced roughness. The SPP intensity field distributions showed an optical enhancement in the form of round bright spots up to 5 times larger than the background signal. We also show an artificially fabricated SPP curved micromirror along with the corresponding near-field optical image. The recorded optical signal exhibited an enhancement up to 10 times larger than the background, which has been generated for the first time in a controlled form. A numerical simulation of a parabolic micromirror based on isotropic pointlike scatterers is analyzed and compared with experimental results. The potential of creating microstructures able to control SPP optical field enhancement is showed in a novel numerically simulated microcavity for SPP's.

Geologic Structures in Crater Walls on Vesta

NASA Technical Reports Server (NTRS)

Mittlefehldt, David W.; Beck, A. W.; Ammannito, E.; Carsenty, U.; DeSanctis, M. C.; LeCorre, L.; McCoy, T. J.; Reddy, V.; Schroeder, S. E.

2012-01-01

The Framing Camera (FC) on the Dawn spacecraft has imaged most of the illuminated surface of Vesta with a resolution of apporpx. 20 m/pixel through different wavelength filters that allow for identification of lithologic units. The Visible and Infrared Mapping Spectrometer (VIR) has imaged the surface at lower spatial resolution but high spectral resolution from 0.25 to 5 micron that allows for detailed mineralogical interpretation. The FC has imaged geologic structures in the walls of fresh craters and on scarps on the margin of the Rheasilvia basin that consist of cliff-forming, competent units, either as blocks or semi-continuous layers, hundreds of m to km below the rims. Different units have different albedos, FC color ratios and VIR spectral characteristics, and different units can be juxtaposed in individual craters. We will describe different examples of these competent units and present preliminary interpretations of the structures. A common occurrence is of blocks several hundred m in size of high albedo (bright) and low albedo (dark) materials protruding from crater walls. In many examples, dark material deposits lie below coherent bright material blocks. In FC Clementine color ratios, bright material is green indicating deeper 1 m pyroxene absorption band. VIR spectra show these to have deeper and wider 1 and 2 micron pyroxene absorption bands than the average vestan surface. The associated dark material has subdued pyroxene absorption features compared to the average vestan surface. Some dark material deposits are consistent with mixtures of HED materials with carbonaceous chondrites. This would indicate that some dark material deposits in crater walls are megabreccia blocks. The same would hold for bright material blocks found above them. Thus, these are not intact crustal units. Marcia crater is atypical in that the dark material forms a semi-continuous, thin layer immediately below bright material. Bright material occurs as one or more layers. In one region, there is an apparent angular unconformity between the bright material and the dark material where bright material layers appear to be truncated against the underlying dark layer. One crater within the Rheasilvia basin contains two distinct types of bright materials outcropping on its walls, one like that found elsewhere on Vesta and the other an anomalous block 200 m across. This material has the highest albedo; almost twice that of the vestan average. Unlike all other bright materials, this block has a subdued 1 micron pyroxene absorption band in FC color ratios. These data indicate that this block represents a distinct vestan lithology that is rarely exposed.

Dark Lakes on a Bright Landscape

NASA Image and Video Library

2013-10-23

Ultracold hydrocarbon lakes and seas dark shapes near the north pole of Saturn moon Titan can be seen embedded in some kind of bright surface material in this infrared mosaic from NASA Cassini mission.

The Influence of Microphysical Cloud Parameterization on Microwave Brightness Temperatures

NASA Technical Reports Server (NTRS)

Skofronick-Jackson, Gail M.; Gasiewski, Albin J.; Wang, James R.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The microphysical parameterization of clouds and rain-cells plays a central role in atmospheric forward radiative transfer models used in calculating passive microwave brightness temperatures. The absorption and scattering properties of a hydrometeor-laden atmosphere are governed by particle phase, size distribution, aggregate density., shape, and dielectric constant. This study identifies the sensitivity of brightness temperatures with respect to the microphysical cloud parameterization. Cloud parameterizations for wideband (6-410 GHz observations of baseline brightness temperatures were studied for four evolutionary stages of an oceanic convective storm using a five-phase hydrometeor model in a planar-stratified scattering-based radiative transfer model. Five other microphysical cloud parameterizations were compared to the baseline calculations to evaluate brightness temperature sensitivity to gross changes in the hydrometeor size distributions and the ice-air-water ratios in the frozen or partly frozen phase. The comparison shows that, enlarging the rain drop size or adding water to the partly Frozen hydrometeor mix warms brightness temperatures by up to .55 K at 6 GHz. The cooling signature caused by ice scattering intensifies with increasing ice concentrations and at higher frequencies. An additional comparison to measured Convection and Moisture LA Experiment (CAMEX 3) brightness temperatures shows that in general all but, two parameterizations produce calculated T(sub B)'s that fall within the observed clear-air minima and maxima. The exceptions are for parameterizations that, enhance the scattering characteristics of frozen hydrometeors.

A statistical examination of Nimbus 7 SMMR data and remote sensing of sea surface temperature, liquid water content in the atmosphere and surfaces wind speed

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Wang, I.; Chang, A. T. C.; Gloersen, P.

1982-01-01

Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) brightness temperature measurements over the global oceans have been examined with the help of statistical and empirical techniques. Such analyses show that zonal averages of brightness temperature measured by SMMR, over the oceans, on a large scale are primarily influenced by the water vapor in the atmosphere. Liquid water in the clouds and rain, which has a much smaller spatial and temporal scale, contributes substantially to the variability of the SMMR measurements within the latitudinal zones. The surface wind not only increases the surface emissivity but through its interactions with the atmosphere produces correlations, in the SMMR brightness temperature data, that have significant meteorological implications. It is found that a simple meteorological model can explain the general characteristics of the SMMR data. With the help of this model methods to infer over the global oceans, the surface temperature, liquid water content in the atmosphere, and surface wind speed are developed. Monthly mean estimates of the sea surface temperature and surface winds are compared with the ship measurements. Estimates of liquid water content in the atmosphere are consistent with earlier satellite measurements.

Titan Surface Temperatures as Measured by Cassini CIRS

NASA Technical Reports Server (NTRS)

Jennings, Donald E.; Flasar, F.M.; Kunde, V.G.; Nixon, C.A.; Romani, P.N.; Samuelson, R.E.; Coustenis, A.; Courtin, R.

2009-01-01

Thermal radiation from the surface of Titan reaches space through a spectral window of low opacity at 19-microns wavelength. This radiance gives a measure of the brightness temperature of the surface. Composite Infrared Spectrometer' (CIRS) observations from Cassini during its first four years at Saturn have permitted latitude mapping of zonally averaged surface temperatures. The measurements are corrected for atmospheric opacity using the dependence of radiance on emission angle. With the more complete latitude coverage and much larger dataset of CIRS we have improved upon the original results from Voyager IRIS. CIRS measures the equatorial surface brightness temperature to be 93.7+/-0.6 K, the same as the temperature measured at the Huygens landing site. The surface brightness temperature decreases by 2 K toward the south pole and by 3 K toward the north pole. The drop in surface temperature between equator and north pole implies a 50% decrease in methane saturation vapor pressure and relative humidity; this may help explain the large northern lakes. The H2 mole fraction is derived as a by-product of our analysis and agrees with previous results. Evidence of seasonal variation in surface and atmospheric temperatures is emerging from CIRS measurements over the Cassini mission.

Visualization and quantification of three-dimensional distribution of yeast in bread dough.

PubMed

Maeda, Tatsuro; DO, Gab-Soo; Sugiyama, Junichi; Araki, Tetsuya; Tsuta, Mizuki; Shiraga, Seizaburo; Ueda, Mitsuyoshi; Yamada, Masaharu; Takeya, Koji; Sagara, Yasuyuki

2009-07-01

A three-dimensional (3-D) bio-imaging technique was developed for visualizing and quantifying the 3-D distribution of yeast in frozen bread dough samples in accordance with the progress of the mixing process of the samples, applying cell-surface engineering to the surfaces of the yeast cells. The fluorescent yeast was recognized as bright spots at the wavelength of 520 nm. Frozen dough samples were sliced at intervals of 1 microm by an micro-slicer image processing system (MSIPS) equipped with a fluorescence microscope for acquiring cross-sectional images of the samples. A set of successive two-dimensional images was reconstructed to analyze the 3-D distribution of the yeast. The average shortest distance between centroids of enhanced green fluorescent protein (EGFP) yeasts was 10.7 microm at the pick-up stage, 9.7 microm at the clean-up stage, 9.0 microm at the final stage, and 10.2 microm at the over-mixing stage. The results indicated that the distribution of the yeast cells was the most uniform in the dough of white bread at the final stage, while the heterogeneous distribution at the over-mixing stage was possibly due to the destruction of the gluten network structure within the samples.

Determining Size Distribution at the Phoenix Landing Site

NASA Astrophysics Data System (ADS)

Mason, E. L.; Lemmon, M. T.

2016-12-01

Dust aerosols play a crucial role in determining atmospheric radiative heating on Mars through absorption and scattering of sunlight. How dust scatters and absorbs light is dependent on size, shape, composition, and quantity. Optical properties of the dust have been well constrained in the visible and near infrared wavelengths using various methods [Wolff et al. 2009, Lemmon et al. 2004]. In addition, the dust is nonspherical, and irregular shapes have shown to work well in determining effective particle size [Pollack et al. 1977]. Variance of the size distribution is less constrained but constitutes an important parameter in fully describing the dust. The Phoenix Lander's Surface Stereo Imager performed several cross-sky brightness surveys to determine the size distribution and scattering properties of dust in the wavelength range of 400 to 1000 nm. In combination with a single-layer radiative transfer model, these surveys can be used to help constrain variance of the size distribution. We will present a discussion of seasonal size distribution as it pertains to the Phoenix landing site.

Optical image of a cometary nucleus: 1980 flyby of Comet Encke

NASA Technical Reports Server (NTRS)

Wells, W. C.; Benson, R. S.; Anderson, A. D.; Gal, G.

1974-01-01

The feasibility was investigated of obtaining optical images of a cometary nucleus via a flyby of Comet Encke. A physical model of the dust cloud surrounding the nucleus was developed by using available physical data and theoretical knowledge of cometary physics. Using this model and a Mie scattering code, calculations were made of the absolute surface brightness of the dust in the line of sight of the on-board camera and the relative surface brightness of the dust compared to the nucleus. The brightness was calculated as a function of heliocentric distance and for different phase angles (sun-comet-spacecraft angle).

High-Resolution Radar Imagery of Mars

NASA Astrophysics Data System (ADS)

Harmon, John K.; Nolan, M. C.

2009-09-01

We present high-resolution radar images of Mars obtained during the 2005 and 2007 oppositions. The images were constructed from long-code delay-Doppler observations made with the Arecibo S-band (13-cm) radar. The average image resolution of 3 km represented a better than order-of-magnitude improvement over pre-upgrade Arecibo imagery of the planet. Images of depolarized reflectivity (an indicator primarily of wavelength-scale surface roughness) show the same bright volcanic flow features seen in earlier imagery, but with much finer detail. A new image of the Elysium region shows fine detail in the radar-bright channels of Athabasca Vallis, Marte Vallis, and Grjota Vallis. The new images of Tharsis and Olympus Mons also show a complex array of radar-bright and radar-dark features. Southern Amazonis exhibits some of the most complex and puzzling radar-bright structure on the planet. Another curiosity is the Chryse/Xanthe/Channels region, where we find some radar-bright features in or adjacent to fluvial chaos structures. Chryse/Xanthe is also the only region of Mars showing radar-bright craters (which are rare on Mars but common on the Moon and Mercury). We also obtained the first delay-Doppler image showing the enhanced backscatter from the residual south polar ice cap. In addition to the depolarized imagery, we were able to make the first delay-Doppler images of the circular polarization ratio (an important diagnostic for surface roughness texture). We find that vast areas of the radar-bright volcanic regions have polarization ratios close to unity. Such high ratios are rare for terrestrial lava flows and only seen for extremely blocky surfaces giving high levels of multiple scattering.

Characterization and Correction of Aquarius Long Term Calibration Drift Using On-Earth Brightness Temperature Refernces

NASA Technical Reports Server (NTRS)

Brown, Shannon; Misra, Sidharth

2013-01-01

The Aquarius/SAC-D mission was launched on June 10, 2011 from Vandenberg Air Force Base. Aquarius consists of an L-band radiometer and scatterometer intended to provide global maps of sea surface salinity. One of the main mission objectives is to provide monthly global salinity maps for climate studies of ocean circulation, surface evaporation and precipitation, air/sea interactions and other processes. Therefore, it is critical that any spatial or temporal systematic biases be characterized and corrected. One of the main mission requirements is to measure salinity with an accuracy of 0.2 psu on montly time scales which requires a brightness temperature stability of about 0.1K, which is a challenging requirement for the radiometer. A secondary use of the Aquarius data is for soil moisture applications, which requires brightness temperature stability at the warmer end of the brightness temperature dynamic range. Soon after launch, time variable drifts were observed in the Aquarius data compared to in-situ data from ARGO and models for the ocean surface salinity. These drifts could arise from a number of sources, including the various components of the retrieval algorithm, such as the correction for direct and reflected galactic emission, or from the instrument brightness temperature calibration. If arising from the brightness temperature calibration, they could have gain and offset components. It is critical that the nature of the drifts be understood before a suitable correction can be implemented. This paper describes the approach that was used to detect and characterize the components of the drift that were in the brightness temperature calibration using on-Earth reference targets that were independent of the ocean model.

On the AU Microscopii debris disk. Density profiles, grain properties, and dust dynamics

NASA Astrophysics Data System (ADS)

Augereau, J.-C.; Beust, H.

2006-09-01

Context: . AU Mic is a young M-type star surrounded by an edge-on optically thin debris disk that shares many common observational properties with the disk around β Pictoris. In particular, the scattered light surface brightness profile falls off as ˜ r-5 outside 120 AU for β Pictoris and 35 AU for AU Mic. In both cases, the disk color rises as the distance increases beyond these reference radii. Aims: . In this paper, we present the first comprehensive analysis of the AU Mic disk properties since the system was resolved by Kalas et al. (2004, Science, 303, 1990). We explore whether the dynamical model, which successfully reproduces the β Pictoris brightness profile (e.g., Augereau et al. 2001, A&A, 370, 447), could apply to AU Mic. Methods: . We calculate the surface density profile of the AU Mic disk by performing the inversion of the near-IR and visible scattered light brightness profiles measured by Liu (2004, Science, 305, 1442) and Krist et al. (2005, AJ, 129, 1008), respectively. We discuss the grain properties by analysing the blue color of the disk in the visible (Krist et al. 2005) and by fitting the disk spectral energy distribution. Finally, we evaluate the radiation and wind forces on the grains. The impact of the recurrent X-ray and UV-flares on the dust dynamics is also discussed. Results: . We show that irrespective of the mean scattering asymmetry factor of the grains, most of the emission arises from an asymmetric, collisionally-dominated region that peaks close to the surface brightness break around 35 AU. The elementary scatterers at visible wavelengths are found to be sub-micronic, but the inferred size distribution underestimates the number of large grains, resulting in sub-millimeter emissions that are too low compared to the observations. From our inversion procedure, we find that the V- to H-band scattering cross sections ratio increases outside 40 AU, in line with the observed color gradient of the disk. This behavior is expected if the grains have not been produced locally, but placed in orbits of high eccentricity by a size-dependent pressure force, resulting in a paucity of large grains beyond the outer edge of the parent bodies' disk. Because of the low luminosity of AU Mic, radiation pressure is inefficient to diffuse the smallest grains in the outer disk, even when the flares are taken into account. Conversely, we show that a standard, solar-like stellar wind generates a pressure force onto the dust particles that behaves much like a radiation pressure force. With an assumed dot{M} ≃ 3×102 dot{M}⊙, the wind pressure overcomes the radiation pressure, and this effect is enhanced by the stellar flares. This greatly contributes to populating the extended AU Mic debris disk and explains the similarity between the β Pictoris and AU Mic brightness profiles. In both cases, the color gradient beyond 120 AU for β Pictoris and 35 AU for AU Mic, is believed to be a direct consequence of the dust dynamics.

The Effects of Surface Roughness on the Apparent Thermal and Optical Properties of the Moon

NASA Astrophysics Data System (ADS)

Rubanenko, L.; Hayne, P. O.; Paige, D. A.

2017-12-01

The thermal inertia and albedo of airless planetary bodies such as the Moon can be inferred by measuring the surface temperatures and solar reflectance. However, roughness below the instrument resolution can affect these measured parameters. Scattering and IR emission from warm slopes onto colder slopes change the surface cooling rate, while shadowing and directional scattering change the reflectance. The importance of these effects grows with increasing solar incidence and emission angles, and during solar eclipses during which the insolation decreases rapidly. The high-quality data gathered by the Lunar Reconnaissance Orbiter (LRO) mission during the last seven years provides us with a unique opportunity to study these effects. Previous works have either adopted a simplified roughness model composed of a single slope, or an illumination model that does not account for subsurface conduction. Our approach incorporates data with simulations conducted using a coupled thermal and illumination model. First, we model the surface temperature distribution below the instrument resolution, considering two realizations: a cratered surface and a Gaussian random surface. Then, we fit the rough surface brightness temperature distribution to that of a flat surface with effective thermal and optical properties to find they differ from the original properties by up to 20% due to the added surface roughness. In the future, this will help to better constrain the intrinsic physical properties of the surface on both the Moon and Mercury and also other airless bodies such as asteroids.

Modeling the non-grey-body thermal emission from the full moon

NASA Technical Reports Server (NTRS)

Vogler, Karl J.; Johnson, Paul E.; Shorthill, Richard W.

1991-01-01

The present series of thermophysical computer models for solid-surfaced planetary bodies whose surface roughness is modeled as paraboloidal craters of specified depth/diameter ratio attempts to characterize the nongrey-body brightness temperature spectra of the moon and of the Galilean satellites. This modeling, in which nondiffuse radiation properties and surface roughness are included for rigorous analysis of scattered and reemitted radiation within a crater, explains to first order the behavior of both limb-scans and disk-integrated IR brightness temperature spectra for the full moon. Only negative surface relief can explain lunar thermal emissions' deviation from smooth Lambert-surface expectations.

Geometrical evidence for dark matter: X-ray constraints on the mass of the elliptical galaxy NGC 720

NASA Astrophysics Data System (ADS)

Buote, David A.; Canizares, Claude R.

1994-05-01

We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential, of the optical light, (2) a technique to measure the shapes of the total gravitating matter and dark matter of an ellipsoidal system which is insensitive to the precise value of the temperature of the gas and to modest temperature gradients, and (3) a new method to determine the ratio of dark mass to stellar mass that is dependent on the functional forms for the visible star, gas and dark matter distributions, but independent of the distance to the galaxy or the gas temperature. We apply these techniques to X-ray data from the ROSAT Position Sensitive Proportional Counter (PSPC) of the optically flattened elliptical galaxy NGC 720; the optical isophotes have ellipticity epsilon approximately 0.40 extending out to approximately 120 sec. The X-ray isophotes are significantly elongated, epsilon = 0.20-0.30 for semimajor axis a approximately 100 sec. The major axes of the optical and X-ray isophotes are misaligned by approximately 30 deg +/- 15 deg. Spectral analysis of the X-ray data reveals no evidence of temperature gradients or anisotropies and demonstrates that a single-temperature plasma (T approximately 0.6 keV) having subsolar heavy element abundances and a two-temperature model having solar abundances describe the spectrum equally well. Considering only the relative geometries of the X-ray and optical surface brightness distributions and an assumed functional form for the potential of the optical light, we conclude that matter distributed like the optical light cannot produce the observed ellipticities of the X-ray isophotes, independent of the gas pressure, the gas temperature, and the value of the stellar mass; this comparison assumes a state of quasi-hydrostatic equilibrium so that the three-dimensional surfaces of the gas emissivity trace the three-dimensional isopotential surfaces -- we discuss the viability of this assumption for NGC 720. Milgrom's Modification of Newtonian Dynamics (MOND) cannot dispel this manifestation of dark matter. Hence, geometrical considerations require, without mention of pressure or temperature, the presence of an extended, massive dark matter halo in NGC 720. Employing essentially the technique of Buote & Canizares (1992; Buote 1992) we use the shape of the X-ray surface brightness to constrain the shape of the total gravitating matter. The total matter is modeled as either an oblate or prolate spheriod of constant shape and orientation having either a Ferrers (rho approximately r-n) or Hernquist density. Assuming the X-ray gas is in hydrostatic equilibrium, we construct a model X-ray gas distribution for various temperature profiles. We determine the ellipticity of the total gravitating matter to be epsilon approximately 0.50-0.70. Using the single-temperature model we estimate a total mass approximately (0.41-1.4) x 1012 h80 solar mass interior to the ellipsoid of semimajor axis 43.6 h80 kpc. Ferrers densities as steep as r-3 do not fit the data, but the r-2 and Hernquist models yield excellent fits. We estimate the mass distributions of the stars and the gas and fit the dark matter directly. For a given gas equation of state and functional forms for the visible stars, gas, and dark matter, these models yield a distance-independent and temperature-independent measurement of the ratio of dark mass to stellar mass MDM/Mstars. We estimate a minimum MDM/Mstars greater than or equal to 4 which corresponds to a total mass slightly greater than that derived from the single-temperature models for distance D = 20h80 Mpc.

Geometrical evidence for dark matter: X-ray constraints on the mass of the elliptical galaxy NGC 720

NASA Technical Reports Server (NTRS)

Buote, David A.; Canizares, Claude R.

1994-01-01

We describe (1) a new test for dark matter and alternate theories of gravitation based on the relative geometries of the X-ray and optical surface brightness distributions and an assumed form for the potential, of the optical light, (2) a technique to measure the shapes of the total gravitating matter and dark matter of an ellipsoidal system which is insensitive to the precise value of the temperature of the gas and to modest temperature gradients, and (3) a new method to determine the ratio of dark mass to stellar mass that is dependent on the functional forms for the visible star, gas and dark matter distributions, but independent of the distance to the galaxy or the gas temperature. We apply these techniques to X-ray data from the ROSAT Position Sensitive Proportional Counter (PSPC) of the optically flattened elliptical galaxy NGC 720; the optical isophotes have ellipticity epsilon approximately 0.40 extending out to approximately 120 sec. The X-ray isophotes are significantly elongated, epsilon = 0.20-0.30 for semimajor axis a approximately 100 sec. The major axes of the optical and X-ray isophotes are misaligned by approximately 30 deg +/- 15 deg. Spectral analysis of the X-ray data reveals no evidence of temperature gradients or anisotropies and demonstrates that a single-temperature plasma (T approximately 0.6 keV) having subsolar heavy element abundances and a two-temperature model having solar abundances describe the spectrum equally well. Considering only the relative geometries of the X-ray and optical surface brightness distributions and an assumed functional form for the potential of the optical light, we conclude that matter distributed like the optical light cannot produce the observed ellipticities of the X-ray isophotes, independent of the gas pressure, the gas temperature, and the value of the stellar mass; this comparison assumes a state of quasi-hydrostatic equilibrium so that the three-dimensional surfaces of the gas emissivity trace the three-dimensional isopotential surfaces -- we discuss the viability of this assumption for NGC 720. Milgrom's Modification of Newtonian Dynamics (MOND) cannot dispel this manifestation of dark matter. Hence, geometrical considerations require, without mention of pressure or temperature, the presence of an extended, massive dark matter halo in NGC 720. Employing essentially the technique of Buote & Canizares (1992; Buote 1992) we use the shape of the X-ray surface brightness to constrain the shape of the total gravitating matter. The total matter is modeled as either an oblate or prolate spheriod of constant shape and orientation having either a Ferrers (rho approximately r(exp -n)) or Hernquist density. Assuming the X-ray gas is in hydrostatic equilibrium, we construct a model X-ray gas distribution for various temperature profiles. We determine the ellipticity of the total gravitating matter to be epsilon approximately 0.50-0.70. Using the single-temperature model we estimate a total mass approximately (0.41-1.4) x 10(exp 12) h(sub 80) solar mass interior to the ellipsoid of semimajor axis 43.6 h(sub 80) kpc. Ferrers densities as steep as r(exp -3) do not fit the data, but the r(exp -2) and Hernquist models yield excellent fits. We estimate the mass distributions of the stars and the gas and fit the dark matter directly. For a given gas equation of state and functional forms for the visible stars, gas, and dark matter, these models yield a distance-independent and temperature-independent measurement of the ratio of dark mass to stellar mass M(sub DM)/M(sub stars). We estimate a minimum M(sub DM)/M(sub stars) greater than or equal to 4 which corresponds to a total mass slightly greater than that derived from the single-temperature models for distance D = 20h(sub 80) Mpc.

Monitoring of deep brain temperature in infants using multi-frequency microwave radiometry and thermal modelling.

PubMed

Han, J W; Van Leeuwen, G M; Mizushina, S; Van de Kamer, J B; Maruyama, K; Sugiura, T; Azzopardi, D V; Edwards, A D

2001-07-01

In this study we present a design for a multi-frequency microwave radiometer aimed at prolonged monitoring of deep brain temperature in newborn infants and suitable for use during hypothermic neural rescue therapy. We identify appropriate hardware to measure brightness temperature and evaluate the accuracy of the measurements. We describe a method to estimate the tissue temperature distribution from measured brightness temperatures which uses the results of numerical simulations of the tissue temperature as well as the propagation of the microwaves in a realistic detailed three-dimensional infant head model. The temperature retrieval method is then used to evaluate how the statistical fluctuations in the measured brightness temperatures limit the confidence interval for the estimated temperature: for an 18 degrees C temperature differential between cooled surface and deep brain we found a standard error in the estimated central brain temperature of 0.75 degrees C. Evaluation of the systematic errors arising from inaccuracies in model parameters showed that realistic deviations in tissue parameters have little impact compared to uncertainty in the thickness of the bolus between the receiving antenna and the infant's head or in the skull thickness. This highlights the need to pay particular attention to these latter parameters in future practical implementation of the technique.

Vela X: A plerion or part of a shell?

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

1998-03-01

An analysis of the radio, optical, and X-ray observations of the supernova remnant (SNR) in Vela has led us to conclude that the radio source Vela X is part of the SNR shell. The high brightness of this radio source is assumed to be a result of the interaction of dome-shaped deformations (bubbles) on the SNR shell, which gives rise to bright radio filaments. The deformations could be produced by Richtmaier-Meshkov's instability, which develops during the impulsive acceleration of a shell of gas (swept up from the interstellar medium by the wind from a presupernova) by a shock wave (generated by a supernova explosion). The brightest radio filament and the X-ray jet extending along it are shown to be located in the region of interaction of two prominent bubbles on the SNR shell. We conclude that the X-ray jet, like Vela X, is part of the shell, and that it has its origin in the Mach reflection of two semispherical shock waves. Our estimate of the plasma temperature behind the front of the Mach wave matches the jet temperature. We also show that the large spread in the estimates of the spectral index for Vela X could be caused by the instrumental effect which arises during observations of extended radio sources with a nonuniform surface-brightness distribution.

Numerical Simulations of Supernova Remnant Evolution in a Cloudy Interstellar Medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slavin, Jonathan D.; Smith, Randall K.; Foster, Adam

The mixed morphology class of supernova remnants has centrally peaked X-ray emission along with a shell-like morphology in radio emission. White and Long proposed that these remnants are evolving in a cloudy medium wherein the clouds are evaporated via thermal conduction once being overrun by the expanding shock. Their analytical model made detailed predictions regarding temperature, density, and emission profiles as well as shock evolution. We present numerical hydrodynamical models in 2D and 3D including thermal conduction, testing the White and Long model and presenting results for the evolution and emission from remnants evolving in a cloudy medium. We findmore » that, while certain general results of the White and Long model hold, such as the way the remnants expand and the flattening of the X-ray surface brightness distribution, in detail there are substantial differences. In particular we find that the X-ray luminosity is dominated by emission from shocked cloud gas early on, leading to a bright peak, which then declines and flattens as evaporation becomes more important. In addition, the effects of thermal conduction on the intercloud gas, which is not included in the White and Long model, are important and lead to further flattening of the X-ray brightness profile as well as lower X-ray emission temperatures.« less

Low-Surface-Brightness Galaxies: Hidden Galaxies Revealed

NASA Astrophysics Data System (ADS)

Bothun, G.; Impey, C.; McGaugh, S.

1997-07-01

In twenty years, low surface brightness (LSB) galaxies have evolved from being an idiosyncratic notion to being one of the major baryonic repositories in the Universe. The story of their discovery and the characterization of their properties is told here. Their recovery from the noise of the night sky background is a strong testament to the severity of surface brightness selection effects. LSB galaxies have a number of remarkable properties which distinguish them from the more familiar Hubble Sequence of spirals. The two most important are 1) they evolve at a significantly slower rate and may well experience star formation outside of the molecular cloud environment, 2) they are embedded in dark matter halos which are of lower density and more extended than the halos around high surface brightness (HSB) disk galaxies. Compared to HSB disks, LSB disks are strongly dark matter dominated at all radii and show a systematic increase in $M/L$ with decreasing central surface brightness. In addition, the recognition that large numbers of LSB galaxies actually exist has changed the form of the galaxy luminosity function and has clearly increased the space density of galaxies at z =0. Recent CCD surveys have uncovered a population of red LSB disks that may be related to the excess of faint blue galaxies detected at moderate redshifts. LSB galaxies offer us a new window into galaxy evolution and formation which is every bit as important as those processes which have produced easy to detect galaxies. Indeed, the apparent youth of some LSB galaxies suggest that galaxy formation is a greatly extended process. While the discovery of LSB galaxies have lead to new insights, it remains unwise to presume that we now have a representative sample which encompasses all galaxy types and forms. (SECTION: Invited Review Paper)

The global distribution, abundance, and stability of SO2 on Io

USGS Publications Warehouse

McEwen, A.S.; Johnson, T.V.; Matson, D.L.; Soderblom, L.A.

1988-01-01

Sulfur dioxide distribution and abundances, bolometric hemispheric albedos, and passive surface temperatures on Io are modeled and mapped globally from Voyager multispectral mosaics, Earth-based spectra, and photometric descriptions. Photometric models indicate global average values for regolith porosity of 75-95% and macroscopic roughness with a mean slope angle of ~30??. Abundances of SO2 suggested by observations at uv-visible wavelengths and at 4.08 ??m are partially reconciled by intimate-mixing models; 30-50% SO2 coverage of the integral disk is indicated. Three major spectral end members, with continuous mixing, are recognized from the Voyager multispectral mosaics; one of these end members is identified as SO2. Intimate-mixing models with the three spectal end members are used to produce abundance maps for the optical surface; ~30% of Io's total optical surface consists of SO2. The SO2 is concentrated in the bright equatorial band and is relatively deficient in the region of Pele-type volcanic reuptions (long 240??-360??) and the polar regions. Temperatures are computed to vary over a 40??K range, at the same illumination angle, according to variations in surface bolometric hemispheric albedo. The brightest (and locally coldest) areas correspond to areas rich in SO2 and are concentrated in an equatorial band (??30?? lat), but many small cold patches occur elsewhere. These cold patches have radiative equilibrium temperatures ???120??K at the subsolar point, resulting in SO2 saturation vapor pressures ???10-8 bar. Midlatitude areas and the region of Pele-type plume eruptions are generally warmer (due to lower albedos). These results for surface temperatures and SO2 abundances and distribution support the regional coldtrapping model for the surface and atmospheric SO2 presented by F.P. Fanale, W.B. Banerdt, L.S. Elson, T.V. Johnson, and R.W. Zurek (1982, In Satellites of Jupiter (D. Morrison, Ed.), pp. 756-781, Univ. of Arizona Press, Tucson), although the region of Pele-type volcanic eruptions may be better characterized by the regolith condtrapping/volcanic-venting model of D.L. Matson and D.B. Nash (1983, J. Geophys. Res. 88, 4771-4783). The bright equatorial band is especially effective at slowing the formation of polar caps of SO2, both by reducing the sublimation rate near the subsolar point and by coldtrapping the SO2 in the equatorial region, so that competing processes of sputtering and volcanic resurfacing may prevent the formation of polar SO2 caps.

Radio emission from supernova remnants in a cloudy interstellar medium

NASA Technical Reports Server (NTRS)

Blandford, R. D.; Cowie, L. L.

1982-01-01

The van der Laan (1962) theory of SNR radio emission is modified in light of the inhomogeneity of the interstellar medium, and in order to allow for particle acceleration in shock fronts. It is proposed that most of the radio emission in 10-20 pc radius SNRs originates in cold interstellar clouds that have been crushed by the high pressure hot gas within the expanding remnant. Under these circumstances, simple reacceleration of ambient interstellar cosmic ray electrons can account for the surface brightness-diameter distribution of observed remnants, with the additional, relativistic particle energy compensating for the decreased filling factor of the radio-emitting regions. Warm interstellar gas, at about 8000 K, may also be compressed within very large SNRs (of radius of 30-100 pc) and account for both the giant radio loops, when these SNRs are seen individually, and the anomalously bright galactic nonthermal radio background, which may be the superposition of a number of such features.

The HD 163296 Circumstellar Disk in Scattered Light: Evidence of Time-Variable Self-Shadowing

NASA Technical Reports Server (NTRS)

Wisniewski, John P.; Clampin, Mark; Grady, Carol A.; Ardila, David R.; Ford, Holland C.; Golimowski, David A.; Illingworth, Garth D.; Krist, John E.

2008-01-01

We present the first multi-color view of the scattered light disk of the Herbig Ae star HD 163296, based on coronagraphic observations from the Hubble Space Telescope Advanced Camera for Surveys (ACS). Radial profile fits of the surface brightness along the disk's semi-major axis indicates that the disk is not continuously flared, and extends to approx.540 AU. The disk's color (V-I)=1.1 at a radial distance of 3.5" is redder than the observed stellar color (V-I)=0.15. This red disk color might be indicative of either an evolution in the grain size distribution (i.e. grain growth) and/or composition, both of which would be consistent with the observed non-flared geometry of the outer disk. We also identify a single ansa morphological structure in our F435W ACS data, which is absent from earlier epoch F606W and F814W ACS data, but corresponds to one of the two ansa observed in archival HST STIS coronagraphic data. Following transformation to similar band-passes, we find that the scattered light disk of HD 163296 is 1 mag arcsec(sup -2) fainter at 3.5" in the STIS data than in the ACS data. Moreover, variations are seen in (i) the visibility of the ansa(e) structures, in (ii) the relative surface brightness of the ansa(e) structures, and in (iii) the (known) intrinsic polarization of the system. These results indicate that the scattered light from the HD 163296 disk is variable. We speculate that the inner disk wall, which Sitko et al. suggests has a variable scale height as diagnosed by near-IR SED variability, induces variable self-shadowing of the outer disk. We further speculate that the observed surface brightness variability of the ansa(e) structures may indicate that the inner disk wall is azimuthally asymmetric. Subject headings: circumstellar matter - stars: individual (HD 163296) - planetary systems: formation - planetary systems: protoplanetary disks

Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System

NASA Technical Reports Server (NTRS)

Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

2012-01-01

The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters, and the single scattering albedo. After this climatological calibration, the modeling system can provide L-band brightness temperatures with a global mean absolute bias of less than 10K against SMOS observations, across multiple incidence angles and for horizontal and vertical polarization. Third, seasonal and regional variations in the residual biases are addressed by estimating the vegetation optical depth through state augmentation during the assimilation of the L-band brightness temperatures. This strategy, tested here with SMOS data, is part of the baseline approach for the Level 4 Surface and Root Zone Soil Moisture data product from the planned Soil Moisture Active Passive (SMAP) satellite mission.

Photometric Studies of GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Cowardin, Heather M.; Barker, Edwin; Abercromby, Kira J.; Foreman, Gary; Horstman, Matt

2009-01-01

The photometric signature of a debris object can be useful in determining what the physical characteristics of a piece of debris are. We report on optical observations in multiple filters of debris at geosynchronous Earth orbit (GEO). Our sample is taken from GEO objects discovered in a survey with the University of Michigan's 0.6-m aperture Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope), and then followed up in real-time with the SMARTS (Small and Medium Aperture Research Telescope System) 0.9-m at CTIO for orbits and photometry. Our goal is to determine 6 parameter orbits and measure colors for all objects fainter than R = 15 th magnitude that are discovered in the MODEST survey. At this magnitude the distribution of observed angular rates changes significantly from that of brighter objects. There are two objectives: 1. Estimate the orbital distribution of objects selected on the basis of two observational criteria: brightness (magnitude) and angular rates. 2. Obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. What is the faint debris likely to be? In this paper we report on the photometric results. For a sample of 50 objects, more than 90 calibrated sequences of R-B-V-I-R magnitudes have been obtained with the CTIO 0.9-m. For objects that do not show large brightness variations, the colors are largely redder than solar in both B-R and R-I. The width of the color distribution may be intrinsic to the nature of the surfaces, but also could be that we are seeing irregularly shaped objects and measuring the colors at different times with just one telescope. For a smaller sample of objects we have observed with synchronized CCD cameras on the two telescopes. The CTIO 0.9-m observes in B, and MODEST in R. The CCD cameras are electronically linked together so that the start time and duration of observations are the same to better than 50 milliseconds. Thus the B-R color is a true measure of the surface of the debris piece facing the telescopes for that observation. Any change in color reflects a real change in the debris surface.

Near Infrared Maps of Elliptical and so Galaxies Detected by IRAS

NASA Astrophysics Data System (ADS)

Cruz-Gonzalez, L.; Recillas-Cruz, E.; Carrasco, L.

1987-05-01

Lw surface brightness maps at 2.2 and 1.25 µm are presented for an IRAS selected sample composed of 3 elliptical and 7 S0 galaxies. In most cases we have found smooth structures which apparently follow the stellar distribution as inferred from the optical images and that the IR emission is more extended. Elongated structures, reminiscent of "jets", are present in a number of galaxies. These 11jets" do not have optical counterparts in the PoSS. This fact suggests a rather steep spectral index between the visible and infrared wavelengths. Fran data at other wavelengths taken from the literature, we have derived spectral energy distributions from .3 to 100 µm. All objects in our sample show a steep α60-l00 µm -l to -2, while in the near IR the energy distributions are characteristic and hence dominated by the presence of a stellar bulge.

Shock-drift particle acceleration in superluminal shocks - A model for hot spots in extragalactic radio sources

NASA Technical Reports Server (NTRS)

Begelman, Mitchell C.; Kirk, John G.

1990-01-01

Shock-drift acceleration at relativistic shock fronts is investigated using a fully relativistic treatment of both the microphysics of the shock-drift acceleration and the macrophysics of the shock front. By explicitly tracing particle trajectories across shocks, it is shown how the adiabatic invariance of a particle's magnetic moment breaks down as the upstream shock speed becomes relativistic, and is recovered at subrelativistic velocities. These calculations enable the mean increase in energy of a particle which encounters the shock with a given pitch angle to be calculated. The results are used to construct the downstream electron distribution function in terms of the incident distribution function and the bulk properties of the shock. The synchrotron emissivity of the transmitted distribution is calculated, and it is demonstrated that amplification factors are easily obtained which are more than adequate to explain the observed constrasts in surface brightness between jets and hot spots.

Skylab experiment SO73: Gegenschein/zodiacal light. [electrophotometry of surface brightness and polarization

NASA Technical Reports Server (NTRS)

Weinberg, J. L.

1976-01-01

A 10 color photoelectric polarimeter was used to measure the surface brightness and polarization associated with zodiacal light, background starlight, and spacecraft corona during each of the Skylab missions. Fixed position and sky scanning observations were obtained during Skylab missions SL-2 and SL-3 at 10 wavelenghts between 4000A and 8200A. Initial results from the fixed-position data are presented on the spacecraft corona and on the polarized brightness of the zodiacal light. Included among the fixed position regions that were observed are the north celestial pole, south ecliptic pole, two regions near the north galactic pole, and 90 deg from the sun in the ecliptic. The polarized brightness of the zodiacal light was found to have the color of the sun at each of these positions. Because previous observations found the total brightness to have the color of the sun from the near ultraviolet out to 2.4 micrometers, the degree of polarization of the zodiacal light is independent of wavelength from 4000A to 8200A.

Stellar Surface Brightness Profiles of Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Herrmann, K. A.

2014-03-01

Radial stellar surface brightness profiles of spiral galaxies can be classified into three types: (I) single exponential, or the light falls off with one exponential out to a break radius and then falls off (II) more steeply (“truncated”), or (III) less steeply (“anti-truncated”). Why there are three different radial profile types is still a mystery, including why light falls off as an exponential at all. Profile breaks are also found in dwarf disks, but some dwarf Type IIs are flat or increasing (FI) out to a break before falling off. I have been re-examining the multi-wavelength stellar disk profiles of 141 dwarf galaxies, primarily from Hunter & Elmegreen (2004, 2006). Each dwarf has data in up to 11 wavelength bands: FUV and NUV from GALEX, UBVJHK and Hα from ground-based observations, and 3.6 and 4.5μm from Spitzer. Here I highlight some results from a semi-automatic fitting of this data set including: (1) statistics of break locations and other properties as a function of wavelength and profile type, (2) color trends and radial mass distribution as a function of profile type, and (3) the relationship of the break radius to the kinematics and density profiles of atomic hydrogen gas in the 40 dwarfs of the LITTLE THINGS subsample.

Structural properties of faint low surface brightness galaxies

NASA Astrophysics Data System (ADS)

Pahwa, Isha; Saha, Kanak

2018-05-01

We study the structural properties of Low Surface Brightness galaxies (LSB) using a sample of 263 galaxies observed by the Green Bank Telescope (Schneider et al. 1992). We perform 2D decompositions of these galaxies in the SDSS g, r and i bands using the GALFIT software. Our decomposition reveals that about 60% of these galaxies are bulgeless i.e., their light distributions are well modelled by pure exponential disks. The rest of the galaxies were fitted with two components: a Sersic bulge and an exponential disk. Most of these galaxies have bulge-to-total (B/T) ratio less than 0.1. However, of these 104 galaxies, 20% have B/T > 0.1 i.e., hosting significant bulge component and they are more prominent amongst the fainter LSBs. According to g - r colour criteria, most of the LSB galaxies in our sample are blue, with only 7 classified as red LSBs. About 15% of the LSB galaxies (including both blue and red) in our sample host stellar bars. The incidence of bars is more prominent in relatively massive blue LSB galaxies with very high gas fraction. These findings may provide important clues to the formation and evolution of LSB galaxies - in particular on the bar/bulge formation in faint LSB disks.

A study of cooling flows in poor clusters of galaxies

NASA Technical Reports Server (NTRS)

Kriss, Gerard A.; Dillingham, Stephen

1995-01-01

We observed three poor clusters with central dominant galaxies (AWM 4, MKW 4, and MKW 3's) using the Position Sensitive Proportional Counter on the ROSAT X-ray satellite. The images reveal smooth, symmetrical X-ray emission filling the cluster with a sharp peak on each central galaxy. The cluster surface brightness profiles can be decomposed using superposed King models for the central galaxy and the intracluster medium. The King model parameters for the cluster portions are consistent with previous observations of these clusters. The newly measured King model parameters for the central galaxies are typical of the X-ray surface brightness distributions of isolated elliptical galaxies. Spatially resolved temperature measurements in annular rings throughout the clusters show a nearly isothermal profile. Temperatures are consistent with previously measured values, but are much better determined. There is no significant drop in temperature noted in the innermost bins where cooling flows are likely to be present, nor is any excess absorption by cold gas required. All cold gas columns are consistent with galactic foreground absorption. We derive mass profiles for the clusters assuming both isothermal temperature profiles and cooling flow models with constant mass flow rates. Our results are consistent with previous Einstein IPC observations by Kriss, Cioffi, & Canizares, but extend the mass profiles out to 1 Mpc in these poor clusters.

Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, F.; Bohler, D.; Ding, Y.

2015-12-07

Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Lightmore » Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.« less

Application of Reflected Global Navigation Satellite System (GNSS-R) Signals in the Estimation of Sea Roughness Effects in Microwave Radiometry

NASA Technical Reports Server (NTRS)

Voo, Justin K.; Garrison, James L.; Yueh, Simon H.; Grant, Michael S.; Fore, Alexander G.; Haase, Jennifer S.; Clauss, Bryan

2010-01-01

In February-March 2009 NASA JPL conducted an airborne field campaign using the Passive Active L-band System (PALS) and the Ku-band Polarimetric Scatterometer (PolSCAT) collecting measurements of brightness temperature and near surface wind speeds. Flights were conducted over a region of expected high-speed winds in the Atlantic Ocean, for the purposes of algorithm development for salinity retrievals. Wind speeds encountered were in the range of 5 to 25 m/s during the two weeks deployment. The NASA-Langley GPS delay-mapping receiver (DMR) was also flown to collect GPS signals reflected from the ocean surface and generate post-correlation power vs. delay measurements. This data was used to estimate ocean surface roughness and a strong correlation with brightness temperature was found. Initial results suggest that reflected GPS signals, using small low-power instruments, will provide an additional source of data for correcting brightness temperature measurements for the purpose of sea surface salinity retrievals.

A Dust-scattering Halo of 4U 1630–47 Observed with Chandra and Swift: New Constraints on the Source Distance

NASA Astrophysics Data System (ADS)

Kalemci, E.; Maccarone, T. J.; Tomsick, J. A.

2018-06-01

We have observed the Galactic black hole transient 4U 1630‑47 during the decay of its 2016 outburst with Chandra and Swift to investigate the properties of the dust-scattering halo created by the source. The scattering halo shows a structure that includes a bright ring between 80″ and 240″ surrounding the source, and a continuous distribution beyond 250″. An analysis of the 12CO J = 1–0 map and spectrum in the line of sight to the source indicates that a molecular cloud with a radial velocity of ‑79 km s‑1 (denoted MC ‑79) is the main scattering body that creates the bright ring. We found additional clouds in the line of sight, calculated their kinematic distances, and resolved the well known “near” and “far” distance ambiguity for most of the clouds. At the favored far-distance estimate of MC ‑79, the modeling of the surface brightness profile results in a distance to 4U 1630‑47 of 11.5 ± 0.3 kpc. If MC ‑79 is at the near distance, then 4U 1630‑47 is at 4.7 ± 0.3 kpc. Future Chandra, Swift, and submillimeter radio observations not only can resolve this ambiguity, but also would provide information regarding properties of dust and the distribution of all molecular clouds along the line of sight. Using the results of this study we also discuss the nature of this source and the reasons for the observation of an anomalously low soft state during the 2010 decay.

Precursor state of oxygen molecules on the Si(001) surface during the initial room-temperature adsorption

NASA Astrophysics Data System (ADS)

Hwang, Eunkyung; Chang, Yun Hee; Kim, Yong-Sung; Koo, Ja-Yong; Kim, Hanchul

2012-10-01

The initial adsorption of oxygen molecules on Si(001) is investigated at room temperature. The scanning tunneling microscopy images reveal a unique bright O2-induced feature. The very initial sticking coefficient of O2 below 0.04 Langmuir is measured to be ˜0.16. Upon thermal annealing at 250-600 °C, the bright O2-induced feature is destroyed, and the Si(001) surface is covered with dark depressions that seem to be oxidized structures with -Si-O-Si- bonds. This suggests that the observed bright O2-induced feature is an intermediate precursor state that may be either a silanone species or a molecular adsorption structure.

Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site

USGS Publications Warehouse

Soderblom, L.A.; Kirk, R.L.; Lunine, J.I.; Anderson, J.A.; Baines, K.H.; Barnes, J.W.; Barrett, J.M.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Cruikshank, D.P.; Elachi, C.; Janssen, M.A.; Jaumann, R.; Karkoschka, E.; Le Mouélic, Stéphane; Lopes, R.M.; Lorenz, R.D.; McCord, T.B.; Nicholson, P.D.; Radebaugh, J.; Rizk, B.; Sotin, Christophe; Stofan, E.R.; Sucharski, T.L.; Tomasko, M.G.; Wall, S.D.

2007-01-01

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 ??m). In such composites bluer materials exhibit higher reflectance at 1.3 ??m and lower at 1.6 and 2.0 ??m. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 ??m/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR). ?? 2007 Elsevier Ltd. All rights reserved.

Archiving, processing, and disseminating ASTER products at the USGS EROS Data Center

USGS Publications Warehouse

Jones, B.; Tolk, B.; ,

2002-01-01

The U.S. Geological Survey EROS Data Center archives, processes, and disseminates Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data products. The ASTER instrument is one of five sensors onboard the Earth Observing System's Terra satellite launched December 18, 1999. ASTER collects broad spectral coverage with high spatial resolution at near infrared, shortwave infrared, and thermal infrared wavelengths with ground resolutions of 15, 30, and 90 meters, respectively. The ASTER data are used in many ways to understand local and regional earth-surface processes. Applications include land-surface climatology, volcanology, hazards monitoring, geology, agronomy, land cover change, and hydrology. The ASTER data are available for purchase from the ASTER Ground Data System in Japan and from the Land Processes Distributed Active Archive Center in the United States, which receives level 1A and level 1B data from Japan on a routine basis. These products are archived and made available to the public within 48 hours of receipt. The level 1A and level 1B data are used to generate higher level products that include routine and on-demand decorrelation stretch, brightness temperature at the sensor, emissivity, surface reflectance, surface kinetic temperature, surface radiance, polar surface and cloud classification, and digital elevation models. This paper describes the processes and procedures used to archive, process, and disseminate standard and on-demand higher level ASTER products at the Land Processes Distributed Active Archive Center.

Real-space mapping of Fano interference in plasmonic metamolecules.

PubMed

Alonso-Gonzalez, Pablo; Schnell, Martin; Sarriugarte, Paulo; Sobhani, Heidar; Wu, Chihhui; Arju, Nihal; Khanikaev, Alexander; Golmar, Federico; Albella, Pablo; Arzubiaga, Libe; Casanova, Felix; Hueso, Luis E; Nordlander, Peter; Shvets, Gennady; Hillenbrand, Rainer

2011-09-14

An unprecedented control of the spectral response of plasmonic nanoantennas has recently been achieved by designing structures that exhibit Fano resonances. This new insight is paving the way for a variety of applications, such as biochemical sensing and surface-enhanced Raman spectroscopy. Here we use scattering-type near-field optical microscopy to map the spatial field distribution of Fano modes in infrared plasmonic systems. We observe in real space the interference of narrow (dark) and broad (bright) plasmonic resonances, yielding intensity and phase toggling between different portions of the plasmonic metamolecules when either their geometric sizes or the illumination wavelength is varied.

A neutral hydrogen survey of the Hydra 1 cluster

NASA Technical Reports Server (NTRS)

Mcmahon, Pauline; Vangorkom, Jacqueline; Richter, Otto; Ferguson, Henry

1993-01-01

We are undertaking a project to image the entire volume of the Hydra 1 cluster of galaxies in neutral hydrogen using the VLA. This involves making a series of pointings spaced 30 min. (the half power beam width) apart, each observed at three velocity settings in order to span the whole velocity range of the cluster. The purpose of this survey is to determine the true distribution, both in space and velocity, of gas-rich systems and hence, to deduce what effects a dense environment may have on the evolution of these systems. Most surveys of clusters to date have been performed on optically selected samples. However, optically selected samples may provide misleading views of the distribution of gas-rich systems, since many low surface brightness galaxies have an abundance of neutral gas (Bothun et al. 1987, Giovanelli & Haynes 1989). The Hydra project is providing the first unbiased view of the HI distribution in a cluster of galaxies. Our 5 sigma sensitivity is 4.1 x 10(exp 7) solar M/beam, (assuming H(sub 0) = 75 km s(exp -1) Mpc(exp -1)) and our velocity resolution is 42 km s(exp -1). We have a spatial resolution of 45 sec., which means that only the largest galaxies are spatially resolved enough to determine HI disk size. Our coverage is about 50 percent of the central region plus eight other fields centered on bright spirals within about 2 deg. of the center.

High-resolution maps of Jupiter at five microns.

NASA Technical Reports Server (NTRS)

Keay, C. S. L.; Low, F. J.; Rieke, G. H.; Minton, R. B.

1973-01-01

The distribution of 5-micron radiation, emitted from a large number of discrete sources from Jupiter, was observed during the 1972 apparition. These sources are less bright than those observed by Westphal (1969). At least 50 discrete sources having brightness temperatures exceeding 227 K were revealed which were mainly located within three narrow-latitude bands. Strong correlation exists between the 5-micron brightness temperatures of Jovian features and their colors as recorded photographically.

Lunar brightness temperature from Microwave Radiometers data of Chang'E-1 and Chang'E-2

NASA Astrophysics Data System (ADS)

Feng, J.-Q.; Su, Y.; Zheng, L.; Liu, J.-J.

2011-10-01

Both of the Chinese lunar orbiter, Chang'E-1 and Chang'E-2 carried Microwave Radiometers (MRM) to obtain the brightness temperature of the Moon. Based on the different characteristics of these two MRMs, modified algorithms of brightness temperature and specific ground calibration parameters were proposed, and the corresponding lunar global brightness temperature maps were made here. In order to analyze the data distributions of these maps, normalization method was applied on the data series. The second channel data with large deviations were rectified, and the reasons of deviations were analyzed in the end.

The very soft X-ray emission of X-ray-faint early-type galaxies

NASA Technical Reports Server (NTRS)

Pellegrini, S.; Fabbiano, G.

1994-01-01

A recent reanaylsis of Einstein data, and new ROSAT observations, have revealed the presence of at least two components in the X-ray spectra of X-ray faint early-type galaxies: a relatively hard component (kT greater than 1.5 keV), and a very soft component (kT approximately 0.2-0.3 keV). In this paper we address the problem of the nature of the very soft component and whether it can be due to a hot interstellar medium (ISM), or is most likely originated by the collective emission of very soft stellar sources. To this purpose, hydrodynamical evolutionary sequences for the secular behavior of gas flows in ellipticals have been performed, varying the Type Ia supernovae rate of explosion, and the dark matter amount and distribution. The results are compared with the observational X-ray data: the average Einstein spectrum for six X-ray faint early-type galaxies (among which are NGC 4365 and NGC 4697), and the spectrum obtained by the ROSAT pointed observation of NGC 4365. The very soft component could be entirely explained with a hot ISM only in galaxies such as NGC 4697, i.e., when the depth of the potential well-on which the average ISM temperature strongly depends-is quite shallow; in NGC 4365 a diffuse hot ISM would have a temperature larger than that of the very soft component, because of the deeper potential well. So, in NGC 4365 the softest contribution to the X-ray emission comes certainly from stellar sources. As stellar soft X-ray emitters, we consider late-type stellar coronae, supersoft sources such as those discovered by ROSAT in the Magellanic Clouds and M31, and RS CVn systems. All these candidates can be substantial contributors to the very soft emission, though none of them, taken separately, plausibly accounts entirely for its properties. We finally present a model for the X-ray emission of NGC 4365, to reproduce in detail the results of the ROSAT pointed observation, including the Position Sensitive Proportional Counter (PSPC) spectrum and radial surface brightness distribution. The present data may suggest that the X-ray surface brightness is more extended than the optical profile. In this case, a straightforward explanation in terms of stellar sources could not be satisfactory. The available data can be better explained with three different contributions: a very soft component of stellar origin, a hard component from X-ray binaries, and an approximately 0.6 keV hot ISM. The latter can explain the extended X-ray surface brightness profile, if the galaxy has a dark-to-luminous mass ratio of 9, with the dark matter very broadly distributed, and a SN Ia explosive rate of approximately 0.6 the Tammann rate.

SPARC: MASS MODELS FOR 175 DISK GALAXIES WITH SPITZER PHOTOMETRY AND ACCURATE ROTATION CURVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lelli, Federico; McGaugh, Stacy S.; Schombert, James M., E-mail: federico.lelli@case.edu

2016-12-01

We introduce SPARC ( Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6  μ m and high-quality rotation curves from previous H i/H α studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i   mass–radius relation is extremely tight. We build detailedmore » mass models and quantify the ratio of baryonic to observed velocity ( V {sub bar}/ V {sub obs}) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ{sub ⋆}) at [3.6]. Assuming ϒ{sub ⋆} ≃ 0.5 M {sub ⊙}/ L {sub ⊙} (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity; (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii)  V {sub bar}/ V {sub obs} varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ{sub ⋆} ≃ 0.2 M {sub ⊙}/ L {sub ⊙} as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ{sub ⋆} ≃ 0.7 M {sub ⊙}/ L {sub ⊙} at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.« less

Andromeda (M31) optical and infrared disk survey. I. Insights in wide-field near-IR surface photometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sick, Jonathan; Courteau, Stéphane; Cuillandre, Jean-Charles

We present wide-field near-infrared J and K{sub s} images of the Andromeda Galaxy (M31) taken with WIRCam at the Canada-France-Hawaii Telescope as part of the Andromeda Optical and Infrared Disk Survey. This data set allows simultaneous observations of resolved stars and near-infrared (NIR) surface brightness across M31's entire bulge and disk (within R = 22 kpc), permitting a direct test of the stellar composition of near-infrared light in a nearby galaxy. Here we develop NIR observation and reduction methods to recover a uniform surface brightness map across the 3° × 1° disk of M31 with 27 WIRCam fields. Two sky-targetmore » nodding strategies are tested, and we find that strictly minimizing sky sampling latency cannot improve background subtraction accuracy to better than 2% of the background level due to spatio-temporal variations in the NIR skyglow. We fully describe our WIRCam reduction pipeline and advocate using flats built from night-sky images over a single night, rather than dome flats that do not capture the WIRCam illumination field. Contamination from scattered light and thermal background in sky flats has a negligible effect on the surface brightness shape compared to the stochastic differences in background shape between sky and galaxy disk fields, which are ∼0.3% of the background level. The most dramatic calibration step is the introduction of scalar sky offsets to each image that optimizes surface brightness continuity. Sky offsets reduce the mean surface brightness difference between observation blocks from 1% to <0.1% of the background level, though the absolute background level remains statistically uncertain to 0.15% of the background level. We present our WIRCam reduction pipeline and performance analysis to give specific recommendations for the improvement of NIR wide-field imaging methods.« less

The Fornax Deep Survey with VST. III. Low surface brightness dwarfs and ultra diffuse galaxies in the center of the Fornax cluster

NASA Astrophysics Data System (ADS)

Venhola, Aku; Peletier, Reynier; Laurikainen, Eija; Salo, Heikki; Lisker, Thorsten; Iodice, Enrichetta; Capaccioli, Massimo; Kleijn, Gijs Verdoes; Valentijn, Edwin; Mieske, Steffen; Hilker, Michael; Wittmann, Carolin; van de Ven, Glenn; Grado, Aniello; Spavone, Marilena; Cantiello, Michele; Napolitano, Nicola; Paolillo, Maurizio; Falcón-Barroso, Jesús

2017-12-01

Context. Studies of low surface brightness (LSB) galaxies in nearby clusters have revealed a sub-population of extremely diffuse galaxies with central surface brightness of μ0,g' > 24 mag arcsec-2, total luminosity Mg' fainter than -16 mag and effective radius between 1.5 kpc 23 mag arcsec-2. We classified the objects based on their appearance into galaxies and tidal structures, and perform 2D Sérsic model fitting with GALFIT to measure the properties of those classified as galaxies. We analyzed their radial distribution and orientations with respect of the cluster center, and with respect to the other galaxies in our sample. We also studied their colors and compare the LSB galaxies in Fornax with those in other environments. Results: Our final sample complete in the parameter space of the previously known UDGs, consists of 205 galaxies of which 196 are LSB dwarfs (with Re < 1.5 kpc) and nine are UDGs (Re > 1.5 kpc). We show that the UDGs have (1) g'-r' colors similar to those of LSB dwarfs of the same luminosity; (2) the largest UDGs (Re > 3 kpc) in our sample appear different from the other LSB galaxies, in that they are significantly more elongated and extended; whereas (3) the smaller UDGs differ from the LSB dwarfs only by having slightly larger effective radii; (4) we do not find clear differences between the structural parameters of the UDGs in our sample and those of UDGs in other galaxy environments; (5) we find that the dwarf LSB galaxies in our sample are less concentrated in the cluster center than the galaxies with higher surface brightness, and that their number density drops within 180 kpc from the cluster center. We also compare the LSB dwarfs in Fornax with the LSB dwarfs in the Centaurus group, where data of similar quality to ours is available. (6) We find the smallest LSB dwarfs to have similar colors, sizes and Sérsic profiles regardless of their environment. However, in the Centaurus group the colors become bluer with increasing galaxy magnitudes, an effect which is probably due to smaller mass and hence weaker environmental influence of the Centaurus group. Conclusions: Our findings are consistent with the small UDGs forming the tail of a continuous distribution of less extended LSB galaxies. However, the elongated and distorted shapes of the large UDGs could imply that they are tidally disturbed galaxies. Due to limitations of the automatic detection methods and uncertainty in the classification the objects, it is yet unclear what is the total contribution of the tidally disrupted galaxies in the UDG population.

Visual aid titled 'The Magellan Mission to Venus'

NASA Technical Reports Server (NTRS)

1988-01-01

Visual aid titled 'The Magellan Mission to Venus' describes data that will be collected and science objectives. Images and brightness temperatures will be obtained for 70-90% of the surface, with a radar resolution of 360 meters or better. The global gravity field model will be refined by combining Magellan and Pioneer-Venus doppler data. Altimetry data will be used to measure the topography of 70-90% of the surface with a vertical accuracy of 120-360 meters. Science objectives include: to improve the knowledge of the geological history of Venus by analysis of the surface morphology and electrical properties and the processes that control them; and to improve the knowledge of the geophysics of Venus, principally its density distribution and dynamics. Magellan, named for the 16th century Portuguese explorer, will be deployed from the payload bay (PLB) of Atlantis, Orbiter Vehicle (OV) 104, during mission STS-30.

ARC-1979-A79-7020

NASA Image and Video Library

1979-02-28

Range : 7 million kilometers (5 million miles) Callisto is Jupiter's outermost Galilean satellites and darkest of the four(but almost twice as bright as Earth's Moon). Mottled appearance from bright and dark patches. Bright spots seem like rayed or bright halved craters seen on our Moon. This face is always turned toward Jupiter. Photo taken through violet filter. Ganymede is slightly larger than Mercury but much less dense (twice the density of water). Its surface brightness is 4 times of Earth's Moon. Mare regions (dark features) are like the Moon's but have twice the brightness, and believed to be unlikely of rock or lava as the Moon's are. It's north pole seems covered with brighter material and may be water frost. Scattered brighter spots may be related to impact craters or source of fresh ice.

Hubble Sees Galaxy Hiding in the Night Sky

NASA Image and Video Library

2017-12-08

This striking NASA/ESA Hubble Space Telescope image captures the galaxy UGC 477, located just over 110 million light-years away in the constellation of Pisces (The Fish). UGC 477 is a low surface brightness (LSB) galaxy. First proposed in 1976 by Mike Disney, the existence of LSB galaxies was confirmed only in 1986 with the discovery of Malin 1. LSB galaxies like UGC 477 are more diffusely distributed than galaxies such as Andromeda and the Milky Way. With surface brightnesses up to 250 times fainter than the night sky, these galaxies can be incredibly difficult to detect. Most of the matter present in LSB galaxies is in the form of hydrogen gas, rather than stars. Unlike the bulges of normal spiral galaxies, the centers of LSB galaxies do not contain large numbers of stars. Astronomers suspect that this is because LSB galaxies are mainly found in regions devoid of other galaxies, and have therefore experienced fewer galactic interactions and mergers capable of triggering high rates of star formation. LSB galaxies such as UGC 477 instead appear to be dominated by dark matter, making them excellent objects to study to further our understanding of this elusive substance. However, due to an underrepresentation in galactic surveys — caused by their characteristic low brightness — their importance has only been realized relatively recently. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Pox 186: An ultracompact galaxy with dominant ionized gas emission

NASA Astrophysics Data System (ADS)

Guseva, N. G.; Papaderos, P.; Izotov, Y. I.; Noeske, K. G.; Fricke, K. J.

2004-07-01

We present a ground-based optical spectroscopic and HST U, V, I photometric study of the blue compact dwarf (BCD) galaxy Pox 186. It is found that the emission of the low-surface brightness (LSB) component in Pox 186 at radii ⪉3 arcsec (⪉270 pc in linear scale) is mainly gaseous in origin. We detect Hα emission out to radii as large as 6 arcsec. At radii ⪆3 arcsec the light of the LSB component is contaminated by the emission of background galaxies complicating the study of the outermost regions. The surface brightness distribution in the LSB component can be approximated by an exponential law with a scale length α ⪉ 120 pc. This places Pox 186 among the most compact dwarf galaxies known. The derived α is likely to be an upper limit to the scale length of the LSB component because of the strong contribution of the gaseous emission. The oxygen abundance in the bright H II region derived from the 4.5 m Multiple Mirror Telescope (MMT) and 3.6 m ESO telescope spectra are 12 + log (O/H) = 7.76 ± 0.02 and 7.74 ± 0.01 (˜Z⊙/15), respectively, in accordance with previous determinations. The helium mass fractions found in this region are Y = 0.248 ± 0.009 (MMT) and Y = 0.248 ± 0.004 (3.6 m) suggesting a high primordial helium abundance. The MMT Observatory is a joint facility of the Smithsonian Institution and the University of Arizona. Based on observations collected at the European Southern Observatory, Chile, ESO program 71.B-0032(A). 12+\\log(O/H)⊙ = 8.92 (Anders & Grevesse \\cite{Anders89}).

THE PHOTOMETRIC PROPERTIES OF A VAST STELLAR SUBSTRUCTURE IN THE OUTSKIRTS OF M33

DOE Office of Scientific and Technical Information (OSTI.GOV)

McConnachie, Alan W.; Ferguson, Annette M. N.; Irwin, Michael J.

2010-11-10

We have surveyed approximately 40 deg{sup 2} surrounding M33 with Canada-France-Hawaii Telescope MegaCam/MegaPrime in the g and i filters out to a maximum projected radius from this galaxy of 50 kpc, as part of the Pan-Andromeda Archaeological Survey (PAndAS). Our observations are deep enough to resolve the top {approx}4 mag of the red giant branch population in this galaxy. We have previously shown that the disk of M33 is surrounded by a large, irregular, low surface brightness substructure. Here, we quantify the stellar populations and structure of this feature using the PAndAS data. We show that the stellar populations ofmore » this feature are consistent with an old population with ([Fe/H]) {approx} -1.6 dex and an interquartile range in metallicity of {approx}0.5 dex. We construct a surface brightness map of M33 that traces this feature to {mu}{sub V} {approx_equal} 33 mag arcsec{sup -2}. At these low surface brightness levels, the structure extends to projected radii of {approx}40 kpc from the center of M33 in both the northwest and southeast quadrants of the galaxy. Overall, the structure has an 'S-shaped' appearance that broadly aligns with the orientation of the H I disk warp. We calculate a lower limit to the integrated luminosity of the structure of -12.7 {+-} 0.5 mag, comparable to a bright dwarf galaxy such as Fornax or Andromeda II and slightly less than 1% of the total luminosity of M33. Further, we show that there is tentative evidence for a distortion in the distribution of young stars near the edge of the H I disk that occurs at similar azimuth to the warp in H I. The data also hint at a low-level, extended stellar component at larger radius that may be an M33 halo component. We revisit studies of M33 and its stellar populations in light of these new results and discuss possible formation scenarios for the vast stellar structure. Our favored model is that of the tidal disruption of M33 in its orbit around M31.« less

Tracing the stellar component of low surface brightness Milky Way dwarf galaxies to their outskirts. I. Sextans

NASA Astrophysics Data System (ADS)

Cicuéndez, L.; Battaglia, G.; Irwin, M.; Bermejo-Climent, J. R.; McMonigal, B.; Bate, N. F.; Lewis, G. F.; Conn, A. R.; de Boer, T. J. L.; Gallart, C.; Guglielmo, M.; Ibata, R.; McConnachie, A.; Tolstoy, E.; Fernando, N.

2018-01-01

Aims: We present results from deep and very spatially extended CTIO/DECam g and r photometry (reaching out to 2 mag below the oldest main-sequence turn-off and covering 20 deg2) around the Sextans dwarf spheroidal galaxy. We aim to use this dataset to study the structural properties of Sextans overall stellar population and its member stars in different evolutionary phases, as well as to search for possible signs of tidal disturbance from the Milky Way, which would indicate departure from dynamical equilibrium. Methods: We performed the most accurate and quantitative structural analysis to-date of Sextans' stellar components by applying Bayesian Monte Carlo Markov chain methods to the individual stars' positions. Surface density maps are built by statistically decontaminating the sample through a matched filter analysis of the colour-magnitude diagram, and then analysed for departures from axisymmetry. Results: Sextans is found to be significantly less spatially extended and more centrally concentrated than early studies suggested. No statistically significant distortions or signs of tidal disturbances were found down to a surface brightness limit of 31.8 mag/arcsec2 in V-band. We identify an overdensity in the central regions that may correspond to previously reported kinematic substructure(s). In agreement with previous findings, old and metal-poor stars such as Blue Horizontal Branch stars cover a much larger area than stars in other evolutionary phases, and bright Blue Stragglers (BSs) are less spatially extended than faint ones. However, the different spatial distribution of bright and faint BSs appears consistent with the general age and metallicity gradients found in Sextans' stellar component. This is compatible with Sextans BSs having formed by evolution of binaries and not necessarily due to the presence of a central disrupted globular cluster, as suggested in the literature. We provide structural parameters for the various populations analysed and make publicly available the photometric catalogue of point-sources as well as a catalogue of literature spectroscopic measurements with updated membership probabilities. Full Tables 2 and 6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A53

Hot Spots on Io: Initial Results From Galileo's Near Infrared Mapping Spectrometer

NASA Technical Reports Server (NTRS)

Lopes-Gautier, Rosaly; Davies, A. G.; Carlson, R.; Smythe, W.; Kamp, L.; Soderblom, L.; Leader, F. E.; Mehlman, R.

1997-01-01

The Near-Infrared Mapping Spectrometer on Galileo has monitored the volcanic activity on Io since June 28, 1996. This paper presents preliminary analysis of NIMS thermal data for the first four orbits of the Galileo mission. NIMS has detected 18 new hot spots and 12 others which were previously known to be active. The distribution of the hot spots on Io's surface may not be random, as hot spots surround the two bright, SO2-rich regions of Bosphorus Regio and Colchis Regio. Most hot spots scan to be persistently active from orbit to orbit and 10 of those detected were active in 1979 during the Voyager encounters. We report the distribution of hot spot temperatures and find that they are consistent with silicate volcanism.

Study of the model of calibrating differences of brightness temperature from geostationary satellite generated by time zone differences

NASA Astrophysics Data System (ADS)

Li, Weidong; Shan, Xinjian; Qu, Chunyan

2010-11-01

In comparison with polar-orbiting satellites, geostationary satellites have a higher time resolution and wider field of visions, which can cover eleven time zones (an image covers about one third of the Earth's surface). For a geostationary satellite panorama graph at a point of time, the brightness temperature of different zones is unable to represent the thermal radiation information of the surface at the same point of time because of the effect of different sun solar radiation. So it is necessary to calibrate brightness temperature of different zones with respect to the same point of time. A model of calibrating the differences of the brightness temperature of geostationary satellite generated by time zone differences is suggested in this study. A total of 16 curves of four positions in four different stages are given through sample statistics of brightness temperature of every 5 days synthetic data which are from four different time zones (time zones 4, 6, 8, and 9). The above four stages span January -March (winter), April-June (spring), July-September (summer), and October-December (autumn). Three kinds of correct situations and correct formulas based on curves changes are able to better eliminate brightness temperature rising or dropping caused by time zone differences.

Pyroclastic flow deposits on Venus as indicators of renewed magmatic activity

NASA Astrophysics Data System (ADS)

Campbell, Bruce A.; Morgan, Gareth A.; Whitten, Jennifer L.; Carter, Lynn M.; Glaze, Lori S.; Campbell, Donald B.

2017-07-01

Radar bright deposits on Venus that have diffuse margins suggest eruptions that distribute debris over large areas due to ground-hugging flows from plume collapse. We examine deposits in eastern Eistla, western Eistla, Phoebe, and Dione Regiones using Magellan data and Earth-based radar maps. The radar bright units have no marginal lobes or other features consistent with viscous flow. Their morphology, radar echo strength, polarization properties, and microwave emissivity are consistent with mantling deposits composed of few centimeters or larger clasts. This debris traveled downhill up to 100 km on modest slopes and blanketed lava flows and tectonic features to depths of tens of centimeters to a few meters over areas up to 40 × 103 km2. There is evidence for ongoing removal and exhumation of previously buried terrain. A newly identified occurrence is associated with a ridge belt south of Ushas Mons. We also note radar bright streaks of coarse material west of Rona Chasma that reflect the last traces of a deposit mobilized by winds from the formation of Mirabeau crater. If the radar bright units originate by the collapse of eruption columns, with coarse fragmental material entrained and fluidized by hot gases, then their extent suggests large erupted volatile (CO2 or H2O) amounts. We propose that these deposits reflect the early stage of renewed magmatic activity, with volatile-rich, disrupted magma escaping through vents in fractured regions of the upper crust. Rapidly eroding under Venus surface conditions or buried by subsequent eruptions, these markers of recently renewed activity have disappeared from older regions.

Measurements of the energy distribution of a high brightness rubidium ion beam.

PubMed

Ten Haaf, G; Wouters, S H W; Nijhof, D F J; Mutsaers, P H A; Vredenbregt, E J D

2018-07-01

The energy distribution of a high brightness rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is (0.205 ± 0.006) eV, which is measured at a beam current of 9 pA. The energy spread originates from the variation in the ionization position of the ions which are created inside an extraction electric field. This extraction field is essential to limit disorder-induced heating which can decrease the ion beam brightness. The ionization position distribution is limited by a tightly focused excitation laser beam. Energy distributions are measured for various ionization and excitation laser intensities and compared with calculations based on numerical solutions of the optical Bloch equations including ionization. A good agreement is found between measurements and calculations. Copyright © 2018 Elsevier B.V. All rights reserved.

Distribution of small channels on the Martian surface

NASA Technical Reports Server (NTRS)

Pieri, D.

1976-01-01

The distribution of small channels on Mars has been mapped from Mariner 9 images at the 1:5,000,000 scale. The small channels referred to here are small valleys ranging in width from the resolution limit of the Mariner 9 wide-angle images (about 1 km) to about 10 km. The greatest density of small channels occurs in dark cratered terrain. This dark zone forms a broad subequatorial band around the planet. The observed distribution may be the result of decreased small-channel visibility in bright areas due to obscuration by a high albedo dust or sediment mantle. Crater densities within two small-channel segments show crater size-frequency distributions consistent with those of the oldest of the heavily cratered plains units. Such crater densities coupled with the almost exclusive occurrence of small channels in old cratered terrain and the generally degraded appearance of small channels in the high-resolution images (about 100 m) imply a major episode of small-channel formation early in Martian geologic history.

Distribution of small channels on the Martian surface

USGS Publications Warehouse

Pieri, D.

1976-01-01

The distribution of small channels on Mars has been mapped from Mariner 9 images, at the 1:5 000 000 scale, by the author. The small channels referred to here are small valleys ranging in width from the resolution limit of the Mariner 9 wide-angle images (???1 km) to about 10 km. The greatest density of small band occurs in dark cratered terrain. This dark zone forms a broad subequatorial band around the planet. The observed distribution may be the result of decreased small-channel visibility in bright areas due to obscuration by a high albedo dust or sediment mantle. Crater densities within two small-channel segments show crater size-frequency distributions consistent with those of the oldest of the heavily cratered plains units. Such crater densities coupled with the almost exclusive occurrence of small channels in old cratered terrain and the generally degraded appearance of small channels in the high-resolution images (???100 m) imply a major episode of small-channel formation early in Martian geologic history. ?? 1976.

Is the zodiacal light intensity steady. [cloud surface brightness and polarization from OSO-5 data

NASA Technical Reports Server (NTRS)

Burnett, G. B.; Sparrow, J. G.; Ney, E. P.

1974-01-01

It is pointed out that conclusions reported by Sparrow and Ney (1972, 1973) could be confirmed in an investigation involving the refinement of OSO-5 data on zodiacal light. It had been found by Sparrow and Ney that the absolute value of both the surface brightness and polarization of the zodiacal cloud varied by less than 10% over the 4-yr period from January 1969 to January 1973.

Measurements of the dielectric properties of sea water at 1.43 GHz

NASA Technical Reports Server (NTRS)

Ho, W. W.; Love, A. W.; Vanmelle, M. J.

1974-01-01

Salinity and temperature of water surfaces of estuaries and bay regions are determined to accuracies of 1 ppt salinity and 0.3 kelvin surface temperature. L-band and S-band radiometers are used in combination as brightness temperature detectors. The determination of the brightness temperature versus salinity, with the water surface temperature as a parameter for 1.4 GHz, is performed with a capillary tube inserted into a resonance cavity. Detailed analysis of the results indicates that the measured values are accurate to better than 0.2 percent in the electric property epsilon' and 0.4 percent in epsilon''. The calculated brightness temperature as a function of temperature and salinity is better than 0.2 kelvin. Thus it is possible to reduce the measured data obtained with the two-frequency radiometer system with 1 ppt accuracy to values in the salinity range 5 to 40 ppt.

Low-temperature transonic cooling flows in galaxy clusters

NASA Technical Reports Server (NTRS)

Sulkanen, Martin E.; Burns, Jack O.; Norman, Michael L.

1989-01-01

Calculations are presented which demonstrate that cooling flow models with large sonic radii may be consistent with observed cluster gas properties. It is found that plausible cluster parameters and cooling flow mass accretion rates can produce sonic radii of 10-20 kpc for sonic point temperatures of 1-3 x 10 to the 6th K. The numerical calculations match these cooling flows to hydrostatic atmosphere solutions for the cluster gas beyond the cooling flow region. The cooling flows produce no appreciable 'holes' in the surface brightness toward the cluster center, and the model can be made to match the observed X-ray surface brightness of three clusters in which cooling flows had been believed to be absent. It is suggested that clusters with low velocity dispersion may be the natural location for such 'cool' cooling flows, and fits of these models to the X-ray surface brightness profiles for three clusters are presented.

The Fundamental Plane and the Surface Brightness Test for the Expansion of the Universe

NASA Astrophysics Data System (ADS)

Kjaergaard, Per; Jorgensen, Inger; Moles, Mariano

1993-12-01

We have determined the Petrosian radius, rη , and the enclosed mean surface brightness within the Petrosian radius, <μ>η, for 33 elliptical and S0 galaxies in the Coma cluster from new accurate CCD surface photometry. For the Petrosian parameter η = 1.39, rη and <μ>η are compared with the effective radius, re, and the effective mean surface brightness, <μ>e derived from fitting a de Vaucouleurs law. The fundamental plane (FP) expressed using rη and <μ>η is the same as the FP found by Jørgensen, Franx, & Kjaergaard (1993) using re and <μ>e. The FP can be used to predict the mean surface brightness within the effective radius or the corresponding Petrosian radius (η = 1.39) with an uncertainty of ±0.14 mag for Coma cluster ellipticals. Thus the FP, applied to clusters, appears to be a suitable tool for performing the surface brightness test (SBT) for the expansion of the universe. We suggest that instead of correcting individual galaxies to some standard conditions, e.g., the same metric radius, the fundamental plane itself should be considered the standard. It is argued that the metric size enclosing around 75% of the total light represents a reasonable compromise between resolution and faint level detection when performing the SBT. This radius could be derived as the Petrosian radius corresponding to η = 2.0 or from a global fit to that part of the observed profile which encompasses 75% of the total light. In case both small and large galaxies are well described by a de Vaucouleurs law the global fit can be performed on a smaller central part of the brightness profile. The use of the FP involves the time consuming determinations of velocity dispersions. We find that <μ>η (η = 1.39) can be predicted from the log rη alone with an accuracy of 0.3 mag for the Coma cluster ellipticals. Our discussion of the various error contributions to the predicted mean surface brightness for faint cluster ellipticals at redshifts z < 0.5 shows that the final error is probably dominated by extra scatter due to, e.g., environmental and evolutionary effects. Thus it might be possible that the use of velocity dispersions are not necessary. To get significant results for the SBT, clusters out to a redshift of approximately z = 0.3 have to be observed. For the most distant galaxies light levels down to about 25-26 mag arcsec-2 in the red and sizes as small as approximately 2" have to be accurately measured. We outline an observational program which will allow the control of the different sources of scatter, including cosmic evolution, producing conclusive results about the expansion of the universe.

Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

NASA Technical Reports Server (NTRS)

Yueh, Simon H.

2004-01-01

Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

ON THE BRIGHTNESS AND WAITING-TIME DISTRIBUTIONS OF A TYPE III RADIO STORM OBSERVED BY STEREO/WAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eastwood, J. P.; Hudson, H. S.; Krucker, S.

2010-01-10

Type III solar radio storms, observed at frequencies below {approx}16 MHz by space-borne radio experiments, correspond to the quasi-continuous, bursty emission of electron beams onto open field lines above active regions. The mechanisms by which a storm can persist in some cases for more than a solar rotation whilst exhibiting considerable radio activity are poorly understood. To address this issue, the statistical properties of a type III storm observed by the STEREO/WAVES radio experiment are presented, examining both the brightness distribution and (for the first time) the waiting-time distribution (WTD). Single power-law behavior is observed in the number distribution asmore » a function of brightness; the power-law index is {approx}2.1 and is largely independent of frequency. The WTD is found to be consistent with a piecewise-constant Poisson process. This indicates that during the storm individual type III bursts occur independently and suggests that the storm dynamics are consistent with avalanche-type behavior in the underlying active region.« less

Fatigue of Austempered Ductile Iron with Two Strength Grades in Very High Cycle Regime

NASA Astrophysics Data System (ADS)

Zhang, Jiwang; Li, Wei; Song, Qingpeng; Zhang, Ning; Lu, Liantao

2016-03-01

In this study, Austempered ductile irons (ADIs) with two different strength grades were produced and the fatigue properties were measured at 109 cycles. The results show that the S-N curves give a typical step-wise shape and there is no fatigue limit in the very high cycle fatigue regime. The two grades ADI have the similar fracture behaviors and fatigue failure can initiate from defects at specimen surface and subsurface zone. On the fracture surfaces of some specimens, the `granular-bright-facet' area with rich carbon distribution is observed in the vicinity of the defect. The microstructure affects the crack behaviors at the early propagation stage. The ADI with upper and lower bainite shows higher fatigue strength compared with the ADI with coarse upper bainite.

The Progenitor and Remnant of the Helium Nova V445 Puppis

NASA Astrophysics Data System (ADS)

Goranskij, V.; Shugarov, S.; Zharova, A.; Kroll, P.; Barsukova, E. A.

2010-10-01

V445 Pup was a peculiar nova with no hydrogen spectral lines during the outburst. The spectrum contained strong emission lines of carbon, oxygen, calcium, sodium, and iron. We have performed digital processing of photographic images of the V445 Pup progenitor using astronomical plate archives. The brightness of the progenitor in the B band was 14.3m. It was a periodic variable star, its most probable period being 0.650654+/-0.000011 days. The light curve shape suggests that the progenitor was a common-envelope binary with a spot on the surface and variable surface brightness. The spectral energy distribution of the progenitor between 0.44 and 2.2 microns was similar to that of an A0V type star. After the explosion in 2001, the dust was formed in the ejecta, and the star became a strong infrared source. This resulted in the star's fading below 20m in the V band. Our CCD BVR observations acquired between 2003 and 2009 suggest that the dust absorption minimum finished in 2004, and the remnant reappeared at the level of 18.5m V. The dust dispersed but a star-like object was absent in frames taken in the K band with the VLT adaptive optics. Only expanding ejecta of the explosion were seen in these frames till March 2007. No reddened A0V type star reappeared in the spectral energy distribution. The explosion of V445 Pup in 2000 was a helium flash on the surface of a CO-type white dwarf. Taking into account the results of modern dynamic calculations, we discuss the possibility of a white-dwarf core detonation triggered by the helium flash and the observational evidence for it. Additionally, the common envelope of the system was lost in the explosion. Destruction in the system and mass loss from its components exclude the future SN Ia scenario for V445 Pup.

A wide-field survey of satellite galaxies around the spiral galaxy M106

NASA Astrophysics Data System (ADS)

Kim, E.; Kim, M.; Hwang, N.; Lee, M. G.; Chun, M.-Y.; Ann, H. B.

2011-04-01

We present a wide-field survey of satellite galaxies in M106 (NGC 4258) covering a ?× 2° field around M106 using Canada-France-Hawaii Telescope/MegaCam. We find 16 satellite galaxy candidates of M106. Eight of these galaxies are found to be dwarf galaxies that are much smaller and fainter than the remaining galaxies. Three of these galaxies are new findings. Surface brightness profiles of 15 out of 16 satellite galaxies can be represented well by an exponential disc profile with varying scalelength. We derive the surface number density distribution of these satellite galaxies. The central number density profile (d < 100 kpc) is well fitted by a power law with a power index of -2.1 ± 0.5, similar to the expected power index of isothermal distribution. The luminosity function of these satellites is represented well by the Schechter function with a faint-end slope of -1.19+0.03-0.06. Integrated photometric properties (total luminosity, total colour and disc scalelength) and the spatial distribution of these satellite galaxies are found to be roughly similar to those of the Milky Way and M31.

Surface Properties and Characteristics of Mars Landing Sites from Remote Sensing Data and Ground Truth

NASA Astrophysics Data System (ADS)

Golombek, M. P.; Haldemann, A. F.; Simpson, R. A.; Furgason, R. L.; Putzig, N. E.; Huertas, A.; Arvidson, R. E.; Heet, T.; Bell, J. F.; Mellon, M. T.; McEwen, A. S.

2008-12-01

Surface characteristics at the six sites where spacecraft have successfully landed on Mars can be related favorably to their signatures in remotely sensed data from orbit and from the Earth. Comparisons of the rock abundance, types and coverage of soils (and their physical properties), thermal inertia, albedo, and topographic slope all agree with orbital remote sensing estimates and show that the materials at the landing sites can be used as ground truth for the materials that make up most of the equatorial and mid- to moderately high-latitude regions of Mars. The six landing sites sample two of the three dominant global thermal inertia and albedo units that cover ~80% of the surface of Mars. The Viking, Spirit, Mars Pathfinder, and Phoenix landing sites are representative of the moderate to high thermal inertia and intermediate to high albedo unit that is dominated by crusty, cloddy, blocky or frozen soils (duricrust that may be layered) with various abundances of rocks and bright dust. The Opportunity landing site is representative of the moderate to high thermal inertia and low albedo surface unit that is relatively dust free and composed of dark eolian sand and/or increased abundance of rocks. Rock abundance derived from orbital thermal differencing techniques in the equatorial regions agrees with that determined from rock counts at the surface and varies from ~3-20% at the landing sites. The size-frequency distributions of rocks >1.5 m diameter fully resolvable in HiRISE images of the landing sites follow exponential models developed from lander measurements of smaller rocks and are continuous with these rock distributions indicating both are part of the same population. Interpretation of radar data confirms the presence of load bearing, relatively dense surfaces controlled by the soil type at the landing sites, regional rock populations from diffuse scattering similar to those observed directly at the sites, and root-mean-squared slopes that compare favorably with 100 m scale topographic slopes extrapolated from altimetry profiles and meter scale slopes from high-resolution stereo images. The third global unit has very low thermal inertia and very high albedo, indicating it is dominated by deposits of bright red atmospheric dust that may be neither load bearing nor trafficable. The landers have thus sampled the majority of likely safe and trafficable surfaces that cover most of Mars and show that remote sensing data can be used to infer the surface characteristics, slopes, and surface materials present at other locations.

The Origin of Regional Dust Deposits on Mars

NASA Technical Reports Server (NTRS)

Christensen, P. R.

1985-01-01

Recently, additional evidence was derived from the Viking Infrared Thermal Mapper observations that allows a more complete model for the formation of Low Thermal inertia-high Albedo regions to be proposed. The first observation is that dust appears to be currently accumulating in the low thermal inertia regions. Following each global dust storm a thin layer of dust is deposited globally, as evidenced by an increase in surface albedo seen from orbit and from the Viking Lander sites. During the period following the storm, the bright dust fallout is subsequently removed from low albedo regions, as indicated by the post-storm darkening of these surfaces and by an increase in the atmospheric dust content over dark regions relative to the bright, low thermal inertia regions. Thus, the fine dust storm material is removed from dark regions but not from the bright regions, resulting in a net accumulation within the bright, low thermal inertia regions. Once deposition has begun, the covering of exposed rocks and sand and the accumulation of fine material on the surface make removal of material increasingly difficult, thereby enhancing the likelihood that material will accumulate within the low thermal inertia regions.

Derivation and Application of a Global Albedo yielding an Optical Brightness To Physical Size Transformation Free of Systematic Errors

NASA Technical Reports Server (NTRS)

Mulrooney, Dr. Mark K.; Matney, Dr. Mark J.

2007-01-01

Orbital object data acquired via optical telescopes can play a crucial role in accurately defining the space environment. Radar systems probe the characteristics of small debris by measuring the reflected electromagnetic energy from an object of the same order of size as the wavelength of the radiation. This signal is affected by electrical conductivity of the bulk of the debris object, as well as its shape and orientation. Optical measurements use reflected solar radiation with wavelengths much smaller than the size of the objects. Just as with radar, the shape and orientation of an object are important, but we only need to consider the surface electrical properties of the debris material (i.e., the surface albedo), not the bulk electromagnetic properties. As a result, these two methods are complementary in that they measure somewhat independent physical properties to estimate the same thing, debris size. Short arc optical observations such as are typical of NASA's Liquid Mirror Telescope (LMT) give enough information to estimate an Assumed Circular Orbit (ACO) and an associated range. This information, combined with the apparent magnitude, can be used to estimate an "absolute" brightness (scaled to a fixed range and phase angle). This absolute magnitude is what is used to estimate debris size. However, the shape and surface albedo effects make the size estimates subject to systematic and random errors, such that it is impossible to ascertain the size of an individual object with any certainty. However, as has been shown with radar debris measurements, that does not preclude the ability to estimate the size distribution of a number of objects statistically. After systematic errors have been eliminated (range errors, phase function assumptions, photometry) there remains a random geometric albedo distribution that relates object size to absolute magnitude. Measurements by the LMT of a subset of tracked debris objects with sizes estimated from their radar cross sections indicate that the random variations in the albedo follow a log-normal distribution quite well. In addition, this distribution appears to be independent of object size over a considerable range in size. Note that this relation appears to hold for debris only, where the shapes and other properties are not primarily the result of human manufacture, but of random processes. With this information in hand, it now becomes possible to estimate the actual size distribution we are sampling from. We have identified two characteristics of the space debris population that make this process tractable and by extension have developed a methodology for performing the transformation.

Colors and Photometry of Bright Materials on Vesta as Seen by the Dawn Framing Camera

NASA Technical Reports Server (NTRS)

Schroeder, S. E.; Li, J.-Y.; Mittlefehldt, D. W.; Pieters, C. M.; De Sanctis, M. C.; Hiesinger, H.; Blewett, D. T.; Russell, C. T.; Raymond, C. A.; Keller, H. U.;

Rear surface light emission measurements from laser-produced shock waves in clear and Al-coated polystyrene targets

NASA Astrophysics Data System (ADS)

McLean, E. A.; Deniz, A. V.; Schmitt, A. J.; Stamper, J. A.; Obenschain, S. P.; Lehecka, T.; Mostovych, A. N.; Seely, J.

1999-08-01

The Nike KrF laser, with its very uniform focal distributions, has been used at intensities near 10 14 W/cm 2 to launch shock waves in polystyrene targets. The rear surface visible light emission differed between clear polystyrene (CH) targets and targets with a thin (125 nm) Al coating on the rear side. The uncoated CH targets showed a relatively slowly rising emission followed by a sudden fall when the shock emerges, while the Al-coated targets showed a rapid rise in emission when the shock emerges followed by a slower fall, allowing an unambiguous determination of the time the shock arrived at the rear surface. A half-aluminized target allowed us to observe this difference in a single shot. The brightness temperature of both the aluminized targets and the non-aluminized targets was slightly below but close to rear surface temperature predictions of a hydrodynamic code. A discussion of preheat effects is given.

Photographer : JPL Range : 7 million kilometers (5 million miles) Callisto is Jupiter's outermost

NASA Technical Reports Server (NTRS)

1979-01-01

Photographer : JPL Range : 7 million kilometers (5 million miles) Callisto is Jupiter's outermost Galilean satellites and darkest of the four(but almost twice as bright as Earth's Moon). Mottled appearance from bright and dark patches. Bright spots seem like rayed or bright halved craters seen on our Moon. This face is always turned toward Jupiter. Photo taken through violet filter. Ganymede is slightly larger than Mercury but much less dense (twice the density of water). Its surface brightness is 4 times of Earth's Moon. Mare regions (dark features) are like the Moon's but have twice the brightness, and believed to be unlikely of rock or lava as the Moon's are. It's north pole seems covered with brighter material and may be water frost. Scattered brighter spots may be related to impact craters or source of fresh ice.

Results of soil moisture flights during April 1974

NASA Technical Reports Server (NTRS)

Schmugge, T. J.; Blanchard, B. J.; Burke, W. J.; Paris, J. F.; Swang, J. R.

1976-01-01

The results presented here are derived from measurements made during the April 5 and 6, 1974 flights of the NASA P-3A aircraft over the Phoenix, Arizona agricultural test site. The purpose of the mission was to study the use of microwave techniques for the remote sensing of soil moisture. These results include infrared (10-to 12 micrometers) 2.8-cm and 21-cm brightness temperatures for approximately 90 bare fields. These brightness temperatures are compared with surface measurements of the soil moisture made at the time of the overflights. These data indicate that the combination of the sum and difference of the vertically and the horizontally polarized brightness temperatures yield information on both the soil moisture and surface roughness conditions.

Evidence of Space Weathering Processes Across the Surface of Vesta

NASA Technical Reports Server (NTRS)

Pieters, Carle M.; Blewett, David T.; Gaffey, Michael; Mittlefehldt, David W.; CristinaDeSanctis, Maria; Reddy, Vishnu; Coradini, Angioletta; Nathues, Andreas; Denevi, Brett W.; Li, Jian-Yang;

Eight ultra-faint galaxy candidates discovered in year two of the Dark Energy Survey

DOE PAGES

Drlica-Wagner, A.

2015-11-04

Here, we report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. The new systems are faint (M V > –4.7more » $$\\mathrm{mag}$$) and span a range of physical sizes (17 $$\\mathrm{pc}$$ < r 1/2 < 181 $$\\mathrm{pc}$$) and heliocentric distances (25 kpc < D ⊙ < 214 kpc). All of the new systems have central surface brightnesses consistent with known ultra-faint dwarf galaxies (μ ≳ 27.5 $$\\mathrm{mag}$$ $$\\mathrm{arcsec}$$ –2). Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known Milky Way satellite galaxies. Most of the candidates are found in the southern part of the DES footprint close to the Magellanic Clouds. We find that the DES data alone exclude (p < 10 –3) a spatially isotropic distribution of Milky Way satellites and that the observed distribution can be well, though not uniquely, described by an association between several of the DES satellites and the Magellanic system. Our model predicts that the full sky may hold ~100 ultra-faint galaxies with physical properties comparable to the DES satellites and that 20%–30% of these would be spatially associated with the Magellanic Clouds.« less

Narrow-stripe broad-area lasers with distributed-feedback surface gratings as brilliant sources for high power spectral beam combining systems

NASA Astrophysics Data System (ADS)

Decker, J.; Crump, P.; Fricke, J.; Wenzel, H.; Maaβdorf, A.; Erbert, G.; Tränkle, G.

2014-03-01

Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam param- eter product, BPP, of the BA lasers, which operate with a BPP of < 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal ber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), μV 95. The resulting diode lasers are fabricated as mini- bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single bre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC sys- tems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 μm, successfully cut of higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high e ciency. To date, such DFB-NBA sources operate with < 50% effciency at output power, Pout < 6 W, with BPP < 1.8 mm-mrad and offV 95 36 . The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 um. We conclude with a review of options for further performance improvements.

The Herschel-ATLAS: magnifications and physical sizes of 500-μm-selected strongly lensed galaxies

NASA Astrophysics Data System (ADS)

Enia, A.; Negrello, M.; Gurwell, M.; Dye, S.; Rodighiero, G.; Massardi, M.; De Zotti, G.; Franceschini, A.; Cooray, A.; van der Werf, P.; Birkinshaw, M.; Michałowski, M. J.; Oteo, I.

2018-04-01

We perform lens modelling and source reconstruction of Sub-millimetre Array (SMA) data for a sample of 12 strongly lensed galaxies selected at 500μm in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). A previous analysis of the same data set used a single Sérsic profile to model the light distribution of each background galaxy. Here we model the source brightness distribution with an adaptive pixel scale scheme, extended to work in the Fourier visibility space of interferometry. We also present new SMA observations for seven other candidate lensed galaxies from the H-ATLAS sample. Our derived lens model parameters are in general consistent with previous findings. However, our estimated magnification factors, ranging from 3 to 10, are lower. The discrepancies are observed in particular where the reconstructed source hints at the presence of multiple knots of emission. We define an effective radius of the reconstructed sources based on the area in the source plane where emission is detected above 5σ. We also fit the reconstructed source surface brightness with an elliptical Gaussian model. We derive a median value reff ˜ 1.77 kpc and a median Gaussian full width at half-maximum ˜1.47 kpc. After correction for magnification, our sources have intrinsic star formation rates (SFR) ˜ 900-3500 M⊙ yr-1, resulting in a median SFR surface density ΣSFR ˜ 132 M⊙ yr-1 kpc-2 (or ˜218 M⊙ yr-1 kpc-2 for the Gaussian fit). This is consistent with that observed for other star-forming galaxies at similar redshifts, and is significantly below the Eddington limit for a radiation pressure regulated starburst.

Solo dwarfs I: survey introduction and first results for the Sagittarius dwarf irregular galaxy

NASA Astrophysics Data System (ADS)

Higgs, C. R.; McConnachie, A. W.; Irwin, M.; Bate, N. F.; Lewis, G. F.; Walker, M. G.; Côté, P.; Venn, K.; Battaglia, G.

2016-05-01

We introduce the Solitary Local dwarfs survey (Solo), a wide-field photometric study targeting every isolated dwarf galaxy within 3 Mpc of the Milky Way. Solo is based on (u)gi multiband imaging from Canada-France-Hawaii Telescope/MegaCam for northern targets, and Magellan/Megacam for southern targets. All galaxies fainter than MV ≃ -18 situated beyond the nominal virial radius of the Milky Way and M31 (≳300 kpc) are included in this volume-limited sample, for a total of 42 targets. In addition to reviewing the survey goals and strategy, we present results for the Sagittarius dwarf irregular galaxy (Sag DIG), one of the most isolated, low-mass galaxies, located at the edge of the Local Group. We analyse its resolved stellar populations and their spatial distributions. We provide updated estimates of its central surface brightness and integrated luminosity, and trace its surface brightness profile to a level fainter than 30 mag arcsec-2. Sag DIG is well described by a highly elliptical (disc-like) system following a single component Sérsic model. However, a low-level distortion is present at the outer edges of the galaxy that, were Sag DIG not so isolated, would likely be attributed to some kind of previous tidal interaction. Further, we find evidence of an extremely low level, extended distribution of stars beyond ˜5 arcmin (>1.5 kpc) that suggests Sag DIG may be embedded in a very low-density stellar halo. We compare the stellar and H I structures of Sag DIG, and discuss results for this galaxy in relation to other isolated, dwarf irregular galaxies in the Local Group.

STELLAR POPULATIONS AND THE STAR FORMATION HISTORIES OF LSB GALAXIES. V. WFC3 COLOR–MAGNITUDE DIAGRAMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schombert, James; McGaugh, Stacy, E-mail: jschombe@uoregon.edu, E-mail: stacy.mcgaugh@case.edu

2015-09-15

We present WFC3 observations of three low surface brightness (LSB) galaxies from the Schombert et al. LSB catalog that are within 11 Mpc of the Milky Way. Deep imaging at F336W, F555W, and F814W allow the construction of the V − I color–magnitude diagrams (CMD) to M{sub I} = −2. Overall 1869, 465, and 501 stellar sources are identified in the three LSB galaxies F415-3, F608-1, and F750-V1, respectively. The spatial distribution of young blue stars matches the Hα maps from ground-based imaging, indicating that star formation in LSB galaxies follows the same style as in other irregular galaxies. Severalmore » star complexes are identified, matching regions of higher surface brightness as seen from ground-based imaging. The CMD for each LSB galaxy has a similar morphology to Local Volume (LV) dwarf galaxies (i.e., a blue main sequence, blue and red He burning branches, and asymptotic giant branch (AGB) stars). The LSB CMD’s distinguish themselves from nearby dwarf CMD’s by having a higher proportion of blue main sequence stars and fewer AGB stars than expected from their mean metallicities. Current [Fe/H] values below −0.6 are deduced from the position of the red helium-burning branch (rHeB) stars in the V − I diagram. The distribution of stars on the blue helium-burning branch (bHeB) and rHeB from the U − V and V − I CMD indicate a history of constant star formation for the last 100 Myr.« less

Eight ultra-faint galaxy candidates discovered in year two of the Dark Energy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drlica-Wagner, A.

Here, we report the discovery of eight new ultra-faint dwarf galaxy candidates in the second year of optical imaging data from the Dark Energy Survey (DES). Six of these candidates are detected at high confidence, while two lower-confidence candidates are identified in regions of non-uniform survey coverage. The new stellar systems are found by three independent automated search techniques and are identified as overdensities of stars, consistent with the isochrone and luminosity function of an old and metal-poor simple stellar population. The new systems are faint (M V > –4.7more » $$\\mathrm{mag}$$) and span a range of physical sizes (17 $$\\mathrm{pc}$$ < r 1/2 < 181 $$\\mathrm{pc}$$) and heliocentric distances (25 kpc < D ⊙ < 214 kpc). All of the new systems have central surface brightnesses consistent with known ultra-faint dwarf galaxies (μ ≳ 27.5 $$\\mathrm{mag}$$ $$\\mathrm{arcsec}$$ –2). Roughly half of the DES candidates are more distant, less luminous, and/or have lower surface brightnesses than previously known Milky Way satellite galaxies. Most of the candidates are found in the southern part of the DES footprint close to the Magellanic Clouds. We find that the DES data alone exclude (p < 10 –3) a spatially isotropic distribution of Milky Way satellites and that the observed distribution can be well, though not uniquely, described by an association between several of the DES satellites and the Magellanic system. Our model predicts that the full sky may hold ~100 ultra-faint galaxies with physical properties comparable to the DES satellites and that 20%–30% of these would be spatially associated with the Magellanic Clouds.« less

THE DISTRIBUTION AND CHEMISTRY OF H{sub 2}CO IN THE DM TAU PROTOPLANETARY DISK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loomis, Ryan A.; Öberg, Karin I.; Guzman, Viviana V.

H{sub 2}CO ice on dust grains is an important precursor of complex organic molecules (COMs). H{sub 2}CO gas can be readily observed in protoplanetary disks and may be used to trace COM chemistry. However, its utility as a COM probe is currently limited by a lack of constraints on the relative contributions of two different formation pathways: on icy grain surfaces and in the gas phase. We use archival Atacama Large (sub-)Millimeter Array observations of the resolved distribution of H{sub 2}CO emission in the disk around the young low-mass star DM Tau to assess the relative importance of these formationmore » routes. The observed H{sub 2}CO emission has a centrally peaked and radially broad brightness profile (extending out to 500 AU). We compare these observations with disk chemistry models with and without grain-surface formation reactions and find that both gas and grain-surface chemistry are necessary to explain the spatial distribution of the emission. Gas-phase H{sub 2}CO production is responsible for the observed central peak, while grain-surface chemistry is required to reproduce the emission exterior to the CO snow line (where H{sub 2}CO mainly forms through the hydrogenation of CO ice before being non-thermally desorbed). These observations demonstrate that both gas and grain-surface pathways contribute to the observed H{sub 2}CO in disks and that their relative contributions depend strongly on distance from the host star.« less

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Implications for Spectral Line Intensity Mapping at Millimeter Wavelengths and CMB Spectral Distortions

NASA Astrophysics Data System (ADS)

Carilli, C. L.; Chluba, J.; Decarli, R.; Walter, F.; Aravena, M.; Wagg, J.; Popping, G.; Cortes, P.; Hodge, J.; Weiss, A.; Bertoldi, F.; Riechers, D.

2016-12-01

We present direct estimates of the mean sky brightness temperature in observing bands around 99 and 242 GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for spectral line emission from high redshift galaxies using ALMA (the ALMA spectral deep field observations “ASPECS” survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242 GHz band, the emission could be a combination of higher order CO lines, and possibly [C II] 158 μm line emission from very high redshift galaxies (z ˜ 6-7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99 GHZ band is: T B = 0.94 ± 0.09 μK. In the 242 GHz band, the mean brightness is: T B = 0.55 ± 0.033 μK. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey.

Interferometric Constraints on Surface Brightness Asymmetries in Long-Period Variable Stars: A Threat to Accurate Gaia Parallaxes

NASA Astrophysics Data System (ADS)

Sacuto, S.; Jorissen, A.; Cruzalèbes, P.; Pasquato, E.; Chiavassa, A.; Spang, A.; Rabbia, Y.; Chesneau, O.

2011-09-01

A monitoring of surface brightness asymmetries in evolved giants and supergiants is necessary to estimate the threat that they represent to accurate Gaia parallaxes. Closure-phase measurements obtained with AMBER/VISA in a 3-telescope configuration are fitted by a simple model to constrain the photocenter displacement. The results for the C-type star TX Psc show a large deviation of the photocenter displacement that could bias the Gaia parallax.

Evaluation and Analysis of Seasat a Scanning Multichannel Microwave Radiometer (SMMR) Antenna Pattern Correction (APC) Algorithm

NASA Technical Reports Server (NTRS)

Kitzis, S. N.; Kitzis, J. L.

1979-01-01

The accuracy of the SEASAT-A SMMR antenna pattern correction (APC) algorithm was assessed. Interim APC brightness temperature measurements for the SMMR 6.6 GHz channels are compared with surface truth derived sea surface temperatures. Plots and associated statistics are presented for SEASAT-A SMMR data acquired for the Gulf of Alaska experiment. The cross-track gradients observed in the 6.6 GHz brightness temperature data are discussed.

Simulating a slow bar in the low surface brightness galaxy UGC 628

NASA Astrophysics Data System (ADS)

Chequers, Matthew H.; Spekkens, Kristine; Widrow, Lawrence M.; Gilhuly, Colleen

2016-12-01

We present a disc-halo N-body model of the low surface brightness galaxy UGC 628, one of the few systems that harbours a `slow' bar with a ratio of corotation radius to bar length of R ≡ R_c/a_b ˜ 2. We select our initial conditions using SDSS DR10 photometry, a physically motivated radially variable mass-to-light ratio profile, and rotation curve data from the literature. A global bar instability grows in our submaximal disc model, and the disc morphology and dynamics agree broadly with the photometry and kinematics of UGC 628 at times between peak bar strength and the onset of buckling. Prior to bar formation, the disc and halo contribute roughly equally to the potential in the galaxy's inner region, giving the disc enough self-gravity for bar modes to grow. After bar formation, there is significant mass redistribution, creating a baryon-dominated inner and dark matter-dominated outer disc. This implies that, unlike most other low surface brightness galaxies, UGC 628 is not dark matter dominated everywhere. Our model nonetheless implies that UGC 628 falls on the same relationship between dark matter fraction and rotation velocity found for high surface brightness galaxies, and lends credence to the argument that the disc mass fraction measured at the location where its contribution to the potential peaks is not a reliable indicator of its dynamical importance at all radii.

Pioneer 10 observations of zodiacal light brightness near the ecliptic - Changes with heliocentric distance

NASA Technical Reports Server (NTRS)

Hanner, M. S.; Weinberg, J. L.; Beeson, D. E.; Sparrow, J. G.

1976-01-01

Sky maps made by the Pioneer 10 Imaging Photopolarimeter (IPP) at sun-spacecraft distances from 1 to 3 AU have been analyzed to derive the brightness of the zodiacal light near the ecliptic at elongations greater than 90 degrees. The change in zodiacal light brightness with heliocentric distance is compared with models of the spatial distribution of the dust. Use of background starlight brightnesses derived from IPP measurements beyond the asteroid belt, where the zodiacal light is not detected, and, especially, use of a corrected calibration lead to considerably lower values for zodiacal light than those reported by us previously.

Improved mapping of radio sources from VLBI data by least-square fit

NASA Technical Reports Server (NTRS)

Rodemich, E. R.

1985-01-01

A method is described for producing improved mapping of radio sources from Very Long Base Interferometry (VLBI) data. The method described is more direct than existing Fourier methods, is often more accurate, and runs at least as fast. The visibility data is modeled here, as in existing methods, as a function of the unknown brightness distribution and the unknown antenna gains and phases. These unknowns are chosen so that the resulting function values are as near as possible to the observed values. If researchers use the radio mapping source deviation to measure the closeness of this fit to the observed values, they are led to the problem of minimizing a certain function of all the unknown parameters. This minimization problem cannot be solved directly, but it can be attacked by iterative methods which we show converge automatically to the minimum with no user intervention. The resulting brightness distribution will furnish the best fit to the data among all brightness distributions of given resolution.

Remote sensing of soil moisture content over bare fields at 1.4 GHz frequency

NASA Technical Reports Server (NTRS)

Wang, J. R.; Choudhury, B. J.

1980-01-01

A simple method of estimating moisture content (W) of a bare soil from the observed brightness temperature (T sub B) at 1.4 GHz is discussed. The method is based on a radiative transfer model calculation, which has been successfully used in the past to account for many observational results, with some modifications to take into account the effect of surface roughness. Besides the measured T sub B's, the three additional inputs required by the method are the effective soil thermodynamic temperature, the precise relation between W and the smooth field brightness temperature T sub B and a parameter specifying the surface roughness characteristics. The soil effective temperature can be readily measured and the procedures of estimating surface roughness parameter and obtaining the relation between W and smooth field brightness temperature are discussed in detail. Dual polarized radiometric measurements at an off-nadir incident angle are sufficient to estimate both surface roughness parameter and W, provided that the relation between W and smooth field brightness temperature at the same angle is known. The method of W estimate is demonstrated with two sets of experimental data, one from a controlled field experiment by a mobile tower and the other, from aircraft overflight. The results from both data sets are encouraging when the estimated W's are compared with the acquired ground truth of W's in the top 2 cm layer. An offset between the estimated and the measured W's exists in the results of the analyses, but that can be accounted for by the presently poor knowledge of the relationship between W and smooth field brightness temperature for various types of soils. An approach to quantify this relationship for different soils and thus improve the method of W estimate is suggested.

ZTF Bright Transient Survey classifications

NASA Astrophysics Data System (ADS)

Fremling, C.; Sharma, Y.; Skulkarni, S. R.; Walters, R.; Blagorodnova, N.; Neill, J. D.; Miller, A. A.; Taggart, K.; Perley, D. A.; Goobar, A.; Graham, M. L.

2018-06-01

The Zwicky Transient Facility (ZTF; ATel #11266) Bright Transient Survey (BTS; ATel #11688) reports classifications of the following targets. Spectra have been obtained with the Spectral Energy Distribution Machine (SEDM) (range 350-950nm, spectral resolution R 100) mounted on the Palomar 60-inch (P60) telescope (Blagorodnova et. al. 2018, PASP, 130, 5003).

The response of the SSM/I to the marine environment. I - An analytic model for the atmospheric component of observed brightness temperatures

NASA Technical Reports Server (NTRS)

Petty, Grant W.; Katsaros, Kristina B.

1992-01-01

A detailed parameterization is developed for the contribution of the nonprecipitating atmosphere to the microwave brightness temperatures observed by the Special Sensor Microwave/Imager (SSM/I). The atmospheric variables considered include the viewing angle, the integrated water vapor amount and scale height, the effective tropospheric lapse rate and near-surface temperature, the total cloud liquid water, the effective cloud height, and the surface pressure. The dependence of the radiative variables on meteorological variables is determined for each of the SSM/I frequencies 19.35, 22.235, 37.0, and 85.5 GHz, based on the values computed from 16,893 maritime temperature and humidity profiles representing all latitude belts and all seasons. A comparison of the predicted brightness temperatures with brightness temperatures obtained by direct numerical integration of the radiative transfer equation for the radiosonde-profile dataset yielded rms differences well below 1 K for all four SSM/I frequencies.

Bright colloidal quantum dot light-emitting diodes enabled by efficient chlorination

NASA Astrophysics Data System (ADS)

Li, Xiyan; Zhao, Yong-Biao; Fan, Fengjia; Levina, Larissa; Liu, Min; Quintero-Bermudez, Rafael; Gong, Xiwen; Quan, Li Na; Fan, James; Yang, Zhenyu; Hoogland, Sjoerd; Voznyy, Oleksandr; Lu, Zheng-Hong; Sargent, Edward H.

2018-03-01

The external quantum efficiencies of state-of-the-art colloidal quantum dot light-emitting diodes (QLEDs) are now approaching the limit set by the out-coupling efficiency. However, the brightness of these devices is constrained by the use of poorly conducting emitting layers, a consequence of the present-day reliance on long-chain organic capping ligands. Here, we report how conductive and passivating halides can be implemented in Zn chalcogenide-shelled colloidal quantum dots to enable high-brightness green QLEDs. We use a surface management reagent, thionyl chloride (SOCl2), to chlorinate the carboxylic group of oleic acid and graft the surfaces of the colloidal quantum dots with passivating chloride anions. This results in devices with an improved mobility that retain high external quantum efficiencies in the high-injection-current region and also feature a reduced turn-on voltage of 2.5 V. The treated QLEDs operate with a brightness of 460,000 cd m-2, significantly exceeding that of all previously reported solution-processed LEDs.

A radar image of Venus.

NASA Technical Reports Server (NTRS)

Goldstein, R. M.; Rumsey, H. C.

1972-01-01

Radar scans of Venus have yielded a brightness map of a large portion of the surface. The bright area in the south (alpha) and the twin such areas in the north (beta and delta) were first discovered by spectral analysis of radar echos. When range-gating is also applied, their shapes are revealed, and they are seen to be roundish and about 1000 km across. Although radar brightness can be the result of either intrinsic reflectivity or surface roughness, polarization studies show these features to be rough (to the scale of the wavelength, 12.5 cm). Dark, circular areas can also be seen, many with bright central spots. The dark areas are probably smooth. The blurring of the equatorial strip is an artifact of the range-Doppler geometry; all resolution disappears at the equator. Another artifact of the method is the 'ghost', in the south, of the images of beta and delta. Such ghosts appear only at the eastern and western extremes of the map.

First direct visualization of spillover species emitted from pt nanoparticles.

PubMed

Takakusagi, Satoru; Fukui, Ken-ichi; Tero, Ryugo; Asakura, Kiyotaka; Iwasawa, Yasuhiro

2010-11-02

We studied the methanol adsorption behavior of Pt nanoparticles that were vacuum-deposited on a TiO(2)(110) surface at room temperature by using an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). A large number of bright spots were observed on fivefold-coordinated Ti (Ti(5c)) rows of the TiO(2)(110) surface after exposure of the Pt/TiO(2)(110) to methanol vapor. We assigned the bright spots to methoxy species. These were mobile and were found to hop along the Ti(5c) rows. In situ time-resolved STM observations of the formation and migration of the bright spots on the Pt/TiO(2)(110) were carried out in the presence of methanol. The bright spots were produced at the periphery of the Pt nanoparticles and migrated to the substrate Ti(5c) rows. We discuss the spillover process and behavior of the methoxy species on the Pt/TiO(2)(110).

Radial distributions of surface mass density and mass-to-luminosity ratio in spiral galaxies

NASA Astrophysics Data System (ADS)

Sofue, Yoshiaki

2018-03-01

We present radial profiles of the surface mass density (SMD) in spiral galaxies directly calculated using rotation curves of two approximations of flat-disk (SMD-F) and spherical mass distribution (SMD-S). The SMDs are combined with surface brightness using photometric data to derive radial variations of the mass-to-luminosity ratio (ML). It is found that the ML generally has a central peak or a plateau, and decreases to a local minimum at R ˜ 0.1-0.2 h, where R is the radius and h is the scale radius of optical disk. The ML, then, increases rapidly until ˜0.5 h, and is followed by gradual rise till ˜2 h, remaining at around ˜2 [M_{⊙} L^{-1}_{⊙}] in the w1 band (infrared λ3.4 μm) and ˜ 10 [M_⊙ L_⊙ ^{-1}] in the r band (λ6200-7500 Å). Beyond this radius, the ML increases steeply with approaching the observed edges at R ˜ 5 h, attaining to as high values as ˜20 in w1 and ˜ 10^2 [M_⊙ L_⊙ ^{-1}] in the r band, which are indicative of dominant dark matter. The general properties of the ML distributions will be useful for constraining cosmological formation models of spiral galaxies.

Towards Understanding the Timing and Frequency of Rain-on-Snow (ROS) Events in Alaska

NASA Astrophysics Data System (ADS)

Pan, C.; Kirchner, P. B.; Kimball, J. S.; Kim, Y.; Kamp, U.

2017-12-01

Rain-on-snow (ROS) events affect ecosystem processes at multiple spatial and temporal scales including hydrology, carbon cycling, wildlife movement and human transportation and result in marked changes to snowpack processes including enhanced snow melt, surface albedo and energy balance. Changes in the surface structure of the snowpack are visible through optical remote sensing and changes in the relative content and distribution of water, air and ice in the snowpack are detectable using passive microwave remote sensing. This project aims to develop ROS products to elucidate changes in frequency and distribution in ROS events using satellite data products derived from both optical and passive microwave satellite records. To detect ROS events, we use downscaled brightness temperature measurements derived from vertical and horizontal polarizations at 19 and 37 GHz from the Advanced Microwave Scanning Radiometer (AMSR-E/2) passive microwave satellites. Preliminary results indicate an overall classification accuracy of 77.6% relative to in situ weather observations including surface air temperature, precipitation, and snow depth. ROS events are spatially distributed largely to elevations below 500 m and occur most frequently on northern to western aspects in addition to southeastern. Regional ROS hot spots occur in southwest Alaska characterized by warmer climates and transient snowcover. The seasonal timing of ROS events indicates increasing frequency during the fall and spring months.

CD94 surface density identifies a functional intermediary between the CD56bright and CD56dim human NK-cell subsets

PubMed Central

Mao, Hsiaoyin C.; Wei, Min; Hughes, Tiffany; Zhang, Jianying; Park, Il-kyoo; Liu, Shujun; McClory, Susan; Marcucci, Guido; Trotta, Rossana

2010-01-01

Human CD56bright natural killer (NK) cells possess little or no killer immunoglobulin-like receptors (KIRs), high interferon-γ (IFN-γ) production, but little cytotoxicity. CD56dim NK cells have high KIR expression, produce little IFN-γ, yet display high cytotoxicity. We hypothesized that, if human NK maturation progresses from a CD56bright to a CD56dim phenotype, an intermediary NK cell must exist, which demonstrates more functional overlap than these 2 subsets, and we used CD94 expression to test our hypothesis. CD94highCD56dim NK cells express CD62L, CD2, and KIR at levels between CD56bright and CD94lowCD56dim NK cells. CD94highCD56dim NK cells produce less monokine-induced IFN-γ than CD56bright NK cells but much more than CD94lowCD56dim NK cells because of differential interleukin-12–mediated STAT4 phosphorylation. CD94highCD56dim NK cells possess a higher level of granzyme B and perforin expression and CD94-mediated redirected killing than CD56bright NK cells but lower than CD94lowCD56dim NK cells. Collectively, our data suggest that the density of CD94 surface expression on CD56dim NK cells identifies a functional and likely developmental intermediary between CD56bright and CD94lowCD56dim NK cells. This supports the notion that, in vivo, human CD56bright NK cells progress through a continuum of differentiation that ends with a CD94lowCD56dim phenotype. PMID:19897577

CD94 surface density identifies a functional intermediary between the CD56bright and CD56dim human NK-cell subsets.

PubMed

Yu, Jianhua; Mao, Hsiaoyin C; Wei, Min; Hughes, Tiffany; Zhang, Jianying; Park, Il-kyoo; Liu, Shujun; McClory, Susan; Marcucci, Guido; Trotta, Rossana; Caligiuri, Michael A

2010-01-14

Human CD56(bright) natural killer (NK) cells possess little or no killer immunoglobulin-like receptors (KIRs), high interferon-gamma (IFN-gamma) production, but little cytotoxicity. CD56(dim) NK cells have high KIR expression, produce little IFN-gamma, yet display high cytotoxicity. We hypothesized that, if human NK maturation progresses from a CD56(bright) to a CD56(dim) phenotype, an intermediary NK cell must exist, which demonstrates more functional overlap than these 2 subsets, and we used CD94 expression to test our hypothesis. CD94(high)CD56(dim) NK cells express CD62L, CD2, and KIR at levels between CD56(bright) and CD94(low)CD56(dim) NK cells. CD94(high)CD56(dim) NK cells produce less monokine-induced IFN-gamma than CD56(bright) NK cells but much more than CD94(low)CD56(dim) NK cells because of differential interleukin-12-mediated STAT4 phosphorylation. CD94(high)CD56(dim) NK cells possess a higher level of granzyme B and perforin expression and CD94-mediated redirected killing than CD56(bright) NK cells but lower than CD94(low)CD56(dim) NK cells. Collectively, our data suggest that the density of CD94 surface expression on CD56(dim) NK cells identifies a functional and likely developmental intermediary between CD56(bright) and CD94(low)CD56(dim) NK cells. This supports the notion that, in vivo, human CD56(bright) NK cells progress through a continuum of differentiation that ends with a CD94(low)CD56(dim) phenotype.

Surface-plasmon resonance-enhanced multiphoton emission of high-brightness electron beams from a nanostructured copper cathode.

PubMed

Li, R K; To, H; Andonian, G; Feng, J; Polyakov, A; Scoby, C M; Thompson, K; Wan, W; Padmore, H A; Musumeci, P

2013-02-15

We experimentally investigate surface-plasmon assisted photoemission to enhance the efficiency of metallic photocathodes for high-brightness electron sources. A nanohole array-based copper surface was designed to exhibit a plasmonic response at 800 nm, fabricated using the focused ion beam milling technique, optically characterized and tested as a photocathode in a high power radio frequency photoinjector. Because of the larger absorption and localization of the optical field intensity, the charge yield observed under ultrashort laser pulse illumination is increased by more than 100 times compared to a flat surface. We also present the first beam characterization results (intrinsic emittance and bunch length) from a nanostructured photocathode.

Extending the Deep Blue aerosol record from SeaWiFS and MODIS to NPP-VIIRS

NASA Technical Reports Server (NTRS)

Sayer, Andrew M.; Hsu, Nai-Yung Christina; Bettenhausen, Corey; Lee, Jaehwa

2015-01-01

Deep Blue expands AOD coverage to deserts and other bright surfaces. Using multiple similar satellite sensors enables us to obtain a long data record. The Deep Blue family consists of three separate aerosol optical depth (AOD) retrieval algorithms: 1. Bright Land: Surface reflectance database, BRDF correction. AOD retrieved separately at each of 412, 470/490, (650) nm. SSA retrieved for heavy dust events. 2. Dark Land: Spectral/directional surface reflectance relationship. AOD retrieved separately at 470/490 and 650 nm. 3. Water: Surface BRDF including glint, foam, underlight. Multispectral inversion (Not present in MODISdataset) All report the AOD at 550 nm, and Ångström exponent (AE).

Hunting Faint Dwarf Galaxies in the Field Using Integrated Light Surveys

NASA Astrophysics Data System (ADS)

Danieli, Shany; van Dokkum, Pieter; Conroy, Charlie

2018-03-01

We discuss the approach of searching the lowest mass dwarf galaxies, ≲ {10}6 {M}ȯ , in the general field, using integrated light surveys. By exploring the limiting surface brightness-spatial resolution (μ eff,lim‑θ) parameter space, we suggest that faint field dwarfs in the Local Volume, between 3 and 10 Mpc, are expected to be detected very effectively and in large numbers using integrated light photometric surveys, complementary to the classical star counts method. We use a sample of dwarf galaxies in the Local Group to construct relations between their photometric and structural parameters, M *–μ eff,V and M *–R eff. We use these relations, along with assumed functional forms for the halo mass function and the stellar mass–halo mass (SMHM) relation, to calculate the lowest detectable stellar masses in the Local Volume and the expected number of galaxies as a function of the limiting surface brightness and spatial resolution. The number of detected galaxies depends mostly on the limiting surface brightness for distances >3 Mpc, while spatial resolution starts to play a role for galaxies at distances >8 Mpc. Surveys with μ eff,lim ∼ 30 mag arcsec‑2 should be able to detect galaxies with stellar masses down to ∼104 M ⊙ in the Local Volume. Depending on the form of the SMHM relation, the expected number of dwarf galaxies with distances between 3 and 10 Mpc is 0.04–0.35 per square degree, assuming a limiting surface brightness of ∼29–30 mag arcsec‑2 and a spatial resolution <4″. We plan to search for a population of low-mass dwarf galaxies in the field by performing a blank wide field photometric survey with the Dragonfly Telephoto Array, an imaging system optimized for the detection of extended ultra low surface brightness structures.

Surface-induced brightness temperature variations and their effects on detecting thin cirrus clouds using IR emission channels in the 8-12 micrometer region

NASA Technical Reports Server (NTRS)

Gao, Bo-Cai; Wiscombe, W. J.

1993-01-01

A method for detecting cirrus clouds in terms of brightness temperature differences between narrow bands at 8, 11, and 12 mu m has been proposed by Ackerman et al. (1990). In this method, the variation of emissivity with wavelength for different surface targets was not taken into consideration. Based on state-of-the-art laboratory measurements of reflectance spectra of terrestrial materials by Salisbury and D'Aria (1992), we have found that the brightness temperature differences between the 8 and 11 mu m bands for soils, rocks and minerals, and dry vegetation can vary between approximately -8 K and +8 K due solely to surface emissivity variations. We conclude that although the method of Ackerman et al. is useful for detecting cirrus clouds over areas covered by green vegetation, water, and ice, it is less effective for detecting cirrus clouds over areas covered by bare soils, rocks and minerals, and dry vegetation. In addition, we recommend that in future the variation of surface emissivity with wavelength should be taken into account in algorithms for retrieving surface temperatures and low-level atmospheric temperature and water vapor profiles.

Analytical Retrieval of Global Land Surface Emissivity Maps at AMSR-E passive microwave frequencies

NASA Astrophysics Data System (ADS)

Norouzi, H.; Temimi, M.; Khanbilvardi, R.

2009-12-01

Land emissivity is a crucial boundary condition in Numerical Weather Prediction (NWP) modeling. Land emissivity is also a key indicator of land surface and subsurface properties. The objective of this study, supported by NOAA-NESDIS, is to develop global land emissivity maps using AMSR-E passive microwave measurements along with several ancillary data. The International Satellite Cloud Climatology Project (ISCCP) database has been used to obtain several inputs for the proposed approach such as land surface temperature, cloud mask and atmosphere profile. The Community Radiative Transfer Model (CRTM) has been used to estimate upwelling and downwelling atmospheric contributions. Although it is well known that correction of the atmospheric effect on brightness temperature is required at higher frequencies (over 19 GHz), our preliminary results have shown that a correction at 10.7 GHz is also necessary over specific areas. The proposed approach is based on three main steps. First, all necessary data have been collected and processed. Second, a global cloud free composite of AMSR-E data and corresponding ancillary images is created. Finally, monthly composting of emissivity maps has been performed. AMSR-E frequencies at 6.9, 10.7, 18.7, 36.5 and 89.0 GHz have been used to retrieve the emissivity. Water vapor information obtained from ISCCP (TOVS data) was used to calculate upwelling, downwelling temperatures and atmospheric transmission in order to assess the consistency of those derived from the CRTM model. The frequent land surface temperature (LST) determination (8 times a day) in the ISCCP database has allowed us to assess the diurnal cycle effect on emissivity retrieval. Differences in magnitude and phase between thermal temperature and low frequencies microwave brightness temperature have been noticed. These differences seem to vary in space and time. They also depend on soil texture and thermal inertia. The proposed methodology accounts for these factors and resultant differences in phase and magnitude between LST and microwave brightness temperature. Additional factors such as topography and vegetation cover are under investigation. In addition, the potential of extrapolating the obtained land emissivity maps to different window and sounding channels has been also investigated in this study. The extrapolation of obtained emissivities to different incident angles is also under investigation. Land emissivity maps have been developed at different AMSR-E frequencies. Obtained product has been validated and compared to global land use distribution. Moreover, global soil moisture AMSR-E product maps have been also used to assess to the spatial distribution of the emissivity. Moreover, obtained emissivity maps seem to be consistent with landuse/land cover maps. They also agree well with land emissivity maps obtained from the ISCCP database and developed using SSM/I observations (for frequencies over 19 GHz).

Forward-Looking Infrared Cameras for Micrometeorological Applications within Vineyards

PubMed Central

Katurji, Marwan; Zawar-Reza, Peyman

2016-01-01

We apply the principles of atmospheric surface layer dynamics within a vineyard canopy to demonstrate the use of forward-looking infrared cameras measuring surface brightness temperature (spectrum bandwidth of 7.5 to 14 μm) at a relatively high temporal rate of 10 s. The temporal surface brightness signal over a few hours of the stable nighttime boundary layer, intermittently interrupted by periods of turbulent heat flux surges, was shown to be related to the observed meteorological measurements by an in situ eddy-covariance system, and reflected the above-canopy wind variability. The infrared raster images were collected and the resultant self-organized spatial cluster provided the meteorological context when compared to in situ data. The spatial brightness temperature pattern was explained in terms of the presence or absence of nighttime cloud cover and down-welling of long-wave radiation and the canopy turbulent heat flux. Time sequential thermography as demonstrated in this research provides positive evidence behind the application of thermal infrared cameras in the domain of micrometeorology, and to enhance our spatial understanding of turbulent eddy interactions with the surface. PMID:27649208

An enhanced VIIRS aerosol optical thickness (AOT) retrieval algorithm over land using a global surface reflectance ratio database

NASA Astrophysics Data System (ADS)

Zhang, Hai; Kondragunta, Shobha; Laszlo, Istvan; Liu, Hongqing; Remer, Lorraine A.; Huang, Jingfeng; Superczynski, Stephen; Ciren, Pubu

2016-09-01

The Visible/Infrared Imager Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (S-NPP) satellite has been retrieving aerosol optical thickness (AOT), operationally and globally, over ocean and land since shortly after S-NPP launch in 2011. However, the current operational VIIRS AOT retrieval algorithm over land has two limitations in its assumptions for land surfaces: (1) it only retrieves AOT over the dark surfaces and (2) it assumes that the global surface reflectance ratios between VIIRS bands are constants. In this work, we develop a surface reflectance ratio database over land with a spatial resolution 0.1° × 0.1° using 2 years of VIIRS top of atmosphere reflectances. We enhance the current operational VIIRS AOT retrieval algorithm by applying the surface reflectance ratio database in the algorithm. The enhanced algorithm is able to retrieve AOT over both dark and bright surfaces. Over bright surfaces, the VIIRS AOT retrievals from the enhanced algorithm have a correlation of 0.79, mean bias of -0.008, and standard deviation (STD) of error of 0.139 when compared against the ground-based observations at the global AERONET (Aerosol Robotic Network) sites. Over dark surfaces, the VIIRS AOT retrievals using the surface reflectance ratio database improve the root-mean-square error from 0.150 to 0.123. The use of the surface reflectance ratio database also increases the data coverage of more than 20% over dark surfaces. The AOT retrievals over bright surfaces are comparable to MODIS Deep Blue AOT retrievals.

Numerical reproduction and explanation of road surface mirages under grazing-angle scattering.

PubMed

Lu, Jia; Zhou, Huaichun

2017-07-01

The mirror-like reflection image of the road surface under grazing-angle scattering can be easily observed in daily life. It was suggested that road surface mirages may occur due to a light-enhancing effect of the rough surface under grazing-angle scattering. The main purpose of this work is to explain the light-enhancing mechanism of rough surfaces under grazing-angle scattering. The off-specular reflection from a random rough magnesium oxide ceramic surface is analyzed by using the geometric optics approximation method. Then, the geometric optics approximation method is employed to develop a theoretical model to predict the observation effect of the grazing-angle scattering phenomenon of the road surface. The rough surface is assumed to consist of small-scale rough surface facets. The road surface mirage is reproduced from a large number of small-scale rough surface facets within the eye's resolution limit at grazing scattering angles, as the average bidirectional reflectance distribution function value at the bright location is about twice that of the surface in front of the mirage. It is suggested that the light-enhancing effect of the rough surface under grazing-angle scattering is not proper to be termed as "off-specular reflection," since it has nothing to do with the "specular" direction with respect to the incident direction.

Near-Surface Geologic Units Exposed Along Ares Vallis and in Adjacent Areas: A Potential Source of Sediment at the Mars Pathfinder Landing Site

NASA Technical Reports Server (NTRS)

Treiman, Allan H.

1997-01-01

A sequence of layers, bright and dark, is exposed on the walls of canyons, impact craters and mesas throughout the Ares Vallis region, Chryse Planitia, and Xanthe Terra, Mars. Four layers can be seen: two pairs of alternating dark and bright albedo. The upper dark layer forms the top surface of many walls and mesas. The upper dark-bright pair was stripped as a unit from many streamlined mesas and from the walls of Ares Valles, leaving a bench at the top of the lower dark layer, approximately 250 m below the highland surface on streamlined islands and on the walls of Ares Vallis itself. Along Ares Vallis, the scarp between the highlands surface and this bench is commonly angular in plan view (not smoothly curving), suggesting that erosion of the upper dark-bright pair of layers controlled by planes of weakness, like fractures or joints. These near-surface layers in the Ares Vallis area have similar thicknesses, colors, and resistances to erosion to layers exposed near the tops of walls in Valles Marineris (Treiman et al.) and may represent the same pedogenic hardpan units. From this correlation, and from analogies with hardpans on Earth, the light-color layers may be cemented by calcite or gypsum. The dark layers are likely cemented by an iron-bearing mineral. Mars Pathfinder instruments should permit recognition and useful analyses of hardpan fragments, provided that clean uncoated surfaces are accessible. Even in hardpan-cemented materials, it should be possible to determine the broad types of lithologies in the Martian highlands. However, detailed geochemical modeling of highland rocks and soils may be compromised by the presence of hardpan cement minerals.

A Bright Lunar Impact Flash Linked to the Virginid Meteor Complex

NASA Technical Reports Server (NTRS)

Moser, D. E.; Suggs, R. M.; Suggs, R. J.

2015-01-01

On 17 March 2013 at 03:50:54 UTC, NASA detected a bright impact flash on the Moon caused by a meteoroid impacting the lunar surface. There was meteor activity in Earth's atmosphere the same night from the Virginid Meteor Complex. The impact crater associated with the impact flash was found and imaged by Lunar Reconnaissance Orbiter (LRO). Goal: Monitor the Moon for impact flashes produced by meteoroids striking the lunar surface. Determine meteoroid flux in the 10's gram to kilogram size range.

ARC-1979-AC79-7090

NASA Image and Video Library

1979-07-10

P-21762 C This color picture of Ganymede in the region 30° S 180° W shows features as small as 6 kilometers (3.7 miles) across. Shown is a bright halo impact crater that shows the fresh material thrown out of the crater. In the background is bright grooved terrain that may be the result of shearing of the surface materials along fault planes. The dark background material is the ancient heavily cratered terrain--the oldest material preserved on the Ganymede surface.

Simple Forest Canopy Thermal Exitance Model

NASA Technical Reports Server (NTRS)

Smith J. A.; Goltz, S. M.

1999-01-01

We describe a model to calculate brightness temperature and surface energy balance for a forest canopy system. The model is an extension of an earlier vegetation only model by inclusion of a simple soil layer. The root mean square error in brightness temperature for a dense forest canopy was 2.5 C. Surface energy balance predictions were also in good agreement. The corresponding root mean square errors for net radiation, latent, and sensible heat were 38.9, 30.7, and 41.4 W/sq m respectively.

Colours of the Outer Solar System Origins Survey: An Update

NASA Astrophysics Data System (ADS)

Schwamb, Megan E.; Fraser, Wesley C.; Pike, Rosemary E.; Bannister, Michele T.; Marsset, Michaël; Kavelaars, J. J.; Benecchi, Susan; Delsanti, Audrey C.; Lehner, Matthew J.; Wang, Shiang-Yu; Thirouin, Audrey; Nesvorný, David

2018-01-01

The vast majority of the known dwarf-planet sized bodies are bright enough to be studied through optical and infrared spectroscopy. As a result, we have an understanding of the surface properties for the largest Kuiper belt objects (KBOs) which retain their primordial inventory of volatile ices. For the typically smaller > 22 mag KBO, we must rely instead on what colors reveal by proxy; yet this picture remains incomplete. Most KBO physical property studies examine the hodgepodge set of objects discovered by various surveys with different and varying detection biases that make it difficult if not impossible to reliably estimate the sizes of the different surface color groupings (compositional classes) residing in the modern-day Kuiper belt.The Colours of the Outer Solar System Origins Survey (Col-OSSOS) probes the surface properties within the Kuiper belt primarily through near simultaneous g,r and J colors with the Gemini North Telescope and u-band with Canada-France-Hawaii Telescope. The project aims to target ~100 KBOs brighter than 23.6 r‧ mag found by the Outer Solar System Origins Survey (OSSOS), a survey with a well-measured detection efficiency. Thus, Col-OSSOS provides the first brightness-complete, compositional-dynamical map of the Outer Solar System, probing in a new light the radial color distribution in the primordial planetesimal disk from which KBOs originated. We will provide an update on the current status of the program highlighting results from the first two years of the survey; including size estimates of the two color KBO subgroups (the red and neutral surfaces) within the dynamically excited Kuiper belt and implications for the early planetesimal disk composition based on neutral-colored binaries found in the cold classical Kuiper belt.

High Energy Studies of Astrophysical Dust

NASA Astrophysics Data System (ADS)

Corrales, Lia Racquel

Astrophysical dust---any condensed matter ranging from tens of atoms to micron sized grains---accounts for about one third of the heavy elements produced in stars and disseminated into space. These tiny pollutants are responsible for producing the mottled appearance in the spray of light we call the "Milky Way." However these seemingly inert particles play a strong role in the physics of the interstellar medium, aiding star and planet formation, and perhaps helping to guide galaxy evolution. Most dust grains are transparent to X-ray light, leaving a signature of atomic absorption, but also scattering the light over small angles. Bright X-ray objects serendipitously situated behind large columns of dust and gas provide a unique opportunity to study the dust along the line of sight. I focus primarily on X-ray scattering through dust, which produces a diffuse halo image around a central point source. Such objects have been observed around X-ray bright Galactic binaries and extragalactic objects that happen to shine through the plane of the Milky Way. I use the Chandra X-ray Observatory, a space-based laboratory operated by NASA, which has imaging resolution ideal for studying X-ray scattering halos. I examine several bright X-ray objects with dust-free sight lines to test their viability as templates and develop a parametric model for the Chandra HETG point spread function (PSF). The PSF describes the instrument's imaging response to a point source, an understanding of which is necessary for properly measuring the surface brightness of X-ray scattering halos. I use an HETG observation of Cygnus X-3, one of the brightest objects available in the Chandra archive, to derive a dust grain size distribution. There exist degenerate solutions for the dust scattering halo, but with the aid of Bayesian analytics I am able to apply prior knowledge about the Cyg X-3 sight line to measure the relative abundance of dust in intervening Milky Way spiral arms. I also demonstrate how information from a single scattering halo can be used in conjunction with X-ray spectroscopy to directly measure the dust-to-gas mass ratio, laying the groundwork for future scattering halo surveys. Distant quasars also produce X-rays that pierce the intergalactic medium. These sources invite the unique opportunity to search for extragalactic dust, whether distributed diffusely throughout intergalactic space, surrounding other galaxies, or occupying reservoirs of cool intergalactic gas. I review X-ray scattering in a cosmological context, examining the range and sensitivity of Chandra to detect the low surface brightness levels of intergalactic scattering. Of particular interest is large "grey" dust, which would cause systematic errors in precision cosmology experiments at a level comparable to the size of the error bars sought. This requires using the more exact Mie scattering treatment, which reduces the scattering cross-section for soft X-rays by a factor of about ten, compared to the Rayleigh-Gans approximation used for interstellar X-ray scattering studies. This allows me to relax the limit on intergalactic dust imposed by previous X-ray imaging of a z=4.3 quasar, QSO 1508+5714, which overestimated the scattering intensity. After implementing the Mie solution with the cosmological integral for scattering halo intensity, I found that intergalactic dust will scatter 1-3% of soft X-ray light. Unfortunately the wings of the Chandra PSF are brighter than the surface brightness expected for these intergalactic scattering halos. The X-ray signatures of intergalactic dust may only be visible if a distant quasar suddenly dimmed by a factor of 1000 or more, leaving behind an X-ray scattering echo, or "ghost" halo.

Hot spots on Io: Initial results from Galileo's near infrared mapping spectrometer

USGS Publications Warehouse

Lopes-Gautier, R.; Davies, A.G.; Carlson, R.; Smythe, W.; Kamp, L.; Soderblom, L.; Leader, F.E.; Mehlman, R.

1997-01-01

The Near-Infrared Mapping Spectrometer on Galileo has monitored the volcanic activity on Io since June 28, 1996. This paper presents preliminary analysis of NIMS thermal data for the first four orbits of the Galileo mission. NIMS has detected 18 new hot spots and 12 others which were previously known to be active. The distribution of the hot spots on Io's surface may not be random, as hot spots surround the two bright, SO2-rich regions of Bosphorus Regio and Colchis Regio. Most hot spots seem to be persistently active from orbit to orbit and 10 of those detected were active in 1979 during the Voyager encounters. We report the distribution of hot spot temperatures and find that they are consistent with silicate volcanism. Copyright 1997 by the American Geophysical Union.

Bidirectional reflectance distribution function of Spectralon white reflectance standard illuminated by incoherent unpolarized and plane-polarized light.

PubMed

Bhandari, Anak; Hamre, Børge; Frette, Øvynd; Zhao, Lu; Stamnes, Jakob J; Kildemo, Morten

2011-06-01

A Lambert surface would appear equally bright from all observation directions regardless of the illumination direction. However, the reflection from a randomly scattering object generally has directional variation, which can be described in terms of the bidirectional reflectance distribution function (BRDF). We measured the BRDF of a Spectralon white reflectance standard for incoherent illumination at 405 and 680 nm with unpolarized and plane-polarized light from different directions of incidence. Our measurements show deviations of the BRDF for the Spectralon white reflectance standard from that of a Lambertian reflector that depend both on the angle of incidence and the polarization states of the incident light and detected light. The non-Lambertian reflection characteristics were found to increase more toward the direction of specular reflection as the angle of incidence gets larger.

A simplified Suomi NPP VIIRS dust detection algorithm

NASA Astrophysics Data System (ADS)

Yang, Yikun; Sun, Lin; Zhu, Jinshan; Wei, Jing; Su, Qinghua; Sun, Wenxiao; Liu, Fangwei; Shu, Meiyan

2017-11-01

Due to the complex characteristics of dust and sparse ground-based monitoring stations, dust monitoring is facing severe challenges, especially in dust storm-prone areas. Aim at constructing a high-precision dust storm detection model, a pixel database, consisted of dusts over a variety of typical feature types such as cloud, vegetation, Gobi and ice/snow, was constructed, and their distributions of reflectance and Brightness Temperatures (BT) were analysed, based on which, a new Simplified Dust Detection Algorithm (SDDA) for the Suomi National Polar-Orbiting Partnership Visible infrared Imaging Radiometer (NPP VIIRS) is proposed. NPP VIIRS images covering the northern China and Mongolian regions, where features serious dust storms, were selected to perform the dust detection experiments. The monitoring results were compared with the true colour composite images, and results showed that most of the dust areas can be accurately detected, except for fragmented thin dusts over bright surfaces. The dust ground-based measurements obtained from the Meteorological Information Comprehensive Analysis and Process System (MICAPS) and the Ozone Monitoring Instrument Aerosol Index (OMI AI) products were selected for comparison purposes. Results showed that the dust monitoring results agreed well in the spatial distribution with OMI AI dust products and the MICAPS ground-measured data with an average high accuracy of 83.10%. The SDDA is relatively robust and can realize automatic monitoring for dust storms.

Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Carruthers, G. R.; Page, T.

1977-01-01

Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.

Assimilation of SMOS Brightness Temperatures or Soil Moisture Retrievals into a Land Surface Model

NASA Technical Reports Server (NTRS)

De Lannoy, Gabrielle J. M.; Reichle, Rolf H.

2016-01-01

Three different data products from the Soil Moisture Ocean Salinity (SMOS) mission are assimilated separately into the Goddard Earth Observing System Model, version 5 (GEOS-5) to improve estimates of surface and root-zone soil moisture. The first product consists of multi-angle, dual-polarization brightness temperature (Tb) observations at the bottom of the atmosphere extracted from Level 1 data. The second product is a derived SMOS Tb product that mimics the data at a 40 degree incidence angle from the Soil Moisture Active Passive (SMAP) mission. The third product is the operational SMOS Level 2 surface soil moisture (SM) retrieval product. The assimilation system uses a spatially distributed ensemble Kalman filter (EnKF) with seasonally varying climatological bias mitigation for Tb assimilation, whereas a time-invariant cumulative density function matching is used for SM retrieval assimilation. All assimilation experiments improve the soil moisture estimates compared to model-only simulations in terms of unbiased root-mean-square differences and anomaly correlations during the period from 1 July 2010 to 1 May 2015 and for 187 sites across the US. Especially in areas where the satellite data are most sensitive to surface soil moisture, large skill improvements (e.g., an increase in the anomaly correlation by 0.1) are found in the surface soil moisture. The domain-average surface and root-zone skill metrics are similar among the various assimilation experiments, but large differences in skill are found locally. The observation-minus-forecast residuals and analysis increments reveal large differences in how the observations add value in the Tb and SM retrieval assimilation systems. The distinct patterns of these diagnostics in the two systems reflect observation and model errors patterns that are not well captured in the assigned EnKF error parameters. Consequently, a localized optimization of the EnKF error parameters is needed to further improve Tb or SM retrieval assimilation.

Control of dispersed-phase temperature in plasma flows by the spectral-brightness pyrometry method

NASA Astrophysics Data System (ADS)

Dolmatov, A. V.; Gulyaev, I. P.; Gulyaev, P. Yu; Iordan, V. I.

2016-02-01

In the present work, we propose a new method for measuring the distribution of temperature in the ensembles of condensed-phase particles in plasma spray flows. Interrelation between the spectral temperature of the particles and the distribution of camera brightness signal is revealed. The established inter-relation enables an in-situ calibration of measuring instruments using the objects under study. The spectral-brightness pyrometry method was approbated on a Plazer plasma-arc wire spraying facility at the Paton Institute of Electrical Welding (Ukrainian Academy of Sciences, Kiev) and on the Thermoplasma 50-1 powder spraying facility at the Institute of Theoretical and Applied Mechanics (Russian Academy of Sciences, Siberian Branch, Novosibirsk). The work was supported by the Russian Foundation for Basic Research (Grants Nos. 14-08-90428 and 15-48-00100).

Aircraft microwave observations and simulations of deep convection from 18 to 183 GHz. II - Model results

NASA Technical Reports Server (NTRS)

Yeh, Hwa-Young M.; Prasad, N.; Mack, Robert A.; Adler, Robert F.

1990-01-01

In this June 29, 1986 case study, a radiative transfer model is used to simulate the aircraft multichannel microwave brightness temperatures presented in the Adler et al. (1990) paper and to study the convective storm structure. Ground-based radar data are used to derive hydrometeor profiles of the storm, based on which the microwave upwelling brightness temperatures are calculated. Various vertical hydrometeor phase profiles and the Marshall and Palmer (M-P, 1948) and Sekhon and Srivastava (S-S, 1970) ice particle size distributions are experimented in the model. The results are compared with the aircraft radiometric data. The comparison reveals that the M-P distribution well represents the ice particle size distribution, especially in the upper tropospheric portion of the cloud; the S-S distribution appears to better simulate the ice particle size at the lower portion of the cloud, which has a greater effect on the low-frequency microwave upwelling brightness temperatures; and that, in deep convective regions, significant supercooled liquid water (about 0.5 g/cu m) may be present up to the -30 C layer, while in less convective areas, frozen hydrometeors are predominant above -10 C level.

Relationship of magnetic field strength and brightness of fine-structure elements in the solar temperature minimum region

NASA Technical Reports Server (NTRS)

Cook, J. W.; Ewing, J. A.

1990-01-01

A quantitative relationship was determined between magnetic field strength (or magnetic flux) from photospheric magnetograph observations and the brightness temperature of solar fine-structure elements observed at 1600 A, where the predominant flux source is continuum emission from the solar temperature minimum region. A Kitt Peak magnetogram and spectroheliograph observations at 1600 A taken during a sounding rocket flight of the High Resolution Telescope and Spectrograph from December 11, 1987 were used. The statistical distributions of brightness temperature in the quiet sun at 1600 A, and absolute value of magnetic field strength in the same area were determined from these observations. Using a technique which obtains the best-fit relationship of a given functional form between these two histogram distributions, a quantitative relationship was determined between absolute value of magnetic field strength B and brightness temperature which is essentially linear from 10 to 150 G. An interpretation is suggested, in which a basal heating occurs generally, while brighter elements are produced in magnetic regions with temperature enhancements proportional to B.

The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer

NASA Astrophysics Data System (ADS)

Lacour, S.; Meimon, S.; Thiébaut, E.; Perrin, G.; Verhoelst, T.; Pedretti, E.; Schuller, P. A.; Mugnier, L.; Monnier, J.; Berger, J. P.; Haubois, X.; Poncelet, A.; Le Besnerais, G.; Eriksson, K.; Millan-Gabet, R.; Ragland, S.; Lacasse, M.; Traub, W.

2008-07-01

Aims: We undertook an H band interferometric examination of Arcturus, a star frequently used as a spatial and spectral calibrator. Methods: Using the IOTA 3 telescope interferometer, we performed spectro-interferometric observations (R≈35) of Arcturus. Atmospheric models and prescriptions were fitted to the data to derive the brightness distribution of the photosphere. Image reconstruction was performed using two software algorithms: Wisard and Mira. Results: An achromatic power law proved to be a good model of the brightness distribution, with a limb darkening compatible with the one derived from atmospheric model simulations using our marcs model. A Rosseland diameter of 21.05±0.21 was derived, corresponding to an effective temperature of Teff = 4295±26 K. No companion was detected from the closure phases, with an upper limit on the brightness ratio of 8×10-4 at 1 AU. The dynamic range at such distance from the photosphere was established as 1.5×10-4 (1σ rms). An upper limit of 1.7×10-3 was also derived for the level of brightness asymmetries present in the photosphere.

Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer

NASA Astrophysics Data System (ADS)

Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

2006-08-01

A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO2, HCHO, SO2, H2O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg.

Information content of sky intensity and polarization measurements at right angles to the solar direction

NASA Technical Reports Server (NTRS)

Holland, A. C.; Thomas, R. W. L.; Pearce, W. A.

1978-01-01

The paper presents the results of a Monte Carlo simulation study of the brightness and polarization at right angles to the solar direction both for ground-based observations (looking up) and for satellite-based systems (looking down). Calculations have been made for a solar zenith angle whose cosine was 0.6 and wavelengths ranging from 3500 A to 9500 A. A sensitivity of signatures to total aerosol loading, aerosol particle size distribution and refractive index, and the surface reflectance albedo has been demonstrated. For Lambertian-type surface reflection the albedo effects enter solely through the intensity sensitivity, and very high correlations have been found between the polarization term signatures for the ground-based and satellite-based systems. Potential applications of these results for local albedo predictions and satellite imaging systems recalibrations are discussed.

Colloidal motion under the action of a thermophoretic force.

PubMed

Burelbach, Jerome; Zupkauskas, Mykolas; Lamboll, Robin; Lan, Yang; Eiser, Erika

2017-09-07

We present thermophoretic measurements in aqueous suspensions of three different polystyrene (PS) particles of varying negative charge, size, and surface coating. Our measurement technique is based on the observation of the colloidal steady-state distribution using conventional bright-field microscopy, which avoids undesirable effects such as laser-induced convection or local heating. We find that the colloids with the weakest zeta potential exhibit the strongest thermophoretic effect, suggesting that the Soret coefficient has a more intricate dependence on surface functionality than predicted by existing theoretical approaches. We also study the relaxation of the colloids to steady-state and propose a model to quantify the relaxation speed, based on the time evolution of the colloidal center of mass. Our observations are well described by this model and show that the relaxation speed tends to increase with the magnitude of the thermophoretic force.

Colloidal motion under the action of a thermophoretic force

NASA Astrophysics Data System (ADS)

Burelbach, Jerome; Zupkauskas, Mykolas; Lamboll, Robin; Lan, Yang; Eiser, Erika

2017-09-01

We present thermophoretic measurements in aqueous suspensions of three different polystyrene (PS) particles of varying negative charge, size, and surface coating. Our measurement technique is based on the observation of the colloidal steady-state distribution using conventional bright-field microscopy, which avoids undesirable effects such as laser-induced convection or local heating. We find that the colloids with the weakest zeta potential exhibit the strongest thermophoretic effect, suggesting that the Soret coefficient has a more intricate dependence on surface functionality than predicted by existing theoretical approaches. We also study the relaxation of the colloids to steady-state and propose a model to quantify the relaxation speed, based on the time evolution of the colloidal center of mass. Our observations are well described by this model and show that the relaxation speed tends to increase with the magnitude of the thermophoretic force.

TES mapping of Mars' north seasonal cap

USGS Publications Warehouse

Kieffer, H.H.; Titus, T.N.

2001-01-01

The Mars Global Surveyor thermal emission spectrometer has made observations of Mars' north polar region for nearly a full martian year. Measurements of bolometric emission and reflectance, as well as brightness temperatures in specific bands synthesized from thermal radiance spectra, are used to track the behavior of surface and atmospheric temperatures, the distribution of condensed CO2 and H2O, and the occurrence of dust storms. CO2 grain size in the polar night is variable in space and time, and is influenced by atmospheric conditions. Some specific locations display concentration of H2O frost and indicate the presence of long-term water-ice near the surface. Annual budgets of solid CO2 range up to 1500 kg m-2; preliminary analysis suggests significant transport of energy into latitudes near 70?? N during the polar night. ?? 2001 Elsevier Science.

A ROSAT HRI observation of the cooling flow cluster MS0839.9+2938.

NASA Astrophysics Data System (ADS)

Nesci, R.; Perola, G. C.; Wolter, A.

1995-07-01

A ROSAT HRI observation of the cluster MS0839.9+2938 at z=0.194 is presented. It confirms the earlier suggestion, based on the detection of extended Hα emission, that the inner regions of this cluster are dominated by a cooling flow. Within the cooling radius a marginally significant evidence is found of structures in the surface brightness, which are similar to those more significantly found in two less distant cooling flow clusters (A2029 and 2A0335+096). We note that, although its barycentre falls on top of the central giant elliptical galaxy, the azimuthally averaged brightness distribution does not peak at that position and actually stays flat out to about 40kpc (10") from the galaxy centre. From comparison with the two clusters mentioned above, this situation seems peculiar, and it is suggested that it could arise from photoelectric absorption by cold gas within the cooling flow, with an equivalent column density in the order of 5x10^21^/cm^2^ within ~10" from the centre, a factor 2-3 higher than the column spectroscopically detected in the comparison clusters.

The association of chromospheric and coronal phenomena with the evolution of the quiet sun magnetic fields

NASA Technical Reports Server (NTRS)

Harvey, Karen L.; Tang, Frances; Gaizauskas, Victor

1986-01-01

Using daily full-disk magnetograms and He I 10830 spectroheliograms to study the count and surface distribution of ephemeral regions over the solar cycle, Harvey (1985) concluded that the small dark structures seen in 10830, thought to correspond to X-ray bright points, were more often associated with magnetic bipoles that appeared to result from an encounter of already existing opposite polarity magentic flux than with emerging small magnetic bipoles (ephemeral regions). Such encounters would be more likely to occur in areas of mixed polarity. The fractional area of the sun covered by mixed polarity fields varies anti-correlated with the solar cycle leading to a possible explanation for the 180 degrees out of phase solar cycle variation of X-ray bright points. To establish the validity of this suggestion, a detailed study of time-sequence magnetic field, He I wavelength 10830, Ha, C IV, and Si II observations of selected areas of the quiet sun was initiated about 2 years ago. The preliminary results of this study are reported.

Potential of fish scales as a filling material in surface coating of cellulosic paper.

PubMed

Ural, Elif; Kandirmaz, Emine A

2018-01-01

Paper is one of the important inputs for the printing industry, and the most important leading parameter in the printing process is its brightness. Brightness can be brought to paper using coatings and sizing. Desired surface properties and, most importantly, surface roughness can be achieved by changing the contents of the coating and sizing of the materials it contains. The use of biomaterials is becoming more important in the paper industry, as they represent substances with a lower carbon footprint. Fish scales are already used as a filling material, cosmetic material and fish food, as well as for determining the age of fish. Fish scales were brought to different sizes by a milling process. Paper formulations including different amounts of fish scales were prepared with fish scales, and coatings on raw paper were subjected to test printings in IGT-C1, with formulations and physical characteristics of coatings such as brightness, lightfastness, strength, adhesion etc. being determined. Regarding the value of yellowness, mixtures of 2.5%-10% can be used. The maximum value of brightness was obtained from a mixture of 10%. Aging visibly changed the colors. The coatings obtained were brighter than the initial coating compositions. The top quality formulation was the coating with 5% medium-sized fish scale particles.

Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres

NASA Astrophysics Data System (ADS)

de Sanctis, M. C.; Raponi, A.; Ammannito, E.; Ciarniello, M.; Toplis, M. J.; McSween, H. Y.; Castillo-Rogez, J. C.; Ehlmann, B. L.; Carrozzo, F. G.; Marchi, S.; Tosi, F.; Zambon, F.; Capaccioni, F.; Capria, M. T.; Fonte, S.; Formisano, M.; Frigeri, A.; Giardino, M.; Longobardo, A.; Magni, G.; Palomba, E.; McFadden, L. A.; Pieters, C. M.; Jaumann, R.; Schenk, P.; Mugnuolo, R.; Raymond, C. A.; Russell, C. T.

2016-08-01

The typically dark surface of the dwarf planet Ceres is punctuated by areas of much higher albedo, most prominently in the Occator crater. These small bright areas have been tentatively interpreted as containing a large amount of hydrated magnesium sulfate, in contrast to the average surface, which is a mixture of low-albedo materials and magnesium phyllosilicates, ammoniated phyllosilicates and carbonates. Here we report high spatial and spectral resolution near-infrared observations of the bright areas in the Occator crater on Ceres. Spectra of these bright areas are consistent with a large amount of sodium carbonate, constituting the most concentrated known extraterrestrial occurrence of carbonate on kilometre-wide scales in the Solar System. The carbonates are mixed with a dark component and small amounts of phyllosilicates, as well as ammonium carbonate or ammonium chloride. Some of these compounds have also been detected in the plume of Saturn’s sixth-largest moon Enceladus. The compounds are endogenous and we propose that they are the solid residue of crystallization of brines and entrained altered solids that reached the surface from below. The heat source may have been transient (triggered by impact heating). Alternatively, internal temperatures may be above the eutectic temperature of subsurface brines, in which case fluids may exist at depth on Ceres today.

An interpretation of photometric parameters of bright desert regions of Mars and their dependence on wave length

NASA Technical Reports Server (NTRS)

Weaver, W. R.; Meador, W. E.

1977-01-01

Photometric data from the bright desert areas of Mars were used to determine the dependence of the three photometric parameters of the photometric function on wavelength and to provide qualitative predictions about the physical properties of the surface. Knowledge of the parameters allowed the brightness of these areas of Mars to be determined for any scattering geometry in the wavelength range of 0.45 to 0.70 micron. The changes that occur in the photometric parameters due to changes in wavelength were shown to be consistent with their physical interpretations, and the predictions of surface properties were shown to be consistent with conditions expected to exist in these regions of Mars. The photometric function was shown to have potential as a diagnostic tool for the qualitative determination of surface properties, and the consistency of the behavior of the photometric parameters was considered to be support for the validity of the photometric function.

Unveiling the Low Surface Brightness Stellar Peripheries of Galaxies

NASA Astrophysics Data System (ADS)

Ferguson, Annette M. N.

2018-01-01

The low surface brightness peripheral regions of galaxies contain a gold mine of information about how minor mergers and accretions have influenced their evolution over cosmic time. Enormous stellar envelopes and copious amounts of faint tidal debris are natural outcomes of the hierarchical assembly process and the search for and study of these features, albeit highly challenging, offers the potential for unrivalled insight into the mechanisms of galaxy growth. Over the last two decades, there has been burgeoning interest in probing galaxy outskirts using resolved stellar populations. Wide-field surveys have uncovered vast tidal debris features and new populations of very remote globular clusters, while deep Hubble Space Telescope photometry has provided exquisite star formation histories back to the earliest epochs. I will highlight some recent results from studies within and beyond the Local Group and conclude by briefly discussing the great potential of future facilities, such as JWST, Euclid, LSST and WFIRST, for major breakthroughs in low surface brightness galaxy periphery science.

The MESSIER surveyor: unveiling the ultra-low surface brightness universe

NASA Astrophysics Data System (ADS)

Valls-Gabaud, David; MESSIER Collaboration

2017-03-01

The MESSIER surveyor is a small mission designed at exploring the very low surface brightness universe. The satellite will drift-scan the entire sky in 6 filters covering the 200-1000 nm range, reaching unprecedented surface brightness levels of 34 and 37 mag arcsec-2 in the optical and UV, respectively. These levels are required to achieve the two main science goals of the mission: to critically test the ΛCDM paradigm of structure formation through (1) the detection and characterisation of ultra-faint dwarf galaxies, which are predicted to be extremely abundant around normal galaxies, but which remain elusive; and (2) tracing the cosmic web, which feeds dark matter and baryons into galactic haloes, and which may contain the reservoir of missing baryons at low redshifts. A large number of science cases, ranging from stellar mass loss episodes to intracluster light through fluctuations in the cosmological UV-optical background radiation are free by-products of the full-sky maps produced.

Local ISM 3D Distribution and Soft X-ray Background Inferences for Nearby Hot Gas

NASA Technical Reports Server (NTRS)

Puspitarini, L.; Lallement, R.; Snowden, Steven L.; Vergely, J.-L.; Snowden, S.

2014-01-01

Three-dimensional (3D) interstellar medium (ISM) maps can be used to locate not only interstellar (IS) clouds, but also IS bubbles between the clouds that are blown by stellar winds and supernovae, and are filled by hot gas. To demonstrate this, and to derive a clearer picture of the local ISM, we compare our recent 3D IS dust distribution maps to the ROSAT diffuse Xray background maps after removal of heliospheric emission. In the Galactic plane, there is a good correspondence between the locations and extents of the mapped nearby cavities and the soft (0.25 keV) background emission distribution, showing that most of these nearby cavities contribute to this soft X-ray emission. Assuming a constant dust to gas ratio and homogeneous 106 K hot gas filling the cavities, we modeled in a simple way the 0.25 keV surface brightness along the Galactic plane as seen from the Sun, taking into account the absorption by the mapped clouds. The data-model comparison favors the existence of hot gas in the solar neighborhood, the so-called Local Bubble (LB). The inferred mean pressure in the local cavities is found to be approx.9,400/cu cm K, in agreement with previous studies, providing a validation test for the method. On the other hand, the model overestimates the emission from the huge cavities located in the third quadrant. Using CaII absorption data, we show that the dust to CaII ratio is very small in those regions, implying the presence of a large quantity of lower temperature (non-X-ray emitting) ionized gas and as a consequence a reduction of the volume filled by hot gas, explaining at least part of the discrepancy. In the meridian plane, the two main brightness enhancements coincide well with the LB's most elongated parts and chimneys connecting the LB to the halo, but no particular nearby cavity is found towards the enhancement in the direction of the bright North Polar Spur (NPS) at high latitude. We searched in the 3D maps for the source regions of the higher energy (0.75 keV) enhancements in the fourth and first quadrants. Tunnels and cavities are found to coincide with the main bright areas, however no tunnel nor cavity is found to match the low-latitude b > or approx. 8deg, brightest part of the NPS. In addition, the comparison between the 3D maps and published spectral data favors a NPS central source region location beyond 230 pc, i.e. at larger distance than usually considered. Those examples illustrate the potential use of more detailed 3D distributions of the nearby ISM for the interpretation of the diffuse soft X-ray background.

Optical and Near-Infrared Structural Properties of Cluster Galaxies at z ~ 0.3

NASA Astrophysics Data System (ADS)

La Barbera, F.; Busarello, G.; Merluzzi, P.; Massarotti, M.; Capaccioli, M.

2002-06-01

Structural parameters (half-light radius re, mean effective surface brightness <μ>e, and Sersic index n, parameterizing the light profile shape) are derived for a sample of galaxies in the rich cluster AC 118 at z=0.31, so far the largest (N=93) sample of galaxies at intermediate redshift with structural parameters measured in the near-infrared. The parameters are obtained in two optical wavebands (V and R) and in the K band, corresponding approximately to the B, V, and H rest frame. The distributions of re at z=0.31 match those for the Coma Cluster (i.e., for the local universe) both in the optical and in the NIR. The K-band distribution is of particular interest, since the NIR light mimics the mass distribution of galaxies. The similarity of the distributions for the two clusters (AC 118 and Coma) proves that the galaxies at the bright end of the luminosity function did not significantly change their sizes since z~0.3 to the present epoch. The ratio of the optical to the NIR half-light radius shows a marked trend with the shape of the light profile (Sersic index n). In galaxies with n>~4 (typical bright ellipticals) re,NIR~0.6re,opt, while the average ratio is 0.8 for galaxies with lower n (typical disk systems). Moreover, the NIR Sersic index is systematically larger than in the optical for n<~4. These results, translated into optical and optical-NIR color gradients, imply that the optical color gradients at z~0.3 are similar to those of nearby galaxies. The optical-NIR color gradients are in the average larger, ranging from -0.73 mag dex-1 for n<~4 to -0.35 mag dex-1 for n>~4. Models with ``pure age'' or ``pure metallicity'' gradients are unable to reconcile our color gradients estimates with observations at z~0, but we argue that the combined effects of age and metallicity might explain consistently the observed data: passive evolution (plus the possible effect of dust absorption) may account for the differences between the optical and NIR structural properties. The lack of any major change in re,NIR since z~0.3 suggests that merging involving bright galaxies did not play a significant role in the last ~4.4 Gyr (ΩM=0.3, ΩΛ=0, H0=50 km s-1 Mpc-1). The results of the present paper will be applied to the study of the scaling laws in subsequent works. Based on observations collected at European Southern Observatory (ESO 62.O-0369, 63.O-0257, 64.O-0236) and on data from the STScI Science Archive.

DISENTANGLING THE ICL WITH THE CHEFs: ABELL 2744 AS A CASE STUDY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiménez-Teja, Y.; Dupke, R., E-mail: yojite@iaa.es

Measurements of the intracluster light (ICL) are still prone to methodological ambiguities, and there are multiple techniques in the literature to address them, mostly based on the binding energy, the local density distribution, or the surface brightness. A common issue with these methods is the a priori assumption of a number of hypotheses on either the ICL morphology, its surface brightness level, or some properties of the brightest cluster galaxy (BCG). The discrepancy in the results is high, and numerical simulations just place a boundary on the ICL fraction in present-day galaxy clusters in the range 10%–50%. We developed amore » new algorithm based on the Chebyshev–Fourier functions to estimate the ICL fraction without relying on any a priori assumption about the physical or geometrical characteristics of the ICL. We are able to not only disentangle the ICL from the galactic luminosity but mark out the limits of the BCG from the ICL in a natural way. We test our technique with the recently released data of the cluster Abell 2744, observed by the Frontier Fields program. The complexity of this multiple merging cluster system and the formidable depth of these images make it a challenging test case to prove the efficiency of our algorithm. We found a final ICL fraction of 19.17 ± 2.87%, which is very consistent with numerical simulations.« less

Resolving Io's Volcanoes from a Mutual Event Observation at the Large Binocular Telescope

NASA Astrophysics Data System (ADS)

de Kleer, K.; Skrutskie, M.; Leisenring, J.; Davies, A. G.; Resnick, A.; Conrad, A.; De Pater, I.; Hinz, P.; Defrere, D.; Veillet, C.

2016-12-01

Near-infrared observations of Io during occultation by Jupiter and the other Galilean satellites have been central to ground-based studies of Io's volcanism for decades. When such observations are made using adaptive optics on 8-10m telescopes, the infrared emission from individual features can be resolved at a resolution approaching a few km on Io's surface. On March 8, 2015, the Large Binocular Telescope Interferometer (LBTI) observed Io during a Europa mutual occultation event. Images were obtained at a wavelength of 4.8 microns every 123 milliseconds, corresponding to 2 km on Io's surface. The thermal emission from four hot spots including Loki Patera, Pillan Patera, and Kurdalagon Patera is clearly resolved. The latter two hot spots hosted bright eruptions in early 2015; the thermal emission from these sites likely represents the aftermath of those eruptions. The occultation light curves are used to construct a brightness temperature map for each of the four hot spots, from which the lava age is estimated using a model for cooling basaltic lavas. The thermal mapping of Loki Patera has produced the first-ever temperature map of the entire patera floor at high (10 km) spatial resolution, and the corresponding age distribution yields the resurfacing rate. For each hot spot, the age and spatial extent of the lava is interpreted in the context of its activity during the surrounding months.

A Broadband Microwave Radiometer Technique at X-band for Rain and Drop Size Distribution Estimation

NASA Technical Reports Server (NTRS)

Meneghini, R.

2005-01-01

Radiometric brightess temperatures below about 12 GHz provide accurate estimates of path attenuation through precipitation and cloud water. Multiple brightness temperature measurements at X-band frequencies can be used to estimate rainfall rate and parameters of the drop size distribution once correction for cloud water attenuation is made. Employing a stratiform storm model, calculations of the brightness temperatures at 9.5, 10 and 12 GHz are used to simulate estimates of path-averaged median mass diameter, number concentration and rainfall rate. The results indicate that reasonably accurate estimates of rainfall rate and information on the drop size distribution can be derived over ocean under low to moderate wind speed conditions.

Beyond 31 mag arcsec-2: The Frontier of Low Surface Brightness Imaging with the Largest Optical Telescopes

NASA Astrophysics Data System (ADS)

Trujillo, Ignacio; Fliri, Jüergen

2016-06-01

The detection of structures in the sky with optical surface brightnesses fainter than 30 mag arcsec-2 (3σ in 10 × 10 arcsec boxes; r-band) has remained elusive in current photometric deep surveys. Here we show how present-day telescopes of 10 m class can provide broadband imaging 1.5-2 mag deeper than most previous results within a reasonable amount of time (I.e., <10 hr on-source integration). In particular, we illustrate the ability of the 10.4 m Gran Telescopio de Canarias telescope to produce imaging with a limiting surface brightness of 31.5 mag arcsec-2 (3σ in 10 × 10 arcsec boxes; r-band) using 8.1 hr on source. We apply this power to explore the stellar halo of the galaxy UGC 00180, a galaxy analogous to M31 located at ˜150 Mpc, by obtaining a radial profile of surface brightness down to μ r ˜ 33 mag arcsec-2. This depth is similar to that obtained using the star-counts techniques for Local Group galaxies, but is achieved at a distance where this technique is unfeasible. We find that the mass of the stellar halo of this galaxy is ˜4 × 109 M ⊙, I.e., (3 ± 1)% of the total stellar mass of the whole system. This amount of mass in the stellar halo is in agreement with current theoretical expectations for galaxies of this kind.

Bright Ray Craters in Ganymede's Northern Hemisphere

NASA Technical Reports Server (NTRS)

1979-01-01

GANYMEDE COLOR PHOTOS: This color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The images show detail on the surface with a resolution of four and a half km. This picture is of a region in the northern hemisphere near the terminator. It shows a variety of impact structures, including both razed and unrazed craters, and the odd, groove-like structures discovered by Voyager in the lighter regions. The most striking features are the bright ray craters which have a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young craters have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas suggests that here, too, there is cleaner ice. We see ray craters with all sizes of ray patterns, ranging from extensive systems of the crater in the southern part of this picture, which has rays at least 300-500 kilometers long, down to craters which have only faint remnants of bright ejects patterns (such as several of the craters in the southern half of PIA01516; P21262). This variation suggests that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact. JPL manages and controls the Voyager project for NASA's Office of Space Science.

Dark Galaxies and Lost Baryons (IAU S244)

NASA Astrophysics Data System (ADS)

Davies, Jonathan I.; Disney, Michael J.

2008-05-01

Preface; Conference prelims; The HI that barked in the night M. J. Disney; The detection of dark galaxies in blind HI surveys J. I. Davies; Red haloes of galaxies - reservoirs of baryonic dark matter? E. Zackrisson, N. Bergvall, C. Flynn, G. Ostlin, G. Micheva and B. Baldwell; Constraints on dark and visible mass in galaxies from strong gravitational lensing S. Dye and S. Warren; Lost baryons at low redshift S. Mathur, F. Nicastro and R. Williams; Observed properties of dark matter on small spatial scales R. Wyse and G. Gilmore; The mass distribution in spiral galaxies P. Salucci; Connecting lost baryons and dark galaxies via QSO absorption lines T. Tripp; ALFALFA: HI cosmology in the local universe R. Giovanelli; The ALFALFA search for (almost) dark galaxies across the HI mass function M. Haynes; HI clouds detected towards Virgo with the Arecibo Legacy Fast ALFA Survey B. Kent; Cosmic variance in the HI mass function S. Schneider; The Arecibo Galaxy Environments Survey - potential for finding dark galaxies and results so far R. Minchin et al.; Free-floating HI clouds in the M81 group E. Brinks, F. Walter and E. Skillman; Where are the stars in dark galaxies J. Rosenberg, J. Salzer and J. Cannon; The halo by halo missing baryon problem S. McGaugh; The local void is really empty R. Tully; Voids in the local volume: a limit on appearance of a galaxy in a dark matter halo A. Tikhonov and A. Klypin; Dim baryons in the cosmic web C. Impey; A census of baryons in galaxy clusters and groups A. Gonzalez, D. Zaritsky and A. Zabludo; Statistical properties of the intercluster light from SDSS image stacking S. Zibetti; QSO strong gravitational lensing and the detection of dark halos A. Maccio; Strong gravitational lensing: bright galaxies and lost dark-matter L. Koopmans; Mapping the distribution of luminous and dark matter in strong lensing galaxies I. Ferreras, P. Saha, L. Williams and S. Burles; Tidal debris posing as dark galaxies P. Duc, F. Bournaud and E. Brinks; Numerical simulation of the dwarf companions of giant galaxies A. Nelson and P. Williams; Delayed galaxies C. Struck, M. Hancock, B. Smith, P. Appleton, V. Charmandaris and M. Giroux; Probe of dark galaxies via disturbed/lopsided isolated galaxies I. Karachentsev, V. Karachentseva, W. Huchtmeier, D. Makarov and S. Kaisin; Star formation thresholds J. Schaye; Scaling relations of dwarf galaxies without supernova-driven winds K. Tassis, A. Kravtsov and N. Gnedin; Star formation in massive low surface brightness galaxies K. O'Neil; Linking clustering properties and the evolution of low surface brightness galaxies D. Bomans and S. Rosenbaum; Too small to form a galaxy: how the UV background determines the baryon fraction M. Hoeft, G. Yepes and S. Gottlober; Star formation in damped Lyman selected galaxies L. Christensen; Dark-matter content of early-type galaxies with planetary nebulae N. Napolitano et al.; Hunting for ghosts: low surface brightnesses from pixels R. Scaramella and S. Sabatini; Baryonic properties of the darkest galaxies E. Grebel; The dwarf low surface brightness population in different environments of the local universe S. Sabatini, J. Davies, S. Roberts and R. Scaramella; Mass modelling of dwarf spheroidal galaxies J. Klimentowski et al.; Evolution of dwarf galaxies in the Centaurus A Group L. Makarova and D. Makarov; A flat faint end of the Fornax cluster galaxy luminosity function S. Mieske, M. Hilker, L. Infante and C. Mendes de Oliveira; Can massive dark halos destroy the discs of dwarf galaxies? B. Fuchs and O. Esquivel; 'Dark galaxies' and local very metal-poor gas-rich galaxies: possible interrelations S. Pustilnik; Morphology and environment of dwarf galaxies in the local universe H. Ann; Arecibo survey of HI emission from disk galaxies at redshift z 0.2 B. Catinella, M. Haynes, J. Gardner, A. Connolly and R. Giovanelli; AGES observations of

Detection of moisture and moisture related phenomena from Skylab. [correlation of brightness and antenna temperature with soil moisture for Texas and Kansas test sites

NASA Technical Reports Server (NTRS)

Eagleman, J. R.; Pogge, E. C.; Moore, R. K. (Principal Investigator); Hardy, N.; Lin, W.; League, L.

1974-01-01

The author has identified the following significant results. Skylab 2 data for June 5, 1973 (Texas site) relates favorably with previously calculated aircraft data when correlating brightness temperature to soil moisture. However, more detailed work is needed to determine the corrected surface temperature. In addition, correlations between the S194 antenna temperature and soil moisture have been obtained for five sets of Skylab data. The best correlations were obtained for the surface to one inch depth in four cases and for surface to two inches depth for the fifth case. Correlation coefficients for the surface to one inch depth were -0.98, -0.95, -0.90, -0.82, and -0.80.

Source structure errors in radio-interferometric clock synchronization for ten measured distributions

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1981-01-01

The effects of source structure on radio interferometry measurements were investigated. The brightness distribution measurements for ten extragalactic sources were analyzed. Significant results are reported.

Photometric Lambert Correction for Global Mosaicking of HRSC Data

NASA Astrophysics Data System (ADS)

Walter, Sebastian; Michael, Greg; van Gasselt, Stephan; Kneissl, Thomas

2015-04-01

The High Resolution Stereo Camera (HRSC) is a push-broom image sensor onboard Mars Express recording the Martian surface in 3D and color. Being in orbit since 2004, the camera has obtained over 3,600 panchromatic image sequences covering about 70% of the planet's surface at 10-20 m/pixel. The composition of an homogenous global mosaic is a major challenge due to the strong elliptical and highly irregular orbit of the spacecraft, which often results in large variations of illumination and atmospheric conditions between individual images. For the purpose of a global mosaic in the full Nadir resolution of 12.5 m per pixel we present a first-order systematic photometric correction for the individual image sequences based on a Lambertian reflection model. During the radiometric calibration of the HRSC data, values for the reflectance scaling factor and the reflectance offset are added to the individual image labels. These parameters can be used for a linear transformation from the original DN values into spectral reflectance values. The spectral reflectance varies with the solar incidence angle, topography (changing the local incidence angle and therefore adding an exta geometry factor for each ground pixel), the bi-directional reflectance distribution function (BRDF) of the surface, and atmospheric effects. Mosaicking the spectral values together as images sometimes shows large brightness differences. One major contributor to the brightness differences between two images is the differing solar geometry due to the varying time of day when the individual images were obtained. This variation causes two images of the same or adjacent areas to have different image brightnesses. As a first-order correction for the varying illumination conditions and resulting brightness variations, the images are corrected for the solar incidence angle by assuming an ideal diffusely reflecting behaviour of the surface. This correction requires the calculation of the solar geometry for each image pixel by an image-to-ground function. For the calculations we are using the VICAR framework and the SPICE library. Under the Lambertian assumption, the reflectance diminishment resulting from an inclined Sun angle can be corrected by dividing the measured reflectance by the cosine of the illumination angle. After rectification of the corrected images, the individual images are mosaicked together. The overall visual impression shows a much better integration of the individual image sequences. The correction resolves the direct correlation between the reflectance and the incidence angles from the data. It does not account for topographic, atmospheric or BRDF influences to the measurements. Since the main purpose of the global HRSC image mosaic is the application for geomorphologic studies with a good visual impression of the albedo variations and the topography, the remaining distortions at the image seams can be equalized by non-reversible image matching techniques.

A model for the infrared emission from an OB star cluster environment

NASA Technical Reports Server (NTRS)

Leisawitz, D.

1991-01-01

A model for the infrared emission from the neighborhood of an OB star cluster is described. The distribution of gas and dust around the stars, properties of the dust, and the cluster and interstellar radiation fields are variable. The model can be applied to regions around clusters embedded to various degrees in their parental molecular clouds (i.e., compact H II regions, blister-type H II regions, and the tenuous H II regions ionized by naked O stars). The model is used to simulate IRAS observations of a typical blister H II region. Infrared surface brightness and spectral energy distributions are predicted and the impact of limited spatial resolution is illustrated. The model results are shown to be consistent with observations of the exemplary outer Galaxy OB cluster NGC 7380. It is planned to use the model as a diagnostic tool to probe the physical conditions and dust properties in star-formation regions and, ultimately, in an interpretation of the spectral energy distributions of spiral galaxies.

Edge Modeling by Two Blur Parameters in Varying Contrasts.

PubMed

Seo, Suyoung

2018-06-01

This paper presents a method of modeling edge profiles with two blur parameters, and estimating and predicting those edge parameters with varying brightness combinations and camera-to-object distances (COD). First, the validity of the edge model is proven mathematically. Then, it is proven experimentally with edges from a set of images captured for specifically designed target sheets and with edges from natural images. Estimation of the two blur parameters for each observed edge profile is performed with a brute-force method to find parameters that produce global minimum errors. Then, using the estimated blur parameters, actual blur parameters of edges with arbitrary brightness combinations are predicted using a surface interpolation method (i.e., kriging). The predicted surfaces show that the two blur parameters of the proposed edge model depend on both dark-side edge brightness and light-side edge brightness following a certain global trend. This is similar across varying CODs. The proposed edge model is compared with a one-blur parameter edge model using experiments of the root mean squared error for fitting the edge models to each observed edge profile. The comparison results suggest that the proposed edge model has superiority over the one-blur parameter edge model in most cases where edges have varying brightness combinations.

Brightness checkerboard lattice method for the calibration of the coaxial reverse Hartmann test

NASA Astrophysics Data System (ADS)

Li, Xinji; Hui, Mei; Li, Ning; Hu, Shinan; Liu, Ming; Kong, Lingqin; Dong, Liquan; Zhao, Yuejin

2018-01-01

The coaxial reverse Hartmann test (RHT) is widely used in the measurement of large aspheric surfaces as an auxiliary method for interference measurement, because of its large dynamic range, highly flexible test with low frequency of surface errors, and low cost. And the accuracy of the coaxial RHT depends on the calibration. However, the calibration process remains inefficient, and the signal-to-noise ratio limits the accuracy of the calibration. In this paper, brightness checkerboard lattices were used to replace the traditional dot matrix. The brightness checkerboard method can reduce the number of dot matrix projections in the calibration process, thus improving efficiency. An LCD screen displayed a brightness checkerboard lattice, in which the brighter checkerboard and the darker checkerboard alternately arranged. Based on the image on the detector, the relationship between the rays at certain angles and the photosensitive positions of the detector coordinates can be obtained. And a differential de-noising method can effectively reduce the impact of noise on the measurement results. Simulation and experimentation proved the feasibility of the method. Theoretical analysis and experimental results show that the efficiency of the brightness checkerboard lattices is about four times that of the traditional dot matrix, and the signal-to-noise ratio of the calibration is significantly improved.

Spatiotemporal analysis of brightness induction

PubMed Central

McCourt, Mark E.

2011-01-01

Brightness induction refers to a class of visual illusions in which the perceived intensity of a region of space is influenced by the luminance of surrounding regions. These illusions are significant because they provide insight into the neural organization of the visual system. A novel quadrature-phase motion cancelation technique was developed to measure the magnitude of the grating induction brightness illusion across a wide range of spatial frequencies, temporal frequencies and test field heights. Canceling contrast is greatest at low frequencies and declines with increasing frequency in both dimensions, and with increasing test field height. Canceling contrast scales as the product of inducing grating spatial frequency and test field height (the number of inducing grating cycles per test field height). When plotted using a spatial axis which indexes this product, the spatiotemporal induction surfaces for four test field heights can be described as four partially overlapping sections of a single larger surface. These properties of brightness induction are explained in the context of multiscale spatial filtering. The present study is the first to measure the magnitude of grating induction as a function of temporal frequency. Taken in conjunction with several other studies (Blakeslee & McCourt, 2008; Robinson & de Sa, 2008; Magnussen & Glad, 1975) the results of this study illustrate that at least one form of brightness induction is very much faster than that reported by DeValois et al. (1986) and Rossi and Paradiso (1996), and are inconsistent with the proposition that brightness induction results from a slow “filling in” process. PMID:21763339

A bright-rimmed cloud sculpted by the H ii region Sh2-48

NASA Astrophysics Data System (ADS)

Ortega, M. E.; Paron, S.; Giacani, E.; Rubio, M.; Dubner, G.

2013-08-01

Aims: We characterize a bright-rimmed cloud embedded in the H ii region Sh2-48 while searching for evidence of triggered star formation. Methods: We carried out observations towards a region of 2' × 2' centered at RA = 18h22m11.39s, Dec = -14°35'24.81''(J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J = 3-2, 13CO J = 3-2, HCO+J = 4-3, and CS J = 7-6 lines with an angular resolution of about 22''. We also present radio continuum observations at 5 GHz carried out with the Jansky Very Large Array (JVLA; EEUU) interferometer with a synthetized beam of 7'' × 5''. The molecular transitions were used to study the distribution and kinematics of the molecular gas of the bright-rimmed cloud. The radio continuum data was used to characterize the ionized gas located on the illuminated border of this molecular condensation. Combining these observations with infrared public data allowed us to build up a comprehensive picture of the current state of star formation within this cloud. Results: The analysis of our molecular observations reveals a relatively dense clump with n(H2) ~ 3 × 103cm-3, located in projection onto the interior of the H ii region Sh2-48. The emission distribution of the four observed molecular transitions has, at VLSR ~ 38 km s-1, morphological anticorrelation with the bright-rimmed cloud as seen in the optical emission. From the new radio continuum observations, we identify a thin layer of ionized gas located on the border of the clump that is facing the ionizing star. The ionized gas has an electron density of about 73 cm-3, which is a factor three higher than the typical critical density (nc ~ 25 cm-3), above which an ionized boundary layer can be formed and maintained. This supports the hypothesis that the clump is being photoionized by the nearby O9.5V star, BD-14 5014. From the evaluation of the pressure balance between the ionized and molecular gas, we conclude that the clump would be in a prepressure balance state with the shocks being driven into the surface layer. Among the five YSO candidates found in the region, two of them (class I) are placed slightly beyond the bright rim, suggesting that their formation could have been triggered by the radiation-driven implosion process.

Interferometric observations of M42 at 1. 3 cm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohashi, N.; Mizuno, A.; Tatematsu, K.

1989-02-01

New interferometric observations of the central 4.5 deg of M42 have been made at 1.3 cm with the NRO Millimeter-Wave Array. Distribution of the radio source consists of two known components. One is centered on the Trapezium stars, and the other corresponds to the bright bar. The present map is compared with the distribution of the CS molecular gas (Hayashi et al., 1989), and it is found that the boundary of the ionized gas is well delineated by the CS ridge. This indicates that the ionized gas is distributed in a cavity of the molecular gas, as suggested by Sugitanimore » et al. (1986). A comparison of the map with a 6-cm radio-continuum map (Johnston et al., 1983) indicates that the 6 cm distribution is more extended than the 1.3 cm distribution, except in the southern part of the bright bar. 9 references.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jester, Sebastian; Schneider, Donald P.; Richards, Gordon T.

The author investigates the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing with imaging and spectroscopy from the Sloan Digital Sky Survey. A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, they define the PG's parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows thatmore » the effective U-B cut in the PG survey is U-B < -0.71, implying a color-related incompleteness. As the color distribution of bright quasars peaks near U-B = -0.7 and the 2-{sigma} error in U-B is comparable to the full width of the color distribution of quasars, the color incompleteness of the BQS is approximately 50% and essentially random with respect to U-B color for z < 0.5. There is however, a bias against bright quasars at 0.5 < z < 1, which is induced by the color-redshift relation of quasars (although quasars at z > 0.5 are inherently rare in bright surveys in any case). They find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects which are blue in g-i, in particular compared to the full range of g-i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.« less

The RSA survey of dwarf galaxies, 1: Optical photometry

NASA Technical Reports Server (NTRS)

Vader, J. Patricia; Chaboyer, Brian

1994-01-01

We present detailed surface photometry, based on broad B-band charge coupled device (CCD) images, of about 80 dwarf galaxies. Our sample represents approximately 10% of all dwarf galaxies identified in the vicinity of Revised Shapley-Ames (RSA) galaxies on high resolution blue photographic plates, referred to as the RSA survey of dwarf galaxies. We derive global properties and radial surface brightness profiles, and examine the morphologies. The radial surface brightness profiles of dwarf galaxies, whether early or late type, display the same varieties in shape and complexity as those of classical giant galaxies. Only a few are well described by a pure r(exp 1/4) law. Exponential profiles prevail. Features typical of giant disk galaxies, such as exponential profiles with a central depression, lenses, and even, in one case (IC 2041), a relatively prominent bulge are also found in dwarf galaxies. Our data suggest that the central region evolves from being bulge-like, with an r(exp 1/4) law profile, in bright galaxies to a lens-like structure in dwarf galaxies. We prove detailed surface photometry to be a helpful if not always sufficient tool in investigating the structure of dwarf galaxies. In many cases kinematic information is needed to complete the picture. We find the shapes of the surface brightness profiles to be loosely associated with morphological type. Our sample contains several new galaxies with properties intermediate between those of giant and dwarf ellipticals (but no M32-like objects). This shows that such intermediate galaxies exist so that at least a fraction of early-type dwarf ellipticals is structurally related to early-type giants instead of belonging to a totally unrelated, disjunct family. This supports an origin of early-type dwarf galaxies as originally more massive systems that acquired their current morphology as a result of substantial, presumable supernova-driven, mass loss. On the other hand, several early-type dwarfs in our sample are merger candidates. Merger events may lead to anisotropic velocity distributions in systems of any luminosity, including dwarfs. The RSA sample of dwarf galaxies is more likely to contain mergers because, in contrast to earlier dwarf galaxy surveys that have focused on clusters and rich groups of galaxies, the RSA dwarfs are typically located in low density environments. The occurrence of mergers among dwarf galaxies is of interest in connection with the rapid evolution of faint blue galaxy counts at redshift z less than 1 which suggests that dwarf galaxies were about five times more numerous in the recent past. Finally, our sample contains several examples of late-type dwarfs and 'transition' types that are potential precursors of nucleated early-type dwarfs. All the above processes--mass loss, mergers, astration--are likely to have contributed to the formation of the current population of diffuse early-type dwarfs. A few new redshifts of dwarf galaxies are reported in this paper.

Anticorrelation of X-ray bright points with sunspot number, 1970-1978

NASA Technical Reports Server (NTRS)

Golub, L.; Davis, J. M.; Krieger, A. S.

1979-01-01

Soft X-ray observations of the solar corona over the period 1970-1978 show that the number of small short-lived bipolar magnetic features (X-ray bright points) varies inversely with the sunspot index. During the entire period from 1973 to 1978 most of the magnetic flux emerging at the solar surface appeared in the form of bright points. In 1970, near the peak of solar cycle 20, the contributions from bright points and from active regions appear to be approximately equal. These observations strongly support an earlier suggestion that the solar cycle may be characterized as an oscillator in wave-number space with relatively little variation in the average total rate of flux emergence.

Study on hexagonal super-lattice pattern with surface discharges in dielectric barrier discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying; Dong, Lifang, E-mail: donglfhbu@163.com; Niu, Xuejiao

2015-10-15

The hexagonal super-lattice pattern with surface discharges (SDs) in dielectric barrier discharge is investigated by intensified charge-coupled device. The pattern is composed of the bright spot and the dim spot which is located at the centroid of surrounding other three bright spots. The phase diagram of the pattern as a function of the gas pressure and the argon concentration is given. The instantaneous images indicate that the bright spot emerging at the front of the current pulse is formed by the volume discharge (VD), and dim spot occurring at the tail of the current pulse is formed by the SD.more » The above result shows that the SD is induced by the VD. The simulation of the electric fields of wall charges accumulated by VDs confirms that the dim spot is formed by the confluences of the SDs of surrounding other three bright spots. By using optical emission spectrum method, both the molecule vibration temperature and electron density of the SD are larger than that of the VD.« less

Energy, entropy and mass scaling relations for elliptical galaxies. Towards a physical understanding of their photometric properties

NASA Astrophysics Data System (ADS)

Márquez, I.; Lima Neto, G. B.; Capelato, H.; Durret, F.; Lanzoni, B.; Gerbal, D.

2001-12-01

In the present paper, we show that elliptical galaxies (Es) obey a scaling relation between potential energy and mass. Since they are relaxed systems in a post violent-relaxation stage, they are quasi-equilibrium gravitational systems and therefore they also have a quasi-constant specific entropy. Assuming that light traces mass, these two laws imply that in the space defined by the three Sérsic law parameters (intensity Sigma0 , scale a and shape nu ), elliptical galaxies are distributed on two intersecting 2-manifolds: the Entropic Surface and the Energy-Mass Surface. Using a sample of 132 galaxies belonging to three nearby clusters, we have verified that ellipticals indeed follow these laws. This also implies that they are distributed along the intersection line (the Energy-Entropy line), thus they constitute a one-parameter family. These two physical laws (separately or combined), allow to find the theoretical origin of several observed photometrical relations, such as the correlation between absolute magnitude and effective surface brightness, and the fact that ellipticals are located on a surface in the [log Reff, -2.5 log Sigma0, log nu ] space. The fact that elliptical galaxies are a one-parameter family has important implications for cosmology and galaxy formation and evolution models. Moreover, the Energy-Entropy line could be used as a distance indicator.

Bright Feature Appears in Titan Kraken Mare

NASA Image and Video Library

2014-11-10

Two Synthetic Aperture Radar (SAR) images from the radar experiment on NASA's Cassini spacecraft show that, between May 2013 and August 2014, a bright feature appeared in Kraken Mare, the largest hydrocarbon sea on Saturn's moon Titan. Researchers think the bright feature is likely representative of something on the hydrocarbon sea's surface, such as waves or floating debris. A similar feature appeared in Ligea Mare, another Titan sea, and was seen to evolve in appearance between 2013 and 2014 (see PIA18430). The image at left was taken on May 23, 2013 at an incidence angle of 56 degrees; the image at right was taken on August 21, 2014 at an incidence angle of 5 degrees. Incidence angle refers to the angle at which the radar beam strikes the surface. http://photojournal.jpl.nasa.gov/catalog/PIA19047

Lunar and Venusian radar bright rings

NASA Technical Reports Server (NTRS)

Thompson, T. W.; Saunders, R. S.; Weissman, D. E.

1986-01-01

Twenty-one lunar craters have radar bright ring appearances which are analogous to eleven complete ring features in the earth-based 12.5 cm observations of Venus. Radar ring diameters and widths for the lunar and Venusian features overlap for sizes from 45 to 100 km. Radar bright areas for the lunar craters are associated with the slopes of the inner and outer rim walls, while level crater floors and level ejecta fields beyond the raised portion of the rim have average radar backscatter. It is proposed that the radar bright areas of the Venusian rings are also associated with the slopes on the rims of craters. The lunar craters have evolved to radar bright rings via mass wasting of crater rim walls and via post-impact flooding of crater floors. Aeolian deposits of fine-grained material on Venusian crater floors may produce radar scattering effects similar to lunar crater floor flooding. These Venusian aeolian deposits may preferentially cover blocky crater floors producing a radar bright ring appearance. It is proposed that the Venusian features with complete bright ring appearances and sizes less than 100 km are impact craters. They have the same sizes as lunar craters and could have evolved to radar bright rings via analogous surface processes.

Variance based joint sparsity reconstruction of synthetic aperture radar data for speckle reduction

NASA Astrophysics Data System (ADS)

Scarnati, Theresa; Gelb, Anne

2018-04-01

In observing multiple synthetic aperture radar (SAR) images of the same scene, it is apparent that the brightness distributions of the images are not smooth, but rather composed of complicated granular patterns of bright and dark spots. Further, these brightness distributions vary from image to image. This salt and pepper like feature of SAR images, called speckle, reduces the contrast in the images and negatively affects texture based image analysis. This investigation uses the variance based joint sparsity reconstruction method for forming SAR images from the multiple SAR images. In addition to reducing speckle, the method has the advantage of being non-parametric, and can therefore be used in a variety of autonomous applications. Numerical examples include reconstructions of both simulated phase history data that result in speckled images as well as the images from the MSTAR T-72 database.

Detection of radio emission from optically identified supernova remnants in M31

NASA Technical Reports Server (NTRS)

Dickel, J. R.; Dodorico, S.; Felli, M.; Dopita, M.

1982-01-01

The Very Large Array was used to conduct a radio search at a wavelength of 20 cm for ten optically identified supernova remnants (SNRs) in M31. Five SNRs were detected, and for the other objects, upper limits to the emission were determined. On the average, the surface brightness of an SNR in M31 appears to be fainter than that of an SNR in the Galaxy. It is suggested that the median surface brightness at a given diameter is higher in late-type spirals than in Sb systems.

Propiedades peculiares de los sistemas de cúmulos globulares y su relación con la formación de sus galaxias anfitrionas

NASA Astrophysics Data System (ADS)

Bassino, L. P.

2017-10-01

Globular clusters (GCs) are ancient stellar systems, among the oldest ones in the Universe. As a consequence, they carry information related to the formation and evolution of their host-galaxies. The study of GC systems associated with early-type galaxies has shown that most of them have similar characteristics. Among them, the most noticeable is the existence of two GC subpopulations (metal-poor and metal-rich, respectively), that differ clearly in their colour distribution, spatial distribution, and kinematics. However, GC systems whose properties differ from the known ``classic'' ones, have been detected in the last years. For instance, the case of GC systems that present more than two subpopulations in their colour distribution or anomalies in the luminosity function. The peculiar properties of the GC systems, together with characteristics of the host-galaxy like the presence of type Ia SNe, the surface-brightness distribution, or the colour map, may be related to bursts of star formation and let us rebuild the host-galaxy history.

Automatic detection method for mura defects on display film surface using modified Weber's law

NASA Astrophysics Data System (ADS)

Kim, Myung-Muk; Lee, Seung-Ho

2014-07-01

We propose a method that automatically detects mura defects on display film surfaces using a modified version of Weber's law. The proposed method detects mura defects regardless of their properties and shapes by identifying regions perceived by human vision as mura using the brightness of pixel and image distribution ratio of mura in an image histogram. The proposed detection method comprises five stages. In the first stage, the display film surface image is acquired and a gray-level shift performed. In the second and third stages, the image histogram is acquired and analyzed, respectively. In the fourth stage, the mura range is acquired. This is followed by postprocessing in the fifth stage. Evaluations of the proposed method conducted using 200 display film mura image samples indicate a maximum detection rate of ˜95.5%. Further, the results of application of the Semu index for luminance mura in flat panel display (FPD) image quality inspection indicate that the proposed method is more reliable than a popular conventional method.

Thermal blinding of gated detectors in quantum cryptography.

PubMed

Lydersen, Lars; Wiechers, Carlos; Wittmann, Christoffer; Elser, Dominique; Skaar, Johannes; Makarov, Vadim

2010-12-20

It has previously been shown that the gated detectors of two commercially available quantum key distribution (QKD) systems are blindable and controllable by an eavesdropper using continuous-wave illumination and short bright trigger pulses, manipulating voltages in the circuit [Nat. Photonics 4, 686 (2010)]. This allows for an attack eavesdropping the full raw and secret key without increasing the quantum bit error rate (QBER). Here we show how thermal effects in detectors under bright illumination can lead to the same outcome. We demonstrate that the detectors in a commercial QKD system Clavis2 can be blinded by heating the avalanche photo diodes (APDs) using bright illumination, so-called thermal blinding. Further, the detectors can be triggered using short bright pulses once they are blind. For systems with pauses between packet transmission such as the plug-and-play systems, thermal inertia enables Eve to apply the bright blinding illumination before eavesdropping, making her more difficult to catch.

The prediction of tropopause height from clusters of brightness temperatures and its application in the stratified regression temperature retrievals using microwave and infrared satellite measurements

NASA Technical Reports Server (NTRS)

Munteanu, M. J.; Piraino, P.; Jakubowicz, O.

1984-01-01

A total of 1575 radiosondes and the corresponding simulated brightness temperatures were used in an effort to derive a temperature retrieval based on the clusters of brightness temperatures. The 8 simulated channels, namely, 3 MSU and 5 IR of the TIROS-N satellite are used by the GLAS temperature retrieval method. The 3 MSU and 5 IR brightness temperatures were clustered into 17 cluster groups and a regression for the prediction of the tropopause height in mb was generated. The overall r.m.s. for the tropopause prediction is excellent, namely, around 16 mb for the summer and 23 mb for the winter. The correct cluster of brightness temperatures can be identified 98% of the time by the method of discriminatory classification if it is approximately a normal distribution or, in general, by the method of the nearest neighbor.

Ganymede's Equatorial Region

NASA Technical Reports Server (NTRS)

1979-01-01

GANYMEDE COLOR PHOTOS: This color picture as acquired by Voyager 1 during its approach to Ganymede on Monday afternoon (the 5th of March). At ranges between about 230 to 250 thousand km. The images show detail on the surface with a resolution of four and a half km. This picture is south of PIA01516 (P21262) near the equator of Ganymede, and has relatively subdued colors in the visible part of the spectrum (later, scientists will analyze Voyager pictures taken in UV). The most striking features are the bright ray craters which have a distinctly 'bluer' color appearing white against the redder background. Ganymede's surface is known to contain large amounts of surface ice and it appears that these relatively young craters have spread bright fresh ice materials over the surface. Likewise, the lighter color and reflectivity of the grooved areas suggest that here, too, there is cleaner ice. We see ray craters with all sizes of ray patterns, ranging from extensive systems, down to craters which have only faint remnants of bright ejecta patterns. This variation suggests that, as on the Moon, there are processes which act to darken ray material, probably 'gardening' by micrometeoroid impact. JPL manages and controls the Voyager project for NASA's Office of Space Science.

Low-Latitude Ethane Rain on Titan

NASA Technical Reports Server (NTRS)

Dalba, Paul A.; Buratti, Bonnie J.; Brown, R. H.; Barnes, J. W.; Baines, K. H.; Sotin, C.; Clark, R. N.; Lawrence, K. J.; Nicholson, P. D.

2012-01-01

Cassini ISS observed multiple widespread changes in surface brightness in Titan's equatorial regions over the past three years. These brightness variations are attributed to rainfall from cloud systems that appear to form seasonally. Determining the composition of this rainfall is an important step in understanding the "methanological" cycle on Titan. I use data from Cassini VIMS to complete a spectroscopic investigation of multiple rain-wetted areas. I compute "before-and-after" spectral ratios of any areas that show either deposition or evaporation of rain. By comparing these spectral ratios to a model of liquid ethane, I find that the rain is most likely composed of liquid ethane. The spectrum of liquid ethane contains multiple absorption features that fall within the 2-micron and 5-micron spectral windows in Titan's atmosphere. I show that these features are visible in the spectra taken of Titan's surface and that they are characteristically different than those in the spectrum of liquid methane. Furthermore, just as ISS saw the surface brightness reverting to its original state after a period of time, I show that VIMS observations of later flybys show the surface composition in different stages of returning to its initial form.

Ultrashort high-brightness pulses from storage rings

NASA Astrophysics Data System (ADS)

Khan, Shaukat

2017-09-01

The brightness of short-wavelength radiation from accelerator-based sources can be increased by coherent emission in which the radiation intensity scales with the number of contributing electrons squared. This requires a microbunched longitudinal electron distribution, which is the case in free-electron lasers. The brightness of light sources based on electron storage rings was steadily improved, but could profit further from coherent emission. The modulation of the electron energy by a continuous-wave laser field may provide steady-state microbunching in the infrared regime. For shorter wavelengths, the energy modulation can be converted into a temporary density modulation by a dispersive chicane. One particular goal is coherent emission from a very short "slice" within an electron bunch in order to produce ultrashort radiation pulses with high brightness.

Laser inscription of pseudorandom structures for microphotonic diffuser applications.

PubMed

Alqurashi, Tawfiq; Alhosani, Abdulla; Dauleh, Mahmoud; Yetisen, Ali K; Butt, Haider

2018-04-19

Optical diffusers provide a solution for a variety of applications requiring a Gaussian intensity distribution including imaging systems, biomedical optics, and aerospace. Advances in laser ablation processes have allowed the rapid production of efficient optical diffusers. Here, we demonstrate a novel technique to fabricate high-quality glass optical diffusers with cost-efficiency using a continuous CO2 laser. Surface relief pseudorandom microstructures were patterned on both sides of the glass substrates. A numerical simulation of the temperature distribution showed that the CO2 laser drills a 137 μm hole in the glass for every 2 ms of processing time. FFT simulation was utilized to design predictable optical diffusers. The pseudorandom microstructures were characterized by optical microscopy, Raman spectroscopy, and angle-resolved spectroscopy to assess their chemical properties, optical scattering, transmittance, and polarization response. Increasing laser exposure and the number of diffusing surfaces enhanced the diffusion and homogenized the incident light. The recorded speckle pattern showed high contrast with sharp bright spot free diffusion in the far field view range (250 mm). A model of glass surface peeling was also developed to prevent its occurrence during the fabrication process. The demonstrated method provides an economical approach in fabricating optical glass diffusers in a controlled and predictable manner. The produced optical diffusers have application in fibre optics, LED systems, and spotlights.

Measurement of Circumstellar Disk Sizes in the Upper Scorpius OB Association with ALMA

NASA Astrophysics Data System (ADS)

Barenfeld, Scott A.; Carpenter, John M.; Sargent, Anneila I.; Isella, Andrea; Ricci, Luca

2017-12-01

We present detailed modeling of the spatial distributions of gas and dust in 57 circumstellar disks in the Upper Scorpius OB Association observed with ALMA at submillimeter wavelengths. We fit power-law models to the dust surface density and CO J = 3–2 surface brightness to measure the radial extent of dust and gas in these disks. We found that these disks are extremely compact: the 25 highest signal-to-noise disks have a median dust outer radius of 21 au, assuming an {R}-1 dust surface density profile. Our lack of CO detections in the majority of our sample is consistent with these small disk sizes assuming the dust and CO share the same spatial distribution. Of seven disks in our sample with well-constrained dust and CO radii, four appear to be more extended in CO, although this may simply be due to the higher optical depth of the CO. Comparison of the Upper Sco results with recent analyses of disks in Taurus, Ophiuchus, and Lupus suggests that the dust disks in Upper Sco may be approximately three times smaller in size than their younger counterparts, although we caution that a more uniform analysis of the data across all regions is needed. We discuss the implications of these results for disk evolution.

THE ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: IMPLICATIONS FOR SPECTRAL LINE INTENSITY MAPPING AT MILLIMETER WAVELENGTHS AND CMB SPECTRAL DISTORTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carilli, C. L.; Walter, F.; Chluba, J.

We present direct estimates of the mean sky brightness temperature in observing bands around 99 and 242 GHz due to line emission from distant galaxies. These values are calculated from the summed line emission observed in a blind, deep survey for spectral line emission from high redshift galaxies using ALMA (the ALMA spectral deep field observations “ASPECS” survey). In the 99 GHz band, the mean brightness will be dominated by rotational transitions of CO from intermediate and high redshift galaxies. In the 242 GHz band, the emission could be a combination of higher order CO lines, and possibly [C ii]more » 158 μ m line emission from very high redshift galaxies ( z  ∼ 6–7). The mean line surface brightness is a quantity that is relevant to measurements of spectral distortions of the cosmic microwave background, and as a potential tool for studying large-scale structures in the early universe using intensity mapping. While the cosmic volume and the number of detections are admittedly small, this pilot survey provides a direct measure of the mean line surface brightness, independent of conversion factors, excitation, or other galaxy formation model assumptions. The mean surface brightness in the 99 GHZ band is: T{sub B}  = 0.94 ± 0.09 μ K. In the 242 GHz band, the mean brightness is: T{sub B}  = 0.55 ± 0.033 μ K. These should be interpreted as lower limits on the average sky signal, since we only include lines detected individually in the blind survey, while in a low resolution intensity mapping experiment, there will also be the summed contribution from lower luminosity galaxies that cannot be detected individually in the current blind survey.« less

The Martian twilight

NASA Technical Reports Server (NTRS)

Kahn, R.; Goody, R.; Pollack, J.

1981-01-01

The changing sky brightness during the Martian twilight as measured by the Viking lander cameras is shown to be consistent with data obtained from sky brightness measurements. An exponential distribution of dust with a scale height of 10 km, equal to the atmospheric scale height, is consistent with the shape of the light curve. Multiple scattering resulting from the forward scattering peak of large particles makes a major contribution to the intensity of the twilight. The spectral distribution of light in the twilight sky may require slightly different optical properties for the scattering particles at high levels from those of the aerosol at lower levels.

An Estimation of the Gamma-Ray Burst Afterglow Apparent Optical Brightness Distribution Function

NASA Astrophysics Data System (ADS)

Akerlof, Carl W.; Swan, Heather F.

2007-12-01

By using recent publicly available observational data obtained in conjunction with the NASA Swift gamma-ray burst (GRB) mission and a novel data analysis technique, we have been able to make some rough estimates of the GRB afterglow apparent optical brightness distribution function. The results suggest that 71% of all burst afterglows have optical magnitudes with mR<22.1 at 1000 s after the burst onset, the dimmest detected object in the data sample. There is a strong indication that the apparent optical magnitude distribution function peaks at mR~19.5. Such estimates may prove useful in guiding future plans to improve GRB counterpart observation programs. The employed numerical techniques might find application in a variety of other data analysis problems in which the intrinsic distributions must be inferred from a heterogeneous sample.

Aerosol Optical Depth Distribution in Extratropical Cyclones over the Northern Hemisphere Oceans

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2016-01-01

Using Moderate Resolution Imaging Spectroradiometer and an extratropical cyclone database,the climatological distribution of aerosol optical depth (AOD) in extratropical cyclones is explored based solely on observations. Cyclone-centered composites of aerosol optical depth are constructed for the Northern Hemisphere mid-latitude ocean regions, and their seasonal variations are examined. These composites are found to be qualitatively stable when the impact of clouds and surface insolation or brightness is tested. The larger AODs occur in spring and summer and are preferentially found in the warm frontal and in the post-cold frontal regions in all seasons. The fine mode aerosols dominate the cold sector AODs, but the coarse mode aerosols display large AODs in the warm sector. These differences between the aerosol modes are related to the varying source regions of the aerosols and could potentially have different impacts on cloud and precipitation within the cyclones.

Distributed fluorescent optical fiber proximity sensor: Towards a proof of concept

NASA Astrophysics Data System (ADS)

Gălătuș, Ramona; Faragó, Paul; Miluski, Piotr; Valles, Juan-Antonio

2018-06-01

Fluorescent fibers are optical fibers which emit light as a response to an incident phenomenon, usually an incident light. Operation depends on the doping dyes, which determine specific fluorescence and optical characteristics useful in the development of optical sensors. In this work we propose a low-cost distributed proximity sensor implemented using a red fluorescent fiber, to provide a security option for a surface plasmon resonance system. Operation of the proposed sensor relies on having the incident illumination intensity varied by the presence or absence of an obstacle in the vicinity of the sensing element. This will influence the radiated fluorescence accordingly. The proposed setup for the implementation of the optical proximity sensor assumes having a high brightness LED deployed for axial fiber illumination and a blue LED for side illumination. Electronic processing then accounts for gain and digitization. Measurement results of the prototype validate the proposed concept.

Triton - Scattering models and surface/atmosphere constraints

NASA Technical Reports Server (NTRS)

Thompson, W. Reid

1989-01-01

Modeling of Triton's spectrum indicates a bright scattering layer of optical depth tau about 3 overlying an optically deep layer of CH4 with high absorption and little scattering. UV absorption in the spectrum indicates tau about 0.3 of red-yellow haze, although some color may also arise from complex organics partially visible on the surface. An analysis of this and other (spectro)photometric evidence indicates that Triton most likely has a bright surface, which was partially visible in 1977-1980. Geometric albedo p = 0.62 + 0.18 or - 0.12 radius r = 1480 + or - 180 km, and temperature T = 48 + or - 6 K. With scattering optical depths of 0.3-3 and about 1-10 mb of N2, a Mars-like atmospheric density and surface visibility pertain.

Venus - 3D Perspective View of Latona Corona and Dali Chasma

NASA Technical Reports Server (NTRS)

1992-01-01

This computer-generated perspective view of Latona Corona and Dali Chasma on Venus shows Magellan radar data superimposed on topography. The view is from the northeast and vertical exaggeration is 10 times. Exaggeration of relief is a common tool scientists use to detect relationships between structure (i.e. faults and fractures) and topography. Latona Corona, a circular feature approximately 1,000 kilometers (620 miles) in diameter whose eastern half is shown at the left of the image, has a relatively smooth, radar-bright raised rim. Bright lines or fractures within the corona appear to radiate away from its center toward the rim. The rest of the bright fractures in the area are associated with the relatively deep (approximately 3 kilometers or 1.9 miles) troughs of Dali Chasma. The Dali and Diana Chasma system consist of deep troughs that extend for 7,400 kilometers (4,588 miles) and are very distinct features on Venus. Those chasma connect the Ovda and Thetis highlands with the large volcanoes at Atla Regio and thus are considered to be the 'Scorpion Tail' of Aphrodite Terra. The broad, curving scarp resembles some of Earth's subduction zones where crustal plates are pushed over each other. The radar-bright surface at the highest elevation along the scarp is similar to surfaces in other elevated regions where some metallic mineral such as pyrite (fool's gold) may occur on the surface.

Seasonal variation of the radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS

NASA Astrophysics Data System (ADS)

Fujiwara, Hideaki; Morishima, Ryuji; Fujiyoshi, Takuya; Yamashita, Takuya

2017-03-01

Aims: This paper investigates the mid-infrared (MIR) characteristics of Saturn's rings. Methods: We collected and analyzed MIR high spatial resolution images of Saturn's rings obtained in January 2008 and April 2005 with the COoled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the Subaru Telescope, and investigated the spatial variation in the surface brightness of the rings in multiple bands in the MIR. We also composed the spectral energy distributions (SEDs) of the C, B, and A rings and the Cassini Division, and estimated the temperatures of the rings from the SEDs assuming the optical depths. Results: We found that the C ring and the Cassini Division were warmer than the B and A rings in 2008, which could be accounted for by their lower albedos, lower optical depths, and smaller self-shadowing effect. We also fonud that the C ring and the Cassini Division were considerably brighter than the B and A rings in the MIR in 2008 and the radial contrast of the ring brightness is the inverse of that in 2005, which is interpreted as a result of a seasonal effect with changing elevations of the Sun and observer above the ring plane. The reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A29

From 20 cm - 1 micron: Measuring the Gas and Dust in Massive Low Surface Brightness Galaxies

NASA Astrophysics Data System (ADS)

Kearsley, E.; O'Neil, K.

2005-12-01

Archival data from the IRAS, 2MASS, NVSS, and FIRST catalogs, supplemented with new measurements of HI, are used to analyze the relationship between the relative mass of the various components of galaxies (stars, atomic hydrogen, dust, and molecular gas) using a small sample of nearby (z<0.1), massive low surface brightness galaxies. The sample is compared to three sets of published data: a large collection of radio sources from the UGC having a radio continuum intensity >2.5 mJy (Condon, Cotton, & Broderick 2002 AJ 124, 675) ; a smaller sample of low surface brightness galaxies (Galaz, et al 2002 2002 AJ 124, 1360); and a collection of NIR low surface brightness galaxies (Monnier-Ragaigne, et al 2002 Ap&SS 281, 145). Overall, our sample properties are similar to the comparison samples in regard to NIR color, gas, stellar, and dynamic mass ratios, etc. Based off the galaxies' q-value (determined from the FIR/1.4 GHz ratio), it appears likely that at least two of the 28 galaxies studied harbor AGN. Notably, we also find that if we naively assume the ratio of the dust and molecular gas mass relative to the mass of HI is a constant we are unable to predict the observed ratio of stellar mass to HI mass, indicating that the HI mass ratio is a poor indicator of the total baryonic mass in the studied galaxies. HI measurements obtained during this study using the Green Bank Telescope also provide a correction to the velocity of UGC 11068.

BEYOND 31 mag arcsec{sup −2}: THE FRONTIER OF LOW SURFACE BRIGHTNESS IMAGING WITH THE LARGEST OPTICAL TELESCOPES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trujillo, Ignacio; Fliri, Jüergen, E-mail: trujillo@iac.es; Departamento de Astrofísica, Universidad de La Laguna, E-38206, La Laguna, Tenerife

2016-06-01

The detection of structures in the sky with optical surface brightnesses fainter than 30 mag arcsec{sup −2} (3 σ in 10 × 10 arcsec boxes; r -band) has remained elusive in current photometric deep surveys. Here we show how present-day telescopes of 10 m class can provide broadband imaging 1.5–2 mag deeper than most previous results within a reasonable amount of time (i.e., <10 hr on-source integration). In particular, we illustrate the ability of the 10.4 m Gran Telescopio de Canarias telescope to produce imaging with a limiting surface brightness of 31.5 mag arcsec{sup −2} (3 σ in 10 ×more » 10 arcsec boxes; r -band) using 8.1 hr on source. We apply this power to explore the stellar halo of the galaxy UGC 00180, a galaxy analogous to M31 located at ∼150 Mpc, by obtaining a radial profile of surface brightness down to μ{sub r} ∼ 33 mag arcsec{sup −2}. This depth is similar to that obtained using the star-counts techniques for Local Group galaxies, but is achieved at a distance where this technique is unfeasible. We find that the mass of the stellar halo of this galaxy is ∼4 × 10{sup 9} M {sub ⊙}, i.e., (3 ± 1)% of the total stellar mass of the whole system. This amount of mass in the stellar halo is in agreement with current theoretical expectations for galaxies of this kind.« less

49 CFR 213.337 - Defective rails.

Code of Federal Regulations, 2010 CFR

2010-10-01

... crystalline center or nucleus inside the head from which it spreads outward as a smooth, bright, or dark... a smooth, bright, or dark surface progressing until substantially at a right angle to the length of... through it. A crack or rust streak may show under the head close to the web or pieces may be split off the...

49 CFR 213.337 - Defective rails.

Code of Federal Regulations, 2011 CFR

2011-10-01

... crystalline center or nucleus inside the head from which it spreads outward as a smooth, bright, or dark... a smooth, bright, or dark surface progressing until substantially at a right angle to the length of... through it. A crack or rust streak may show under the head close to the web or pieces may be split off the...

49 CFR 213.337 - Defective rails.

Code of Federal Regulations, 2013 CFR

2013-10-01

... crystalline center or nucleus inside the head from which it spreads outward as a smooth, bright, or dark... a smooth, bright, or dark surface progressing until substantially at a right angle to the length of... through it. A crack or rust streak may show under the head close to the web or pieces may be split off the...

49 CFR 213.337 - Defective rails.

Code of Federal Regulations, 2012 CFR

2012-10-01

... crystalline center or nucleus inside the head from which it spreads outward as a smooth, bright, or dark... a smooth, bright, or dark surface progressing until substantially at a right angle to the length of... through it. A crack or rust streak may show under the head close to the web or pieces may be split off the...

49 CFR 213.337 - Defective rails.

Code of Federal Regulations, 2014 CFR

2014-10-01

... crystalline center or nucleus inside the head from which it spreads outward as a smooth, bright, or dark... a smooth, bright, or dark surface progressing until substantially at a right angle to the length of... through it. A crack or rust streak may show under the head close to the web or pieces may be split off the...

Correction of WindScat Scatterometric Measurements by Combining with AMSR Radiometric Data

NASA Technical Reports Server (NTRS)

Song, S.; Moore, R. K.

1996-01-01

The Seawinds scatterometer on the advanced Earth observing satellite-2 (ADEOS-2) will determine surface wind vectors by measuring the radar cross section. Multiple measurements will be made at different points in a wind-vector cell. When dense clouds and rain are present, the signal will be attenuated, thereby giving erroneous results for the wind. This report describes algorithms to use with the advanced mechanically scanned radiometer (AMSR) scanning radiometer on ADEOS-2 to correct for the attenuation. One can determine attenuation from a radiometer measurement based on the excess brightness temperature measured. This is the difference between the total measured brightness temperature and the contribution from surface emission. A major problem that the algorithm must address is determining the surface contribution. Two basic approaches were developed for this, one using the scattering coefficient measured along with the brightness temperature, and the other using the brightness temperature alone. For both methods, best results will occur if the wind from the preceding wind-vector cell can be used as an input to the algorithm. In the method based on the scattering coefficient, we need the wind direction from the preceding cell. In the method using brightness temperature alone, we need the wind speed from the preceding cell. If neither is available, the algorithm can work, but the corrections will be less accurate. Both correction methods require iterative solutions. Simulations show that the algorithms make significant improvements in the measured scattering coefficient and thus is the retrieved wind vector. For stratiform rains, the errors without correction can be quite large, so the correction makes a major improvement. For systems of separated convective cells, the initial error is smaller and the correction, although about the same percentage, has a smaller effect.

Stellar systems in the direction of the Hickson Compact Group 44. I. Low surface brightness galaxies

NASA Astrophysics Data System (ADS)

Smith Castelli, A. V.; Faifer, F. R.; Escudero, C. G.

2016-11-01

Context. In spite of the numerous studies of low-luminosity galaxies in different environments, there is still no consensus about their formation scenario. In particular, a large number of galaxies displaying extremely low-surface brightnesses have been detected in the last year, and the nature of these objects is under discussion. Aims: In this paper we report the detection of two extended low-surface brightness (LSB) objects (μeffg' ≃ 27 mag) found, in projection, next to NGC 3193 and in the zone of the Hickson Compact Group (HCG) 44, respectively. Methods: We analyzed deep, high-quality, GEMINI-GMOS images with ELLIPSE within IRAF in order to obtain their brightness profiles and structural parameters. We also searched for the presence of globular clusters (GC) in these fields. Results: We have found that, if these LSB galaxies were at the distances of NGC 3193 and HCG 44, they would show sizes and luminosities similar to those of the ultra-diffuse galaxies (UDGs) found in the Coma cluster and other associations. In that case, their sizes would be rather larger than those displayed by the Local Group dwarf spheroidal (dSph) galaxies. We have detected a few unresolved sources in the sky zone occupied by these galaxies showing colors and brightnesses typical of blue globular clusters. Conclusions: From the comparison of the properties of the galaxies presented in this work with those of similar objects reported in the literature, we have found that LSB galaxies display sizes covering a quite extended continous range (reff 0.3-4.5 kpc), in contrast to "normal" early-type galaxies, which show reff 1.0 kpc with a low dispersion. This fact might point to different formation processes for both types of galaxies.

Surface Photometric Properties of HII Galaxies

NASA Astrophysics Data System (ADS)

Vajgel, B.; Telles, E.

2009-05-01

HII galaxies are dwarf galaxies undergoing violent star formation. They were firstly selected by objective-prism spectroscopy and were object of extensive studies to characterize their physical conditions of the interstellar medium. Their SFR together with their low Z raised the question whether some of them can be truly ``young'' galaxies. To infer the SFH, one needs information in a large spectral range. We obtained images in the optical region of the spectrum with the 0.6 m B&C and the 1.6 m telescopes at the Laboratório Nacional de Astrofísica, for a sample of 50 objects in B, V, R and I, which combined with recent evolutionary models, enable us to deduce the stellar population content and its spatial distribution. These seem to be the nearest youngest galaxies that can be studied in detail, and their structural properties offer important indications about the evolutionary relation and the origin of dwarf galaxies in the universe. With this sample we built a morphological catalogue with broad-band photometry, including the structural analysis through the brightness profiles. The initial analysis suggests that the galaxies can be segregated in two broad classes, in agreement with what had already been proposed in the literature; Type I have irregular envelopes with signs of perturbation and turn out to the more luminous sub-sample; while Type II have regular external isophotes and are less luminous. The brightness profiles are well represented by exponential fits, as in irregular and elliptical dwarf galaxies. However, HII galaxies are more compact in comparison with their more diffuse counterparts. We study the behavior of the HII galaxies in the metallicity-luminosity plane. This relation, interpreted as a relation between the mass and the metallicity of dwarf galaxies of low surface brightness (dE and dIrr), has direct implications for their formation and evolution, and over the possible evolutionary links between HII galaxies and other types of dwarf galaxies.

Ceres During Opposition Surge.

NASA Image and Video Library

2017-05-16

NASA's Dawn spacecraft successfully observed Ceres at opposition on April 29, 2017, taking images from a position exactly between the sun and Ceres' surface. Mission specialists had carefully maneuvered Dawn into a special orbit so that the spacecraft could view Occator Crater, which contains the brightest area of Ceres, from this new perspective. A movie shows these opposition images, with contrast enhanced to highlight brightness differences. The bright spots of Occator stand out particularly well on an otherwise relatively bland surface. Dawn took these images from an altitude of about 12,000 miles (20,000 kilometers). Based on data from ground-based telescopes and spacecraft that have previously viewed planetary bodies at opposition, scientists predicted that Ceres would appear brighter from this opposition configuration. This increase in brightness, or "surge," relates the size of the grains of material on the surface, as well as how porous those materials are. The science motivation for performing these observations is further explained in the March 2017 issue of the Dawn Journal blog. A movie can be viewed at https://photojournal.jpl.nasa.gov/catalog/PIA21405

Lenstronomy: Multi-purpose gravitational lens modeling software package

NASA Astrophysics Data System (ADS)

Birrer, Simon; Amara, Adam

2018-04-01

Lenstronomy is a multi-purpose open-source gravitational lens modeling python package. Lenstronomy reconstructs the lens mass and surface brightness distributions of strong lensing systems using forward modelling and supports a wide range of analytic lens and light models in arbitrary combination. The software is also able to reconstruct complex extended sources as well as point sources. Lenstronomy is flexible and numerically accurate, with a clear user interface that could be deployed across different platforms. Lenstronomy has been used to derive constraints on dark matter properties in strong lenses, measure the expansion history of the universe with time-delay cosmography, measure cosmic shear with Einstein rings, and decompose quasar and host galaxy light.

Photometric evidence on long-term stability of albedo and colour markings on Io

NASA Technical Reports Server (NTRS)

Morrison, D.; Pieri, D.; Johnson, T. V.; Veverka, J.

1979-01-01

Photometric measurements of the color and albedo of Io during the last 50 years are examined in order to determine the stability of the Ionian surface. Brightness measurements of Io relative to Ganymede show a slight, however inconclusive, increase with time, while light curve amplitudes and shapes are found to agree well during this period. The extent of volcanic activity observed by Voyager 1, however, is shown to be undetectable with the precision attainable by earth-based albedo determinations, and just barely detectable as color changes, which explains the observed photometric stability. Possible mechanisms for the preservation of the observed longitudinal distribution of color on Io are also discussed.

VLTI + MIDI Study of the High Mass Protostellar Candidate NGC 3603 IRS 9A

NASA Astrophysics Data System (ADS)

Nürnberger, D. E. A.; Vehoff, S.; Hummel, C. A.; Duschl, W. J.

2010-02-01

The formation and early evolution of high mass stars is among the hottest topics in astrophysics. Interferometric studies of these young stars and their circumstellar environments (envelopes, disks and jets) at near and mid infrared wavelengths are still rare and in terms of data analysis/interpretation very challenging. We here report on observations of the high mass protostellar candidate NGC 3603 IRS 9A which we undertook with VLTI + MIDI in 2005, complemented by near and mid infrared imaging and spectroscopic data. We discuss our results obtained from dedicated modeling efforts, employing both DUSTY and MC3D radiative transfer codes for a selected number of source geometries and surface brightness distributions.

Modeling the nucleus and jets of comet 81P/Wild 2 based on the Stardust encounter data

NASA Technical Reports Server (NTRS)

Sekanina, Zdenek; Brownlee, Donald E.; Economou, Thanasis E.; Tuzzolino, Anthony J.; Green, Simon F.

2004-01-01

We interpret the nucleus properties and jet activity from the Stardust spacecraft imaging and the onboard dust monitoring system data. Triangulation of 20 jets shows that 2 emanate from the nucleus dark side and 16 emanate from sources that are on slopes where the Sun's elevation is greater than predicted from the fitted triaxial ellipsoid. Seven sources, including five in the Mayo depression, coincide with relatively bright surface spots. Fitting the imaged jets, the spikelike temporal distribution of dust impacts indicates that the spacecraft crossed thin, densely populated sheets of particulate ejecta extending from small sources on the rotating nucleus, consistent with an emission cone model.

The core of the nearby S0 galaxy NGC 7457 imaged with the HST planetary camera

NASA Technical Reports Server (NTRS)

Lauer, Tod R.; Faber, S. M.; Holtzman, Jon A.; Baum, William A.; Currie, Douglas G.; Ewald, S. P.; Groth, Edward J.; Hester, J. Jeff; Kelsall, T.

1991-01-01

A brief analysis is presented of images of the nearby S0 galaxy NGC 7457 obtained with the HST Planetary Camera. While the galaxy remains unresolved with the HST, the images reveal that any core most likely has r(c) less than 0.052 arcsec. The light distribution is consistent with a gamma = -1.0 power law inward to the resolution limit, with a possible stellar nucleus with luminosity of 10 million solar. This result represents the first observation outside the Local Group of a galaxy nucleus at this spatial resolution, and it suggests that such small, high surface brightness cores may be common.

Bright Stuff on Ceres = Sulfates and Carbonates on CI Chondrites

NASA Technical Reports Server (NTRS)

Zolensky, Michael; Chan, Queenie H. S.; Gounelle, Matthieu; Fries, Marc

2016-01-01

Recent reports of the DAWN spacecraft's observations of the surface of Ceres indicate that there are bright areas, which can be explained by large amounts of the Mg sulfate hexahydrate (MgSO4•6(H2O)), although the identification appears tenuous. There are preliminary indications that water is being evolved from these bright areas, and some have inferred that these might be sites of contemporary hydro-volcanism. A heat source for such modern activity is not obvious, given the small size of Ceres, lack of any tidal forces from nearby giant planets, probable age and presumed bulk composition. We contend that observations of chondritic materials in the lab shed light on the nature of the bright spots on Ceres

Rosette globulettes and shells in the infrared

NASA Astrophysics Data System (ADS)

Mäkelä, M. M.; Haikala, L. K.; Gahm, G. F.

2014-07-01

Context. Giant galactic H ii regions surrounding central young clusters show compressed molecular shells, which have broken up into clumps, filaments, and elephant trunks interacting with UV light from central OB stars. Tiny, dense clumps of subsolar mass, called globulettes, form in this environment. Aims: We observe and explore the nature and origin of the infrared emission and extinction in these cool, dusty shell features and globulettes in one H ii region, the Rosette nebula, and search for associated newborn stars. Methods: We imaged the northwestern quadrant of the Rosette nebula in the near-infrared (NIR) through wideband JHKs filters and narrowband H2 1-0 S(1) and Pβ plus continuum filters using the Son of Isaac (SOFI) instrument at the New Technology Telescope (NTT) at European Southern Observatory (ESO). We used the NIR images to study the surface brightness of the globulettes and associated bright rims. We used the NIR JHKs photometry to create a visual extinction map and to search for objects with NIR excess emission. In addition, archival images from Spitzer Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 μm and Herschel Photoconductor Array Camera and Spectrometer (PACS) observations, covering several bands in the mid-infrared and far-infrared, were used to further analyze the stellar population, to examine the structure of the trunks and other shell structures and to study this Rosette nebula photon-dominated region in more detail. Results: The globulettes and elephant trunks have bright rims in the Ks band, which are unresolved in our images, on the sides facing the central cluster. An analysis of 21 globulettes, where surface brightness in the H2 1-0 S(1) line at 2.12 μm is detected, shows that approximately a third of the surface brightness observed in the Ks filter is due to this line: the observed average of the H2/Ks surface brightness is 0.26 ± 0.02 in the globulettes' cores and 0.30 ± 0.01 in the rims. The estimated H2 1-0 S(1) surface brightness of the rims is ˜3-8 × 10-8 Wm-2 sr-1μm-1. The ratio of the surface brightnesses support fluorescence instead of shocks as the H2 excitation mechanism. The globulettes have number densities of n(H2) ˜ 10-4 cm-3 or higher. We estimated masses of individual globulettes and compared them to the results from previous optical and radio molecular line surveys. We confirm that the larger globulettes contain very dense cores, that the density is also high farther out from the core, and that their mass is subsolar. Two NIR protostellar objects were found in an elephant trunk and one was found in the most massive globulette in our study. Based on observations done at the European Southern Observatory, La Silla, Chile (ESO programmes 084.C-0299 and 088.C-0630).Appendix A is only available in electronic form at http://www.aanda.orgTables 5 and 6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A108

On the Response of the Special Sensor Microwave/Imager to the Marine Environment: Implications for Atmospheric Parameter Retrievals. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Petty, Grant W.

1990-01-01

A reasonably rigorous basis for understanding and extracting the physical information content of Special Sensor Microwave/Imager (SSM/I) satellite images of the marine environment is provided. To this end, a comprehensive algebraic parameterization is developed for the response of the SSM/I to a set of nine atmospheric and ocean surface parameters. The brightness temperature model includes a closed-form approximation to microwave radiative transfer in a non-scattering atmosphere and fitted models for surface emission and scattering based on geometric optics calculations for the roughened sea surface. The combined model is empirically tuned using suitable sets of SSM/I data and coincident surface observations. The brightness temperature model is then used to examine the sensitivity of the SSM/I to realistic variations in the scene being observed and to evaluate the theoretical maximum precision of global SSM/I retrievals of integrated water vapor, integrated cloud liquid water, and surface wind speed. A general minimum-variance method for optimally retrieving geophysical parameters from multichannel brightness temperature measurements is outlined, and several global statistical constraints of the type required by this method are computed. Finally, a unified set of efficient statistical and semi-physical algorithms is presented for obtaining fields of surface wind speed, integrated water vapor, cloud liquid water, and precipitation from SSM/I brightness temperature data. Features include: a semi-physical method for retrieving integrated cloud liquid water at 15 km resolution and with rms errors as small as approximately 0.02 kg/sq m; a 3-channel statistical algorithm for integrated water vapor which was constructed so as to have improved linear response to water vapor and reduced sensitivity to precipitation; and two complementary indices of precipitation activity (based on 37 GHz attenuation and 85 GHz scattering, respectively), each of which are relatively insensitive to variations in other environmental parameters.

Clusters in Formation - The Case of 3C61.1 and A Luminous AGN in a Merging Cluster

NASA Astrophysics Data System (ADS)

Kraft, Ralph

2017-09-01

We propose a Chandra investigation of the serendipitously detected cluster, X-CLASS 1835, that hosts the classical FRII radio source 3C61.1 as well as a radiatively efficient, X-ray bright AGN. The cluster exhibits a prominent surface brightness edge which suggests a merger and/or a major AGN outburst. The radio emission from 3C61.1 shows interaction with the hot cluster plasma. We will characterize the merger/outburst by measuring the properties of the surface brightness edge, study the interaction of the FRII radio source (its hotspots, jet, and cocoon) with the ICM, measure spectra of 3C61.1 (nucleus and hotspots) and the AGN to explore their physical properties, and measure the PV work from any detected cavities around 3C61.1 to compare to the radio power.

RESOLVE: A new algorithm for aperture synthesis imaging of extended emission in radio astronomy

NASA Astrophysics Data System (ADS)

Junklewitz, H.; Bell, M. R.; Selig, M.; Enßlin, T. A.

2016-02-01

We present resolve, a new algorithm for radio aperture synthesis imaging of extended and diffuse emission in total intensity. The algorithm is derived using Bayesian statistical inference techniques, estimating the surface brightness in the sky assuming a priori log-normal statistics. resolve estimates the measured sky brightness in total intensity, and the spatial correlation structure in the sky, which is used to guide the algorithm to an optimal reconstruction of extended and diffuse sources. During this process, the algorithm succeeds in deconvolving the effects of the radio interferometric point spread function. Additionally, resolve provides a map with an uncertainty estimate of the reconstructed surface brightness. Furthermore, with resolve we introduce a new, optimal visibility weighting scheme that can be viewed as an extension to robust weighting. In tests using simulated observations, the algorithm shows improved performance against two standard imaging approaches for extended sources, Multiscale-CLEAN and the Maximum Entropy Method.

Studies of Isolated and Non-isolated Photospheric Bright Points in an Active Region Observed by the New Vacuum Solar Telescope

NASA Astrophysics Data System (ADS)

Liu, Yanxiao; Xiang, Yongyuan; Erdélyi, Robertus; Liu, Zhong; Li, Dong; Ning, Zongjun; Bi, Yi; Wu, Ning; Lin, Jun

2018-03-01

Properties of photospheric bright points (BPs) near an active region have been studied in TiO λ 7058 Å images observed by the New Vacuum Solar Telescope of the Yunnan Observatories. We developed a novel recognition method that was used to identify and track 2010 BPs. The observed evolving BPs are classified into isolated (individual) and non-isolated (where multiple BPs are observed to display splitting and merging behaviors) sets. About 35.1% of BPs are non-isolated. For both isolated and non-isolated BPs, the brightness varies from 0.8 to 1.3 times the average background intensity and follows a Gaussian distribution. The lifetimes of BPs follow a log-normal distribution, with characteristic lifetimes of (267 ± 140) s and (421 ± 255) s, respectively. Their size also follows log-normal distribution, with an average size of about (2.15 ± 0.74) × 104 km2 and (3.00 ± 1.31) × 104 km2 for area, and (163 ± 27) km and (191 ± 40) km for diameter, respectively. Our results indicate that regions with strong background magnetic field have higher BP number density and higher BP area coverage than regions with weak background field. Apparently, the brightness/size of BPs does not depend on the background field. Lifetimes in regions with strong background magnetic field are shorter than those in regions with weak background field, on average.

Passive microwave sensing of soil moisture content: Soil bulk density and surface roughness

NASA Technical Reports Server (NTRS)

Wang, J. R.

1982-01-01

Microwave radiometric measurements over bare fields of different surface roughnesses were made at the frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz to study the frequency dependence as well as the possible time variation of surface roughness. The presence of surface roughness was found to increase the brightness temperature of soils and reduce the slope of regression between brightness temperature and soil moisture content. The frequency dependence of the surface roughness effect was relatively weak when compared with that of the vegetation effect. Radiometric time series observation over a given field indicated that field surface roughness might gradually diminish with time, especially after a rainfall or irrigation. This time variation of surface roughness served to enhance the uncertainty in remote soil moisture estimate by microwave radiometry. Three years of radiometric measurements over a test site revealed a possible inconsistency in the soil bulk density determination, which turned out to be an important factor in the interpretation of radiometric data.

Passive microwave sensing of soil moisture content - The effects of soil bulk density and surface roughness

NASA Technical Reports Server (NTRS)

Wang, J. R.

1983-01-01

Microwave radiometric measurements over bare fields of different surface roughness were made at frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz to study the frequency dependence, as well as the possible time variation, of surface roughness. An increase in surface roughness was found to increase the brightness temperature of soils and reduce the slope of regression between brightness temperature and soil moisture content. The frequency dependence of the surface roughness effect was relatively weak when compared with that of the vegetation effect. Radiometric time-series observations over a given field indicate that field surface roughness might gradually diminish with time, especially after a rainfall or irrigation. The variation of surface roughness increases the uncertainty of remote soil moisture estimates by microwave radiometry. Three years of radiometric measurements over a test site revealed a possible inconsistency in the soil bulk density determination, which is an important factor in the interpretation of radiometric data.

The nature of solar brightness variations

NASA Astrophysics Data System (ADS)

Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Cameron, R. H.; Yeo, K. L.; Schmutz, W. K.

2017-09-01

Determining the sources of solar brightness variations1,2, often referred to as solar noise3, is important because solar noise limits the detection of solar oscillations3, is one of the drivers of the Earth's climate system4,5 and is a prototype of stellar variability6,7—an important limiting factor for the detection of extrasolar planets. Here, we model the magnetic contribution to solar brightness variability using high-cadence8,9 observations from the Solar Dynamics Observatory (SDO) and the Spectral And Total Irradiance REconstruction (SATIRE)10,11 model. The brightness variations caused by the constantly evolving cellular granulation pattern on the solar surface were computed with the Max Planck Institute for Solar System Research (MPS)/University of Chicago Radiative Magnetohydrodynamics (MURaM)12 code. We found that the surface magnetic field and granulation can together precisely explain solar noise (that is, solar variability excluding oscillations) on timescales from minutes to decades, accounting for all timescales that have so far been resolved or covered by irradiance measurements. We demonstrate that no other sources of variability are required to explain the data. Recent measurements of Sun-like stars by the COnvection ROtation and planetary Transits (CoRoT)13 and Kepler14 missions uncovered brightness variations similar to that of the Sun, but with a much wider variety of patterns15. Our finding that solar brightness variations can be replicated in detail with just two well-known sources will greatly simplify future modelling of existing CoRoT and Kepler as well as anticipated Transiting Exoplanet Survey Satellite16 and PLAnetary Transits and Oscillations of stars (PLATO)17 data.

Local stability of galactic discs in modified dynamics

NASA Astrophysics Data System (ADS)

Shenavar, Hossein; Ghafourian, Neda

2018-04-01

The local stability of stellar and fluid discs, under a new modified dynamical model, is surveyed by using WKB approximation. The exact form of the modified Toomre criterion is derived for both types of systems and it is shown that the new model is, in all situations, more locally stable than Newtonian model. In addition, it has been proved that the central surface density of the galaxies plays an important role in the local stability in the sense that low surface brightness (LSB) galaxies are more stable than high surface brightness (HSBs). Furthermore, the growth rate in the new model is found to be lower than the Newtonian one. We found that, according to this model, the local instability is related to the ratio of surface density of the disc to a critical surface density Σcrit. We provide observational evidence to support this result based on star formation rate in HSBs and LSBs.

Artificial light alters natural regimes of night-time sky brightness

PubMed Central

Davies, Thomas W.; Bennie, Jonathan; Inger, Richard; Gaston, Kevin J.

2013-01-01

Artificial light is globally one of the most widely distributed forms of anthropogenic pollution. However, while both the nature and ecological effects of direct artificial lighting are increasingly well documented, those of artificial sky glow have received little attention. We investigated how city lights alter natural regimes of lunar sky brightness using a novel ten month time series of measurements recorded across a gradient of increasing light pollution. In the city, artificial lights increased sky brightness to levels six times above those recorded in rural locations, nine and twenty kilometers away. Artificial lighting masked natural monthly and seasonal regimes of lunar sky brightness in the city, and increased the number and annual regime of full moon equivalent hours available to organisms during the night. The changes have potentially profound ecological consequences.

ALMA 1.3 mm Map of the HD 95086 System

NASA Astrophysics Data System (ADS)

Su, Kate Y. L.; MacGregor, Meredith A.; Booth, Mark; Wilner, David J.; Flaherty, Kevin; Hughes, A. Meredith; Phillips, Neil M.; Malhotra, Renu; Hales, Antonio S.; Morrison, Sarah; Ertel, Steve; Matthews, Brenda C.; Dent, William R. F.; Casassus, Simon

2017-12-01

Planets and minor bodies such as asteroids, Kuiper-Belt objects, and comets are integral components of a planetary system. Interactions among them leave clues about the formation process of a planetary system. The signature of such interactions is most prominent through observations of its debris disk at millimeter wavelengths where emission is dominated by the population of large grains that stay close to their parent bodies. Here we present ALMA 1.3 mm observations of HD 95086, a young early-type star that hosts a directly imaged giant planet b and a massive debris disk with both asteroid- and Kuiper-Belt analogs. The location of the Kuiper-Belt analog is resolved for the first time. The system can be depicted as a broad (ΔR/R ˜ 0.84), inclined (30° ± 3°) ring with millimeter emission peaked at 200 ± 6 au from the star. The 1.3 mm disk emission is consistent with a broad disk with sharp boundaries from 106 ± 6 to 320 ± 20 au with a surface density distribution described by a power law with an index of -0.5 ± 0.2. Our deep ALMA map also reveals a bright source located near the edge of the ring, whose brightness at 1.3 mm and potential spectral energy distribution are consistent with it being a luminous star-forming galaxy at high redshift. We set constraints on the orbital properties of planet b assuming coplanarity with the observed disk.

Extreme Brightness Temperatures and Refractive Substructure in 3C273 with RadioAstron

NASA Astrophysics Data System (ADS)

Johnson, Michael D.; Kovalev, Yuri Y.; Gwinn, Carl R.; Gurvits, Leonid I.; Narayan, Ramesh; Macquart, Jean-Pierre; Jauncey, David L.; Voitsik, Peter A.; Anderson, James M.; Sokolovsky, Kirill V.; Lisakov, Mikhail M.

2016-03-01

Earth-space interferometry with RadioAstron provides the highest direct angular resolution ever achieved in astronomy at any wavelength. RadioAstron detections of the classic quasar 3C 273 on interferometric baselines up to 171,000 km suggest brightness temperatures exceeding expected limits from the “inverse-Compton catastrophe” by two orders of magnitude. We show that at 18 cm, these estimates most likely arise from refractive substructure introduced by scattering in the interstellar medium. We use the scattering properties to estimate an intrinsic brightness temperature of 7× {10}12 {{K}}, which is consistent with expected theoretical limits, but which is ˜15 times lower than estimates that neglect substructure. At 6.2 cm, the substructure influences the measured values appreciably but gives an estimated brightness temperature that is comparable to models that do not account for the substructure. At 1.35 {{cm}}, the substructure does not affect the extremely high inferred brightness temperatures, in excess of {10}13 {{K}}. We also demonstrate that for a source having a Gaussian surface brightness profile, a single long-baseline estimate of refractive substructure determines an absolute minimum brightness temperature, if the scattering properties along a given line of sight are known, and that this minimum accurately approximates the apparent brightness temperature over a wide range of total flux densities.

Bolivia

Atmospheric Science Data Center

2013-04-18

... in brightness between them. Varying degrees of surface moisture around the two playas are illustrated by the different display ... angular composites contain information relating to surface moisture and/or texture characteristics that are not apparent with a single ...

AGE AND STRUCTURE PARAMETERS OF THE REMOTE M31 GLOBULAR CLUSTER B514 BASED ON HST, 2MASS, GALEX, AND BATC OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma Jun; Wang Song; Wu Zhenyu

2012-02-15

B514 is a remote M31 globular cluster (GC) which is located at a projected distance of R{sub p} {approx_equal} 55 kpc. Deep observations with the Advanced Camera for Surveys on the Hubble Space Telescope are used to provide accurate integrated light and star counts of B514. By coupling the analysis of the distribution of the integrated light with star counts, we are able to reliably follow the profile of the cluster out to {approx}40''. Based on the combined profile, we study in detail its surface brightness distribution in the F606W and F814W filters and determine its structural parameters by fittingmore » a single-mass isotropic King model. The results showed that the surface brightness distribution departs from the best-fit King model for r > 10''. B514 is quite flat in the inner region and has a larger half-light radius than the majority of normal GCs of the same luminosity. It is interesting that, in the M{sub V} versus log R{sub h} plane, B514 lies nearly on the threshold for ordinary GCs as defined by Mackey and van den Bergh. In addition, B514 was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey, using 13 intermediate-band filters covering a wavelength range of 3000-8500 A. Based on aperture photometry, we obtain its spectral energy distributions (SEDs) as defined by the 13 BATC filters. We determine the cluster's age and mass by comparing its SEDs (from 2267 to 20000 Angstrom-Sign , comprised of photometric data from the near-ultraviolet band of the Galaxy Evolution Explorer, 5 Sloan Digital Sky Survey bands, 13 BATC intermediate-band filters, and Two Micron All Sky Survey near-infrared JHK{sub s} filters) with theoretical stellar population synthesis models, resulting in an age of 11.5 {+-} 3.5 Gyr. This age confirms the previous suggestion that B514 is an old GC in M31. B514 has a mass of 0.96-1.08 Multiplication-Sign 10{sup 6} M{sub Sun} and is a medium-mass GC in M31.« less

The formation of giant low surface brightness galaxies

NASA Technical Reports Server (NTRS)

Hoffman, Yehuda; Silk, Joseph; Wyse, Rosemary F. G.

1992-01-01

It is demonstrated that the initial structure of galaxies can be strongly affected by their large-scale environments. In particular, rare (about 3 sigma) massive galaxies in voids will have normal bulges, but unevolved, extended disks; it is proposed that the low surface brightness objects Malin I and Malin II are prototypes of this class of object. The model predicts that searches for more examples of 'crouching giants' should be fruitful, but that such galaxies do not provide a substantial fraction of mass in the universe. The identification of dwarf galaxies is relatively unaffected by their environment.

K-band observations of boxy bulges - I. Morphology and surface brightness profiles

NASA Astrophysics Data System (ADS)

Bureau, M.; Aronica, G.; Athanassoula, E.; Dettmar, R.-J.; Bosma, A.; Freeman, K. C.

2006-08-01

In this first paper of a series on the structure of boxy and peanut-shaped (B/PS) bulges, Kn-band observations of a sample of 30 edge-on spiral galaxies are described and discussed. Kn-band observations best trace the dominant luminous galactic mass and are minimally affected by dust. Images, unsharp-masked images, as well as major-axis and vertically summed surface brightness profiles are presented and discussed. Galaxies with a B/PS bulge tend to have a more complex morphology than galaxies with other bulge types, more often showing centred or off-centred X structures, secondary maxima along the major-axis and spiral-like structures. While probably not uniquely related to bars, those features are observed in three-dimensional N-body simulations of barred discs and may trace the main bar orbit families. The surface brightness profiles of galaxies with a B/PS bulge are also more complex, typically containing three or more clearly separated regions, including a shallow or flat intermediate region (Freeman Type II profiles). The breaks in the profiles offer evidence for bar-driven transfer of angular momentum and radial redistribution of material. The profiles further suggest a rapid variation of the scaleheight of the disc material, contrary to conventional wisdom but again as expected from the vertical resonances and instabilities present in barred discs. Interestingly, the steep inner region of the surface brightness profiles is often shorter than the isophotally thick part of the galaxies, itself always shorter than the flat intermediate region of the profiles. The steep inner region is also much more prominent along the major-axis than in the vertically summed profiles. Similarly to other recent work but contrary to the standard `bulge + disc' model (where the bulge is both thick and steep), we thus propose that galaxies with a B/PS bulge are composed of a thin concentrated disc (a disc-like bulge) contained within a partially thick bar (the B/PS bulge), itself contained within a thin outer disc. The inner disc likely formed secularly through bar-driven processes and is responsible for the steep inner region of the surface brightness profiles, traditionally associated with a classic bulge, while the bar is responsible for the flat intermediate region of the surface brightness profiles and the thick complex morphological structures observed. Those components are strongly coupled dynamically and are formed mostly of the same (disc) material, shaped by the weak but relentless action of the bar resonances. Any competing formation scenario for galaxies with a B/PS bulge, which represent at least 45 per cent of the local disc galaxy population, must explain equally well and self-consistently the above morphological and photometric properties, the complex gas and stellar kinematics observed, and the correlations between them.

Simultaneous Multi-band Detection of Low Surface Brightness Galaxies with Markovian Modeling

NASA Astrophysics Data System (ADS)

Vollmer, B.; Perret, B.; Petremand, M.; Lavigne, F.; Collet, Ch.; van Driel, W.; Bonnarel, F.; Louys, M.; Sabatini, S.; MacArthur, L. A.

2013-02-01

We present to the astronomical community an algorithm for the detection of low surface brightness (LSB) galaxies in images, called MARSIAA (MARkovian Software for Image Analysis in Astronomy), which is based on multi-scale Markovian modeling. MARSIAA can be applied simultaneously to different bands. It segments an image into a user-defined number of classes, according to their surface brightness and surroundings—typically, one or two classes contain the LSB structures. We have developed an algorithm, called DetectLSB, which allows the efficient identification of LSB galaxies from among the candidate sources selected by MARSIAA. The application of the method to two and three bands simultaneously was tested on simulated images. Based on our tests, we are confident that we can detect LSB galaxies down to a central surface brightness level of only 1.5 times the standard deviation from the mean pixel value in the image background. To assess the robustness of our method, the method was applied to a set of 18 B- and I-band images (covering 1.3 deg2 in total) of the Virgo Cluster to which Sabatini et al. previously applied a matched-filter dwarf LSB galaxy search algorithm. We have detected all 20 objects from the Sabatini et al. catalog which we could classify by eye as bona fide LSB galaxies. Our method has also detected four additional Virgo Cluster LSB galaxy candidates undetected by Sabatini et al. To further assess the completeness of the results of our method, both MARSIAA, SExtractor, and DetectLSB were applied to search for (1) mock Virgo LSB galaxies inserted into a set of deep Next Generation Virgo Survey (NGVS) gri-band subimages and (2) Virgo LSB galaxies identified by eye in a full set of NGVS square degree gri images. MARSIAA/DetectLSB recovered ~20% more mock LSB galaxies and ~40% more LSB galaxies identified by eye than SExtractor/DetectLSB. With a 90% fraction of false positives from an entirely unsupervised pipeline, a completeness of 90% is reached for sources with r e > 3'' at a mean surface brightness level of μg = 27.7 mag arcsec-2 and a central surface brightness of μ0 g = 26.7 mag arcsec-2. About 10% of the false positives are artifacts, the rest being background galaxies. We have found our proposed Markovian LSB galaxy detection method to be complementary to the application of matched filters and an optimized use of SExtractor, and to have the following advantages: it is scale free, can be applied simultaneously to several bands, and is well adapted for crowded regions on the sky. .

Effect of the Solar UV/EUV Heating on the Intensity and Spatial Distribution of Jupiter's Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Kita, Hajime; Misawa, H.; Tsuchiya, F.; Tao, C.; Morioka, A.

2012-10-01

Jupiter's synchrotron radiation (JSR) is the emission from relativistic electrons, and it is the most effective probe for remote sensing of Jupiter's radiation belt from the Earth. Recent observations reveal short term variations of JSR with the time scale of days to weeks. Brice and McDonough (1973) proposed that the solar UV/EUV heating for Jupiter's upper atmosphere causes enhancement of total flux density. If such a process occurs at Jupiter, it is also expected that diurnal wind system produces dawn-dusk asymmetry of the JSR brightness distribution. Preceding studies confirmed that the short term variations in total flux density correspond to the solar UV/EUV. However, the effect of solar UV/EUV heating on the brightness distribution has not been confirmed. Hence, the purpose of this study is to confirm the solar UV/EUV heating effect on total flux density and brightness distribution. We made radio imaging analysis using the National Radio Astronomy Observatory (NRAO) archived data of the Very Large Array (VLA) obtained in 2000, and following results were shown. 1, Total flux density varied corresponding to the solar UV/EUV. 2, Dawn side emission was brighter than dusk side emission almost every day. 3, Variations of the dawn-dusk asymmetry did not correspond to the solar UV/EUV. In order to explain the second result, we estimate the diurnal wind velocity from the observed dawn-dusk ratio by using the model brightness distribution of JSR. Estimated neutral wind velocity is 46+/-11 m/s, which reasonably corresponds to the numerical simulation of Jupiter's upper atmosphere. In order to explain the third result, we examined the effect of the global convection electric field driven by tailward outflow of plasma in Jupiter's magnetosphere. As the result, it is suggested that typical fluctuation of the convection electric field strength was enough to cause the observed variations of the dawn-dusk asymmetry.

Observational difference between gamma and X-ray properties of optically dark and bright GRBs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balazs, L. G.; Horvath, I.; Bagoly, Zs.

2008-05-22

Using the discriminant analysis of the multivariate statistical analysis we compared the distribution of the physical quantities of the optically dark and bright GRBs, detected by the BAT and XRT on board of the Swift Satellite. We found that the GRBs having detected optical transients (OT) have systematically higher peak fluxes and lower HI column densities than those without OT.

Curved Radio Spectra of Weak Cluster Shocks

NASA Astrophysics Data System (ADS)

Kang, Hyesung; Ryu, Dongsu

2015-08-01

In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed {u}{{s}}˜ 3× {10}3 {km} {{{s}}}-1 and sonic Mach number {M}{{s}}˜ 3. These shocks produce curved radio spectra that steepen gradually over (0.1-10){ν }{br} with a break frequency {ν }{br}˜ 1 GHz if the duration of electron acceleration is ˜60-80 Myr. However, the abrupt increase in the spectral index above ˜1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with {γ }{{e}}≳ {10}4.

Implementation of an Ultra-Bright Thermographic Phosphor for Gas Turbine Engine Temperature Measurements

NASA Technical Reports Server (NTRS)

Eldridge, Jeffrey I.; Bencic, Timothy J.; Zhu, Dongming; Cuy, Michael D.; Wolfe, Douglas E.; Allison, Stephen W.; Beshears, David L.; Jenkins, Thomas P.; Heeg, Bauke; Howard, Robert P.;

Variations in Surface Texture of the North Polar Residual Cap of Mars

NASA Technical Reports Server (NTRS)

Milkovich, S. M.; Byrne, S.; Russell, P. S.

2011-01-01

The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters. This roughness manifests as a series of bright mounds and dark hollows in visible images; these bright and dark patches have a characteristic wavelength and orientation. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material a result potentially at odds with impact crater statistics, which suggest ongoing deposition over the past 10-20 Kyr.

Estimation of surface temperature in remote pollution measurement experiments

NASA Technical Reports Server (NTRS)

Gupta, S. K.; Tiwari, S. N.

1978-01-01

A simple algorithm has been developed for estimating the actual surface temperature by applying corrections to the effective brightness temperature measured by radiometers mounted on remote sensing platforms. Corrections to effective brightness temperature are computed using an accurate radiative transfer model for the 'basic atmosphere' and several modifications of this caused by deviations of the various atmospheric and surface parameters from their base model values. Model calculations are employed to establish simple analytical relations between the deviations of these parameters and the additional temperature corrections required to compensate for them. Effects of simultaneous variation of two parameters are also examined. Use of these analytical relations instead of detailed radiative transfer calculations for routine data analysis results in a severalfold reduction in computation costs.

Galaxy evolution by color-log(n) type since redshift unity in the Hubble Ultra Deep Field

NASA Astrophysics Data System (ADS)

Cameron, E.; Driver, S. P.

2009-01-01

Aims: We explore the use of the color-log(n) (where n is the global Sérsic index) plane as a tool for subdividing the galaxy population in a physically-motivated manner out to redshift unity. We thereby aim to quantify surface brightness evolution by color-log(n) type, accounting separately for the specific selection and measurement biases against each. Methods: We construct (u-r) color-log(n) diagrams for distant galaxies in the Hubble Ultra Deep Field (UDF) within a series of volume-limited samples to z=1.5. The color-log(n) distributions of these high redshift galaxies are compared against that measured for nearby galaxies in the Millennium Galaxy Catalogue (MGC), as well as to the results of visual morphological classification. Based on this analysis we divide our sample into three color-structure classes. Namely, “red, compact”, “blue, diffuse” and “blue, compact”. Luminosity-size diagrams are constructed for members of the two largest classes (“red, compact” and “blue, diffuse”), both in the UDF and the MGC. Artificial galaxy simulations (for systems with exponential and de Vaucouleurs profile shapes alternately) are used to identify “bias-free” regions of the luminosity-size plane in which galaxies are detected with high completeness, and their fluxes and sizes recovered with minimal surface brightness-dependent biases. Galaxy evolution is quantified via comparison of the low and high redshift luminosity-size relations within these “bias-free” regions. Results: We confirm the correlation between color-log(n) plane position and visual morphological type observed locally and in other high redshift studies in the color and/or structure domain. The combined effects of observational uncertainties, the morphological K-correction and cosmic variance preclude a robust statistical comparison of the shape of the MGC and UDF color-log(n) distributions. However, in the interval 0.75 < z <1.0 where the UDF i-band samples close to rest-frame B-band light (i.e., the morphological K-correction between our samples is negligible) we are able to present tentative evidence of bimodality, albiet for a very small sample size (17 galaxies). Our unique approach to quantifying selection and measurement biases in the luminosity-size plane highlights the need to consider errors in the recovery of both magnitudes and sizes, and their dependence on profile shape. Motivated by these results we divide our sample into the three color-structure classes mentioned above and quantify luminosity-size evolution by galaxy type. Specifically, we detect decreases in B-band, surface brightness of 1.57 ± 0.22 mag arcsec-2 and 1.65 ± 0.22 mag arcsec-2 for our “blue, diffuse” and “red, compact” classes respectively between redshift unity and the present day.

Cosmic gamma-ray bursts from BATSE - Another great debate

NASA Technical Reports Server (NTRS)

Hartmann, Dieter H.; The, Lih-Sin; Clayton, Donald D.; Schnepf, Neil G.; Linder, Eric V.

1992-01-01

The BATSE detectors aboard Compton Observatory record about one cosmic gamma-ray burst (GRB) per day. Preliminary data analysis shows a highly isotropic sky map and a nonuniform brightness distribution. Anisotropies expected from a Galactic neutron star population, the most frequently considered source model, did not emerge from the data. Taken at face value, the data seem to suggest a heliocentric solution of the GRB puzzle. The observed isotropy can be achieved if sources are either very near or extragalactic. Pop I neutron stars in the disk do not simultaneously fit sky and brightness distributions. A possibility are sources in an extended Galactic halo with scale length large enough to avoid strong anisotropies due to the solar offset from the Galactic center. If GRBs are located in an extended halo we ask whether the neutron star paradigm can survive. We show that the recently discovered high velocity radio pulsars may provide a natural source population for GRBs. If these pulsars formed in the halo, as suggested by the radio data, the possibility arises that GRBs and high velocity pulsars are two related phenomena that provide observational evidence of the dark Galactic corona. We also discuss cosmological redshift constraints that follow from the observed brightness distribution.

Solar corona during the 1994 and 1999 eclipses

NASA Astrophysics Data System (ADS)

Badalyan, O. G.; Sýkora, J.

2008-06-01

The lower and middle layers of the corona are studied analyzing the ground-based observations carried out during the November 3, 1994 and August 11, 1999 total solar eclipses. While the 1994 eclipse took place nearby the solar activity minimum, the 1999 eclipse occurred closer to the solar cycle maximum. Structures, isolines of brightness and polarization, and topology of the magnetic field lines of force (calculated under a potential approximation) of these two coronae are mutually compared. It is confirmed that the brightness distribution in the corona corresponds to the hydrostatic distribution of density at the distances 1.2-1.8R⊙. Temperature 1.4 MK and density n0 = 3.3 × 108cm-3 are found for the equatorial coronal regions of the 1999 corona. Physical conditions in the polar coronal regions are investigated analyzing the brightness and polarization of the 1994 eclipse. We have found that the degree of polarization in polar plumes is about 10% higher than that in the inter-plumes space. Consideration of the brightness in plumes and in the adjacent background space allowed us to conclude that the temperatures there are close to 1 MK. The density in the individual plumes is near n0 = 2.7 × 108cm-3, while it decreases to about n0 = 2.0 × 108cm-3 in the inter-plumes space. It is pointed out that the simultaneous interpretation of the measured brightness and polarization struggles with some difficulties.

Predicting Cortical Dark/Bright Asymmetries from Natural Image Statistics and Early Visual Transforms

PubMed Central

Cooper, Emily A.; Norcia, Anthony M.

2015-01-01

The nervous system has evolved in an environment with structure and predictability. One of the ubiquitous principles of sensory systems is the creation of circuits that capitalize on this predictability. Previous work has identified predictable non-uniformities in the distributions of basic visual features in natural images that are relevant to the encoding tasks of the visual system. Here, we report that the well-established statistical distributions of visual features -- such as visual contrast, spatial scale, and depth -- differ between bright and dark image components. Following this analysis, we go on to trace how these differences in natural images translate into different patterns of cortical input that arise from the separate bright (ON) and dark (OFF) pathways originating in the retina. We use models of these early visual pathways to transform natural images into statistical patterns of cortical input. The models include the receptive fields and non-linear response properties of the magnocellular (M) and parvocellular (P) pathways, with their ON and OFF pathway divisions. The results indicate that there are regularities in visual cortical input beyond those that have previously been appreciated from the direct analysis of natural images. In particular, several dark/bright asymmetries provide a potential account for recently discovered asymmetries in how the brain processes visual features, such as violations of classic energy-type models. On the basis of our analysis, we expect that the dark/bright dichotomy in natural images plays a key role in the generation of both cortical and perceptual asymmetries. PMID:26020624

The influence of thermal inertia on temperatures and frost stability on Triton

NASA Technical Reports Server (NTRS)

Spencer, John R.; Moore, Jeffrey M.

1992-01-01

It is presently argued, in view of (1) a thermal inertia model for the surface of Triton which (like previous ones) predicts a monotonic recession of permanent N2 deposits toward the poles and very little seasonal N2 frost in the southern hemisphere, and (2) new spectroscopic evidence for nonvolatile CO2 on Triton's bright southern hemisphere, that much of that bright southern material is not N2. Such bright southern hemisphere volatiles may allow the formation of seasonal frosts, thereby helping to explain the observed spectroscopic changes of Triton during the last decade.

GHOSTS IN THE ATTIC: MAPPING THE STELLAR CONTENT OF THE S0 GALAXY NGC 5102

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidge, T. J.

2010-02-15

The spatial distribution of stars in the nearby S0 galaxy NGC 5102 is investigated using images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope. With the exception of gaps between detector elements, the entire galaxy is surveyed in r' and i', while the J and Ks data extend out to R {sub GC} {approx} 6 kpc, which corresponds to almost 7 disk scale lengths. A modest population of main-sequence stars with M{sub V} < -3.5 and ages {approx}70 Myr are detected throughout the disk, with the majority located in the southern half of the galaxy. The stellar disk inmore » the northern half of the galaxy is warped, following structure that is also seen in H I. Objects with photometric properties that are consistent with those of bright asymptotic giant branch (AGB) stars are seen throughout the disk, and the ratio of C stars to bright M giants is consistent with an overall increase in the star formation rate within the past 1 Gyr. Star-forming activity during the interval 0.1-2 Gyr was more centrally concentrated than during the past {approx}100 Myr. The structure of the disk changes near R {sub GC} {approx} 5 kpc (5.5 disk scale lengths), in the sense that the radial surface density profile defined by red supergiants (RSGs) and bright AGB stars levels off at larger radii. RSGs and bright AGB stars are traced out to a radius of 14 kpc (15.6 scale lengths) along the southern portion of the major axis, while a tentative detection is also made of bright AGB stars at a projected distance of {approx}16 kpc along the southeast minor axis. A large clump of AGB stars that subtends {approx}1 arcmin is identified to the west of the galaxy center. It is argued that this is the remnant of a companion galaxy that triggered past episodes of elevated star-forming activity.« less

Spectral and Spatial Analysis of Volatile Deposits in Io's Loki Patera

NASA Astrophysics Data System (ADS)

Landis, C. E.; Howell, R. R.

2012-12-01

Loki Patera is an active volcanic feature approximately 200 km in diameter on Jupiter's moon Io. The goals of this research are to better understand the nature of volatile distribution in and around the Loki region. Images taken by Voyager I show a number of bright features distributed across the patera surface. These features, referred to as "bergs," may be fumaroles which allow sulfur gases from the lava beneath the hardened crust to escape onto the surface. By examining the spatial distribution of the bergs and the spectral signatures of bergs and other features around Loki Patera, we can better understand their role in the volcanic activity observed at Loki, and perhaps elsewhere on Io. Spectral data from the Voyager and Galileo missions were examined using ISIS3, a program suite developed by the USGS. Photometric corrections were applied to the images to adjust for changes in lighting geometry. The spatial distribution of the bergs was examined using ArcMap. Initial results indicate that the bergs seldom occur near the inner and outer edges of the patera, which are known to be hotter than other parts of the patera. The lack of bergs in this area suggests that thermal properties of the crust may control the distribution of the bergs. The spacing of the bergs, which on average are about 6 km from each other, and other distribution statistics are used to test whether there is some maximum area of crust in which one berg can accommodate the escaping gases. The spectral signatures of the bergs themselves are compared to other surface features in and around the patera. Further study of the bergs and other features will continue to shed light on the underlying geologic and volcanic processes responsible for the activity at Loki. This work was supported in part by NASA JDAP grant NNX09AE06G.

Snow stratigraphic heterogeneity within ground-based passive microwave radiometer footprints: implications for emission modelling

NASA Astrophysics Data System (ADS)

Sandells, M.; Rutter, N.; Derksen, C.; Langlois, A.; Lemmetyinen, J.; Montpetit, B.; Pulliainen, J. T.; Royer, A.; Toose, P.

2012-12-01

Remote sensing of snow mass remains a challenging area of research. Scattering of electromagnetic radiation is sensitive to snow mass, but is also affected by contrasts in the dielectric properties of the snow. Although the argument that errors from simple algorithms average out at large scales has been used to justify current retrieval methods, it is not obvious why this should be the case. This hypothesis needs to be tested more rigorously. A ground-based field experiment was carried out to assess the impact of sub-footprint snow heterogeneity on microwave brightness temperature, in Churchill, Canada in winter in early 2010. Passive microwave measurements of snow were made using sled-mounted radiometers at 75cm intervals over a 5m transect. Measurements were made at horizontal and vertical polarizations at frequencies of 19 and 37 GHz. Snow beneath the radiometer footprints was subsequently excavated, creating a snow trench wall along the centrepoints of adjacent footprints. The trench wall was carefully smoothed and photographed with a near-infrared camera in order to determine the positions of stratigraphic snow layer boundaries. Three one-dimensional vertical profiles of snowpack properties (density and snow specific surface area) were taken at 75cm, 185cm and 355cm from the left hand side of the trench. These profile measurements were used to derive snow density and grain size for each of the layers identified from the NIR image. Microwave brightness temperatures for the 2-dimensional map of snow properties was simulated with the Helsinki University of Technology (HUT) model at 1cm intervals horizontally across the trench. Where each of five ice lenses was identified in the snow stratigraphy, a decrease in brightness temperature was simulated. However, the median brightness temperature simulated across the trench was substantially higher than the observations, of the order of tens of Kelvin, dependent on frequency and polarization. In order to understand and quantify possible sources of error in the simulations, a number of experiments were carried out to investigate the sensitivity of the brightness temperature to: 1) uncertainties in field observations, 2) representation of ice lenses, 3) model layering structure, and 4) near-infrared derived grain size representing snow grain size at microwave wavelengths. Field measurement error made little difference to the simulated brightness temperature, nor did the representation of ice lenses as crusts of high density snow. As the number of layers in the snow was reduced to 3, 2, or 1, the simulated brightness temperature increased slightly. However, scaling of snow grain size had a dramatic effect on the simulated brightness temperatures, reducing the median bias of the simulations to within measurement error for the statistically different brightness temperature distributions. This indicated that further investigation is required to define what is meant by the microwave grain size, and how this relates to the grain size that is used in the microwave emission model.

A portable inspection system to estimate direct glare of various LED modules

NASA Astrophysics Data System (ADS)

Chen, Po-Li; Liao, Chun-Hsiang; Li, Hung-Chung; Jou, Shyh-Jye; Chen, Han-Ting; Lin, Yu-Hsin; Tang, Yu-Hsiang; Peng, Wei-Jei; Kuo, Hui-Jean; Sun, Pei-Li; Lee, Tsung-Xian

2015-07-01

Glare is caused by both direct and indirect light sources and discomfort glare produces visual discomfort, annoyance, or loss in visual performance and visibility. Direct glare is caused by light sources in the field of view whereas reflected glare is caused by bright reflections from polished or glossy surfaces that are reflected toward an individual. To improve visual comfort of our living environment, a portable inspection system to estimate direct glare of various commercial LED modules with the range of color temperature from 3100 K to 5300 K was developed in this study. The system utilized HDR images to obtain the illumination distribution of LED modules and was first calibrated for brightness and chromaticity and corrected with flat field, dark-corner and curvature by the installed algorithm. The index of direct glare was then automatically estimated after image capturing, and the operator can recognize the performance of LED modules and the possible effects on human being once the index was out of expecting range. In the future, we expect that the quick-response smart inspection system can be applied in several new fields and market, such as home energy diagnostics, environmental lighting and UGR monitoring and popularize it in several new fields.

Design of LED fish lighting attractors using horizontal/vertical LIDC mapping method.

PubMed

Shen, S C; Huang, H J

2012-11-19

This study employs a sub-module concept to develop high-brightness light-emitting diode (HB-LED) fishing light arrays to replace traditional fishing light attractors. The horizontal/vertical (H/V) plane light intensity distribution curve (LIDC) of a LED light source are mapped to assist in the design of a non-axisymmetric lens with a fish-attracting light pattern that illuminates sufficiently large areas and alternates between bright and dark. These LED fishing light attractors are capable of attracting schools of fish toward the perimeter of the luminous zone surrounding fishing boats. Three CT2 boats (10 to 20 ton capacity) were recruited to conduct a field test for 1 y on the sea off the southwestern coast of Taiwan. Field tests show that HB-LED fishing light array installed 5 m above the boat deck illuminated a sea surface of 5 × 12 m and achieved an illuminance of 2000 lx. The test results show that the HB-LED fishing light arrays increased the mean catch of the three boats by 5% to 27%. In addition, the experimental boats consumed 15% to 17% less fuel than their counterparts.

Micromachined edge illuminated optically transparent automotive light guide panels

NASA Astrophysics Data System (ADS)

Ronny, Rahima Afrose; Knopf, George K.; Bordatchev, Evgueni; Tauhiduzzaman, Mohammed; Nikumb, Suwas

2012-03-01

Edge-lit backlighting has been used extensively for a variety of small and medium-sized liquid crystal displays (LCDs). The shape, density and spatial distribution pattern of the micro-optical elements imprinted on the surface of the flat light-guide panel (LGP) are often "optimized" to improve the overall brightness and luminance uniformity. A similar concept can be used to develop interior convenience lighting panels and exterior tail lamps for automotive applications. However, costly diffusive sheeting and brightness enhancement films are not be considered for these applications because absolute luminance uniformity and the minimization of Moiré fringe effects are not significant factors in assessing quality of automotive lighting. A new design concept that involves micromilling cylindrical micro-optical elements on optically transparent plastic substrates is described in this paper. The variable parameter that controls illumination over the active regions of the panel is the depth of the individual cylindrical micro-optical elements. LightTools™ is the optical simulation tool used to explore how changing the micro-optical element depth can alter the local and global luminance. Numerical simulation and microfabrication experiments are performed on several (100mmx100mmx6mm) polymethylmethacrylate (PMMA) test samples in order to verify the illumination behavior.

Gravity waves generated by a tropical cyclone during the STEP tropical field program - A case study

NASA Technical Reports Server (NTRS)

Pfister, L.; Chan, K. R.; Bui, T. P.; Bowen, S.; Legg, M.; Gary, B.; Kelly, K.; Proffitt, M.; Starr, W.

1993-01-01

Overflights of a tropical cyclone during the Australian winter monsoon field experiment of the Stratosphere-Troposphere Exchange Project (STEP) show the presence of two mesoscale phenomena: a vertically propagating gravity wave with a horizontal wavelength of about 110 km and a feature with a horizontal scale comparable to that of the cyclone's entire cloud shield. The larger feature is fairly steady, though its physical interpretation is ambiguous. The 110-km gravity wave is transient, having maximum amplitude early in the flight and decreasing in amplitude thereafter. Its scale is comparable to that of 100-to 150-km-diameter cells of low satellite brightness temperatures within the overall cyclone cloud shield; these cells have lifetimes of 4.5 to 6 hrs. These cells correspond to regions of enhanced convection, higher cloud altitude, and upwardly displaced potential temperature surfaces. The temporal and spatial distribution of meteorological variables associated with the 110-km gravity wave can be simulated by a slowly moving transient forcing at the anvil top having an amplitude of 400-600 m, a lifetime of 4.5-6 hrs, and a size comparable to the cells of low brightness temperature.

The Dragonfly Nearby Galaxies Survey. IV. A Giant Stellar Disk in NGC 2841

NASA Astrophysics Data System (ADS)

Zhang, Jielai; Abraham, Roberto; van Dokkum, Pieter; Merritt, Allison; Janssens, Steven

2018-03-01

Neutral gas is commonly believed to dominate over stars in the outskirts of galaxies, and investigations of the disk-halo interface are generally considered to be in the domain of radio astronomy. This may simply be a consequence of the fact that deep H I observations typically probe to a lower-mass surface density than visible wavelength data. This paper presents low-surface-brightness, optimized visible wavelength observations of the extreme outskirts of the nearby spiral galaxy NGC 2841. We report the discovery of an enormous low-surface brightness stellar disk in this object. When azimuthally averaged, the stellar disk can be traced out to a radius of ∼70 kpc (5 R 25 or 23 inner disk scale lengths). The structure in the stellar disk traces the morphology of H I emission and extended UV emission. Contrary to expectations, the stellar mass surface density does not fall below that of the gas mass surface density at any radius. In fact, at all radii greater than ∼20 kpc, the ratio of the stellar mass to gas mass surface density is a constant 3:1. Beyond ∼30 kpc, the low-surface-brightness stellar disk begins to warp, which may be an indication of a physical connection between the outskirts of the galaxy and infall from the circumgalactic medium. A combination of stellar migration, accretion, and in situ star formation might be responsible for building up the outer stellar disk, but whatever mechanisms formed the outer disk must also explain the constant ratio between stellar and gas mass in the outskirts of this galaxy.

VizieR Online Data Catalog: FIR data of IR-bright dust-obscured galaxies (DOGs) (Toba+, 2017)

NASA Astrophysics Data System (ADS)

Toba, Y.; Nagao, T.; Wang, W.-H.; Matsuhara, H.; Akiyama, M.; Goto, T.; Koyama, Y.; Ohyama, Y.; Yamamura, I.

2017-11-01

We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, (i-[22])AB>7.0. Combining an IR-bright DOG sample with the flux at 22μm>3.8mJy discovered by Toba & Nagao (2016ApJ...820...46T) with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07

Far-infrared Properties of Infrared-bright Dust-obscured Galaxies Selected with IRAS and AKARI Far-infrared All-sky Survey

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Nagao, Tohru; Wang, Wei-Hao; Matsuhara, Hideo; Akiyama, Masayuki; Goto, Tomotsugu; Koyama, Yusei; Ohyama, Youich; Yamamura, Issei

2017-05-01

We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, {(I-[22])}{AB}> 7.0. Combining an IR-bright DOG sample with the flux at 22 μm > 3.8 mJy discovered by Toba & Nagao with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07< z< 1.0) that were obtained from the literature, we estimated their IR luminosity, star formation rate (SFR), and stellar mass based on the spectral energy distribution fitting. We found that (1) the WISE 22 μm luminosity at the observed frame is a good indicator of IR luminosity for IR-bright DOGs and (2) the contribution of the active galactic nucleus to IR luminosity increases with IR luminosity. By comparing the stellar mass and SFR relation for our DOG sample and the literature, we found that most of the IR-bright DOGs lie significantly above the main sequence of star-forming galaxies at similar redshift, indicating that the majority of IRAS- or AKARI-detected IR-bright DOGs are starburst galaxies.

Normal dimensions of the posterior pituitary bright spot on magnetic resonance imaging.

PubMed

Côté, Martin; Salzman, Karen L; Sorour, Mohammad; Couldwell, William T

2014-02-01

The normal pituitary bright spot seen on unenhanced T1-weighted MRI is thought to result from the T1-shortening effect of the vasopressin stored in the posterior pituitary. Individual variations in its size may be difficult to differentiate from pathological conditions resulting in either absence of the pituitary bright spot or in T1-hyperintense lesions of the sella. The objective of this paper was to define a range of normal dimensions of the pituitary bright spot and to illustrate some of the most commonly encountered pathologies that result in absence or enlargement of the pituitary bright spot. The authors selected normal pituitary MRI studies from 106 patients with no pituitary abnormality. The size of each pituitary bright spot was measured in the longest axis and in the dimension perpendicular to this axis to describe the typical dimensions. The authors also present cases of patients with pituitary abnormalities to highlight the differences and potential overlap between normal and pathological pituitary imaging. All of the studies evaluated were found to have pituitary bright spots, and the mean dimensions were 4.8 mm in the long axis and 2.4 mm in the short axis. The dimension of the pituitary bright spot in the long axis decreased with patient age. The distribution of dimensions of the pituitary bright spot was normal, indicating that 99.7% of patients should have a pituitary bright spot measuring between 1.2 and 8.5 mm in its long axis and between 0.4 and 4.4 mm in its short axis, an interval corresponding to 3 standard deviations below and above the mean. In cases where the dimension of the pituitary bright spot is outside this range, pathological conditions should be considered. The pituitary bright spot should always be demonstrated on T1-weighted MRI, and its dimensions should be within the identified normal range in most patients. Outside of this range, pathological conditions affecting the pituitary bright spot should be considered.

The dust scattering halo of Cygnus X-3

NASA Astrophysics Data System (ADS)

Corrales, L. R.; Paerels, F.

2015-10-01

Dust grains scatter X-ray light through small angles, producing a diffuse halo image around bright X-ray point sources situated behind a large amount of interstellar material. We present analytic solutions to the integral for the dust scattering intensity, which allow for a Bayesian analysis of the scattering halo around Cygnus X-3. Fitting the optically thin 4-6 keV halo surface brightness profile yields the dust grain size and spatial distribution. We assume a power-law distribution of grain sizes (n ∝ a-p) and fit for p, the grain radius cut-off amax, and dust mass column. We find that a p ≈ 3.5 dust grain size distribution with amax ≈ 0.2 μm fits the halo profile relatively well, whether the dust is distributed uniformly along the line of sight or in clumps. We find that a model consisting of two dust screens, representative of foreground spiral arms, requires the foreground Perseus arm to contain 80 per cent of the total dust mass. The remaining 20 per cent of the dust, which may be associated with the outer spiral arm of the Milky Way, is located within 1 kpc of Cyg X-3. Regardless of which model was used, we found τ_sca ˜ 2 E_keV^{-2}. We examine the energy resolved haloes of Cyg X-3 from 1 to 6 keV and find that there is a sharp drop in scattering halo intensity when E < 2-3 keV, which cannot be explained with multiple scattering effects. We hypothesize that this may be caused by large dust grains or material with unique dielectric properties, causing the scattering cross-section to depart from the Rayleigh-Gans approximation that is used most often in X-ray scattering studies. The foreground Cyg OB2 association, which contains several evolved stars with large extinction values, is a likely culprit for grains of unique size or composition.

Extragalactic background light: a measurement at 400 nm using dark cloud shadow*†- I. Low surface brightness spectrophotometry in the area of Lynds 1642

NASA Astrophysics Data System (ADS)

Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch.

2017-09-01

We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at λ = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV ≳ 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of ≲ 0.5 × 10-9 erg cm-2 s-1 sr-1 Å-1 as required to measure an EBL intensity in range of ˜1 to a few times 10-9 erg cm-2 s-1 sr-1 Å-1. Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.

Surface brightness profiles and structural parameters for 53 rich stellar clusters in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Mackey, A. D.; Gilmore, G. F.

2003-01-01

We have compiled a pseudo-snapshot data set of two-colour observations from the Hubble Space Telescope archive for a sample of 53 rich LMC clusters with ages of 106-1010 yr. We present surface brightness profiles for the entire sample, and derive structural parameters for each cluster, including core radii, and luminosity and mass estimates. Because we expect the results presented here to form the basis for several further projects, we describe in detail the data reduction and surface brightness profile construction processes, and compare our results with those of previous ground-based studies. The surface brightness profiles show a large amount of detail, including irregularities in the profiles of young clusters (such as bumps, dips and sharp shoulders), and evidence for both double clusters and post-core-collapse (PCC) clusters. In particular, we find power-law profiles in the inner regions of several candidate PCC clusters, with slopes of approximately -0.7, but showing considerable variation. We estimate that 20 +/- 7 per cent of the old cluster population of the Large Magellanic Cloud (LMC) has entered PCC evolution, a similar fraction to that for the Galactic globular cluster system. In addition, we examine the profile of R136 in detail and show that it is probably not a PCC cluster. We also observe a trend in core radius with age that has been discovered and discussed in several previous publications by different authors. Our diagram has better resolution, however, and appears to show a bifurcation at several hundred Myr. We argue that this observed relationship reflects true physical evolution in LMC clusters, with some experiencing small-scale core expansion owing to mass loss, and others large-scale expansion owing to some unidentified characteristic or physical process.

Galaxy And Mass Assembly (GAMA): detection of low-surface-brightness galaxies from SDSS data

NASA Astrophysics Data System (ADS)

Williams, Richard P.; Baldry, I. K.; Kelvin, L. S.; James, P. A.; Driver, S. P.; Prescott, M.; Brough, S.; Brown, M. J. I.; Davies, L. J. M.; Holwerda, B. W.; Liske, J.; Norberg, P.; Moffett, A. J.; Wright, A. H.

2016-12-01

We report on a search for new low-surface-brightness galaxies (LSBGs) using Sloan Digital Sky Survey (SDSS) data within the Galaxy And Mass Assembly (GAMA) equatorial fields. The search method consisted of masking objects detected with SDSS PHOTO, combining gri images weighted to maximize the expected signal-to-noise ratio, and smoothing the images. The processed images were then run through a detection algorithm that finds all pixels above a set threshold and groups them based on their proximity to one another. The list of detections was cleaned of contaminants such as diffraction spikes and the faint wings of masked objects. From these, selecting potentially the brightest in terms of total flux, a list of 343 LSBGs was produced having been confirmed using VISTA Kilo-degree Infrared Galaxy Survey (VIKING) imaging. The photometry of this sample was refined using the deeper VIKING Z band as the aperture-defining band. Measuring their g - I and J - K colours shows that most are consistent with being at redshifts less than 0.2. The photometry is carried out using an AUTO aperture for each detection giving surface brightnesses of μr ≳ 25 mag arcsec-2 and magnitudes of r > 19.8 mag. None of these galaxies are bright enough to be within the GAMA main survey limit but could be part of future deeper surveys to measure the low-mass end of the galaxy stellar mass function.

Surface Modification and Surface - Subsurface Exchange Processes on Europa

NASA Astrophysics Data System (ADS)

Phillips, Cynthia B.; Molaro, Jamie; Hand, Kevin P.

2017-10-01

The surface of Jupiter’s moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa’s leading-trailing hemisphere brightness asymmetry.Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted “chaos-type” terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features.In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa’s surface area.Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age (~50myr) of Europa. Quantifying the timescale and volume of transported material will yield insight on whether such a process may provide fuel to sustain a biosphere in Europa’s subsurface ocean, which is relevant to searches for life by a future mission such as a potential Europa Lander.

Surface Modification and Surface - Subsurface Exchange Processes on Europa

NASA Astrophysics Data System (ADS)

Phillips, C. B.; Molaro, J.; Hand, K. P.

2017-12-01

The surface of Jupiter's moon Europa is modified by exogenic processes such as sputtering, gardening, radiolysis, sulfur ion implantation, and thermal processing, as well as endogenic processes including tidal shaking, mass wasting, and the effects of subsurface tectonic and perhaps cryovolcanic activity. New materials are created or deposited on the surface (radiolysis, micrometeorite impacts, sulfur ion implantation, cryovolcanic plume deposits), modified in place (thermal segregation, sintering), transported either vertically or horizontally (sputtering, gardening, mass wasting, tectonic and cryovolcanic activity), or lost from Europa completely (sputtering, plumes, larger impacts). Some of these processes vary spatially, as visible in Europa's leading-trailing hemisphere brightness asymmetry. Endogenic geologic processes also vary spatially, depending on terrain type. The surface can be classified into general landform categories that include tectonic features (ridges, bands, cracks); disrupted "chaos-type" terrain (chaos blocks, matrix, domes, pits, spots); and impact craters (simple, complex, multi-ring). The spatial distribution of these terrain types is relatively random, with some differences in apex-antiapex cratering rates and latitudinal variation in chaos vs. tectonic features. In this work, we extrapolate surface processes and rates from the top meter of the surface in conjunction with global estimates of transport and resurfacing rates. We combine near-surface modification with an estimate of surface-subsurface (and vice versa) transport rates for various geologic terrains based on an average of proposed formation mechanisms, and a spatial distribution of each landform type over Europa's surface area. Understanding the rates and mass balance for each of these processes, as well as their spatial and temporal variability, allows us to estimate surface - subsurface exchange rates over the average surface age ( 50myr) of Europa. Quantifying the timescale and volume of transported material will yield insight on whether such a process may provide fuel to sustain a biosphere in Europa's subsurface ocean, which is relevant to searches for life by a future mission such as a potential Europa Lander.

Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe.

PubMed

Zhang, Zhi-Yu; Papadopoulos, Padelis P; Ivison, R J; Galametz, Maud; Smith, M W L; Xilouris, Emmanuel M

2016-06-01

Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H2 gas velocity fields and enclosed H2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh-Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB.

Innovative Facet Passivation for High-Brightness Laser Diodes

DTIC Science & Technology

2016-02-05

and anti-reflection (AR) coatings are deposited after cleaving. Edge- emitting laser diodes emit very high optical powers from small emission areas, as...SECURITY CLASSIFICATION OF: The objective of this effort is to increase the power of low fill-factor (20%) laser diode (LD) bars from the present...2012 16-Nov-2015 Approved for Public Release; Distribution Unlimited Final Report: Innovative Facet Passivation for High-Brightness Laser Diodes The

Automated Adaptive Brightness in Wireless Capsule Endoscopy Using Image Segmentation and Sigmoid Function.

PubMed

Shrestha, Ravi; Mohammed, Shahed K; Hasan, Md Mehedi; Zhang, Xuechao; Wahid, Khan A

2016-08-01

Wireless capsule endoscopy (WCE) plays an important role in the diagnosis of gastrointestinal (GI) diseases by capturing images of human small intestine. Accurate diagnosis of endoscopic images depends heavily on the quality of captured images. Along with image and frame rate, brightness of the image is an important parameter that influences the image quality which leads to the design of an efficient illumination system. Such design involves the choice and placement of proper light source and its ability to illuminate GI surface with proper brightness. Light emitting diodes (LEDs) are normally used as sources where modulated pulses are used to control LED's brightness. In practice, instances like under- and over-illumination are very common in WCE, where the former provides dark images and the later provides bright images with high power consumption. In this paper, we propose a low-power and efficient illumination system that is based on an automated brightness algorithm. The scheme is adaptive in nature, i.e., the brightness level is controlled automatically in real-time while the images are being captured. The captured images are segmented into four equal regions and the brightness level of each region is calculated. Then an adaptive sigmoid function is used to find the optimized brightness level and accordingly a new value of duty cycle of the modulated pulse is generated to capture future images. The algorithm is fully implemented in a capsule prototype and tested with endoscopic images. Commercial capsules like Pillcam and Mirocam were also used in the experiment. The results show that the proposed algorithm works well in controlling the brightness level accordingly to the environmental condition, and as a result, good quality images are captured with an average of 40% brightness level that saves power consumption of the capsule.

Exploration of an Ancient Ocean World: Dawn at Ceres

NASA Astrophysics Data System (ADS)

Raymond, C. A.

2016-12-01

The Dawn mission completed its comprehensive mapping of Ceres, the only dwarf planet in the inner solar system, earlier this year and has since begun an extended mission to improve the quality of the data sets and test specific hypotheses. Prior to Dawn's arrival, Ceres was already known to be a dark, wet dwarf planet with evidence for altered minerals and water vapor emissions, from decades of ground- and space-based observations. Dawn arrived at Ceres in March of 2015 and found a very dark surface as expected, but unexpectedly found a heavily cratered surface that was punctuated by small extremely bright areas. Contrary to the prediction by pre-Dawn models of an ice-rich, viscously-relaxed smooth surface resulting from physical differentiation and freezing of an ancient subsurface ocean, its surface has many craters, implying a mechanically strong thick crust. Ceres is, however, missing the largest expected craters and is gravitationally relaxed at long wavelengths, implying that the strong crust overlies a weaker deep interior. This presented a challenge to the pre-Dawn differentiation model, but data were available to test it. Ceres' surface is dominated by dark material, phyllosilicates, ammoniated clays and carbonates. The ubiquitous presence of ammoniated minerals suggests formation in a colder environment, possibly in the outer solar system, while the distribution of minerals indicates that Ceres' interior experienced pervasive alteration. Water ice has been observed in fresh craters at high latitudes, and elemental measurements indicate the presence of water ice in the immediate subsurface. These observations, along with Ceres gravity field confirm that Ceres at least partially differentiated, releasing water and volatiles from the original chondritic material, and providing evidence for an ancient subsurface ocean. Evidence for past and continuing geologic activity on Ceres is found in the regional variations in topography and morphology of the surface. Smoother, apparently resurfaced areas are generally found at lower elevations and rougher areas have greater relief. Local morphology such as crater floor deposits, isolated mountains and the enigmatic bright areas indicate active processes on Ceres that likely involve brine-driven cryovolcanism.

In-depth Analysis of Land Surface Emissivity using Microwave Polarization Difference Index to Improve Satellite QPE

NASA Astrophysics Data System (ADS)

Zheng, Y.; Kirstetter, P. E.; Hong, Y.; Wen, Y.; Turk, J.; Gourley, J. J.

2015-12-01

One of primary uncertainties in satellite overland quantitative precipitation estimates (QPE) from passive sensors such as radiometers is the impact on the brightness temperatures by the surface land emissivity. The complexity of surface land emissivity is linked to its temporal variations (diurnal and seasonal) and spatial variations (subsurface vertical profiles of soil moisture, vegetation structure and surface temperature) translating into sub-pixel heterogeneity within the satellite field of view (FOV). To better extract the useful signal from hydrometeors, surface land emissivity needs to be determined and filtered from the satellite-measured brightness temperatures. Based on the dielectric properties of surface land cover constitutes, Microwave Polarization Differential index (MPDI) is expected to carry the composite effect of surface land properties on land surface emissivity, with a higher MPDI indicating a lower emissivity. This study analyses the dependence of MPDI to soil moisture, vegetation and surface skin temperature over 9 different land surface types. Such analysis is performed using the normalized difference vegetation index (NDVI) from MODIS, the near surface air temperature from the RAP model and ante-precedent precipitation accumulation from the Multi-Radar Multi-Sensor as surrogates for the vegetation, surface skin temperature and shallow layer soil moisture, respectively. This paper provides 1) evaluations of brightness temperature-based MPDI from the TRMM and GPM Microwave Imagers in both raining and non-raining conditions to test the dependence of MPDI to precipitation; 2) comparisons of MPDI categorized into instantly before, during and immediately after selected precipitation events to examine the impact of modest-to-heavy precipitation on the spatial pattern of MPDI; 3) inspections of relationship between MPDI versus rain fraction and rain rate within the satellite sensors FOV to investigate the behaviors of MPDI in varying precipitation conditions; 4) analysis of discrepancies of MPDI over 10.65, 19.35, 37 and 85.8 GHz to identify the sensitivity of MPDS to microwave wavelengths.

Radial distribution of dust, stars, gas, and star-formation rate in DustPedia⋆ face-on galaxies

NASA Astrophysics Data System (ADS)

Casasola, V.; Cassarà, L. P.; Bianchi, S.; Verstocken, S.; Xilouris, E.; Magrini, L.; Smith, M. W. L.; De Looze, I.; Galametz, M.; Madden, S. C.; Baes, M.; Clark, C.; Davies, J.; De Vis, P.; Evans, R.; Fritz, J.; Galliano, F.; Jones, A. P.; Mosenkov, A. V.; Viaene, S.; Ysard, N.

2017-09-01

Aims: The purpose of this work is the characterization of the radial distribution of dust, stars, gas, and star-formation rate (SFR) in a sub-sample of 18 face-on spiral galaxies extracted from the DustPedia sample. Methods: This study is performed by exploiting the multi-wavelength DustPedia database, from ultraviolet (UV) to sub-millimeter bands, in addition to molecular (12CO) and atomic (Hi) gas maps and metallicity abundance information available in the literature. We fitted the surface-brightness profiles of the tracers of dust and stars, the mass surface-density profiles of dust, stars, molecular gas, and total gas, and the SFR surface-density profiles with an exponential curve and derived their scale-lengths. We also developed a method to solve for the CO-to-H2 conversion factor (αCO) per galaxy by using dust- and gas-mass profiles. Results: Although each galaxy has its own peculiar behavior, we identified a common trend of the exponential scale-lengths versus wavelength. On average, the scale-lengths normalized to the B-band 25 mag/arcsec2 radius decrease from UV to 70 μm, from 0.4 to 0.2, and then increase back up to 0.3 at 500 microns. The main result is that, on average, the dust-mass surface-density scale-length is about 1.8 times the stellar one derived from IRAC data and the 3.6 μm surface brightness, and close to that in the UV. We found a mild dependence of the scale-lengths on the Hubble stage T: the scale-lengths of the Herschel bands and the 3.6 μm scale-length tend to increase from earlier to later types, the scale-length at 70 μm tends to be smaller than that at longer sub-mm wavelength with ratios between longer sub-mm wavelengths and 70 μm that decrease with increasing T. The scale-length ratio of SFR and stars shows a weak increasing trend towards later types. Our αCO determinations are in the range (0.3-9) M⊙ pc-2 (K km s-1)-1, almost invariant by using a fixed dust-to-gas ratio mass (DGR) or a DGR depending on metallicity gradient. DustPedia is a project funded by the EU under the heading "Exploitation of space science and exploration data". It has the primary goal of exploiting existing data in the Herschel Space Observatory and Planck Telescope databases.

Theoretical overview and modeling of the sodium and potassium atmospheres of the moon

NASA Technical Reports Server (NTRS)

Smyth, William H.; Marconi, M. L.

1995-01-01

A general theoretical overview for the sources, sinks, gas-surface interactions, and transport dynamics of sodium and potassium in the exospheric atmosphere of the Moon is given. These four factors, which control the spatial distribution of these two alkali-group gases about the Moon, are incorporated in numerical models. The spatial nature and relative importance of the initial source atoms atmosphere (which must be nonthermal to explain observational data) and the ambient (ballistic hopping) atom atmosphere are examined. The transport dynamics, atmospheric structure, and lunar escape of the nonthermal source atoms are time variable with season of the year and lunar phase because of their dependence on the radiation acceleration experienced by sodium and potassium atoms as they resonantly scatter solar photons. The dynamic transport time of fully thermally accomodated ambient atoms along the surface because of solar radiation acceleration (only several percent of surface gravity) is larger than the photoionization lifetimes and hence unimportant in determining the local density, although for potassium the situation is borderline. The sodium model was applied to analyze sodium observations of the sunward brightness profiles acquired near last quarter by Potter & Morgan (1988b) extending from the surface to an altitude of 1200 km, and near first quarter by Mendillo, Baumgardner, & Flynn (1991), extending in altitude from approximately 1430 to approximately 7000 km. The observations at larger altitudes could be fitted only for source atoms having a velocity distribution with a tail that is mildly nonthermal (like an approximately 1000 K Maxwell-Boltzmann distribution). Solar wind sputtering appears to a be a viable source atom mechanism for the sodium observations with photon-simulated desorption also possible but highly uncertain, although micrometeoroid impact vaporization appears to have a source that is too small and too hot, with likely an incorrect angular distribution about the Moon.

Early science from the Pan-STARRS1 Optical Galaxy Survey (POGS): Maps of stellar mass and star formation rate surface density obtained from distributed-computing pixel-SED fitting

NASA Astrophysics Data System (ADS)

Thilker, David A.; Vinsen, K.; Galaxy Properties Key Project, PS1

2014-01-01

To measure resolved galactic physical properties unbiased by the mask of recent star formation and dust features, we are conducting a citizen-scientist enabled nearby galaxy survey based on the unprecedented optical (g,r,i,z,y) imaging from Pan-STARRS1 (PS1). The PS1 Optical Galaxy Survey (POGS) covers 3π steradians (75% of the sky), about twice the footprint of SDSS. Whenever possible we also incorporate ancillary multi-wavelength image data from the ultraviolet (GALEX) and infrared (WISE, Spitzer) spectral regimes. For each cataloged nearby galaxy with a reliable redshift estimate of z < 0.05 - 0.1 (dependent on donated CPU power), publicly-distributed computing is being harnessed to enable pixel-by-pixel spectral energy distribution (SED) fitting, which in turn provides maps of key physical parameters such as the local stellar mass surface density, crude star formation history, and dust attenuation. With pixel SED fitting output we will then constrain parametric models of galaxy structure in a more meaningful way than ordinarily achieved. In particular, we will fit multi-component (e.g. bulge, bar, disk) galaxy models directly to the distribution of stellar mass rather than surface brightness in a single band, which is often locally biased. We will also compute non-parametric measures of morphology such as concentration, asymmetry using the POGS stellar mass and SFR surface density images. We anticipate studying how galactic substructures evolve by comparing our results with simulations and against more distant imaging surveys, some of which which will also be processed in the POGS pipeline. The reliance of our survey on citizen-scientist volunteers provides a world-wide opportunity for education. We developed an interactive interface which highlights the science being produced by each volunteer’s own CPU cycles. The POGS project has already proven popular amongst the public, attracting about 5000 volunteers with nearly 12,000 participating computers, and is growing rapidly.

FIRST RESULTS FROM THE DRAGONFLY TELEPHOTO ARRAY: THE APPARENT LACK OF A STELLAR HALO IN THE MASSIVE SPIRAL GALAXY M101

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Dokkum, Pieter G.; Merritt, Allison; Abraham, Roberto

2014-02-20

We use a new telescope concept, the Dragonfly Telephoto Array, to study the low surface brightness outskirts of the spiral galaxy M101. The radial surface brightness profile is measured down to μ {sub g} ∼ 32 mag arcsec{sup –2}, a depth that approaches the sensitivity of star count studies in the Local Group. We convert surface brightness to surface mass density using the radial g – r color profile. The mass density profile shows no significant upturn at large radius and is well-approximated by a simple bulge + disk model out to R = 70 kpc, corresponding to 18 diskmore » scale lengths. Fitting a bulge + disk + halo model we find that the best-fitting halo mass M{sub halo}=1.7{sub −1.7}{sup +3.4}×10{sup 8} M {sub ☉}. The total stellar mass of M101 is M{sub tot,∗}=5.3{sub −1.3}{sup +1.7}×10{sup 10} M {sub ☉}, and we infer that the halo mass fraction f{sub halo}=M{sub halo}/M{sub tot,∗}=0.003{sub −0.003}{sup +0.006}. This mass fraction is lower than that of the Milky Way (f {sub halo} ∼ 0.02) and M31 (f {sub halo} ∼ 0.04). All three galaxies fall below the f {sub halo}-M {sub tot,} {sub *} relation predicted by recent cosmological simulations that trace the light of disrupted satellites, with M101's halo mass a factor of ∼10 below the median expectation. However, the predicted scatter in this relation is large, and more galaxies are needed to better quantify this possible tension with galaxy formation models. Dragonfly is well suited for this project: as integrated-light surface brightness is independent of distance, large numbers of galaxies can be studied in a uniform way.« less

Comparison of measured brightness temperatures from SMOS with modelled ones from ORCHIDEE and H-TESSEL over the Iberian Peninsula

NASA Astrophysics Data System (ADS)

Barella-Ortiz, Anaïs; Polcher, Jan; de Rosnay, Patricia; Piles, Maria; Gelati, Emiliano

2017-01-01

L-band radiometry is considered to be one of the most suitable techniques to estimate surface soil moisture (SSM) by means of remote sensing. Brightness temperatures are key in this process, as they are the main input in the retrieval algorithm which yields SSM estimates. The work exposed compares brightness temperatures measured by the SMOS mission to two different sets of modelled ones, over the Iberian Peninsula from 2010 to 2012. The two modelled sets were estimated using a radiative transfer model and state variables from two land-surface models: (i) ORCHIDEE and (ii) H-TESSEL. The radiative transfer model used is the CMEM. Measured and modelled brightness temperatures show a good agreement in their temporal evolution, but their spatial structures are not consistent. An empirical orthogonal function analysis of the brightness temperature's error identifies a dominant structure over the south-west of the Iberian Peninsula which evolves during the year and is maximum in autumn and winter. Hypotheses concerning forcing-induced biases and assumptions made in the radiative transfer model are analysed to explain this inconsistency, but no candidate is found to be responsible for the weak spatial correlations at the moment. Further hypotheses are proposed and will be explored in a forthcoming paper. The analysis of spatial inconsistencies between modelled and measured TBs is important, as these can affect the estimation of geophysical variables and TB assimilation in operational models, as well as result in misleading validation studies.

A new, bright and hard aluminum surface produced by anodization

NASA Astrophysics Data System (ADS)

Hou, Fengyan; Hu, Bo; Tay, See Leng; Wang, Yuxin; Xiong, Chao; Gao, Wei

2017-07-01

Anodized aluminum (Al) and Al alloys have a wide range of applications. However, certain anodized finishings have relatively low hardness, dull appearance and/or poor corrosion resistance, which limited their applications. In this research, Al was first electropolished in a phosphoric acid-based solution, then anodized in a sulfuric acid-based solution under controlled processing parameters. The anodized specimen was then sealed by two-step sealing method. A systematic study including microstructure, surface morphology, hardness and corrosion resistance of these anodized films has been conducted. Results show that the hardness of this new anodized film was increased by a factor of 10 compared with the pure Al metal. Salt spray corrosion testing also demonstrated the greatly improved corrosion resistance. Unlike the traditional hard anodized Al which presents a dull-colored surface, this newly developed anodized Al alloy possesses a very bright and shiny surface with good hardness and corrosion resistance.

A semiempirical model for interpreting microwave emission from semiarid land surfaces as seen from space

NASA Technical Reports Server (NTRS)

Kerr, Yann H.; Njoku, Eni G.

1990-01-01

A radiative-transfer model for simulating microwave brightness temperatures over land surfaces is described. The model takes into account sensor viewing conditions (spacecraft altitude, viewing angle, frequency, and polarization) and atmospheric parameters over a soil surface characterized by its moisture, roughness, and temperature and covered with a layer of vegetation characterized by its temperature, water content, single scattering albedo, structure, and percent coverage. In order to reduce the influence of atmospheric and surface temperature effects, the brightness temperatures are expressed as polarization ratios that depend primarily on the soil moisture and roughness, canopy water content, and percentage of cover. The sensitivity of the polarization ratio to these parameters is investigated. Simulation of the temporal evolution of the microwave signal over semiarid areas in the African Sahel is presented and compared to actual satellite data from the SMMR instrument on Nimbus-7.

Vesta Mineralogy after Dawn Global Observations

NASA Technical Reports Server (NTRS)

ChristinaDeSanctis, Maria; Ammannito, E.; Capaccioni, F.; Cparia, M. T.; Carraro, F.; Fonte, S.; Frigeri, A.; Longobardo, A.; Marchi, S.; Palomba, E.;

Simulations of the effects of water vapor, cloud liquid water, and ice on AMSU moisture channel brightness temperatures

NASA Technical Reports Server (NTRS)

Muller, Bradley M.; Fuelberg, Henry E.; Xiang, Xuwu

1994-01-01

Radiative transfer simulations are performed to determine how water vapor and nonprecipitating cloud liquid water and ice particles within typical midlatitude atmospheres affect brightness temperatures T(sub B)'s of moisture sounding channels used in the Advanced Microwave Sounding Unit (AMSU) and AMSU-like instruments. The purpose is to promote a general understanding of passive top-of-atmosphere T(sub B)'s for window frequencies at 23.8, 89.0, and 157.0 GHz, and water vapor frequencies at 176.31, 180.31, and 182.31 GHz by documenting specific examples. This is accomplished through detailed analyses of T(sub B)'s for idealized atmospheres, mostly representing temperate conditions over land. Cloud effects are considered in terms of five basic properties: droplet size distribution, phase, liquid or ice water content, altitude, and thickness. Effects on T(sub B) of changing surface emissivity also are addressed. The brightness temperature contribution functions are presented as an aid to physically interpreting AMSU T(sub B)'s. Both liquid and ice clouds impact the T(sub B)'s in a variety of ways. The T(sub B)'s at 23.8 and 89 GHz are more strongly affected by altostratus liquid clouds than by cirrus clouds for equivalent water paths. In contrast, channels near 157 and 183 GHz are more strongly affected by ice clouds. Higher clouds have a greater impact on 157- and 183-GHz T(sub B)'s than do lower clouds. Clouds depress T(sub B)'s of the higher-frequency channels by suppressing, but not necessarily obscuring, radiance contributions from below. Thus, T(sub B)'s are less closely associated with cloud-top temperatures than are IR radiometric temperatures. Water vapor alone accounts for up to 89% of the total attenuation by a midtropospheric liquid cloud for channels near 183 GHz. The Rayleigh approximation is found to be adequate for typical droplet size distributions; however, Mie scattering effects from liquid droplets become important for droplet size distribution functions with modal radii greater than 20 micrometers near 157 and 183 GHz, and greater than 30-40 micrometers at 89 GHz. This is due mainly to the relatively small concentrations of droplets much larger than the mode radius. Orographic clouds and tropical cumuli have been observed to contain droplet size distributions with mode radii in the 30-40 micrometers range. Thus, as new instruments bridge the gap between microwave and infrared to frequencies even higher than 183 GHz, radiative transfer modelers are cautioned to explicitly address scattering characteristics of such clouds.

Surface brightness profiles of 10 comets

NASA Astrophysics Data System (ADS)

Jewitt, D. C.; Meech, K. J.

1987-06-01

CCD photometric observations of the comae of 10 comets, obtained at the 4-m and 2.1-m telescopes at KPNO during 1985-1986 using filters centered at 700.5, 650.0, or 546.0 nm, are reported. The data are presented in extensive tables and graphs and characterized in detail. The radial surface brightness profiles are shown to be steeper than predicted by an idealized spherically symmetric steady-state comet model, the steepness increasing with the projected distance from the nucleus. These profiles are attributed, on the basis of Monte Carlo simulations, to imperfect coupling between the sublimated gas and the optically dominant grains of the coma.

Rayleigh beacon for measuring the surface profile of a radio telescope.

PubMed

Padin, S

2014-12-01

Millimeter-wavelength Rayleigh scattering from water droplets in a cloud is proposed as a means of generating a bright beacon for measuring the surface profile of a radio telescope. A λ=3  mm transmitter, with an output power of a few watts, illuminating a stratiform cloud, can generate a beacon with the same flux as Mars in 10 GHz bandwidth, but the beacon has a narrow line width, so it is extremely bright. The key advantage of the beacon is that it can be used at any time, and positioned anywhere in the sky, as long as there are clouds.

Planetary camera observations of the double nucleus of M31

NASA Technical Reports Server (NTRS)

Lauer, Tod R.; Faber, S. M.; Groth, Edward J.; Shaya, Edward J.; Campbell, Bel; Code, Arthur; Currie, Douglas G.; Baum, William A.; Ewald, S. P.; Hester, J. J.

1993-01-01

HST Planetary Camera images obtained in the V and I band for M31 show its inner nucleus to consist of two components that are separated by 0.49 arcsec. The nuclear component with lower surface brightness closely coincides with the bulge photocenter and is argued to be at the kinematic center of the galaxy. It is surmised that, if dust absorption generates the asymmetric nuclear morphology observed, the dust grain size must either be exceptionally large, or the dust optical depth must be extremely high; the higher surface-brightness and off-center nuclear component may alternatively be a separate stellar system.

OH+ emission from cometary knots in planetary nebulae

NASA Astrophysics Data System (ADS)

Priestley, F. D.; Barlow, M. J.

2018-05-01

We model the molecular emission from cometary knots in planetary nebulae (PNe) using a combination of photoionization and photodissociation region (PDR) codes, for a range of central star properties and gas densities. Without the inclusion of ionizing extreme ultraviolet (EUV) radiation, our models require central star temperatures T* to be near the upper limit of the range investigated in order to match observed H2 and OH+ surface brightnesses consistent with observations - with the addition of EUV flux, our models reproduce observed OH+ surface brightnesses for T* ≥ 100 kK. For T* < 80 kK, the predicted OH+ surface brightness is much lower, consistent with the non-detection of this molecule in PNe with such central star temperatures. Our predicted level of H2 emission is somewhat weaker than commonly observed in PNe, which may be resolved by the inclusion of shock heating or fluorescence due to UV photons. Some of our models also predict ArH+ and HeH+ rotational line emission above detection thresholds, despite neither molecule having been detected in PNe, although the inclusion of photodissociation by EUV photons, which is neglected by our models, would be expected to reduce their detectability.

Compact Groups analysis using weak gravitational lensing II: CFHT Stripe 82 data

NASA Astrophysics Data System (ADS)

Chalela, Martín; Gonzalez, Elizabeth Johana; Makler, Martín; Lambas, Diego García; Pereira, Maria E. S.; O'mill, Ana; Shan, HuanYuan

2018-06-01

In this work we present a lensing study of Compact Groups (CGs) using data obtained from the high quality Canada-France-Hawaii Telescope Stripe 82 Survey. Using stacking techniques we obtain the average density contrast profile. We analyse the lensing signal dependence on the groups surface brightness and morphological content, for CGs in the redshift range z = 0.2 - 0.4. We obtain a larger lensing signal for CGs with higher surface brightness, probably due to their lower contamination by interlopers. Also, we find a strong dependence of the lensing signal on the group concentration parameter, with the most concentrated quintile showing a significant lensing signal, consistent with an isothermal sphere with σV = 336 ± 28 km/s and a NFW profile with R200 = 0.60 ± 0.05 h_{70}^{-1}Mpc. We also compare lensing results with dynamical estimates finding a good agreement with lensing determinations for CGs with higher surface brightness and higher concentration indexes. On the other hand, CGs that are more contaminated by interlopers show larger dynamical dispersions, since interlopers bias dynamical estimates to larger values, although the lensing signal is weakened.