Browsing by Subject "band"

Now showing 1 - 10 of 10

The Abundances Of Polyacetylenes Toward CRL618
(2011-02) Fonfria, J. P.; Cernicharo, J.; Richter, Matthew J.; Lacy, John H.; Lacy, John H.
We present a mid-infrared high spectral resolution spectrum of CRL618 in the frequency ranges 778-784 and 1227-1249 cm(-1) (8.01-8.15 and 12.75-12.85 mu m) taken with the Texas Echelon-cross-Echelle Spectrograph (TEXES) and the Infrared Telescope Facility (IRTF). We have identified more than 170 rovibrational lines arising from C2H2, HCN, C4H2, and C6H2. We have found no unmistakable trace of C8H2. The line profiles display a complex structure suggesting the presence of polyacetylenes in several components of the circumstellar envelope (CSE). We derive total column densities of 2.5x10(17), 3.1x10(17), 2.1x10(17), 9.3x10(16) cm(-2), and less than or similar to 5x10(16) cm(-2) for HCN, C2H2, C4H2, C6H2, and C8H2, respectively. The observations indicate that both the rotational and vibrational temperatures in the innermost CSE depend on the molecule, varying from 100 to 350 K for the rotational temperatures and 100 to 500 K for the vibrational temperatures. Our results support a chemistry in the innermost CSE based on radical-neutral reactions triggered by the intense UV radiation field.
The c2d Spitzer Spectroscopic Survey Of Ices Around Low-Mass Young Stellar Objects. II. CO2
(2008-05) Pontoppidan, Klaus M.; Boogert, Adwin C. A.; Fraser, Helen J.; van Dishoeck, Ewine F.; Blake, Geoffrey A.; Lahuis, Fred; Oberg, Karin I.; Evans, Neal J.; Salyk, Colette; Evans, Neal J.
This paper presents Spitzer IRS lambda/Delta lambda similar to 600 spectroscopy of the CO2 15.2 mu m bending mode toward 50 embedded young low-mass stars, taken mostly from the "Cores to Disks'' (c2d) Legacy program. The average abundance of solid CO2 relative to water in low-mass protostellar envelopes is 0.32 +/- 0.02, significantly higher than that found in quiescent molecular clouds and in massive star-forming regions. A decomposition of the observed CO2 bending mode profiles requires a minimum of five unique components. Roughly 2/3 of the CO2 ice is found in a water-rich environment, while most of the remaining 1/3 is found in a CO environment with strongly varying relative concentrations of CO2 to CO along each line of sight. Ground-based observations of solid CO toward a large subset of the c2d sample are used to further constrain the CO2:CO component and suggest a model in which low-density clouds form the CO2:H2O component and higher density clouds form the CO2:CO ice during and after the freezeout of gas-phase CO. The abundance of the CO2:CO component is consistent with cosmic-ray processing of the CO-rich part of the ice mantles, although a more quiescent formation mechanism is not ruled out. It is suggested that the subsequent evolution of the CO2 and CO profiles toward low-mass protostars, in particular the splitting of the CO2 bending mode due to pure, crystalline CO2, is first caused by distillation of the CO2:CO component through evaporation of CO due to thermal processing to similar to 20-30 K. The formation of pure CO2 via segregation from the H2O rich mantle may contribute to the band splitting at higher levels of thermal processing (greater than or similar to 50 K) but is harder to reconcile with the physical structure of protostellar envelopes around low-luminosity objects.
Debris Thickness of Glaciers in the Everest Area (Nepal Himalaya) Derived from Satellite Imagery Using a Nonlinear Energy Balance Model
(2014-07) Rounce, D. R.; McKinney, D. C.; Rounce, D. R.; McKinney, D. C.
Debris thickness is an important characteristic of debris-covered glaciers in the Everest region of the Himalayas. The debris thickness controls the melt rates of the glaciers, which has large implications for hydrologic models, the glaciers' response to climate change, and the development of glacial lakes. Despite its importance, there is little knowledge of how the debris thickness varies over these glaciers. This paper uses an energy balance model in conjunction with Landsat7 Enhanced Thematic Mapper Plus (ETM+) satellite imagery to derive thermal resistances, which are the debris thickness divided by the thermal conductivity. Model results are reported in terms of debris thickness using an effective thermal conductivity derived from field data. The developed model accounts for the nonlinear temperature gradient in the debris cover to derive reasonable debris thicknesses. Fieldwork performed on Imja-Lhotse Shar Glacier in September 2013 was used to compare to the modeled debris thicknesses. Results indicate that accounting for the nonlinear temperature gradient is crucial. Furthermore, correcting the incoming shortwave radiation term for the effects of topography and resampling to the resolution of the thermal band's pixel is imperative to deriving reasonable debris thicknesses. Since the topographic correction is important, the model will improve with the quality of the digital elevation model (DEM). The main limitation of this work is the poor resolution (60m) of the satellite's thermal band. The derived debris thicknesses are reasonable at this resolution, but trends related to slope and aspect are unable to be modeled on a finer scale. Nonetheless, the study finds this model derives reasonable debris thicknesses on this scale and was applied to other debris-covered glaciers in the Everest region.
Light-Element Abundance Variations At Low Metallicity: The Globular Cluster NGC 5466
(2010-10) Shetrone, Matthew; Martell, Sarah L.; Wilkerson, Rachel; Adams, Joshua; Siegel, Michael H.; Smith, Graeme H.; Bond, Howard E.; Adams, Joshua
We present low-resolution (R similar or equal to 850) spectra for 67 asymptotic giant branch (AGB), horizontal branch, and red giant branch (RGB) stars in the low-metallicity globular cluster NGC 5466, taken with the VIRUS-P integral-field spectrograph at the 2.7 m Harlan J. Smith telescope at McDonald Observatory. Sixty-six stars are confirmed, and one rejected, as cluster members based on radial velocity, which we measure to an accuracy of 16 km s(-1) via template-matching techniques. CN and CH band strengths have been measured for 29 RGB and AGB stars in NGC 5466, and the band-strength indices measured from VIRUS-P data show close agreement with those measured from Keck/LRIS spectra previously taken for five of our target stars. We also determine carbon abundances from comparisons with synthetic spectra. The RGB stars in our data set cover a range in absolute V magnitude from +2 to -3, which permits us to study the rate of carbon depletion on the giant branch as well as the point of its onset. The data show a clear decline in carbon abundance with rising luminosity above the luminosity function >bump> on the giant branch, and also a subdued range in CN band strength, suggesting ongoing internal mixing in individual stars but minor or no primordial star-to-star variation in light-element abundances.
Light-Element Abundance Variations At Low Metallicity: The Globular Cluster NGC 5466
(2010-10) Shetrone, Matthew; Martell, Sarah L.; Wilkerson, Rachel; Adams, Joshua; Siegel, Michael H.; Smith, Graeme H.; Bond, Howard E.; Adams, Joshua
We present low-resolution (R similar or equal to 850) spectra for 67 asymptotic giant branch (AGB), horizontal branch, and red giant branch (RGB) stars in the low-metallicity globular cluster NGC 5466, taken with the VIRUS-P integral-field spectrograph at the 2.7 m Harlan J. Smith telescope at McDonald Observatory. Sixty-six stars are confirmed, and one rejected, as cluster members based on radial velocity, which we measure to an accuracy of 16 km s(-1) via template-matching techniques. CN and CH band strengths have been measured for 29 RGB and AGB stars in NGC 5466, and the band-strength indices measured from VIRUS-P data show close agreement with those measured from Keck/LRIS spectra previously taken for five of our target stars. We also determine carbon abundances from comparisons with synthetic spectra. The RGB stars in our data set cover a range in absolute V magnitude from +2 to -3, which permits us to study the rate of carbon depletion on the giant branch as well as the point of its onset. The data show a clear decline in carbon abundance with rising luminosity above the luminosity function >bump> on the giant branch, and also a subdued range in CN band strength, suggesting ongoing internal mixing in individual stars but minor or no primordial star-to-star variation in light-element abundances.
Precribed Music Revised for 1961-1962 and 1962-1963
(University of Texas at Austin, 1961-06-15) University of Texas at Austin
Precribed Music Revised for 1963,1964,1965,1966
(University of Texas at Austin, 1963-09-01) University of Texas at Austin
Prescribed Music for 1949-1950 Regional Music Competition-Festivals The University Interscholastic League
(University of Texas at Austin, 1949-10-01) University of Texas at Austin
A Revised Parallel-Sequence Morphological Classification of Galaxies: Structure and Formation of S0 and Spheroidal Galaxies
(2012-01) Kormendy, John; Bender, Ralf; Kormendy, John
We update van den Bergh's parallel-sequence galaxy classification in which S0 galaxies form a sequence S0a-S0b-S0c that parallels the sequence Sa-Sb-Sc of spiral galaxies. The ratio B/T of bulge-to-total light defines the position of a galaxy in this tuning-fork diagram. Our classification makes one major improvement. We extend the S0a-S0b-S0c sequence to spheroidal ("Sph") galaxies that are positioned in parallel to irregular galaxies in a similarly extended Sa-Sb-Sc-Im sequence. This provides a natural "home" for spheroidals, which previously were omitted from galaxy classification schemes or inappropriately combined with ellipticals. To motivate our juxtaposition of Sph and Im galaxies, we present photometry and bulge-disk decompositions of four rare, late-type S0s that bridge the gap between the more common S0b and Sph galaxies. NGC 4762 is an edge-on SB0bc galaxy with a very small classical-bulge-to-total ratio of B/T = 0.13 +/- 0.02. NGC 4452 is an edge-on SB0 galaxy with an even tinier pseudobulge-to-total ratio of PB/T = 0.017 +/- 0.004. It is therefore an SB0c. VCC 2048, whose published classification is S0, contains an edge-on disk, but its "bulge" plots in the structural parameter sequence of spheroidals. It is therefore a disky Sph. And NGC 4638 is similarly a "missing link" between S0s and Sphs-it has a tiny bulge and an edge-on disk embedded in an Sph halo. In the Appendix, we present photometry and bulge-disk decompositions of all Hubble Space Telescope Advanced Camera for Surveys Virgo Cluster Survey S0s that do not have published decompositions. We use these data to update the structural parameter correlations of Sph, S + Im, and E galaxies. We show that Sph galaxies of increasing luminosity form a continuous sequence with the disks (but not bulges) of S0c-S0b-S0a galaxies. Remarkably, the Sph-S0-disk sequence is almost identical to that of Im galaxies and spiral galaxy disks. We review published observations for galaxy transFormation processes, particularly ram-pressure stripping of cold gas. We suggest that Sph galaxies are transformed, "red and dead" Scd-Im galaxies in the same way that many S0 galaxies are transformed, red and dead Sa-Sc spiral galaxies.
The Volatile Composition and Activity of Comet 103P/Hartley 2 During the EPOXI Closest Approach
(2011-06) Dello Russo, N.; Vervack, R. J.; Lisse, C. M.; Weaver, H. A.; Kawakita, H.; Kobayashi, H.; Cochran, Anita L.; Harris, W. M.; McKay, A. J.; Biver, N.; Bockelee-Morvan, D.; Crovisier, J.; Cochran, Anita L.
We report time-resolved measurements of the absolute and relative abundances of eight parent volatiles (H2O, CH3OH, C2H6, C2H2, NH3, HCN, H2CO, and HC3N) in the coma of 103P/Hartley 2 on UT 2010 November 4, the date the EPOXI spacecraft made its closest approach to the comet, using high-dispersion infrared spectroscopy with NIRSPEC at the W. M. Keck Observatory. Overall gas and dust production increased by roughly 60% between UT 10:49 and 15:54. Differences in the spatial distributions of species in the coma suggest icy sources of different composition in the nucleus of 103P/Hartley 2. However, differences in the relative abundances of species with time are minor, suggesting either internal compositional heterogeneity in 103P/Hartley 2 is small compared with the diversity of chemistry observed within the comet population, or more significant heterogeneity exists on scales smaller than our spatial resolution. Observations contemporaneous with the EPOXI encounter test how compositional heterogeneity over the surface and the inner coma of a comet manifests itself in remote-sensing observations of the bulk coma.