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Full-Text Articles in Physical Sciences and Mathematics
The Opacity Of Spiral Galaxy Disks. Vi. Extinction, Stellar Light And Color., Benne W. Holwerda, R. A. Gonzalez, P. C. Van Der Kruit, R. J. Allen
The Opacity Of Spiral Galaxy Disks. Vi. Extinction, Stellar Light And Color., Benne W. Holwerda, R. A. Gonzalez, P. C. Van Der Kruit, R. J. Allen
Faculty Scholarship
In this paper we explore the relation between dust extinction and stellar light distribution in disks of spiral galaxies. Extinction influences our dynamical and photometric perception of disks, since it can distort our measurement of the contribution of the stellar component. To characterize the total extinction by a foreground disk, González et al. (1998, ApJ, 506, 152) proposed the "Synthetic Field Method" (SFM), which uses the calibrated number of distant galaxies seen through the foreground disk as a direct indication of extinction. The method is described in González et al. (1998, ApJ, 506, 152) and Holwerda et al. (2005a, AJ, …
The Opacity Of Spiral Galaxy Disks. V. Dust Opacity, Hi Distributions And Sub-Mm Emission., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
The Opacity Of Spiral Galaxy Disks. V. Dust Opacity, Hi Distributions And Sub-Mm Emission., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
Faculty Scholarship
The opacity of spiral galaxy disks, from counts of distant galaxies, is compared to HI column densities. The opacity measurements are calibrated using the “Synthetic Field Method” from González et al. (1998, ApJ, 506, 152), Holwerda et al. (2005a, AJ, 129, 1381). When compared for individual disks, the HI column density and dust opacity do not seem to be correlated as HI and opacity follow different radial profiles. To improve statistics, an average radial opacity profile is compared to an average HI profile. Compared to dust-to-HI estimates from the literature, more extinction is found in this profile. This difference may …
Modelling Continuum Optical And Ultraviolet Polarization Of Active Galactic Nuclei, René W. Goosmann, C. Martin Gaskell
Modelling Continuum Optical And Ultraviolet Polarization Of Active Galactic Nuclei, René W. Goosmann, C. Martin Gaskell
Department of Physics and Astronomy: Faculty Publications
We present results from a new Monte Carlo radiative transfer computer code, STOKES, developed to model polarization induced by scattering off free electrons and dust grains. STOKES is freely available on the web and can be used to model scattering in a wide variety of astrophysical situations. For edge-on (type-2) viewing positions, the polarization produced by a dusty torus alone is largely wavelength-independent.
This is because the torus is optically thick and the change in albedo with wavelength is slight. Wavelength-independent polarization therefore does not necessarily imply electron scattering. We are able to fully explain wavelength independent type-2 polarization without …
Hyperspectral Simulation And Recovery Of Submerged Targets In Turbid Waters, Charles R. Bostater
Hyperspectral Simulation And Recovery Of Submerged Targets In Turbid Waters, Charles R. Bostater
Ocean Engineering and Marine Sciences Faculty Publications
Modeled hyperspectral reflectance signatures just above the water surface are obtained from radiative transfer models to create synthetic images of targets below the water surface. Images are displayed as 24 bit RGB images of the water surface using selected channels. Example model outputs are presented in this paper for a hyperspectral Monte Carlo and a hyperspectral layered analytical iterative model of radiative transport within turbid shallow water types. Images at the selected wavelengths or channels centered at 490, 530 and 680 nm suggests the two models provide quite similar results when displayed as RGB images. The techniques are demonstrated to …
The Opacity Of Spiral Galaxy Disks. Iv. Radial Extinction Profiles From Counts Of Distant Galaxies Seen Through Foreground Disks., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
The Opacity Of Spiral Galaxy Disks. Iv. Radial Extinction Profiles From Counts Of Distant Galaxies Seen Through Foreground Disks., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
Faculty Scholarship
Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. and Holwerda et al. developed the Synthetic Field Method (SFM ), which analyzes synthetic fields constructed by adding various deep exposures of unobstructed background fields to the candidate foreground galaxy field. The advantage of the SFM is that it gives the average opacity for the area of a galaxy disk without making assumptions about either the distribution of absorbers or of the disk starlight. However, it …
The Opacity Of Spiral Galaxy Disks. Iii. Automating The Synthetic Field Method., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
The Opacity Of Spiral Galaxy Disks. Iii. Automating The Synthetic Field Method., Benne W. Holwerda, R. A. Gonzalez, Ronald J. Allen, P. C. Van Der Kruit
Faculty Scholarship
Dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. developed a method for this calibration, the Synthetic Field Method (SFM), and applied this concept to a Hubble Space Telescope (HST )/Wide Field Planetary Camera 2 image of NGC 4536. The SFM estimates the total extinction through the disk without requiring assumptions about the distribution of absorbers or disk light. The poor statistics, however, result in large errors in individual measurements. We …
High-Resolution Ocean Color Remote Sensing Of Benthic Habitats: A Case Study At The Roatan Island, Honduras, Deepak R. Mishra, Sunil G. Narumalani, Donald Rundquist, Merlin P. Lawson
High-Resolution Ocean Color Remote Sensing Of Benthic Habitats: A Case Study At The Roatan Island, Honduras, Deepak R. Mishra, Sunil G. Narumalani, Donald Rundquist, Merlin P. Lawson
Department of Earth and Atmospheric Sciences: Faculty Publications
Natural resource managers clamor for detailed reef habitat maps for monitoring smaller scale disturbances in reef communities. Coastal ocean color remote sensing techniques permit benthic habitats to be explored with higher resolution than ever before. The objective of this research was to develop an accurate benthic habitat map for an area off the northwest coast of Roatan Island, Honduras, using high-resolution multispectral IKONOS data. Atmospheric (Rayleigh and aerosol path radiance) and water column corrections (water depth and water column attenuation) were applied to the imagery, making it a robust method for mapping benthic habitats. Water depth for each pixel was …