The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Kristin M Burgess - One of the best experts on this subject based on the ideXlab platform.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
The Astrophysical Journal, 2007Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0 cm-2 ≤ log NH I ≤ 20.3 cm-2) from a large sample of high-resolution spectra acquired using the Keck and Magellan telescopes. Specifically, we present 47 new SLLSs from 113 QSO sight lines. We focus on the neutral hydrogen frequency distribution fH I(N, X) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with log NH I ≥ 20.3 cm-2). We find that the fH I(N, X) of the SLLSs can be reasonably described with a power law of index α = -1.43 or -1.19 depending on whether we set the lower NH I bound for the analysis at 1019.0 or 1019.3 cm-2, respectively. The results indicate a flattening in the slope of fH I(N, X) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of fH I(N, X) for the SLLSs over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of fH I(N, X), the line density lSLLS(X). We introduce the observable distribution Function (N, X) and its moment, which elucidates comparisons of H I absorbers from the Lyα forest through to the DLA. We find that a simple three-Parameter Function can fit (N, X) over the range 17.0 cm-2 ≤ log NH I ≤ 22.0 cm-2. We use these results to predict that fH I(N, X) must show two additional inflections below the SLLS regime to match the observed fH I(N, X) distribution of the Lyα forest. Finally, we demonstrate that SLLSs contribute a minor fraction (≈15%) of the universe's hydrogen atoms and, therefore, an even smaller fraction of the mass in predominantly neutral gas.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
arXiv: Astrophysics, 2006Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLS; defined to be absorbers with 19.0 = 20.3 cm^-2). We find that that f(N,X) of the SLLS can be reasonably described with a power-law of index alpha = -1.43^{+0.15}_{-0.16} or alpha = -1.19^{+0.20}_{-0.21} depending on whether we set the lower N(HI) bound for the analysis at 10^{19.0} cm^-2 or 10^{19.3}$ cm^-2, respectively. The results indicate a flattening in the slope of f(N,X) between the SLLS and DLA. We find little evidence for redshift evolution in the shape of f(N,X) for the SLLS over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of f(N,X), the line density l_lls(X). We introduce the observable distribution Function O(N,X) and its moment, which elucidates comparisons of HI absorbers from the Lyman-alpha through to the DLA. We find that a simple three Parameter Function can fit O(N,X) over the range 17.0 <= log(NHI) <=22.0. We use these results to predict that f(N,X) must show two additional inflections below the SLLS regime to match the observed f(N,X) distribution of the Lyman-alpha forest. Finally, we demonstrate that SLLS contribute a minor fraction (~15%) of the universe's hydrogen atoms and, therefore, an even small fraction of the mass in predominantly neutral gas.
Gabriel E Prochter - One of the best experts on this subject based on the ideXlab platform.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
The Astrophysical Journal, 2007Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0 cm-2 ≤ log NH I ≤ 20.3 cm-2) from a large sample of high-resolution spectra acquired using the Keck and Magellan telescopes. Specifically, we present 47 new SLLSs from 113 QSO sight lines. We focus on the neutral hydrogen frequency distribution fH I(N, X) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with log NH I ≥ 20.3 cm-2). We find that the fH I(N, X) of the SLLSs can be reasonably described with a power law of index α = -1.43 or -1.19 depending on whether we set the lower NH I bound for the analysis at 1019.0 or 1019.3 cm-2, respectively. The results indicate a flattening in the slope of fH I(N, X) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of fH I(N, X) for the SLLSs over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of fH I(N, X), the line density lSLLS(X). We introduce the observable distribution Function (N, X) and its moment, which elucidates comparisons of H I absorbers from the Lyα forest through to the DLA. We find that a simple three-Parameter Function can fit (N, X) over the range 17.0 cm-2 ≤ log NH I ≤ 22.0 cm-2. We use these results to predict that fH I(N, X) must show two additional inflections below the SLLS regime to match the observed fH I(N, X) distribution of the Lyα forest. Finally, we demonstrate that SLLSs contribute a minor fraction (≈15%) of the universe's hydrogen atoms and, therefore, an even smaller fraction of the mass in predominantly neutral gas.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
arXiv: Astrophysics, 2006Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLS; defined to be absorbers with 19.0 = 20.3 cm^-2). We find that that f(N,X) of the SLLS can be reasonably described with a power-law of index alpha = -1.43^{+0.15}_{-0.16} or alpha = -1.19^{+0.20}_{-0.21} depending on whether we set the lower N(HI) bound for the analysis at 10^{19.0} cm^-2 or 10^{19.3}$ cm^-2, respectively. The results indicate a flattening in the slope of f(N,X) between the SLLS and DLA. We find little evidence for redshift evolution in the shape of f(N,X) for the SLLS over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of f(N,X), the line density l_lls(X). We introduce the observable distribution Function O(N,X) and its moment, which elucidates comparisons of HI absorbers from the Lyman-alpha through to the DLA. We find that a simple three Parameter Function can fit O(N,X) over the range 17.0 <= log(NHI) <=22.0. We use these results to predict that f(N,X) must show two additional inflections below the SLLS regime to match the observed f(N,X) distribution of the Lyman-alpha forest. Finally, we demonstrate that SLLS contribute a minor fraction (~15%) of the universe's hydrogen atoms and, therefore, an even small fraction of the mass in predominantly neutral gas.
J X Prochaska - One of the best experts on this subject based on the ideXlab platform.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
The Astrophysical Journal, 2007Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0 cm-2 ≤ log NH I ≤ 20.3 cm-2) from a large sample of high-resolution spectra acquired using the Keck and Magellan telescopes. Specifically, we present 47 new SLLSs from 113 QSO sight lines. We focus on the neutral hydrogen frequency distribution fH I(N, X) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with log NH I ≥ 20.3 cm-2). We find that the fH I(N, X) of the SLLSs can be reasonably described with a power law of index α = -1.43 or -1.19 depending on whether we set the lower NH I bound for the analysis at 1019.0 or 1019.3 cm-2, respectively. The results indicate a flattening in the slope of fH I(N, X) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of fH I(N, X) for the SLLSs over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of fH I(N, X), the line density lSLLS(X). We introduce the observable distribution Function (N, X) and its moment, which elucidates comparisons of H I absorbers from the Lyα forest through to the DLA. We find that a simple three-Parameter Function can fit (N, X) over the range 17.0 cm-2 ≤ log NH I ≤ 22.0 cm-2. We use these results to predict that fH I(N, X) must show two additional inflections below the SLLS regime to match the observed fH I(N, X) distribution of the Lyα forest. Finally, we demonstrate that SLLSs contribute a minor fraction (≈15%) of the universe's hydrogen atoms and, therefore, an even smaller fraction of the mass in predominantly neutral gas.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
arXiv: Astrophysics, 2006Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLS; defined to be absorbers with 19.0 = 20.3 cm^-2). We find that that f(N,X) of the SLLS can be reasonably described with a power-law of index alpha = -1.43^{+0.15}_{-0.16} or alpha = -1.19^{+0.20}_{-0.21} depending on whether we set the lower N(HI) bound for the analysis at 10^{19.0} cm^-2 or 10^{19.3}$ cm^-2, respectively. The results indicate a flattening in the slope of f(N,X) between the SLLS and DLA. We find little evidence for redshift evolution in the shape of f(N,X) for the SLLS over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of f(N,X), the line density l_lls(X). We introduce the observable distribution Function O(N,X) and its moment, which elucidates comparisons of HI absorbers from the Lyman-alpha through to the DLA. We find that a simple three Parameter Function can fit O(N,X) over the range 17.0 <= log(NHI) <=22.0. We use these results to predict that f(N,X) must show two additional inflections below the SLLS regime to match the observed f(N,X) distribution of the Lyman-alpha forest. Finally, we demonstrate that SLLS contribute a minor fraction (~15%) of the universe's hydrogen atoms and, therefore, an even small fraction of the mass in predominantly neutral gas.
John M Omeara - One of the best experts on this subject based on the ideXlab platform.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
The Astrophysical Journal, 2007Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLSs; defined to be absorbers with 19.0 cm-2 ≤ log NH I ≤ 20.3 cm-2) from a large sample of high-resolution spectra acquired using the Keck and Magellan telescopes. Specifically, we present 47 new SLLSs from 113 QSO sight lines. We focus on the neutral hydrogen frequency distribution fH I(N, X) of the SLLS and its moments and compare these results with the Lyα forest and the damped Lyα systems (DLAs; absorbers with log NH I ≥ 20.3 cm-2). We find that the fH I(N, X) of the SLLSs can be reasonably described with a power law of index α = -1.43 or -1.19 depending on whether we set the lower NH I bound for the analysis at 1019.0 or 1019.3 cm-2, respectively. The results indicate a flattening in the slope of fH I(N, X) between the SLLSs and DLAs. We find little evidence for redshift evolution in the shape of fH I(N, X) for the SLLSs over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of fH I(N, X), the line density lSLLS(X). We introduce the observable distribution Function (N, X) and its moment, which elucidates comparisons of H I absorbers from the Lyα forest through to the DLA. We find that a simple three-Parameter Function can fit (N, X) over the range 17.0 cm-2 ≤ log NH I ≤ 22.0 cm-2. We use these results to predict that fH I(N, X) must show two additional inflections below the SLLS regime to match the observed fH I(N, X) distribution of the Lyα forest. Finally, we demonstrate that SLLSs contribute a minor fraction (≈15%) of the universe's hydrogen atoms and, therefore, an even smaller fraction of the mass in predominantly neutral gas.
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the keck magellan survey for lyman limit absorption i the frequency distribution of super lyman limit systems
arXiv: Astrophysics, 2006Co-Authors: John M Omeara, J X Prochaska, Scott Burles, Gabriel E Prochter, Rebecca A Bernstein, Kristin M BurgessAbstract:We present the results of a survey for super Lyman limit systems (SLLS; defined to be absorbers with 19.0 = 20.3 cm^-2). We find that that f(N,X) of the SLLS can be reasonably described with a power-law of index alpha = -1.43^{+0.15}_{-0.16} or alpha = -1.19^{+0.20}_{-0.21} depending on whether we set the lower N(HI) bound for the analysis at 10^{19.0} cm^-2 or 10^{19.3}$ cm^-2, respectively. The results indicate a flattening in the slope of f(N,X) between the SLLS and DLA. We find little evidence for redshift evolution in the shape of f(N,X) for the SLLS over the redshift range of the sample 1.68 < z < 4.47 and only tentative evidence for evolution in the zeroth moment of f(N,X), the line density l_lls(X). We introduce the observable distribution Function O(N,X) and its moment, which elucidates comparisons of HI absorbers from the Lyman-alpha through to the DLA. We find that a simple three Parameter Function can fit O(N,X) over the range 17.0 <= log(NHI) <=22.0. We use these results to predict that f(N,X) must show two additional inflections below the SLLS regime to match the observed f(N,X) distribution of the Lyman-alpha forest. Finally, we demonstrate that SLLS contribute a minor fraction (~15%) of the universe's hydrogen atoms and, therefore, an even small fraction of the mass in predominantly neutral gas.
Kevin Heng - One of the best experts on this subject based on the ideXlab platform.
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optical properties of potential condensates in exoplanetary atmospheres
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Daniel Kitzmann, Kevin HengAbstract:The prevalence of clouds in currently observable exoplanetary atmospheres motivates the compilation and calculation of their optical properties. First, we present a new open-source Mie scattering code known as LX-MIE, which is able to consider large-size Parameters (~10⁷) using a single computational treatment. We validate LX-MIE against the classical MIEVO code as well as previous studies. Secondly, we embark on an expanded survey of the published literature for both the real and imaginary components of the refractive indices of 32 condensate species. As much as possible, we rely on experimental measurements of the refractive indices and resort to obtaining the real from the imaginary component (or vice versa), via the Kramers–Kronig relation, only in the absence of data. We use these refractive indices as input for LX-MIE to compute the absorption, scattering and extinction efficiencies of all 32 condensate species. Finally, we use a three-Parameter Function to provide convenient fits to the shape of the extinction efficiency curve. We show that the errors associated with these simple fits in the Wide Field Camera 3 (WFC3), J, H, and K wavebands are ~10 per cent. These fits allow for the extinction cross-section or opacity of the condensate species to be easily included in retrieval analyses of transmission spectra. We discuss prospects for future experimental work. The compilation of the optical constants and LX-MIE is publicly available as part of the open-source Exoclime Simulation Platform (http://www.exoclime.org).
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optical properties of potential condensates in exoplanetary atmospheres
arXiv: Earth and Planetary Astrophysics, 2017Co-Authors: Daniel Kitzmann, Kevin HengAbstract:The prevalence of clouds in currently observable exoplanetary atmospheres motivates the compilation and calculation of their optical properties. First, we present a new open-source Mie scattering code known as LX-MIE, which is able to consider large size Parameters ($\sim 10^7$) using a single computational treatment. We validate LX-MIE against the classical MIEV0 code as well as previous studies. Second, we embark on an expanded survey of the published literature for both the real and imaginary components of the refractive indices of 32 condensate species. As much as possible, we rely on experimental measurements of the refractive indices and resort to obtaining the real from the imaginary component (or vice versa), via the Kramers-Kronig relation, only in the absence of data. We use these refractive indices as input for LX-MIE to compute the absorption, scattering and extinction efficiencies of all 32 condensate species. Finally, we use a three-Parameter Function to provide convenient fits to the shape of the extinction efficiency curve. We show that the errors associated with these simple fits in the Wide Field Camera 3 (WFC3), J, H and K wavebands are $\sim 10\%$. These fits allow for the extinction cross section or opacity of the condensate species to be easily included in retrieval analyses of transmission spectra. We discuss prospects for future experimental work. The compilation of the optical constants and LX-MIE are publicly available as part of the open-source Exoclime Simulation Platform (this http URL).
