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Robert T. Trousdale - One of the best experts on this subject based on the ideXlab platform.
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The Frank Stinchfield Award: muscle damage after total hip arthroplasty done with the two-incision and mini-posterior techniques.
Clinical orthopaedics and related research, 2005Co-Authors: Rodrigo Mardones, Mark W. Pagnano, Joseph P. Nemanich, Robert T. TrousdaleAbstract:Some surgeons have suggested that a minimally invasive two-incision approach allows total hip arthroplasty to be done without cutting or damaging any muscle or tendon. To our knowledge that claim has not been supported by any published clinical or basic science data. Our purpose in doing this study was to quantify the extent and location of damage to the abductor and external rotator muscles and tendons after two-incision and mini-posterior total hip arthroplasty. Ten cadavers (20 hips) were studied. In each cadaver one hip randomly was assigned to the two-incision group and the contralateral hip was assigned to the mini-posterior group. After inserting the total hip arthroplasty components the muscle damage was assessed using a technique described previously. Damage to the muscle of the gluteus medius and gluteus minimus was substantially greater with the two-incision technique than with the mini-posterior technique. Every two-incision total hip replacement caused measurable damage to the abductors, the external Rotators, or both. Every mini-posterior hip replacement caused the external Rotators to detach during the exposure and had additional measurable damage to the abductor muscles and tendon. We do not support the contention that a two-incision total hip arthroplasty is done without cutting muscle or tendon. None of the two-incision hip replacements were done without cutting, reaming, or damaging the gluteus medius or gluteus minimus muscle or external Rotators.
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Muscle damage after total hip arthroplasty done with the two-incision and mini-posterior techniques : The treatment of osteoarthritis of the hip 1920
Clinical Orthopaedics and Related Research, 2005Co-Authors: Rodrigo Mardones, Mark W. Pagnano, Joseph P. Nemanich, Robert T. TrousdaleAbstract:Some surgeons have suggested that a minimally invasive two': incision approach allows total hip arthroplasty to be done without cutting or damaging any muscle or tendon. To our knowledge that claim has not been supported by any published clinical or basic science data. Our purpose in doing this study was to quantify the extent and location of damage to the abductor and external rotator muscles and tendons after two-incision and mini-posterior total hip arthroplasty. Ten cadavers (20 hips) were studied. In each cadaver one hip randomly was assigned to the two-incision group and the contralateral hip was assigned to the mini-posterior group. After inserting the total hip arthroplasty components the muscle damage was assessed using a technique described previously. Damage to the muscle of the gluteus medius and gluteus minimus was substantially greater with the two' incision technique than with the mini-posterior technique. Every two-incision total hip replacement caused measurable damage to the abductors, the external Rotators, or both. Every mini-posterior hip replacement caused the external Rotators to detach during the exposure and had additional measurable damage to the abductor muscles and tendon. We do not support the contention that a two-incision total hip arthroplasty is done without cutting muscle or tendon. None of the two-incision hip replacements were done without cutting, reaming, or damaging the gluteus medius or gluteus minimus muscle or external Rotators.
Nicholas Scott - One of the best experts on this subject based on the ideXlab platform.
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the sami galaxy survey mass as the driver of the kinematic morphology density relation in clusters
The Astrophysical Journal, 2017Co-Authors: Nicholas Scott, Francesco Deugenio, Sarah Brough, Jesse Van De Sande, Matt S Owers, R Sharp, L Cortese, S M CroomAbstract:We examine the kinematic morphology of early-type galaxies (ETGs) in eight galaxy clusters in the Sydney-AAO Multi-object Integral-field spectrograph Galaxy Survey. The clusters cover a mass range of 14.2 < log(M_(200)/M_☉) < 15.2 and we measure spatially resolved stellar kinematics for 315 member galaxies with stellar masses 10.0
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the sami galaxy survey revisiting galaxy classification through high order stellar kinematics
The Astrophysical Journal, 2017Co-Authors: Jesse Van De Sande, Nicholas Scott, Francesco Deugenio, L M R Fogarty, Sarah Brough, L Cortese, S M Croom, Joss Blandhawthorn, J T Allen, Julia J BryantAbstract:Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h_3 (~skewness) and h_4 (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter (λ_(R_e)) and ellipticity (e_e) are used to separate fast and slow Rotators; there exists a good correspondence to regular and non-regular Rotators, respectively, as also seen in earlier studies. We confirm that regular Rotators show a strong h_3 versus V/σ anti-correlation, whereas quasi-regular and non-regular Rotators show a more vertical relation in h_3 and V/σ. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h_3 versus V/σ signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow Rotators, whereas Classes 2–5 correspond to fast Rotators. We find that galaxies with similar λ_(R_e) - e_e values can show distinctly different h_3 - V/σ signatures. Class 5 objects are previously unidentified fast Rotators that show a weak h_3 versus V/σ anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h_3 versus V/σ as evidence for disks in most fast Rotators, suggesting a dearth of gas-poor mergers among fast Rotators.
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the sami galaxy survey revisiting galaxy classification through high order stellar kinematics
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Jesse Van De Sande, Nicholas Scott, Francesco Deugenio, Sarah Brough, L Cortese, S M Croom, Joss Blandhawthorn, J T Allen, Lisa Fogarty, Julia J BryantAbstract:Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h3 (~skewness) and h4 (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using 2D integral field data from the SAMI Galaxy Survey. A proxy for the spin parameter ($\lambda_{R_e}$) and ellipticity ($\epsilon_e$) are used to separate fast and slow Rotators; there exists a good correspondence to regular and non-regular Rotators, respectively, as also seen in earlier studies. We confirm that regular Rotators show a strong h3 versus $V/\sigma$ anti-correlation, whereas quasi-regular and non-regular Rotators show a more vertical relation in h3 and $V/\sigma$. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h3 versus $V/\sigma$ signatures. We identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow Rotators, whereas Classes 2-5 correspond to fast Rotators. We find that galaxies with similar $\lambda_{R_e}-\epsilon_e$ values can show distinctly different h3-$V/\sigma$ signatures. Class 5 objects are previously unidentified fast Rotators that show a weak h3 versus $V/\sigma$ anti-correlation. These objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h3 versus $V/\sigma$ as evidence for disks in most fast Rotators, suggesting a dearth of gas-poor mergers among fast Rotators.
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distribution of slow and fast Rotators in the fornax cluster
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: Nicholas Scott, Roger L Davies, Ryan C W Houghton, Michele Cappellari, Alister W Graham, Kevin A PimbbletAbstract:We present integral field spectroscopy of 10 early-type galaxies in the nearby, low-mass, Fornax cluster, from which we derive spatially resolved stellar kinematics. Based on the morphologies of their stellar velocity maps we classify 2/10 galaxies as slow Rotators, with the remaining eight galaxies fast Rotators. Supplementing our integral field observations with morphological and kinematic data from the literature, we analyse the 'kinematic' type of all 30 galaxies in the Fornax cluster brighter than MK = -21.5 mag (M* ~ 6 × 109 M⊙). Our sample's slow rotator fraction within one virial radius is 7-6+4 per cent. 13-6+8 per cent of the early-type galaxies are slow Rotators, consistent with the observed fraction in other galaxy aggregates. The fraction of slow Rotators in Fornax varies with cluster-centric radius, rising to 16-8+11 per cent of all kinematic types within the central 0.2 virial radii, from 0 per cent in the cluster outskirts. We find that, even in mass-matched samples of slow and fast Rotators, slow Rotators are found preferentially at higher projected environmental density than fast Rotators. This demonstrates that dynamical friction alone cannot be responsible for the differing distributions of slow and fast Rotators. For dynamical friction to play a significant role, slow Rotators must reside in higher mass sub-haloes than fast Rotators and/or form in the centres of groups before being accreted on to the cluster. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
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fast and slow Rotators in the densest environments a swift ifs study of the coma cluster
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: Ryan C W Houghton, Nicholas Scott, Roger L Davies, Francesco Deugenio, N Thatte, Fraser Clarke, M Tecza, G Salter, L M R Fogarty, Timothy GoodsallAbstract:We present integral-field spectroscopy of 27 galaxies in the Coma cluster observed with the Oxford SWIFT spectrograph, exploring the kinematic morphology-density relationship in a cluster environment richer and denser than any in the ATLAS3D survey. Our new data enables comparison of the kinematic morphology relation in three very different clusters (Virgo, Coma and Abell 1689) as well as to the field/group environment. The Coma sample was selected to match the parent luminosity and ellipticity distributions of the early-type population within a radius 15' (0.43 Mpc) of the cluster centre, and is limited to r' = 16 mag (equivalent to M_K = -21.5 mag), sampling one third of that population. From analysis of the lambda-ellipticity diagram, we find 15+-6% of early-type galaxies are slow Rotators; this is identical to the fraction found in the field and the average fraction in the Virgo cluster, based on the ATLAS3D data. It is also identical to the average fraction found recently in Abell 1689 by D'Eugenio et al.. Thus it appears that the average slow rotator fraction of early type galaxies remains remarkably constant across many different environments, spanning five orders of magnitude in galaxy number density. However, within each cluster the slow Rotators are generally found in regions of higher projected density, possibly as a result of mass segregation by dynamical friction. These results provide firm constraints on the mechanisms that produce early-type galaxies: they must maintain a fixed ratio between the number of fast Rotators and slow Rotators while also allowing the total early-type fraction to increase in clusters relative to the field. A complete survey of Coma, sampling hundreds rather than tens of galaxies, could probe a more representative volume of Coma and provide significantly stronger constraints, particularly on how the slow rotator fraction varies at larger radii.
Keiji Ohtsuki - One of the best experts on this subject based on the ideXlab platform.
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a multilayer model for thermal infrared emission of saturn s rings iii thermal inertia inferred from cassini cirs
Icarus, 2011Co-Authors: Ryuji Morishima, Linda Spilker, Keiji OhtsukiAbstract:Abstract The thermal inertia values of Saturn’s main rings (the A, B, and C rings and the Cassini division) are derived by applying our thermal model to azimuthally scanned spectra taken by the Cassini Composite Infrared Spectrometer (CIRS). Model fits show the thermal inertia of ring particles to be 16, 13, 20, and 11 J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. However, there are systematic deviations between modeled and observed temperatures in Saturn’s shadow depending on solar phase angle, and these deviations indicate that the apparent thermal inertia increases with solar phase angle. This dependence is likely to be explained if large slowly spinning particles have lower thermal inertia values than those for small fast spinning particles because the thermal emission of slow Rotators is relatively stronger than that of fast Rotators at low phase and vise versa. Additional parameter fits, which assume that slow and fast Rotators have different thermal inertia values, show the derived thermal inertia values of slow (fast) Rotators to be 8 (77), 8 (27), 9 (34), 5 (55) J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. The values for fast Rotators are still much smaller than those for solid ice with no porosity. Thus, fast Rotators are likely to have surface regolith layers, but these may not be as fluffy as those for slow Rotators, probably because the capability of holding regolith particles is limited for fast Rotators due to the strong centrifugal force on surfaces of fast Rotators. Other additional parameter fits, in which radii of fast Rotators are varied, indicate that particles less than ∼1 cm should not occupy more than roughly a half of the cross section for the A, B, and C rings.
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A multilayer model for thermal infrared emission of Saturn’s rings. III: Thermal inertia inferred from Cassini CIRS
Icarus, 2011Co-Authors: Ryuji Morishima, Linda Spilker, Keiji OhtsukiAbstract:Abstract The thermal inertia values of Saturn’s main rings (the A, B, and C rings and the Cassini division) are derived by applying our thermal model to azimuthally scanned spectra taken by the Cassini Composite Infrared Spectrometer (CIRS). Model fits show the thermal inertia of ring particles to be 16, 13, 20, and 11 J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. However, there are systematic deviations between modeled and observed temperatures in Saturn’s shadow depending on solar phase angle, and these deviations indicate that the apparent thermal inertia increases with solar phase angle. This dependence is likely to be explained if large slowly spinning particles have lower thermal inertia values than those for small fast spinning particles because the thermal emission of slow Rotators is relatively stronger than that of fast Rotators at low phase and vise versa. Additional parameter fits, which assume that slow and fast Rotators have different thermal inertia values, show the derived thermal inertia values of slow (fast) Rotators to be 8 (77), 8 (27), 9 (34), 5 (55) J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. The values for fast Rotators are still much smaller than those for solid ice with no porosity. Thus, fast Rotators are likely to have surface regolith layers, but these may not be as fluffy as those for slow Rotators, probably because the capability of holding regolith particles is limited for fast Rotators due to the strong centrifugal force on surfaces of fast Rotators. Other additional parameter fits, in which radii of fast Rotators are varied, indicate that particles less than ∼1 cm should not occupy more than roughly a half of the cross section for the A, B, and C rings.
Francesco Deugenio - One of the best experts on this subject based on the ideXlab platform.
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stellar kinematics and environment at z 0 8 in the lega c survey massive slow Rotators are built first in overdense environments
The Astrophysical Journal, 2020Co-Authors: Justin Cole, Francesco Deugenio, Rachel Bezanson, Arjen Van Der Wel, Eric F Bell, Marijn Franx, Anna Gallazzi, Josha Van Houdt, Adam Muzzin, Camilla PacificiAbstract:In this Letter, we investigate the impact of environment on integrated and spatially resolved stellar kinematics of a sample of massive, quiescent galaxies at intermediate redshift (0.6 < z < 1.0). For this analysis, we combine photometric and spectroscopic parameters from the UltraVISTA and Large Early Galaxy Astrophysics Census surveys in the COSMOS field and environmental measurements. We analyze the trends with overdensity (1+δ) on the rotational support of quiescent galaxies and find no universal trends at either fixed mass or fixed stellar velocity dispersion. This is consistent with previous studies of the local universe; rotational support of massive galaxies depends primarily on stellar mass. We highlight two populations of massive galaxies () that deviate from the average mass relation. First, the most massive galaxies in the most underdense regions ((1 + δ) ≤ 1) exhibit elevated rotational support. Similarly, at the highest masses () the range in rotational support is significant in all but the densest regions. This corresponds to an increasing slow-rotator fraction such that only galaxies in the densest environments ((1 + δ) ≥ 3.5) are primarily (90% ± 10%) slow Rotators. This effect is not seen at fixed velocity dispersion, suggesting minor merging as the driving mechanism: Only in the densest regions have the most massive galaxies experienced significant minor merging, building stellar mass and diminishing rotation without significantly affecting the central stellar velocity dispersion. In the local universe, most massive galaxies are slow Rotators, regardless of environment, suggesting minor merging occurs at later cosmic times (z ≲ 0.6) in all but the most dense environments.
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the sami galaxy survey mass as the driver of the kinematic morphology density relation in clusters
The Astrophysical Journal, 2017Co-Authors: Nicholas Scott, Francesco Deugenio, Sarah Brough, Jesse Van De Sande, Matt S Owers, R Sharp, L Cortese, S M CroomAbstract:We examine the kinematic morphology of early-type galaxies (ETGs) in eight galaxy clusters in the Sydney-AAO Multi-object Integral-field spectrograph Galaxy Survey. The clusters cover a mass range of 14.2 < log(M_(200)/M_☉) < 15.2 and we measure spatially resolved stellar kinematics for 315 member galaxies with stellar masses 10.0
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the sami galaxy survey revisiting galaxy classification through high order stellar kinematics
The Astrophysical Journal, 2017Co-Authors: Jesse Van De Sande, Nicholas Scott, Francesco Deugenio, L M R Fogarty, Sarah Brough, L Cortese, S M Croom, Joss Blandhawthorn, J T Allen, Julia J BryantAbstract:Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h_3 (~skewness) and h_4 (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using two-dimensional integral field data from the SAMI Galaxy Survey. Proxies for the spin parameter (λ_(R_e)) and ellipticity (e_e) are used to separate fast and slow Rotators; there exists a good correspondence to regular and non-regular Rotators, respectively, as also seen in earlier studies. We confirm that regular Rotators show a strong h_3 versus V/σ anti-correlation, whereas quasi-regular and non-regular Rotators show a more vertical relation in h_3 and V/σ. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h_3 versus V/σ signatures. Within the SAMI Galaxy Survey, we identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow Rotators, whereas Classes 2–5 correspond to fast Rotators. We find that galaxies with similar λ_(R_e) - e_e values can show distinctly different h_3 - V/σ signatures. Class 5 objects are previously unidentified fast Rotators that show a weak h_3 versus V/σ anti-correlation. From simulations, these objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h_3 versus V/σ as evidence for disks in most fast Rotators, suggesting a dearth of gas-poor mergers among fast Rotators.
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the sami galaxy survey revisiting galaxy classification through high order stellar kinematics
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Jesse Van De Sande, Nicholas Scott, Francesco Deugenio, Sarah Brough, L Cortese, S M Croom, Joss Blandhawthorn, J T Allen, Lisa Fogarty, Julia J BryantAbstract:Recent cosmological hydrodynamical simulations suggest that integral field spectroscopy can connect the high-order stellar kinematic moments h3 (~skewness) and h4 (~kurtosis) in galaxies to their cosmological assembly history. Here, we assess these results by measuring the stellar kinematics on a sample of 315 galaxies, without a morphological selection, using 2D integral field data from the SAMI Galaxy Survey. A proxy for the spin parameter ($\lambda_{R_e}$) and ellipticity ($\epsilon_e$) are used to separate fast and slow Rotators; there exists a good correspondence to regular and non-regular Rotators, respectively, as also seen in earlier studies. We confirm that regular Rotators show a strong h3 versus $V/\sigma$ anti-correlation, whereas quasi-regular and non-regular Rotators show a more vertical relation in h3 and $V/\sigma$. Motivated by recent cosmological simulations, we develop an alternative approach to kinematically classify galaxies from their individual h3 versus $V/\sigma$ signatures. We identify five classes of high-order stellar kinematic signatures using Gaussian mixture models. Class 1 corresponds to slow Rotators, whereas Classes 2-5 correspond to fast Rotators. We find that galaxies with similar $\lambda_{R_e}-\epsilon_e$ values can show distinctly different h3-$V/\sigma$ signatures. Class 5 objects are previously unidentified fast Rotators that show a weak h3 versus $V/\sigma$ anti-correlation. These objects are predicted to be disk-less galaxies formed by gas-poor mergers. From morphological examination, however, there is evidence for large stellar disks. Instead, Class 5 objects are more likely disturbed galaxies, have counter-rotating bulges, or bars in edge-on galaxies. Finally, we interpret the strong anti-correlation in h3 versus $V/\sigma$ as evidence for disks in most fast Rotators, suggesting a dearth of gas-poor mergers among fast Rotators.
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fast and slow Rotators in the densest environments a swift ifs study of the coma cluster
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: Ryan C W Houghton, Nicholas Scott, Roger L Davies, Francesco Deugenio, N Thatte, Fraser Clarke, M Tecza, G Salter, L M R Fogarty, Timothy GoodsallAbstract:We present integral-field spectroscopy of 27 galaxies in the Coma cluster observed with the Oxford SWIFT spectrograph, exploring the kinematic morphology-density relationship in a cluster environment richer and denser than any in the ATLAS3D survey. Our new data enables comparison of the kinematic morphology relation in three very different clusters (Virgo, Coma and Abell 1689) as well as to the field/group environment. The Coma sample was selected to match the parent luminosity and ellipticity distributions of the early-type population within a radius 15' (0.43 Mpc) of the cluster centre, and is limited to r' = 16 mag (equivalent to M_K = -21.5 mag), sampling one third of that population. From analysis of the lambda-ellipticity diagram, we find 15+-6% of early-type galaxies are slow Rotators; this is identical to the fraction found in the field and the average fraction in the Virgo cluster, based on the ATLAS3D data. It is also identical to the average fraction found recently in Abell 1689 by D'Eugenio et al.. Thus it appears that the average slow rotator fraction of early type galaxies remains remarkably constant across many different environments, spanning five orders of magnitude in galaxy number density. However, within each cluster the slow Rotators are generally found in regions of higher projected density, possibly as a result of mass segregation by dynamical friction. These results provide firm constraints on the mechanisms that produce early-type galaxies: they must maintain a fixed ratio between the number of fast Rotators and slow Rotators while also allowing the total early-type fraction to increase in clusters relative to the field. A complete survey of Coma, sampling hundreds rather than tens of galaxies, could probe a more representative volume of Coma and provide significantly stronger constraints, particularly on how the slow rotator fraction varies at larger radii.
Ryuji Morishima - One of the best experts on this subject based on the ideXlab platform.
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a multilayer model for thermal infrared emission of saturn s rings iii thermal inertia inferred from cassini cirs
Icarus, 2011Co-Authors: Ryuji Morishima, Linda Spilker, Keiji OhtsukiAbstract:Abstract The thermal inertia values of Saturn’s main rings (the A, B, and C rings and the Cassini division) are derived by applying our thermal model to azimuthally scanned spectra taken by the Cassini Composite Infrared Spectrometer (CIRS). Model fits show the thermal inertia of ring particles to be 16, 13, 20, and 11 J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. However, there are systematic deviations between modeled and observed temperatures in Saturn’s shadow depending on solar phase angle, and these deviations indicate that the apparent thermal inertia increases with solar phase angle. This dependence is likely to be explained if large slowly spinning particles have lower thermal inertia values than those for small fast spinning particles because the thermal emission of slow Rotators is relatively stronger than that of fast Rotators at low phase and vise versa. Additional parameter fits, which assume that slow and fast Rotators have different thermal inertia values, show the derived thermal inertia values of slow (fast) Rotators to be 8 (77), 8 (27), 9 (34), 5 (55) J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. The values for fast Rotators are still much smaller than those for solid ice with no porosity. Thus, fast Rotators are likely to have surface regolith layers, but these may not be as fluffy as those for slow Rotators, probably because the capability of holding regolith particles is limited for fast Rotators due to the strong centrifugal force on surfaces of fast Rotators. Other additional parameter fits, in which radii of fast Rotators are varied, indicate that particles less than ∼1 cm should not occupy more than roughly a half of the cross section for the A, B, and C rings.
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A multilayer model for thermal infrared emission of Saturn’s rings. III: Thermal inertia inferred from Cassini CIRS
Icarus, 2011Co-Authors: Ryuji Morishima, Linda Spilker, Keiji OhtsukiAbstract:Abstract The thermal inertia values of Saturn’s main rings (the A, B, and C rings and the Cassini division) are derived by applying our thermal model to azimuthally scanned spectra taken by the Cassini Composite Infrared Spectrometer (CIRS). Model fits show the thermal inertia of ring particles to be 16, 13, 20, and 11 J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. However, there are systematic deviations between modeled and observed temperatures in Saturn’s shadow depending on solar phase angle, and these deviations indicate that the apparent thermal inertia increases with solar phase angle. This dependence is likely to be explained if large slowly spinning particles have lower thermal inertia values than those for small fast spinning particles because the thermal emission of slow Rotators is relatively stronger than that of fast Rotators at low phase and vise versa. Additional parameter fits, which assume that slow and fast Rotators have different thermal inertia values, show the derived thermal inertia values of slow (fast) Rotators to be 8 (77), 8 (27), 9 (34), 5 (55) J m −2 K −1 s −1/2 for the A, B, and C rings, and the Cassini division, respectively. The values for fast Rotators are still much smaller than those for solid ice with no porosity. Thus, fast Rotators are likely to have surface regolith layers, but these may not be as fluffy as those for slow Rotators, probably because the capability of holding regolith particles is limited for fast Rotators due to the strong centrifugal force on surfaces of fast Rotators. Other additional parameter fits, in which radii of fast Rotators are varied, indicate that particles less than ∼1 cm should not occupy more than roughly a half of the cross section for the A, B, and C rings.
