The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Charles J. Lada - One of the best experts on this subject based on the ideXlab platform.
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Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68
The Astrophysical Journal, 2007Co-Authors: Sébastien Maret, Edwin A. Bergin, Charles J. LadaAbstract:We present observations of 13CO, C18O, HCO+, H13CO+, DCO+ and N2H+ line emission towards the Barnard 68 starless core. The line Profiles are interpreted using a chemical network coupled with a radiative transfer code in order to reconstruct the Radial Velocity Profile of the core. Our observations and modeling indicate the presence of complex Radial motions, with the inward motions in the outer layers of the core but outward motions in the inner part, suggesting Radial oscillations. The presence of such oscillation would imply that B68 is relatively old, typically one order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the Radial Velocity Profiles of starless cores.
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Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68
The Astrophysical Journal, 2007Co-Authors: Sébastien Maret, Edwin A. Bergin, Charles J. LadaAbstract:We present observations of 13CO, C18O, HCO+, H13CO+, DCO+, and N2H+ line emission toward the Barnard 68 starless core. The line Profiles are interpreted by use of a chemical network coupled with a radiative transfer code, in order to reconstruct the Radial Velocity Profile of the core. Our observations and modeling indicate the presence of complex Radial motions, with inward motions in the outer layers of the core but outward motions in the inner layers of the core, suggesting Radial oscillations. The presence of such oscillations would imply that the Barnard 68 starless core is relatively old, typically 1 order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the Radial Velocity Profiles of starless cores.
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USING CHEMISTRY TO UNVEIL THE KINEMATICS OF STARLESS CORES: COMPLEX Radial MOTIONS
2007Co-Authors: Edwin Bergin, Charles J. LadaAbstract:We present observations of 13 CO, C 18 O, HCO ,H 13 CO, DCO, and N2H line emission toward the Barnard 68 starless core. The line Profiles are interpreted by use of a chemical network coupled with a radiative transfer code, in order to reconstruct the Radial Velocity Profile of the core. Our observations and modeling indicate the presence of complex Radial motions, with inward motions in the outer layers of the core but outward motions in the inner layers of the core, suggesting Radial oscillations. The presence of such oscillations would imply that the Barnard 68 starless core is relatively old, typically 1 order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the Radial Velocity Profiles of starless cores. Subject headings: astrochemistry — ISM: abundances — ISM: individual (Barnard 68) — ISM: molecules — stars: formation
Soo-chang Rey - One of the best experts on this subject based on the ideXlab platform.
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A Bound Violation on the Galaxy Group Scale: The Turn-around Radius of NGC 5353/4
The Astrophysical Journal, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The first observational evidence for the violation of the maximum turn-around radius on the galaxy group scale is presented. The NGC 5353/4 group is chosen as an ideal target for our investigation of the bound-violation because of its proximity, low-density environment, optimal mass scale, and existence of a nearby thin straight filament. Using the observational data on the line-of-sight velocities and three-dimensional distances of the filament galaxies located in the bound zone of the NGC 5353/4 group, we construct their Radial Velocity Profile as a function of separation distance from the group center and then compare it to the analytic formula obtained empirically by Falco et al. (2014) to find the best-fit value of an adjustable parameter with the help of the maximum likelihood method. The turn-around radius of NGC 5353/4 is determined to be the separation distance where the adjusted analytic formula for the Radial Velocity Profile yields zero. The estimated turn-around radius of NGC 5353/4 turns out to substantially exceed the upper limit predicted by the spherical model based on the LambdaCDM cosmology. Even when the restrictive condition of spherical symmetry is released, the estimated value is found to be only marginally consistent with the LambdaCDM expectation.
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A NEW DYNAMICAL MASS MEASUREMENT FOR THE VIRGO CLUSTER USING THE Radial Velocity Profile OF THE FILAMENT GALAXIES
The Astrophysical Journal, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The Radial velocities of the galaxies in the vicinity of a cluster show deviation from the pure Hubble flow due to their gravitational interaction with the cluster. According to a recent study by Falco et al. based on a high-resolution N-body simulation, the Radial Velocity Profile of galaxies located at distances larger than three times the virial radius of a neighboring cluster can be well approximated by a universal formula, and could be reconstructed from direct observables provided that the galaxies are distributed along a one-dimensional filament. They suggested an algorithm designed to estimate the dynamic mass of a cluster by fitting the universal formula from the simulation to the reconstructed Radial Velocity Profile of the filament galaxies around the cluster from observations. We apply the algorithm to two narrow, straight filaments (referred to as Filaments A and B) that were recently identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog. The dynamical mass of the Virgo cluster is estimated to be and for the cases of Filaments A and B, respectively. We discuss the observational and theoretical systematics intrinsic to the method of Falco et al. as well as the physical implication of the final results.
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The Radial Velocity Profile of the filament galaxies in the vicinity of the Virgo cluster as a test of gravity
arXiv: Cosmology and Nongalactic Astrophysics, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The Radial velocities of the galaxies in the vicinity of a massive cluster shows deviation from the pure Hubble flow due to their gravitational interaction with the cluster. According to a recent study of Falco et al. with a high-resolution N-body simulation based on General Relativity (GR), the Radial Velocity Profile of the galaxies located at distances larger than three times the virial radius of a neighbour cluster has a universal shape and could be reconstructed from direct observables provided that the galaxies are distributed along one dimensional filament. Analyzing the narrow filamentary structure identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog, we reconstruct the Radial Velocity Profile of the Virgo filament galaxies and compare it with the universal formula derived by Falco et al. It is found that unless the virial mass of the Virgo cluster exceeds $10^{15}\,h^{-1}M_{\odot}$ the universal formula fails to describe the reconstructed Radial Velocity Profile whose peculiar Velocity term turns out to decrease much less rapidly. Speculating that the disagreement between the GR prediction and the observed Radial Velocity Profile of the Virgo filament galaxies may be due to the presence of unscreened fifth force, we suggest the Radial Velocity Profile of the filament galaxies around the clusters as a powerful test of gravity on the cosmological scale.
Stephane Roux - One of the best experts on this subject based on the ideXlab platform.
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shear with comminution of a granular material microscopic deformations outside the shear band
Physical Review E, 2003Co-Authors: Guillaume Chambon, Jean Schmittbuhl, Alain Corfdir, Jeanpierre Vilotte, Stephane RouxAbstract:tion of the strain rapidly forms a shear band ~seven particles wide! in which comminution develops. We focused on the strain field outside this shear band and observed a rich dynamics of large and intermittent mechanical clusters ~up to 50 particles wide!. Quantitative description of the Radial Velocity Profile outside the shear band reveals an exponential decrease. However, a significant slip evolution of the associated characteristic length is observed, indicative of a slow decoupling between the shear band and the rest of the sample. This slow evolution is shown to be well described by power laws with the imposed slip, and has important implications for friction laws and earthquake physics.
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Shear with comminution of a granular material: Microscopic deformations outside the shear band
Physical Review E, 2003Co-Authors: Guillaume Chambon, Jean Schmittbuhl, Alain Corfdir, Jeanpierre Vilotte, Stephane RouxAbstract:A correlation imaging velocimetry technique is applied to recover displacement fields in a granular material subjected to extended shear. A thick (10 cm) annular sand sample (grain size: 1 mm) is confined at constant pressure (σ=0.5MPa) against a rough moving wall displacing at very low speed (˙δ=83μms−1). Localization of the strain rapidly forms a shear band (seven particles wide) in which comminution develops. We focused on the strain field outside this shear band and observed a rich dynamics of large and intermittent mechanical clusters (up to 50 particles wide). Quantitative description of the Radial Velocity Profile outside the shear band reveals an exponential decrease. However, a significant slip evolution of the associated characteristic length is observed, indicative of a slow decoupling between the shear band and the rest of the sample. This slow evolution is shown to be well described by power laws with the imposed slip, and has important implications for friction laws and earthquake physics.
Sébastien Maret - One of the best experts on this subject based on the ideXlab platform.
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Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68
The Astrophysical Journal, 2007Co-Authors: Sébastien Maret, Edwin A. Bergin, Charles J. LadaAbstract:We present observations of 13CO, C18O, HCO+, H13CO+, DCO+ and N2H+ line emission towards the Barnard 68 starless core. The line Profiles are interpreted using a chemical network coupled with a radiative transfer code in order to reconstruct the Radial Velocity Profile of the core. Our observations and modeling indicate the presence of complex Radial motions, with the inward motions in the outer layers of the core but outward motions in the inner part, suggesting Radial oscillations. The presence of such oscillation would imply that B68 is relatively old, typically one order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the Radial Velocity Profiles of starless cores.
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Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68
The Astrophysical Journal, 2007Co-Authors: Sébastien Maret, Edwin A. Bergin, Charles J. LadaAbstract:We present observations of 13CO, C18O, HCO+, H13CO+, DCO+, and N2H+ line emission toward the Barnard 68 starless core. The line Profiles are interpreted by use of a chemical network coupled with a radiative transfer code, in order to reconstruct the Radial Velocity Profile of the core. Our observations and modeling indicate the presence of complex Radial motions, with inward motions in the outer layers of the core but outward motions in the inner layers of the core, suggesting Radial oscillations. The presence of such oscillations would imply that the Barnard 68 starless core is relatively old, typically 1 order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the Radial Velocity Profiles of starless cores.
Jounghun Lee - One of the best experts on this subject based on the ideXlab platform.
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A Bound Violation on the Galaxy Group Scale: The Turn-around Radius of NGC 5353/4
The Astrophysical Journal, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The first observational evidence for the violation of the maximum turn-around radius on the galaxy group scale is presented. The NGC 5353/4 group is chosen as an ideal target for our investigation of the bound-violation because of its proximity, low-density environment, optimal mass scale, and existence of a nearby thin straight filament. Using the observational data on the line-of-sight velocities and three-dimensional distances of the filament galaxies located in the bound zone of the NGC 5353/4 group, we construct their Radial Velocity Profile as a function of separation distance from the group center and then compare it to the analytic formula obtained empirically by Falco et al. (2014) to find the best-fit value of an adjustable parameter with the help of the maximum likelihood method. The turn-around radius of NGC 5353/4 is determined to be the separation distance where the adjusted analytic formula for the Radial Velocity Profile yields zero. The estimated turn-around radius of NGC 5353/4 turns out to substantially exceed the upper limit predicted by the spherical model based on the LambdaCDM cosmology. Even when the restrictive condition of spherical symmetry is released, the estimated value is found to be only marginally consistent with the LambdaCDM expectation.
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A NEW DYNAMICAL MASS MEASUREMENT FOR THE VIRGO CLUSTER USING THE Radial Velocity Profile OF THE FILAMENT GALAXIES
The Astrophysical Journal, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The Radial velocities of the galaxies in the vicinity of a cluster show deviation from the pure Hubble flow due to their gravitational interaction with the cluster. According to a recent study by Falco et al. based on a high-resolution N-body simulation, the Radial Velocity Profile of galaxies located at distances larger than three times the virial radius of a neighboring cluster can be well approximated by a universal formula, and could be reconstructed from direct observables provided that the galaxies are distributed along a one-dimensional filament. They suggested an algorithm designed to estimate the dynamic mass of a cluster by fitting the universal formula from the simulation to the reconstructed Radial Velocity Profile of the filament galaxies around the cluster from observations. We apply the algorithm to two narrow, straight filaments (referred to as Filaments A and B) that were recently identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog. The dynamical mass of the Virgo cluster is estimated to be and for the cases of Filaments A and B, respectively. We discuss the observational and theoretical systematics intrinsic to the method of Falco et al. as well as the physical implication of the final results.
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The Radial Velocity Profile of the filament galaxies in the vicinity of the Virgo cluster as a test of gravity
arXiv: Cosmology and Nongalactic Astrophysics, 2015Co-Authors: Jounghun Lee, Suk Kim, Soo-chang ReyAbstract:The Radial velocities of the galaxies in the vicinity of a massive cluster shows deviation from the pure Hubble flow due to their gravitational interaction with the cluster. According to a recent study of Falco et al. with a high-resolution N-body simulation based on General Relativity (GR), the Radial Velocity Profile of the galaxies located at distances larger than three times the virial radius of a neighbour cluster has a universal shape and could be reconstructed from direct observables provided that the galaxies are distributed along one dimensional filament. Analyzing the narrow filamentary structure identified by Kim et al. in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog, we reconstruct the Radial Velocity Profile of the Virgo filament galaxies and compare it with the universal formula derived by Falco et al. It is found that unless the virial mass of the Virgo cluster exceeds $10^{15}\,h^{-1}M_{\odot}$ the universal formula fails to describe the reconstructed Radial Velocity Profile whose peculiar Velocity term turns out to decrease much less rapidly. Speculating that the disagreement between the GR prediction and the observed Radial Velocity Profile of the Virgo filament galaxies may be due to the presence of unscreened fifth force, we suggest the Radial Velocity Profile of the filament galaxies around the clusters as a powerful test of gravity on the cosmological scale.
