The Experts below are selected from a list of 522 Experts worldwide ranked by ideXlab platform
Junhui Zhao - One of the best experts on this subject based on the ideXlab platform.
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dynamics of ionized gas at the galactic center very large array observations of the three dimensional velocity field and location of the ionized streams in sagittarius a west
The Astrophysical Journal, 2009Co-Authors: Junhui Zhao, M Morris, W M Goss, Tao AnAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact H II components in the central 80 '' (3 pc, assuming D = 8 pc). Using VLA archival data for the H92 alpha radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to -415 km s(-1). Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each of the observed streams of ionized gas follows a single orbit, we determined the five orbital parameters (a, e, Omega, omega, i) for each of them using least-square fitting to the loci of the streams. The degeneracy in the orbital solutions for both the direction of flow and the two mirror images can be further resolved using the information obtained from the velocity measurements. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. All three are confined within the central 3 pc. Both the Northern and Eastern Arm streams have high eccentricities (e = 0.83 +/- 0.10 and 0.82 +/- 0.05, respectively), while the Western Arc stream is nearly circular, with e = 0.2 +/- 0.15. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth) and have orbital periods in the range 4-8x10(4) yr. To verify the fit, the distributions of radial and transverse velocity vectors in Sgr A West were also computed using the Keplerian model and they show good agreement with both the proper motion and radial velocity data. In addition, the computed orbits suggest that the Northern and Eastern Arm streams may collide in the "Bar" region (a few arcsec south of Sgr A*) and that most of the orbiting ionized gas in the "Bar" region is located behind Sgr A*. We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near infrared observations. From the H92a line data, we find evidence of substantial interaction between the IRS 8 nebula and the Northern Arm stream occurring in the bow-shock region. Other new morphological features revealed in our high-resolution image include (1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field, and (2) a linear feature in the IRS 16 region, suggesting that the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
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dynamics of ionized gas at the galactic center vla observations of the 3d velocity field and location of the ionized streams in sagittarius a west
arXiv: Astrophysics of Galaxies, 2009Co-Authors: Junhui Zhao, M Morris, W M GossAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the VLA at 1.3 cm. We measured proper motions for 71 compact HII components. We also investigated radial velocities in the LSR velocity using the H92a line data. Combining proper motion and radial velocity measurements, we have determined the 3D velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) can be modeled with three bundles of Keplerian orbits around Sgr A*. We determined the five orbital parameters for each of them using LSQ fitting to the locii of the streams. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. Both the Northern and Eastern Arm streams have high eccentricities, while the Western Arc stream is nearly circular. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth). We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near IR observations. From the H92a line data, we find evidence for interaction between the IRS 8 nebula and the Northern Arm stream. Other new morphological features revealed in our high-resolution image include: 1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field and 2) a linear feature in the IRS 16 region, suggesting the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
Tao An - One of the best experts on this subject based on the ideXlab platform.
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dynamics of ionized gas at the galactic center very large array observations of the three dimensional velocity field and location of the ionized streams in sagittarius a west
The Astrophysical Journal, 2009Co-Authors: Junhui Zhao, M Morris, W M Goss, Tao AnAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact H II components in the central 80 '' (3 pc, assuming D = 8 pc). Using VLA archival data for the H92 alpha radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to -415 km s(-1). Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each of the observed streams of ionized gas follows a single orbit, we determined the five orbital parameters (a, e, Omega, omega, i) for each of them using least-square fitting to the loci of the streams. The degeneracy in the orbital solutions for both the direction of flow and the two mirror images can be further resolved using the information obtained from the velocity measurements. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. All three are confined within the central 3 pc. Both the Northern and Eastern Arm streams have high eccentricities (e = 0.83 +/- 0.10 and 0.82 +/- 0.05, respectively), while the Western Arc stream is nearly circular, with e = 0.2 +/- 0.15. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth) and have orbital periods in the range 4-8x10(4) yr. To verify the fit, the distributions of radial and transverse velocity vectors in Sgr A West were also computed using the Keplerian model and they show good agreement with both the proper motion and radial velocity data. In addition, the computed orbits suggest that the Northern and Eastern Arm streams may collide in the "Bar" region (a few arcsec south of Sgr A*) and that most of the orbiting ionized gas in the "Bar" region is located behind Sgr A*. We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near infrared observations. From the H92a line data, we find evidence of substantial interaction between the IRS 8 nebula and the Northern Arm stream occurring in the bow-shock region. Other new morphological features revealed in our high-resolution image include (1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field, and (2) a linear feature in the IRS 16 region, suggesting that the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
W M Goss - One of the best experts on this subject based on the ideXlab platform.
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dynamics of ionized gas at the galactic center very large array observations of the three dimensional velocity field and location of the ionized streams in sagittarius a west
The Astrophysical Journal, 2009Co-Authors: Junhui Zhao, M Morris, W M Goss, Tao AnAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact H II components in the central 80 '' (3 pc, assuming D = 8 pc). Using VLA archival data for the H92 alpha radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to -415 km s(-1). Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each of the observed streams of ionized gas follows a single orbit, we determined the five orbital parameters (a, e, Omega, omega, i) for each of them using least-square fitting to the loci of the streams. The degeneracy in the orbital solutions for both the direction of flow and the two mirror images can be further resolved using the information obtained from the velocity measurements. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. All three are confined within the central 3 pc. Both the Northern and Eastern Arm streams have high eccentricities (e = 0.83 +/- 0.10 and 0.82 +/- 0.05, respectively), while the Western Arc stream is nearly circular, with e = 0.2 +/- 0.15. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth) and have orbital periods in the range 4-8x10(4) yr. To verify the fit, the distributions of radial and transverse velocity vectors in Sgr A West were also computed using the Keplerian model and they show good agreement with both the proper motion and radial velocity data. In addition, the computed orbits suggest that the Northern and Eastern Arm streams may collide in the "Bar" region (a few arcsec south of Sgr A*) and that most of the orbiting ionized gas in the "Bar" region is located behind Sgr A*. We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near infrared observations. From the H92a line data, we find evidence of substantial interaction between the IRS 8 nebula and the Northern Arm stream occurring in the bow-shock region. Other new morphological features revealed in our high-resolution image include (1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field, and (2) a linear feature in the IRS 16 region, suggesting that the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
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dynamics of ionized gas at the galactic center vla observations of the 3d velocity field and location of the ionized streams in sagittarius a west
arXiv: Astrophysics of Galaxies, 2009Co-Authors: Junhui Zhao, M Morris, W M GossAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the VLA at 1.3 cm. We measured proper motions for 71 compact HII components. We also investigated radial velocities in the LSR velocity using the H92a line data. Combining proper motion and radial velocity measurements, we have determined the 3D velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) can be modeled with three bundles of Keplerian orbits around Sgr A*. We determined the five orbital parameters for each of them using LSQ fitting to the locii of the streams. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. Both the Northern and Eastern Arm streams have high eccentricities, while the Western Arc stream is nearly circular. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth). We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near IR observations. From the H92a line data, we find evidence for interaction between the IRS 8 nebula and the Northern Arm stream. Other new morphological features revealed in our high-resolution image include: 1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field and 2) a linear feature in the IRS 16 region, suggesting the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
M Morris - One of the best experts on this subject based on the ideXlab platform.
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dynamics of ionized gas at the galactic center very large array observations of the three dimensional velocity field and location of the ionized streams in sagittarius a west
The Astrophysical Journal, 2009Co-Authors: Junhui Zhao, M Morris, W M Goss, Tao AnAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the Very Large Array (VLA) at 1.3 cm. By combining recent observations with those made at earlier epochs with the VLA at wavelengths of 1.3 and 3.6 cm, we measured proper motions for 71 compact H II components in the central 80 '' (3 pc, assuming D = 8 pc). Using VLA archival data for the H92 alpha radio recombination line, we also investigated radial velocities in the LSR velocity range from +200 to -415 km s(-1). Combining proper motion and radial velocity measurements, we have determined the three-dimensional velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) in the central 3 pc can be modeled with three bundles of Keplerian orbits around Sgr A*. Assuming that each of the observed streams of ionized gas follows a single orbit, we determined the five orbital parameters (a, e, Omega, omega, i) for each of them using least-square fitting to the loci of the streams. The degeneracy in the orbital solutions for both the direction of flow and the two mirror images can be further resolved using the information obtained from the velocity measurements. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. All three are confined within the central 3 pc. Both the Northern and Eastern Arm streams have high eccentricities (e = 0.83 +/- 0.10 and 0.82 +/- 0.05, respectively), while the Western Arc stream is nearly circular, with e = 0.2 +/- 0.15. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth) and have orbital periods in the range 4-8x10(4) yr. To verify the fit, the distributions of radial and transverse velocity vectors in Sgr A West were also computed using the Keplerian model and they show good agreement with both the proper motion and radial velocity data. In addition, the computed orbits suggest that the Northern and Eastern Arm streams may collide in the "Bar" region (a few arcsec south of Sgr A*) and that most of the orbiting ionized gas in the "Bar" region is located behind Sgr A*. We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near infrared observations. From the H92a line data, we find evidence of substantial interaction between the IRS 8 nebula and the Northern Arm stream occurring in the bow-shock region. Other new morphological features revealed in our high-resolution image include (1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field, and (2) a linear feature in the IRS 16 region, suggesting that the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
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dynamics of ionized gas at the galactic center vla observations of the 3d velocity field and location of the ionized streams in sagittarius a west
arXiv: Astrophysics of Galaxies, 2009Co-Authors: Junhui Zhao, M Morris, W M GossAbstract:We present new results based on high-resolution observations of Sgr A West at the Galactic center with the VLA at 1.3 cm. We measured proper motions for 71 compact HII components. We also investigated radial velocities in the LSR velocity using the H92a line data. Combining proper motion and radial velocity measurements, we have determined the 3D velocity distribution in Sgr A West. We find that the three ionized streams (Northern Arm, Eastern Arm, and Western Arc) can be modeled with three bundles of Keplerian orbits around Sgr A*. We determined the five orbital parameters for each of them using LSQ fitting to the locii of the streams. Our results confirm earlier results on the streams in the Western Arc and the Northern Arm to be in Keplerian orbits, suggesting that the stream in the Eastern Arm is also consistent with an elliptical orbit. Both the Northern and Eastern Arm streams have high eccentricities, while the Western Arc stream is nearly circular. All three streams orbit around Sgr A* in a Counterclockwise Sense (viewed from the Earth). We also report an ionized nebula associated with IRS 8, including a bow shock in radio continuum emission which shows excellent agreement with near IR observations. From the H92a line data, we find evidence for interaction between the IRS 8 nebula and the Northern Arm stream. Other new morphological features revealed in our high-resolution image include: 1) a helical structure in the Northern Arm, suggesting that MHD plays an important role in the motion of the ionized gas, in addition to the dynamics determined by the central gravitational field and 2) a linear feature in the IRS 16 region, suggesting the compressed edge of the Northern Arm may result from the collective winds and radiation pressure from the high mass stars in the IRS16 cluster.
Charles J. Brokaw - One of the best experts on this subject based on the ideXlab platform.
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Symmetry Breaking in a Model for Nodal Cilia INTRODUCTION: THE BIOLOGY OF NODAL CILIA
2020Co-Authors: Charles J. BrokawAbstract:Abstract. Nodal cilia are very short cilia found in the embryonic node on the ventral surface of early mammalian embryos. They create a right to left fluid flow that is responsible for determining the normal asymmetry of the internal organs of the mammalian body. To do this, the distal end of the cilium must circle in a Counterclockwise Sense. Computer simulations with 3-dimensional models of flagella allow examination of 3-dimensional movements such as those of nodal cilia. 3-dimensional circling motions of short cilia can be achieved with velocity controlled models, in which dynein activity is regulated by sliding velocity. If dyneins on one outer doublet are controlled by the sliding velocity experienced by that doublet, the system is symmetric, and the 3-dimensional models can show either clockwise or Counterclockwise circling. My computer simulations have examined two possible symmetry breaking mechanisms: 1) dyneins on doublet N are regulated by a mixture of the sliding velocities experienced by doublets N and N+1 (numbered in a clockwise direction, looking from the base). or 2) symmetry is broken by an off-axis force that produces a right-handed twist of the axoneme, consistent with observations that some dyneins can rotate their substrate microtubules in a clockwise direction
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Symmetry Breaking in a Model for Nodal Cilia
2015Co-Authors: Charles J. BrokawAbstract:Abstract. Nodal cilia are very short cilia found in the embryonic node on the ventral surface of early mammalian embryos. They create a right to left fluid flow that is responsible for determining the normal asymmetry of the internal organs of the mammalian body. To do this, the distal end of the cilium must circle in a Counterclockwise Sense. Computer simulations with 3-dimensional models of flagella allow examination of 3-dimensional movements such as those of nodal cilia. 3-dimensional circling motions of short cilia can be achieved with velocity controlled models, in which dynein activity is regulated by sliding velocity. If dyneins on one outer doublet are controlled by the sliding velocity experienced by that doublet, the system is symmetric, and the 3-dimensional models can show either clockwise or Counterclockwise circling. My computer simulations have examined two possible symmetry breaking mechanisms: 1) dyneins on doublet N are regulated by a mixture of the sliding velocities experienced by doublets N and N+1 (numbered in a clockwise direction, looking from the base). or 2) symmetry is broken by an off-axis force that produces a right-handed twist of the axoneme, consistent with observations that some dyneins can rotate their substrate microtubules in a clockwise direction. INTRODUCTION: THE BIOLOGY OF NODAL CILI
