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E K Grebel - One of the best experts on this subject based on the ideXlab platform.
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on the origin of the radial mass Density Profile of the galactic halo globular cluster system
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: Genevieve Parmentier, E K GrebelAbstract:We investigate what may be the origin of the presently observed spatial distribution of the mass of the Galactic Old Halo globular cluster system. We propose its radial mass Density Profile to be a relic of the distribution of the cold baryonic material in the protogalaxy. Assuming that this one arises from the Profile of the whole protogalaxy minus the contribution of the dark matter (and a small contribution of the hot gas by which the protoglobular clouds were bound), we show that the mass distributions around the Galactic centre of this cold gas and of the Old Halo agree satisfactorily. In order to demonstrate our hypothesis even more conclusively, we simulate the evolution with time, up to an age of 15 Gyr, of a putative globular cluster system whose initial mass distribution in the Galactic halo follows the Profile of the cold protogalactic gas. We show that beyond a galactocentric distance of order 2-3 kpc, the initial shape of such a mass Density Profile is preserved despite the complete destruction of some globular clusters and the partial evaporation of some others. This result is almost independent of the choice of the initial mass function for the globular clusters, which is still ill determined. The shape of these evolved cluster system mass Density Profiles also agrees with the presently observed Profile of the Old Halo globular cluster system, thus strengthening our hypothesis. Our result might suggest that the flattening shown by the Old Halo mass Density Profile at short distances from the Galactic centre is, at least partly, of primordial origin.
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on the origin of the radial mass Density Profile of the galactic halo globular cluster system
arXiv: Astrophysics, 2005Co-Authors: Genevieve Parmentier, E K GrebelAbstract:We investigate what may be the origin of the presently observed spatial distribution of the mass of the Galactic Old Halo globular cluster system. We propose its radial mass Density Profile to be a relic of the distribution of the cold baryonic material in the protoGalaxy. Assuming that this one arises from the Profile of the whole protoGalaxy minus the contribution of the dark matter (and a small contribution of the hot gas by which the protoglobular clouds were bound), we show that the mass distributions around the Galactic centre of this cold gas and of the Old Halo agree satisfactorily. In order to demonstrate our hypothesis even more conclusively, we simulate the evolution with time, up to an age of 15 Gyr, of a putative globular cluster system whose initial mass distribution in the Galactic halo follows the Profile of the cold protogalactic gas. We show that beyond a galactocentric distance of order 2 to 3 kpc, the initial shape of such a mass Density Profile is preserved in spite of the complete destruction of some globular clusters and the partial evaporation of some others. This result is almost independent of the choice of the initial mass function for the globular clusters, which is still ill-determined. The shape of these evolved cluster system mass Density Profiles also agree with the presently observed Profile of the Old Halo globular cluster system, thus strengthening our hypothesis. Our result might suggest that the flattening shown by the Old Halo mass Density Profile at short distance from the Galactic centre is, at least partly, of primordial origin.
Gregory D Martinez - One of the best experts on this subject based on the ideXlab platform.
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three dimensional stellar kinematics at the galactic center measuring the nuclear star cluster spatial Density Profile black hole mass and distance
The Astrophysical Journal, 2013Co-Authors: Sylvana Yelda, Andrea M. Ghez, James S Bullock, Manoj Kaplinghat, Annika H G Peter, Gregory D Martinez, K PhiferAbstract:We present three-dimensional (3D) kinematic observations of stars within the central 0.5 pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface Density Profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D Profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial Density Profile, cluster velocity anisotropy, black hole mass (M BH), and distance to the Galactic center (R 0) simultaneously. We find that the inner stellar Density Profile of the late-type stars, ρ(r)r –γ, have a power law slope , much more shallow than the frequently assumed Bahcall-Wolf slope of γ = 7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M ☉ and kpc is consistent with that derived from stellar orbits within 1'' of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R 0 is reduced by 30% . We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R 0.
Annika H G Peter - One of the best experts on this subject based on the ideXlab platform.
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three dimensional stellar kinematics at the galactic center measuring the nuclear star cluster spatial Density Profile black hole mass and distance
The Astrophysical Journal, 2013Co-Authors: Sylvana Yelda, Andrea M. Ghez, James S Bullock, Manoj Kaplinghat, Annika H G Peter, Gregory D Martinez, K PhiferAbstract:We present three-dimensional (3D) kinematic observations of stars within the central 0.5 pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface Density Profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D Profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial Density Profile, cluster velocity anisotropy, black hole mass (M BH), and distance to the Galactic center (R 0) simultaneously. We find that the inner stellar Density Profile of the late-type stars, ρ(r)r –γ, have a power law slope , much more shallow than the frequently assumed Bahcall-Wolf slope of γ = 7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M ☉ and kpc is consistent with that derived from stellar orbits within 1'' of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R 0 is reduced by 30% . We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R 0.
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Measuring the stellar luminosity function and spatial Density Profile of the inner 0.5 pc of the Milky Way nuclear star cluster
Journal of Physics: Conference Series, 2012Co-Authors: Tuan Do, Sylvana Yelda, Shelley A. Wright, Andrea M. Ghez, Jessica R Lu, James S Bullock, Annika H G Peter, Mark Morris, G. Martinez, Manoj KaplinghatAbstract:We report on measurements of the luminosity function of early (young) and late-type (old) stars in the central 0.5 pc of the Milky Way nuclear star cluster as well as the Density Profiles of both components. The young (~ 6 Myr) and old stars (> 1 Gyr) in this region provide different physical probes of the environment around a supermassive black hole; the luminosity function of the young stars offers us a way to measure the initial mass function from star formation in an extreme environment, while the Density Profile of the old stars offers us a probe of the dynamical interaction of a star cluster with a massive black hole. The two stellar populations are separated through a near-infrared spectroscopic survey using the integral-field spectrograph OSIRIS on Keck II behind the laser guide star adaptive optics system. This spectroscopic survey is able to separate early-type (young) and late-type (old) stars with a completeness of 50% at K' = 15.5. We describe our method of completeness correction using a combination of star planting simulations and Bayesian inference. The completeness corrected luminosity function of the early-type stars contains significantly more young stars at faint magnitudes compared to previous surveys with similar depth. In addition, by using proper motion and radial velocity measurements along with anisotropic spherical Jeans modeling of the cluster, it is possible to measure the spatial Density Profile of the old stars, which has been difficult to constrain with number counts alone. The most probable model shows that the spatial Density Profile, n(r) ∝ r−γ, to be shallow with γ = 0.4 ± 0.2, which is much flatter than the dynamically relaxed case of γ = 3/2 to 7/4, but does rule out a 'hole' in the distribution of old stars. We show, for the first time, that the spatial Density Profile, the black hole mass, and velocity anisotropy can be fit simultaneously to obtain a black hole mass that is consistent with that derived from individual orbits of stars at distances < 1000 AU from the Galactic center.
Genevieve Parmentier - One of the best experts on this subject based on the ideXlab platform.
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on the origin of the radial mass Density Profile of the galactic halo globular cluster system
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: Genevieve Parmentier, E K GrebelAbstract:We investigate what may be the origin of the presently observed spatial distribution of the mass of the Galactic Old Halo globular cluster system. We propose its radial mass Density Profile to be a relic of the distribution of the cold baryonic material in the protogalaxy. Assuming that this one arises from the Profile of the whole protogalaxy minus the contribution of the dark matter (and a small contribution of the hot gas by which the protoglobular clouds were bound), we show that the mass distributions around the Galactic centre of this cold gas and of the Old Halo agree satisfactorily. In order to demonstrate our hypothesis even more conclusively, we simulate the evolution with time, up to an age of 15 Gyr, of a putative globular cluster system whose initial mass distribution in the Galactic halo follows the Profile of the cold protogalactic gas. We show that beyond a galactocentric distance of order 2-3 kpc, the initial shape of such a mass Density Profile is preserved despite the complete destruction of some globular clusters and the partial evaporation of some others. This result is almost independent of the choice of the initial mass function for the globular clusters, which is still ill determined. The shape of these evolved cluster system mass Density Profiles also agrees with the presently observed Profile of the Old Halo globular cluster system, thus strengthening our hypothesis. Our result might suggest that the flattening shown by the Old Halo mass Density Profile at short distances from the Galactic centre is, at least partly, of primordial origin.
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on the origin of the radial mass Density Profile of the galactic halo globular cluster system
arXiv: Astrophysics, 2005Co-Authors: Genevieve Parmentier, E K GrebelAbstract:We investigate what may be the origin of the presently observed spatial distribution of the mass of the Galactic Old Halo globular cluster system. We propose its radial mass Density Profile to be a relic of the distribution of the cold baryonic material in the protoGalaxy. Assuming that this one arises from the Profile of the whole protoGalaxy minus the contribution of the dark matter (and a small contribution of the hot gas by which the protoglobular clouds were bound), we show that the mass distributions around the Galactic centre of this cold gas and of the Old Halo agree satisfactorily. In order to demonstrate our hypothesis even more conclusively, we simulate the evolution with time, up to an age of 15 Gyr, of a putative globular cluster system whose initial mass distribution in the Galactic halo follows the Profile of the cold protogalactic gas. We show that beyond a galactocentric distance of order 2 to 3 kpc, the initial shape of such a mass Density Profile is preserved in spite of the complete destruction of some globular clusters and the partial evaporation of some others. This result is almost independent of the choice of the initial mass function for the globular clusters, which is still ill-determined. The shape of these evolved cluster system mass Density Profiles also agree with the presently observed Profile of the Old Halo globular cluster system, thus strengthening our hypothesis. Our result might suggest that the flattening shown by the Old Halo mass Density Profile at short distance from the Galactic centre is, at least partly, of primordial origin.
K Phifer - One of the best experts on this subject based on the ideXlab platform.
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three dimensional stellar kinematics at the galactic center measuring the nuclear star cluster spatial Density Profile black hole mass and distance
The Astrophysical Journal, 2013Co-Authors: Sylvana Yelda, Andrea M. Ghez, James S Bullock, Manoj Kaplinghat, Annika H G Peter, Gregory D Martinez, K PhiferAbstract:We present three-dimensional (3D) kinematic observations of stars within the central 0.5 pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface Density Profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D Profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial Density Profile, cluster velocity anisotropy, black hole mass (M BH), and distance to the Galactic center (R 0) simultaneously. We find that the inner stellar Density Profile of the late-type stars, ρ(r)r –γ, have a power law slope , much more shallow than the frequently assumed Bahcall-Wolf slope of γ = 7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M ☉ and kpc is consistent with that derived from stellar orbits within 1'' of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R 0 is reduced by 30% . We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R 0.