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Aaron J Romanowsky - One of the best experts on this subject based on the ideXlab platform.
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galaxies in λcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
The Astrophysical Journal, 2011Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, 1 fits—at least on average—all basic statistics of galaxies with circular velocities Vcirc > 80 km s − calculated at a radius of ∼10 kpc. Our primary observational constraint is the luminosity–Velocity (LV) relation—which generalizes the Tully–Fisher and Faber–Jackson relations in allowing all types of galaxies to be included, and provides a fundamental benchmark to be reproduced by any theory of galaxy formation. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic LV relation from ∼50 km s −1 to ∼500 km s −1 , with a bend below ∼80 km s −1 and a systematic offset between lateand early-type galaxies. For comparison to theory, we employ our new ΛCDM “Bolshoi” simulation of DM, which has unprecedented mass and force resolution over a large cosmological volume, while using an up-to-date set of cosmological parameters. We use HAM to assign rank-ordered galaxy luminosities to the DM halos, a procedure that automatically fits the empirical luminosity Function and provides a predicted LV relation that can be checked against observations. The adiabatic contraction of DM halos in response to the infall of the baryons is included as an optional model ingredient. The resulting predictions for the LV relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr =− 14 to Mr =− 22. We also compare our predictions for the “cold” baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function (VF) is also in agreement with the galaxy VF from 80 to 400 km s −1 ,u sing the HIPASS survey for late-type galaxies and Sloan Digital Sky Survey (SDSS) for early-type galaxies. However, in accord with other recent results, we find that the DM halos with Vcirc < 80 km s −1 are much more abundant than observed galaxies with the same Vcirc. Finally, we find that the two-point correlation Function of bright galaxies in our model matches very well the results from the final data release of the SDSS, especially when a small amount of scatter is included in the HAM prescription.
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galaxies in lcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter. We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits all basic statistics of galaxies with circular velocities Vcirc > 80 km/s. Our observational constraint is the luminosity-Velocity relation which allows all types of galaxies to be included. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic luminosity-Velocity relation from 50 km/s to 500 km/s, with a bend below 80 km/s and a systematic offset between late- and early-type galaxies. For comparison to theory, we employ our LCDM "Bolshoi" simulation of dark matter, which has unprecedented mass and force resolution. We use halo abundance matching to assign rank-ordered galaxy luminosities to the dark matter halos. The resulting predictions for the luminosity-Velocity relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr = -14-22. We also compare our predictions for the "cold" baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function is in agreement with the galaxy Velocity Function for 80-400 km/s. However, we find that the dark matter halos with Vcirc < 80 km/s are much more abundant than observed galaxies with the same Vcirc . We find that the two-point correlation Function of galaxies in our model matches very well the results from the SDSS.
Marla Geha - One of the best experts on this subject based on the ideXlab platform.
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the kinematics of the ultra faint milky way satellites solving the missing satellite problem
The Astrophysical Journal, 2007Co-Authors: Joshua D Simo, Marla GehaAbstract:We present Keck DEIMOS spectroscopy of stars in eight of the newly discovered ultra-faint dwarf galaxies around the Milky Way. We measure the Velocity dispersions of Canes Venatici I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, Leo T, Ursa Major I, and Ursa Major II from the velocities of 18-214 stars in each galaxy and find dispersions ranging from 3.3 to 7.6 km s^(-1). The six galaxies with absolute magnitudes M_V < -4 are highly dark matter dominated, with mass-to-light ratios approaching 1000 M_☉/L_(☉,V). For the fainter galaxies we find tentative evidence for tidal disruption. The measured Velocity dispersions of the ultra-faint dwarfs are correlated with their luminosities, indicating that a minimum mass for luminous galactic systems may not yet have been reached. We also measure the metallicities of the observed stars and find that the new dwarfs have mean metallicities of [Fe/H] = -2.0 to -2.3; these galaxies represent some of the most metal-poor stellar systems known. The six brightest of the ultra-faint dwarfs extend the luminosity-metallicity relationship followed by more luminous dwarfs by a factor of ~30 in luminosity. We detect metallicity spreads of up to 0.5 dex in several objects, suggesting multiple star formation epochs. UMa II and Com, despite their exceptionally low luminosities, have higher metallicities that suggest they may once have been much more massive. Having established the masses of the ultra-faint dwarfs, we re-examine the missing satellite problem. After correcting for the sky coverage of the Sloan Digital Sky Survey, we find that the ultra-faint dwarfs substantially alleviate the discrepancy between the predicted and observed numbers of satellites around the Milky Way, but there are still a factor of ~4 too few dwarf galaxies over a significant range of masses. We show that if galaxy formation in low-mass dark matter halos is strongly suppressed after reionization, the simulated circular Velocity Function of CDM subhalos can be brought into approximate agreement with the observed circular Velocity Function of Milky Way satellite galaxies.
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the kinematics of the ultra faint milky way satellites solving the missing satellite problem
arXiv: Astrophysics, 2007Co-Authors: Joshua D Simon, Marla GehaAbstract:We present Keck/DEIMOS spectroscopy of stars in 8 of the newly discovered ultra-faint dwarf galaxies around the Milky Way. We measure the Velocity dispersions of Canes Venatici I and II, Ursa Major I and II, Coma Berenices, Hercules, Leo IV and Leo T from the velocities of 18 - 214 stars in each galaxy and find dispersions ranging from 3.3 to 7.6 km/s. The 6 galaxies with absolute magnitudes M_V < -4 are highly dark matter-dominated, with mass-to-light ratios approaching 1000. The measured Velocity dispersions are inversely correlated with their luminosities, indicating that a minimum mass for luminous galactic systems may not yet have been reached. We also measure the metallicities of the observed stars and find that the 6 brightest of the ultra-faint dwarfs extend the luminosity-metallicity relationship followed by brighter dwarfs by 2 orders of magnitude in luminosity; several of these objects have mean metallicities as low as [Fe/H] = -2.3 and therefore represent some of the most metal-poor known stellar systems. We detect metallicity spreads of up to 0.5 dex in several objects, suggesting multiple star formation epochs. Having established the masses of the ultra-faint dwarfs, we re-examine the missing satellite problem. After correcting for the sky coverage of the SDSS, we find that the ultra-faint dwarfs substantially alleviate the discrepancy between the predicted and observed numbers of satellites around the Milky Way, but there are still a factor of ~4 too few dwarf galaxies over a significant range of masses. We show that if galaxy formation in low-mass dark matter halos is strongly suppressed after reionization, the simulated circular Velocity Function of CDM subhalos can be brought into approximate agreement with the observed circular Velocity Function of Milky Way satellite galaxies. [slightly abridged]
Sebastian Trujillogomez - One of the best experts on this subject based on the ideXlab platform.
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galaxies in λcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
The Astrophysical Journal, 2011Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, 1 fits—at least on average—all basic statistics of galaxies with circular velocities Vcirc > 80 km s − calculated at a radius of ∼10 kpc. Our primary observational constraint is the luminosity–Velocity (LV) relation—which generalizes the Tully–Fisher and Faber–Jackson relations in allowing all types of galaxies to be included, and provides a fundamental benchmark to be reproduced by any theory of galaxy formation. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic LV relation from ∼50 km s −1 to ∼500 km s −1 , with a bend below ∼80 km s −1 and a systematic offset between lateand early-type galaxies. For comparison to theory, we employ our new ΛCDM “Bolshoi” simulation of DM, which has unprecedented mass and force resolution over a large cosmological volume, while using an up-to-date set of cosmological parameters. We use HAM to assign rank-ordered galaxy luminosities to the DM halos, a procedure that automatically fits the empirical luminosity Function and provides a predicted LV relation that can be checked against observations. The adiabatic contraction of DM halos in response to the infall of the baryons is included as an optional model ingredient. The resulting predictions for the LV relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr =− 14 to Mr =− 22. We also compare our predictions for the “cold” baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function (VF) is also in agreement with the galaxy VF from 80 to 400 km s −1 ,u sing the HIPASS survey for late-type galaxies and Sloan Digital Sky Survey (SDSS) for early-type galaxies. However, in accord with other recent results, we find that the DM halos with Vcirc < 80 km s −1 are much more abundant than observed galaxies with the same Vcirc. Finally, we find that the two-point correlation Function of bright galaxies in our model matches very well the results from the final data release of the SDSS, especially when a small amount of scatter is included in the HAM prescription.
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galaxies in lcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter. We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits all basic statistics of galaxies with circular velocities Vcirc > 80 km/s. Our observational constraint is the luminosity-Velocity relation which allows all types of galaxies to be included. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic luminosity-Velocity relation from 50 km/s to 500 km/s, with a bend below 80 km/s and a systematic offset between late- and early-type galaxies. For comparison to theory, we employ our LCDM "Bolshoi" simulation of dark matter, which has unprecedented mass and force resolution. We use halo abundance matching to assign rank-ordered galaxy luminosities to the dark matter halos. The resulting predictions for the luminosity-Velocity relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr = -14-22. We also compare our predictions for the "cold" baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function is in agreement with the galaxy Velocity Function for 80-400 km/s. However, we find that the dark matter halos with Vcirc < 80 km/s are much more abundant than observed galaxies with the same Vcirc . We find that the two-point correlation Function of galaxies in our model matches very well the results from the SDSS.
Shiqiang Dai - One of the best experts on this subject based on the ideXlab platform.
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effect of the optimal Velocity Function on traffic phase transitions in lattice hydrodynamic models
Communications in Nonlinear Science and Numerical Simulation, 2009Co-Authors: Xianglin Han, Shiqiang DaiAbstract:Abstract The original lattice hydrodynamics models of traffic flow are extended to take into account the complex acceleration behavior of drivers. A new optimal Velocity Function which considers the stepwise acceleration effect and fits the observed data better is introduced. The stability conditions of these two models are obtained by using the linear stability theory. It is shown that the modified optimal Velocity Function has a remarkable influence on the neutral stability curve and the traffic phase transitions. In a certain vehicle’s density and driver’s sensitivity region, tri-stable states will occur. In addition, the properties of the multiple phases also depend on the asymmetry of the optimal Velocity Function and the stage number of multi-phase transitions is closely related to the turning points of the optimal Velocity Function. The validity and correctness of the analytical results is confirmed by numerical simulations.
Joel R Primack - One of the best experts on this subject based on the ideXlab platform.
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galaxies in λcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
The Astrophysical Journal, 2011Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult if not impossible for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter (DM). We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, 1 fits—at least on average—all basic statistics of galaxies with circular velocities Vcirc > 80 km s − calculated at a radius of ∼10 kpc. Our primary observational constraint is the luminosity–Velocity (LV) relation—which generalizes the Tully–Fisher and Faber–Jackson relations in allowing all types of galaxies to be included, and provides a fundamental benchmark to be reproduced by any theory of galaxy formation. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic LV relation from ∼50 km s −1 to ∼500 km s −1 , with a bend below ∼80 km s −1 and a systematic offset between lateand early-type galaxies. For comparison to theory, we employ our new ΛCDM “Bolshoi” simulation of DM, which has unprecedented mass and force resolution over a large cosmological volume, while using an up-to-date set of cosmological parameters. We use HAM to assign rank-ordered galaxy luminosities to the DM halos, a procedure that automatically fits the empirical luminosity Function and provides a predicted LV relation that can be checked against observations. The adiabatic contraction of DM halos in response to the infall of the baryons is included as an optional model ingredient. The resulting predictions for the LV relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr =− 14 to Mr =− 22. We also compare our predictions for the “cold” baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function (VF) is also in agreement with the galaxy VF from 80 to 400 km s −1 ,u sing the HIPASS survey for late-type galaxies and Sloan Digital Sky Survey (SDSS) for early-type galaxies. However, in accord with other recent results, we find that the DM halos with Vcirc < 80 km s −1 are much more abundant than observed galaxies with the same Vcirc. Finally, we find that the two-point correlation Function of bright galaxies in our model matches very well the results from the final data release of the SDSS, especially when a small amount of scatter is included in the HAM prescription.
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galaxies in lcdm with halo abundance matching luminosity Velocity relation baryonic mass Velocity relation Velocity Function and clustering
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Sebastian Trujillogomez, Anatoly Klypin, Joel R Primack, Aaron J RomanowskyAbstract:It has long been regarded as difficult for a cosmological model to account simultaneously for the galaxy luminosity, mass, and Velocity distributions. We revisit this issue using a modern compilation of observational data along with the best available large-scale cosmological simulation of dark matter. We find that the standard cosmological model, used in conjunction with halo abundance matching (HAM) and simple dynamical corrections, fits all basic statistics of galaxies with circular velocities Vcirc > 80 km/s. Our observational constraint is the luminosity-Velocity relation which allows all types of galaxies to be included. We have compiled data for a variety of galaxies ranging from dwarf irregulars to giant ellipticals. The data present a clear monotonic luminosity-Velocity relation from 50 km/s to 500 km/s, with a bend below 80 km/s and a systematic offset between late- and early-type galaxies. For comparison to theory, we employ our LCDM "Bolshoi" simulation of dark matter, which has unprecedented mass and force resolution. We use halo abundance matching to assign rank-ordered galaxy luminosities to the dark matter halos. The resulting predictions for the luminosity-Velocity relation are in excellent agreement with the available data on both early-type and late-type galaxies for the luminosity range from Mr = -14-22. We also compare our predictions for the "cold" baryon mass (i.e., stars and cold gas) of galaxies as a Function of circular Velocity with the available observations, again finding a very good agreement. The predicted circular Velocity Function is in agreement with the galaxy Velocity Function for 80-400 km/s. However, we find that the dark matter halos with Vcirc < 80 km/s are much more abundant than observed galaxies with the same Vcirc . We find that the two-point correlation Function of galaxies in our model matches very well the results from the SDSS.
