1309.1154
Calibration of RAVE distances to a large sample of Hipparcos stars
Francis
Calibrate distances to 52k RAVE [?] stars, including dwarfs, giants, and pre-MS stars, from a magnituded-limited population of 18k Hipparcos reference sample. Give treatments for a number of types of bias affecting calculation, including bias from the NL relationship between the quantity of interest (e.g., distance or distance modulus) and the measured quantity (parallax or visual magnitude), the Lutz-Kelker bias [a systematic bias that results from using the assumption that the number of observable stars increases with the square of the distance. It causes measured parallaxes to stars be larger than their actual values (why?) This causes inferred luminosities and distances to be too small] due to variation in density of the stellar population. The use of a magnitude bound minimizes the Malmquist and the Lutz-Kelker bias, and avoids a measurement bias resulting from the greater accuracy of Hipparcos parallaxes for brighter stars. The calibration is applicable to stars in 2MASS when there is some way to determine stellar class with reasonable confidence. For RAVE this is possible for hot dwarfs [what is that?] and using log g [what is that?]. The accuracy of the calibration is tested against Hipparcos stars with better then 2% parallax errors, and by comparison of the RAVE velocity distribution with that of Hipparcos, and is found to improve upon previous estimates of luminosity distance. An estimate of the LSR [what is this?] from RAVE data, U, V, W = 14.9, 15.3, 6.9 km/s shows agreement with the current best estimate from XHIP [?]. The RAVE velocity distribution confirms the alignment of stellar motions with spiral structure [how did it turn from distance calibration to velocity distribution? I guess that's what the RAVE survey must be about].
1309.1159
The rotationally stabilized VPOS and predicted proper motions of the Milky Way satellite galaxies
Pawlowski, Kroupa
The satellite galaxies of the MW define a vast polar structure (VPOS), a thin plane perpendicular to the MW disc. Proper motion (PM) measurements are now available for all of the 11 brightest, 'classical' satellites and allow an updated analysis of the alignment of their orbital poles with this spatial structure. The coherent orbital alignment of 7 to 9 out of 11 satellites demonstrates that the VPOSS is a rotationally stabilized structure and not only a pressure-supported, flattened ellipsoid. This allows us to empirically and model independently predict the PMs of almost all satellites galaxies by assuming that the MW satellite galaxies orbit within the VPOS. As a test of our method, the predictions are best met by satellites whose PMs are already well constrained, as expected because more uncertain measurements tend to deviate more from the true values. Improved and new PM measurements will further test these predictions. A strong alignment of the satellite galaxy orbital poles is not expected in DM based simulations of galaxy formation. Coherent orbital directions of satellite galaxies are, however, a natural consequence of tidal dwarf galaxies formed together in the debris of a galaxy collision. The orbital poles of the MW satellite galaxies therefore lend further support to tidal scenarios for the for the origin of the VPOS and are a very significant challenge for the standard LCDM model of cosmology. Also note that the dependence of the MW satellite speeds on Galactocentric distance appear to map an effective potential with a constant velocity of approximately 240 km/s to about 250 kpc. The individual satellite velocities are only mildly radial.
1309.1161
Noiseless gravitational lensing simulations
Angulo, Chen, Hilbert, Abel
There is a lack of accurate theoretical predictions for the lensing signal of substructures, mainly because of the discreteness noise inherent to N-body sims. Present Recursive-TCM, a method that is able to provide lensing predictions with an arbitrarily low discreteness noise, without any free parameters or smoothing scale. This solution is based on a novel way of interpreting the results of N-body simulations, where particles simply trace the evolution and distortion of Lagrangian phase-space volume elements. Discuss the advantages of this method over the widely used cloud-in-cells and adaptive-kernel smoothing density estimators. Applying the new method to a cluster-sized DM halo simulated in warm and cold DM scenarios, show how the expected differences in their substructure population translate into differences in the convergence and magnification maps. Anticipate that this method will provide the high-precision theoretical predictions required to interpret and fully exploit SL observations [It may be discrete-noise-less, but are there any other sources of "noise"?].
1309.1162
Broadband Alcock-Paczynski test exploiting redshift distortions
Song, Okumura, Taruya
BAO, known as one of the largest cosmological objects, is a cosmological tool to measure geometric distances via the Alcock-Paczynski effect, by which the observed BAO exhibits characteristic anisotropies in addition to the redshift distortions. This implies that once we know the correct distances to the observed BAO, the tip points of baryon acoustic peaks in the anisotropic correlation function of galaxies, xi(sigma,pi), can form a great circle (hereafter 2d BAO circle) in the sigma and pi plane, where sigma and pi are the separation of galaxy pair parallel and perpendicular to the LoS, respectively. This 2d BAO circle is indeed robust and remains unchanged under the variations of the unknown galaxy bias and/or coherent motion, while it varies transversely and radially with respect to the variations of D_A and H^-1, respectively. Hereby the ratio between transverse distance D_A and the radial distance H^-1 uniquely reproduces the intrinsic shape of the 2d BAO circle, which is a priori given by the known broadband shape of spectra: "broadband Alcock-Paczynski test" exploiting z distortions. All BAO peaks of xi(sigma,pi) are precisely calculated with the improved theoretical model of z distortion. Test the broadband Alcock-Paczynski method using BOSS-like mock catalogues. The transverse and radial distances are probed in precision of several percentage fractional errors, and the coherent motion is observed to match with the fiducial values accurately.
Calibration of RAVE distances to a large sample of Hipparcos stars
Francis
Calibrate distances to 52k RAVE [?] stars, including dwarfs, giants, and pre-MS stars, from a magnituded-limited population of 18k Hipparcos reference sample. Give treatments for a number of types of bias affecting calculation, including bias from the NL relationship between the quantity of interest (e.g., distance or distance modulus) and the measured quantity (parallax or visual magnitude), the Lutz-Kelker bias [a systematic bias that results from using the assumption that the number of observable stars increases with the square of the distance. It causes measured parallaxes to stars be larger than their actual values (why?) This causes inferred luminosities and distances to be too small] due to variation in density of the stellar population. The use of a magnitude bound minimizes the Malmquist and the Lutz-Kelker bias, and avoids a measurement bias resulting from the greater accuracy of Hipparcos parallaxes for brighter stars. The calibration is applicable to stars in 2MASS when there is some way to determine stellar class with reasonable confidence. For RAVE this is possible for hot dwarfs [what is that?] and using log g [what is that?]. The accuracy of the calibration is tested against Hipparcos stars with better then 2% parallax errors, and by comparison of the RAVE velocity distribution with that of Hipparcos, and is found to improve upon previous estimates of luminosity distance. An estimate of the LSR [what is this?] from RAVE data, U, V, W = 14.9, 15.3, 6.9 km/s shows agreement with the current best estimate from XHIP [?]. The RAVE velocity distribution confirms the alignment of stellar motions with spiral structure [how did it turn from distance calibration to velocity distribution? I guess that's what the RAVE survey must be about].
1309.1159
The rotationally stabilized VPOS and predicted proper motions of the Milky Way satellite galaxies
Pawlowski, Kroupa
The satellite galaxies of the MW define a vast polar structure (VPOS), a thin plane perpendicular to the MW disc. Proper motion (PM) measurements are now available for all of the 11 brightest, 'classical' satellites and allow an updated analysis of the alignment of their orbital poles with this spatial structure. The coherent orbital alignment of 7 to 9 out of 11 satellites demonstrates that the VPOSS is a rotationally stabilized structure and not only a pressure-supported, flattened ellipsoid. This allows us to empirically and model independently predict the PMs of almost all satellites galaxies by assuming that the MW satellite galaxies orbit within the VPOS. As a test of our method, the predictions are best met by satellites whose PMs are already well constrained, as expected because more uncertain measurements tend to deviate more from the true values. Improved and new PM measurements will further test these predictions. A strong alignment of the satellite galaxy orbital poles is not expected in DM based simulations of galaxy formation. Coherent orbital directions of satellite galaxies are, however, a natural consequence of tidal dwarf galaxies formed together in the debris of a galaxy collision. The orbital poles of the MW satellite galaxies therefore lend further support to tidal scenarios for the for the origin of the VPOS and are a very significant challenge for the standard LCDM model of cosmology. Also note that the dependence of the MW satellite speeds on Galactocentric distance appear to map an effective potential with a constant velocity of approximately 240 km/s to about 250 kpc. The individual satellite velocities are only mildly radial.
1309.1161
Noiseless gravitational lensing simulations
Angulo, Chen, Hilbert, Abel
There is a lack of accurate theoretical predictions for the lensing signal of substructures, mainly because of the discreteness noise inherent to N-body sims. Present Recursive-TCM, a method that is able to provide lensing predictions with an arbitrarily low discreteness noise, without any free parameters or smoothing scale. This solution is based on a novel way of interpreting the results of N-body simulations, where particles simply trace the evolution and distortion of Lagrangian phase-space volume elements. Discuss the advantages of this method over the widely used cloud-in-cells and adaptive-kernel smoothing density estimators. Applying the new method to a cluster-sized DM halo simulated in warm and cold DM scenarios, show how the expected differences in their substructure population translate into differences in the convergence and magnification maps. Anticipate that this method will provide the high-precision theoretical predictions required to interpret and fully exploit SL observations [It may be discrete-noise-less, but are there any other sources of "noise"?].
1309.1162
Broadband Alcock-Paczynski test exploiting redshift distortions
Song, Okumura, Taruya
BAO, known as one of the largest cosmological objects, is a cosmological tool to measure geometric distances via the Alcock-Paczynski effect, by which the observed BAO exhibits characteristic anisotropies in addition to the redshift distortions. This implies that once we know the correct distances to the observed BAO, the tip points of baryon acoustic peaks in the anisotropic correlation function of galaxies, xi(sigma,pi), can form a great circle (hereafter 2d BAO circle) in the sigma and pi plane, where sigma and pi are the separation of galaxy pair parallel and perpendicular to the LoS, respectively. This 2d BAO circle is indeed robust and remains unchanged under the variations of the unknown galaxy bias and/or coherent motion, while it varies transversely and radially with respect to the variations of D_A and H^-1, respectively. Hereby the ratio between transverse distance D_A and the radial distance H^-1 uniquely reproduces the intrinsic shape of the 2d BAO circle, which is a priori given by the known broadband shape of spectra: "broadband Alcock-Paczynski test" exploiting z distortions. All BAO peaks of xi(sigma,pi) are precisely calculated with the improved theoretical model of z distortion. Test the broadband Alcock-Paczynski method using BOSS-like mock catalogues. The transverse and radial distances are probed in precision of several percentage fractional errors, and the coherent motion is observed to match with the fiducial values accurately.
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