Sunday. Got a lot of work done yesterday (managed to get the gg lensing code running after including some fixes). Aaron flies back from Vancouver tonight. Hope to get the reply to the MNRAS referee report finished today.
1110.4107
Virial-to-optical velocity ratios of local disk galaxies from combined kinematics and galaxy-galaxy lensing
Reyes, Mandelbaum, Gunn, Nakajima, Seljak, Hirata
* whoa, it's one of mine.
* DM and baryonic mass are 'comparable' within the optical radius
Measure virial-to-optical velocity ratios of disk galaxies measured for disk galaxies at <z>=0.07 and with stellar masses 1e9 Msun < M* < 1e11 Msun. The ratio of the circular velocity measured at the virial radius of the dark matter halo (~150 kpc) to that at the optical radius of the disk (~10 kpc) is a strong observational constraint: links galaxies to their DM haloes dynamically and constrains the total mass profile of disk galaxies over an order of magnitude in length scale. For this measurement, combine V_vir derived from halo masses measured with gg lensing, with V_opt derived from the Tully-Fisher relation (TFR) from Reyes et al (2011). Use similarly-selected galaxy samples from both the lensing and TFR analysis. For three M_* bins with lensing-weighted mean stellar masses of 0.6, 2.7 and 6.5e10 Msun, find halo-to-stellar mass ratios M_vir/M_*=41, 23, and 26, with 1-sigma statistical uncertainties of around 0.1 dex, and V_vir/V_opt=0.79, 0.72, and 0.79 (Vopt/Vvir~1.3), with 1-sigma statistical uncertainties of around 0.05 in Vvir/Vopt, respectively. Results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons. The results obtained in this work will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work. This paper presents a new an improved galaxy shape catalogue for weak lensing that covers the full SDSS DR7 footprint.
1110.4370
Gravitationally consistent halo catalogs and merger trees for precision cosmology
Behroozi, Wechsler, Wu, Buscha, Klypin, Primack
New method for generating merger trees and halo catalogs. Keeps track of and supplements "missing" haloes, for self-consistency. Check for self-consistency, looks good.
1110.4372
The Rockstar phase-space temporal halo finder and the velocity offsets of cluster cores
Behroozi, Wechsler, Wu
New algorithm for identifying dark matter halos, substructure, and tidal features: adaptive hierarchical refinement of fof groups in six phase-space dimensions and one time dimension, which allows for robust tracking of substructure. Fast. Good recovery of halo properties. Demonstrate conclusively that DM halo cores are not at rest relative to the halo bulk or satellite average velocities; have coherent velocity offsets across a wide range of halo masses and redshifts. For massive clusters, the offsets can be up to 400 km/s at z=0, and even higher at high redshifts. Code publicly available.
1110.4391
Discovery of a dissociative galaxy cluster merger with large physical separation
Dawson, Wittman, Jee, Gee, Hughes, Tyson, Schmidt, Thorman, Bradac, Miyazaki, Lemaux, Utsumi
Bullet cluster analog at z=0.5: collisional cluster gas has become separated fomr the collisionless galaxies and DM. Identify cluster using optical and weak lensing observations as part of DLS. Cluster is a dissociative merger. System is at least 0.7Gyr since first pass-through.
1110.4431
A grand rotation curve and DM halo in the MW galaxy
Sofue
Rotation curve of MW constructed, covering a wide range of radius (galactic center to 1Mpc); deconvolved into bulge, disk and halo components by least-squares fitting. Dark halo component fits well with NFw density profile. Fit yielded h=16.3 kpc and rho_0=7.37e-3 Msun/pc^3. Local dark matter density near the sun at R_0=8 kpc is estimated to be 6.8e-2 Msun/pc^3. Total mass inside the gravitational boundary of the galaxy at R~385 kpc (half distance to M31) is estimated to be M_h~9e11 Msun. Stellar baryon fraction of 5%. From the expected baryon fraction of local group, suggest baryons in the form of 1e6K gas fills the dark halo. This may contribute to the observed X-ray background.
1110.4635
Optimized detection of shear peaks in WL maps
Marian, Smith, Hilbert, Schneider
Use multiply-scaled filters to detect shear peaks down to S/N of 3, and you'll do better in constraining cosmology.
1110.4659
The imprint of the relative velocity between baryons and dark matter on the 21-cm signal from reionization
Bittner, Loeb
Post-recombination streaming of baryons through dark matter keeps baryons out of low mass (<1e6 Msun) haloes coherently on scales of a few comoving Mpc. Argued that this will have a large impact on the 21-cm signal before and after reionization, because it raises the minimum mass required to form ionizing sources. Using semi-numerical code, show that the impact of the baryon streaming effect on the 21 cm signal during reionization (redshifts z approximately 7-20) depends strongly on the cooling scenario assumed for star formation, and the corresponding virial temperature or mass at which stars form. For the canonical case of atomic hydrogen cooling at 1e4 Kelvin, the minimum mass for star formation is well above the mass of haloes that are affected by baryon streaming, and there are no major changes to existing predictions. For the case of molecular hydrogen cooling, find reionization is delayed by a change in redshift of approximately 2 [from what reference redshift?], and that more relative power is found in large modes at a given ionization fraction. But the delay in reionization is degenerate with astrophysical assumptions, such as the production rate of UV photons by stars.
* perhaps an interesting way to determine whether baryon streaming relative to DM affects the formation of first stars (ionization sources).
1110.4888
The effects of alignment and ellipticity on the clustering of galaxies
van Daalen, Angulo, White
* ignoring shapes will underestimate clustering on small (~2Mpc) scales, but it shouldn't affect BAO, or other large scale effects, probably {MG}
Effects of halo ellipticity and alignment with LSS on the galaxy correlation function. The effect of disrupting the alignment with larger-scale structure is a ~2% decrease in galaxy correlation function around r=1.8Mpc/h; sphericalizing the ellipsoidal distributions of galaxies within haloes decreases the correlation function by up to 20% for r<1Mpc/h. Similar relusts apply to power spectra and redshift-space correlation functions. Models such as those based on HOD, which adopt a spherically averaged profile for the galaxy distributions within haloes, will therefore significantly underestimate the clustering on sub-Mpc scales.
* must be careful of using HOD to do model fitting on galaxy correlation functions! {RN}
1110.4370
Gravitationally consistent halo catalogs and merger trees for precision cosmology
Behroozi, Wechsler, Wu, Buscha, Klypin, Primack
New method for generating merger trees and halo catalogs. Keeps track of and supplements "missing" haloes, for self-consistency. Check for self-consistency, looks good.
1110.4372
The Rockstar phase-space temporal halo finder and the velocity offsets of cluster cores
Behroozi, Wechsler, Wu
New algorithm for identifying dark matter halos, substructure, and tidal features: adaptive hierarchical refinement of fof groups in six phase-space dimensions and one time dimension, which allows for robust tracking of substructure. Fast. Good recovery of halo properties. Demonstrate conclusively that DM halo cores are not at rest relative to the halo bulk or satellite average velocities; have coherent velocity offsets across a wide range of halo masses and redshifts. For massive clusters, the offsets can be up to 400 km/s at z=0, and even higher at high redshifts. Code publicly available.
1110.4391
Discovery of a dissociative galaxy cluster merger with large physical separation
Dawson, Wittman, Jee, Gee, Hughes, Tyson, Schmidt, Thorman, Bradac, Miyazaki, Lemaux, Utsumi
Bullet cluster analog at z=0.5: collisional cluster gas has become separated fomr the collisionless galaxies and DM. Identify cluster using optical and weak lensing observations as part of DLS. Cluster is a dissociative merger. System is at least 0.7Gyr since first pass-through.
1110.4431
A grand rotation curve and DM halo in the MW galaxy
Sofue
Rotation curve of MW constructed, covering a wide range of radius (galactic center to 1Mpc); deconvolved into bulge, disk and halo components by least-squares fitting. Dark halo component fits well with NFw density profile. Fit yielded h=16.3 kpc and rho_0=7.37e-3 Msun/pc^3. Local dark matter density near the sun at R_0=8 kpc is estimated to be 6.8e-2 Msun/pc^3. Total mass inside the gravitational boundary of the galaxy at R~385 kpc (half distance to M31) is estimated to be M_h~9e11 Msun. Stellar baryon fraction of 5%. From the expected baryon fraction of local group, suggest baryons in the form of 1e6K gas fills the dark halo. This may contribute to the observed X-ray background.
1110.4635
Optimized detection of shear peaks in WL maps
Marian, Smith, Hilbert, Schneider
Use multiply-scaled filters to detect shear peaks down to S/N of 3, and you'll do better in constraining cosmology.
1110.4659
The imprint of the relative velocity between baryons and dark matter on the 21-cm signal from reionization
Bittner, Loeb
Post-recombination streaming of baryons through dark matter keeps baryons out of low mass (<1e6 Msun) haloes coherently on scales of a few comoving Mpc. Argued that this will have a large impact on the 21-cm signal before and after reionization, because it raises the minimum mass required to form ionizing sources. Using semi-numerical code, show that the impact of the baryon streaming effect on the 21 cm signal during reionization (redshifts z approximately 7-20) depends strongly on the cooling scenario assumed for star formation, and the corresponding virial temperature or mass at which stars form. For the canonical case of atomic hydrogen cooling at 1e4 Kelvin, the minimum mass for star formation is well above the mass of haloes that are affected by baryon streaming, and there are no major changes to existing predictions. For the case of molecular hydrogen cooling, find reionization is delayed by a change in redshift of approximately 2 [from what reference redshift?], and that more relative power is found in large modes at a given ionization fraction. But the delay in reionization is degenerate with astrophysical assumptions, such as the production rate of UV photons by stars.
* perhaps an interesting way to determine whether baryon streaming relative to DM affects the formation of first stars (ionization sources).
1110.4888
The effects of alignment and ellipticity on the clustering of galaxies
van Daalen, Angulo, White
* ignoring shapes will underestimate clustering on small (~2Mpc) scales, but it shouldn't affect BAO, or other large scale effects, probably {MG}
Effects of halo ellipticity and alignment with LSS on the galaxy correlation function. The effect of disrupting the alignment with larger-scale structure is a ~2% decrease in galaxy correlation function around r=1.8Mpc/h; sphericalizing the ellipsoidal distributions of galaxies within haloes decreases the correlation function by up to 20% for r<1Mpc/h. Similar relusts apply to power spectra and redshift-space correlation functions. Models such as those based on HOD, which adopt a spherically averaged profile for the galaxy distributions within haloes, will therefore significantly underestimate the clustering on sub-Mpc scales.
* must be careful of using HOD to do model fitting on galaxy correlation functions! {RN}
1110.4894
Gravitational lensing with 3d ray tracing
Killedar, Lasky, Lewis, Fluke
Distance-redshift relation suffers lensing-induced scatter due to (de)magnification due to WL by LSS. This can be quantified by the magnification probability distribution; predicting requires ray-tracing simulations. Standard, multiple thin-lens approximation is often used; to quantify the accuracy, developed code that performs ray-tracing without approximation. The efficiency and accuracy of this computationally challenging approach improved by careful choices of numerical parameters; the results are analyzed for the behavior of the ray-tracing code in the vicinity of Schwarzschild and NFW lenses. Preliminary comparisons are drawn with the multiple lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of z=0.5.
* where the f*** are the results, man? did they find the magnification probability distribution, or not? I guess this was simply a code-testing paper, testing just around Schwartzschild and NFW lenses, showing "preliminary comparisons".
1110.4913
The impact of high spatial frequency atmospheric distortions on WL measurements
Heymans, Rowe, Hoekstra, Miller, Erben, Kitching, Van Waerbeke
Precise measurement of PSF across the imaging data important; want to model the high spatial frequency variation properly. Analyze dense stellar fields imaged at the CFHT to quantify degree of high spatial frequency variation in ground-based imaging PSF and compare results to models of atmospheric turbulence. Data shows anisotropic turbulence pattern with an orientation independent of the wind direction and wind speed. Find the amplitude of the high spatial frequencies to decrease with increasing exposure time, as t^-0.5, and find negligibly small atmospheric contribution to the PSF ellipticity variation for exposure times t>180 seconds. For future surveys analyzing shorter exposure data, anisotropic turbulence will need to be taken into account as the amplitude of the correlated atmospheric distortions becomes comparable to a cosmological lensing signal on scales less than 10 arcminutes. Effect can be mitigated by correlating galaxy shear measured on exposures imaged with a time separation greater than 50 seconds, for which spatial turbulence patterns are uncorrelated.
* at least 50 second exposure, with multiple exposure to correlate, to minimize psf ellipticity due to atmospheric turbulence correlation; >180 second exposure to make the atmospheric contribution negligibly small.
The impact of high spatial frequency atmospheric distortions on WL measurements
Heymans, Rowe, Hoekstra, Miller, Erben, Kitching, Van Waerbeke
Precise measurement of PSF across the imaging data important; want to model the high spatial frequency variation properly. Analyze dense stellar fields imaged at the CFHT to quantify degree of high spatial frequency variation in ground-based imaging PSF and compare results to models of atmospheric turbulence. Data shows anisotropic turbulence pattern with an orientation independent of the wind direction and wind speed. Find the amplitude of the high spatial frequencies to decrease with increasing exposure time, as t^-0.5, and find negligibly small atmospheric contribution to the PSF ellipticity variation for exposure times t>180 seconds. For future surveys analyzing shorter exposure data, anisotropic turbulence will need to be taken into account as the amplitude of the correlated atmospheric distortions becomes comparable to a cosmological lensing signal on scales less than 10 arcminutes. Effect can be mitigated by correlating galaxy shear measured on exposures imaged with a time separation greater than 50 seconds, for which spatial turbulence patterns are uncorrelated.
* at least 50 second exposure, with multiple exposure to correlate, to minimize psf ellipticity due to atmospheric turbulence correlation; >180 second exposure to make the atmospheric contribution negligibly small.
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