Thursday.
1211.1377
Direct detection of self-interacting dark matter
Vogelsberger, Zavala
Expected DM detection signal taking into account different self-scattering models. Models with constant and velocity dependent cross sections, which are consistent with observational constraints, lead to distinct signatures in the velocity distribution, because non-thermalised features found in the CDM distribution are thermalized through particle scattering. Depending on the model, self-interaction can lead to a 10% reduction of the recoil rates at high energies, corresponding to a minimum speed that can cause recoil larger than 300 km/s, compared to the CDM case. (5% at lower energies). Amplitude of the annual modulation signal can increase by up to 25%, and the day of maximum amplitude can shift by about 2 weeks with respect to the CDM expectation; the exact day of phase reversal of the modulation signal can also differ by about a week between different models (models with velocity dependent cross sections peaking at typical dwarf galaxy velocity lead only to minor changes in signal, while allowed constant cross section models lead to significant changes). Conclude that different self-interacting DM scenarios might be distinguished from each other through the details of direct detection signals; detailed constraints on the intrinsic properties of DM based on null detections should take into account the possibility of self-scattering and the resulting effects on the detector signal [is self-scattering consistent with LSS evolution?]
1211.1379
The redshift-sapce cluster-galaxy cross-correlation function: I. Modeling galaxy infall onto Millennium simulation clusters and SDSS groups
Zu, Weinberg
Large scale infall of galaxies around massive clusters provide a potentially powerful diagnostic of structure growth, DE and cosmological deviation from GR. Develop and test a method to recover galaxy infall kinematics (GIK) from measurement of the z-space cluster-galaxy cross-correlation function xi_cg(r_p, r_pi). Using galaxy and halo samples from the Millennium simulation, calibrate an analytic model of the galaxy kinematic profiles comprised of a virialized component with an isotropic Gaussian velocity distribution and an infall component described by a skewed 2d t-distribution with a characteristic infall velocity v_r and separate radial and tangential dispersions. We show that convolving the real-space cross-correlation function with this velocity distribution accurately predicts the z-space xi_cg, and show that measurements of xi_cg can be inverted to recover the 4 distinct elements of the GIK profiles, in turn providing diagnostics of cluster mass profiles. Expect characteristic infall velocity v_r(r) to be insensitive to galaxy formation physics that can affect velocity dispersions within halos. Measure xi_cg for rich galaxy groups to recover GIK profiles in two bins of central galaxy stellar mass; the high mass bin has v_r(r) curve very similar to that of 1e14 Msun halos in the Millennium simulation, and the recovered kinematics follow the expected trends with mass. GIK modling of cluster-galaxy cross-correlations can be valuable complement to stacked WL analysis, allowing novel tests of modified gravity theories that seek to explain cosmic acceleration.
1211.1387
Characterizing the satellites of massive galaxies up to z~2: young populations to build the outskirts of nearby massive galaxies
Marmol-Queralto, Trujillo, ... et al
The accretion of minor satellites is currently proposed as the most likely mechanism to explain the significant size evolution of the massive galaxies during the last ~10 Gyr. In this paper we investigate the rest-frame colors and the average stellar ages of satellites found around massive galaxies (M* of 1e11 Msun) since z~2. Find: satellites have bluer colors than their central galaxies [what data or simulation are they taking about???]. When exploring the stellar ages of the galaxies, find that the satellites have similar ages to the massive galaxies that host them at high redshifts, while at lower redshifts they are, on average, ~1.5 Gyr younger. If our satellite galaxies create the envelope of nearby massive galaxies, our results would be compatible with the idea that the outskirts of those galaxies are slightly younger, metal-porer and with lower [alpha/Fe] abundance ratios than their inner regions. [so I guess this is from simulations?]
1211.1394
Kickstarting reionization with the first black holes: the effects of second-order perturbation theory in pre-reioniation volumes
Holley-Bockelmann, Wise, Sinha
Both Zeldovich approximation and Lagrangian perturbation theory produce present-day DM halo mass functions, but LPT drives more rapid evolution of dense regions, increasing the occurrence of rare massive objects; an effect that is most pronounced at high redshift. LPT can harbor more Pop III stars and their BH remnants, and they produce them earlier. Although the differences between LPT and ZA MF are nearly erased by z=6, this small boost to the number and mass of BHs more than doubles the reionized volume of the early universe. Discuss implications for reionizatin and massive BH growth.
1211.1397
Cross-correlations as a carbon monoxide detector
Pullen, Chang, Dore, Lidz
CO gas content as a function of z can be quantified by 3d fluctuation power spectra; is a LSS tracer; cross-correlating CO emission with other tracers of LSS offers a way to measure the emission as a function of scale and redshift. Illustrate by: attempt to extract redshifted CO emissions embedded in WMAP data. Cross-correlate all-sky WMAP7 with LSS data sets (photomoetric quasar sample, LRG sample from SDSS (DR6/7, respectively). No cross-correlation signal with CO(1-0) nor CO(2-1) lines detected, mainly due to instrumental noise in WMAP. Discuss cross-correlation signal from tSZ effect and dust as potential contaminants.
1211.1421
The Sloan bright arcs survey: ten strong gravitational lensing clusters and evidence of overconcentration
Wiesner et al
As the title says.
1211.1632
Sunyaev-Zeldovich-measured pressure profiles fomr the Bolocam X-ray/SZ galaxy cluster sample
Sayers et al
Describe SZ measurements and analysis of ICM pressure profiles of a set of 45 massive galaxy clusters imaged using bolocam at the caltech submillimeter observatory. Use masses determined from Chandra X-ray to scale with each cluster's profile by the overdensity radius R500 and the mass-and-redshift-dependent normalization factor P500. Deproject the average pressure profile of our sample into 13 log-spaced radial bins between 0.07R500 and 3.5 R500. Find that a generalized NFW profile describes data with sufficient goodness-of-fit and best-fit parameters (C500, alpha, beta, gamma, P0). Also use the X-ray data to define cool-core and disturbed subsamples of clusters, and constrain the average pressure profiles of each of these subsamples. Find that, the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R>~0.15R500 (cool core show indication of higher pressure at smaller scales). In addition, place simultaneous constraints on the mass scaling of cluster pressure profiles, ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R500 and 2.0R500. The scatter among profiles is minimized at radii between 0.2R500 and 0.5R500, with a value of 20% [should do this wrt concentration radius, but I suppose that's not easy to do]. The best-fit mass scaling has a power-law slope of 0.49, which is shallower than the nominal prediction of 2/3 from self-similar hydrostatic equilibrium models. These results for the intrinsic scatter and mass scaling are largely consistent with previous analysis, most of which have relied heavily on x-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample.
1211.1664
The faint end of the cluster galaxy luminosity function at high redshift
Mancone, et al
Measure the faint end slope of the galaxy LF for cluster galaxies at 1<z<1.5 with Spitzer. Investigate whether the slope alpha differs from that of the field LF at these redshifts, and with the cluster LF at low z. The latter is of particular interest, as low-luminosity galaxies are expected to undergo significant evolution. Use 7 high-z spectrscopically confirmed galaxy clusters drawn from the IRA shallow cluster survey to measured LF down to M*+3 (3.6 um) and M*+2.5 (4.5 um). THe summed LF at median cluster redshift (z=1.35) is well fit by a Schechter distribution with alpha[3.6]=-0.97 and alpha[4.5]=-0.91, consistent with a flat faint end slope and is in agreement with meausrements of the field LSf in similar bands at these z. A comparison to alpha in low-z clusters finds no statistically significant evidence of evolution. Combined with past studies which slow that M* is passively evolving out to z~1.3, this means that the shape of the cluster LF is largely in place by z~1.3. This suggests that the processes that govern the build up of the mass of low-mass cluster galaxies have no net effect on the faint end slope of the cluster LF at z<1.3.
1211.1377
Direct detection of self-interacting dark matter
Vogelsberger, Zavala
Expected DM detection signal taking into account different self-scattering models. Models with constant and velocity dependent cross sections, which are consistent with observational constraints, lead to distinct signatures in the velocity distribution, because non-thermalised features found in the CDM distribution are thermalized through particle scattering. Depending on the model, self-interaction can lead to a 10% reduction of the recoil rates at high energies, corresponding to a minimum speed that can cause recoil larger than 300 km/s, compared to the CDM case. (5% at lower energies). Amplitude of the annual modulation signal can increase by up to 25%, and the day of maximum amplitude can shift by about 2 weeks with respect to the CDM expectation; the exact day of phase reversal of the modulation signal can also differ by about a week between different models (models with velocity dependent cross sections peaking at typical dwarf galaxy velocity lead only to minor changes in signal, while allowed constant cross section models lead to significant changes). Conclude that different self-interacting DM scenarios might be distinguished from each other through the details of direct detection signals; detailed constraints on the intrinsic properties of DM based on null detections should take into account the possibility of self-scattering and the resulting effects on the detector signal [is self-scattering consistent with LSS evolution?]
1211.1379
The redshift-sapce cluster-galaxy cross-correlation function: I. Modeling galaxy infall onto Millennium simulation clusters and SDSS groups
Zu, Weinberg
Large scale infall of galaxies around massive clusters provide a potentially powerful diagnostic of structure growth, DE and cosmological deviation from GR. Develop and test a method to recover galaxy infall kinematics (GIK) from measurement of the z-space cluster-galaxy cross-correlation function xi_cg(r_p, r_pi). Using galaxy and halo samples from the Millennium simulation, calibrate an analytic model of the galaxy kinematic profiles comprised of a virialized component with an isotropic Gaussian velocity distribution and an infall component described by a skewed 2d t-distribution with a characteristic infall velocity v_r and separate radial and tangential dispersions. We show that convolving the real-space cross-correlation function with this velocity distribution accurately predicts the z-space xi_cg, and show that measurements of xi_cg can be inverted to recover the 4 distinct elements of the GIK profiles, in turn providing diagnostics of cluster mass profiles. Expect characteristic infall velocity v_r(r) to be insensitive to galaxy formation physics that can affect velocity dispersions within halos. Measure xi_cg for rich galaxy groups to recover GIK profiles in two bins of central galaxy stellar mass; the high mass bin has v_r(r) curve very similar to that of 1e14 Msun halos in the Millennium simulation, and the recovered kinematics follow the expected trends with mass. GIK modling of cluster-galaxy cross-correlations can be valuable complement to stacked WL analysis, allowing novel tests of modified gravity theories that seek to explain cosmic acceleration.
1211.1387
Characterizing the satellites of massive galaxies up to z~2: young populations to build the outskirts of nearby massive galaxies
Marmol-Queralto, Trujillo, ... et al
The accretion of minor satellites is currently proposed as the most likely mechanism to explain the significant size evolution of the massive galaxies during the last ~10 Gyr. In this paper we investigate the rest-frame colors and the average stellar ages of satellites found around massive galaxies (M* of 1e11 Msun) since z~2. Find: satellites have bluer colors than their central galaxies [what data or simulation are they taking about???]. When exploring the stellar ages of the galaxies, find that the satellites have similar ages to the massive galaxies that host them at high redshifts, while at lower redshifts they are, on average, ~1.5 Gyr younger. If our satellite galaxies create the envelope of nearby massive galaxies, our results would be compatible with the idea that the outskirts of those galaxies are slightly younger, metal-porer and with lower [alpha/Fe] abundance ratios than their inner regions. [so I guess this is from simulations?]
1211.1394
Kickstarting reionization with the first black holes: the effects of second-order perturbation theory in pre-reioniation volumes
Holley-Bockelmann, Wise, Sinha
Both Zeldovich approximation and Lagrangian perturbation theory produce present-day DM halo mass functions, but LPT drives more rapid evolution of dense regions, increasing the occurrence of rare massive objects; an effect that is most pronounced at high redshift. LPT can harbor more Pop III stars and their BH remnants, and they produce them earlier. Although the differences between LPT and ZA MF are nearly erased by z=6, this small boost to the number and mass of BHs more than doubles the reionized volume of the early universe. Discuss implications for reionizatin and massive BH growth.
1211.1397
Cross-correlations as a carbon monoxide detector
Pullen, Chang, Dore, Lidz
CO gas content as a function of z can be quantified by 3d fluctuation power spectra; is a LSS tracer; cross-correlating CO emission with other tracers of LSS offers a way to measure the emission as a function of scale and redshift. Illustrate by: attempt to extract redshifted CO emissions embedded in WMAP data. Cross-correlate all-sky WMAP7 with LSS data sets (photomoetric quasar sample, LRG sample from SDSS (DR6/7, respectively). No cross-correlation signal with CO(1-0) nor CO(2-1) lines detected, mainly due to instrumental noise in WMAP. Discuss cross-correlation signal from tSZ effect and dust as potential contaminants.
1211.1421
The Sloan bright arcs survey: ten strong gravitational lensing clusters and evidence of overconcentration
Wiesner et al
As the title says.
1211.1632
Sunyaev-Zeldovich-measured pressure profiles fomr the Bolocam X-ray/SZ galaxy cluster sample
Sayers et al
Describe SZ measurements and analysis of ICM pressure profiles of a set of 45 massive galaxy clusters imaged using bolocam at the caltech submillimeter observatory. Use masses determined from Chandra X-ray to scale with each cluster's profile by the overdensity radius R500 and the mass-and-redshift-dependent normalization factor P500. Deproject the average pressure profile of our sample into 13 log-spaced radial bins between 0.07R500 and 3.5 R500. Find that a generalized NFW profile describes data with sufficient goodness-of-fit and best-fit parameters (C500, alpha, beta, gamma, P0). Also use the X-ray data to define cool-core and disturbed subsamples of clusters, and constrain the average pressure profiles of each of these subsamples. Find that, the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R>~0.15R500 (cool core show indication of higher pressure at smaller scales). In addition, place simultaneous constraints on the mass scaling of cluster pressure profiles, ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R500 and 2.0R500. The scatter among profiles is minimized at radii between 0.2R500 and 0.5R500, with a value of 20% [should do this wrt concentration radius, but I suppose that's not easy to do]. The best-fit mass scaling has a power-law slope of 0.49, which is shallower than the nominal prediction of 2/3 from self-similar hydrostatic equilibrium models. These results for the intrinsic scatter and mass scaling are largely consistent with previous analysis, most of which have relied heavily on x-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample.
1211.1664
The faint end of the cluster galaxy luminosity function at high redshift
Mancone, et al
Measure the faint end slope of the galaxy LF for cluster galaxies at 1<z<1.5 with Spitzer. Investigate whether the slope alpha differs from that of the field LF at these redshifts, and with the cluster LF at low z. The latter is of particular interest, as low-luminosity galaxies are expected to undergo significant evolution. Use 7 high-z spectrscopically confirmed galaxy clusters drawn from the IRA shallow cluster survey to measured LF down to M*+3 (3.6 um) and M*+2.5 (4.5 um). THe summed LF at median cluster redshift (z=1.35) is well fit by a Schechter distribution with alpha[3.6]=-0.97 and alpha[4.5]=-0.91, consistent with a flat faint end slope and is in agreement with meausrements of the field LSf in similar bands at these z. A comparison to alpha in low-z clusters finds no statistically significant evidence of evolution. Combined with past studies which slow that M* is passively evolving out to z~1.3, this means that the shape of the cluster LF is largely in place by z~1.3. This suggests that the processes that govern the build up of the mass of low-mass cluster galaxies have no net effect on the faint end slope of the cluster LF at z<1.3.
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