Wednesday.
1404.1920
Dark matter haloes in galaxies and globular cluster populations
Hudson, Harris, Harris
Combine a new, comprehensive database for gobbler cluster populations in all types of galaxies with a new calibration of galaxy halo masses based entirely on WL. Correlating these two sets of data, find that the mass ratio eta==M_GCS/M_h (total mass in GCs, divided by halo mass) is essentially constant at <eta>~4e-5, strongly confirming earlier suggestions in the literature. Globular clusters are the only known stellar population that formed in essentially direct proportion to host galaxy halo mass. The intrinsic scatter in eta appears to be at most 0.2 dex; argue that some of this scatter is due to differing degrees of tidal stripping of the globular cluster systems between central and satellite galaxies. Suggest that this correlation can be understood if most globular clusters form at very early stages in galaxy evolution, largely avoiding the feedback processes that inhibited the bulk of field-SF in their host galaxies. The actual mean value of eta also suggests that about 1/4 of the initial bass mass present in protogalaxies collected into GMCs large enough to form massive, dense star clusters. Finally, calibration of <eta> indicates that the halo masses of the MW and M31 are 1.2e12 Msun and 3.9e12 Msu, respectively.
1404.1933
Cross-correlation of cosmic infrared background anistropies with large scale structures
Serra, … Doré, … White
Measure the X-PS between LRGs from DR8 and CIB from Planck and IRIS at 353, 545, 857, and 3000 Ghz (850,500,350,100 um, respectively) in the multipole range 100<ell<1000. Using approximately 6.5e5 photometrically determined LRGs in 7760 degsq of the Northern Hemisphere in 0.45<z<0.65, and modeling the CIB anisotropies with an extended version of the halo model, confirm the basic picture obtained from recent analysis of CIB anisotropies with Herschel and Planck that the most efficient halo mass at hosting SF galaxies is log (Meff/Msun)=12.8pm0.2. Also estimate the percentage of CIB anisotropies correlated with LRGs as approximately 11.8, 3.9,1.8 and 1.0% of the total at 3000,857,545, and 535 GHz, respectively. At z~0.55, the bias of CIB galaxies wrt the DM density field has the value b_CIB~1.45, and mean dust temperature of CIB galaxies is T_d=26K.
1404.1938
The local dark matter density
Read
Review current efforts to measure the mean density of DM near the Sun. This encodes dynamical information about the Galaxy and is also of importance of 'direct detection' DM experiments. Discuss theoretical expectations in current cosmology; the theory behind mass modeling of the Galaxy; and show how combining local and global measures pores the shape of the MW DM halo and the possible presence of a 'dark disc'. Stress the strengths and weaknesses of different methodologies and highlight the continuing need for detailed tests on mock data - particularly in the light of recently discovered evidence for disequilibria in the MW disc. Highlight several recent measurements in order to increasing data complexity and prior, and correspondingly, decreasing formal error bars. Comparing these measurements with spherical extrapolations from the MW's rotation curve, show that the MW is consistent with having a spherical DM halo at the Solar position R0. The very latest measures based on ~10k stars from SDSS appear to favor little hallo flattening at R0, suggesting that the Galaxy has a rather weak DM disc, with a correspondingly quiescent merger history.
1404.2123
Parameterizing the stellar haloes of galaxies
D'Souza, Kauffmann, Wang, Vegetti
Study the stellar haloes of galaxies out to 70-100 kpc as function of M* and galaxy type by stacking aligned r and g band images from a sample of 45k galaxies from DR9 in 0.06<z<0.1 and in the mass range 1e10.0Msun<M*<1e11.4Msun. ...Find that the ellipticity of the stellar halo is a function of galaxy stellar mass and that the haloes of high concentration (C>2.6) galaxies are more elliptical than those of low concentration (C<2.6). The g-r color profile of high concentration galaxies reveals that the g-r color of the stellar population in the stellar halo is bluer than in the main galaxy, and the color of the stellar halos is refer for higher mass galaxies. Further demonstrate that the full two-dimensional surface intensity distribution of the galaxy stacks can only be fit through multi-component Sersic models. Using the fraction of light in the outer component of the models as a proxy for the fraction of accreted stellar light, show that this fraction is a function of stellar mass and galaxy type. For high concentration galaxies, the fraction of accreted stellar light rises from 30 to 70% for galaxies in the given M* range. The fraction of accreted light is much smaller in low concentration systems, increasing from 2% to 25% over the same mass range. This work provides constraints for the theoretical understanding of the formation of stellar haloes of galaxies.
1404.2241
The bias of weighted dark matter haloes from peak theory
Verde, Jiminez, .. Heavens, etal
Give analytical form for the weighted correlation function of peaks in a Gaussian random field. In a cosmological context, this describes the formation bias. Show its validity and applicability to the evolved cosmo density field and halo field, using Gaussian random field realizations and DM N-body numerical sims. Using results from peak theory, compute the bias of peaks (and DM haloes) and show that it reproduces results from the simulations at the O(10%) level. Analytical formula for the bias predicts a scale-dependent bias with two characteristics: a broad band shape which, however, is most affected by the choice of weighting scheme and evolution bias, and a more robust, narrow feature localized at the BAO scale, an effect that is confirmed in simulations. This scale-dependent bias smooths the BAO feature but, conveniently, does not move it. Provide a simple analytic formula to describe this effect. Envision that our analytic solution will be of use for galaxy surveys that exploit galaxy clustering.
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