Day 54

1107.5910
Testing homogeneity with the fossil record of galaxies
Heavens, Jiminez, Maartens


Homogeneity is the basic assumption for both standard GR and modified gravity scenarios, and forms basis for interpreting CMB and galaxy distribution.


Probe homogeneity of universe via reconstruction of key intrinsic properties of galaxies as a function of property along their worldlines.  (which properties are they talking about?)  Compare properties at the same proper time for other galaxies.  Compute lookback time using radial BAO; time along galaxy world line from stellar physics.  This won't prove homogeneity, but will provide consistency test.


1107.5932
A study of gravitational lens chromaticity with the HST
Munoz, Mediavilla, Kochanek, Falco, Mosquera


Study 6 gravitational lens with HST-ACS; study flux ratios bewteen lens images in 6 filters from 2200A to 8140A.  Construct UV extinction curves in 3 of the systems; characterize the properties of the dust relative to MW and LMC/SMC.  Chromatic microlensing detected in one; study physical properties of quasar accretion disk.  Model disk as gaussian; r_s estimated as 4-8 light days and chromatic power index p ~ 1.1 for log or linear prior on r_s.  The other 2 systems provided no useful estimates of extinction or chromatic microlensing.


1011.1310
Intracluster supernovae in the multi-epoch nearby cluster survey
Sand et al


58 X-ray clusters, 23 intra-cluster (no host galaxy) SNIa.  4 SNe do not have host galaxy (indicator of the mass of the intracluster medium).  It seems to agree with the X-ray ICM estimate.  See Figure 7.


1107.6046
The progenitor mass of SN 2011dh from stellar populations analysis
Murphey, Jennings, Williams, Dalcanton, Dolphin


Nearby SNe, resolved progenitor in M51.  Stellar evolution theory discrepancy.  Estimate mass of progenitor.  13 Msun vs 18-21 Msun (two different results, same data).  Color + abs magnitude used to determine age.  Use stellar population analysis for age/mass consistency; conclude that 13 Msun progenitor is most likely.


1107.5740
Merger induced scatter and bias in the cluster mass--SZ effect scaling relation
Kraus, Pierpaoli, 


Scaling relation between tSZ and cluster mass:  what induces scatter?  Use simulations and look  at mergers.  Not a log-normal relation.  (1) Concentration of the halo: the more concentrated, more SZ signal.  (2) Mergers: cause asymmetric scatter, bias mass measurements lower.  (other studies gives higher SZ mass estimates--at the first passes).  Messy, but systematically lowers the SZ signal.  Must correct the mass estimates based on the morphology (if doing cosmology). 



1008.3491
Constraints on intrinsic alignment contamination of weak lensing surveys
using the MegaZ-LRG sample
Joachimi, Mandelbaum, Abdalla, Bridle


Correlation between large-scale galaxy density field and intrinsic
galaxy shapes are evidences of galaxy intrinsic alignments.  This is
a major systematic in cosmic shear, but also give insight to
evolution and formation of galaxies.  Use 800k MegaZ-LRG samples,
and make measurements with photo-z sample.  Constrain intrinsic alignment
model for red galaxies over z~0 to 0.7 and luminosity (4mag).
Include photo-z scattering into the modeling.  For r_p > 6 Mpc/h: correlation
function of galaxy position to shape is consistent with scaling with r_p
and redshift of a revised nonlinear version of the linear alignment model
for "all samples" (?).  Redshift dependence in the form of (1+z)^n is
constrained to n=-0.3\pm0.8 (1 sigma--not much z dependence).
Additional dependence on luminosity
of the form L^b with b=1.1\pm0.3 required (brighter, more aligned).
Normalization (amplitude) of intrinsic alignment power spectrum is
0.077\pm0.008 rho_cr for galaxies at z=0.3 and abs. r mag of -22.
Assuming no intrinsic alignments for blue galaxies, the bias on cosmo
parameters for a tomographic CFHTLS-like lensing survey show that the
mean bias and uncertainty are smaller than the 1 sigma statsitical
errors when all samples combined are used.  Additional MegaZ-LRG data
reduces the uncertainty in the intrinsic alignment bias on cosmological
parameters by factors of 3 to 7.


* what is r_p?
* what is the linear alignment model?

1010.0911

A Bayesian analysis of the 27 highest energy cosmic rays detected by the Pierre Auger Observatory

Watson, Mortlock, Jaffe

UHECRs (ultra-high energy cosmic rays) is thought to be generated by AGNs, but there is currently no conclusive evidence.  Correlate CHECR arrival direction and nearby AGNs, strongest detection coming from a sample of 27 UHECRs detected by PAO.  But these results were based on statistical methodology that ignored, e.g., UHECR arrival energies and directions, but also some problematic fine-tuning of the correlation parameters.  Here a fully Bayesian analysis of the PAO data presented; makes use of more information, find that a fraction of 15% of UHECRs originate from known AGNs in the VCV (Veron-Cetty & Veron) catalogue.  Rules out all UHECRs comes from VCV AGNs, but small possibility of PAO-AGN correlation is coincidental remains (15% is 200x probable as 0%).

1104.1566

The shape of dark matter haloes in the Aquarius Simulations: evolution and memory

Vera-Ciro, Sales, Helmi, Frenk, Navarro, Springel, Vogelsberger, White

Use Aquarius N-body simulation to investigate the mechanism that determine the shape of MW-type DM halos.  (What are the shape of MW DM halos?)  The shapes are measured at the instantaneous virial radius.  Shape of halos evolve from prolate at early times to more triaxial/oblate at late time.  Shape correlates with the infalling material: prolate correlates to when haloes are fed through narrow filaments which characterizes the early epochs of halo assembly, whereas the accretion is more isotropic at late times, resulting in a triaxial/oblate halo shape.   At z=0, the past history of each halo is imprinted in their shapes at different radii (!), which exhibit a variation from prolate in the inner regions to triaxial/oblate in the outskirts.  If Aquarius halos are fair representation of MW-like 1e12 Msun objects, the smape of DM haloes is a complex, time-dependent property, with each radial shell retaining memory of the conditions at the time of collapse.

* I wonder how this reconciles with Neil Dalal's theory?

1107.5169
Clipping the cosmos: the bias and bispectrum of large scale structure
Simpson, James, Heavens, Heymans


Introduce new technique which enables extraction of useful information from the bispectrum of galaxies well beyond the conventional limits of perturbation theory.  This method improves measurements of galaxy bispectrum, permitting the maximum wavenumber at z=0 to be 0.1 h/Mpc to 0.5 h/Mpc and perhaps beyond, with correspondingly large improvements in the determination of galaxy bias.


1107.6003
Improved constrains on Type Ia SN host galaxy properties using multi-wavelength photometry and their correlations with SN properties
Gupta, D'Andrea, Sako, Conroy, Smith, Bassett, Frieman, Garnavich, Jha, Kessler, Lampeitl, Marriner, Nichol, Schneider


Improve estimates of stellar mass and mass-weighted average age of SNIa hosts; combine UV(GALEX) and near IR (UKIDSS) photometry with optical (SDSS) photometry.  SDSSII SNe survey, 206 SNe Ia.  Median redshift of 0.2.  Evidence of correlation (<2 sigma) between the residuals of SNe Ia from best-fit Hubble and mass-weighted average age of host galaxies.  Trend: older galaxies host SNe Ia that are brighter than average after standard ligh-curve corrections are made.  At ~3 sigma, more massive galaxies often host brighter SNe Ia after light-curve correction.