Day 760

Wednesday, Oxford.

1410.1531
The photo heating of the intergalactic medium in synthesis models of the UV background
Puchwein, ... Madam, et al

Compare cosmo hydro sims combined with the homogeneous metagalactic UV background (UVB) of Haard & Madau to observations of the Lyman-alpha forest that are sensitive to the thermal and ionization state of the IGM.  The transition from optically thick to thin photo heating predicted by the simple one-zone, radiative transfer model implemented by HM2012 predicts a thermal history that is in good agreement with the observed rise of the IGM temperature at z~3 if accounting for the expected evolution of the volume filling factor of HeIII.  Simulations indicate that there may be, however, some tension between the observed peak in the temperature evolution and the rather slow evolution of the HeII opacities suggested by recent HST measurements.  The HM2012 UVB also underpredicts the metagalactic hydrogen photoionization rate required by the simulations to match the observed opacity of the forest and z>4 and z<2.

1410.1535
The sizes of $z\sim6-8$ lensed galaxies from the Hubble frontier fields Abell 2744 data
Kawamata, ... Oguri, et al

Measure lensing-distorted Sersic profiles of z~6-8 dropout galaxies: 31 z~6-7 and 8 z~8 galaxies.  In general, the larger the brighter, and redder.  Conforms with previous result of 2.5<z<12 galaxy size results.  Find that the ratio of r_c to virial radius is virtually constant at 3.5pm0.1% over a wide z range, where the virial radii of hosting DM haloes are derived based on the abundance matching.  This constant ratio is consistent with the disk formation model by Mo+1998 with the fraction of angular momentum and mass with haloes confined in the disks are similar.  A comparison with various types of local galaxies indicates that the galaxies here are most similar to circumnuclear SF regions of barred galaxies in the seines that a sizable amount of stars are forming in a very small area.

1410.1617
Lagrangian perturbation theory at one loop order: successes, failures, and improvements
Vlah, Seljak, Baldauf

Apply the convolved Lagrangian perturbation theory (CLPT) formalism, in which one can express the matter density PS in terms of integrals over a function of cumulants of the displacement field, allowing for a resummation of the terms, to evaluate the full one loop PS.  Keep the cumulants up to third order, extending the Zel'dovich approximation and providing the PS analogous to the calculations recently performed for the correlation function.  Compare the results to the N-body sims and to the Lagrangian perturbation simulations up to the second order.  Find that the analytic calculations are in good agreement with the LPT simulations, but when compared to full N-body sims, find that while one loop calculations improve uptown the Zel'dovich approximation in the PS, they still significantly lack power.  As found previously in the correlation function one loop CLPT improves slightly against Zel'dovich above 30 Mpc/h, but is actually worse than Zel'dovich below that.  Investigate the deficiencies of the CLPT approach and argue that main problem of CLPT is its inability to trap particles inside DM haloes, which leads to an overestimate of the small scale power of the displacement field and to an underestimate of the small scale power from one halo term effects.  Model this using the displacement field damped at a NL scale (CLPTs).  To explore this in more detail, decompose the PS and correlation function into 3 additive components: Zel'dovich, residual BAO wiggle, and residual road band.  One loop CLPT predicts small modification to BAO wiggles that are enhanced in CLPTs, with up to 5% corrections to correlation function around BAO scale.

1410.1687
Can an inhomogeneous metric be detected with the baryonic acoustic oscillation peak?
Roukema et al

Void--hyperbolic; superclusters--positively curved space; a best-fit metric should be close to the void case modeled as a constant-curvature metric on a given time slice.  Thus, comoving separations near superclusters should be compressed in comparison to the homogeneous case.  Demonstrate this by measuring the 2pt auto-correlation function on comoving scales in order to detect shifts in the BAO peak for LRG in SDSS DR7.  In tangential directions, subsets of pairs overlapping with superclusters or voids show the BAO peak.  The tangential BAO peak location for overlap with superclusters is 4.3pm1.6 Mpc/h less than for LRG pairs unselected for supercluster overlap, and 6.6 Mpc/h less than that of the complementary pairs.  Liivamagi+ superclusters give corresponding differences of 3.7 and 6.3 Mpc/h, respectively.  Found moderately significant evidence that the BAO peak location for supercluster-overlapping pairs is compressed by about 6% compared to that of the complementary sample, providing a potential challenge to FLRW models and a benchmark for predictions from back reaction models.