The Effect of Foreground Mitigation Strategy on EoR Window Recovery

The removal of the Galactic and extragalactic foregrounds remains a major challenge for those wishing to make a detection of the Epoch of Reionization 21-cm signal. Multiple methods of modelling these foregrounds with varying levels of assumption have been trialled and shown promising recoveries on simulated data. Recently however there has been increased discussion of using the expected shape of the foregrounds in Fourier space to define an EoR window free of foreground contamination. By carrying out analysis within this window only, one can avoid the foregrounds and any statistical bias they might introduce by instead removing these foregrounds. In this paper we discuss the advantages and disadvantages of both foreground removal and foreground avoidance. We create a series of simulations with noise levels in line with both current and future experiments and compare the recovered statistical cosmological signal from foreground avoidance and a simplified, frequency independent foreground removal model. We find that while, for current generation experiments, foreground avoidance enables a better recovery at $k_{perp} > 0.6 \mathrm{Mpc}^{-1}$, foreground removal is able to recover significantly more signal at small $k_{los}$ for both current and future experiments. We also relax the assumption that the foregrounds are smooth by introducing a Gaussian random factor along the line-of-sight and then also spatially. We find that both methods perform well for foreground models with line-of-sight and spatial variations around $0.1\%$ however at levels larger than this foregrounds removal shows a greater signal recovery.Comment: 14 pages, 10 figures, accepted by MNRA

Detection of correlated galaxy ellipticities on CFHT data: first evidence for gravitational lensing by large-scale structures

We report the detection of a significant (5.5 sigma) excess of correlations between galaxy ellipticities at scales ranging from 0.5 to 3.5 arc-minutes. This detection of a gravitational lensing signal by large-scale structure was made using a composite high quality imaging survey of 6300 arcmin^2 obtained at the Canada France Hawaii Telescope (CFHT) with the UH8K and CFH12K panoramic CCD cameras. The amplitude of the excess correlation is 2.2\pm 0.2 % at 1 arcmin scale, in agreement with theoretical predictions of the lensing effect induced by large-scale structure.We provide a quantitative analysis of systematics which could contribute to the signal and show that the net effect is small and can be corrected for. We show that the measured ellipticity correlations behave as expected for a gravitational shear signal. The relatively small size of our survey precludes tight constraints on cosmological models. However the data are in favor of cluster normalized cosmological models, and marginally reject Cold Dark Matter models with (Omega=0.3, sigma_8<0.6) or (Omega=1, sigma_8=1). The detection of cosmic shear demonstrates the technical feasibility of using weak lensing surveys to measure dark matter clustering and the potential for cosmological parameter measurements, in particular with upcoming wide field CCD cameras.Comment: 19 pages. 19 Figures. Revised version accepted in A&

The effect of environment on star forming galaxies at redshift 1 - First insight from PACS

We use deep 70, 100 and 160 um observations taken with PACS, the Photodetector Array Camera and Spectrometer on board of Herschel, as part of the PACS Evolutionary Probe (PEP) guaranteed time, to study the relation between star formation rate and environment at redshift ~ 1 in the GOODS-S and GOODS-N fields. We use the SDSS spectroscopic catalog to build the local analog and study the evolution of the star formation activity dependence on the environment. At z ~ 1 we observe a reversal of the relation between star formation rate and local density, confirming the results based on Spitzer 24 um data. However, due to the high accuracy provided by PACS in measuring the star formation rate also for AGN hosts, we identify in this class of objects the cause for the reversal of the density-SFR relation. Indeed, AGN hosts favor high stellar masses, dense regions and high star formation rates. Without the AGN contribution the relation flattens consistently with respect to the local analog in the same range of star formation rates. As in the local universe, the specific star formation rate anti-correlates with the density. This is due to mass segregation both at high and low redshift. The contribution of AGN hosts does not affect this anti-correlation, since AGN hosts exhibit the same specific star formation rate as star forming galaxies at the same mass. The same global trends and AGN contribution is observed once the relations are studied per morphological type. We study the specific star formation rate vs stellar mass relation in three density regimes. Our data provides an indication that at M/M_{\odot} > 10^{11} the mean specific star formation rate tends to be higher at higher density, while the opposite trend is observed in the local SDSS star forming sample.Comment: 10 pages, 16 figures, accepted for publication on A&

Detection of the pairwise kinematic Sunyaev-Zel'dovich effect with BOSS DR11 and the Atacama Cosmology Telescope

We present a new measurement of the kinematic Sunyaev-Zeldovich effect using data from the Atacama Cosmology Telescope (ACT) and the Baryon Oscillation Spectroscopic Survey (BOSS). Using 600 square degrees of overlapping sky area, we evaluate the mean pairwise baryon momentum associated with the positions of 50,000 bright galaxies in the BOSS DR11 Large Scale Structure catalog. A non-zero signal arises from the large-scale motions of halos containing the sample galaxies. The data fits an analytical signal model well, with the optical depth to microwave photon scattering as a free parameter determining the overall signal amplitude. We estimate the covariance matrix of the mean pairwise momentum as a function of galaxy separation, using microwave sky simulations, jackknife evaluation, and bootstrap estimates. The most conservative simulation-based errors give signal-to-noise estimates between 3.6 and 4.1 for varying galaxy luminosity cuts. We discuss how the other error determinations can lead to higher signal-to-noise values, and consider the impact of several possible systematic errors. Estimates of the optical depth from the average thermal Sunyaev-Zeldovich signal at the sample galaxy positions are broadly consistent with those obtained from the mean pairwise momentum signal.Comment: 15 pages, 8 figures, 2 table