1509.02158
Constraints on the temperature of the intergalactic medium at z=04 with 21-cm observations
Greig, Mesinger, Pober
Compute robust lower limits on the spin temperature, Ts, f the z=8.4 IGM, implied by the upper limits on the 21-cm power spectrum recently measured by PAPER-64. Unlike previous studies which used a single EoR model, the approach samples a large parameter space of EoR models: the dominant uncertainty when estimating constraints on Ts. Allowing Ts to be a free parameter and marginalizing over EoR parameters in the MCMC code 21CMMC, infer Ts>3K for a mean IGM neutral fraction of x_HI>~0.1. Further improve on these limits by folding-in additional EoR constraints based on: (i) the dark fraction in QSO spectra, which implies a strict upper limit of x_HI{z=5.9]<0.06+0.05(1sigma); and (ii) the electron scattering optical depth, tau_e=0.066±0.016(1sigma) measured by the Planck satellite. By restricting the allowed EoR models, these additional observations tighten the lower limits on the spin temperature to Ts>=6K. Thus, even such preliminary 21-cm observations begin to rule out extreme scenarios such as 'cold reionization', implying at least some prior heating of the IGM. The analysis framework developed here can be applied to upcoming 21-cm observations, thereby providing unique insights into the sources which heated and subsequently reionized the very early Universe.
1509.02159
Galaxy and Mass Assembly (GAMA): projected galaxy clustering
Farrow, Cole, Norberg, Metcalfe, et al
Measure the projected 2PCF of galaxies in the 180 deg2 equatorial regions of the GAMA II survey, for four different redshift slices between z=0.0 and z=0.5. To do this, further develop the Cole (2011) method of producing suitable random catalogs for the calculation of correlation functions. Find that more r-band luminous, more massive and redder galaxies are more clustered. Also find that red galaxies have stronger clustering on scales less than ~3 Mpc/h. Compare to two different versions of the GALFORM galaxy formation model, Lacey et al (in prep) and Gonzalez-Perez et al (2014), and find that the models reproduce the trend of stronger clustering for more massive galaxies. However, the models under predict the clustering of blue galaxies, can incorrectly predict the correlation function on small scales and under predict the clustering in the sample of galaxies with ~3 L_r. Suggest possible avenues to explore to improve these clustering predictions. The measurements presented in this paper can be used to test other galaxy formation models, and make the measurements available online to facilitate this.
1509.02162
Cosmology and astrophysics from relaxed galaxy clusters- IV: robustly calibrating hydrostatic masses with weak lensing
Applegate, Mantz, Allen, vonder Linden, et al
The 4th in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Use measurements of WL from Weighting the Ginats project to calibrate Chandra X-ray measurements of total mass that rely on the assumption of hydrostatic equilibrium. This comparison of X-ray and lensing masses provides a measurement of the combined bias of X-ray hydrostatic masses due to both astrophysical and instrumental sources. Assuming a fixed cosmology, and within a characteristic radius (r_2500) determined from the X-ray data, measure a lensing to X-ray mass ratio of 0.96±9%(stat)±9%(sys). Find no significant trends of the ratio with mass, redshift or the morphological indicators used to select the sample. In accordance with predictions from hydro sims for the most massive, relaxed clusters, the results disfavor strong, tens-of-percent departures from hydrostatic equilibrium at these radii. In addition, find a mean concentration of the sample measured from lensing data of c_200=3.0+4.4-1.8. Anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30-50%, leading to similar improvements in cosmo constraints that employ X-ray hydrostatic mass estimates, such as on Omega-m from the cluster gas mass fraction.
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