Measuring H0 from the 6dF Galaxy Survey and future low-redshift surveys

Baryon acoustic oscillations (BAO) at low redshift provide a precise and largely model-independent way to measure the Hubble constant, H0. The 6dF Galaxy Survey measurement of the BAO scale gives a value of H0 = 67 +/- 3.2 km/s/Mpc, achieving a 1-sigma precision of 5%. With improved analysis techniques, the planned WALLABY (HI) and TAIPAN (optical) redshift surveys are predicted to measure H0 to 1-3% precision.Comment: Proceedings of IAU Symposium 289, "Advancing the Physics of Cosmic Distances", Richard de Grijs & Giuseppe Bono (eds), 2012, 4p

The Collateral Channel under Imperfect Debt Enforcement

Does a country’s ability to enforce debt contracts affect the sensitivity of economic activity to collateral values? To answer this question, we introduce a novel industry-specific measure of real asset redeployability - the ease with which real assets are transfered to alternative uses - as a proxy for collateral liquidation values. Our measure exploits the heterogeneity of expenditures in new and used capital and the heterogeneity in the composition of real asset holdings across U.S. industries. Using a cross-industry cross-country approach, we find that industry size and growth are more sensitive to collateral values in countries with weaker debt enforcement. Our estimates indicate that the differential effect is sizeable. The sensitivity of economic activity to collateral values is not affected by a country’s financial development once the quality of debt enforcement is accounted for. We then rationalize our empirical findings based on a model of credit under imperfect enforcement and discuss an important implication of our empirical result: macroeconomic volatility generated by fluctuations in collateral values is higher in countries with weaker debt enforcement institutions.

Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

We analyse the power spectrum of the Baryon Oscillation Spectroscopic Survey (BOSS), Data Release 12 (DR12) to constrain the relative velocity effect, which represents a potential systematic for measurements of the Baryon Acoustic Oscillation (BAO) scale. The relative velocity effect is sourced by the different evolution of baryon and cold dark matter perturbations before decoupling. Our power spectrum model includes all $1$-loop redshift-space terms corresponding to $v_{\rm bc}$ parameterised by the bias parameter $b_{v^2}$. We also include the linear terms proportional to the relative density, $\delta_{\rm bc}$, and relative velocity dispersion, $\theta_{\rm bc}$, which we parameterise with the bias parameters $b^{\rm bc}_{\delta}$ and $b^{\rm bc}_{\theta}$. Our data does not support a detection of the relative velocity effect in any of these parameters. Combining the low and high redshift bins of BOSS, we find limits of $b_{v^2} = 0.012 \pm 0.015\;(\pm 0.031)$, $b^{\rm bc}_{\delta} = -1.0 \pm 2.5\;(\pm 6.2)$ and $b^{\rm bc}_{\theta} = -114 \pm 55\;(\pm 175)$ with $68\%$ ($95\%$) confidence levels. These constraints restrict the potential systematic shift in $D_A(z)$, $H(z)$ and $f\sigma_8$, due to the relative velocity, to $1\%$, $0.8\%$ and $2\%$, respectively. Given the current uncertainties on the BAO measurements of BOSS these shifts correspond to $0.53\sigma$, $0.5\sigma$ and $0.22\sigma$ for $D_A(z)$, $H(z)$ and $f\sigma_8$, respectively

Enzyme Replacement in Gaucher Disease

The development of enzyme replacement therapy for Gaucher disease was a triumph of translational medicine. What were the key steps in its development? What are the controversies surrounding its use

Extending the modeling of the anisotropic galaxy power spectrum to k=0.4 hMpc−1k = 0.4 \ h\mathrm{Mpc}^{-1}

We present a new model for the redshift-space power spectrum of galaxies and demonstrate its accuracy in modeling the monopole, quadrupole, and hexadecapole of the galaxy density field down to scales of $k = 0.4 \ h\mathrm{Mpc}^{-1}$. The model describes the clustering of galaxies in the context of a halo model and the clustering of the underlying halos in redshift space using a combination of Eulerian perturbation theory and $N$-body simulations. The modeling of redshift-space distortions is done using the so-called distribution function approach. The final model has 13 free parameters, and each parameter is physically motivated rather than a nuisance parameter, which allows the use of well-motivated priors. We account for the Finger-of-God effect from centrals and both isolated and non-isolated satellites rather than using a single velocity dispersion to describe the combined effect. We test and validate the accuracy of the model on several sets of high-fidelity $N$-body simulations, as well as realistic mock catalogs designed to simulate the BOSS DR12 CMASS data set. The suite of simulations covers a range of cosmologies and galaxy bias models, providing a rigorous test of the level of theoretical systematics present in the model. The level of bias in the recovered values of $f \sigma_8$ is found to be small. When including scales to $k = 0.4 \ h\mathrm{Mpc}^{-1}$, we find 15-30\% gains in the statistical precision of $f \sigma_8$ relative to $k = 0.2 \ h\mathrm{Mpc}^{-1}$ and a roughly 10-15\% improvement for the perpendicular Alcock-Paczynski parameter $\alpha_\perp$. Using the BOSS DR12 CMASS mocks as a benchmark for comparison, we estimate an uncertainty on $f \sigma_8$ that is $\sim$10-20\% larger than other similar Fourier-space RSD models in the literature that use $k \leq 0.2 \ h\mathrm{Mpc}^{-1}$, suggesting that these models likely have a too-limited parametrization.Comment: Submitted to JCA