Day 1490

Thursday.

1810.09466
The circular velocity curve of the Milky Way from 5 to 25 kpc
Eilers, Hogg, Rix, Ness

Measure the circular velocity curve v_c(R) for the MW with the highest precision to date across Galactocentric distances of 5<=R<=25 kpc.  The analysis draws on the 6-dimensional phase-space coordinates of >~23k luminous red-giant stars, for which the previously determined precise parallaxes using a data-driven model that combines spectral data from APOGEE with photometric information from WISE, 2MASS, and Gaia. Derive the circular velocity curve with the Jeans equation assuming an axisymmetric gravitational potential.  At the location of the Sun, determine the circular velocity with its formal uncertainty to be v_c(Rsun) = 229.0±0.2 km/s with systematic uncertainties at the ~5% level.  Find that the velocity curve is gently but significantly declining at -1.7±0.1 km/s/kpc, with a systematic uncertainty of 0.46 km/s/kpc, beyond the inner 5 kpc.  Exclude the inner 5 kpc from the analysis due to the presence of the Galactic bar, which strongly influences the kinematic structure and requires modeling in a non-axisymmetric potential. Combining the results with external measurement of the mass distribution for the baryonic components of the MW from other studies, estimate the Galaxy's dark halo mass within the viral radius to be M_vir=7.25±0.26e11 Msun and a local dark matter density of rho_dm(Sun) = 0.30±0.03 GeV/cm^3.


1810.09456
Dark Energy Survey Year 1 Results: methods for cluster cosmology and application to the SDSS
Constant, et al

Perform the first blind analysis of cluster abundance data.  Specifically, derive cosmo constraints from the abundance and WL signal of red mapper clusters of richness lambda >= 20 in the range 0.1<z<0.3 as measured in SDSS.  Simultaneously fit for cosmological parametersand the richness--mass relation of the clusters.  For a flat LCDM cosmo model with massive neutrinos, find S_8 == sigma8(Omega_m/0.3)^0.5 = 0.79+0.05-0.04.  This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths.  The result is also consistent with the combined probes analyses by DES and KiDS, and with CMB anisotropies as measured by Planck.  Demonstrate that the cosmological posteriors are robust against variation of the richness-mass relation model and to systematics associated with the calibration of the selection function.  In combination with BAO and BBN data, constrain the Hubble rate to be h=0.66±0.02, independent of the CMB.  Further work aimed at improving the understanding of the scatter of the richness-mass relation has the potential to significantly improve the precision of the cosmo posteriors.  The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES.  The SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set.