Day 847

Monday.

1503.01785
A Hubble astrometry initiative: laying the foundation for the next-generation proper-motion survey of the Local Group
Kallivayalil, Wetzel, Simon, Boylan-Kolchin, Deason, Fritz, Geha, Sohn, Weisz

High-precision astrometry throughout the LG is a unique capability of HST, with potential for transformative science, including constraining the nature of dark matter, probing the epoch of reionization, and understanding key physics of galaxy evolution.  While Gaia will provide unparalleled astrometric precision for bright stars in they nor halo of the MW, HST is the only current mission capable of measuring accurate proper motions for systems at greater distances (>80 kpc), which represents the vast majority of galaxies in the LG.  The next generation of proper-motion measurements will require long time baselines, spanning many years to decades and possibly multiple telescopes, combining HST with JWST or WFIRST.  However, the current HST allocation process is not conductive to such multi-cycle/multi-mission science, which will bear fruit primarily over many years.  Propose an HST astrometry initiative to enable long-time-baseline, multi-mission science, which could be used to prove comprehensive kinematic measurements of all dwarf galaxies and high surface-density stellar streams in the LG with HST's ACS or WFC3.  Such an initiative not only would produce forefront scientific results within the next 5 years of HSTs life, but also would serve as a critical anchor point for future missions to obtain unprecedented astrometric accuracy, ensuring that HST leaves a unique and lasting legacy for decades to come.


1503.01851
Cosmological constraints from Subaru weak lensing cluster counts
Hamana, Sakurai, Koike, Miller
Present results of WL cluster counts from 11 sq deg SuprimeCam data.  Although the area is much smaller than previous work, the number density of galaxies usable for WL analysis is about 2x as large as those.  The higher galaxy number density reduces the noise in the WL mass maps, and thus increases the S/N of peaks of the lensing signal due to massive clusters.  This enables us to construct a WL selected cluster sample by adopting a high threshold S/N, such that the contamination rate due to false signals is small.  Find 6 peaks with S/N>5.  For all the peaks, previously identified clusters of galaxies are matched within a separation of 1 arcmin, demonstrating good correspondence between the peaks and clusters of galaxies.  Evaluate the statitiscal error using mock WL data, and find Npeak=6±3.1 in an effective area of 9.0 sq deg.  Compare the measured WL cluster counts with the theoretical model prediction based on halo models and place the constraint on Omega_m-sigma_8 plane which is found to be consistent with currently standard LCDM models.  It is demonstrated that the WL cluster counts can place a unique constraint on sigma_8-c_0 plane, where c_0 is the normalization of the DM halo mass-concentration relationship.  Finally, discuss prospects for ongoing/future wide field optical galaxy surveys.