Day 1340

Monday.

1711.06267
There is no missing satellites problem
Kim, Peter, Hargis

A critical challenge to the CDM paradigm is that there are fewer satellites observed around the MW than found in simulations of DM substructure.  Show that there is a match between the observed satellite counts corrected by the detection efficiency of the SDSS (for luminosities L<~340 L_sun) and the number of luminous satellites predicted by CDM, assuming an empirical relation between stellar mass and halo mass.  The "missing satellites problem", cast in terms of number counts is thus solved, and imply that luminous satellites inhabit sub halos as smalls 1e7-8 Msun.  The total number of MW satellites depends sensitively on the spatial distribution of satellites.  Also show that WDM models with a thermal relic mass smaller than 4 keV are robustly ruled out, and that limits of m_WDM <~ 8keV from the MW are probable in the near future.  Similarly stringent constraints can be placed on any DM model that leads to a suppression of the matter power spectrum on ~1e7 Msun scales.  Measurements of completely dark halos below 1e8 Msun, achievable with substructure lensing, are the next frontier for tests of CDM.


1711.06273
Exploring the brighter fatter effect with the hyper suprime-cam
Coulton, Armstrong, Smith, Lupton, Spergel

The brighter fatter effect has been postulated to arise due to the build up of a transverse electric field, produced as photo-charges accumulate in the pixels' potential wells.  Investigate the brighter fatter effect in HSC by examine flat fields and moments of stars.  Observe deviations from the expected linear relation in the photon transfer curve, luminosity dependent correlations between pixels in flat field images and a luminosity dependent PSF in stellar observations.  Under the key assumptions of translation invariance and Maxwell's equations in thequasi-static limit, give a first-principles proof that the effect can be parameterized by a translationally invariant scalar kernel.  Describe how this kernel can be estimated from flat fields and discuss how this kernel has been used to remove the brighter fatter distortions in HSC images.  Find that the correction restores the expected linear relation in the photon transfer curves and significantly reduces, but does not completely remove, the luminosity dependence of the PSF over a wide range of magnitudes.