Event Calendar

Title: Approximating Probabilistic Photometric Redshifts for Large Surveys

Abstract: Upcoming and ongoing galaxy surveys will produce redshift probability distribution functions (PDFs) in addition to traditional photometric redshift (photo-z) point estimates. However, the storage of photo-z PDFs may present a challenge with increasingly large catalogs, as we face a trade-off between the accuracy of subsequent science measurements and the storage cost. This paper presents qp, a Python package facilitating manipulation of approximations of 1-dimensional PDFs, as suitable for photo-z PDF s. We use qp to investigate the performance of three simple PDF storage formats on two realistic mock datasets, representative of upcoming surveys with different data qualities, as a function of the number of stored parameters per photo-z PDF, using metrics of both individual photo-z PDF s and an estimator of the overall redshift distribution function.This will have huge reach for surveys like the Large Synoptic Survey Telescope (LSST).

Title: Forming planetesimals from gravitational collapse

Abstract: The formation of 1-100 km planetesimals from dust and pebbles is a critical and possibly determinative step in establishing the architecture of extrasolar planetary systems. One physically viable pathway involves the spontaneous clustering of small solid particles through the streaming instability, followed by gravitational collapse. I will discuss the results of new simulations of planetesimal formation, that confirm some prior results and provide evidence that the mass function of planetesimals formed in laminar disks is independent of the aerodynamic properties of the particles that participate in the instability. I will highlight open questions and connections to a global scenario of planet formation in which mobility plays the central role.

Host: Mohamad Ali-Dib

Title: The halos of galaxies and clusters

Abstract: I will show recent measurements of halo shapes, profiles and edges from SDSS and DES. These measurements can be used for tests of modified gravity and dark matter interactions. I will describe tests with current measurements and future possibilities to test new ideas.

Host: Xin Wang

Title: TBD

Abstract: TBD

Host: Joel Meyers