CCAPP Summer Seminar

June 20, 2017

11:30 am - 12:30 pm

4054 McPherson Laboratory

Add to Calendar 2017-06-20 11:30:00 2017-06-20 12:30:00 CCAPP Summer Seminar Title: Producing an SDSS-BOSS CMASS sample with imaging from the Dark Energy Survey to test gravitySpeaker: Su-Jeong LeeWe propose a test of gravity on cosmological scales using the newly-defined DES CMASS analogue (DMASS) sample. The CMASS sample is originally designed from the Sloan Digital Sky Survey and provides the most powerful redshift-space galaxy clustering measurements to date. A joint analysis of redshift-space distortions (such as those probed by CMASS) and weak gravitational lensing (currently best measured by the Dark Energy Survey) can provide a powerful cosmological-scale test of General Relativity. Unfortunately, the DES and SDSS-BOSS footprints suffer minimal overlap, primarily on the celestial equator near the SDSS Stripe 82 region. We have built a robust Bayesian model to select DMASS galaxies in the DES footprint specifically to address this lack of overlap. We show that the DMASS sample selected by this model has a fairly good match with the CMASS sample through various validations. To test models of modified gravity, we construct a data vector consisting of Year 1 DES galaxy-galaxy lensing measurements around the galaxies in the DMASS sample and the existing SDSS redshift-space distortion measurements from BOSS.Title: Quadruple Systems: Hints on Supernova FormationSpeaker: Xiao FangThe origin of Type Ia Supernovae (SNe) is still not well understood. One of the most popular candidates is the binary white dwarf (WD) merger. However, it has long been realized that binary WD systems normally take extremely long time to merge via gravitational waves and it is still unclear whether WD mergers can fully account for the observed SN Ia rate. Recent effort has been devoted to the effects of introducing a distant tertiary to the binary system, which can induce high eccentricities of the binary WDs and possibly lead to direct collisions or more efficient energy dissipation. Alternatively, we investigate the long-term evolution of the hierarchical quadruple systems, i.e. WD binary with a binary companion, which are basically unexplored, yet they should be numerous. We explore their interesting dynamics and find that the fraction of reaching high eccentricities is largely enhanced, which hints on a higher WD merger rate than predicted from triple systems with the same set of secular and non-secular effects considered. Considering the population of quadruple stellar systems, the quadruple scenario might contribute significantly to the overall rate of Ia SNe. 4054 McPherson Laboratory OSU ASC Drupal 8 ascwebservices@osu.edu America/New_York public

2017-06-20 11:30:00 2017-06-20 12:30:00 CCAPP Summer Seminar Title: Producing an SDSS-BOSS CMASS sample with imaging from the Dark Energy Survey to test gravitySpeaker: Su-Jeong LeeWe propose a test of gravity on cosmological scales using the newly-defined DES CMASS analogue (DMASS) sample. The CMASS sample is originally designed from the Sloan Digital Sky Survey and provides the most powerful redshift-space galaxy clustering measurements to date.  A joint analysis of redshift-space distortions (such as those probed by CMASS) and weak gravitational lensing (currently best measured by the Dark Energy Survey) can provide a powerful cosmological-scale test of General Relativity. Unfortunately, the DES and SDSS-BOSS footprints suffer minimal overlap, primarily on the celestial equator near the SDSS Stripe 82 region.  We have built a robust Bayesian model to select DMASS galaxies in the DES footprint specifically to address this lack of overlap. We show that the DMASS sample selected by this model has a fairly good match with the CMASS sample through various validations. To test models of modified gravity, we construct a data vector consisting of Year 1 DES galaxy-galaxy lensing measurements around the galaxies in the DMASS sample and the existing SDSS redshift-space distortion measurements from BOSS.Title: Quadruple Systems: Hints on Supernova FormationSpeaker: Xiao FangThe origin of Type Ia Supernovae (SNe) is still not well understood. One of the most popular candidates is the binary white dwarf (WD) merger. However, it has long been realized that binary WD systems normally take extremely long time to merge via gravitational waves and it is still unclear whether WD mergers can fully account for the observed SN Ia rate. Recent effort has been devoted to the effects of introducing a distant tertiary to the binary system, which can induce high eccentricities of the binary WDs and possibly lead to direct collisions or more efficient energy dissipation. Alternatively, we investigate the long-term evolution of the hierarchical quadruple systems, i.e. WD binary with a binary companion, which are basically unexplored, yet they should be numerous. We explore their interesting dynamics and find that the fraction of reaching high eccentricities is largely enhanced, which hints on a higher WD merger rate than predicted from triple systems with the same set of secular and non-secular effects considered. Considering the population of quadruple stellar systems, the quadruple scenario might contribute significantly to the overall rate of Ia SNe. 4054 McPherson Laboratory America/New_York public

Title: Producing an SDSS-BOSS CMASS sample with imaging from the Dark Energy Survey to test gravity

Speaker: Su-Jeong Lee

We propose a test of gravity on cosmological scales using the newly-defined DES CMASS analogue (DMASS) sample. The CMASS sample is originally designed from the Sloan Digital Sky Survey and provides the most powerful redshift-space galaxy clustering measurements to date. A joint analysis of redshift-space distortions (such as those probed by CMASS) and weak gravitational lensing (currently best measured by the Dark Energy Survey) can provide a powerful cosmological-scale test of General Relativity. Unfortunately, the DES and SDSS-BOSS footprints suffer minimal overlap, primarily on the celestial equator near the SDSS Stripe 82 region. We have built a robust Bayesian model to select DMASS galaxies in the DES footprint specifically to address this lack of overlap. We show that the DMASS sample selected by this model has a fairly good match with the CMASS sample through various validations. To test models of modified gravity, we construct a data vector consisting of Year 1 DES galaxy-galaxy lensing measurements around the galaxies in the DMASS sample and the existing SDSS redshift-space distortion measurements from BOSS.

Title: Quadruple Systems: Hints on Supernova Formation

Speaker: Xiao Fang

The origin of Type Ia Supernovae (SNe) is still not well understood. One of the most popular candidates is the binary white dwarf (WD) merger. However, it has long been realized that binary WD systems normally take extremely long time to merge via gravitational waves and it is still unclear whether WD mergers can fully account for the observed SN Ia rate. Recent effort has been devoted to the effects of introducing a distant tertiary to the binary system, which can induce high eccentricities of the binary WDs and possibly lead to direct collisions or more efficient energy dissipation. Alternatively, we investigate the long-term evolution of the hierarchical quadruple systems, i.e. WD binary with a binary companion, which are basically unexplored, yet they should be numerous. We explore their interesting dynamics and find that the fraction of reaching high eccentricities is largely enhanced, which hints on a higher WD merger rate than predicted from triple systems with the same set of secular and non-secular effects considered. Considering the population of quadruple stellar systems, the quadruple scenario might contribute significantly to the overall rate of Ia SNe.