News, 2017
On MLK Day King College Prep Cosmology Club Explores Dark Matter
January 16, 2017
On MLK Day King College Prep Cosmology Club Explores Dark Matter
On Martin Luther King Day, 2017, students from the Cosmology Club at Dr. Martin Luther King Prep High School will visit KICP to learn about current dark matter research and tour the lab facilities. The instructor of the club, Nora Wengerski, has been working with KICP Professor Luca Grandi and his group for several months, including a week-long research experience in the summer of 2016 and developing the curriculum for the King Prep cosmology club, which is in its inaugural year.

Former PFC Fellow Eric Dahl honored with a PECASE
January 24, 2017
Former KICP Fellow Eric Dahl
Former KICP Fellow Eric Dahl has received a Presidential Early Career Award for Scientists and Engineers (PECASE); the highest honor presented by the U.S. Government to scientists and engineers during the early stages of their careers. Dahl's research at the KICP focused on the COUPP/PICO series of bubble chamber based dark matter detection experiments. His current research continues to focus upon PICO, where he is developing new and innovating ways to use this technology to detect dark matter.

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Summer Undergraduate Researcher Michael Foley Wins AAS Chambliss Student Medal
February 1, 2017
Undergraduate Michael Foley (Far Left) received an AAS Chambliss Student Medal for work conducted with KICP Fellow Dan Scolnic (Second from Right).
KICP Summer undergraduate research student Michael Foley was recently awarded a Chambliss Student Medal at the 229th AAS meeting for a presentation on his KICP research. Michael, a Notre Dame student, worked at the KICP on a grant from Notre Dame's Glynn Family Honors Program and was mentored by KICP Fellow Dan Scolnic and Senior Researcher Rick Kessler. Michael's poster presented his work on The Foundation Survey, a new low-redshift supernova survey that uses the Pan-STARRS telescope to measure distances of Type Ia Supernovae in the Hubble flow. The survey will be a critical resource in the coming years to improve measurements of the Hubble constant and satisfy the WFIRST low-redshift sample requirement for measurements of dark energy. According to mentor Scolnic, "Michael helped rewrite the full photometry pipeline, determined our absolute calibration, created accurate simulations of the survey and became completely indispensable in just one summer."

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Deflategate: Cold Wet Footballs, Ideal Gas Laws and Accusations of Cheating
February 8, 2017
Deflategate: Cold Wet Footballs, Ideal Gas Laws and Accusations of Cheating
Just in time for Super Bowl LI, students in the Space Explorers Program examined the physics and media frenzy of Deflategate. During the 2015 AFC championship game, NFL officials discovered that the pressure in several footballs used by the New England Patriots had decreased below permissible levels. This sparked a national controversy known as "Deflategate". The NFL (as well as many enemies the four-time Super Bowl champions Patriots had made in the football world) argued that the pressure drop could only be caused by cheating, especially because Tom Brady favors underinflated balls. (note: each team controls 12 footballs used when they are on offense mandated to be between 12.5 and 13.5 psi ). Patriots' fans argued that the drop was caused either by well known laws of physics, or by an elaborate NFL conspiracy.

Twenty-eight (28) high school students in KICP's Space Explorers program put these arguments to the test. Over the course of two weeks, students critically evaluated over a dozen arguments made by both sides, ranging from court documents, to college lectures, to tweets. Despite the strong opinions, contradictory claims, and often factually incorrect information found in these arguments, the Space Explorers managed to identify the critical questions that needed to be resolved to determine if Deflategate could be caused by purely innocuous physics and designed an experiment to address them. Their experiment revolved around measuring the effect that wetness had on the rate at which cold footballs warm up and increase in pressure.

To date their results are inconclusive. One trial found nothing suspicious about the pressure drop, and a second could not explain the low pressures in the Patriots' footballs. The Space Explorers themselves are split down the middle about how to interpret their results and will debate the best way to resolve this difference at the pre-Super Bowl Saturday class.

Hsin-Yu Chen has been selected for a Cronin Fellowship
February 15, 2017
Hsin-Yu Chen has been selected for a Cronin Fellowship
Please join me in congratulating Hsin-Yu Chen who has been selected for a Cronin Fellowship for 2017. The James Cronin Graduate Student Fellowship honors Professor Cronin though support of exceptional Ph.D. candidates. The Cronin Fellowship will support Hsin-Yu's research work up to the end of Summer quarter 2017, when she is expected to graduate.

Congratulations Hsin-Yu!

Angela V. Olinto,
Homer J. Livingston Professor and Chair Department of Astronomy & Astrophysics

The PFC will welcome 5 new Fellows in the Autumn of 2017
March 9, 2017
The PFC will welcome 5 new Fellows in the Autumn of 2017
Reed Essick received his PhD from MIT focusing on strong tides in close binary systems and gravitational radiation. His work has touched many areas of gravitational-wave astrophysics, from data quality and detection to phenomenological source modeling. Reed plans to continue this research at KICP and looks forward to exploring the physics accessible through measurements of populations gravitational wave sources.

Macarena Lagos will receive her PhD from Imperial College London. Her research focuses on theoretical cosmology, specifically on analysing the viability of alternative gravity theories and developing methods to test gravity at large scales. At KICP, Macarena hopes to continue her current research and start new collaborations with its members.

Kirit Karkare will join us as a joint Grainger and KICP Fellow after completing his degree at Harvard University, where he worked on hardware and systematics analysis for the BICEP/Keck CMB polarization experiments. At the KICP, he plans to continue working on the CMB with BICEP and SPT, and on detector development for line intensity mapping and measurements of high-redshift galaxies.

Wai Ling (Kimmy) Wu did her graduate work at Stanford University with the BICEP/Keck team on the design, testing, and deployment of BICEP3 -- a small aperture CMB polarimeter that aims to target the inflationary gravitational wave B-mode signature. She then moved to UC Berkeley to work with the SPT team on the SPT-3G receiver and on delensing CMB B-mode maps, an important step to further constraint the inflationary B-mode signature. At KICP, she plans on extending her delensing work with BICEP/Keck and SPT datasets and looks forward to exploring new avenues to understand the cosmos with fellow KICP researchers.

Grayson Rich carried out research at Triangle Universities Nuclear Laboratory (TUNL) while a graduate student at the University of North Carolina. As a part of the COHERENT Collaboration, he has been working towards the first observation of coherent, elastic neutrino-nucleus scattering (CEvNS): a low-energy neutrino-nucleus interaction arising from the standard model but still undetected over 40 years after its prediction. As a KICP Fellow and an Enrico Fermi Fellow at the Enrico Fermi Institute, he will maintain involvement with COHERENT and continue to advance an effort he spearheaded at TUNL to provide definitive characterizations of the responses of neutrino and dark matter detector systems, working with several groups at KICP and the broader astroparticle physics community. He also hopes to work with KICP and EFI members to exploit high-energy astrophysical signals, seeking insight into cosmological questions and the properties of fundamental particles.

The Event Horizon Telescope's historic quest
April 13, 2017
The South Pole Telescope
This week the South Pole Telescope joined a global network of telescopes to take observations which aim to capture the highest-resolution image ever taken of the supermassive black hole at the center of the Milky Way.

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The Halo Boundary of Galaxy Clusters in SDSS
April 24, 2017
A cluster formed in a Lambda-Cold Dark Matter simulation of structure formation.

Credit: Benedikt Diemer, Philip Mansfield
KICP astrophysicists Chihway Chang and Andrey Kravtsov have participated in a recent study, which presents strong evidence for the physical edge of galaxy clusters using public data from the Sloan Digital Sky Survey.

The existence of such physical edges associated with sharp density drops due to the density caustics formed by accreting matter was predicted by KICP researchers Benedikt Diemer and Andrey Kravtsov in 2014, as part of Diemers PhD research. In a follow-up study, Diemer, Kravtsov and a former KICP fellow Surhud More (currently at Institute of Physics of the Universe, Tokyo, Japan) have shown that the-edges can be considered to be natural physical boundary of dark matter halos that provide the gravitational "back-bone" for the structures observed in the galaxy distribution.

In the recent study, co-led by Chihway Chang and Eric Baxter - a former KICP student and currently a postdoctoral fellow at the University of Pennsylvania - the density drop associated with the halo edges was detected in the galaxy distribution around cluster centers.

Cosmological simulations show that massive galaxy clusters we see today have been accreting galaxies into their deep gravitational potential over the cosmic time. The process of galaxies "falling into" the cluster's potential well is a fairly clean and universal process that depends only on basic quantities of the cluster such as mass and accretion rate. One of the result of this simple picture is a sharp feature in the number density of galaxies around clusters - an imprint of the caustic formed by the infalling galaxies as they reach the first apocenter of their orbit, or the "edge" of the galaxy cluster. Researchers called the distance of the edge the "splashback" radius, as galaxies literally "splashing back" to that radius after they accrete onto cluster.

Together with collaborators in UPenn and UIUC, that included KICP faculty Andrey Kravtsov, Chihway Chang and Eric Baxter, examined distribution of galaxies around a sample of clusters identified within the SDSS. The existence of the edge in the galaxy distribution within clusters was confirmed. In addition, the analysis revealed that properties of galaxies around cluster are sensitive to existence of the edge. Outside the splashback radius, the mix of red and blue galaxies was approximately independent of the distance from the cluster center, while inside the splashback radius the mix is abruptly changes towards a larger fraction of red galaxies. This indicates that the edge is a real dynamical feature and that majority of galaxies get transformed by the cluster environment from blue to red in less than one orbital period.

This figure shows the fraction of red and blue galaxies around galaxy clusters. The sharp change in the red fraction indicates that galaxy tend to turn red once they enter the edge of the cluster, which is marked by the grey vertical band. (Figure modified from the paper "The Halo Boundary of Galaxy Clusters in the SDSS".)

Related KICP references:

Congratulations to PFC member Joshua Frieman!
April 27, 2017
Prof. Josh Frieman
Congratulations to KICP Senior Member Joshua Frieman for his election as Vice Chair of the Executive Committee of the Division of Astrophysics of the American Physical Society.

The Division of Astrophysics (DAP), organized in 1970, engages in observational and theoretical investigation that relates to the study of physical processes in stars and other discrete galactic sources, galactic structure and evolution, the early history and evolution of the Universe, and the Sun and solar activity. Division interests also have significant overlap with other APS divisions such as Particles and Fields, Nuclear Physics, and Plasma Physics.