John R. Peterson
Assoc. Professor of Physics
Purdue University
Teaching:
S2007,
S2008, & S2009: Physics 360, Quantum
Mechanics
F2007,
F2008, F2009, S2013, S2014, & S2015:
Physics 172, Modern Mechanics
S2010,
S2011, S2012, S2022, S2023: Physics
& Astronomy 562, High Energy Astrophysics
F2010,
F2011, & F2012: Physics &
Astronomy 561, Galaxies & Large Scale Structure
F2013,
F2014, F2015, F2016, F2020, F2021, F2022, F2023: Astronomy 370, Cosmology
S2016
& S2017: Physics & Astronomy
563, Particle Astrophysics
F2017,
F2018, F2019: Physics & Astronomy
567: Observational Techniques in
Astronomy
S2019,
S2020, S2021: Physics & Astronomy
560: Stellar Evolution
Research:
Research Fields: X-ray
& Optical Astrophysics, Particle Astrophysics, & Cosmology
Research Subjects: Clusters
of Galaxies, Galaxies, Dark Energy, & Dark Matter
My
group focuses on research in astrophysics and cosmology using data from X-ray
and optical telescopes. Some work we have
done on the X-ray spectra of clusters of galaxies (above left) demonstrates a
discrepancy in a model how the gas in clusters of galaxies cools. The X-ray spectrum contains a number of
atomic emission lines, which act as a thermostat for gas of specific temperatures. The light blue model is the standard model
for complete cooling, but is clearly inconsistent with the observed data (dark
blue). Instead a model where the colder plasma
is missing (red) matches the data well.
The interpretation of this is still unclear, since it would seem to
indicate an enormous heating source inside the largest structures in the
Universe.
By
simply counting the number of clusters of galaxies in the Universe and
measuring where they are, we have an extremely sensitive indicator of how much
dark matter and dark energy there is in the Universe. The above right image shows a collection of
new clusters of galaxies we have found by using the most sensitive X-ray
telescopes. The number and location of
the clusters of galaxies in the Universe follows a theory for how fast matter
can form structures as the Universe begins to expand. Thus, this can be used to measure properties
of dark matter and dark energy.
Galaxies
can be studied in optical images (below) to map the distribution of matter in
the Universe. In addition, gravitational
forces that alter the path of light before it reaches us can distort the shapes
of distant galaxies. This is a
relatively new technique that can map the dark matter in the Universe. Furthermore, the recessional velocity of the
galaxies can be estimated by using the galaxy colors. This enables us to map out this dark matter
map crudely in cosmic time, since faster moving galaxies are correlated with
larger cosmic distances. It is thought
that the evolution of the dark matter map is sensitive to the properties of
dark energy. Thus, detailed measurements
of galaxies can help us to unravel the mystery of both dark matter and dark
energy.
These
dark matter & dark energy measurements, however, are relatively subtle and
require careful study of measurement systematics. Because of that we created a Photon Simulator
that uses ab initio physics calculations to simulate light through the atmosphere
and then through a telescope and camera system. All possible distortions of the images of
galaxy light through atmosphere+telescope+camera
system can then be studied in detailed.
Much more detail about these simulations including movies of aspects of
the simulator can be found at the PhoSim website.
Current Group Members:
Post Doctoral Researchers and
Research Associates:
Glenn Sembroski (Research
Associate 2015-)
Graduate
Students:
Anirban Dutta (Graduate Student 2018-)
Undergraduate Students:
Past Group Members:
Caleb Remocaldo
(2018-2020, Purdue undergraduate)
Colin
Burke (2015-2018, Purdue undergraduate, now a graduate student in astronomy at
U Illinois)
Kira
Graves (2017-2018, Purdue undergraduate)
Mackenzie
Geckler (2018, Purdue undergraduate)
En-Hsin Peng
(2011-2015 Postdoc; Research Associate 2015-2017)
Jun Cheng (2015-2017, Purdue graduate
student, PhD 2017)
Matt
Wiesner (2015-2016 Postdoc; Assistant Professor at Benedictine University)
Mingbin Leng (2013-2014, Purdue undergraduate; now a graduate
student in physics at Brown Univ.)
Amanda Winans (2012, REU student from
Missouri State)
Mary Ann Hodge (2011, REU student from
Murray State; now a graduate student in physics at Purdue Univ.)
Nathan Todd (2009-2011, Purdue
undergraduate; now a graduate student in physics at Washington Univ.)
Mark Hannel (2010-2011, Purdue
undergraduate; now a graduate student in physics at NYU)
Satya Nagarajan (2010-2011, Purdue
undergraduate; now a graduate student in physics at Ohio State)
Zarah Ahmad
(2010 REU student from South Eastern Missouri State)
Mallory Young (2009, REU student from
Hendrix Univ.; now a graduate student in seismology at Australian National
University)
Emily Grace (2008-2010 Purdue
undergraduate; now a graduate student in physics at Princeton)
Alexandra Lupu (2007, REU student from
Cornell Univ.)
Kari
Frank (2007-2013, Purdue graduate student, PhD 2013, research associate at Penn
State)
Justin
Bankert (2006-2010 Purdue undergraduate; graduate student in physics at Johns
Hopkins)
Alan Meert (2006-2009 Purdue
undergraduate; graduate student in physics at U. Penn)
Suzanne
Lorenz (2006-2012, Graduate Student, PhD 2012, now lecturer at U Alaska)
Major Software Projects:
X-ray Monte Carlo
(XMC): Detailed X-ray Monte Carlo
Simulation Code
Photon Simulator (PhoSim): Detailed Ab Initio Photon Optical/IR Monte
Carlo Simulation Code
Telescopes:
XMM-Newton Observatory (http://xmm.vilspa.esa.es)
Chandra X-ray Observatory (http://chandra.harvard.edu)
LSST (Large Synoptic Survey Telescope) (http://www.lsst.org)
Suzaku (http://www.astro.isas.ac.jp/suzaku)
Sloan (http://www.sdss.org)
Hubble (http://hubble.nasa.gov)
Subaru (http://naoj.org)
JWST (James Webb Space Telescope) (https://jwst.stsci.edu)
Dark Energy Survey (DES) (http://www.darkenergysurvey.org)
WIYN (http://www.wiyn.org)
Biographical Information:
Education:
PhD,
Physics, Columbia University, 2003
M
Phil, Physics, Columbia University, 2000
MA,
Physics, Columbia University, 1999
BA
Honors, Physics, University of Chicago, 1997
Professional History:
2012-
Associate Professor of Physics, Purdue University
2006-2012 Assistant Professor of Physics, Purdue University
2003-2006 Postdoctoral Research Associate, Stanford University and SLAC
1997-2003 Graduate Research Assistant, Columbia University
1994-1997 Undergraduate Research Assistant, University of Chicago and
Fermilab