Research directions of the Center include theoretical astrophysics, with emphasis on computation and simulation; experimental astrophysics, with emphasis on the dark part of the universe and data mining; and particle physics, especially as related to the search for and theoretical understanding of dark matter particles at the LHC.
Astrostatistics is concerned with developing statistical techniques for
the analysis of astrophysical data. Carnegie Mellon has a unique
established group of researchers in astrostatistics who have tackled a
wide range of astrophysical problems. Recent research topics include:
analysis of the Cosmic Microwave Background, estimating the dark energy
equation of state, analysis of galaxy spectra, detecting galaxy clusters
via the Sunyaev-Zeldovich effect, identifying filaments, and estimating
density functions with truncated data. A common theme in this work is
the goal of detecting subtle, nonlinear signals in noisy,
high-dimensional data. The group plans to be deeply involved in future
large surveys such as the LSST.
As petascale computing becomes a mainstay in many fields of scientific
research, Computer Science researchers at Carnegie Mellon aim to
develop the software, architectures, and community expertise to use these
machines optimally. Emerging advances in multiscale modeling, simulation
machine learning, data mining, and visualization can be
exploited at the petascale for future scientific discovery. In particular,
research focuses on developing data-intensive scalable computing (DISC)
architectures and algorithms for managing and serving scientific data and computations
to potentially very large user bases; developing scalable algorithms, data
mining, and machine learning techniques for analyzing and gaining
knowledge from massive amounts of data such as those to be gathered
by the LSST; and developing the tools for doing cutting-edge numerical
numerical simulations relevant to cosmology.
From the study of the earliest energy emission in the universe - the
Cosmic Microwave Background Radiation - to the evolution of galaxies and
the formation of large-scale structure, Center researchers are part of
the worldwide scientific effort to determine the basic cosmological
parameters, investigate the nature of dark matter and dark energy, and to
describe and understand the evolution of the universe. Many of these
parameters are expected to be tied down using data from current and
planned ground-based and space-based observatories. Carnegie Mellon has
joined the collaboration building the Large Synoptic Survey Telescope,
which will be the premier ground-based survey telescope in the next
decade. The analyses of these data sets are very challenging and will
require both the development of highly sophisticated simulations and the
application of the latest tools in data-mining, statistics, and computer
science. Carnegie Mellon is working as well on partnerships to build the
Cylinder Radio Telescope to explore the universe, and especially the
nature of dark energy, using the 21 cm radiation from neutral Hydrogen.
Theoretical astrophysics research carried out at the Center focuses on the
formation of structure in the universe and the role played by dark matter
and dark energy. Large scale cosmological simulations are used as a tool
to investigate the formation of galaxies and the growth and evolution of
their associated super-massive black holes. The material in between
galaxies is also an active area of study, as it contains the gas from
which future stars will form. As we look back in time to the so called
"dark ages" before the first stars formed, all these topics converge, and
important roles are played by the first black holes, earliest galaxies and
intergalactic gas in the re-ionization of the universe. This epoch is just
beyond the current observational frontier, and theoretical predictions are
being made for what will be seen, work made possible by the development of
petascale simulation algorithms and physical modeling at the McWilliams
Center. The Center's dedicated computer cluster, Ferrari, and the Moore
supercomputer shared with Computer Science will be important facilities in
carrying out this research.
Theoretical Particle Physics
The LHC (Large Hadron Collider) will produce collisions of protons at
energies never before reached. The products of these collisions could
very well include the dark matter particles that compose twenty-three
percent of the mass-energy in the universe. Indeed, there are compelling
arguments that the energies at which the LHC operates are exactly in the
window to see Weakly Interacting Massive Particles (WIMPs). The
remarkably successful Standard Model (SM) of particle physics however,
does not include WIMPs, or any other realistic dark matter
candidate. With data soon to come from the LHC, theorists in the Center
will be part of the world-wide challenge to extend the SM in a way which
is consistent with both the mathematics of quantum field theory and the
bounds arising from laboratory experiments and cosmological
observations. In particular, the discovery of a dark matter candidate
would allow us to study its properties in a laboratory setting and,
together with theoretical insights, to develop an underlying theory that
encompasses both the SM and the new physics that includes dark matter.
Experimental Particle Physics
Carnegie Mellon is one of 155 institutions involved in building and
operating the Compact Muon Solenoid (CMS), one of the two major detectors
at the Large Hadron Collider (LHC). Carnegie Mellon physicists
constructed the state-of-the-art electronics, consisting of 150,000
channels, for the end-cap muon detectors of CMS. A prime experimental
activity at the LHC will be searching for, and hopefully studying, the
properties of dark matter particles that may well be produced in this new
energy regime. For example, a widely-studied candidate for the dark
matter particles is the neutralino, if it is the lightest and most stable
of a whole set of new supersymmetric partners to each of the particles of
the Standard Model. Experimental particle physicists in the Center will
be searching the CMS data for evidence of the neutralino or other
possible dark matter particles, and then studying their properties once
they are found.
Research CollaborationsSloan Digital Sky Survey III
Carnegie Mellon University joined the Sloan Digital Sky Survey (SDSS) as full members in 2011. Cosmologists in the McWilliams Center are focusing on the BOSS (Baryon Oscillation Spectroscopic Survey) experiment, which will constrain dark energy models and cosmic geometry. A new 1000 fiber multiplexed spectrograph has been installed on the 2.5 meter SDSS telescope at Apache Point, New Mexico. 10,000 square degrees of the sky are being surveyed over a 5 years period, resulting in a catalog containing 1.4 million Luminous Red Galaxy redshifts and 160,000 high redshift quasar spectra. As an example of the power of the new survey it should be noted that in the latter case this represents a factor 50 improvement over the previous largest sample (from an earlier incarnation of the SDSS). By using this observational data to map out the baryon oscillation scale, which represents a "standard ruler," the Universe's distance scale will be measured to order 1% at redshifts z = 0.3 and z = 0.6 (using galaxies) and z = 2.5 (using the forest of Lyman alpha absorption seen in the quasar spectra). Alongside these cosmological constraints, the survey represents a rich source of data that will improve our knowledge of the formation of galaxies and of the intergalactic medium. At the present time, large amounts of data have already been obtained and analyzed, and CMU scientists have taken part in the most recent data release, which includes the largest color image of the sky ever made, the first measurement of 3D structure in intergalactic space and measurement of galaxy clustering on the largest scales yet.
Sloan Digital Sky Survey IV
Carnegie Mellon University joined the 4th round of the Sloan Digital Sky Survey (SDSS-IV) as a full institutional member in 2013. The survey will start in 2014 and run through 2020. All the observations will be carried out using the 2.5 meter SDSS telescope at Apache Point, New Mexico. 7500 square degrees of the sky are being surveyed over a four-year period, resulting in a catalog that will contain 0.6 million galaxy spectra at redshifts, z, from 0.6 to 1.0, and 750,000 quasar spectra from z = 1 to 3.5.
Cosmologists in the McWilliams Center are focusing on the eBOSS (Extended Baryon Oscillation Spectroscopic Survey) and MaNGA (Mapping Nearby Galaxies at APO) experiments.
eBOSS will achieve the best ever measurements of cosmic expansion to a distance of 12 billion light-years. It will provide the first measurements across the critical epoch between 6.5 and 11 billion light-years, the predicted "onset time" for dark energy. Using observational data to map the scale of baryon acoustic oscillations, which represents a "standard ruler," the universe's scale will be measured to order 1% at redshifts z = 0.7 and z = 0.9 (using galaxies), z = 1.5 (using quasar spectra) and z = 2.5 (using the forest of Lyman alpha absorption lines seen in the quasar spectra). eBOSS will also include a massive sample of variable stars selected from time-domain imaging surveys, follow-up on a unique sample of X-ray sources, and create the largest existing sample of accreting supermassive black holes.
MaNGA will uncover the internal structure and formation history of 10,000 galaxies and characterize the diversity of their evolutionary histories. It will contain the largest sample of galaxies ever observed in resolved spectroscopy by more than a factor of ten. With many spectra across the extent of each galaxy to trace its assembly history and dark matter content, MaNGA will provide a uniquely rich, legacy data set.
Dark Energy Spectroscopic Instrument
Carnegie Mellon was a participant in the Dark Energy Spectroscopic Instrument (DESI) from the time of one of its predecessors, BigBOSS. DESI is a ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with a wide-area galaxy and quasar spectroscopic survey. The survey is planned to begin in 2018 using the four-meter Mayall Telescope at Kitt Peak National Observatory and a robotically-actuated, fiber-fed spectrograph capable of taking 5000 simultaneous spectra over a wavelength range from 340 nm to 1060 nm. Using data from imaging surveys that are already underway, spectroscopic targets will be selected that trace the underlying dark matter distribution. The DESI survey should deliver 20 million galaxy spectra that will yield measurements of BAO and the expansion history of the universe to the sub-percent level of accuracy, as well as measurements of the clustering of dark matter at small scales and redshift space distortions up to z = 1.7. This would be at least an order of magnitude of improvement over SDSS-III both in terms of the number of galaxies mapped and also the comoving volume of the Universe probed.
The Large Synoptic Survey Telescope
Carnegie Mellon joined the Large Synoptic Survey Telescope (LSST) collaboration early in 2008 as a participating institution. The LSST will be a new kind of telescope that combines a very wide field of view, moving quickly between images, and ability to observe very faint objects. Located on a mountain ridge in the Chilean Andes, the LSST will take more than 800 panoramic pictures each night and cover the sky twice each week. The 3.2 Giga-pixel camera will acquire about 20 Terabytes of data each night. Over the ten-year survey in six broad photometric bands starting in the middle of this decade, each region of the sky will be covered roughly 2000 times. Fred Gilman is a member of the Board of Directors of the LSST Corporation.
November, 2009, The LSST Science Collaborations and project members have published a book documenting the science that can be done during the course of operation of the LSST. This LSST Science Book can be downloaded as a PDF file in its entirety (596 pages, over 50 Mb) or by chapter. The current version was made public on October 16, 2009. It is anticipated that it will be updated in a year or two. It can be downloaded by going to http://www.lsst.org/lsst/scibook
Euclid is an upcoming (2020s) space-based cosmology survey led by the European Space Agency (ESA) but with recent involvement from NASA in the form of an agreement that allows 40 US scientists to participate as full members of the Euclid survey. Shirley Ho and Rachel Mandelbaum are among the 40 in that group. The Euclid mission will carry out both imaging and spectroscopic surveys, with the goal of measuring the growth of cosmological structure with time using a wide-field weak lensing survey, as well as constraining geometry using baryonic acoustic oscillations (BAO). The ultimate goal is to constrain dark energy very precisely, at the level of a Stage-IV dark energy experiment. Because of the unique capabilities of a space-based telescope - in particular, the high resolution of the imaging and the ability to easily measure at infrared wavelengths - the Euclid mission will also have interesting synergies with some of the ground-based dark energy surveys that will be taking place around that time, such as the LSST survey.
The HyperSuprimeCam (HSC) survey is a project to carry out a wide-field imaging survey at the 8.2m Subaru telescope, based on a collaboration between the Japanese and Taiwanese astronomical communities and Princeton University. Rachel Mandelbaum is also a member of this collaboration. HSC is a new instrument that was commissioned at the Subaru telescope in late 2012, and the plan is to use it starting in spring 2014 to carry out a 3-layer survey. The wide layer of the survey will focus on weak gravitational lensing, which can be used to map out the statistical growth of cosmological structure with time during the past ~7 billion years. The deep and ultradeep layer will cover smaller volumes but look at the more distant past to study various galaxy populations and AGN. The project is expected to take 300 nights over a 5-year period, and will provide a bridge to Stage-IV surveys such as the LSST project.