X-raying the Milky Way (Dr. Lia Corrales)
Astrophysical dust acts as either a source of contamination or an essential piece of physics, in every subject from star and planet formation to galaxy evolution and cosmology. With high resolution images from the Chandra X-ray Observatory, we will look for and study dusty structures that scatter X-ray light from distant black holes and neutron stars. X-ray spectroscopy can also directly reveal the gas phase and potentially the mineral structures of dust. I am seeking undergraduate research for a wide range of observational projects: imaging, spectroscopic analysis, and exploratory computation with Python.
Observational Stellar Astrophysics (Prof. Bob Mathieu):
As part of the NSF-supported WIYN Open Cluster Study, our group investigates the binary populations of stellar open clusters. Binary stars in clusters are not only the fuel behind cluster evolution, they also provide an intriguing opportunity to explore the interplay between stellar evolution and stellar dynamics. We use knowledge of binary star populations to study non-standard stellar products for which a coherent picture of formation and evolution is not yet fully understood. Examples of such stellar anomalies include blue stragglers and sub-subgiants.
Another focus of our group is exploring accretion dynamics of young binary systems with circumstellar disks. Remnants from formation, these disks affect the orbits and eventual masses of binary systems. Despite being the most common products of star formation, binary evolution at this early phase remains an open topic of research.
Depending upon the particular interests of students, possible projects could involve measuring precise stellar radial velocities using the multi-object spectrograph of WIYN, developing new techniques to determine parameters for binaries, investigating triple systems using imaging and spectroscopic data, searching for faint stellar companions in anomalous stellar systems, or analyzing new data of pre-main-sequence binaries from the SALT high-resolution spectrograph. An observing run at the WIYN Observatory would be likely.
Towards a Better Understanding of our Nearest Extragalactic Neighbors (Prof. Eric Wilcots)
One of the little-appreciated facts about the Magellanic Clouds, the nearest extragalactic neighbors to the Milky Way, is that they are simply the closest examples of a morphological class of galaxy that is well represented in the local Universe. The recent implication that the Clouds could be making their first passage by the Milky Way has weakened the notion that the characteristic structure of the Large Magellanic Cloud - a single spiral arm and a luminous stellar bar possibly offset from the center of the galaxy - is a result of its interaction with the Milky Way. Professor Wilcots has a number of research projects for REU students motivated by the idea that one way to better understand the LMC is to better understand the morphological class of Magellanic spirals in general. The various projects include:
analyzing new observations obtained with the WIYN 3.5m telescope to measure the stellar and ionized kinematics of Magellanic spirals to determine their mass distribution, their star formation history, and whether or not their bars are real;
analyzing new data from the Australia Telescope Compact Array radio telescope to map the distribution and kinematics of the neutral gas in Magellanic spirals;
analyzing archival and SDSS data to build a three-dimensional model of the large-scale environments of Magellanic spirals.
Galaxy Groups (Prof. Eric Wilcots)
The broad bimodal distribution of galaxies between a population of red, passively evolving galaxies and blue, star-forming ones is now well-established. There is also broad agreement that the transformation of galaxies from the so-called blue cloud to the red sequence is a result of removal or exhaustion of a galaxy’s supply of gas and the subsequent shutting down of its star formation. Meanwhile, modern simulations of the formation and growth of large-scale structure in the Universe show that galaxy clusters are the result of a hierarchical process by which individual galaxy groups merge. The bulk of current observations indicate that the transformation of galaxies is largely complete once they are well-established residents of large clusters. All of this suggests that the transformation of galaxies largely takes place outside of the central regions of clusters and, quite possibly, in the lower density environments of galaxy groups. This research project is targeted at understanding not only where galaxy transformation takes place, but also at understanding the relative importance of the different mechanisms by which a galaxy’s gas content is depleted. The REU student will be using archival and survey data to understand the evolution of galaxy groups; this could include applying a multiwavelength approach to correlate the star formation rate and population of active galactic nuclei within groups with their gas content and larger environment or using WIYN 3.5m and archival data to measure the dynamical growth of galaxy groups.
Galaxies and their environments (Prof. Jay Gallagher):
We are obtaining optical/infrared observations from a variety of ground-based telescopes, including the 3.5-m WIYN and the 4.2-m William Herschel Telescope, for a study of how the internal structures of galaxies are modified by their environments.
This project involves the quantitative analysis of galaxy images to define basic structures, the measurement of star formation rates, and determinations of internal stellar and ionized gas kinematics. We are applying these techniques to galaxies with special characteristics, such as those with signatures of recent disturbances, e.g., polar ring galaxies and starbursts, as well as to systems that appear to have been quiescent for long time periods (such as "super thin" disk galaxies).
This will provide an REU student with a range of opportunities for the collection, analysis, and interpretation of galaxy observations within the framework of dynamical constraints on their evolutionary processes.
X-ray astrophysics (Prof. Dan McCammon):
The last few years has seen a revolution in the spectroscopic and imaging sensitivity of astrophysical X-ray detectors. We have a very instrumentally-based program aimed at developing a new type of detector technology that measures the temperature rise produced by the absorption of single X-ray photons and can achieve energy resolutions 100 times better than a theoretically perfect CCD or solid state detector.
We are using these detectors in a sounding rocket program to study the galactic and extragalactic soft X-ray backgrounds. Improvements in the detectors will allow a search for the "missing baryons" in intergalactic space, and improved studies of the very hot components of the interstellar medium in our galaxy. We also support the deployment of similar detectors on general-purpose space-based observatories such as Astro-H. Interested students can learn fabrication and cryogenic techniques needed to assemble and test detectors, and methods of X-ray data analysis.
Warm Ionized Medium (Dr. Matt Haffner):
Under the leadership of Prof. Ron Reynolds, Wisconsin has carried out the first survey of the entire galaxy in the H-alpha emission line of ionized hydrogen. These maps show the location and effect of hot ionizing stars, but also indicate the presence of a mysterious, low density ionized gas filling much of interstellar space. The velocity resolution provided by WHAM can allow astronomers to map out the distribution of this gas, while observing other diffuse optical emission lines can characterize the temperature, chemical state, and ionization level of the gas.
Star Forming Regions and Polarization (Prof. Alex Lazarian):
Magnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the interstellar medium. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be employed. This project will deal with the development of new techniques for studies of MHD turbulence using a combination of numerics and observational data. It will be a good project for a student interested in data analysis programming, and working across both theory and observations.
New Ways of Studying Astrophysical Magentic Fields (Prof. Alex Lazarian):
Stars are born from the magnetized partially ionized gas that fills our galaxy. The magnetization of media is extremely important not only for star formation but also for many other key astrophysical processes, e.g. propagation and acceleration of energetic particles, transport of heat and heavy element accross the galaxy. Understanding of the magnetic field structure is also important for reliable studies of CMB polarization that arises from the enigmatic cosmological B-modes that cary information about the gravitational waves in the early Universe. Indeed, the polarization related to galactic magnetic fields interferes with the CMB polarization and the knowledge of the magnetic field structure can help separating the two contributions.
Two new technique of tracing magnetic field have been suggested recently by Prof. Lazarian's group. These techniques employ the modern theory of of turbulence in magnetized fluids. This theory predicts that the fluctuations of the magnetic fields and velocities develop gradients that are directed perpendicular to magnetic fields. Prof. Lazarian and his students calculated the gradients of synchrotron intensity and velocity centroids, which are the measure that can be obtained with spectral lines. The measures were compared with the directions of magnetic fields obtained from the polarization data obtained with the Planck mission. An excellent tracing of magnetic field with the gradients was reported. This work opens new prospects of magnetic field studies.
REU students are invited to participate in this exciting new direction of research to apply the developed software to the existing observational data in order to obtain the directions of magnetic fields in phases of interstellar media. Obtaining new publishable results is expected during the REU tenure.
Neutrino Astrophysics and Astronomy (Prof. Francis Halzen, Prof. Albrecht Karle, Prof. Justin Vandenbroucke, Prof. Stefan Westerhoff and Scientist Dr. John Kelley):
The completed IceCube neutrino detector at the South Pole is the first instrument with the sensitivity required to capture signals of cosmic neutrinos. Rather than collecting light, it probes the high-energy Universe by detecting neutrinos. Since the 1950s, scientists have built a compelling case for using high-energy neutrinos as ideal messengers from the most interesting, violent, and least understood phenomena in the Universe. Throughout the previous decade, an international collaboration of scientists has designed, constructed, and operated the first kilometer-scale neutrino telescope. Originally conceived at the University of Wisconsin, IceCube has transformed a cubic kilometer of natural Antarctic ice into a Cherenkov detector. Optical sensors embedded in the ice detect the photons radiated by charged particles produced in neutrino interactions. They detect the faint flashes of light created by neutrino interactions in the transparent ice.
Since early construction of the detector, the IceCube group has employed about 5 to 10 undergraduates. Although work is ongoing on the development of a next-generation detector, data analysis is a priority focused on the origin of cosmic neutrinos as well as on the study of the neutrino itself.
Additionally, students will have the option to work on the development of the Askaryan Radio Array (ARA). ARA is a pioneering neutrino detector located at the South Pole designed to detect ultra-high-energy neutrinos from cosmic ray interactions with the cosmic microwave background. Our current research is focused on separating potential neutrino signals detected by the ARA antenna arrays from the large background of thermal noise, as well as developing directional and energy reconstruction algorithms that can be used to estimate neutrino properties once such rare events are detected. REU students on this project will learn the necessary techniques in radio signal analysis, interferometric beamforming, data analysis and reduction in Python and C++, and parallel processing with graphics processing units (GPUs) in order to contribute to our research. Specific projects include, but are not limited to: raytracing of radio signals in the Antarctic ice sheet; accelerating interferometric neutrino directional reconstruction with GPUs; and optimization of detector triggers and neutrino event filters running at the South Pole.
Observational Cosmology (Prof. Peter Timbie):
The Observational Cosmology group uses two astrophysical tools to study the evolution and structure of the universe: 1) the ancient photons that make up the 2.7 K cosmic microwave background (CMB) allow us to explore cosmological history as far back as a redshift of z = 1400, some 300,000 years after the Big Bang; 2) radiation from neutral hydrogen gas at a wavelength of 21-cm traces the large scale distribution of matter and dark matter, which in turn probes dark energy, neutrino mass, etc.
Students in the Observational Cosmology group assist in building the most sensitive detectors of microwave and radio radiation possible and can learn about radio astronomy, cryogenics, superconductivity, microwave circuits and antennas, and data analysis.
REU students can choose to work on the development of a superconducting microwave sensor called a microwave kinetic inductance detector (MKID), specifically designed for measurements of the polarization of the CMB. CMB polarization is expected to arise from gravitational waves released during the inflation process during the Big Bang. Another project is to design and test antennas and receivers for the Hydrogen Structure Array, a radio interferometer under development for measuring 21-cm radiation.
Cosmic ray observations and their propagation in magnetic fields (Dr. Paolo Desiati):
After more than one hundred years from the discovery of penetrating cosmic particles from space, we still have quite a lot to learn about the origin and journey from their sources to us. The observation of cosmic ray particle energy, mass and arrival direction distributions can provide useful information on their history, especially if combined with the detection of high energy neutrinos and electromagnetic emissions such as gamma rays. To reconstruct their history it is necessary to disentangle the effects of their production at the sources with those of propagation in interstellar magnetic fields. One way to do so is to analyze experimental data collected by IceCube and IceTop and the South Pole and compare them with results from other experiments and relate them with scenarios of cosmic ray production and propagation. In addition, the study of particle trajectories in magnetic fields can provide the necessary information to reconstruct the more complicated puzzle of cosmic ray propagation in magnetized plasmas. Thus we may be able to utilize cosmic ray distributions in a given energy and mass range to probe interstellar magnetic fields within a defined distance scale and infer their diffusion coefficients.