The Sun at Millimeter Wavelengths (Supervisor: Dr. Adam Kobelski)
Due to the relatively small height of the chromosphere (of order 1000’s of km) through which the temperature and density change by many orders of magnitude via a complex and dynamic layering, the solar chromosphere is one of the more diﬃcult atmospheric layers of the Sun to observe and model. Recently, the Atacama Large Millimeter Array (ALMA) has become available for solar observations, providing a unique and robust linear thermometer of the solar chromosphere. In this project, one student will have the opportunity to utilize ALMA solar observations in conjunction with readily available support observations of diﬀerent atmospheric layers (from instruments such as the Solar Dynamics Observatory and the Interface Region Imaging Spectrograph) to better understand the ﬂow of energy through the chromosphere. The student will learn the basics of Python, data analysis, and solar plasma physics, which should result in a publication of the properties of the Sun at millimeter wavelengths. In later years, the project will also include observations from the up-and-coming 4m Daniel K. Inouye Solar Telescope (DKIST) which will observe the Sun from the near infrared to the near ultraviolet.
Supermassive Black Holes (Supervisor: Dr. Sarah Burke Spolaor)
A main research focus of GWAC is to lead gravitational-wave searches for signals from binary supermassive black holes using the North American Nanohertz Observatory for Gravitational Waves (NANOGrav; Figure 1). NANOGrav, an NSF Physics Frontiers Center, is an international collaboration that is using pulsar timing to search for gravitational wave signals from supermassive black hole binaries. There is the opportunity for one REU student to build an online database of supermassive black hole binary systems from the literature, extracting the basic parameters from these targets. This is part of an ongoing eﬀort to build a comprehensive database of published binary systems. The student will then run NANOGrav software pipelines to search for (and place limits on) gravitational-wave signals from the systems in the database.
Figure 1 - Binary supermassive black holes form in galaxy mergers and are expected to be among the brightest gravitational-wave sources in the Universe. A number of candidates currently exist in the literature, and the sensitivity of NANOGrav is now breaching the expected signal level from a number of those objects. At WVU we have developed algorithms to use binary models garnered from electromagnetic emission to raise the sensitivity of our gravitational-wave searches.
Gas in the Interstellar Medium (Supervisor: Dr. Loren Anderson)
Because of the low excitation temperature, the 4.8GHz transition of formaldehyde (H2CO) is frequently seen in absorption, even against the cosmic microwave background18. Formaldehyde absorption is expected to be strongest foreground to a bright source of 4.8GHz continuum emission. Many authors have used this fact to determine the distances to the continuum sources19,20,21,22. We have a large (400-hour) Green Bank Telescope (GBT) survey of formaldehyde in the Galactic plane (Figure 2), the ﬁrst such large-scale survey. Early analysis of these data surprisingly shows the formaldehyde absorption has no discernable relationship with radio continuum sources, and therefore its use in distance determinations is suspect. One to two REU students will investigate whether the old assumption about formaldehyde being seen in absorption toward bright continuum sources is correct, by comparing absorption found in lines of sight toward continuum sources and also nearby regions. Once this project is completed, later REU students will also create a catalog of formaldehyde clouds, analyze their Galactic distribution, and compare this distribution to that of other tracers.
Figure 2 - A portion of the data from Dr. Anderson’s GBT formaldehyde survey integrated over all velocities (background), with radio continuum emission shown as green contours. There are 10s of formaldehyde clouds in this small patch of sky that are clearly detected in absorption (dark regions), but the strength of this absorption does not appear to be correlated with the strength of radio continuum emission.
BlackHoles@Home (Supervisor Dr. Zachariah Etienne, LIGO collaboration member)
In the spirit of SETI@Home, BlackHoles@Home is an in-development volunteer computing project that leverages consumer-grade computers to generate an enormous catalog of (numerical-relativity-based) theoretical gravitational waveform predictions for black hole binaries (the most common LIGO source). Current catalogs have been suﬃcient for the rather noisy gravitational wave observations to date (noisy signals are largely insensitive to black hole spins), but the catalogs will need to grow enormously to maximize the science from louder gravitational wave signals. Therefore, projects like this are critically important for the future of gravitational wave astronomy. One REU student will learn the basics of gravitational wave astrophysics, numerical relativity, and gravitational wave source modeling, and will take part in the analysis of simulation data from BlackHoles@Home.
Figure 5 - Proof-of-principle black hole binary inspiral calculation using the BlackHoles@Home infrastructure. The green lines indicate the trajectory of the two black holes, and the color scale shows conformal factor, which ranges from zero (inﬁnite curvature) and one (zero curvature).
Fast Radio Bursts (Supervisors: Drs. Duncan Lorimer, Maura McLaughlin, Sarah Burke Spolaor)
Fast Radio Bursts (FRBs) are bright, highly dispersed, radio pulses of cosmological but unknown origin ﬁrst discovered by a WVU undergraduate student in 2007. As one of the hottest topics in time-domain astrophysics today, FRBs oﬀer students a gateway into astrophysical research, radio astronomy instrumentation, data analysis techniques, and discovery science. Two REU students will participate in a number of ongoing searches for new FRBs that our group is involved in. REU students will create a uniform analysis of multi-telescope data sets to search for FRBs over a wide range of sky positions, observing frequencies and sensitivity levels. Our pipeline for such analyses (Figure 3) makes use of oﬀ-the-shelf pulse discovery code, as well as state-of-the art single-pulse classiﬁers that in turn use deep learning networks to winnow down vast numbers of candidate signals. The students would be inspecting output from this search classifying and measuring the properties of the detected pulses.
Figure 3 - Flow diagram showing single-pulse detection pipelines used to search for FRBs.. This project combines elements from data science: inherently large data set manipulation (the DADA buﬀer and Heimdall are standard data analysis tools within the community): deep learning networks to winnow down candidate pulses using the FETCH software package developed at WVU and state-of-the-art databases using elasticsearch to manage the bookkeeping aspects of the project.
Pulsar Searches (Supervisors: Drs. Duncan Lorimer, Maura McLaughlin)
The group at WVU is involved in multiple large-scale pulsar surveys with the Green Bank and Arecibo telescopes. These searches are critical for discovering high timing precision millisecond pulsars that will increase the sensitivity of the NANOGrav pulsar timing array. Such pulsar searches also reveal exotic binaries that can be used to test general relativity and constrain the neutron star equation of state, young pulsars in supernova remnants that can tell us about supernova kick velocities, pulsars with a range of emission properties and intermittency timescales that inform the physics of pulsar emission, and can discover new FRBs. One REU student will analyze pulsar and transients data, lead follow-up observations of newly discovered pulsars, and learn how to “time” pulsars and thereby determine their periods, period derivatives, and binary parameters (if applicable). This project is expected to result in a publication with timing solutions for a number of newly discovered pulsars.
Figure 4 - The sky covered from the start of the Green Bank Northern Celestial Cap (GBNCC) survey from 2009 until 2019. Thus far, 161 pulsars, including 20 MSPs and 11 RRATs, have been discovered in this survey. The REU students funded from this proposal would help process the data accumulated in 2019 and the ﬁrst half of 2020, which we expect to result in the discovery of ~20 pulsars.
Mapping the circumgalactic medium (Supervisor: Dr. D.J. Pisano)
Theories of galaxy formation predict that, in the present day, low mass galaxies in low density environments should be accreting gas predominantly in a cool phase. UV absorption line studies of the circumgalactic medium (CGM) have shown that up to half of the baryonic mass in the CGM is in the cool phase, but does not reveal if this gas is being accreted onto the galaxy disk. By observing this gas in HI emission using sensitive radio telescopes such as the GBT, we can map the distribution and dynamics of this gas at HI column densities a factor of a thousand below that found in galactic disks.
With over 50 galaxies mapped with the GBT so far, one or two REU students will work to quantify the nature of the gas in the CGM and shed light on ongoing gas accretion in the local universe.
Figure 6 - Maps of HI from the GBT (red) and Westerbork Synthesis Telescope (yellow) overlaid on an optical image (blue). The extra HI visible from the GBT data between NGC 6946 and its companions is consistent with ongoing cold accretion.