Research Focus

Research Interest

J. Drew Hogg

About Me

I am a fifth year graduate student at the University of Maryland-College Park working towards a Ph.D. in astronomy under the supervision of Dr. Chris Reynolds. My thesis work is mainly focused on understanding the physics of black hole accretion and how it connects to the broadband variability ubiquitiously observed from these systems. Most of my research is theoretically based in the development and analysis of large, global numerical models of accretion disks, but I also dabble in observational astronomy. Currently, my research is funded through the NASA Earth and Space Science Fellowship (NESSF) Program. Prior to recieving this award, I was a Joint Space-Science Institute (JSI) Fellow.


My research is focused on understanding how black holes grow through the accretion of gas from their surrounding environments. Getting a handle on this problem is difficult for a number of reasons, the largest of which is that the black hole and surrounding accretion disk is too small to directly probe with current observational facilities. However, we can use the spectro-temporal and photometric variability as an indirect probe of the physics.

Now, the majority of my efforts are aimed at understanding the dynamics, angular momentum transport, and energetics of truncated accretion disks. There is increasing empirical evidence that the accretion disks around certain black holes may be "truncated" and undergo a sharp secular change. A switch from efficient gas cooling in the outer accretion disk to inefficient cooling in the inner disk (analogous to the two phase medium of the ISM), is usually invoked to explain this transition. State transitions in stellar mass black holes and low-luminosity active galactic nuclei are often attributed to disk truncation, but the details of the physics governing the disk evolution are poorly understood. Pairing hydrodynamic and magnetohydrodynamic simulations of truncated accretion disks, I am working to shed light on this problem. This work will be published soon, so please check back!

I have also worked on understanding the distinct nonlinear signatures (e.g. lognormal flux distributions, RMS-flux relations, and interband lags) that are universally observed on the viscous timescales of accreting objects. Commonly, this phenomenology is explained evidence for "propagating fluctuations" in mass accretion rate that arise through stochasticity in the angular momentum transport. We recover these signatures in an ab initio disk simulation and find that they are driven by the slow oscillation of the disk dynamo. This work can be found here.

Outreach And Teaching

While most of my time and effort goes into my research, one of the most important things I do as an astronomer is giving back to the community. I firmly believe public outreach is an essential part of a career in astronomy because our profession is funded by taxpayer dollars and, therefore, it is our duty to share our discovery with nonscientists. Of all the sciences, astronomy is uniquely suited to capture the imaginations of people of all ages and educations because we are all innately curious about the cosmos.

I recently became a AAS Ambassador and am looking to spread my excitement about astronomy to the students of Prince George's County. I am in the process of developing a program called "Black Holes On The Blackboard", which will target elementary school aged children and show them how much fun science can be. I hope that by introducing understandable astronomical concepts we will: 1. Get them excited about astronomy and science in general, and 2. Correct or prevent misconceptions that typically plague the general public.

I am also very interested in improving the way we teach astronomy to non-scientists. My time as a teaching assistant for non-major's introductory astronomy opened my eyes to the struggles the average person has with understanding science. Typically, its not that the material is difficult, but rather, they have to overcome science and math anxiety and incorrect prior conceptions. Presenting material in a way that draws on real world experience (accretion disks are like a sink or toilet bowl) and is given in small, managable pieces seems to help the most. Semester-to-semester and student-to student, the approaches one must take change and evolve based on the individual and group. The constant adaptation is part of the reason I find teaching so exciting and interesting.

Last year was my first year teaching, but I was recognized as a "Distinguished Teaching Assistant" by the University of Maryland and "Teaching Assistant of the Year" by the astronomy department.

Public Policy

I am also very interested in both domestic and international space policy. Looking toward the future, I believe an understanding of "how the sausage is made" is essential because effective leadership relies on experience. As a grad student, the political scene is a little overwhelming, however, through my current involvement I am becoming aware of the challenges we are currently facing and issues that may become important in the upcoming years and decades.

Currently, I am a voluteer with the AAS's Communicating With Washington program and serve as my department's AAS Agent. Helping out with the Communicating With Washington program has been especially exciting because I have had the chance to go to the Hill and speak with legislators about the importance of astronomical research and some of the concerns we have. I have talked with a number of policymakers from both sides of the aisle, which has been incredibly useful for shaping my perspective on the direction scientific policy is going and what things we need to prepare for in the future.

Past Work

Before starting grad school at UMD I recieved degrees in Physics and Astronomy from the University of Colorado. I performed an analysis of optical and X-ray spectra of AGN that were newly detected with the Swift Burst Alert Telescope for my senior honors thesis. My undergraduate work introduced me to the complexity and diversity of active galaxies, which served as motivation to study the details of accretion physics. Through this work, I found a number of unique galaxies and one that may even be a recoiling supermassive black hole. I applied for, and was awarded, three orbits of Hubble observation and 10 ks of Chandra observation to conduct high spatial resolution imaging of this unique galaxy. Additionally, I am carrying out spectral follow-ups of this unique galaxy using the 4.3-meter Discovery Channel Telescope.

A career in science is a journey. More often than not, the path is unclear and you get lost, but through these academic wanderings you explore concepts that have never been never been considered before. This is the true beauty of embarking upon a career in science and I can't wait to see how it develops!