About Me

My name is Justin Robinson, and I am a fourth year astronomy PhD candidate at Georgia State University. My research interests include extragalactic distance measurements, supermassive black hole mass measurements, and relationships between active galaxies and supermassive black holes.

Green Bank Radio Telescope

The Robert C. Byrd Green Bank Telescpoe is located in the national radio quiet zone in West Virginia. It is the largest steerable instrument in the world, with a dish 300 feet in diameter and height 485 feet above the ground. I've used this telescope to observe 21cm radiation from neutral hydrogen in nearby galaxies hosting an active galactic nucleus (AGN).

AGN Host Galaxies

An AGN is a supermassive black hole actively feeding on nearby material. The accretion disk houses the gas that is orbiting around and falling into the black hole. Further away from the black hole are thick clouds moving at extremely fast speeds, and this environment is referred to as the broad line region. I measure distances to galaxies which host a supermassive black hole such as this, and also use the behavior of these environments to measure black hole masses.

My Work


"Tully-Fisher Distances and Dynamical Mass Constraints for 24 Host Galaxies of Reverberation-Mapped AGN," Justin H. Robinson, Misty C. Bentz, Hélène M. Courtois, Megan C. Johnson, D. M. Crenshaw, Beena Meena, Garrett E. Polack, Michele L. Silverstein, Dading Chen 2021, ApJ, 912, 160

"HI Spectroscopy of Reverberation-Mapped Active Galactic Nuclei," Justin H. Robinson, Misty C. Bentz, Megan C. Johnson, Hélène M. Courtois, Benjamin Ou-Yang 2019, ApJ, 880, 68



GOT Space Outreach Events

Maynard Holbrook Jackson High School & Trip Elementary School
I am the graduate lead ambassador for the Georgia Outreach Team for Space (GOT Space). GOT Space's mission:  to inspire an appreciation of STEM and STEM careers in Georgia K-12 students through the delivery of interactive presentations by graduate and undergraduate students, highlighting innovative science and engineering research.

The Tully-Fisher Relation

Image credit: NOAO
The Tully-Fisher relation shows a correlation between the rotational velocity of a spiral galaxy (the width of the emission line, corrected for the inclination of the galaxy) and its absolute magnitude. Therefore, if the rotational velocity is known, then the true brightness of a galaxy can be achieved.

    The Tully-Fisher relation's main importance to extragalactic astronomy is distance measurement. Because the relation gives absolute magnitude, if we compare that value to the measured apparent magnitude of the same galaxy, then the distance can be measured (in short, comparing how bright something actually is to how bright it appears to be shows how far away it must be).

Astronomy 1020 Lab Materials

Here you will find all materials and documentation for your Astronomy 1020 lab section. Click on each link to view/download.

Possible project topics and short summaries. Due dates for outlines, presentations, and projects listed.

Outline of due dates and details on each step of the project.

Summary and requirements for each type of possible project.


Reverberation Mapping

Image credit: NASA/JPL-Caltech
Reverberation Mapping is a technique to measure the mass of an active supermassive black hole. Light that is ejected from the accretion disk emits in all directions, some towards us, and some towards the surrounding broad line region clouds. The clouds reflect the incoming light, causing an echo in the signals we dectect from an AGN: one signal from the light emitted towards us, another signal from the reflected light. The echo, or reverberation, allows the size of the broad line region to be measured. The size in combination with the rotation speed of the broad line region clouds allows the mass of the supermassive black hole to be measured.

I use reverberation mapping data to model the broad line regions in nearby AGN host galaxies. These models tell us the geometry of the region, how it is oriented with respect to our observing point of view, and the dynamics of the gas. This allows us not only measure supermassive black hole masses, but determine if gas is actively rotating around, inflowing towards, or outflowing away from the black hole.


Since the founding of GOT Space in 2018, out team has expanded to ~20 undergraduate and ~10 graduate ambassadors from Georgia State University, Georgia Tech, and Kennesaw State University. We have impacted nearly 3000 K-12 students in 15 schools across 6 Georgia districts (and still counting!). We proudly continue to be partnered with and funded by the Georgia Space Grant Consortium.

For more information on GOT Space, or to request a presentation, please visit our website: 


"Probing Nearby Active Galaxies: Distances, Masses, Dark Matter, and Black Holes," given at the February 2021 Bradley Observatory at Agnes Scott Open House

"Fundamental Properties of Active Galaxies: Distances and Masses of Nearby Seyferts," given at the 236th AAS Meeting

Contact Me


jrob (at) astro.gsu.edu


25 Park Place South
Suite 605
Atlanta GA, 30303-2911