About Me

My name is Justin Robinson, and I am a visiting lecturer of physics and astronomy 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.

AGN Host Galaxies

An active galactic nucleus (AGN) is a supermassive black hole actively feeding on nearby material. AGN activity generates an enormous amount of energetic feedback back into the galaxy, which is thought to play a major role in galaxy evolution over cosmic time. 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.

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).

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



Facebook Group

I am the vice president of the Troy Astronomical Society (TAS). Formed in 2021, the TAS is a club comprised of amateur astronomers, professional astronomers, physicists, and undergraduates of all majors. During the fall and spring semesters, we hold monthly meetings featuring astronomy talks, recent astronomy news, and observing sessions. Click on the image above to join our Facebook group!

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).

Fall Semester 2023

ASTR 1010K: Astronomy of the Solar System
M, W, 9:30am - 10:45am
Aderhold Learning Center 2

ASTR 1010K: Astronomy of the Solar System
M, W, 5:30pm - 6:45pm
Langdale Hall 203

ASTR 1010K: Astronomy of the Solar System
T, Th, 11:00am - 12:15pm
Langdale Hall 200

PHYS 1111K: Introductory Physics I
T, Th, 12:45pm - 2:00pm
Aderhold Learning Center 203

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.


I am the faculty lead for the Georgia Outreach Team for Space (GOT Space). Since the founding of GOT Space in 2018, our 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: 

Office Hours

Monday, Wednesday, Friday

11:00am - 12:00pm

Office: 1 Park Place #431


"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


jrobinson138 (at) gsu.edu


1 Park Place
Office 431
Atlanta GA, 30303