Dr. Justin Robinson

Physics & Astronomy Lecturer
GSU Affiliate Director, GA Space Grant Consortium
Program Manager, Astronomy on Tap Atlanta

About Me

My name is Justin Robinson, and I am a 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 an environment created by a supermassive black hole that actively feeds 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 that host an AGN such as this, and also use the behavior of these environments to measure black hole masses (animation credit: DESY/Science Communication Lab).

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 measure the rotation speeds of nearby galaxies hosting an AGN.

My Work

Select Publications

"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

Abstract

"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

Abstract

Links

AGN Black Hole Mass Database

NASA Extragalactic Database (NED)

Extragalactic Distance Database (EDD)

I am the director of the Three Taverns Astrophysics Lecture Series. Our monthly series, which we premiered in October 2023, consists of a Georgia State University graduate student or faculty guest speaker, followed by stargazing sessions with a 6-inch Celestron NexStar 8SE Go-To Telescope. Each talk is geared for a general audience, and topics have ranged from small stars, the Milky Way galaxy, the expansion rate of the Universe, supermassive black holes, and active astrophysics research conducted at GSU. Click on the image above for more info on this month's event!

September Event:
'A Star is Born... Then Dies: The Story of the Life Cycles of Stars'
Speaker: GSU Astrophysics Graduate Student Colin Kane
Date: Thursday, September 26th, 8-9:30pm

The Tully-Fisher relation is a correlation between the rotational velocity of a spiral galaxy and its intrinsic brightness. Using this relation, measurement of the rotation speed allows the true brightness of a galaxy to be estimated.

The Tully-Fisher relation's main importance to extragalactic astronomy is distance measurement. The relation predicts a spiral galaxy's intrinsic brightness, which when compared to its apparent brightness observed from Earth allows the distance to the galaxy to 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 2024

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

ASTR 1020K: Stellar & Galactic Astronomy
M, W, 12:30pm - 1:45pm

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

PHYS 1111K: Introductory Physics I
T, Th, 5:30pm - 6:45pm

Reverberation Mapping is a technique used to measure the mass of a supermassive black hole. As black holes are messy eaters, the rate at which they feed is variable and random. We can detect this activity by measuring how the light emitted from the accretion disk around the black hole changes over time (~days to weeks). Some of that light is emitted perpendicular to our line of sight, eventually crashing into gas clouds rotating around the black hole. We then monitor the remitted light from those clouds over time, the echo of the original signal that is delayed in time due to the extra path length the photons travel before heading our way. The echo, or reverberation, allows the size of this region to be measured, which when combined with the rotation speed of the clouds allows the mass of the supermassive black hole to be measured.

I use reverberation mapping data to model the these 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). Our team consists of undergraduate and graduate ambassadors from Georgia State University, Georgia Tech, and Kennesaw State University. Since the founding in 2018, we have impacted ~10,000 K-12 students in 40 unique schools across 6 Atlanta 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:

GOT Space Webpage

Office Hours

Mondays
3:00pm - 4:00pm

Tuesdays
1:00pm - 3:00pm

Talks

"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

EMAIL:

jrobinson138 (at) gsu.edu

OFFICE:

1 Park Place
Office 431
Atlanta GA, 30303