Turning on the Light and Looking Back in Time - Emission Line Nebulae, Black Hole Variability, and the Circumgalactic Gas Reservoir

This research program aims to use extended emission line nebulae to map out the variability of active galactic nuclei (AGN) over timescales from ten thousand to one hundred thousand years, and at the same time, to make the graduate school environment work better for today’s students. Extended nebulae illuminate the circumgalactic gas that is fueling and being impacted by galaxy and black hole growth.

The principal investigator and students at New Mexico State University will (1) build an efficient search algorithm for finding AGN-powered emission line nebulae in the local universe, (2) map out the ionization histories of the central AGN powering the emission, and (3) study the host galaxies, circumgalactic gas, and local environments around AGN with a range of ionization histories. The environment of graduate school has a profound impact on students, both professionally and psychologically.

This proposal will address this through (1) the development of a workshop to guide students in acquiring versatile research skills and in strengthening their mental health, and (2) the creation of a writing group to foster the consistent writing that develops scientific thinking, produces scientific contributions in timely manner, and enhances overall morale.

AGN are known to be highly variable, but our understanding of the factors that influence AGN over long timescales (10^4 – 10^5-years) is quite limited. Extended emission line nebulae are the key to probing variability on these timescales, but biases exist in current samples, and we are only beginning to understand how this glowing circumgalactic material and the local environment fuel and are impacted by the central galaxy and AGN.

This program will advance knowledge by using recent public surveys and a morphological search algorithm to expand the known sample of AGN-powered nebulae to fainter targets and a broader range of ionization histories, i.e., without being biased by the current luminosity of the associated AGN. Leveraging the greater amount of time available on longslit/multislit instruments on 3-4m class telescopes, the researchers will obtain deep, spatially-resolved spectroscopy and constrain AGN ionization histories over these longer timescales.

The program will also provide insight into the influence of the host galaxy, local environment, and kinematics of the surrounding gas that, when combined with studies of the more distant universe, will contribute to our understanding of how AGN variability and the circumgalactic gas reservoir change over cosmic time.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.