I am interested in the evolution of galaxies and the processes which drive that evolution.
For this, I study the active phases of galaxies: mergers, starbursts, and active galactic nuclei (AGN).
I analyze both observations (primarily in the radio-through-optical regimes) as well as N-body simulations to understand how mergers drive the growth of stellar mass and how feedback processes eventually halt that growth.
Read on for brief summaries of specific domains.
Dynamical Models of Galaxy Mergers
The redistribution of stars and consumption of gas by star formation and AGN during galaxy interactions and mergers have a strong influence on the properties of the galaxies involved, driving significant morphological transformation.
I am matching dynamical models to observations of local mergers in order to facilitate detailed comparisons between numerical models of star formation and the actual star formation taking place in these systems.
This modeling effort will accurately timestamp individual systems, something not previously available for a sample of galaxy mergers.
To the left is a visualization of the gas in a simulated merger of two disk galaxies (with orbital parameters matched to NGC 2623, though the video has not been rotated to match our viewing direction).
The Interstellar Medium of Luminous Infrared Galaxies
There exist populations of galaxies where the bulk of their energy is emitted in the infrared.
The “Luminous Infrared Galaxies” (LIRGs) are powered by a combination of star formation and AGN.
In addition to the numerical simulations described above, I am also investigating the atomic and molecular gas properties of these systems via radio and mm observations of atomic and molecular gas tracers.
These observations are being studied to understand the properties of the fuel available for star formation and AGN fueling.
As part of this effort I am also performing a survey of the neutral hydrogen (H I) in U/LIRGs to obtain kinematics for the above dynamical modeling, and to determine the distribution of the atomic gas in these systems.
Additionally, I am using emission from molecules such as CO, HCN, and HCO+ to study the physical conditions in the gas directly associated with star formation.
Dwarf Galaxy Interactions
Little is known about interactions between dwarf galaxies, compared to more massive galaxies.
However, by number, mergers between dwarfs are expected to be more frequent than mergers between massive galaxies, but it is unclear how these interactions will affect the star formation rates, stellar masses, and gas content of dwarfs.
I am part of the TiNy Titans (TNT) survey of local dwarf galaxies.
Our SDSS-selected sample of isolated dwarf galaxy pairs and a matched sample of non-isolated pairs and individual dwarfs is being used to study the effect of interactions and mergers on dwarf galaxies.
Additionally, we are using large-volume cosmological simulations to obtain theoretical predictions for these interactions.
I am pursuing optical integral field unit observations of dwarf-dwarf mergers and dynamical models for individual pairs.
Active Galactic Nuclei
While it only takes a relatively small amount of gas to fuel a supermassive black hole, the energy output can potentially affect the entire host galaxy.
I am interested in the interactions between radio jets and the ambient host galaxy, as well as the broadband emission from AGN and their hosts.
Studying the broadband emission can disentangle the power sources of these systems: star formation vs AGN activity.
Additionally, I am interested in studying the rare examples of “dual AGN” – galaxy mergers where both supermassive black holes are simultaneously accreting.
These systems may provide critical information on the role of AGN feedback in galaxy evolution.
I am part of an international team, working on the optical integral field unit and millimeter spectral line observations of these objects.
I am a member of several collaborations which are focused on merger-driven galaxy evolution.
These projects have or are in the process of assembling large multi-wavelength imaging and spectroscopic datasets to facilitate the studies described above.
In all collaborations I am actively working on (sub)mm and optical observations as well as numerical modeling of the ongoing mergers.
GOALS: The Great Observatories All-sky LIRG Survey
GOALS is a multiwavelength survey of the most IR luminous galaxies in the nearby universe. The aim of GOALS is to study extreme star formation, AGN, and merger-driven galaxy evolution. I am leading aspects of the (sub)mm studies of the ISM of GOALS galaxies as well as dynamical modeling of the mergers. I am also working on observations and analysis of optical integral field spectroscopy.
TNT: TiNy Titans
TNT is focused on interactions and mergers of dwarf galaxies in the nearby universe. Our understanding of dwarf galaxy interactions is limited, compared to our understanding of massive galaxies. Yet dwarf-dwarf interactions may be better analogs to hierarchical assembly at high redshift. I am actively involved in numerical modeling of local dwarf-dwarf mergers and am leaving an integral field spectroscopy program on TNT galaxies.
MODA: Multiwavelength Observations of Dual AGN
website coming soon
MODA is focused on detailed multi-wavelength studies of the few confirmed dual AGN systems (mergers hosting two AGN with separations less than 10 kpc). The aim of MODA is to understand the impact of AGN on merger-driven galaxy evolution at the phase of a merger where the galaxies are near coalescence and nuclear feedback is expected to have its strongest influence. I am performing (sub)mm and optical integral field spectroscopic observations of these systems, and dynamical modeling of the host mergers.
A list of my publications is available in my CV, on NASA ADS (peer reviewed), on arXiv/astro-ph, and via my ORCID (0000-0003-3474-1125).
A copy of my PhD dissertation, “The Dynamics and Cold Gas Content of Luminous Infrared Galaxy Mergers in the Local Universe” can be downloaded from the Library at the University of Virginia.
Many of the scripts I use for processing and analysis of both data and simulations are available in a github repository.
Project-specific scripts will be added to github repositories after that paper's acceptance. Code associated with the following paper is currently available: