Dr. Monique Aller

My research interests focus on observationally investigating fundamental galaxy components, including interstellar dust and gas, galaxy stellar populations, and supermassive black holes, and exploring the evolution of connections between properties characterizing these galaxy components over the past ~10 billion years. My research utilizes both ground- and space-based observational facilities at wavelengths ranging from the ultraviolet to the infrared, including the Hubble Space Telescope, the Spitzer Space Telescope, the Gemini-South Telescope, and the upcoming James Webb Space Telescope. My current research programs use a combination of new and archival observational data to study questions about the composition and evolution of galaxies, particularly in the context of the role and impact of the interstellar dust and gas, and of the circumgalactic medium.

Interstellar dust grains are composed of carbonaceous, silicate, and metallic oxide molecules. Different molecules produce unique spectral signatures which can be detected in absorption against background light sources. Our research program investigates absorption features produced by these dust grains, including the rest-frame ultraviolet feature at 2175 Å produced by carbonaceous dust, and infrared features near 10 and 20 m produced by silicate dust grains. The galaxies in which we study these dust grains range from the local to more distant galaxies, and are generally located along the sightline to a background light source, such as an active galactic nucleus (the accreting supermassive black hole at the center of a galaxy in the distant Universe). Our research seeks to answer questions such as whether silicate dust in more distant galaxies is more crystalline than that in our own Galaxy and whether the ratio of carbonaceous to silicate dust differs relative to the local Universe. This program combines data from the Spitzer Space Telescope, the Hubble Space Telescope, and the upcoming James Webb Space Telescope, among other facilities.

The absorbing galaxies in which we study the dust properties also contain neutral and ionized gas atoms which produce distinct spectral features at ultraviolet and optical wavelengths. The ratios of the abundances of different elements can be used to identify depleted (or missing in gaseous form) elements that are incorporated into dust grains. Furthermore, the spectral features produced by the gas can be used to investigate connections between the interstellar and circumgalactic gas properties in the galaxies and the dust grain properties.

In spiral galaxy disks there is a direct connection with the spiral density waves that propagate through the disk. However, what is the triggering mechanism(s) in galaxies that lack such spiral density perturbations, such as polar ring galaxies, or morphologically spheroidal/elliptical galaxies?
In collaboration with research colleagues at The University of South Carolina and Georgia Southern University, we are investigating the stellar, gas, and dust distributions in a sample of ~20 polar ring galaxies in the local Universe using multi-wavelength data. This program combines data from the Spitzer Space Telescope Infrared Array Camera (IRAC), Gemini South Gemini Multi Object Spectrograph (GMOS), and Hubble Space Telescope (HST) among other facilities.