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Dr. Monique Aller

Associate Professor of Physics & Astronomy

Observational Astronomy

Office: Statesboro Campus, Math/Physics Bldg, Rm 2050
Phone: (912) 478-0576
Link to publications: Click Here


B.A. Physics & Medieval/Renaissance Studies, Wellesley College
M.S. Astronomy & Astrophysics, University of Michigan
Ph.D. Astronomy & Astrophysics, University of Michigan
Postdoctoral Researcher, Institute of Astronomy, ETH Zurich
Postdoctoral Fellow, Dept. of Physics & Astronomy, U. of So. Carolina


Astronomy/Astrophysics Courses:

  • Astronomy 1010- Astronomy of the Solar System
  • Astronomy 4138 – Galactic Astronomy
  • Astronomy 5890 – Astronomy Research Experience

Physics Courses:

  • Physics 2211K – Principles of Physics I


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.

Hubble Space Telescope
Credits: NASA

James Webb Space Telescope
Credits: Nasa/Chris Gunn

Spitzer Space Telescope  
Credits: NASA JPL
Gemini South Telescope
Credits: NOIRLab

Examples of Ongoing Research Projects

What is the nature of interstellar dust in distant galaxies? Do the dust grains have a similar composition, grain structure, and crystallinity when compared to dust grains found in local galaxies?

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.

Fig. 6 from Aller et al. 2012, ApJ, 748, 19 ( illustrating the absorption feature near 10 m produced by silicate dust grains in the z=0.89 absorbing galaxy along the sightline to the blazar PKS 1830-211. Each panel shows the fit to a different possible dust grain. The best fit is produced by hortonolite.

Example Projects:

Example Publications:….7K/abstract…785…36A/abstract…748…19A/abstract

How does the evolution of the dust grains in galaxies connect with the interstellar and circumgalactic gas and metal enrichment properties, and with the evolution of galactic stellar populations and morphology?
Fig. 7 from Aller et al. 2014, ApJ, 785, 36 ( illustrating the relationship between the Mg II equivalent width (produced by gaseous ionized Magnesium atoms) and the 10 m peak optical depth (a measure of the absorption strength) of the silicate dust grains for six galaxy absorption systems. The right panel shows the optical depths corrected by the covering factors.

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.

Example Projects:

Example Publications:….7K/abstract…785…36A/abstract…23752705K/abstract

How is star formation triggered in galaxies?
NGC 4650A – Example of a polar ring galaxy in which we are investigating the stellar structures, star-formation triggers, and dust distribution.
Credits: Space Telescope Science Institute & Hubble Heritage Team (AURA/STScI/NASA)

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.


Last updated: 8/27/2021