Research

How star formation is being modified in galaxies around Virgo

My graduate student Kim Conger has used 12 micron emission from the WISE satellite to measure the extent of star-forming disks in galaxies residing a large range of densities around the Virgo cluster.  She finds that the extent of star-forming disks in cluster and filament galaxies are smaller compared to those in field galaxies.  She also compares her results to state-of-the-art semi-analytic models (SAMs) of galaxy formation.  She finds that the models predict the size of field galaxies well, but underpredict the extent of star formation in dense environments.  These same models, however, predict the correct fraction of galaxies with no star formation, implying that their implementation of environmental effects is incomplete.

The molecular gas contents and star formation rate in distant cluster galaxies

If we want to understand how the oldest present-day cluster galaxies stopped forming stars, we need to observe the progenitors of these galaxies in distant clusters.  A specifically powerful approach is to study the molecular gas contents of these galaxies, as this gas is the fuel for star formation.  I work with colleagues, including Allison Noble at ASU, to understand how the molecular gas is distributed in clusters 9 Billion Light years away.  Using extremely deep and high resolution data from the Atacama Large Millimeter Array (ALMA) we have been able to observe that these distant cluster galaxies are overabundant in their molecular gas compared to similarly star-forming galaxies in the field. We also have been able to determine that the spatial distribution of gas in these galaxies shows striking asymmetries, akin to what is found in much more mature local clusters. This indicates that even these distant and immature clusters may be able to alter the gas contents of the galaxies that lie within them.

I am leading efforts to obtain a large census of the molecular gas density in the GOGREEN and GCLASS clusters described above.

Using deconvolution to study the spatially resolve properties of distant galaxies

We are at the limit of what we can learn from spatially integrated images of galaxies.  While observations with JWST are revealing fascinating details about distant galaxies, these surveys are limited both in their wavelength coverage and in their area.  Recent advancements in mature deconvolution techniques allow us to sharpen ground-based images using our knowledge of how the images are blurred by the earth's atmosphere.  These techniques operate with no prior knowledge of how the true image looks and the newest developments have been able to improve ground-based image quality by a factor of ~3.

With these techniques we will be able to understand where galaxies cease their star formation first in dense environments, which will give us new insights into the physical mechanisms that quench star formation.

Applying deconvolution to large surveys

Schematic showing the gains in area and spatial resolution (at 1μm) achievable by deconvolving ground-based multi-passband imaging from current and future surveys (magenta to blue). The deconvolution technique, we are using has already been successfully applied to the COSMOS/UltraVISTA field by our collaborators, resulting in new images with 0.3arcsecond resolution.  We are applying the same technique, which requires no morphological priors and can be applied over large fields of view,to the GOGREEN cluster survey dataset, making publicly available multi-passband images with 0.3 arcsecond resolution over a larger area than well known JWST and HST surveys (yellow).  This work will serve as a pathfinder for future large ground-based surveys, e.g. VRO/LSST (right).