Gaseous, Disk-Halo Interfaces

I'm interested in gaseous, disk-halo interfaces as critical boundaries in the baryon cycle. These interfaces are imprinted with structural, kinematic, and chemical clues about the feedback and accretion processes that drive galaxy growth and evolution over cosmic time. My research focuses on optical emission-line studies of extraplanar diffuse ionized gas (eDIG) layers in nearby galaxies and their implications for baryon cycling between the disk and the lower halo.


I'm interested in the role of non-thermal pressure gradients, including turbulent motions, magnetic fields, and cosmic rays, in supporting the unexpectedly large scale heights of eDIG layers (Boettcher et al. 2016, 2019). By observing galaxies viewed from a range of inclination angles, we have found evidence that large vertical velocity dispersions driven by star-formation feedback may be integral to the properties of these layers (Boettcher et al. 2017).

At left: NGC 891 as seen on APOD  (Adam Block, Mt. Lemmon SkyCenter, U. Arizona)

The Circumgalactic Medium (CGM)

As a member of the Cosmic Ultraviolet Baryon Survey, I'm interested in the properties of the intermediate-redshift CGM. This large HST program has obtained COS spectroscopy of 15 UV-bright QSOs at z > 0.8 in fields with deep galaxy survey data, enabling absorber properties to be contextualized in their galactic environments (Chen et al. 2020). I'm leading the analysis of the damped Lyman-alpha absorbers discovered in CUBS, including the serendipitous detection of diffuse molecular gas associated with a massive, early-type galaxy at z = 0.57 (Boettcher et al. 2020, submitted).

At right: The Hubble Space Telescope (NASA)