Dr. Ashley R. Bemis

Allegro Fellow &
Leiden Observatory Research Associate

Expertise: Star Formation, Dense Gas, Nearby Galaxies, Radio Astronomy
Curriculum Vitae
https://orcid.org/0000-0003-0618-8473
RESEARCH INTERESTS

I am interested in star formation, its connection to dense gas, and its dependence on environment within nearby (z~0) galaxies and the Milky Way. I work extensively with observations in the radio regime using data from the Atacama Large Millimeter and sub-millimeter Array, the James Clerk Maxwell Telescope, the Sub-Millimeter Array, and others.



Outside of the James Clerk Maxwell Telescope.
THESIS WORK

My PhD thesis work (completed October 2020) focused on the relationship between dense gas (primarily as traced by HCN) and star formation (as traced by IR and radio continuum emission) in more-extreme environments than those found in the disks of normal galaxies (mergers, Ultra-Luminous Infrared Galaxies, and galaxy centers). The data were compared to the predictions of theoretical models of star formation (cf. Krumholz & McKee 2005, Padoan & Nordlund 2011, Hennebelle & Chabrier 2011, Federrath & Klessen 2012, Burkhart 2018), in addition to emissivities modeled using the radiative transfer code RADEX (van der Tak et al. 2007).

The Antennae Galaxies, Image Credit: Hubble/European Space Agency

Ongoing Research

HCN and HCO+ Emission in the Extreme Environments of Mergers and Galaxy Centers

HCN and HCO+ emission is compared at sub-kpc scales across a sample of 10 galaxies using ALMA archival data. Preliminary results were presented at  The Laws of Star Formation Conference, Cambdridge, UK in 2018 without modeling incorporated. Initial results with modeling incorporated (excluding HCO+) were presented in an invited talk at the AAS Summer 2020 meeting.

The Sample

Spiral Galaxies (3 Barred)
M83, Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: W. Blair (STScI/Johns Hopkins University) and R. O’Connell (University of Virginia)
NGC 3351 / M95, NASA/JPL-Caltech/R. Kennicutt (University of Arizona) and the SINGS Team
NGC 3627, Credit: ESO and Joe DePasquale
Circinus Galaxy, Credit: Andrew S. Wilson (University of Maryland); Patrick L. Shopbell (Caltech); Chris Simpson (Subaru Telescope); Thaisa Storchi-Bergmann and F. K. B. Barbosa (UFRGS, Brazil); and Martin J. Ward (University of Leicester, U.K.) and NASA/ESA
NGC 1808, Jim Flood, an amateur astronomer affiliated with Sperry Observatory at Union College in New Jersey, and Max Mutchler, a member of the Space Telescope Science Institute staff who volunteered to work with Jim
Interacting Systems
VV 114, Copyright: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
NGC 3256, Image Credit: NASA, ESA, Hubble Heritage (STScI / AURA) – ESA/Hubble Collaboration, & A. Evans (UVa, NRAO, SUNYSB)
The Antennae Galaxies, Image Credit: Hubble/European Space Agency
NGC 7469, Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

In addition to IRAS 13120-5453.

Directly Determining Molecular Emissivities in Milky Way Clouds

This project aims to determine molecular emissivities by comparing molecular emission, including multi-J emission of dense gas tracers HCN & HCO+, to independent gas mass tracers (i.e. dust) in Milky Way clouds. This makes use of archival data from the Herschel Gould Belt Survey (2010A&A…518L.102A).


JCMT HCN 4-3 data overlaid on the Aquila H2 column density map from the Herschel Gould Belt Survey (2010A&A…518L.102A).

UPCOMING PROJECTS

  1. I am currently imaging cloud-scale CN emission across the  Antennae Galaxies for eventual comparison with cloud-scale CO emission, star formation rate tracers, and the predictions of analytical models of star formation (see thesis work).
  2. I will be supervising a LEAPS project in the summer of 2021 in which the student will perform a multi-J anlaysis of HCN and HCO+ emission at selected sightlines across the Antennae using SMA data (PI project SMA 2018B-S022).


Page Last Updated on January 20, 2021