My thesis investigates the connections between star formation feedback and gas kinematics over a range of physical and star formation rate scales. My thesis advisor is Prof. Alberto Bolatto.

The first chapter of my thesis is related to the kinematics of extraplanar diffuse ionized gas (eDIG) in nearby, normally star-forming galaxies from the EDGE and CALIFA surveys. In my first paper, I derive molecular and ionized gas rotation curves for a sample of intermediate inclination galaxies. I find that the ionized gas rotates systematically slower than the molecular gas in the majority of these systems. We attribute this difference in rotation velocity to the presence of eDIG, which rotates more slowly with increasing height above the galaxy midplane. Viewed at an intermediate inclination, this effect leads to the systematically lower ionzied gas rotation velocities.

In order to measure eDIG properties directly, my second paper analyzes the ionized gas scale height, vertical gradient in the rotation velocity, and ionization properties of eDIG in a sample of edge-on CALIFA galaxies. We again find evidence for eDIG in the majority of galaxies studied, indicating the pervasive nature of this phase in nearby star-forming galaxies. This WIM-like phase is an important component to these galaxies, and the ionization of the eDIG is consistent with ionization from star formation activity in the midplane. Therefore, star formation feedback plays a role even in normally star-forming galaxies.

The second chapter of my thesis focuses on super star clusters (SSCs) in the central starburst of NGC253. High resolution ALMA data reveal dusty, compact, massive stellar clusters potentially powering the starburst-driven outflow (Leroy et al. 2018). Using even higher resolution ALMA data (30 mas = 0.5 pc), we find evidence for outflows from some of these SSCs. My third paper will focus on the properties of these outflows (such as the outflow velocity, mass, and energy injection) as well as modeling to constrain the outflow opening angles and inclinations. My fourth paper will study the continuum properties of these SSCs to constrain the cluster mass function.

In the final chapter of my thesis, I will study the kinematics of the galaxy-scale outflow in the prototypical starbust galaxy M82. I am the PI of cycle 7 SOFIA observations of the [CII]158μm line in the disk and outflow of M82. These spatially- and velocity-resolved measurements will allow for [CII] to be measured in the outflow of M82 for the first time. It is expected that the outflow should transition from molecular to atomic gas, and these data will probe this transition region. Moreover, the atomic gas in the outflow decelerates (Martini et al. 2018) whereas there is no such deceleration seen in the molecular gas (Leroy et al. 2015). These velocity resolved [CII] measurements (which are only possible with upGREAT on SOFIA) will determine whether the [CII] decelerates or not.

Star Formation Feedback Processes

A schematic of various star formation feedback processes as a function of physical scale and star formation rate. My thesis focuses on the feedback mechanisms highlighted in green.

Molecular and Ionized Gas Kinematics in Nearby Galaxies

Left: Molecular gas (blue) rotates systematically faster than the ionized gas (red) in the majority of intermediate inclination galaxies from the EDGE-CALIFA Survey (Levy et al. 2018). Right: The ionized gas rotation velocity decreases with distance from the galaxy midplane in a majority of the edge-on galaxies studied (Levy et al. 2019).

The Nearby Starburst Galaxy NGC 253

The 350 GHz dust continuum map covering the central 10" x 10" (170 pc x 170 pc) of NGC 253. The beam FWHM is shown in the upper left corner. Despite the increased resolution most of the massive clusters identified by Leroy et al. 2018 persist, sometimes with a few lower-mass companion objects. The insets show the CS 7-6 spectra towards three SSCs, highlighting the characteristic P-Cygni profiles indicative of outflows. These are the only clusters toward which we unequivocally identify blue-shifted absorption signaling outflow activity. (Levy et al. 2020, in prep.)


First-Authored Publications:
28 first-author citations — h-index=2
The EDGE-CALIFA Survey: Evidence for Pervasive Extraplanar Diffuse Ionized Gas in Nearby Edge-On Galaxies
Levy et al. 2019, ApJ, 882, 84
The EDGE-CALIFA Survey: Molecular and Ionized Gas Kinematics in Nearby Galaxies
Levy et al. 2018, ApJ, 860, 92
Co-Authored Publications:
252 total citations — h-index=8
Super Star Clusters in the Central Starburst of NGC 4945
Emig et al. 2020, ApJ accepted
The Turbulent Gas Structure in the Centers of NGC 253 and the Milky Way
Kreiger et al. 2020, ApJ
The Molecular ISM in the Super Star Clusters of the Starburst NGC 253
Kreiger et al. 2020, ApJ
The EDGE-CALIFA Survey: Using Optical Extinction to Probe the Spatially-Resolved Distribution of Gas in Nearby Galaxies
Barrera-Ballesteros et al. 2020, MNRAS
The Molecular Outflow in NGC 253 at a Resolution of Two Parsecs
Krieger et al. 2019, ApJ
Forming Super Star Clusters in the Central Starburst of NGC 253
Leroy et al. 2018, ApJ
The EDGE-CALIFA Survey: Validating Stellar Dynamical Mass Models with CO Kinematics
Leung et al. 2018, MNRAS
The EDGE-CALIFA Survey: The Influence of Galactic Rotation on the Molecular Depletion Time across the Hubble Sequence
Colombo et al. 2017, MNRAS
The EDGE-CALIFA Survey: Variations in the Molecular Gas Depletion Time in Local Galaxies
Utomo et al. 2017, ApJ
The EDGE-CALIFA Survey: Interferometric Observations of 126 Galaxies with CARMA
Bolatto et al. 2017, ApJ
Dense Molecular Gas Tracers in the Outflow of the Starburst Galaxy NGC 253
Walter et al. 2017, ApJ
October 2019 Probing Feedback from Super Star Clusters in the Central Starburst of NGC253
ALMA 2019: Science Results and Cross-Facility Synergies Cagliari, Italy
October 2019 The WIM in Other Galaxies
Invited Review Talk
The Warm Ionized Medium (WIM) Workshop Green Bank, WV
June 2019 Probing Feedback from Super Star Clusters in the Central Starburst of NGC253
Radio/Millimeter Astrophysical Frontiers in the Next Decade Charlottesville, VA
November 2018 Connecting Stellar Feedback and Gas Kinematics in Nearby Star-Forming Galaxies
Lunch talk at Goddard Space Flight Center Greenbelt, MD
September 2018 Connecting Star Formation Feedback and Gas Kinematics on Different Scales
Lunch talk at the National Science Foundation Alexandria, VA
June 2018 Connecting Molecular and Ionized Gas Kinematics to Extraplanar Diffuse Ionized Gas with the EDGE-CALIFA Survey
Astrophysical Frontiers in the Next Decade and Beyond Portland, OR
January 2018 The EDGE-CALIFA Survey: Molecular and Ionized Gas Kinematics in Nearby Galaxies
The 231st Meeting of the AAS Washington, DC
October 2017 The EDGE-CALIFA Survey: Molecular and Ionized Gas Kinematics in Nearby Galaxies
The Role of Gas in Galaxy Dynamics Valetta, Malta
September 2016 The EDGE CO Survey of Nearby Galaxies
Half a Decade of ALMA: Cosmic Dawns Transformed Palm Springs, CA
April 2016 Velocity Field Structure in the EDGE Galaxies
Molecular Gas in Galactic Environments Charlottesville, VA
January 2015 Tracing the Dense Molecular Gas in the Large Magellanic Cloud
The 225th Meeting of the AAS Seattle, WA

Mentoring, Teaching, Service, & Outreach

Students Mentored:

Lauren Cooke May 2020

Summer 2019
Senior at Washington, DC area high school
Now: Undergraduate at Harvard University
Brandon Davey January 2020 — GRAD-MAP Winter Workshop Undergraduate at the University of South Florida
Nathnael Feleke Summer 2019 — GRAD-MAP Summer Scholars (co-mentor)

January 2019 — GRAD-MAP Winter Workshop
Undergraduate at Montgomery College - Takoma Park
Now: Undergraduate at Florida Institute of Technology
Aurora Cid January 2018 — GRAD-MAP Winter Workshop Undergraduate at CUNY College of Staten Island
Natalia Ramírez Vega January 2017 — GRAD-MAP Winter Workshop Undergraduate at the University of Costa Rica & Fidélitas University


Spring 2020 ASTR 121: Introductory Astrophysics II - Stars and Beyond Teaching and Lab Assistant
Fall 2019 ASTR 120: Introductory Astrophysics - Solar System Teaching Assistant
Spring 2014 PHYS 141: Introductory Mechanics Preceptor
Spring 2013 MATH 100, 100AX: Prep for College Algebra Undergraduate Teaching Coordinator
Fall 2012 MATH 100, 100AX: Prep for College Algebra Undergraduate Teaching Coordinator
Spring 2012 MATH 100, 100AX: Prep for College Algebra Lead Undergraduate Teaching Assistant
Fall 2011 MATH 100, 100AX: Prep for College Algebra Undergraduate Teaching Assistant


January 2020 - presentReferee for MNRAS
Spring 2020UMD Astronomy Department Faculty Search Committee member
2019Scientific Organizing Committee member for the Warm Ionized Medium Workshop
March 2017 - August 2020Class-year representative on the UMD Astronomy Department's Graduate Student Council


I am involved with GRAD-MAP (Graduate Resources Advancing Diversity with Maryland Astronomy and Physics), which pairs undergraduates from historically black colleges and universities, minority serving institutions, and community colleges primarily from the mid-Atlantic region with a mentor in either the UMD astronomy or physics departments. During the winter break, these students attend a ten-day Winter Workshop, where they learn Python, work on a research project with their mentor(s), and learn information and resources to help them apply for graduate school. For the past four years, I have served as a research mentor for a student. For the past three years, I developed the student's project independently and also assisted with some of the professional development during the Winter Workshop. In the summer of 2019, I was a co-mentor for a student in GRAD-MAP's ten-week Summer Scholars program.

Prior to coming the the University of Maryland, I worked in education and public outreach at the National Optical Astronomy Observatory (NOAO) in Tucson, AZ as the lead student for two years. I ran programs for schools and classrooms, developed activities and materials, organized teacher workshops, published a monthly newsletter, wrote and recorded a bi-monthly podcast, coordinated the translation of materials, and ran a social media site. I was also one of the key developers for the UNESCO International Year of Light 2015 Quality Lighting Teaching Kit, which has been distributed to partner organizations worldwide. I was also a character in two installments of NOAO's comic strip "Tales of the Modern Astronomer", which have been featured at AAS conferences (see the photo in this section) and on the covers of past NOAO Newsletters (which you can find here and here)!

Nathnael Feleke—our 2019 GRAD-MAP Summer Scholar—posing in front of his poster with two of his project mentors (Stuart Vogel and R.C.L.).

The 2019 GRAD-MAP Winter Workshop cohort and volunteers in front of the Green Bank Telescope. (Photo by Peter Teuben)

Posing in front of my comic book character at the NOAO booth at the 2015 winter AAS meeting.

Helping out at the NOAO booth during the Tucson Festival of Books, and posing with my storybook likeness.


Department of Astronomy
University of Maryland
1113 PSC Bldg. 415
College Park, MD 20742

Office: ATL 1227