Part I: Preliminary Information
Title: Developing an Atlas of Starburst Galaxy Emission Lines
Abstract:
Simulations have become a popular tool for the investigation of complex astrophysical systems
thanks to enhancements in computational technologies and capabilities. By comparing
simulation results with observations, we may further tune such simulations to realistically model
and understand various galactic systems. This project seeks to utilize such simulations to better
understand galaxy evolution. Specifically, I will investigate galaxies undergoing high rates of
star formation and their surrounding clouds to better understand the effects that various
parameters have on the light emitted by these star-forming galaxies. Throughout this research, I
will carry out numerous simulations of star-forming galaxies to compile into an atlas of
information and results. Such knowledge about distant galactic processes helps guide our
understanding of our own galaxy by both allowing us to adopt an outsider perspective and
helping us explore processes similar to those of our own galaxy but under extreme conditions.
Personal Statement:
I was gifted F. Scott Fitzgerald’s wittily philosophical novel This Side of Paradise in high
school. The novel follows the protagonist Amory Blaine’s life from school to war, as he matures
from a “romantic egotist”1 to an “educated personage.”2 The complete disorder prevalent
throughout his life makes Amory question everything, until he is sure of only himself.
Ultimately, Amory cries out, “I know myself, but that is all-”3 I quickly became fascinated with
1
F. Scott Fitzgerald, This Side of Paradise (New York: Barnes & Noble Books 2005), 4.
Ibid., 236.
3 Ibid., 261.
2
this last line of Fitzgerald’s novel. Amory’s understanding of himself was inspirational to me, a
stereotypically uncertain high school student. I wanted to know myself as well as Amory knew
himself; however, as I reflected on my own life, there was little consistency and even less
certainty.
Growing up, I was interested in everything. I thought science was fascinating, but
enjoyed reading and debating. I was part of chess team and book club and played in the
orchestra. Later in high school, I attended the North Carolina Governor’s School summer
program for French and was enrolled in the North Carolina School of Math and Science online
program. As expected, I was also being told to apply to colleges and pick a major. The former
was not too difficult a task but the latter left me conflicted; I was interested in too many things.
In a vague sense, I knew I wanted to engage in science on a daily basis but simultaneously
ponder philosophical questions. This apparent dichotomy of interests left me in a frenzied state
of uncertainty very much contrary to Amory’s confidence.
As a first-year Elon student, I had various exceptional experiences. My Honors Fellows
Global Experience made me question the implications of international human rights. A study
abroad program in Istanbul during Winter Term taught me the complexities evoked when
cultures blend. My ethics courses helped me view the aforementioned issues from a moral
standpoint. My introductory physics courses taught me that even scientific knowledge is debated
and constructed. As my interest in epistemology developed even further, I began to see physics
and philosophy as inseparable. For me, they both approach similar questions about the universe,
about what we know and what we can know.
In a romantic, Fitzgerald-esque sort of way, I have come to characterize myself as a
student of physics and courter of philosophy. Over the summer of 2013, I completed a
computational astrophysics research experience at North Carolina State University. I simulated
incredibly complex stellar systems on super-computers. The experience inspired me to explore
astrophysics research using simulations, as I realized that modeling real-life systems has great
philosophical undertones as well. After all, Plato’s classic Allegory of the Cave is the
philosophical epitome of a simulation.
With my research at Elon, I hope to continue to be a student of physics, but maintain my
interest in the bigger questions of philosophy. The Lumen prize will provide me the unique
opportunity to have experiences that will enrich my research, whether by attending national
conferences that engage me with scholars in the field or by participating in workshops that help
me understand the questions and methods used in the field. The experience granted to me by the
Lumen prize will benefit my graduate studies, as I will already have developed some research
skills and have become part of the scholarly community. Finally, I hope the experience of the
Lumen program will enable me to become an Amory-like educated personage.
Part II: Project Description
Focus:
Simulations that imitate real-world situations have been a scholarly investigative tool for
centuries. With our improved knowledge of physics and enhanced computational technologies,
nowadays we can write computer simulation codes modeling systems from nanoparticles to
galaxies. By providing a few observational inputs, such simulations model complex relationships
that cannot be measured directly. This project proposes to create an atlas of information by
addressing the following question: How can we match the observed emitted light of starburst
galaxies by altering various parameters within simulations? Simulations of starbursts and other
galaxies in general can help us in two different ways: First, they allow us to approach our own
galaxy from an outsider perspective. Similar to studying cultures, one may develop a greater
understanding of one’s own culture by studying others. Second, we are able to model extreme
conditions to better understand the mechanisms that cause them, as well as their effects. While
these extreme conditions are not present within our own galaxy, such simulations can improve
our understanding of processes happening within our own galaxy. This study builds off previous
scholarly research; however, its comprehensive nature distinguishes it from similar past studies
and will consequently enable us to have a broader perspective and understanding overall.
Background Information
Star-forming galaxies that demonstrate an exceptionally high rate of star formation,
known as starburst galaxies, have played a crucial role in the study of the evolution of galaxies.
Within starburst galaxies lie recently formed, hot, massive stars that emit large amounts of light
(Calzetti 1996). Since these hot, massive stars quickly consume the gas reservoir of the galaxy,
the starburst must only be a phase in the evolution of galaxies. Thus, by studying the starburst
phase, a better understanding of the evolution of galaxies as a whole will be established (Calzetti
et al. 1996, Kewley et al. 2001).
To study galaxy evolution, measurements of the energy released are crucial. This energy,
known as the emitted radiation, interacts with clouds of gas that surround the stars. While the
surrounding clouds absorb some of the energy, some of it is re-emitted instead, creating emission
lines. The characteristic spectrum of light that the clouds emit, known as their emission-line
spectrum, is an important diagnostic. It allows for deeper investigation of starburst galaxies and
depends on the incoming radiation and the properties of the cloud itself (Osterbrock and Ferland
2006). Through observations and simulations of the emission lines coming from the clouds that
surround starburst galaxies, insight may be gained into the processes and characteristics of these
massive star-forming regions. This insight may be applied to understanding characteristics of our
own galaxy.
Like starburst galaxies, the clouds surrounding other extragalactic objects emit
characteristic spectra. Various extragalactic emission-line objects in different stages of galactic
evolution can be classified by analyzing these spectra (Baldwin, Phillips & Terlevich 1981).
Once classified, the spectral strengths can be analyzed to estimate many physical parameters. For
example, astronomers study the rate of star formation within these galaxies, the various
characteristics of their emitted radiation, and the elemental composition of the surrounding gas
clouds.
Several methods for modeling these cloud systems exist. Levesque et al. (2010) studied
the effects of changing certain parameters of the star-forming region on the emitted spectrum.
While their study helped us in understanding some of the intricacies of these regions, it was not
completely observationally consistent. They assumed the surrounding cloud to be a single,
constant pressure mass subjected to radiation from hot, newly formed stars. Observations
confirm that many clouds are often present with a variety of densities (Osterbrock and Ferland
2006) that Levesque et al. (2010) did not account for.
Instead of assuming constant parameters for cloud system simulations, Korista et al.
(1997) created an atlas of simulations by testing a range of input parameters. They considered
various column densities (amount of atoms in a given cylinder spanning the area being studied),
gas densities, and chemical compositions of the cloud. However, instead of using starburst
galaxies as a method for investigation, Korista et al. (1997) use quasars, highly energetic
galaxies with strongly emitting regions around a central supermassive black hole. Though their
study provides insight into the cloud system processes, the emitted radiation of quasars and their
cloud properties are different than those of starburst galaxies.
Proposed Research
My study will use the unique parameters proposed by Korista et al. (1997) for quasars but
adapt them to starburst galaxies to address the following questions:
1. What are specific cloud parameters that influence the strength of emission lines in
starburst galaxies?
2. How can these parameters be tuned in simulations to match observations?
3. How do these parameters guide overall understanding of galaxy evolution?
In the first stage of my project, I will carry out hundreds of simulations of starburst
galaxies using two computational codes—Starburst99 and Cloudy—varying different model
parameters to create a large data set of emission line plots. The vast amount of data will be stored
on an external storage unit.
In the second stage of the project, I will analyze these simulations and compare them to
observations. To do so, I will use different spatial distribution functions and select the one that
best describes recent observational data by Allen et al. (2013). Previous theorists have suggested
a power law distribution (Ferguson et al. 1997, Richardson et al. 2014) or a fractal cloud
distribution (Bottoroff and Ferland 2001). Others have suggested a Gaussian (normal)
distribution due to its prominence throughout nature. In this project, I will try these suggested
distributions and others that may be appropriate. By comparing theory and simulations to
observations, I can select the most realistic distribution. This comparison will allow me to
constrain which spatial distribution functions truly depict the physical picture present in starburst
galaxies.
The data generated throughout this project and its necessary accompanying information
will be both posted online and published in a peer-reviewed journal for scholars to view and use.
Overall, the two stages of the project together will further the astronomical community’s
understanding of the processes and parameters that create the observed emission line spectrum.
Proposed experiences:
I began researching in the fall of 2013 by examining various example problems during
weekly meetings with Dr. Richardson to become better acquainted with the software commonly
used in the field of nebular astrophysics. We continued meeting throughout winter and spring
2014. I will run many of the models necessary to compile the atlas this summer through the
Summer Undergraduate Research Experience program at Elon to which I have been accepted.
This summer I also hope to attend the Educational Research in Radio Astronomy program at the
National Radio Astronomy Observatory to which I have applied. This program will allow me to
explore and gain valuable experience with observational astronomy. Support through the Lumen
prize will also enable me to attend Dr. Gary Ferland’s weeklong Cloudy summer school in
Ireland to which I have been accepted. Dr. Ferland is the creator of Cloudy, a large-scale spectral
synthesis code designed to simulate interstellar matter that I will be using for my research. His
workshop will incorporate textbook study and group research projects that will further develop
my skills with Cloudy.
Throughout the following two years, I will also be completing two research hours each
semester of Honors 498 research with Dr. Richardson. This will allow me to continue my
research, completing the compiled atlas by the end of fall 2014 and drafting a paper explaining
the results in the fall as well. I will submit the paper to the Astrophysical Journal Supplement
Series for publication in spring 2015. I will also begin work on the numerical analysis of the
results in spring 2015, continuing into the fall 2015 as necessary. Finally, I will compile all
results into a completed Honors Thesis.
In summer 2015, I will complete a Research Experience for Undergraduates. Stepping
back from my project to look at another will allow me to explore other potential fields of interest
and research for a short period of time that will enrich my overall skills as a physicist. I will
attend two American Astronomical Society meetings in January of 2015 and 2016, planning to
present a poster at the former and give an oral presentation at the latter. I also plan to present my
results at the National Conference for Undergraduate Research and Elon University’s Spring
Undergraduate Research Forum in 2015 and 2016.
Proposed products:
I will create the following specific products with this project:
1. A final paper in which my findings will be reported with the intention to submit to
the Astrophysical Journal Supplement Series.
2. An atlas of starburst emission lines with methods and data posted online to be
freely and easily available for interested scholars.
3. Several posters and oral talks for presentation at Elon’s Summer Undergraduate
Research Experience symposium, Elon’s Spring Undergraduate Research Forum,
the National Conference of Undergraduate Research, and two American
Astronomical Society meetings.
4. A compiled Honors Thesis detailing my experience with the project.
Part III: Feasibility
Feasibility statement:
An explanation of the project’s feasibility can be broken into two parts: my existing
experience with the methodology/topic and the feasibility of the research itself.
My education in simulating physics began by learning Visual Python from Dr. Kyle
Altmann. Visual Python is a computational tool used in introductory physics courses to aid in the
calculation and visualization of complex systems. My interest in physics simulations evolved to
encompass galactic simulations when I completed a Research Experience for Undergraduates at
North Carolina State University in computational astrophysics. These REU programs introduce
students to a topic and help them conduct research under a mentor at the host university for a
brief period during the summer. Although I was presented with a topic of which I had limited
knowledge, I gained valuable research skills throughout the summer and was able to present my
results at a final undergraduate research symposium. I learned different programming languages
and computer systems that are similar to those I will be using in this project. I gained more
experience with science communication when I gave a brief talk about my topic to the general
public at the North Carolina Science Museum in Raleigh. I presented my research at this past
winter’s American Astronomical Society’s meeting in Washington, D.C. Furthermore, studies at
Elon have helped me gain a better understanding of my research topic overall. In the fall of 2013,
I took Dr. Crider’s Modern Astrophysics I course. In spring 2015, I hope to take Modern
Astrophysics II. These experiences, in and out of class, developed my research and
communication skills and gave me a comprehensive understanding of the topics.
In preparation for this research, I have been expanding my understanding of the software
necessary for the research. I will be using Starburst99 and Cloudy, both simulation codes used
by many scholars in the field. The coupling of spectral evolution codes (like Starburst99) with
photoionization codes (like Cloudy) is common in the field (Kewley et al. 2013, Moy et al.
2001). Starburst99 is a star-forming galaxy simulation code that is available online and requires a
few simple input parameters to run (Leitherer & Vazquez 2005). Using this code will enable me
to study many different star-forming galaxies. Cloudy is a complex open source code (free and
open to edit) that hundreds of scholars use per year. It simulates a broad-range of conditions in
interstellar matter and predicts the resultant spectra (Ferland et al. 2013).
Throughout the past semester, I have been working with Cloudy and have already run a
few simulations on Starburst99 as well. Preliminary results of these codes look promising.
Though the codes have posed no problem thus far, individually or coupled, should any problems
arise, both codes have networks of support. Starburst99 and Cloudy both have online
documentation. Furthermore, Cloudy has a message board with an extensive network of scholars
who can provide me with advice. Because both codes are freely available, the cost of the
software is conveniently not a consideration for this project. Cloudy may prove computationally
expensive, prompting a need for off-campus supercomputers to which I already have access.
Thus, due to my past experiences and the nature of the research, this project is entirely feasible.
Budget:

Conferences- $4,000
o AAS Winter 2015- Seattle, Washington ($1,265)

Travel by plane ($500)

Conferences Fees ($165)

Lodging ($500)

Food- $25 per day ($100)
o AAS Winter 2016- Kissimmee, Florida ($1,165)

Travel by plane ($400)

Conferences Fees ($165)

Lodging ($500)

Food- $25 per day ($100)
o NCUR 2015- Cheney, Washington ($835)

Travel by plane ($300)

Conferences Fees ($185)

Lodging ($250)

Food- $25 per day ($100)
o NCUR 2016- Asheville, NC ($735)


Travel by car ($200)

Conferences Fees ($185)

Lodging ($250)

Food- $25 per day ($100)
Experiences- $3,500
o Cloudy Summer School- Belfast, Ireland ($2,750)

Travel ($2,000)

Lodging ($350)

Food ($300)

Other Expenses ($100)
o Educational Research in Radio Astronomy (ERIRA)- Green Bank, WV ($750)


Travel- by car ($250)

Lodging ($300)

Food ($200)
Research Materials- $4,500
o Computer- Macbook Pro ($3,500)
o Data Storage (5 TB External Hard Drive) ($500)
o Books- $500
Physics of Fully Ionized Gases (Lyman Spitzer); Physical Processes in the
Interstellar Medium (Lyman Spitzer); Physics of the Interstellar and
Intergalactic Medium (Bruce T. Draine); The Physics and Chemistry of
the Interstellar Medium (A. Tielens); An Introduction to Active Galactic
Nuclei (Bradley M. Peterson); Foundations of Astrophysics (Barbara
Ryden and Bradley M. Peterson); Radiative Processes in Astrophysics
(George B. Rybicki and Alan P. Lightman); Astrophysics Of Gaseous
Nebulae And Active Galactic Nuclei (Donald E. Osterbrock and Gary J.
Ferland)

Publication in Astrophysical Journal Supplement Series- Page Charges- $2,750
o 25 pages @ $110 per page for ApJS

Other unforeseen expenses – $250
Total: $15,000
Timeline:
Proposed Experiences
Summer 2014
SURE
Proposed Product(s)
Elaboration of methodology
Written research overview (similar
to a literature review) and
methodology
Creation of atlas
Compiled initial atlas
Final poster presentation
Potentially attend Educational
Research in Radio Astronomy
summer workshop at National
Radio Astronomy Observatory
Gain experience with observational
astronomy
Attend Cloudy workshop
Portfolio of potential example
problems simulation can solve
Networking with other researchers
Fall 2014
Two 498 research credit hours
with Dr. Richardson
Finalize atlas
Analyze atlas
Rough draft of atlas paper
Submit abstract for Winter AAS
and Spring NCUR conferences
Winter 2015
Attend AAS conference
Spring 2015
Two 498 research credit hours
with Dr. Richardson
Finalize paper
Begin numerical analysis of
results
Attend SURF/NCUR conference
Potential poster presentation
Submit final paper to Astrophysical
Journal Supplements
Completed atlas (post data online)
Potential oral presentation(s)
Potentially enroll in Dr.
Richardson’s “Modern
Astrophysics II” course
Summer 2015
Participate in research experience
for undergraduates (REU) at
another institution
Fall 2015
Two 498 research credit hours
with Dr. Richardson
Gain experience in other topics and
methods within astronomy
Continue numerical analysis of
results
Begin working on compiling
Honors Thesis
Winter 2016
Attend AAS conference
Spring 2016
Two 498 research credit hours
with Dr. Richardson
Potential oral presentation
Finalize numerical analysis
Attend SURF/NCUR conference
Potential oral presentation(s)
Defend Honors Thesis
Finalized Honors Thesis
List of sources:
Allen J., Hewett C., Richardson C. T., Ferland G. J., & Baldwin J. A., 2013, MNRAS, 430, 3510
Baldwin J.A., Phillips M.M., Telervich R., 1981, PASP, 93, 5
Bottorff, M. & Ferland, G. J., 2001, ApJ 549, 118
Calzetti D., 1996, AJ, 113, 162
Ferguson J. W., Korista K. T., Baldwin J. A. & Ferland G. J., 1997, ApJ, 487, 122
Ferland et al., 2013 RevMexAA 49, 137
Kewley L.J., Dopita M. A., Sutherland R.S., Heisler C.A., & Trevena J., 2001, ApJ, 556, 121
Kewley, L.J. & Ellison, S. L., 2013, ApJ, 681, 1183
Korista K., Baldwin J., Ferland G.J., & Verner D., 1997 ApJS, 108, 401
Levesque E., Kewley L., & Larson K., 2010 ApJ 139, 712
Osterbrock, D. & Ferland, G.J., 2006, Astrophysics of Gaseous Nebulae and Active Galactic
Nuclei, (2nd ed.; Sausalito, California: University Science Books)
Richardson, C.T., Allen, J.T., Baldwin, J.A., Hewett, P.C., & Ferland, G.J., 2014, MNRAS
Vazquez, G. A. & Leitherer, C., 2005, ApJ, 621, 695