Faculty Spotlight: Jessica Werk

Jessica Werk recently joined the UW Astronomy Department as an Assistant Professor, and is the new faculty advisor to undergraduate students. She grew up in Simsbury, a suburb of Hartford, CT. Her research aims to unravel the mysteries of the circumgalactic medium and the role it plays in galaxy formation and evolution. In her own words:

Jessica-Werk“I am currently building a research group of graduate and undergraduate students focused on the broad topics of galaxy formation and evolution. Specifically, my work addresses the physics of and interplay between the interstellar, circumgalactic, and intergalactic media — all the stuff between the stars and galaxies, which is, as it turns out, the vast majority of the stuff in the universe. I follow the gas using both multi-wavelength observations in space and from the ground,  and by considering a range of cosmological simulations. I love working with, teaching, and advising students, and consider it to be the best part of my job.”

Q & A

What got you into astronomy?

When I went away to college, I left behind my TI-83 calculator thinking I was done with math and science forever. I had thought I wanted to double major in international politics and economics and I was going to learn to speak at least 3 additional languages. But that was before I had ever really pondered a vast universe beyond our relatively minuscule planet, and, before I enrolled in Astronomy 155 – an introduction to astronomy course – taught by Professor Kathryn Johnston then at Wesleyan University. The first day of class I learned that photons from the sun take approximately 8 and half  minutes to arrive at earth, and that fact just hit me hard like a punch to the gut. I thought: I need to understand this incredibly vast universe. My first course in astronomy changed my goals and outlook tremendously, in a large part due to the encouragement and enthusiasm of Professor Johnston. After she gave me the opportunity to carry out research modeling stellar tidal streams in a growing gravitational potential over the summer of my freshman year, I was truly hooked. Later, when I packed for my Sophomore year, the TI-83 came with me and my goal was to become an astronomer.

What advice do you have for post-docs / grads / undergrads that you wish someone had told you earlier in your career?

Good advice is the type that reaches you at exactly the right moment when you need to hear it. So, instead of offering general advice, I’ll share a piece of career advice that resonated with me at precisely the right moment. During my first postdoc, I was feeling a bit untethered and generally pessimistic about my future as an astronomer. (I’ve since come to realize this is common experience, especially for first postdocs.) I had even been exploring other career options, having recently interviewed at a management consulting firm — which was itself a near soul-crushing experience. At this particular moment, I was having lunch at an international astronomy conference with a very prominent astronomer, Joss Bland-Hawthorn. I may have mentioned my lurking feeling of career disillusionment, although I can’t recall the specifics of the conversation. However, I vividly recall his response. He looked at me very seriously and said, “Don’t give up. Just do not give up.” That was exactly what I needed to hear at that moment. There were many times after that conversation that I wanted to give up and leave the field in defeat, but those words haunted me. As simple as his advice was, it gave me that little bit of extra strength I needed to continue to face the rejection after rejection that comes with continuously applying for fellowships, jobs and grants.

That said, for many astronomers, leaving the field is the right choice. There are more lucrative and potentially rewarding options for someone with analytical, teaching and coding skills. I know astronomers who have left the field because they realized they would be happier doing something else, not because they gave up. If you’re contemplating a career in astronomy, it is important to be honest with yourself about whether your heart is in the research.  You should reassess your goals at every stage.  It was this process of continual self-evaluation that led me to realize that I have to do astronomy research, that I really do love it, and that most of my doubts involved a fear of rejection and failure at some level. Rejection is difficult, but it gets easier and you get stronger the more you face it. Failure is entirely a figment of your imagination.

What is your favourite aspect about Seattle?

The stunning, dog-friendly and incredibly maintained city parks are my favorite aspect of Seattle so far. Between Magnuson, Discovery, and Carkeek parks, it is very difficult to choose a favorite. My dog Marlowe’s favorite is Magnuson Park for its huge off-leash area and dog beach. On the human beach at Magnuson, I enjoyed swimming this summer while marveling at the Cascades in the distance. Just last weekend at Carkeek park, I watched salmon run up the creek, and when I was down on the beach saw a salmon jump out of the water several times. Oh, and I almost forgot to mention the exhilarating feeling of standing on the bridge just above an oncoming freight train. I consider Carkeek Park to be my happy place in Seattle, since I live very close by. Discovery park is just a true gem, with amazing views and large open fields.

Research Spotlight: N-body Shop Simulates the Universe

They say that the best simulation is the one you never have to run. We respectfully disagree. We prefer the simulation you only have to run once*. This is how George Lake did it, it’s how the N-Body Shop does it, and it has worked out pretty well so far. We present to you the newest in the N-Body Shop large scale cosmological simulations. Ladies and gentlemen, for your consideration ROMULUS25!

Why we need cosmological simulations

Running an astrophysical “experiment” is hard. We cannot travel a hundred million light years to a distant galaxy and study its evolution over the course of billion of years. However, N-Body simulations are a way to perform experiments to understand how galaxies form and evolve using a supercomputer. Specialized parallel software models a large region of the universe as a collection of billions of mass elements, integrates the relevant equations that model… the expansion of the Universe, gravity, electromagnetic and hydrodynamic forces, dark matter, cosmology, star formation, supernovae explosions, and the formation and growth of supermassive black holes (rocket science? That is easy). The outcome is a series of detailed snapshots of the state of that region of the Universe, described by the position, velocity and thermodynamical properties of each mass element. Scientists can then identify “galaxies” within the simulations as a specific collection of mass elements and study their evolution in time.

romulus25_3panel
A color density slice of Romulus25 at z=0.4, centered on a group of galaxies with total mass 10 times the size of our own Milky Way. Left: The underlying DM distribution. Center: the distribution of stars, color coded with their metallicity (red: metal poor, red: metal rich). Right: the distribution of stars, color coded with their age. Red: old, Blue: young. Most stars are older than 1 Gyr as star formation is “quenched” in the dense group environment. The White dots mark Black Holes.

What is ROMULUS25?

A new, state of the art cosmological simulation encompassing over 15,000 cubic Megaparsecs (Mpc) that is able to resolve the internal structure of galaxies down to dwarf galaxies and over the entire Hubble time. The simulation includes a novel treatment of Super Massive Black Holes physics and it is being run on the Blue Waters supercomputer, using our Tree+SPH code ChaNGa.

Science Goals

With ROMULUS25, we plan to answer the following questions:

  • How many small galaxies are there? We are quantifying the number evolution of the faint end of the galaxy Luminosity Function at z >5 and its contribution to the reionization of the Universe (Lauren Anderson).
  • Understand the genesis and evolution of empirical scaling relations for galaxy properties (Michael Tremmel in collaboration with Dan Taranu at UWA and the SAMI Galaxy Survey team)
  • Study the co-eval assembly of supermassive black holes and galaxies (Michael Tremmel, Zoe Deford, and Josh Smith in collaboration with Marta Volonteri, IAP Paris)
  • Examine when and in what galaxies do SMBH mergers and dual AGN occur and where these events fit in the bigger picture of galaxy-BH coevolution (Michael Tremmel, Daven Cocroft, and Daniel Simons in collaboration with Marta Volonteri)
  • Where do Supernovae and SMBH winds go? We will measure the amount of elements pushed by SNae and SMBH winds into the CGM as a function of galaxy mass, SMBH activity, and redshift. (Michael Tremmel in collaboration with Prof. Jessica Werk)
  • Which galaxies host Super Massive Black Holes? Predicting the occupation fraction of SMBHs in dwarf galaxies (Michael Tremmel in collaboration with Prof. Marta Volonteri)
  • Disentangle the effects of environment and Black Holes physics on the observed shutting off of star formation in massive galaxies (Michael Tremmel in collaboration with Andrew Pontzen at UCL)
  • Dust attenuation in high redshift galaxies. In particular, Understanding how the relationship between UV and IR emission is different in the Early Universe (Danielle Skinner and Lauren Anderson)

Why another large scale simulation?

Excellent cosmological simulations already exists, like EAGLE and MILLENIUM and they have been instrumental in shaping our knowledge of galaxy formation. While all recent simulations adopt a cosmological model based on a Cold Dark Matter model and an accelerating expansion driven by dark energy, the original advantages that ROMULUS25 brings are multiple:

  • Sub-kpc spatial resolution that allows us to simulate at the same time the evolution of the bulge and disk structure of systems time size of Andromeda and above and the properties of dwarf galaxies as small as the Magellanic Clouds.
  • Two databases (one halo based, in collaboration with Andrew Pontzen, and the other particle based) that allow us to follow a) the evolution and merging history of various galaxies and the b) thermodynamical history of each simulated mass element across cosmic time. This is a unique strength of particle based, SPH tree-codes such as ChaNGa.
  • A novel physical description of SMBH formation, dynamics and accretion that will allows us to, for the first time, realistically capture the merging rate of SMBHs over cosmic time and their frequency as a function of host galaxy properties.
  • Having a detailed knowledge of the spatial distribution, age, and metal content of the stars and neutral hydrogen in each simulated galaxy allows us to create “artificial observations,” which can be used to compare the outcome of the model with the properties of galaxy samples in the real Universe
Interacting z=1 galaxies color map
A color map of interacting galaxies at z=1. Gray maps the dark matter distribution, red and blue old and young stars respectively, while the large green dots mark the position of the active Super Massive Black Holes. One galaxy has had its star formation “quenched,” possibly by a combination of intense feedback from SMBHs and having gas stripped away by its companion, while the one on the right is a disk galaxy that is actively forming stars. The frame is about 100 kpc across. This system eventually results in a BH merger and a quenched galaxy by z = 0.5.

The UW Team

Several people are involved in this project: Michael Tremmel and Lauren Anderson are the grad students currently involved in the project. Prof. Tom Quinn develops and maintains ChaNGa as part of a collaboration with a computational group group at NCSA. Prof. F. Governato is involved in the science planning and analysis. We also have a group of undergraduate students working on the project: Danielle Skinner, Zoe Deford, Josh Smith, Daven Cocroft, and Daniel Simons.

Powers of ten fun facts

  • The database will contain 10,000+ galaxies
  • Romulus25 is being run using up to 100,000+ cores
  • The amount of data created (about 100 time snapshots) will reach 10+ Terabytes and requires a database and an efficient analysis toolset to properly analyze it.
  • To reach redshift zero the simulation will require 100 million CPU hours

The main physics modules in the ROMULUS25 simulation

  • Gravity duh!
  • Gas heating, cooling, metal enrichment and diffusion
  • SN feedback and cosmic UV radiation
  • BH formation, dynamics, accretion, and feedback
  • Gas dynamics resolved down to 30-60pc

Collaborations and Future Work

We have ongoing collaborations with the IAP in Paris (Volonteri), UCL in London UK (Pontzen) and with the SAMI survey in AU (Taranu). But with so much data and a rich science agenda we welcome scientists near and far and especially students interested in applying for grad school at UW to get in touch with us. We work hard to make our group a most effective and welcoming work environment for everybody interested.


A color density map of the DM distribution centered on a group of galaxies in ROMULUS25. The movie shows a large number of subhalos orbiting in the potential of the group, which weights about ten times the one of our own Milky Way. Each of the most massive subhalos hosts a luminous galaxy. The frame is about 2Mpc per side.

A color density map (red: hot, blue: cold) of the gas distribution. Note the galaxy with a bipolar outflow (possibly driven by the central SMBHs and the interaction with the cluster’s hot diffuse gas).

This research has been made possible by two NSF awards, NSF PRAC OCI-1144357 and NSF AST-1311956, with a total time allocation of 200 million CPU hours. NSF

*for now!

Faculty Spotlight: Emily Levesque

Emily Levesque grew up in Taunton, MA and is a new Assistant Professor in the UW Astro department (welcome!). Her research program is focused on stellar astrophysics and using massive stars in particular as cosmological tools. In her own words:

levesque_emily“The light from star-forming galaxies is dominated by their young massive star populations, and transient phenomena draw our attention to the death throes of these same stars, sometimes at really extreme distances. At the same time, massive stars are uniquely available as local laboratories: we can detect the earliest generations of massive stars exploding as long-duration gamma-ray bursts across the visible universe, while also closely examining the physical properties of their evolutionary and chemical twins right in our own cosmic backyard. Right now my research is focused on observing nearby massive stars and stellar populations and using these results to test and improve the same theoretical models of stellar evolution that we then apply to the high-redshift universe.”

Q & A

What got you into astronomy? What’s your first memory associated with astronomy?

My answer to both of these is the same! When I was 2 years old Halley’s Comet was making its most recent fly-by, and my older brother, Ben, had a school assignment that asked him to go out and observe it. The whole family headed out to the backyard, and according to my parents I was completely transfixed. From then on as I got older people would ask me what I wanted to be when I grew up and my answer was always some variation on “an actor or an astronomer”, “a marine biologist or an astronomer”, “a violinist or an astronomer”, and so on. Astronomer is what stuck!

What do you find most challenging and rewarding about being an astronomer?

One challenging aspect of being an astronomer is balancing the core scientific motivations that drive you with some of the more mundane day-to-day tasks that keep everything up and running: arranging work travel, making slides, writing budgets, debugging code. This can actually go either way: sometimes you hate dealing with the little things, and sometimes it’s much easier to cross “book flights for conference” off your to-do list than “formulate five-year research plan for studying Thorne-Zytkow objects”. It’s important to step back periodically and go “hey, I’m doing all of this because I’m studying the evolution of massive stars a billion light years away!”, but you also don’t want to let the big picture overwhelm you and keep you from the little individual steps that drive your day-to-day progress.

For me, the most rewarding aspect of being an astronomer is getting other people excited about science and astronomy. I love giving public talks and answering questions from people who aren’t in the field. Little kids are always a blast, but I really love seeing adults get drawn into the topic. Inevitably someone will say “Oh, I’m sure this is such a silly question, but…”, and then go on to ask something really thought-provoking or fundamental to current astronomy. I like reminding people that “silly” questions are often the starting point for great science, and it’s always fun to ignite some enthusiasm and curiosity in people about astronomy and how our universe works.

What advice do you have for post-docs / grads / undergrads that you wish someone had told you earlier in your career?

I always tell people to build up a team of advisers and mentors rather than just relying on a single person. Sometimes this is just practical; if you have a question and one person is busy or unavailable, someone else can help you. It’s also really helpful to have multiple perspectives, whether you’re talking about research, teaching, or professional development. Getting this kind of varied feedback is really important to growing as a scientist and to developing your own personal perspective on your research and career.

Another piece of advice is to do as much presenting and writing as you can! Building up a good foundation of scientific knowledge is important, but it’s only part of the skill set that you’ll eventually need. Giving a presentation and writing about your research is crucial if you want to be a professional astronomer, and those same skills are also highly transferrable if you want to move into a related field. Since we don’t often teach “how to write a proposal” or “how to give a conference talk” in classes, the only way to get good at these things is to seek out as much practice and feedback as possible.

Share a short, personal story (family, pets, hobby, fav. quote or song or poem or book) – why is this important to you?

I have a pair of photos in my office: on the left is my grandmother graduating with her LPN from nursing school, and on the right is me graduating with an S.B. in physics from MIT. Like all of my grandparents, she had to drop out of school in her early teens to go work in a factory and help support her family. It broke her heart at the time because she loved school. Eventually she and my grandfather both went back and earned their high school diplomas, and she then went on to get a nursing degree, all while raising five kids! Throughout her life she always emphasized the immense value of education; two generations later I was the first person in my family to get a Ph.D. I love having this photo to look at: on my grouchy or tired days it’s pretty motivating (nursing school! with five kids!), and it reminds me that one of my jobs as a professor is to help make this kind of story possible for my own students from all kinds of backgrounds.

In the not-so-distant future, you’re sent to explore and live on a habitable planet in a nearby star system. What 3 items (physical or abstract) would you make sure you bring and why?

Assuming that people are disqualified as “items”, and that whoever/whatever is sending me will throw in the basic survival provisions (food, water, power source, a Hitchhiker’s towel, etc.)…

–My laptop, so that I can take notes on what I see, keep a journal, take a few pictures, and have some basic portable research tools at hand.

–A simple handheld spectrograph. I’m primarily an observer and mostly work with spectroscopic data, so that’s probably the first thing I’d want to point at anything interesting that I might spot!

–My little stuffed frog. He’s a travel good luck charm, and that’s going to be a pretty long trip. Plus those would be some pretty funny photos from a new planet…

What is your favourite aspect about Seattle?

So far, the weather. I’ve only been living here since mid-August and we’ve had crisp sunny fall days pretty much the whole time! It stays like this all year round, right?

Did or do you have a science role model? What makes this individual’s qualities important to you?

Carl Sagan. He was a talented scientist, a wonderful writer, and I think he’s largely responsible for our modern picture of what a successful “science communicator” or “science celebrity” should be. He got an entire generation interested in science and space (I was very nearly named “Sagan”; my parents were both big Cosmos fans), and I think we need a lot more people like him working in today’s media!