The DIRAC Institute in the Department of Astronomy at the University of Washington is seeking applicants with a strong research record in the development of statistical techniques or algorithms for analyzing large astrophysical data sets for two postdoctoral positions.
AstroML: The first position is to help in the development of the second edition of astroML (http://astroml.org) a popular Python-based machine learning package for astrophysics. New components we are incorporating within astroML include methodologies from deep learning and hierarchical bayesian statistics. Special emphasis will be placed on building a broader community and making astroML a sustainable open-source project. The successful candidate will lead these activities, including the application of the new codes to dataset available to UW researchers.
Time Series Data: The second position is to develop new approaches for analyzing astronomical time series data using modern computational frameworks. The goal of this framework will be to enable science with the ZTF and LSST data sets. Promising applicants should possess an interest in time domain science and experience or interest in the use of databases and large scale compute platforms such as Spark, Dask, or similar. Good Python skills, and experience with machine learning libraries, image processing of astronomical images, or astronomical databases are desirable.
The DIRAC Institute is a newly formed center for data intensive astrophysics at the University of Washington. The Institute consists of six faculty and senior fellows, and over 20 postdoctoral researchers and research scientists. It has active research programs in Cosmology, Solar System science, Milky-Way structure, the Variable and Transient universe, andAstronomical Software.
The University of Washington is a partner in the Zwicky Transient Facility (ZTF) project, a new time-domain survey which will begin operations in early 2018. The UW is a founding partner of the LSST project, and leads the construction of its time domain and solar system processing pipelines. Other research activities at UW/DIRAC include topics in extragalactic science, as well as the understanding the structure, formation, and evolution of the Milky Way using large surveys (SDSS, WISE, PanSTARRS PS1, and others).
A Ph.D. degree in astronomy, physics, computer science, or a related subject is required. The initial appointment is for two years, renewable up to three years, and offers competitive salary and benefits. The appointments are available immediately and are expected to start no later than September 2018.
Applicants should submit a curriculum vitae, description of research interests (with links to Github if relevant) and arrange for three letters of reference to be submitted to Nikolina Horvat at email@example.com with subject line “DIRAC postdoc application (your name)”. Applications will be accepted until the positions are filled, to assure full consideration, please send your application by Dec 31st 2017
For detailed information about the benefits available through the University of Washington, including dental, medical and disability insurance, retirement, and childcare centers, see the University of Washington benefits page: https://www.washington.edu/admin/hr/benefits/.
The DIRAC Institute is a community of people with diverse interests and areas of expertise, engaged in the understanding of our universe through the analysis of large and complex data sets. We are an open, ethical, highly engaged and collaborative community based on trust, transparency and mutual respect. We believe in providing a welcoming and inclusive environment, in the importance of quality of life, in embracing diversity, in making a difference and having fun.
When: January 14, 2019 @ 12:30pm
Where: PAB, eScience Data Studio, 6th floor
Maximizing LSST science with probabilistic data products
LSST will produce massive catalogs including detected objects down to unprecedented floors in signal-to-noise ratio, opening the door to a new space of potential discoveries, from illuminating the dark energy accelerating the expansion of the universe to revealing the physical processes underlying transients and variable stars. The anticipated deluge of uncertainty-dominated data, however, demands an unprecedented degree of statistical rigor. Posterior probabilities that quantify complex uncertainties are appropriate successors to the conventional point estimates of physical parameters that suffice for more informative data. In contrast with traditional science analysis pipelines for point estimates and Gaussian errors, inferential infrastructure compatible with probabilistic data products remains underdeveloped. I present mathematically self-consistent techniques for validating, storing, and using such probabilities in the context of photometric redshifts with applications in cosmology. A statistically principled propagation of information will enable us to use every part of the animal and do the best science possible with LSST.
Dr. Melissa L. Graham, LSST Research Scientist and DIRAC Fellow, coauthored paper on a large Hubble survey of supernovae “Delayed Circumstellar Interaction for Type Ia SN 2015cp Revealed by an HST Ultraviolet Imaging Survey”.
The supernova explosions of white dwarf stars are thought to be caused by the influence of a binary companion star. Most evidence points towards a merger with another white dwarf star, but accreting too much mass from a sun-like or red giant star could also cause a supernova. It is very difficult to directly observe the companion star caught in a supernova explosion, but luckily, some companion stars are very messy. Red giants are so big and bright that material blows off their surface and is scattered around the vicinity like litter in the wind. If the fast-moving front of material ejected by a supernova hits this residual gas, it sends a shock through the material that creates luminous ultraviolet emission. This has only been seen a few times before, when the residual gas was very close to the explosion, and it was unknown how often these stellar systems had gas littering their environment, which had been blown out to further distances, and thus gone unnoticed. By patiently waiting, and using HST to take NUV snapshots of the sites of ~70 supernovae at 1-3 years after the explosion, we caught one white dwarf explosion in a stellar system with a litterbug companion star: Supernova 2015cp. Our team used ground- and space-based facilities (including Keck, VLT, VLA, HST, and Swift) to obtain additional data and study SN 2015cp in detail. Our analysis limits the fraction of white dwarf explosions with messy companion stars to be <6%.
December 2018 Newsletter
It is a great pleasure to welcome you to the first DIRAC Institute newsletter. It is hard to believe that the institute is only a year old and how much has happened over the last 12 months.
In January a team of DIRAC scientists made use of the University of Washington’s 3.5m telescope in New Mexico to measure the shape of the interstellar asteroid 1I/‘Oumuamua (the first asteroid or comet we have discovered that originated from another solar system). In May, 450 people packed Kane Hall to hear our inaugural DIRAC Public Lecture by Nobel Laureate Saul Perlmutter, who described how surveys such as the Zwicky Transient Facility and the Large Synoptic Survey Telescope can revolutionize our understanding of the universe. And in just the last few weeks we streamed the detection of over one million new, variable, or moving objects detected by the Zwicky Transient Factory telescope in a single night.
You can read more about these discoveries in the articles below. I hope you will be able to join us for some of the lectures and events that we will be hosting at the DIRAC Institute in 2019.
As we wrap up this year I did want to ask one thing of you. We are starting a new initiative at DIRAC to bring in students from under-represented universities and colleges around the country to spend the summer working with our researchers. In Seattle, and at the University, we are fortunate to live in a dynamic and entrepreneurial community with access to many skilled and talented researchers. We want to share that knowledge with students who do not have access to these resources.
As you consider your charitable donations this year please consider supporting DIRAC by sponsoring one of the our 2019 Summer Fellows.
If you have already made your gift, thank you for your generosity.
December 2018 Newsletter
Researchers from DIRAC and LSST are gearing up for the annual winter American Astronomical Society (AAS) meeting. This year, it will be here in Seattle at the Washington State Convention Center, from January 6-10, 2019. More than 15 talks and posters will be presented by DIRAC scientists. The meeting offers a stunning array of presentations (over 2300!), professional development workshops, and opportunities for networking.
LSST will have a booth in the exhibit hall throughout the week, and will host a Town Hall evening with updates from across the project. Software developers and scientists from UW’s LSST Data Management team will lead two tutorials on the LSST Science Pipelines for colleagues who want to learn the basics of LSST’s software stack. In addition, UW Astronomy department chair Julianne Dalcanton, recipient of the Beatrice M. Tinsley Prize for exceptionally creative or innovative research, will give an invited plenary talk about her use of large surveys to study low-surface-brightness galaxies and to resolve stellar structures and populations in the Milky Way and other galaxies.
December 2018 Newsletter
Eadie’s research falls in the category of astrostatistics, an interdisciplinary field of astronomy and statistics. On the astronomy side, she is interested in properties of the Milky Way Galaxy such as its mass and amount of dark matter, as well as its stellar populations, globular cluster population, and central nuclear star cluster.
Dr Eadie works with Associate Professors and Senior Data Science Fellows Dr. Mario Juric (DIRAC, Department of Astronomy, eScience) and Dr. Tyler McCormick (Department of Statistics, Department of Social Science, CSSS, eScience).
Dr. Eadie is an eScience Institute and DIRAC Postdoctoral Fellow. She joined DIRAC in September 2017 after completing her PhD in Physics & Astronomy at McMaster University in Hamilton, Ontario, Canada. Eadie also has a Masters in Physics, Engineering Physics, & Astronomy from Queen’s University at Kingston, Ontario and a Bachelor of Science in Physics, with a minor in Publishing, from Simon Fraser University in Vancouver, British Columbia. Having grown-up on Vancouver Island, she is very happy to be back in the Pacific Northwest for her postdoctoral fellowship.
On the statistics side, Eadie is interested in Bayesian hierarchical modelling, Markov chain Monte Carlo techniques, and in general, implementing and developing modern statistical methods to and for astronomical problems. Observational data in astronomy is undergoing a big data revolution, and Eadie is interested in harnessing these data sets with the best statistical tools in order to test physical models of the Milky Way. She hopes to learn not only about the Milky Way’s present properties and structure but also its formation history in the context of the larger Local Group of galaxies.
Most recently, Eadie and Juric co-authored a paper about the Milky Way’s mass as estimated from the data acquired by the European Space Agency’s Gaia Satellite. Gaia has collected position and velocity information of over 1 billion stars in the Milky Way Galaxy! Their work has been submitted to the Astrophysical Journal and is currently undergoing peer-review.
Eadie is also passionate about teaching at the post-secondary level, and has two certificates from the McMaster MacPerson Institute for Leadership, Innovation, and Excellence in Teaching. In her first year at the UW, she has been invited to give a number of lectures to undergraduate and graduate students in the Department of Astronomy. Eadie is a strong proponent of active-learning strategies, and recently developed an exercise for students that teaches Bayesian statistics through m&m’s candy. Since implementing the active-learning strategy in class, she and DIRAC’s Associate Director, Dr. Daniela Huppenkothen, along with collaborators McCormick and Dr. Aaron Springford (Weyerhaeuser), have co-authored a paper describing the activity. Their work has been submitted to the Journal of Statistics Education.
Eadie says that the DIRAC and eScience Institutes have been the ideal environments for an early-career academic like herself; “Both DIRAC and eScience have not only helped me strengthen my interdisciplinary skills and technical proficiency, “ Eadie says, “but have also given me the freedom to follow my academic interests, to explore areas of unique research, to develop new collaborations, and to gain experience in post-secondary teaching”. An avid goal-setter, Eadie plans to make the most of her remaining time at the UW (her postdoctoral appointment continues through 2019), and to make progress towards her long-term career aspiration of becoming a tenured-professor in Astrophysics and/or Astrostatistics at a top university in North America.
December 2018 Newsletter
2018 saw the beginning of survey operations for the Zwicky Transient Facility (ZTF). ZTF is characterizing the Northern Hemisphere sky on timescales ranging from minutes to years. ZTF data will identify young supernovae, rare classes of explosive transients, variable stars, and solar system objects.
DIRAC researchers have been deeply involved in developing technical infrastructure for ZTF as well as leading science analyses.
A major achievement of the DIRAC team was deploying the public ZTF alert stream in June. DIRAC researchers Dr. Maria Patterson, Prof. Mario Juric, Prof. Eric Bellm, and Dr. Zach Golkhou adapted open-source tools from the commercial internet industry and applied them to the problem of streaming up to a million alerts each night in near real time to scientists around the world. Each alert provides an updated lightcurve for a time-variable object observed by ZTF, enabling researchers to identify objects of interest and trigger rapid followup observations. A corresponding public alert archive (https://ztf.uw.edu/alerts/public/) enables more leisurely study. The ZTF alert stream prefigures the larger stream expected by LSST, and DIRAC’s data engineering group is building and expanding on the alert stream tools to enable more sophisticated filtering, classification, and analysis.
In his role as ZTF Survey Scientist, Prof. Eric Bellm also spearheaded the development of the ZTF scheduler. This piece of software solves the complex problem of determining how to most effectively order the hundreds of observations ZTF obtains each night to maximize efficiency and scientific output. The ZTF scheduler has pioneered an innovative new scheduling algorithm based on Integer Linear Programming. A paper describing the algorithm as well as the ZTF surveys will soon be submitted to a special issue of the Publications of the Astronomical Society of the Pacific, where it will join other technical papers describing the ZTF camera, data system, alert system, and other components.
DIRAC researchers and students have been pursuing a range of scientific investigations using the ZTF data. A highlight was the discovery of ZTF18abauprj, a young Type Ia supernova in NGC 6279 (Astronomer’s Telegram, No. 11721). Prof. Eric Bellm identified in it the ZTF alert stream while he was observing and was able to immediately obtain a spectrum. Graduate student Joachim Moeyens and Prof. Mario Juric are using ZTF data to test a new algorithm for discovering asteroids. Dr. Jim Davenport is searching for stellar flares in ZTF high-cadence data with undergraduate Courtney Klein and for SETI signatures as well. Prof. Eric Bellm is working with two undergraduates, Priscilla Dohrward and Rebecca Kyerr, to find compact binary candidates in the ZTF data. Dr. Daniela Huppenkothen, Leah Fulmer, and Zach Golkhou are working on large-scale classifications of ZTF objects.
December 2018 Newsletter
The explanation for the mysterious “Boyajian’s Star” has eluded scientists since its discovery in 2015. DIRAC Research Scientist, James Davenport, thinks it may simply be cosmic dust.
DIRAC Researcher and NSF Postdoctoral Fellow, James Davenport, is a coauthor on a recent paper studying “Boyajian’s Star”, aka the Most Mysterious Star in the Universe! KIC 8462852, as the star is officially known, has been observed to undergo dramatic changes in brightness over several days, as well as smaller long-term variations. Both of these forms of variability have been unexplained so far, but this latest paper (including Davenport and UW grad student , Brett Morris) finds that clumpy dust surrounding KIC 8462852 is the most likely explanation.R
December 2018 Newsletter
On October 24, 2017, the first interstellar object, 1I/‘Oumuamua, was discovered by a small telescope in Hawaii. 1I/‘Oumuamua is thought to have originated in another solar system before its journey took it on a brief tour of our own Solar System. As the first interstellar visitor it was given its own special designation, the number 1 for it being the first of its kind and the letter “I” for interstellar. Even the name,’Oumuamua, means “first messenger” in Hawaiian.
The remarkable opportunity that 1I provides is the first direct study of the properties of solar systems beyond that of our own. Asteroids and comets, the by-products of planetary formation, have been studied for centuries in our own Solar System, but we have not yet had the opportunity to make similar observations of asteroids and comets on the outside. Even given the capabilities of modern-day astronomical observatories and satellites we still cannot observe individual objects the size of asteroids around other stars.
When 1l was discovered our research group at DIRAC took on the task of trying to understand as much as possible about it before it left the Solar System. Within days of its discovery, we were given time on the University of Washington’s telescope at Apache Point in Sunspot, New Mexico. We took images of the asteroid as it passed through the desert skies. Right away we went to work analyzing the data. The photometry revealed that 1I had a reddish color, which Lynne Jones, an expert in our group on observations of the Solar System, realized meant that 1I’s surface composition was similar to our Solar Systems asteroids.
Because of bad weather in New Mexico, we only managed to collect a few hours of data; making inferring properties such as the shape and rotation of 1I difficult to calculate. Luckily, we had an expert on statistics and machine learning in our team, Daniela Huppenkothen, who applied sophisticated statistical techniques to tease out the period and amplitude of the variations in brightness of 1I. The results of many analyses by the DIRAC group revealed that 1I was shaped like a skinny potato and probably had some amount of tensile strength holding it together.
Our group’s findings were published in the Astrophysical Journal Letters.
In addition to our observations of 1I, we wanted to know where it might have come from. Together with Drs. Rory Barnes and Tom Quinn, we investigated the evolution of 1I’s galactic orbit before it encountered the Solar System. We started out with the goal of finding out where 1I came from, but further investigation showed that finding a home star is not as straightforward as we thought due to the complex dynamics of the Galaxy. The orbit of 1I before encountering the Solar System was roughly circular making it possible that it migrated large distances within a relatively short time from some other area in the Galaxy so may never know which solar system was its original home.
When: December 11, 2018 @ 12:00pm
Where: PAB, B305, 3rd floor
The Brightest Stars in Kepler and K2