These research projects were available in past years of Pre-MAP:

1. Using Computer Simulations to Study the Bar in the Thick Disk of the Milky Way

Faculty advisor: Victor Debattista

Like many other galaxies, the galaxy we live in (the Milky Way) contains a thin disk of young and old stars, and a thick disk of old stars. (The Sun belongs to the thin disk and sits about half way out to the edge of the disk.) The thin disk is the most massive component of the Milky Way, and accounts for 85% of the total mass of the galaxy. It is made up of spiral arms, an S-shaped bend or warp at large radii, and a bar at the center. Details are here. NGC 5248, a spiral galaxy much like the Milky Way. Image courtesy the Sloan Digital Sky Survey.

The bar of the Milky Way is visible some distance above the plane of the thin disk. The fact that a bar is present means that stars cannot move on circular orbits around the center of the galaxy. Instead they must move on elongated orbits. When we look to either side of the center of the Milky Way, we find that thin disk stars have different velocities because the system is not symmetric.

How important is this effect for thick disk stars? To address this question, we can use computer simulations to study what happens to the thick disk when a bar forms in the thin disk. We have already run such simulations and found that a bar also forms in the thick disk. But what would the observational signature of such a thick disk bar be? What will the velocities of thick disk stars be?

You will take the computer simulation and view it in the same way we view the Milky Way from Earth and then measure the velocities of the stars in the computer model. A set of observational velocities will be available for comparison.

2. Observing Variable Stars Using the 12 inch Telescope

Faculty advisor: Ana Larson

Research on variable stars is important because it provides information about stellar properties such as mass, radius, luminosity, temperature, internal and external structure, composition, and evolution. This information can then be used to understand other stars. Pofessional astronomers work with only a handful of large telescopes, and so cannot gather data on the brightness changes of thousands of variable stars. Details are here. An artist's impression of a cataclysmic variable, one category of variable stars. Image is copyright Mark A. Garlick / space-art.co.uk, used with permission. Please do not use this image without contacting the artist first.

Instead, it is amateur astronomers, utilizing small telescopes, who are making valuable contributions to stellar astronomy by observing variable stars and submitting their observations to the American Association of Variable Star Observers (AAVSO) International Database.

You will obtain and analyze real data from the 12 inch Meade telescope located on the observation deck of the Physics and Astronomy Building. Many variable stars such as cataclysmic variables and RR Lyrae stars change their brightness significantly over short periods of time. For cataclysmic variables, this change can happen within hours; for RR Lyrae stars, this change happens over a night. Thus, a few clear nights will suffice to obtain data to contribute to the AAVSO database. You will become part of an international observing effort, reflecting the international scope of the study of astronomy.

3. Identifying New Cataclysmic Variables with the Sloan Digital Sky Survey

Faculty advisor: Paula Szkody

Binary stars comprise more than half of the stars in the sky. Very close binaries (those separated by only the diameter of the Sun) are especially interesting, because the closeness of the stars usually means that matter is transferred from one to the other, altering their entire evolution. The close binaries that contain a cool M star transferring its mass to a hot white dwarf star are called Cataclysmic Variables (CVs). Details are here. Optical spectrum of a cataclysmic variable binary star system.

Due to the mass transfer, CVs undergo a large amount of variability. In an effort to understand this variability, and ultimately the long term evolution of these systems, a group of faculty, postdocs, grad and undergrads students are participating in a five year effort to find CVs that have spectra available in the Sloan Digital Sky Survey (SDSS).

You will identify CVs by sorting through the SDSS spectra. You will then make finding charts from the Digitized Sky Survey that can be used in follow-up studies with the Apache Point Observatory telescope, help observe during the remote observations with APO, do a literature search for all discovered objects to see if they are known or new, and compare and contrast all the spectra of systems for which multiple spectra exist in the archive.

4. Searching for Gravitationally Lensed Quasars with the Hubble Space Telescope

Faculty advisor: Scott Anderson

Light emitted from distant luminous astronomical objects traverses extraordinary distances across the Universe before being detected by a telescope. One class of astronomical objects known as quasars, whose enormous light output arises in energy released via the accretion of matter onto a supermassive black hole, can be studied with even modestly sized telescopes out to distances exceeding 10 billion light years. Gravitational lenses due to the cluster Abell 2218. The arcs around the bright cluster of galaxies (left) are multiple images/project_images of the same distant galaxy hidden behind the cluster.

On very rare occasions on the long journey to our telescopes the light from a quasar will be bent and focused by the force of gravity of a massive object (galaxy or cluster of galaxies) that lies along the line-of-sight between the Earth and the distant quasar. The intervening massive object acts as a gravitational lens, bending the light of the quasar and sometimes producing a "mirage" of multiple, closely spaced images/project_images of the solitary quasar. Such rare, gravitationally lensed quasars are unique probes encompassing a wide range of applications in astrophysics.

You will examine roughly 100 HST images/project_images searching for new cases of lensed quasars. You will then swap images/project_images with another student to insure that you haven't missed a interesting case. Any interesting cases would be suitable for more intense study, first to confirm that they are newly discovered lensed quasars, and perhaps culminating in a scientific publication describing any n ew lens discoveries.

5. Assembling the SDSS Large Galaxy Atlas

Graduate student advisor: Andrew West

Catalogs of galaxies are a useful tool for studying galaxy properties, since by looking at many galaxy images it becomes possible to see trends in size, color, morphology and more associated with different galaxy types. Galaxy A0741+29 from the catalog.

Andrew West has developed an extensive software pipeline to create images from the Sloan Digital Sky Survey which are optimized for studying the properties of large galaxies. You can see images created from this software pipeline at http://www.astro.washington.edu/west/rc3. Note that this is a LARGE catalog, so may take many minutes to load over high speed internet connections, and is probably hopeless over dial-up!

While the first draft of this catalog now exists, many images have significant defects that will make them unusable for measuring galaxy properties. These defects include images with missing data, galaxies larger than the current default image size, off-center galaxies, or galaxies contaminated by light from planes and satellites or neaby bright stars.

The Pre-MAP team will contribute to the assembly of the SDSS Large Galaxy Atlas by visually inspecting the galaxy frames for defects such as those above and any other unforeseen problems. Any problematic images will be recorded, along with a description of the defect, for reprocessing. Once a complete list of images needing additional processing is assembled Pre-MAP students can assist in generating the replacement frames for the catalog. Eventually all images will need to be analyzed to fit galaxy models to the data -- this represents a longer term project that interested Pre-MAP students could contribute to over the course of this and successive years.

6. Using Low Mass Stars as Probes of the Structure of the Milky Way

Graduate student advisor: Kevin Covey

Low mass stars represent the dominant stellar component of the Milky Way. Additionally, these stars have such long lifetimes that every low mass star born in the Milky Way is still present as a main sequence star. Their large numbers and long lifetimes make them ideal tracers of the history and structure of our Galaxy. Spectra of low mass stars.

By studying the position of these stars in the galaxy (requiring knowledge of their location in the sky and their distance from us) as well as of their velocity in the galaxy, we can learn about the structure of the galaxy and its formation history.

The Pre-MAP team will assemble a large sample of low mass stars with spectra observed during the Sloan Digital Sky Survey for further analysis. The Pre-MAP team will then use a previously written software program (see figure 1) to assign spectral types to this sample by comparing each star to a set of template spectra. Once each star has been assigned a spectral type, they can be compared with a template of the appropriate spectral type for which the radial velocity is very precisely known (see figure 2), and the distance can be derived from known relationships between the spectral type and absolute luminosity of these stars. Knowing their velocities and position within the galaxy, we can then investigate the rate at which stars gain energy, puffing up the Galactic disk in the vertical dimension.

7. Deconstructing Galaxies in 3 Dimensions

Faculty advisor: Victor Debattista

Galaxies are the fundamental building blocks of the universe. Modern cosmology began when Erwin Hubble recognized that the fuzzy "nebulae" seen earlier with less sensitive telescopes were not part of our galaxy, the Milky Way, as had been thought, but were galaxies themselves. NGC 5248, a spiral galaxy much like the Milky Way. Image courtesy the Sloan Digital Sky Survey.

As Hubble already noticed, galaxies come in various types. The most common type has a disk of stars, with the stars orbiting about the center. These 'disk galaxies' also contain central concentrations of stars, known as bulges. One of the most common ways of studying disk galaxies is to decompose images of them into the part that is the bulge and another part that is the disk. But the precise definition of bulges and disks continues to be debated because such decompositions are to some extent arbitrary. Worse, nature grants us only one view of any galaxy, and usually we have to contend with dust and bright star forming regions which make study of such images difficult.

In this project we will study images of simulated galaxies which we can view from any orientation we like. We will explore how the properties of the bulge and the disk seem to change as we change our viewing orientation. (Click here for an animation.) Because in the simulated galaxies we know the full three dimensional structure of the system, this will allow us to establish how reliable such decompositions of galaxies are. At the end we can compare with a few real galaxies to make statements about their different components such as how round and flat are disks? How close to spherical are the bulges?

Click here for more details on this project.

8. A New Way to Investigate Stellar Properties from Spectra

Graduate student advisor: Amy Kimball

One way astronomers observe stars is to examine their spectra: a spectrum is a graph that shows how much light a star is emitting at different wavelengths. Spectra can be used to figure out scientifically important information about a star, such as its metallicity (how many heavy elements the star contains) and the amount of gravity at its surface (which depends on both the star's size and its mass). Spectrum of our sun.

A new method of studying these properties from a star's spectrum is available using the recent development of Principle Component Analysis (PCA). PCA is a way to simplify a set of data (like spectra) by breaking it down into a set of components which describe the data set. Each spectrum is a particular combination of some of the components which describe the whole data set. An example of PCA is describing the color "orange" by saying it contains one part "red" and one part "yellow".

For this project, you will use available code to do PCA on a set of spectra to find out if there is a relationship between the primary spectra used to build a particular star's spectrum, and the metallicity and gravity of that star. To answer this, you will look at stars whose metallicity and gravity are already known from other methods, and compare the PCA results for those stars to their metallicity and gravity values. If PCA is a good analysis tool, you will discover a way to predict the metallicity and gravity for any star based on its own spectrum, and the primary spectra you got from PCA! A positive result would lead to the inclusion of your project in a short scientific paper.

Click here for more details on this project.

9. Hunting for New Supernovae and Other Variable Objects in the Sloan Digital Sky Survey

Faculty advisor: Andy Becker

Supernovae are among the brightest and most violent events known to mankind. They are the explosions of dying stars, marking a fiery and spectacular end to their lives. The light from these objects can be used to examine both the shape and composition of the Universe between us and the supernovae. Hubble Space Telescope image of supernova 1999i. Supernovae can be as bright as the galaxy they live in before fading away.

The Sloan Digital Sky Survey (SDSS) is about to begin searching the sky for supernovae. Starting in September and for three months, the SDSS telescope will continuously monitor two large regions of the sky, alternating between them every other night.

You will detect objects that have varied in position or brightness from one night to another by subtracting one image of the sky from a later image of the same piece of sky. Some of these will be supernovae. The sky is full of other interesting variable objects, such as asteroids, variable stars, man-made satellites (some of which do not officially exist), and black holes at the centers of distant galaxies. Any new objects you find, in particular supernovae and comets, may be eligible for publication by the International Astronomical Union Circulars Central Bureau for Astronomical Telegrams.

Click here for more details on this project.

10. M Dwarfs as Tracers of Galactic Populations

Advisors: John Bochanski, Suzanne Hawley

Low-mass stars are the dominant stellar component of the Galaxy. Their slow evolution and ubiquity combine to make them common members of all parts of the Galaxy. Thus, we can use these stars as tracers of different Galactic populations. Artist's impression of tidal streams in the Milky Way, courtesy of Steve Majewski

By studying the position of these stars in the galaxy (requiring knowledge of their location in the sky and their distance from us) as well as of their velocity in the galaxy, we can learn about the structure of the Galaxy and its formation history.

The Pre-MAP team will study a large sample of over 8,000 low-mass stars observed as part of the Sloan Digital Sky Survey. Combining distances measured with relations determined at the University of Washington, along with radial velocities and proper motions, the full space motions of each star will be determined. Pre-MAP students will study the most interesting subsample of these objects, inspecting large velocity outliers to ensure their accuracy (in both velocity and spectral type). This subsample will probe the oldest parts of our Galaxy, investigating the Milky Way in its infancy.

Click here for more details on this project.

11. Probing for the Presence of Puny Planets

Faculty advisor: Eric Agol

Over the past decade astronomers have discovered 200 planets orbiting other stars. Most of these are much more massive than the Earth, although recently planets have been found that are as small as about 10 times the mass of the Earth. Artist's depiction of a planetary eclipse in the HD 209458 system. Copyright 1999, Lynette Cook.

Pushing towards the detection of "puny" planets as small as the Earth is one of the grand challenges in astronomy. Towards this end, I have proposed a technique which uses large Jupiter-sized "giant" planets which partially eclipse their host stars. If the large planet is alone, then the times when the eclipses occur should be precisely periodic, like the ticking of a clock. However, if a second puny planet exists in the system, then the eclipses will not be exactly periodic due to the gravitational pull of the puny planet.

Your task will be to look at observations of the eclipses of extrasolar giant planets taken with the Hubble Space Telescope, analyze the data to measure how bright the star is at different times, and then use already computed models to fit that data and determine the time when each eclipse occured. Then, these results will be used to determine whether the eclipses are exactly periodic, or, more interestingly, not exactly periodic. In the latter case we will determine whether there might be another planet in the system. In the former case, we will place constraints on the presence of other planets. In principle, this data will be sensitive to planets with masses as small as our Earth.

Click here for more details on this project.

12. Understanding the Physical Processes Active in Galaxy Starbursts

Faculty advisor: Fabio Governato

Many galaxies reside not alone, but in groups and clusters. In these crowded environments, galaxies interact, collide and even merge together to form larger galaxies! Telescopes have imaged several of these cosmic collisions, revealing how galaxies undergo radical morphological transformations as they are smashed together. Simulation of two spiral galaxies about to merge.

The observations reveal that in such mergers, stars can form at rates larger than 1000 solar masses/year. The most massive of this rapidly forming population of stars have very short lifetimes, before exploding as supernovae. Winds generated from these supernovae sweep galaxies of their remaining gas content. This will halt the supply of gas required for further star formation: following a major starburst star formation ends abruptly. How important are galactic winds to quench star formation? What are the observational signatures connected to a major starburst?

The team will run simulations of galaxy mergers or analyze existing ones. (Click here for examples of merger simulations generated at UW.) Different physical processes connected to star formation and energy feedback can be turned on and off, and varied in intensity, to learn about their relative importance in shaping galaxy properties.

13. Galaxy Mergers: Comparing Theory with Observations

Faculty advisor: Fabio Governato

One set of tools developed here in Astronomy's "N-body Shop" allows astrophysicists to simulate galaxy mergers and to include a detailed description of the physical processes involved. Only by comparing these simulations with the observable universe will we know if our models are correct. Simulation of above galaxies shown after passing through each other.

Once a simulation has been run, artificial images in the optical or infrared bands can then be created from the simulations as if they had been observed with Space Telescopes like Hubble, Spitzer and GALEX.

The team will create and analyze artificial images from simulations of galaxy interactions and mergers. These artificial images will be analyzed with existing software to measure the global properties of galaxies, such as their light distribution in different optical and infrared bands. A comparison with published observations will allow us to understand if the current modeling of galaxy mergers does indeed explain the properties of real galaxies, or if our theoretical understanding of such events will need to be modified!

14. Searching for Inner Solar System Objects with SDSS

Faculty advisor: Andy Becker

The Sloan Digital Sky Survey (SDSS) has imaged the same patches of sky multiple times to search for supernovae. These images are also very useful to detect inner solar system objects: since they are so close to us and moving, they appear in different locations in each image. The red, green, and blue tracks in this image show the motion of an asteroid. Image courtesy the Sloan Digital Sky Survey.

The Pre-MAP team will use the SDSS Supernova Survey difference imaging database to search for inner solar system objects. The survey team has designed their scanning software to weed out known variables and objects in motion. We intend to examine the objects automatically or manually classified as moving objects.

The research plan has three primary goals : search for comets in the data; accurately measure the colors and extend the orbits of known asteroids in the data; and extend the orbital completeness by nearly 2 magnitudes by "linking" multiple instances of unknown objects into new orbits.

15. Constructing a Comprehensive Catalog of RR Lyrae Stars

Faculty advisor: Zeljko Ivezic

Some of the best objects with which to study the outer regions of the Milky Way galaxy are RR Lyrae stars. RR Lyrae stars are standard candles, meaning that it is straightforward to determine their distances; they are also sufficiently bright to be detected at large distances and are fairly numerous. Light curve of RR Lyrae, the prototypical RR Lyrae star! RR Lyrae stars brighten and dim periodically, and their true brightnesses and distances can be derived from their periods.

Observations of RR Lyrae stars allow us to trace the structure of our Galaxy. For example, overdensities in their distribution could indicate that we have detected a small satellite galaxy that is being swallowed by the Milky Way, as is currently happening with the Sagittarius dwarf galaxy. Several catalogs of new RR Lyrae stars have been obtained using the Sloan Digital Sky Survey (SDSS); different methods have produced slightly different catalogs.

You will analyse all of these SDSS catalogs of RR Lyrae stars and quantify their completeness and their contamination by non-RR Lyrae stars. You will verify whether significantly different methods reveal an overdensity of RR Lyrae stars, thereby providing strong evidence for the presence of interesting sub-structures in our Galaxy.

Click here for more details on this project.

16. Calculating Comet Impact Rates on Earth During Comet Showers

Advisor: Nate Kaib

Comet showers are time periods when the number of long-period comets passing near the Earth increases by factors of 100 or more. These periods can last for as long as a million years, and there's no doubt that the rate comets collide with the Earth will go up as well. Luckily, comet showers only occur every few hundred million years. Predicting the rate of impacts the Earth should experience during one of these events is useful to determine whether or not comet showers pose a threat to life on Earth. 1997 image of comet Hale-Bopp, a typical long-period comet.

Comet showers are triggered by another star in the Milky Way passing very close to and disrupting the Oort Cloud, which is a spherical reservoir of about one trillion cometary bodies surrounding our solar system. You will be analyzing the results of many different computer simulations of these types of stellar passages through the Oort Cloud. By combining these simulation results with observation statistics of real long-period comets, you will determine how often the Earth suffers collisions with these comets.

17. Searching for hot Jupiters with LSST

Advisors: Mark Claire, John Bochanski

Observing stars for periodic dips in brightness has emerged as an exciting and robust method for finding Jupiter-mass planets around other stars. This project aims to answer the question: Will the Large Synoptic Survey Telescope (LSST, a telescope due to begin operation in 2012) be able to observe planetary transits and significantly add to the number of known extrasolar planets in our Galaxy? Preliminary results from this project indicate that the answer might be a resounding YES! A planet passing in front of a star blocks some of the star's light.

This project primarily involves simple computer programming in IDL. The project will involve running and linking inputs and output files between 3 existing computer models for 1) generating planetary transit light curves, 2) simulating how LSST will observe those systems, and 3) attempting to detect the signal of the planet in the simulated LSST data. We hope to identify the most likely LSST targets for planetary detection, provide quantitative estimates of the number of planets that could be found, and to provide recommendations on search criteria which would maximize LSST's capabilities for planetary detection.

18. Planetary Nebula Central Stars in MACHO

Advisors: Julie Lutz, Oliver Fraser

Planetary nebulae (PN) are old stars that are shedding their outer layers on their way to becoming white dwarf stars. Most low mass stars will go through this phase. The mass that they shed is returned to the interstellar medium to eventually go into new generations of stars. A planetary nebula: the death throes of an average star.

In this project we will concentrate on the stars that are left behind rather than the gas that is being ejected. Our goal is to learn more about the central stars of PN. What we will do is to look at some central stars that are included in a massive online astronomical database called the MACHO project. The central stars in question (about 25) happen to be located towards the center of the Milky Way Galaxy in a region where the MACHO project observed took observations for five years. We will locate the central stars, look at their observations and determine whether or not they are variable.

For those that are found to be variable, we will investigate whether or not the variability displays any period. Finally, we'll think about what could cause the variability. Stars change their brightness for many reasons. Some stars are members of binary systems where one star comes in front of the other periodically. Other stars pulsate or have eruptions on their surface.

19. Searching SDSS for eclipsing binaries

Advisors: Eric Hilton, Adam Kowalski

The Sloan Digital Sky Survey has taken many observations of the same patch of sky over the last several years. This project will look at these data for stars that are dimmer than usual during at least one of these observations. We will be looking for stars (or perhaps planets) orbiting each other when one object passes in front of the other from our perspective here on Earth. Information from eclipsing systems can be used to calculate the masses and sizes of the stars, which is otherwise very difficult to obtain. An example of eclipsing systems

We will be using statistical techniques already developed to find these target objects. You will write simple computer programs to search through these targets, and use the SDSS data base to gather additional information about the objects. Possible extensions of the project involve making follow-up observations with the 3.5 meter Apache Point Observatory telescope.

20. The search for radio stars

Advisor: Amy Kimball

Normal stars radiate very strongly in visible light (like our sun), but very weakly in the radio. If a star does emit strong radio signals, it can be a sign that something strange is going on, such as a flare, a supernova or an interaction with another nearby star. An image of the sun and sunspots taken in the radio (6cm wavelength).

In this project, we will look for stars which emit strongly in the radio, but otherwise appear normal. You will determine a simple selection of normal stars based on their brightness and color, and match these stars to a pre-existing sample of radio sources. The goal is to determine the fraction of "normal" stars with radio emission, and to see if they differ in significant ways from stars without radio emission.