Last updated January 2012

Please come talk to me if you have an interest in any of these projects. They are most definitely suitable for undergraduates with some knowledge of astronomy. I prefer students who have taken Ay 20 and who have some unix / programming experience. I generally work only with Caltech students.

Projects are divided into those that deal with astronomical data, those that involve programming to model or simulate various phenomena, and those that are more about organization and/or web content. Note that towards the bottom of this page there are some urls linking to potentially useful background information relevant to the types of research I do. Also, there are some other ideas here if you want more advanced challenges.


ASTRONOMICAL DATA

  • I have various data sets consisting of imaging or spectroscopic data that need basic data processing or "reduction". These include several data sets from the Palomar Observatory and/or the Keck Observatory. The basic steps include bias subtraction and flat fielding, with possibilities like image mosaicing or spectral extraction depending on the type of observations. When the primary steps are completed the data will then be ready for analysis by either you or another student who follows you. Current data sets include:

  • After basic image processing has been completed, photometry and/or spectroscopic analysis is needed. This is where the science starts to happen. Current data sets and needs include:

  • Young stars exhibit a wide range of time-variable phenomena. This is due to a combination of rotation, accretion, and extinction effects. Between two different collaborations there is times series monitoring data in the optical (from the Palomar 48" telescope) and in the mid-infrared (from the Spitzer space telescope) to play with. Analysis of these data sets is a good undergraduate opportunity.

    ORGANIZATION OF INFORMATION ON YOUNG STARS

  • We are currently assembling a broad sweep of data from both on-line resources and from the astronomical literature on young stellar clusters and associations. Our aim is to build a trustworthy database for young star research so as to make queries and scientific productivity easy. We need your help! Specifically, a list of clusters is here along with links to their SIMBAD entries where lots and lots of information can be found. While I have membership lists for some of the clusters, the information needs to be downloaded and organized. For others, a literature search is needed in order to acquire just the reference list. Referencing to the primary information sources is critical! A previous SURF student (Daniil Feldman) wrote the initial infrastructure for the database and a current postdoc (Nairn Baliber) has exapanded it and enabled the user interface. This is a good project for someone without much astro experience but who wants to learn about the astronomical literature and on-line data portals. You could even do it in excel if you insist!

  • I would like to make publicly available much of my spectroscopic and imaging data sets on star forming regions. Someone could set up the web infrastructure for this, with links to my available data in .fits file format.

  • Along these same lines, something purely mechanical that needs to be done is reading in old exabyte tapes and translating the data onto another storage format such as DVD. This isn't exactly research, but I'll pay you for your time while you read a book or surf the web!

  • Designing and writing science content for Palomar Observatory public outreach. Material would appear in the visitor galleries on the mountain as well as on-line. Specific task would be explaining in simple terms -- first -- the electromagnetic spectrum of stars from the UV (ultra-violet) through the Mid-IR (infrared). Young stars have UV excess due to enhanced sun-like chromospheres. They also have IR excess due to surrounding dust. Second task is to explain how the signatures of ``protoplanetary disks" seen around other stars are relevant to understanding the conditions in our own solar system when it was only a few tens of Myr old.

    PROGRAMMING MODELS OR SIMULATIONS

  • A pure analysis project requires some resourceful sleuthing of the literature on fundamental stellar properties and probably some use of stellar atmospheres models. The need is to determine the bolometric correction scale for young pre-main sequence stars. Dwarf (luminosity class V) and Giant (luminosity class III) scales exist, but no one has taken a hard look at the appropriate bolometric corrections for luminosity class IV. Because bolometric corrections are key to determining stellar luminosities and hence stellar masses and ages, it is important to understand the systematics of the standard methodology and just how much in error we could be with the approximations currently employed by most researchers in this field.

  • Another pure analysis project is to simulate the effects of both random and systematic errors in observables on some of the key derived quantities for young stars. Specifically, some questions to be answered are: What are the formal errors in stellar mass and stellar age across the pre-main sequence HR diagram that result from errors in photometry, in spectral type, and in extinction? How is the calculated infrared excess (indicative of circumstellar material) affected by errors in photometry, in spectral type, and in extinction? This is a programming project, with direct application to some of today's most compelling questions in planet formation and evolution.
    Useful background and resources for these projects:

    SCIENCE BACKGROUND:

    A list of good review articles relevant to young stars research

    A college lecture on star formation

    A small tutorial on star clusters and star forming regions where you can click on the link to T Tauri stars.

    Here is a dictionary defition of "T Tauri Star": A young low-mass star characterized by variability, the presence of hydrogen emission lines, and often other signatures of circumstellar gas and dust including bright x-ray, ultraviolet, infrared, and radio emission. T Tauri stars are named after a variable star in the constellation Taurus that exhibits particularly strong hydrogen lines as well as strong ``excess continuum" over a broad range of wavelengths. The association of T Tauri stars with dark cloud regions on the sky is more than coincidental. Stars are formed by the gravitational collapse of dense areas of interstellar material and the young T Tauri stars are identified with the earliest phase of stellar evolution during which stars emerge from their natal molecular cloud cores to become detectable at visible wavelengths. Before this stage they are said to be ``embedded" in the obscuring gas and dust. T Tauri stars with very strong emission lines are designated ``classical T Tauri stars" while their counterparts with reduced hydrogen emission are known as ``weak-line T Tauri stars."

    Young age Several lines of evidence confirm the extreme youth of T Tauri stars. They are located in star forming environments typically within or near dark clouds of gas and dust. Born together in aggregates, associations, or even clusters, these groups of T Tauri stars have stellar densities that are too low to have withstood disruption by galactic tides for more than a few times their age. At present they are bound together gravitationally but only temporarily by the mass of their parent molecular cloud. As expected from much younger versions of our own Sun, T Tauri stars exhibit high variability in x-rays that measure emission from a strong and active corona, and at ultraviolet and optical wavelengths that similarly measure chromospheres. The luminosities and surface temperatures of T Tauri stars place them above the zero-age main sequence on the Hertzsprung-Russell diagram, with positions that are consistent with those of young stars prior to the onset of nuclear fusion of hydrogen near their centers. Evolutionary models of the gravitational contraction during this ``pre-main sequence" stage indicate stellar ages between 105 and 107 years. During this early stage T Tauri stars also exhibit strong lithium absorption lines which are an indicator of youth since lithium is a light element that is rapidly mixed down to interior regions of the star where it is consumed nuclear reactions.

    Emission lines and accretion/outflow The level of "activity" in T Tauri stars is even higher than the enhanced levels expected for their young age and is attributed to circumstellar disks, accretion, and outflow. The presence of dynamically flowing gas is implied by broadening of strong emission lines in the spectra of classical T Tauri stars. Comparison with theoretical simulations reveals that the high-velocity wings of observed spectral lines result mostly from the gas that is falling directly onto the star, although some features result from the accompanying winds and jets. These inflow and outflow processes are fueled by the coupling of accreting disk material to a rotating stellar magnetosphere. Material leaves the disk plane close to the star and travels along magnetic field lines in a "funnel flow." Some material is channeled along closed field lines towards the stellar photosphere where it causes a shock and thus some of the x-ray, ultraviolet, and optical emission, while some is flung out of the system along open field lines to appear as bipolar jets. Classical T Tauri stars thus resemble more exotic accretion-jet systems, such as accreting white dwarf stars, pulsars, and black holes at the center of active galactic nuclei where the origin of the accreting material is in a circumstellar disk.

    Excess continuum emission and circumstellar disks The existence of circumstellar dust disks around classical T Tauri stars is established by observations of long-wavelength emission at infrared (micrometer) through radio (millimeter and centimeter) wavelengths. The sources are much brighter than the expected stellar photospheric values which have an essentially blackbody spectrum. Instead, the observed spectral distribution of radiation coincides with that of a dusty disk with temperatures that decrease with disk radius surrounding the star. The disks have masses from 0.01 to 10% of the mass of the Sun, sizes of about 100 astronomical units (1.5 × 1010 km or 1 × 1010 mi), and constituent dust grains that are evolved from those in the interstellar medium in terms of both their size and composition. Imaging at high spatial resolution has resolved these disks in many cases at multiple wavelengths. Scattered light images obtained with the Hubble Space Telescope and ground-based telescopes such as Keck Observatory reveal the outline of disk surfaces. In addition, gas emission displays the Doppler signature of a disk that is rotating in accord with Kepler's laws. Virtually all classical T Tauri stars but far fewer weak-line T Tauri stars have circumstellar disks. The relative detection rates indicate that the disks evolve on short timescales -- within a few million years -- toward the formation of a planetary system. First the dust grows into large boulders or ``planetesimals" and eventually individual planets and for massive enough bodies the gas is also incorporated to produce ``gas giants" like Jupiter and Saturn. At somewhat later times, small amounts of dust result from the collisions of remaining planetesimals in ``debris disks," having little or no molecular gas. The transitional phase from gas-rich ``protoplanetary" disks to gas-poor planetesimal disks probes an important phase in the formation of planetary systems like our own Solar System. Taken as a whole, the properties, rate of occurrence, and inferred evolution for disks around T Tauri stars provide strong evidence that planet formation is a common by-product of the star-forming process.

    SKILLS BACKGROUND

    The SIMBAD server which accepts object names (or coordinates) and produces an overview page giving some basic stellar properties, source aliases, and most importantly a link to all published papers that reference the object (scroll down to the References heading and click on the "display" button). For example, type in "HD 105" in the top box.

    The ADS server which allows one to search for papers by author name or various text matches. For example, if I want to find a paper by Jeffries in 1997 I would enter the author in the author box and the year in the rightmost year box then hit "send query".

    For data reduction or analysis tasks, IDL tutorials are here (you can cut and paste the links):
    http://www.astro.virginia.edu/class/oconnell/astr511/IDLexercises/
    IRAF tutorials are here:
    http://www.ifa.hawaii.edu/~joshw/IRAFtutorial/index.html
    and introductory/interactive IRAF exercises:
    http://iraf.noao.edu/tutorials/tutorials.html


    Back to Lynne's teaching and advising page.