1995 Research Experiences for Undergraduates Program

NRAO National Radio Astronomy Observatory
Research Projects by NRAO Site

Charlottesville, Virginia (NRAO Headquarters)

Charlottesville students Christopher (`Kester') Allen, David Copeland and Edward Gray (left to right) examine David Malin's color optical image of Rho Ophiuchi and the region of Antares. David produced color radio images of the same region from data obtained at the NRAO 12m radiotelescope.

There were three students in the 1995 NSF Research Experience for Undergraduates (REU) program at NRAO-Charlottesville. Highlights of the program included a series of introductory level lectures on aspects of astronomy, particularly radio astronomy, spread over a few weeks. These lectures were intended to aquaint the students with the research which various staff members carry out.

Many of the students in the NRAO-Green Bank program visited Charlottesville for a tour of the Central Development Laboratory , and of the University of Virginia's facility for the fabrication of the Semiconductor-Insulator-Semiconductor detectors used in millimeter wave receivers, the Semiconductor Device Laboratory.

. The students had an informal get-together with astronomers from the University of Virginia at lunch, and from NRAO in the evening, followed by a visit with graduate students from the University's Astronomy Department.

Immediately afterward, the Charlottesville students visited Green Bank to see the NRAO telescopes located there, to meet members of the Green Bank staff, and to attend the annual picnic.

The students gave a series of 15 minute talks on their projects during a lunch symposium in Charlottesville before they began leaving for the summer.

Later in the summer, the students returned to Green Bank for a session of observations on the 43m telescope. This was a regularly scheduled program which Al Wootten, the Charlottesville REU coordinator, runs on the 43m to monitor the status of water masers in regions where low luminosity stars are forming. Two new water masers were discovered during the session. The students also toured the Green Bank Telescope, now about 180 feet high, the elevation axis assembled and the box structure which supports the surface being assembled on the ground.

Charlottesville students Christopher (`Kester') Allen and Edward Gray (left and right) stand on the apex of the elevation axis tower of the Green Bank Telescope during their tour of the site.

David Copeland
Reed College
Worked with David Nice

A Search for Transient Pulsar Signals

Student David Copeland (Reed College) worked on a project to search for fast (millisecond) dispersed transient signals in rapidly sampled spectral data from Arecibo Observatory. Such signals could come from pulsars or possibly other (unknown) Galactic phenomena. Copeland worked on the analysis routines for this project, both developing and optimizing the specific algorithm for the search and developing the overall software system. This involved quite a bit of coding in C, both reworking old routines and developing a single, coherent package. The algorithm development included many software runs on test data to study and fine-tune the search algorithm.

David also processed data to form images taken at NRAO's 12 meter telescope. The data was taken using a new type of observing. Normally observing is done by moving the telescope into a specific position, observing for a period of time, then moving the telescope and observing at another position for a while. This is very inefficient because most of the time is spent waiting for the telescope to stop shaking. A new observing mode called OTF or On The Fly observing is being developed at NRAO. This mode moves the telescope constantly and records the position of the telescope with very fine precision. No time is wasted waiting for the telescope to stop moving since it never does. This mode is subject to a sort of "motion blurring" but such blurring can be removed mathematically and maps can be constructed that are as good as images made with the conventional observing mode. David was working on a star forming region in the constellation Ophiuchus. This C18O J=1-0 map of the Ophiuchus Dark Cloud shows a velocity coded image, wich blue highlighting lower (blueshifted) velocity portions of the cloud, red higher (redshifted) velocity portions of the cloud, and green showing material lying near the clouds average velocity. The kinematically disturbed region to the upper right is known as the Ophiuchus A core, and here the most massive stars have formed.

Edward Gray
Boston University
Worked with Darrell Schiebel

A Graphical Class Browser for AIPS++

Summer student Edward Gray made a lot of good progress on a graphical class browser. Take a look at it: Graphical browser Basically, it first lists the set of AIPS++ modules; you click on one, and you end up with a list of the base classes in that module. From there, you click on the boxes to get documentation and click on the triangles to descend into the tree.

Kester Allen
Amherst College
Worked with Al Wootten

Water Masers and Cold Gas (Ammonia) in the L1448 Star Formation Region.

At several epochs, observations have been made of the L1448 star-forming region at the VLA in order to locate pointlike sources of emission in the 22 GHz line of interstellar water. Collisions in shocks near the forming star produces brilliant, non-thermal emission from water molecules. The pointlike sources are known as water masers. Allen reduced these observations for three epochs in 1994. Several primary centers of star forming activity occur within a region of about 90" extent in L1448. All of the masers present in 1994 occur near the southernmost of these centers, known as L1448C. The masers appear segregated by velocity, with those shifted to higher frequency (blueshifted) relative to ambient gas occurring in one sector, and those shifted to lower frequency (redshifted) occurring in another sector. The two clusters of masers lie along a line which is parallel to an outflow of gas observed on much larger scales toward L1448C. Presumably, the masers trace shocks near the origin of the flow, within scales of tens of AU from the young star.

On much larger scales, thermal emission from ammonia molecules has been mapped using the VLA by Wootten and Mangum. Allen investigated the ammonia images for evidence of thermal gas in proximity to L1448C. The intensity maps show a pronounced ridge surrounded by several knots of bright gas around the location of the masers. Disk-like, the ridge is symmetrical around the maser positions, and has a "tied- off" pinched appearance in the section closest to the maser. This feature is oriented approximately 65 degrees E of N, and is approximately 20'' or 5000 AU across; since this is perpendicular to the observed angle that a line between the blue- and red-shifted masers forms, this suggests that the ridge is related to a possible accretion disk for the hypothetical protostar within. Strong ammonia emission was also observed from the IRS3 protostars to the north.

Socorro, New Mexico (NRAO Array Operations Center)

Students conducting their research at the NRAO Array Operations Center (AOC) in New Mexico included John Barthelmes, James Brauher, Christopher Carpenter, Amy Hronek, Audress Johnson, Allison Nugent, and Ngan Ying Lui. The program at the AOC is under the direction of Dr. Claire Chandler and Dr. Bryan Butler.

Claire wrote a report on the summer student program at the AOC:

This year the VLA held its regular Synthesis Imaging Summer School in Socorro. Since many of the lecturers who we usually invite to give talks to our summer students were already speaking for the Summer School, we asked the summer students to arrive in time for the School so that they could attend. After this, and several lectures about radio astronomy and interferometry presented by Bryan and myself, many of them showed a good understanding of the technique. We also gave talks on general topics in astronomy, and invited other members of the scientific staff to do the same. The astronomy talks went down well with the students.

I took the summer students on a field trip to visit the observatory at Kitt Peak, including the instruments of NOAO, the NRAO 12-m , and the VLBA antenna. We also visited the Mirror Lab at Steward Observatory. This trip was a big hit, and the students requested more like it in the future. The students from NOAO visited us in Socorro on their way to the National Solar Observatory at Sac Peak , and I gave them a tour of the VLA.

Our students were given a couple of hours of their own VLA time, which was used for an OH maser search toward supernova remnants, a project supervised by Dale Frail.

Our students also gave guided tours of the VLA every weekend, and at the end of their time here, each student gave a short lunch talk (about 15 minutes) about their summer project.

John Barthelmes
State University of New York
Worked with Ruth Milner

From SunOS 4 to Solaris

John Barthelmes worked with Ruth Milner assisting with various aspects of the migration of our Sun workstations to the new Solaris 2 operating system. John's tasks began with obtaining and compiling the source code for a number of public-domain packages we use on our systems. He inventoried both our SunOS 4 and Solaris systems to determine which programs were missing in the new environment, and then located and retrieved the source code for everything he could find. He then successfully built about fifty packages. His next major task was to learn the "perl" language and use it to write scripts which would enhance the usefulness of the system software installation log that is kept at all NRAO sites. The scripts he produced will be used to search the log and print information about the package specified by the user, and he also wrote an HTML front end (including a perl CGI script) for updating the log file. John then took the plain TeX copies of the UNIX Introduction and the AOC Guide to Computing (nearly eighty pages of documentation) and retypeset them in LaTeX, and using "latex2html" he then produced HTML files from the LaTeX versions, which will allow users access to HyperText versions of these documents from the Socorro Computing WWW pages. John also updated several sections of these documents, including the diagrams of our public computers. The results of his work should be useful to us for a long time to come.

Jim Brauher
University of Michigan
Worked with Huib van Langevelde

Measuring Stellar Proper Motions Via OH Masers

Jim Brauher worked with on the analysis of spectral line VLBA data. The main goal of this project was to measure the proper motions and annual parallaxes of two Mira variables, U Her and R LMi. The OH masers associated with both objects were observed with the VLBA for two epochs in phase referencing mode. Jim used the AIPS reduction package to map the circumstellar main-line OH masers with both phase referencing and self-calibration, and compared the results. He also constructed moment maps of the large data cubes. His analysis revealed discrepancies with the standard model, in which the brightest maser should line up with the stellar position and coincide with the most blue-shifted component in the spectrum. A publication on this subject is in preparation. Short VLA observations of the same objects were made and processed to measure the amount of flux resolved out by the VLBA . Finally, Jim completely recalibrated the data from one of the epochs, in order to correct for a missing component in the correlator model. This will enable us to use the data for astrometry.

Chris Carpenter
Harvard University
Worked with Dale Frail

A Search for Radio Counterparts of Gamma Ray Bursters.

Chris Carpenter worked with Dale Frail on a long term monitoring effort to look for the radio counterparts of gamma ray bursters. Gamma ray bursts are brief flashes of energetic emission from random directions in space whose origin is completely unknown. It is expected that some fraction of this radiation should come out at radio wavelengths, resulting in a time-variable radio source. Chris reduced and analyzed VLA data taken over several epochs toward 9 gamma ray burst error boxes. A total of 50 images were made and a variability analysis was done on the 112 sources cataloged from the images. Three unusual time-variable sources were found in the error boxes of the gamma ray bursters. Follow-up optical observations are planned.

Amy Hronek
Occidental College
Worked with Craig Walker

Behavior of VLBA Antennas and VLBA Dynamic Range Tests

Amy Hronek worked with Craig Walker on two projects during the summer of 1995. The first was an effort to characterize the system temperature, gain, and overall sensitivity of the VLBA antennas as a function of frequency across the full range that can be observed in each band. This project involved several sessions of single dish observing using all of the VLBA antennas and reduction of the monitor data using both standard VLBA software and a new program that she and Walker wrote. The project will result in a VLBA Test Memo which she wrote and Walker is in the process of finishing. The second project was a test of the ability to make high dynamic range images using VLBA data recorded in the 2 bit mode. All previous high dynamic range tests had been done in 1 bit mode. This project involved one session of VLBA interferometric observing, correlation on the VLBA correlator, and reduction of the data in AIPS and SDE. Amy did most of the data reduction. The test was successful and Walker will write a very short memo to that effect based on her work.

Audress Johnson
The University of Texas at Austin
Worked with Rick Perley

An Update to the VLA Calibration Scheme.

Audress Johnson worked with Rick Perley on a project aimed at updating the VLA's calibration scheme. After mastering the intricacies of calibrating radio interferometer data she went on to determine accurate flux density ratios for various standard VLA calibrators. Her work will be vital in maintaining the high quality of data coming out of the VLA.

Ngan Ying Lui
Polytechnic University
Worked with Clint Janes

Interference Protection.

NGAN YING LUI Ngan Ying "Annie" Lui worked with Clint Janes in the Electronics Division at NRAO Socorro. Her assignments were to support the Interference Protection Group in its efforts to identify and mitigate radio frequency interference to radio astronomy observations. NRAO has had in place for some time a procedure to measure interference in the 20 cm observing band at the VLA, and recently those plots were made accessible via the World Wide Web. Ms. Lui added an overlay to the plotting procedure so that now Web browsers can find specific frequency and other helpful information to better interpret the amplitude vs. frequency information on the plots. In the process, she improved understanding of the overall procedure so that she could copy the entire interference measuring procedure to the VLA 90 cm band, and make interference plots available on the Web for that band as well. The project involved writing an Observe File for the VLA and modifications to existing AIPS (Advanced Image Processing System), Fortran, and Unix routines. She also supported one of the scientists, Dr. Vivek Dhawan, in his efforts to translate the VLA interference measuring procedures to VLBA bands. Using her work, data were successfully observed. To spot check Dhawan's measurements, she used a VLBA remote operating procedure called SPAN to find and plot interfering signals at VLBA sites. In the process she improved the understanding of SPAN plotting procedures. Finally, Ms. Lui prepared a recommendation for the VLBA Field Group Leader on displaying graphs at the remote VLBA sites of data gathered from a central VLBA data monitor in Socorro.

Allison Nugent
Southwest Missouri State University
Worked with Mark Holdaway

Radio Images of Large Supernova Remnants.

Allison Nugent worked with Mark Holdaway on reducing and analyzing VLA data on a sample of large supernova remnants. This sample was poorly studied because of the large angular size of the remnants, most of which required adding total power from the Effelsberg 100 meter antenna and mosaicing several VLA pointings together. Allison responded well to the technical challenges of mosaicing the VLA and Effelsberg data. Allison found that a number of sources were polarized, and some had interesting rotation measure structure. Since only two frequencies were used in these observations, unambiguous rotation measure results could not be obtained, so these objects require more observations. In addition to creating beautiful images of these impressive radio sources, Allison looked into correlations with images at other emission bands such as the infrared and X-ray. We found that some sources which were presumed to be supernova remnants may actually be HII regions based on the infrared emission.

Green Bank, West Virginia (NRAO 43m and 100m Telescopes)

Students conducting their research at the NRAO Green Bank Site in West Virginia included Katrina Koski, Daniel McCoy, D. J. Pisano, Douglas Williams and Thomas Wilson. The program at Green Bank is under the direction of Dr. Ron Maddalena.

Daniel J. Pisano
Yale University
Worked with Jay Lockman

A Recombination Line Survey of Inner Galaxy Diffuse HII Regions.

D.J. Pisano, a junior from Yale, worked with Jay Lockman. He helped finalize the data from a recombination line survey of diffuse HII regions in the inner Galaxy. They then analyzed the data to derive the distribution of diffuse nebulae and to compare them with compact HII regions. Finally, they tried to estimate the distance to each object and derive the total luminosity that each contributes to the Galaxy. Interesting results were found. A paper is available.

Thomas J. Wilson
The University of Nevada at Las Vegas
Worked with Dana Balser

Combining Interferometer and Single-dish Continuum maps.

The data consisted of two sets of 11 continuum maps of classical HII regions at 8.7 GHz. The high resolution maps were obtained at the VLA in the D-array configuration. The single-dish maps were taken by the MPIfR 100 meter telescope to recover the zero-spacing flux. Tom Wilson made two major contributions: (1) he improved the signal-to-noise ratio of the VLA maps by self-calibrating the data; and (2) he combined the interferometer data with the single-dish data using the AIPS task VTESS, which uses the maximum entropy method. The results are much more sensitive and accurate maps of these regions. The primary goal is to use these maps to constrain models of the density and ionization structure of these HII regions.

Daniel McCoy
West Virginia Institute of Technology
Worked with Mike Stennes

An LO Reference Distribution System for Green Bank.

During the summer we designed, built, and (partially) tested an LO reference distribution system. The system provides transmission of precision reference frequencies to various points on the Green Bank site via phase monitored optical fiber. Daniel was given full responsibility of the round trip phase monitor module, and the clock synchronization circuit. The round trip phase monitor uses a mixture of digital and analog technology to measure the two-way propagation delay of a signal with an accuracy of much less than 1 picosecond. The clock synchronization circuit is a high speed (500 MHz) digital circuit. This circuit was designed by Daniel from scratch, and was particularly challenging as it required careful attention to layout on microstrip transmission line media. During Daniel's stay at Green Bank, he became familiar with all aspects of hardware development. Parts procurement, circuit design/fab/test, scheduling milestones, and cost estimating were all part of Daniel's assigned tasks.

Doug Williams
Stanford University
Worked with Rich Lacasse

GBT Active Surface Computer Design and Status Monitor.

Doug Williams worked for me this past summer and produced a great deal of very useful software. First he put together a status monitor for the GBT open loop active surface. It consists of a color coded display of all the actuators with the colors indicating their status. The package also actively queries the actuators to update the status and provides the ability to command all actuators. In addition, Doug produced a design for the master computer controlling the active surface, and implemented a fair amount of software for it.

David Ward
San Francisco State University
Worked with Mike Holstine

Plant Engineering


Katrina Koski
Lake Forest College
Worked with Glen Langston

Sky Survey at X-Band and with the Janksy Antenna.

Katrina worked on two projects this summer, analyzing the raw X band (3.6 cm) Green Bank Earth Station (GBES) Survey data, and helping with the experiments to test the Jansky Antenna. The GBES Surveys are intended to be full northern sky surveys at X and Ku (2 cm) bands. The surveys will monitor the sky, searching for short term variable sources, and monitor all the bright variable radio soruces. These surveys will be repeated at two week intervals. During the summer of 1995, the modifications were being made to the tracking station, which did not allow full Ku band data to be collected. Katrina wrote parts of a C program to edit the X band data, remove solar system objects and convert from Kelvins to Janskys. She used AIPS to grid the data into images, then identify radio sources. Some of the gridded images can be viewed. For example the galactic center region , covers right ascension range 16 to 20 hours, declination -30 to 33 degrees.

2002 Update: Koski obtained a BS in Physics and MS in Astronomy and works for an optical interferometry company in Socorro NM.

Tucson, Arizona (NRAO 12m and VLBA Telescopes)

Students conducting their research at the NRAO Tucson Site in Arizona included Frank Kolor, Larissa Bowles and James Wren. The program in Tucson is under the direction of Jeff Hagen. As the NRAO offices are across the street from KPNO/NOAO offices, the REU group shares in the activities of the NOAO REU program there.

Tucson summer students Jim Wren, Kelsey Johnson, Regina Jorgenson, Remy Indebetouw, Rain Winebarger, Reed Riddle, Larissa Bowles, Elena Neagu, Nadege Meunier, and Scott Clingenpeel (left to right) watch a (terrestrial) fireworks display from a vantage point above Tucson. Wren and Bowles were NRAO summer students, the others in the picture were from the NOAO summer student program. Photo courtesy Larissa Bowles.

Frank Kolor
Stanford University
Worked with Matt Waddel

Thermal Characteristics of the 12m Radiotelescope.

Frank Kolor labored intensively on a new sytem for monitoring thermal characteristics of the backup structure on the 12 meter telescope. This project included a circuit design and analysis, component specification and test, assembly, and installation. He was able to almost complete the project in the time alloted. There were only a couple of thermistors left to install and the circuit card needed to be programmed and installed. All of these tasks have now been completed and the system is functional.

Larissa Bowles
University of Virginia
Worked with Marc L. Kutner & Kathryn N. Mead

Molecular Clouds and Star Formation in Different Galactic Environments.

Though it is generally understood that massive star formation takes place in giant molecular clouds (GMCs), there is still no clear picture of how these clouds are formed or under what conditions star formation is initiated. We can help address these questions by studying molecular clouds and star formation in different galactic environments. To do this, we can study different parts of our own Galaxy or look at other galaxies. In studying other galaxies, telescope resolution limits us to ones in the Local Group: the Large and Small Magellanic Clouds and the Andromeda Galaxy, M31.

This project involved observations of CO(J=2-1) (1.3mm) emission from a section of M31 believed to have strong magnetic fields (to tell us something about the relationship between magnetic fields and star formation). The observations were carried out in May 1995 on the 12m telescope, located on Kitt Peak. A 4' x 4' region was mapped using a new technique, On the Fly (OTF) mapping. In OTF mapping, data are taken continuously as the telescope is scanned across the source (rather than simply stopping the telescope at each position to be observed). OTF produces higher quality images, and takes less observing time, but provides some challenges in data reduction.

Ms. Bowles used the Astronomical Image Processing System (AIPS) to process the data. The major tasks involved combining the 70 maps of the region into a single map, detecting and deleting bad data, arranging all of the observed points onto a regular grid and collecting the results into a data cube that could be further analyzed. For example, by picking out emission in different velocity ranges, she could isolate emission from different parts of the region. The results of this work will be presented as a poster at the next AAS Meeting.

Ms. Bowles wrote a beginners handbook for anyone using AIPS to do OTF mapping for the first time. This handbook will be useful to anyone with no or limited prior knowledge of AIPS. This handbook will be incorporated in more extensive NRAO documentation.

James Wren
New Mexico Institute of Mining and Technology
Worked with Darrell Emerson and Phil Jewell

Pointing Characteristics of the 12m Radiotelescope.

This summer I worked with Phil Jewell and Darell Emerson on the analysis of structural tilt and pointing offsets of the 12-m radio telescope on Kitt Peak. Most of my project consisted of writing routines in PV-Wave for analysis of the data coming from the tilt meters and pointing calibration files. PV-Wave is a mathematical analysis package similar to IDL. Over the summer I used it to write many routines to reduce and display the data. Using these tools it may be possible to determine any periodic offsets in the pointing of the 12-m not compensated for in the current model. It may then be possible to add additional terms to the pointing equations that will be able to adjust the pointing model to obtain a better fit and therefore reduce pointing error.

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