1999 Research Experiences for Undergraduates Program

NRAO National Radio Astronomy Observatory
1999 is the 40th Anniversary of the NRAO Summer Student Program!
Research Projects by NRAO Site


Charlottesville, Virginia (NRAO Headquarters)



There were five students in the 1999 Summer Student Research Program, three of them under the 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 are intended to aquaint the students with the research which various staff members carry out. The lectures are listed below.




1999 Summer students from Green Bank and Charlottesville met at a get-together with mentors and lecturers in Charlottesville.

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 1999 students enjoy an informal get-together with astronomers from the University of Virginia and NRAO at lunch. followed by a visit with graduate students from the University's Astronomy Department.

The students wrote a Target of Opportunity proposal to measure OH in a comet which was awarded time. As a consequence, they observed at the 43m telescope in Green Bank, which closed this summer. They observed OH in C/1999 H1 (Lee) (above, seen on 20 May by Seiichi Yoshida). Water is the dominant consitituent of comets but is unobservable owing to the earth's atmosphere. However, its photodissociation product OH can be observed with the 43m telescope. From that, the waqter production rate may be measured. We did this and published the result in the IAU Circular No. 7233:

Comet C/1999 H1 (Lee)

P. Mason, C. Murray, D. Bambic, J. Durbin and A. Wootten (NRAO) report that the OH 18-cm transitions were detected toward comet C/1999 H1 (Lee) at the NRAO 140-ft telescope in Green Bank, WV on 1999 May 25th. The 1667 MHz line was measured with a line area of 0.062 +/- 0.007 K km/s in antenna temperature; the 1665 MHz line was measured at 0.026 +/- 0.008 K km/s. The 1667/1665 ratio of 2.4 reasonably matches the expected line ratio of 1.8. Assuming an OH lifetime of 2 x 10**5 s, the line measurements give a water production rate of 5.5 x 10**28 s**-1.


Later in the summer, the Charlottesville students visited Green Bank again to tour the NRAO telescopes located there, to meet members of the Green Bank staff, and to attend the annual picnic.

One highlight was the placing of the panels onto the Green Bank telescope ( GBT ), the world's largest steerable telescope. It is an offset parabaloid, 110m across the longest axis, incorporating 16 million lbs of steel in the moving structure. The surface is more than half complete on the structure; during the rest of the year it will be completed. In Green Bank for observations, the students got to watch the process.

The 40 ft telescope there is a student telescope, open for any project which students would like to carry out on it (though its instrumentation is limited). If there is interest, we may carry out, probably remotely, a project on the VLA or 12m telescope in Tucson.

We're very excited about the Atacama Large Millimeter Array, which was selected as the top priority for a new astronomical instrument in the 90s back at the beginning of the decade by the Astronomy Survey Committee. Students got to see it take shape as the second year of design and development gets underway.

The students gave a series of 15 minute talks on their projects during a lunch symposium in Charlottesville before they begin leaving for the summer. They produced short reports describing their summer research.


1999 Summer students from Charlottesville and their mentors at the 1999 Summer Student Research Symposium. Left to right: John Hibbard, Chris Power, Jack Gallimore, Jonathan Durbin, Dustin Bambic, Cristina Murray, Porter Mason, Michele Thornley and Barry Turner.

On August 11, 1999, the last total eclipse of the millennium occurred. Although totality was most easily viewed over the Atlantic through Europe to India, the path began over the Eastern Shore of Maryland and Virginia about 20 minutes before sunrise. Reliving eclipse expeditions of old, we decided to see if we could see any effects of totality before the shadow actually hit the Earth. Possibilities included a delayed twilight followed by sudden dawn and the rise of the partially eclipsed sun. The interpretations of our observations was somewhat muddled by the passage of a line of strong thundershowers just before 'totality'. However, we convinced ourselves that we had, in fact, seen a delayed twilight. On the return, we took a scenic route through historic Oxford and St. Michaels Maryland.


Students (l-r) Dustin Bambic, Chris Power and Cristina Murray on the auto ferry from Oxford to Bellaire cross the Tred Avon River (about half water and half stinging nettles at this time of year).

CV Summer Student Schedule, Summer 1999

Date Person Item Location Time
17 May open Students begin arriving
19 May R2D2 Star Wars Opens Carmike 12am
19 May Wootten Welcome NRAO,Room 317, Stone Hall 9am
21 May Wootten Radiotelescopes and Radioastronomical JargonNRAO,Room 317, Stone Hall 9am
21 May open Public Night at McCormick Observatory at the Observatory 9pm
24 May Wootten Preparation for Observing--From Antenna Temperature to Science NRAO,Room 317, Stone Hall 9am
25 May Wootten Leave for Observing NRAO,Room 317, Stone Hall 9am
25 May Wootten Observing, 43m telescope Green Bank, W. Va. 1pm
25 May Wootten Observing ends, 43m telescope Green Bank, W. Va. 9pm
26 May Wootten Return to Charlottesville Green Bank, W. Va. 8am
28 May Kellerman The Development of Radio Astronomy NRAO,Room 317, Stone Hall 9am
2 June Condon Radio Sources NRAO,Room 317, Stone Hall 9am
4 Jun open Public Night at McCormick Observatory at the Observatory 9pm
9 June Turner Interstellar Chemistry NRAO,Room 317, Stone Hall 9am
14 June Beasley Interferometry NRAO,Room 317, Stone Hall 9am
16 June Liszt The Interstellar Medium NRAO,Room 317, Stone Hall 9am
18 June Matthews HI in Nearby Galaxies NRAO,Room 317, Stone Hall 9am
18 Jun open Public Night at McCormick Observatory at the Observatory 9pm
19 June All NRAO Summer Picnic McIntire Park Shelter No. 3 1:30 pm
21 June (tent) Wells The Green Bank Telescope NRAO,Room 317, Stone Hall 9am
23 June Hogg Radio Stars NRAO,Room 317, Stone Hall 9am
25 June Thornley Molecules in Normal Galaxies NRAO,Room 317, Stone Hall 9am
28 June McMullin Interstellar Molecules NRAO,Room 317, Stone Hall 9am
30 June Gallimore Active Galactic Nuclei NRAO,Room 317, Stone Hall 9am
2 Jul open Public Night at McCormick Observatory at the Observatory 9pm
7 Jul Garwood AIPS++ NRAO,Room 317, Stone Hall 9am
12 Jul Wootten Star Formation NRAO,Room 317, Stone Hall 9am
16 Jul open Public Night at McCormick Observatory at the Observatory 9pm
TBD Bradley Central Development Lab Introduction Rm 228 Ivy Road 9am
TBD Bradley Tour of Central Development Lab Rm 228 Ivy Road 10am
TBD Lunch with U. Va. NRAO,Room 317, Stone Hall 12pm
TBD Bradley Tour of U. Va. Device Fabrication Facility U. Virginia 1:20pm
TBD Wootten BBQ for CV, GB REUs and mentors Wootten Home 6pm
24 July All CV REUs -> Green Bank Picnic Green Bank, W. Va. noon
28 July van den Bout TBD NRAO,Room 317, Stone Hall 9am
3 Aug Students REU research presentations Rm 317, high noon
4 Aug Hibbard TBD NRAO,Room 317, Stone Hall 9am
6 Aug Hibbard TBD NRAO,Room 317, Stone Hall 9am
6 Aug open Public Night at McCormick Observatory at the Observatory 9pm
20 Aug open Public Night at McCormick Observatory at the Observatory 9pm



>

Cristina M. Murray of University of New Mexico
works with Jack Gallimore
on

Black Holes in Active Galaxies

Active galaxies (AGNs) are thought to be powered by accretion onto a central, massive black hole. Seyfert galaxies are the nearest AGNs that show all of the classic signs of activity, including radio jets, broad optical line emission, hard X-ray emission, and rapid variability. They are indistinguishable from quasars except that they are nearer and less luminous. Recent VLBA observations have demonstrated that the radio emission from a Seyfert nucleus is, however, peculiar. The nuclear radio properties may owe to thermal processes in gas located very near the massive black hole (i.e., a few light years from the AGN).

I have several projects investigating peculiar radio sources in Seyfert nuclei, two of which are naturally suited for summer student research. One is a VLA survey of high frequency (22 and 43~GHz) emission from Seyfert nuclei. The goal is to locate potential flat-spectrum sources and address the effects of thermal free-free absorption (or possibly emission). There are currently data for 13 sources in hand, and we anticipate having an additional 15 sources this summer (TAC-willing). The other is a VLBI survey of nearby Seyfert galaxies. The main goal of the VLBI project is to investigate the Seyfert radio jets at a spatial resolution of ~ 1 light year. We will be receiving snapshot VLBI data for 8 sources this spring.

Both programs are technically challenging, and the summer student can expect to come away with an advanced understanding of aperture synthesis techniques. The student might choose either to concentrate on complete reduction of the survey data, in which case he or she will receive co-authorship on the survey paper, or to focus on the analysis and interpretation of a specific source and assume lead authorship.


Dustin Bambic, of Western Kentucky University
will work with Michele Thornley
on

NGC 7331: Characterizing the contribution of spiral density waves in flocculent galaxies

My summer with NRAO in Charlottesville began as smoothly as one could hope, even though I was completely unfamiliar with our subject, flocculent galaxies. I had just finished school a week earlier, allowing little preparation time. Michele began the summer with discussion of our project, data, goals, and motivation. In short, galaxies with large-scale spiral structure are thought to contain spiral density waves. A spiral density wave is a compression wave that is able to organize a galaxy’s constituents, forming spiral arms. However, not all galaxies have a large scale spiral design. Another galaxy type, flocculent galaxies, has a disc like the grand-design spirals, but no arms are visible in optical light. Due to their lack of organization, flocculent galaxies have been assumed by some of the astronomical community to not contain spiral density waves. In addition, the topic draws very little attention, and little data is available to those who wish to investigate the matter. So, Michele made this her doctoral thesis topic, investigated several flocculents, including the prototypical flocculent galaxy, NGC 5055, and found conclusive evidence for density wave presence in a few of them. She wished to continue this work, and turned the telescopes toward another flocculent, NGC 7331. Michele was granted 15 hours of observing time with NRAO’s Very Large Array, and the data was safe in hand well before the summer. She soon turned her efforts toward new topics, with the NGC 7331 data set unreduced.

As an undergraduate interested in astronomy, I applied to NRAO’s summer REU program, and other REU programs, in January 1999. In March, NRAO offered me a position in Charlottesville, and I quickly accepted. I had been chosen by Michele to help reduce her aforementioned data set.

I immediately began my background readings, consisting mostly of astrophysical and astronomical journals, spanning the spiral galaxy formation process, spiral form maintenance, galactic surveys, galactic kinematics, galactic interactions and mergers, and of course an introduction to radio astronomy. In addition, the other summer students and I attended a few lectures a week concerning other astronomical topics, each about an hour long, and each by a different NRAO scientist. This introductory time was focused yet unhurried, and perhaps the most learningful period of my life. After only a few weeks, my view of the universe had changed considerably. Suddenly galaxies were dynamical, evolving systems, and the cosmos was much more exciting.

Soon, however, it was back to earth and into the world of AIPS and LINUX. UNIX is an operating system. Prior to NRAO, I may have thought the whole world was either Windows or Mac. However, my eyes were shown additional operating systems, UNIX/LINUX and SUN OS, and my digital adventure was underway. But, not before I was shown AIPS, and opened to what real radio astronomy consists of. AIPS is the data reduction program used for reduction of data collected by NRAO telescopes. Data from observations is stored onto DAT tape, and AIPS enters when you’re ready to read and/or edit the data. AIPS consists of tasks and verbs used to configure your data, and with AIPS, bytes are turned into actual images of your object. Initially, I was very intimidated by both AIPS and LINUX, but as my stay at NRAO advanced, I became much more confident in my understanding of both, or at least the parts of each we used.

The data set came in three main sets, each corresponding to a different antenna configuration used to obtain the data. Different configurations provide information on different size scales. However, the reduction process is basically the same for each. Michele and I went through the first data set together, taking notes the entire time so that I could repeat the process by myself. However, it was not thoughtless replication. Each data set is different, almost taking on a character. Each had its own problems, requiring data interpretation and troubleshooting until the final image was satisfactory. The first eight of my twelve week stay at NRAO consisted of this reduction process, until three final images were obtained, one from each configuration.

These three images served as the base of all our further investigations. The three images were combined to create one “mother image.” From this image, we were able to create velocity maps, density maps, major and minor axis velocity slices, and zooms of each, corresponding to different regions of NGC 7331. Again, we used each to look for density wave signatures in NGC 7331. We were not the first to look at NGC 7331 with density wave detection in mind. A previous group had used optical means to search for density waves, and claimed to detect density wave perturbations along the western side of the galaxy. We investigated the same region, and the rest of the galaxy. Interestingly, we could not confirm the wave detection along the western side of NGC 7331, but found more significant perturbations along the southeastern side of the galaxy. This final analysis process, along with my preparation for the final presentation of our research to the NRAO staff, occupied the last four weeks of my stay in Charlottesville, and before I knew it, the summer was over.

My summer at NRAO was as pleasing an experience as I could have imagined. I formed great friendships during my stay. I experienced the reality of astronomical research. I saw what astronomers do all day, what they eat, what they talk about, and even how they drive. My plans before NRAO included attending an astronomical graduate program. After my summer at NRAO, these plans have solidified. In fact, I plan to pursue astronomy more than ever. Perhaps I’ll have a summer student working under me some day.


Porter Mason , of Duke University

works with Barry Turner
on

The 2mm Spectral Survey

Mr. Mason worked on preparing Turner's 2mm survey for presentation on the WWW. The input to the problem is (i) the observed spectra in tabular form (the form to be determined); (ii) and catalog of computed spectral lines including Lovas, JPL, and my own calculations; (iii) tables of spectral line parameters measured by me from the spectra. The problem will be to provide a WEB setup that allows the user to click on a given spectrum, and obtain several features including (i) a plot which with cursor control may be scaled in both axes, over a chosen frequency range; (ii) may be linked to the atlas of computed lines with which any selected line on the plot may be searched and labelled if a match is found; (iii) contain most of the elementary features of Unipops or AIOS++ such as rms (requiring designation of baseline parameters); perhaps gaussian fitting; 0th moment measures, etc.

The result may be viewed here.


Jonathan Durbin , of
Valdosta State University
works with Richard Bradley
on

Wideband Balanced Amplifiers

Mr. Durbin helped to design wideband balanced amplifiers for operation in the 1-6 GHz band. Specifically, we need to develop multi-octave hybrid couplers. The student will learn about the operation of such components and then use computer-aided design tools to simulate their performance. Test structures will be fabricated and evaluated.


Chris Power, of Trinity College, Dublin
works with John Hibbard and J. Barnes (IfA)
on

N-body Simulation of "The Antennae"

Collisions between galaxies can be dealt with analytically only in very specific cases. Unfortunately, the conditions that are prevalent in the bulk of galaxy interactions rarely satisfy these idealisations and so, when considering such situations, the researcher must make use of N-Body simulations to model the encounters. In general, pictorial representations of the time evolution of such encounters is desired.

In this report, I will discuss my work in this area; in particular I will concentrate on how I developed a means to convert observational and simulation data into a form that is readable by the interactive 3 dimensional visualization tool, Geomview. I will also describe my work on the matching of simulation and observational data for the case of NGC 4038/9, the "Antennae", as well as the motivation for such model matching and the characteristic features of a system that are particularly suited to such fitting.

As an interesting aside, I indulged myself and present brief discussions on The History of Mergers and previous attempts to model the "Antennae" in Numerical Models of NGC 4038/9. My work may be reviewed here.











NRAO/Socorro 1999 Research Experience for
Undergraduates (REU) Program







1999 Summer students from Socorro visit the NRAO-Kitt Peak 12m telescope. (left to right, standing)Allison Coil, Liz McGrath, Bryan Jones, Niruj Mohan, Crystal Brogan, Chad Young, Colleen Schwartz, Makenzie Lystrup, Hannah Smith, (sitting) Darrell Osgood, and Teddy Cheung at the 12-meter NRAO telescope.



The summer REU program at NRAO/Socorro in 1999 consists of 4 main categories of activity:

1 - student research projects, in collaboration with an NRAO advisor
2 - lectures to the students by NRAO staff members
3 - a joint student project, involving observations with the Very Large Array (VLA)
4 - guided tours of the VLA, given by the students on weekends


The 1999 REU program at NRAO/Socorro is under the direction of Liese van Zee , Chris Fassnacht and Greg Taylor. Drs. van Zee and Fassnacht are Jansky Postdoctoral Researchers at NRAO/Socorro, and Dr. Taylor is a member of the scientific research staff. Please visit the NRAO/Socorro Summer Student Page.






Lectures, etc...


Several lectures about radio astronomy and interferometry will be presented, allowing the students to obtain a good understanding of the technique. Talks were also given on general topics in astronomy, presented by members of the scientific staff. The astronomy talks were designed to give the students an understanding of what sort of research goes on at NRAO, and in radio astronomy in general. The detailed list of lectures and events for the summer is in the following table. 






1999 Calendar of Events -- New Mexico

This is the list of 1999 student lectures and other organized events for the summer students.

1999 Summer Student Calendar of Events

June 1999

July 1999

August 1999


Last update: July 18, by LvZ







The VLA is in A configuration this summer. Three hours of telescope time have been allocated to the summer students to pursue group projects.

  • A Study of Water Masers

  • HI Absorption towards PDS 456

    Last Modified on Aug 11, 1999

    Planned Trips

    Kitt Peak/Tucson - June 21-23.

    The NRAO/AOC summer students embarked on a trip to Kitt Peak, where they visited the NRAO12m telescope, the NRAO/Tucson REU students, and the NOAO facilities and summer students.

    Trip Itinerary


    0700, June 21 - leave Socorro
    1100, June 21 - lunch in Lordsburg
    1430, June 21 - tour of NRAO 12-m antenna (by Jeff Mangum)
    1630, June 21 - dinner @ KP cafeteria
    1700, June 21 - tour of optical telescopes (by Nigel Sharp)

    1000, June 22 - KP-VLBA antenna tour (by Nick Jesch)
    1130, June 22 - leave for Tucson
    1300, June 22 - lunch
    1430, June 22 - tour of NRAO Tucson (by Jeff Mangum)
    1600, June 22 - free time to explore Tucson/U of A
    1900, June 22 - dinner at Caruso's Italian restaurant

    1000, June 23 - breakfast, check out of hotel
    1100, June 23 - tour of UA mirror lab
    1230, June 23 - lunch at Eric's
    1400, June 23 - leave Tucson for Socorro
    1900, June 23 - short walk along the Catwalk, Glenwood, NM
    2300, June 23 - arrive in Socorro


    Click here to see pictures of this year's trip.


    Other Stuff

  • A Basic Information Letter is available from the WWW pages.

  • A more complete picture page on the WWW shows snap-shots from the summer.










    Student Research Projects




    Each of the REU students will work with one or more advisors on one or more projects throughout the summer. This is the main focus of the program, and the majority of the students' time will be spent on these research endeavors. These projects involved observing, data reduction and analysis, equipment development, and theoretical studies. At the end of the program, each student gave a lunch talk explaining the main project(s) he or she worked on during the summer. The possibility exists for the students to present their original research at scientific meetings deemed appropriate by their advisor(s). Following is a detailed list of the specific projects carried out by the NRAO/Socorro REU students:


    Darrell Osgood of New Mexico Institute of Mining and Technology
    works with Frazer Owen
    on

    Evolution of Populations of Radio Galaxies in Clusters

    Using the existing deep VLA radio images for 6 clusters of galaxies with z between 0.25 and 0.41 and existing optical imaging (ground-based and HST),the student would make the optical identifications. The student would use these data, along with existing optical spectroscopy to estimate size of the radio populations in each of these clusters and whether the radio galaxies were likely star-formation driven or AGN's. These data would then be compared with lower redshift results to evaluate the evolution of these populations with redshift and other cluster properties.


    Teddy Cheung of Brandeis
    works with Jim Ulvestad
    on

    ARISE Imaging

    Space VLBI missions have unique imaging requirements relative to ground VLBI. For the highest resolutions, there typically are large holes in the (u,v) plane, both due to the high spacecraft orbit and to intermittent tracking. Also, high sensitivity is required, but the space telescope cannot nod back and forth between sources due to a limited slewing capability, making phase referencing impossible for the space element. These two issues should be addressed in order to provide better imaging for the future ARISE mission. Either problem is reasonably well-defined, and could be completed in a summer term, assuming a well-prepared student with some AIPS and radio interferometry background. The proposed approaches are outlined below, with the final selection to be made based on the student's and advisor's negotiation. Item (1) is probably a more tractable problem for a summer, although item (2) might also be possible. (1) Explore techniques in AIPS and/or DIFMAP for imaging of ARISE data having large holes in the (u,v) plane. The approach would be to take on-hand VSOP data from my projects or other observations, then create (u,v) holes of varying sizes by deleting antennas giving long ground spacings (e.g., use the southwestern VLBA stations plus HALCA). The data would be used to examine techniques for fringe-fitting, self-calibration, and data weighting in order to find the best range of parameters, the limitations to dynamic range, and the inflection points at which the images begin to degrade rapidly. Simulated data might also be used.

    (2) Investigate the possibility of phase-referencing the ground telescopes at high frequencies, while keeping ARISE pointed at the program source, in order to increase the coherent integration time and the detection threshold. There are two possible approaches, either through the acquisition of VLBA test data with most (but not all) of the antennas phase referencing, or by generation of simulated data with such an observing strategy. Currently, the latter strategy is favored, because real test data would still have an atmosphere above the VLBA antenna that is not phase referencing; the whole point of the project would be to test phase referencing for an antenna that cannot slew, but also has NO atmosphere.


    Colleen Schwartz of Colby College
    works with Joan Wrobel
    on

    SYMMETRIZATION OF THE RELATIVISTIC JETS IN M84

    The elliptical galaxy M84 hosts an FR I radio continuum source and a dusty, warped optical emission line ``disk''. HST imaging shows that the inner dust distribution is not relaxed, but filamentary and complex. We have a VLA image of M84 at 4.9 GHz with a resolution of 500 mas (36 pc) FWHM, showing that the two large-scale jets in M84 are initially asymmetric: the ratio RI of the intensity of the northern main jet to the southern counterjet exceeds unity. However, these jets symmetrize ( RI) by a projected nuclear offset rp (950 pc). Is this VLA symmetrization trend consistent with Doppler boosting in a decelerating, but initially relativistic, jet characterized by a (slowing) jet fluid velocity and a (constant) line-of-sight viewing angle ? To test this, we obtained VLBA images of M84 at 1.7 GHz and 8.4 GHz, with resolutions of 11 mas (0.80 pc) and 1.9 mas (0.14 pc), respectively, and used them to evaluate RI on pc scales for comparison with RI on 100-pc (VLA) scales. These comparisons imply: (a) RI > 15 at  pc and  pc, requiring and at these locations. (b) RI drops gradually between  pc and  pc, as expected if twin relativistic jets smoothly decelerate. (c) RI drops rapidly between  pc and  pc, suggesting an abrupt slowing of the jet at this distance. Indeed, the main jet morphology at  pc resembles an oblique shock. Furthermore, although the main jet is not initially perpendicular to the dust layer seen by HST, a clockwise deflection of the jet at  pc brings it into closer alignment with the normal to the layer. This hints that the optical line-emitting gas and the dust in M84 trace the medium initially entrained across the jet's boundary layer, both abruptly slowing the jet and deflecting it toward the normal to the gas/dust layer. These preliminary results were reported at IAU Symp. 175 in 1995 October.


    Andreea Petric, of Columbia University and NMIMT
    works with Michael Rupen
    on

    Multi-object Spectroscopy of the Cluster CL0939+47

    Multi-object spectroscopy of objects in this z=0.4 cluster was undertaken to determine how important dust extinction is in moderate redshift clusters, and to clarify galaxy type in clusters at 0.3


    Niruj Mohan , of Raman Research Institute, Bangalore
    works with K. Anantharamiah
    on

    Recombination Line Emission from Starbursts

    Niruj will work mainly on VLA spectral line data from two proposals AN81 and AM614. This will form the basis of his Ph.D. thesis. If time permits, he will also work on VLBA continuum data on PKS 1830-211 (at 90 and 50 cm) from the project BA031.

    AN81 is a VLA proposal to study Recombination line emission near 8.5 GHz from a variety of starburst galaxies: a Wolf-Rayet Galaxy (He 2-10), a blue compact Dwarf (NGC 5253), an interacting system (NGC 1808) and two merging systems (NGC 4038 and VV 114). This proposal was awarded a total of 38 hours of VLA time (14 hrs in CnB, 4 hrs in C, 16 hrs in DnC and 4 hrs in D configurations). The CnB and C array observations were made in Nov/Dec 98 and is awaiting data reduction. The remaining obsevations will be made sometime during during Mar-Jun 99. These proposals were prepared by Niruj and the observe files were also made by him.

    AM614 is a VLA proposal that Niruj wrote to followup our earlier detection of RRLs from two well known starburst systems, IC694 and NGC 3628. Models for line emission that were made based on the detections at 8.5 GHz, predicted a strong variation of line strength with frequency. It is crucial to study higher frequency RRLs to constrain the models. This proposal is for observations of RRLs at 2 cm and has been awarded a total of 16 hours of VLA time in the D-configuration. I expect that these observations will be made when Niruj is visiting Socorro and thus he will take care of all aspects of these observations.

    Another project that Niruj is involved in, and which is only peripherally related to the main theme of his thesis, is search for RRLs at 20cm from the gravitational lens system PKS1830-211 (VLA proposal AA220). To study the effect of intervening ionized gas (due to free-free absorption and scattering) on the continuum structure of PKS 1830-211, we have obtained a 10 hr VLBA observation (Program BA031) at 90 cm and 50 cm. If time permits, I will ask Niruj to work on this data as well while he is here. This will provide him (and me) valuable experience with low-frequency VLBA data.

    Niruj is already proficient in preparing VLA observe files and spectral line data reduction using AIPS. I therefore expect him to get started as soon as he arrives. A large amount of data, all produced through his proposals and which will become part his Ph.D thesis, will be waiting for him when he arrives. He will greatly benifit from a summer studentship in 1999.



    Crystal Brogan , of The University of Kentucky
    works with Dale Frail
    on

    1720 MHz Zeeman Observations of OH Masers Toward SNRs

    Ms Brogan will be working with Drs D. A. Frail and W. M. Goss on an effort to perform 1720 MHz Zeeman observations of OH masers toward galactic supernova remnants. The 1720 MHz transition has proven to be a powerful probe of supernova remnant interactions with molecular clouds. The 1720 MHz line also exhibits the Zeeman effect, allowing for the magnetic field strength to be measured in these regions for the first time. The goal of this project will be to increase significantly the small number of such measurements in order to accurately model the role of magnetic fields in molecular shocks.


    Chad Young of Mississippi State University,
    works with Dale Frail
    on

    Afterglows from Gamma-ray Bursters

    The goal is the detection of long-lived afterglows from gamma-ray bursters at radio wavelengths. The study of these afterglows in the radio yields unique diagnostics not obtainable by any other means. In particular radio observations give the size and allow one to infer the expansion of the relativistic fireball that is produced in the burst.

    A student might be expected to work on several things including (1) the monitoring of known radio afterglows (2) searching for radio emission from new bursts, (3) modeling the flux evolution of the synchrotron-emitting fireball, (4) developing observing/reduction code to simplify the process of obtaining radio data on GRBs. Depending on the student's talents I can see this as a pure observing project, a theory project or a partial software project. The detection of an afterglow would almost certainly involve the publication of paper.


    Hanna Smith , of Smith College,
    works with Greg Taylor
    on

    Compact Symmetric Object 1946+708

    The Compact Symmetric Object 1946+708 was the first extragalactic source in which bi-directional motions were directly observed (Taylor & Vermeulen 1997, ApJL, 485, L9). This offers a unique chance to measure H$_0$. Along with Rene Vermeulen, I have obtained multi-epoch VLBA observations of 1946+708 at 8 and 15 GHz. Our program will also measure the advance speeds of the hot spots, from which we will obtain the age of the source. The past year has seen the first such direct measurements of the hotspot advance speed in extragalactic radio sources (Owsianik, Conway & Polatidis 1998, A&A, 336, L37; Owsianik & Conway 1998, A&A, 337, 69). The high reported velocities (0.25 c) in the Compact Symmetric Objects 0108+388 and 0710+439, give ages of order 1000 years, reinforcing the idea that these objects are compact by virtue of their youth and are not confined ("frustrated") by a dense environment. A velocity of 0.25 c (0.06 mas/yr) will be readily detectable by our monitoring observations. The basic work for a summer student would be to calibrate and image four VLBA epochs at 8 and 15 GHz on 1946+708 and to determine the motions of the jet components and especially the hot spots. A summer student working on this project would learn about the physics of Compact Symmetric Objects, and about the reduction and analysis of phase-referenced VLBI data. The goal for the student would be the publication of a paper in the ApJ and presentation of the results at a AAS meeting or other suitable conference.



    Elizabeth McGrath of Vassar
    works with Miller Goss
    on

    Water and HII in the Giant HII Region W49

    Miller Goss: Chris De Pree and I have started a program to determine the relative positions of H2O and continuum components in the giant HII regions Sgr B2 and W49. The observing technique is to do simultaneous continuum and H2O observations ( both IF's ). We self cal on the strong H2O masers and then can detect the weak 1.3 cm continuum components at high resolution ( 0.2 arc sec or so in the B array). The data reduction is complete for Sgr B2 and just started for W49. The relative positions can be determined at the level of 0.001 arc sec or so due to the favorable signal to noise. An REU student can bring this program to completion.



    Makenzie Lystrup of Portland State University
    works with Craig Walker
    on

    Phase Referencing with the VLBA: Structure and Motion of 3C120

    I would have the summer student work on a test of some aspect of phase referencing with the VLBA. Phase referencing is, of course, critical to high sensitivity on the VLBA. It is one of the two main focus areas in VLBA testing at the moment (the other is 3mm). The exact details of the project may vary depending on what others do between now and then and on the status of some old phase referencing tests. But my current idea would be to test various aspects of the use of multiple calibrators to improve the quality of reference results. Very early in the summer, or perhaps before the student gets here, a test project would be observed and correlated. In the test, several calibrators in a cluster, plus a few others around the sky, would be observed. All would be strong sources with very well known positions. Using those data, we would look for the most effective, and easiest, scheme to use to improve the accuracy of referenced phases.

    Bryan Jones, of
    works with Rick Perley
    on

    Ionospheric Correction Using A Dual Frequency GPS Unit

    I think I have a cool project for an REU student -- working with our brand new dual frequency GPS unit. It looks as though the software support promised by the software group will be a little late in showing up. We could probably use a student to help us learn how to use the device. It is run from a PC running Windows NT, and does lots of cool things. So, I think we can offer this as a project. Once we get the receiver up, and the software loaded, more experiments with polarized pulsars will be needed to finish the project.



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

    Students conducting their research at the NRAO Green Bank Site in West Virginia included the students in the list below, along with others. The program at Green Bank is under the direction of Dr. Ron Maddalena.

    1999 Summer Student Steve Hicks meets Senator Robert Byrd on the occasion of his visit to the Observatory.

    1998 Summer and co-op Students and NRAO staff members after a caving trip (L-R): Frank Ghigo, Jennifer Lockman, Pat Matheny, Ron Maddalena, Nicole Wiersgalla, and Steve Hicks. 







    


    1998 Calendar of Events -- West Virginia

    The following lists the scheduled activities for the GB students:
    May 7, 12, and June 2 -- Student Orientation and tours

    June 1998


    July 1998


    The dates might vary slightly from the above. The time and place might also vary but will usually be at 3:00 in the conference room in the new wing.

    Scott Zmerick, of West Virginia University
    works with Ron Maddalena and Sue Ann Heatherly
    on

    A 40 Foot Upgrade


    We are currently updating the control interface and receiver system for the 40-ft educational telescope. A programming student is needed to complete the graphical user interface to the telescope system.

    Steve Hicks, of
    works with Dan Pedtke
    on

    An OVLBI Controller

    OVLBI and NRAO is to complete the design of our new Peltier controller. This is a 90% hardware and 10% software project, so it would be good to have an EE as opposed to a CE. I think it could be finished in a summer and would help all on the site. There are a few other small things as well, one would be capturing schematics, updating our documentation - pretty boring for most people but a student might be into it.


    Christopher S Deyoung , of University of Houston
    works with Steve White
    on

    Test Dewars for Radioastronomy Instrumentation

    A project in the cryogenics lab. An automated system for characterizing and logging the cooling capacity of the various refrigerator needs to be designed built and tested. This would be a nice summer long project which could be carried through form design to completion during the summer months. What I have in mind is a test dewar(s) with variable loads on the first and second stages of the refrigerators. A computer controls the energy applied to each load and graphs a load diagram for the particular refrigerator. This project entails thermodynamics, electrical engineering and writing code for the PC.


    Jill C. Kamienski , of University of Colorado, Boulder
    works with Frank Ghigo
    on

    Green Bank Interferometer Upgrades

    The project will involve programming in C or C++ for the Green Bank Interferometer project. It can involve either 1. Developing software for control of two 85-foot telescopes, in a vxWorks environment. The software would generate commands for moving the telescope to desired positions, would monitor the positions and other status information, and would write the status data in a log file. or 2. Developing a system for on-line editing and analysis of data from the Interferometer. Perhaps this will include an automated way of identifying radio sources that are flaring or exhibiting unusual behavior, and of identifying hardware problems.


    David Sand, of UCLA,
    works with Jim Braatz
    on

    Distant Megamasers

    The student and I will address the question of whether water megamaser sources are preferentially detected in AGNs with highly inclined galactic disks. Such a trend was detected at early stages of the maser surveys, and it can now be updated with survey results from the past two years, and the question addressed more confidently. The project will involve collecting, cataloguing, and analyzing properties of galaxies which have been observed for water. Statistical comparisons of the detected and undetected populations will then be pursued.


    Jeanine Wilson , of The University of Washington,
    works with Dana Balser and Toney Minter
    on

    Diffuse Ionized Gas in Galaxies

    The summer student will work on modelling the diffuse ionized gas of galaxies. Models of ionization levels of different atoms will be computed using the program CLOUDY for many different types of stars and differing ISM characteristics around these stars. The results from the CLOUDY models will then be used to model a galactic disk. These models will then be compared to the galactic disk of the Milky Way and other galaxies with extended emission from diffuse ionized gas such as NGC 891.




    Tucson, Arizona (NRAO 12m, ALMA and VLBA Telescopes)

    Two REU students conducted research at the NRAO Tucson site in Arizona during the summer of 1999. The program in Tucson is under the direction of Jeff Mangum. 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.




    1999 Summer students get a tour of the 12m from Jeff Mangum.

    In addition to the general activities carried out at the KPNO/NOAO offices, the NRAO and KPNO/NOAO REU students participated in two group activities organized by the NRAO staff. The first was a night at the 12 Meter Telescope, where the REU students spent a day at the 12 Meter Telescope. Following a tour of the telescope and lab facilities, where the students were introduced to the instrumentation used in millimeter wavelength astronomy, the students were given the opportunity to participate in some actual millimeter wave astronomical observations. With this experience the students got an introduction to the observing techniques used in millimeter wavelength astronomy.

    The second general activity was a lecture series on millimeter wavelength astronomy given by members of the NRAO scientific staff. Three lectures were given. Jeff Mangum gave a presentation on millimeter wavelength research into the properties of objects in the Solar System and molecular clouds. Darrel Emerson gave a lecture on millimeter wavelength observing techniques. Finally, to complete the survey of millimeter astronomy, Simon Radford gave a lecture on extragalactic astronomy at millimeter wavelengths.




    1999 Summer students get a tour of the 12m from Jeff Mangum.

    The following are detailed reports describing the work done by each REU student at NRAO Tucson.



    Sean Andrews, of Northwestern University
    works with Jonathan Williams
    on

    Molecular Clouds and Star Formation in the Outer Galaxy

    My project was a study of star formation and molecular clouds using data from the Five College Radio Astronomy Observatory's CO Outer Galaxy Survey (Heyer et al. 1998, ApJ Suppl,115,241) and the IRAS point source catalog. The CO survey contains more than 2 million spectra and is the most detailed millimeter spectral line map ever made. It covers approximately 300 square degrees of sky in the outer Perseus arm of the Galaxy.

    The beginning of the project consisted of a general overview of the properties of molecular clouds in the outer Galaxy, including analysis of their masses, volume densities, sizes, dynamics, and temperatures. As a familiarity with these characteristics was developed, the project shifted into an examination of star formation within the clouds of the survey.

    Using the IRAS point source catalog, I created images of the clouds and embedded stars using IDL. After thorough analysis of the IRAS sources' spectra, two samples of clouds were compiled: one of clouds with embedded stars and the other of clouds without embedded stars. Many comparisons between these two samples were made to bring out any characteristics that are indicative of star formation. Specifically, I found a relationship between the samples that suggests that most of the integrated mass of clouds with embedded stars is in a much higher mass range than that of the clouds without embedded stars. Additionally, comparing the column densities of the two samples revealed signs that clouds with embedded stars are more compact than those clouds without stars. These results affirm that molecular clouds that are more massive and compact are likely to have greater star formation efficiencies.


    Andria Schwortz , of Alfred University
    works with Jeff Mangum
    on

    Methyl Cyanide as a Probe of Kinetic Temperature in Dense Molecular Clouds

    Historically, the inversion transition of ammonia (NH3) has been used as the primary temperature indicator in dense molecular clouds. However, the physical approximation typically used for this method assumes that only three energy levels are populated. This model breaks down when the temperature becomes high enough, about 50K. Recent investigations designed to determine the temperatures of the cores of molecular clouds have found that many of them to be at about 70-150K. As these temperatures are beyond the range of accuracy of the NH3 inversion transition method, these numbers have significant inaccuracies. We propose a different temperature probe which retains its accuracy at higher temperatures than the probes previously used. This probe uses the rotational transitions of methyl cyanide (CH3CN), a symmetric rotor. Using measurements of the J=6-5, 8-7, and 12-11 rotational transitions of CH3CN obtained with the IRAM 30m Telescope, we have derived the kinetic temperature within a sample of molecular cloud cores. The analysis of these data used two separate analysis methods; a statistical equilibrium technique which compared the intensities of the different K-transitions within a given J-ladder, and a rotational temperature diagram analysis. The results of this analysis has yielded good temperature and column density figures for some 24 molecular cloud cores within our galaxy. The results of this work will be presented at the AAS meeting in Atlanta, Georga in January 2000.



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