National Radio Astronomy Observatory

Summer Program Report: 2004

Overview

Summer Student Program

Twenty-five students participated in NRAO's 2004 Summer Student program, including 14 undergraduate students supported by the National Science Foundation (NSF)'s Research Experiences for Undergraduates (REU) program, two undergraduate students or graduating seniors supported by the NRAO Undergraduate Summer Student program, and nine graduate students supported by the NRAO Graduate Summer Student program. This was the forty-fifth year of the NRAO Summer Research Program, which has graduate over 950 students in its tenure. Research initiated in previous years by some student and their mentors continues, giving the program a continuing impact even for students who have departed.

There were 146 applicants to the 2004 NRAO summer student program, of whom 69 (47%) were women and 12 (8%) were under-represented minorities. The 14 REU positions were filled by 12 women (86%) and 2 men (14%). One of the REU positions was filled by an under-represented minority (7%). In all, 25 summer students were hired, 15 women (63%) and 10 men (37%), and two under-represented minorities (8%). Eleven students were assigned to Socorro (7 REU), nine to Charlottesville (3 REU), and five to Green Bank (4 REU). Eleven of the student participants, including 9 of the REU students, will present posters on their research projects at the winter meeting of the American Astronomical Society in January, 2005.

Summer Teacher Program

The NRAO's RET program offers teachers both a research experience and, with its emphasis on carryover to the classroom, encourages and supports the concept of inquiry (i.e. research) based instruction. Three teachers participated in NRAO research programs during the summer of 2004, with two teachers supported by the National Science Foundation (NSF)'s Research Experiences for Teachers (RET) program and one teacher supported by a NASA IDEAS Program Grant.

This was the fifth year of the RET program at the NRAO, though the NRAO has offered a variety of teacher workshops for seventeen years. There were 26 applicants to the NRAO RET program from 15 states, of whom 5 (19%) were women. Three RET appointments were offered, but only two were finally accepted (both male). The program has been offered at both Green Bank and Socorro, though this year the only appointments were in Green Bank. In future years, appointments are anticipated at Green Bank, Socorro, and Charlottesville. Similar to the REU students, a brief description of the teachers' projects are included later in the report, and both RETs will present posters on their research projects at the winter AAS meeting in January, 2005.

Organization of Report

This report is organized as follows. In Section 1 we list all Summer 2004 program participants. We then separately describe the different activities students and teachers participated in at one of the three main NRAO sites: Charlottesville (Section 2), Green Bank (Section 3), and Socorro (Section 4). In the following two sections we present brief descriptions of the research projects completed by each student (Section 5) or teacher (Section 6). These descriptions are available on-line at http://www.nrao.edu/students/archive/projects.php, which includes links to the final written reports. Finally, in Section 7 we list all of the summer projects which will be presented at the 205th meeting of the American Astronomical Society in San Diego, CA in January, 2005. Many of these presentations are expected to be published in astronomical journals in 2005-6.

Table of Contents

1. Table of 2004 NRAO Summer Program Participants
2. Site Specific Activities: Charlottesville, VA
3. Site Specific Activities: Green Bank, WV
4. Site Specific Activities: Socorro, NM
5. Summer Student Project Summaries
6. Summer Teacher Project Summaries
7. Poster Titles for 205th AAS Meeting

This table summarizes the student and teacher participants (name and school attending), research project (title, mentor, and assigned site), and the source of student support: NSF REU for students supported by the National Science Foundation (NSF)'s Research Experiences for Undergraduates (REU) program, NSF RET for teachers supported by the National Science Foundation (NSF)'s Research Experiences for Teachers (RET) program, NRAO GRP for students supported by the NRAO Graduate Summer Research Program, and NRAO uGRP for students supported by the NRAO Undergraduate Summer Research Program. Overall there were 25 summer student participants (14 REU) and 3 summer teacher participants (2 RET).

2004 NRAO Summer Program Participants (N=28)
Student	School	Project	Mentor	Site	Program
Indraneil Biswas	University of Virginia	Epoch of Reionization Experiment : Antenna and Antenna Mount Design	Rich Bradley	CV	NRAO GRP
Patrick Cameron	California Institute of Technology	A Pipeline for VLA data reduction	Dale Frail	Soc	NRAO GRP
Jana Grcevich	University of Wisconsin- Madison	High Resolution Imaging of Three Starless Cores using Diazenylium	Yancy Shirley	Soc	NSF REU
Charles G. Gear	Elkins High School, Elkins WV	RFI Detector Calibration & Curriculum Development	Ron Maddalena & Sue Ann Heatherly	GB	NASA IDEAS
Nicole Gugliucci	Lycoming College	The Evolution of Radio Galaxies	Greg Taylor	Soc	NSF REU
Kelley Hess	Cornell University	Radio Sources in the Andromeda Galaxy	Lorant Sjouwerman	Soc	NSF REU
Bradley Isom	University of Nebraska-Lincoln	A Test Spectrometer for the Green Bank Electronics Division	John Ford	GB	NSF REU
Sarah Jaeggli	University of Arizona	Broadband Digital Spectrograph for the GB/SRBS	Rich Bradley	CV	NSF REU
Carlos Kelly	University of Wyoming	Software Development for the ALMA Correlator	Jim Pisano	CV	NRAO GRP
Charles James Kelly	Rockbridge County HS, Rockbridge VA	Visualization of Pulsar Spigot Data	Karen O'Neil	GB	NSF RET
John Kelly	University of Virginia	VLA Observations of the Chandra Deep Field South	Ken Kellermann	CV	NRAO GRP
Mariana Lazarova	Sweet Briar College	Turbulent Characteristics of Galactic HI	Toney Minter	GB	NRAO uGRP
Marsha Logan	Benedict College	VLA Observations of the Solar Chromosphere	Tim Bastian	CV	NRAO GRP
Chun Ly	University of Arizona	Investigating the Structure of Radio Jets	Craig Walker	Soc	NRAO GRP
Ann Martin	University at Buffalo	The Life of Young Radio Jets Near Black Holes	Yuri Kovalev	GB	NSF REU
Danielle Miller	James Madison University	Data Reduction Involving Higher-Dimensional Arrays	Amy Shelton & Nicole Radziwill	GB	NSF REU
Rebecca Percy	Villanova University	Automated 600-720 GHz Receiver Measurements	Eric Bryerton	CV	NSF REU
Lin Qiu	University of Wisconsin - Madison	Automation Hardware Development for ALMA Receiver Evaluation	John Effland	CV	NRAO uGRP
Lynnae Quick	North Carolina Agricultural and Technical State University	Radio Observations of Brown Dwarfs	Rachel Osten	CV	NSF REU
Urvashi Rao Venkata	Univ of California, San Diego	Monte Carlo Image Analysis in Radio Interferometry - A statistical approach to feature/object detect	Tim Cornwell	Soc	NRAO GRP
C. Steve Rapp	A. Linwood Holton Governor's School of Abington VA	RFI Detection and Mitigation and the NRAO Quiet Zone	Ron Maddalena	GB	NSF RET
Kirstin Schillemat	Clarkson University	The Jet Proper Motions of the Microquasar SS433	A. Mioduszewski, V. Dhawan, and M. Rupen	Soc	NSF REU
Sarah Scoles	Agnes Scott College	A Search for explosive radio transients in the VLA data archive	Glen Langston	GB	NSF REU
Anandkumar Shetiya	New Mexico Tech, NM, USA	Optimization of Scale Sensitive Deconvolution Algorithms	Sanjay Bhatnagar	Soc	NRAO GRP
Christine Simpson	Wellesley College	Water Masers Toward Class I Protostar YLW16A	Mark Claussen	Soc	NSF REU
David Stewart	Virginia Tech	Prototype Design of a New Orthomode Transition Based on the Active Balun Technique	Shing-Kuo Pan	CV	NRAO GRP
Adrienne Stilp	University of Wisconsin-Madison	Observations of the Sunyaev-Zeldovich Effect with the Cosmic Background Imager	Steve Myers	Soc	NSF REU
Ben Zeiger	Willamette University	Time Evolution in the Supernova Remnant CTB 80	Shami Chatterjee & Walter Brisken	Soc	NSF REU

2. Site Specific Activities: Charlottesville VA

The 2004 Summer Student program at NRAO/Charlottesville was under the direction of John Hibbard and Rich Bradley. There were nine students in the 2004 Summer Student Research Program at NRAO-Charlottesville, three of them under the NSF Research Experience for Undergraduates (REU) program. The top row of the above picture shows some of the Charlottesville summer students during their field trip to Green Bank. The students are (left to right): Lin Qiu (uGRP), Becca Percy (REU), Carlos Kelly (GRP), Sarah Jaeggli (REU), Lynnae Quick (REU), and Dave Stewart (GRP). Not pictured are Indraeil Biswas (GRP), John Kelly (GRP) and Marsha Logan (GRP). In the bottom row are Green Bank students Ron DuPlain (NRAO co-op) and Mariana Lazarova (uGRP).

The summer program included a series of introductory level lectures on aspects of astronomy, particularly radio astronomy and radio instrumentation The lectures are listed in the CV Summer Student Schedule below. The highlight of the summer was a student observing project using the Green Bank telescope (GBT), the world's largest steerable telescope. The students observed a galactic star forming region in the 2cm line of H₂CO (formaldehyde). This line is found ubiquitously in absorption, but rarely in emission. The goal was to map the region around the site of previously reported 2cm formaldehyde emission in a star forming region in Ophiuchus, using the better sensitivity and smaller beam of the GBT. Several regions were targeted in order to discover the extent of the dense molecular gas and how it relates to star formation in the region. The observations went very well, and the students confirmed previously reported formaldehyde emission and absorption, and made a more complete map of the area.

The students traveled to Green Bank, West Virginia, to participate in the GBT observations on July 10 & 11. The students stayed on an extra day in order to meet members of the Green Bank staff, to meet their student counterparts in Green Bank, and to tour the NRAO facilities and telescopes, including the Green Bank telescope and the GBT visitors center. Later that same week, the Charlottesville students returned the favor and hosted a visit from the Green Bank summer participants (July 15-17). During this visit the students gave short presentations on their research topics to each other, took a tour of the NRAO Charlottesville facilities, including the NRAO Technology Center and the future site of the North American ALMA Science Center, and were entertained by the UVa astronomy faculty and graduate students.

At the end of the summer, the students gave a series of 15 minute talks on their projects during a lunch symposium in Charlottesville, and produced a short report describing their summer research. One of the students (REU), will attend the AAS meeting in San Diego, CA in January 2005 to present posters on her summer project.

3. Site Specific Activities: Green Bank, WV

The 2004 REU/RET program at NRAO/Green Bank was under the direction of Toney Minter and Sue Anne Heatherly. There were five students and three teachers in the 2004 Summer Research Program at NRAO-GB. Four of the students and two of the teachers were supported by the NSF Research Experience for Undergraduates (REU) or Research Experience for Teachers (RET) program. The above picture shows several of the summer students in the GBT control room during their GBT observations. Seated (left to right) are Ann Martin (REU) and Sarah Scoles (REU). Standing (left to right) are Brad Isom (REU), Ron DuPlain (NRAO co-op), Ron's girlfriend, and Mariana Lazarova (uGRP). Not pictured are Dani Miller (REU) and Brad Isom (REU).

The Green Bank summer student/teacher calendar is given below. The Green Bank summer students were able to participant to varying degrees in several workshops. These include the NASA Goddard/NRAO teacher workhop, the RARECATS teacher workshop, a Chautaugua Short Course on Astronomy, the Society of Amateur Radio Astronomers (SARA) meeting and the Mid Atlantic Astronomical Society Start Party. There was also a weekly Science Lunch with the students every Thursday. In mid-July the Green Bank summer participants traveled to Charlottesville to meet their counterparts. During this visit the students gave short presentations on their research topics to each other and took a tour of the NRAO Charlottesville facilities, including the NRAO Technology Center and the future site of the North American ALMA Science Center, and were entertained by the UVa astronomy faculty and graduate students.

During the summer, the Green Bank students conducted their own observational project on the GBT. They mapped the Crab Supernova remnant at 24.2 GHz as well as monitored the Crab Pulsar at 1.4 GHz. At the end of the summer, the students gave the staff a one day seminar where they presented the results of their summer research projects. They also produced a short report describing this work. One of the students (REU), and both RET participants will attend the AAS meeting in San Diego, CA in 2005 to present posters on their summer research projects.

4. Site Specific Activities: Socorro, NM

The 2004 REU program at NRAO/Socorro was under the direction of Greg Taylor, Yancy Shirley and Walter Brisken. Dr. Shirley is a Jansky Postdoctoral Researcher. There were 11 students in the 2004 Summer Student Research Program at NRAO-Socorro from locations as varied as New York to India. Seven of the students participated via the NSF Research Experience for Undergraduates (REU) program while the remaining five were supported by the NRAO Graduate Research Program (GRP). Pictured above are (left to right): (back) Ben Zeiger (REU), (middle) Brian Cameron (GRP), Christine Simpson (REU), Anand Shetiya (GRP), Kelley Hess (REU), Adrienne Stilp (REU), (front) Kirsten Schillemat (REU), Nicole Gugliucci (REU), Chun Ly (GRP), and Jana Grcevich (REU). Urvashi Rao Venkata (GRP) is not pictured.

The summer started off with the students all attending the Ninth Synthesis Imaging Summer School held from 15-22 June 2004 on the campus of New Mexico Tech. The REU students participation in this school was supported by the NSF REU grant. The school covered both the basics and advanced topics of radio (and optical!) synthesis imaging, and served as a great introduction to the VLA and the research that most of the students would be involved with over the summer.

Besides the Summer School, the Socorro summer students had a variety of activities to take part in, as listed in the calendar below. In addition to the scheduled events, there were weekly activities for the students, including a "Wednesday Lunch" (free pizza for students!), a Tuesday Science Tea held in the upstairs lounge, weekly scientific colloquia, and ultimate frisbee on Tuesday and Thursday evenings. The group toured five observatories including the VLA, VLBA Pie Town station, Apache Point (Sloan Digital Sky Survey), Lowell, and NPOI. During weekend trips, the group also visited a few of New Mexico's, West Texas', and Arizona's most scenic locations: The Guadalupe Mountains, Carlsbad Caverns, North Baldy, Three Rivers Petroglyphs, The Grand Canyon, and White Sands (http://www.aoc.nrao.edu/~yshirley/Summer04/WhiteSands/Groupjump.AVI).

The scientific highlight of the summer was the four student-led observational projects, three using the VLA and one using the VLBA. One group used the VLA to search for water masers toward dense molecular cloud cores which are being being observed with the Spitzer Space Telescope and that may harbor nascent or very low-mass protostars. A second group looked for a bridge of HI gas between two neighboring members of the M81 galaxy group. The third VLA project used the VLA in a non-standard mode to search for emission, both pulsed and unpulsed, from an Anomalous X-ray pulsar. The fourth group used the VLBA to attempt to resolve the morphological classification of the core-jet source J2022+6133.

At the end of the summer, the students gave a series of 15 minute talks on their projects during a lunch symposium, and produced a short report describing their summer research (sent under separate cover). At least one (Nicole Gugliucci) has a draft of a paper ready to submit to the astronomical journals. Nine of the summer participants (including all seven of the REU students) will attend the AAS meeting in San Diego, CA in January of 2005 to present the results of their summer research.

This section lists short summaries of the projects for participants in the NRAO Summer Student program. The symbol to the right indicates students who were supported under the National Science Foundation (NSF)'s Research Experiences for Undergraduates (REU) program. All other students were supported under the NRAO Summer Student program.

Indraneil Biswas, of University of Virginia,
worked with Rich Bradley on

Epoch of Reionization Experiment : Antenna and Antenna Mount Design

In order to successfully detect the highly red shifted HI associated with the Epoch of Reionization (EoR), a proper understanding of the galactic and extragalactic foreground contaminants is necessary. An optimum method to do that is by radio interferometry. An EoR interferometer requires antenna elements which:

1. are broadband - operating over a frequency of 130-200MHz
2. are widefield- capable of seeing the whole sky
3. have a stable operation over the whole bandwidth with an ideal Smith chart
4. have a stable radiation pattern for the entire bandwidth devoid of sidelobes
5. are weather resistant to operate for a period not exceeding six months

An antenna which suits the above criteria was found to be a "disc dipole" antenna, with a pair of dipoles in quadrature encapsulated by a pair of metallic discs, such that the axis of the each dipole is parallel to the diameter of each of the discs . For optimum performance, the antenna is placed at a specific height from an electrical ground plane covered with wire mesh.

Biswas was involved in the design, simulation, fabrication and deployment of the antenna elements for the prototype "Epoch of Reionization interferometer." The original design of the EoR antennas was a modification of the sleeve dipole done by Dr. Richard Bradley at the NRAO CDL. Biswas evaluated and modified the design of the EoR prototype antenna using the CST Microwave studio package, running simulations of the antenna by varying dimensions of its individual substructures. A set up with the correct dimensions of the antenna substructures was selected, which gives overall optimum antenna performance.

In addition to the design and simulation of the prototype antenna element, Biswas was involved in the design of the antenna mount. This was designed with the intention of providing a stable set up for making the antenna securely fastened to make data collection possible. Two antenna elements and mounts were constructed in Green Bank WV in early August and eventually deployed in the period between Aug 16-22, 2004. Biswas was involved in the deployment of the entire interferometer array including setting up of the east-west interferometer baseline using GPRS technology, linking up each antenna to the back end electronics using coaxial cables, and testing the performance of the array as a whole.

Patrick Cameron, of California Institute of Technology,
worked with Dale Frail on

A Pipeline for VLA data reduction

This summer Brian developed software for the rapid reduction of large quantities of VLA continuum and spectral line data. The first component of the software consists of procedures written for the Astronomical Image Processing System (AIPS) which can quickly accomplish basic flagging, robust calibration, and simple imaging of a single, multi-source UV data file. The second piece consists of a python script that drives these AIPS procedures through numerous UV data sets. The script is designed to require almost zero user input while keeping the user informed of progress and possible problems. It accomplishes this task by gathering all of the information relevant for reduction from the raw data header and various VLA calibrator manuals, then delivering it to AIPS. This pipeline is well suited for projects involving large amounts of public data from the NRAO Data Archive.

Jana Grcevich, of University of Wisconsin- Madison,
worked with Yancy Shirley on

High Resolution Imaging of Three Starless Cores using Diazenylium

Pre-protostellar Cores, or PPCs, are cold, dense clumps within nearby star-forming molecular clouds that are detected only through their far-infrared to millimeter emission. Since they have no (or very low) internal luminosity, but high column density, they are plausible candidates for the stages just before the formation of a central protostar. Important information can be gained through the study of molecular tracers in these cores.

Diazenylium, or NNH+, has its J=1-0 hyperfine transition at a frequency of 93.17 GHz. Three starless cores, L1498, L1512, and L1544, have been observed using the Nobeyama Radio Telescope with BEARS (a 5x5 array of SIS receivers). The three starless cores are located in the Taurus molecular cloud complex, and have central densities of 10⁴, 10⁵, and 10⁶ respectively. It is hoped that they represent an evolutionary sequence. Jana reduced and analyzed these data, producing final maps consisting of 100 spectra separated by 20.55".

It has been assumed in above the that NNH+ emission is a good tracer of the dust continuum emission, but studies that show this have generally had poor spatial resolution. Jana used the increased resolution of the new data to show that the NNH+ still accurately traces the dust continuum emission for these cores, matching the center position and aspect ratios. She found that the abundances remain constant throughout the core, with no evidence of central depletion. In addition, the velocity dispersion remains constant throughout the core. The spectra showed some evidence of anomalous hyperfine structure and blending, which interfered with the calculation of the optical depth correction. A blue asymmetry was observed in the line in the central regions of L1544. Jana also reduced observations of the NNH+ J=3-4 transition taken at the Caltech Submillimeter Observatory. The line was seen at the central positions of L1544 and L1512, but not observed in L1498.

Nicole Gugliucci, of Lycoming College,
worked with Greg Taylor on

The Evolution of Radio Galaxies

Since their introduction as a new class of active galactic nuclei (AGN) introduced 10 years ago, Compact Symmetric Objects (CSOs) have yielded insights into AGN evolution. They have emission on both sides of the central engine in the form of hotspots and jets. Their small sizes (< 1 kpc) are attributed to their youth (previously accepted as being between 350 and 2000 years old.) These ages are derived from the motions of the hotspots as they move away from each other with time. However, this has only been done for a small sample of CSOs.

Nicole studied 3 epochs of VLBI data at 8.4 GHz for 11 CSO candidate sources from the COINS sample (CSOs Observed in the Northern Sky). Along with Alison Peck (CfA) and Greg Taylor (NRAO) and Marcello Giroletti (IRA), she identified 5 of these as new members of the CSO class due to morphology, spectral index maps, and proper motions. Four sources were rejected on the basis of their core-jet morphologies and spectral indices, leaving 2 candidates. With these and 10 other CSOs from COINS, Nicole measured the proper motions of the hotspots and derived most age estimates between 240 and 3000 years, with one source appearing to be only 20 years old. She also detected polarized flux in two CSOs, a first for this class of objects.

Kelley Hess, of Cornell University,
worked with Lorant Sjouwerman on

Radio Sources in the Andromeda Galaxy

New and archival Very Large Array (VLA) data at 6 cm wavelength was combined and analysed for faint radio sources in the central 10 arcmin of the Andromeda galaxy. Kelley compiled a catalog of radio sources and compared them to sources found in previous radio surveys of M31 at 4 cm and 20 cm with the VLA, and to X-ray sources recently found by Chandra. The field was found to contain 3 SNRs and 312 point sources with an integrated flux 4 sigma, 15 microJy, above the noise, including the nuclear black hole candidate M31*. The majority of the sources found at 6 cm did not have multi-wavelength counterparts, however those with detections at other wavelengths will be used to determine the relative astrometry between the X-Ray field by Chandra and the radio field seen by the VLA. Ultimately, this information will be used to identify the X-ray counterpart of M31* from among 3 candidates separated by only a few arcseconds. Kelley and Lorant anticipate the completion of 48 hours worth of real simultaneous observations with Chandra and the VLA this winter. This will improve current 6 cm VLA observations by doubling the total observing time, and allow one to study the variability of sources in the field, specifically M31*, at multiple wavelengths.

Supernova SN1885A lies less than an arcminute from the core of M31. It creates a striking impression in Hubble images, however it had not previously been detected at radio wavelengths. Kelley confirmed no detection of SN1885A in 6 cm at 15 microJy and but it remains unclear at the 4 sigma, 12 microJy, level at 4 cm. Three candidates were detected in the vicinity of SN1885A's optical image, but more analysis must be done before any of these are accepted or rejected as a possible radio counterpart.

Bradley Isom, of University of Nebraska-Lincoln,
worked with John Ford on

A Test Spectrometer for the Green Bank Electronics Division

The instrumentation on the GBT operates at very wide bandwidths and at very low noise levels. It is difficult for ordinary laboratory instrumentation to be used for diagnosis and testing of these sensitive instruments. The NRAO at Green Bank obtained the ALMA Test Correlator hoping to create from it a scale replica of the Spectrometer being used in the GBT control room. This replica would be used to test the instrumentation without having to take observing time away from astronomers. This summer, Brad worked with the Green Bank engineers to modify this Lab Spectrometer to suit the needs of the technicians. This included adding additional cross-correlation modes, integrating the device into the existing system, and creating interfaces emulating the real Spectrometer. The Lab Spectrometer is very near to complete. All that remains is minimal debugging of the computer code and final testing. Brad used and developed his skills in digital design, computer programming, and hands-on digital troubleshooting.

Sarah Jaeggli, of University of Arizona,
worked with Rich Bradley on

Broadband Digital Spectrograph for the GB/SRBS

The Green Bank SRBS is divided into three distinct stages of implementation. The first consists of a dipole antenna and a spectrometer which scans from 18 to 70 MHz at intervals of four seconds through out the day. This is the system which is currently being used. The second proposed stage replaces the dipole antenna with the LPA (Log Periodic Array) and digital spectrograph which will scan the frequency range from 30 to 350 MHz and adds the 13.7 m dish that will provide a range from 50 to 800 MHz using the Swiss built instrument Callisto. In the final stage Callisto will be replaced with a broadband digital spectrograph capable of ranges from 300-3000 MHz. Also included in this stage will be a new dipole antenna operating in the 10 to 30 MHz range.

Sarah participated in the third stage, creating a prototype for the broadband digital spectrograph that will be used on the LPA in the second stage and for all instruments in the third stage. The broadband digital spectrometer consists of a frequency converter and a PC with a data collection card. Sarah built a filter for the frequency converter and wrote programs to acquire and process the data, and to display a radio spectrum.

Carlos Kelly, of University of Wyoming,
worked with Jim Pisano on

Software Development for the ALMA Correlator

The ALMA correlator software needs to be tested during its development. This software is tightly bound to the ALMA correlator hardware, but often the correlator hardware is not available for testing against the software.

For this reason, Carlos worked to develop a correlator simulator which simulates the functional interfaces to the correlator control computer (CCC) and the correlator data processing computer (CDP). The correlator simulator is a Linux PC running a modified real-time Linux kernel which accepts CAN commands from the CCC and returns responses to it in accordance to established correlator/computer interface. The correlator simulator also produces raw lags via a Python script which is the raw input for the CDP. Carlos focused his work on the CCC interface which accepted control commands, validated the protocols, and returned valid responses. Carlos helped to design, develop, test, debug, and document the correlator simulator system within the framework of the existing ALMA correlator software.

John Kelly, of University of Virginia,
worked with Ken Kellermann on

VLA Observations of the Chandra Deep Field South

This summer John completed data reduction of approximately 50 hours of VLA 20 cm observations of the Chandra Deep Field South, which includes the new Hubble Ultra Deep Field, taken February and March 2004. The elevation of the CDFS field at the VLA is very low, compounding problems with ground pickup and interference, as well as limiting the observable time to only six hours per day. To obtain the highest fidelity image possible, John broke the data into small time segments and cleaned each of these separately before combining them in the image plane. This removed time variable effects and allowed much improved images to be made. The deepest image made using the 2004 data had a noise of ~15 uJy in the center of the field, somewhat higher than the theoretical, likely due to dynamic range effects from the bright sources. This was combined with a previous set of observations to produce an image with a noise ~7 uJy. John also began preliminary work on optical and X-ray comparisons with data from Hubble, Chandra and the VLT. The Chandra data contained about 50 obvious X-ray counterparts to radio sources, as well as a systematic offset in both RA and DEC which must be accounted for in future analysis.

Mariana Lazarova, of Sweet Briar College,
worked with Toney Minter on

Turbulent Characteristics of Galactic HI

Density fluctuations in the galactic neutral hydrogen play a significant role in the dynamics of the ISM and have been observed on a wide range of scales with aperture synthesis telescopes. Our goal was to establish the relationship between the parsec-scale fluctuations detected in this experiment and the observed A.U. scale fluctuations that are seen in the neutral ISM. We aimed at finding the variation of the strength of the HI turbulence with Galactocentric radius. The results would help us determine if the HI fluctuations are a global property of the galactic HI and give us insight on the possible sources of energy for the HI turbulence.

Four lines of sight, towards HD 18537, PSR 0540+23, 220.0+0.0, and 149.5+0.0, were chosen in the outer Galaxy where the velocity-distance relationship is monotonic. Mariana calibrated VLA spectra-line data from five observations at 21 cm. The data were then exported to ASCII files for analysis. Since the spatial power spectrum (SPS) is obtained directly by squaring the amplitude of the complex visibility function, no imaging was required. Mariana developed two IDL programs to (1) estimate the noise power spectrum, and (2) create SPS plots after the noise contribution had been corrected for.

Marsha Logan, of Benedict College,
worked with Tim Bastian on

VLA Observations of the Solar Chromosphere

After about 50 years, theoretical and observational research show that the solar chromosphere is not thoroughly understood. Most models have been static. Static models of the solar chromosphere are based on UV/EUV line and IR/mm continuum observations. However, observations indicate a dynamic state. Dynamic behavior is visible in lines and continua observed on the SOHO spacecraft and Ca II resonance lines. This gives rise to conflicting views of the structure of the poorly understood chromosphere. It is believed that acoustic waves generated in the solar atmosphere propagate upward and form shocks, dissipating their energy and heating nearby material. We question whether these waves play a role in the structure of the chromosphere.

In order to examine the dynamics of the chromosphere, we have made VLA observations because of the VLA's ability to make high resolution two-dimensional pictures of the sun relatively quickly and at several frequencies and also because of the fourier transform relationship that exists between an interferometer and the image formed. The image formation is a result of this mathematical relationship between the visibility function and the radio brightness distribution. Observations were made in 7mm, 13mm and 20mm bands over a two day time frame. We have obtained data made in Ca II from Big Bear solar Observatory; all data was taken in 10 or 15 second cadence. Using AIPS (UVPLOT and ISPEC) we reduced data and obtained time sequence images, formed data cubes (compute the brightness variation as a function of time at different locations), created light curves and formed preliminary k-? diagrams. Our preliminary finding is that there are no oscillations in the radio.

Chun Ly, of University of Arizona,
worked with Craig Walker on

Investigating the Structure of Radio Jets

Chun reduced recent VLBA+Gb+Eb 43GHz observation of M84 where the northern jet has been detected. Poor weather (e.g., snow on GBT and rain on Eb) limited the sensitivity of these measurements. Chun also analyzed VLBA/VLBI observations of M87 taken between 1999 and 2004. He found that a counter-jet exists at 43GHz and 22GHz, and determined that the counter-jet is not free-free absorbed. In addition, the edge-brightened structure and changes in the jet structure are seen. These data should help motivate a proposal to make a movie of M87. Such a movie will hopefully provide clue on how jets are being collimated very close to the supermassive black hole.

Ann Martin, of University at Buffalo,
worked with Yuri Kovalev on

The Life of Young Radio Jets Near Black Holes

GigahertzPeaked Spectrum (GPS) sources are typically characterized as young sources representing an early stage in the development of larger, structurally complex radio objects. They are believed to be young radio jets forming near black holes in structures identified with galaxies and quasars. The GPS sources have similar morphologies to older sources, but a more compact and simple structure. They are identified by a characteristic spectrum, which peaks, appropriately, around 1 GHz. Other criteria for selection include sufficient brightness, spectrum width, and overall shape of the spectrum. Further understanding of these sources depends upon the collection of a larger, more complete sample than has been available in the past. Additionally, the ideal sample would be based upon simultaneous broadband measurements, allowing the observer to work with instantaneous spectra. Nonsimultaneous measurements are inadequate because GPS sources tend to be variable. In order to best understand the physics of GPS sources, and to prevent bias in the selection of a sample of GPS sources, one should avoid making conclusions based on observations taken days, months, or years apart.

Ann selected a sample of GPS sources from a sample of 3000 quasars and radio galaxies brighter than 100 mJy observed with the Russian 600m ring radio telescope RATAN. RATAN provides simultaneous broadband measurements in range of 122 GHz, avoided some of the pitfalls mentioned above. Sources for the sample were selected in many intermediate steps. In the first, 348 possibilities were culled from the original 3000 spectra. This selection was based on the overall shape of each spectrum. Ann fit both parabolic and linear models to the spectra in order to estimate interesting parameters such as the spectral indices, the turnover frequency, and the turnover flux density. She further refined the sample according to how well the data fit the predicted selfabsorbed synchrotron model. Sources were examined for changes in flux density over time, in order to investigate a theoretically predicted increase in the flux density of optically thick synchrotron emission. The results of the project included two lists of sources, one of which was composed of definite GPS sources, and the other of possible GPS sources which demand further investigation. Ann identified 146 sources as GPS sources, with another 28 possibile sources.

Danielle Miller, of James Madison University,
worked with Amy Shelton & Nicole Radziwill on

Data Reduction Involving Higher-Dimensional Arrays

DEAP (Data Extraction and Analysis Program) is a modular package for the interactive display and editing of scientific data with the goal of producing publication quality plots. DEAP is written in Python and incorporates PGPlot, a well-known plotting package in astronomical applications. DEAP was initially developed by a group of graduate students from the University of Maryland Software Engineering program, which included one NRAO employee. DEAP is also used as a framework for bigger packages such GBT FITS Monitor (GFM), which is used as a "quick look" tool by observers at the GBT to show data as it is generated throughout an observation.

This summer, Dani added a 2-D imaging color display capability to DEAP. PGPlot functions were used to set the color table and draw the image. She also implemented a Y2-axis display in DEAP. The Y2-Axis allows the observer to plot two XY plots in the same window using different scales, meaning one plot will be scaled using the Y1-Axis while the other uses the Y2-Axis. Dani prepared and implemented a full design of both new plotting capabilities, including documentation and examples.

Rebecca Percy, of Villanova University,
worked with Eric Bryerton on

Automated 600-720 GHz Receiver Measurements

Becca's project was to assemble, align, and debug the experimental setup for making automated 600-720 GHz receiver noise measurements. She spent the first half of the summer outfitting the receiver cryostat with wiring and the appropriate components to test mixers being made at the University of Virginia's Electrical Engineering lab. The purpose of this receiver is to measure different types of Hot Electron Bolometers (extremely sensitive thermometers that heat up when an incident photon strikes it). Becca assisted in testing the mixer chips (which contain the HEB's). The purpose of these tests is to characterize different types of HEB mixers and decide which will be best for a terahertz receiver. To do so, she set up a Martin-Puplett Interferometer (similar to a Michelson Interferometer except that it aligns the polarizations) which is being used to send the signal into the receiver. This involves sending a Local Oscillator (LO) signal and a load (which simulates an astronomical source) through the interferometer and into the mixer chip. The mixer chip mixes the signals and reduces them to an Intermediate Frequency (IF). We then read the power being produced by the system and we can calculate the system noise. Becca wrote a LabView program to read the power and control a tunable filter. The filter sweeps through the IF range, and a reading is taken at each step.

Lin Qiu, of University of Wisconsin - Madison,
worked with John Effland on

Automation Hardware Development for ALMA Receiver Evaluation

Lin worked on the chopper software for ALMA Band 6 mixer and cartridge measurement systems. The goals for the summer were to modify the chopper circuit, to write a LabView program, to integrate it with the BAND6DAQ measurement software, and to test different input parameters to optimize the chopper speed. The program synchronizes the spinning chopper wheel to a continuous record of hot load and cold load measurement using the power meter, calculating the y - factor by dividing the hot load noise power by cold load noise power. Lin restructured the algorithm to make it more understandable, simplified the architecture for easier code maintenance, and most importantly, resolved the synchronization problem the previous chopper routine had when it missed one trigger signal. The student also successfully sped up the chopper, shortening the full bandwidth test by 16 minutes, resulting in a 22% reduction in test time. The software development process was documented to meet the design standard, which involved changes to the hardware, old commands being discarded and new functions being created in the software, and goals being achieved on both test systems.

Lynnae Quick, of North Carolina Agricultural and Technical State University,
worked with Rachel Osten on

Radio Observations of Brown Dwarfs

The discovery of radio emission from brown dwarfs (accomplished a few years ago by a group of NRAO summer students!) surprised the stellar community, and raised deep questions about the continuance of activity into ultracool stellar objects.

Lynnae worked with Dr. Rachel Osten in studying the characteristics of radio emission from a sample of sources identified as brown dwarfs from the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS). These sources were recently observed with the VLA in X-band (3.6 cm). Lynnae calibrated and imaged these data in AIPS, and measured the flux density of any associated radio emission. In all, Lynnae reduced and analyzed data for nine brown dwarfs (five L dwarfs and four T dwarfs), eight of which were 2MASS sources and one SDSS source. Radio emission was detected from three of the 2MASS objects: 2MASS 0652+472, at a distance of 11.1pc and of spectral type L4.5; 2M0559-1404 at a distance of 10.24 pc and of spectral type of T5; and 2M0857+5708 at a distance of 11pc and of spectral type of L8.

Urvashi Rao Venkata, of Univ of California, San Diego,
worked with Tim Cornwell on

Monte Carlo Image Analysis in Radio Interferometry - A statistical approach to feature/object detect

Image analysis, such as component fitting of radio interferometric images has traditionally been based on likelihood techniques applied to deconvolved images. The analysis usually ignores the uncertainty arising from the process of deconvolution, a non-linear inverse problem. One would therefore like to estimate the properties of components representing the entire emission present in the raw, dirty image. In practice, this is not feasible given the large dimensionality of the parameter space in a pixel based method. A scale sensitive representation of an image as a collection of elliptical gaussian components can control this problem.

Urvashi's project involved the design and implementation of an algorithm that performs a Bayesian image analysis to fit elliptical gaussian components to sub-regions of the dirty image, taking full account of the point spread function. Prior to the fitting of emission inside a given region, the emission outside the region is removed by subtracting a previously deconvolved image. This method produces samples of the posterior distributions for the number and parameters of elliptical gaussian components within the region of interest. Information about relative probabilities and uncertainties associated with the component parameters can augment the process of object detection and characterization. Urvashi compared the performance of this approach to the standard methods. She also tested the algorithm on simulated as well as real data sets, and implemented it as an aips++ glish tool.

Kirstin Schillemat, of Clarkson University,
worked with Amy Mioduszewski, Vivek Dhawan, and Michael Rupen on

The Jet Proper Motions of the Microquasar SS433

SS433 is one of the best known precessing jet sources, and the only jet whose composition, temperature, and density are known from X-ray and optical atomic emission lines. It is also a lovely radio source, as the precessing relativistic jets trace out loops on the sky which can be followed for many arcseconds (corresponding to a few years in the lives of the radio ejecta). We have recently completed a major imaging campaign, covering over a quarter-cycle of the 164-day precession period with daily VLBA and weekly VLA observations to trace the moving ejecta.

In preparation for her project, which was to analyze the sequence of images, Kirstin learned to reduce VLA and VLBA data in AIPS, and attended the 9th Synthesis Imaging Summer School. She then undertook a study of the proper motions in the jet of SS~433, which have been detected optically. She found that while individual radio components travel with steady velocities, these can deviate significantly from the optical Doppler shifts. Ultimately this means that the velocity of the individual bright radio-emitting features differs greatly from the bulk velocity of the underlying baryons that emit the optical lines. The ballistic model however, fits the optical lines and the radio morphology extremely well. This is the first iron-clad proof that the radio components display pattern motion (phase-velocity effects) rather than bulk motion - in no other case is the material velocity known.

Kirstin also analysed the so-called anomalous emission, slower outflows of low surface brightness, oriented perpendicular to the jets, and seen in no other source. Apart from confirming the reality of these outflows, quantitative evaluation of their spectral index and outflow speed proved to be difficult to extract from the present dataset.

Kirstin's work formed part of the analysis of SS433, presented by Amy Mioduszewski at the 2004 High Energy Astrophysics Division meeting in New Orleans, Sept 2004; and will be presented ay Kirstin at the January 2005 AAS.

Sarah Scoles, of Agnes Scott College,
worked with Glen Langston on

A Search for explosive radio transients in the VLA data archive

Transient radio sources are evidence of unique phenomena and are important probes of fundamental physics. A number of groups have detected both galactic and extragalactic transient sources. These observations have led to predictions that long term observations will yield a background of transient events, in imaging surveys.

Sarah's project was to develop a technique for the detection of transient radio sources using Very Large Array archive data on M81 and A2192. These multi-epoch datasets allow for the detection of transients on timescales from < 1 day to 1-17 years. To find long-term transients, Sarah developed modified a program to compile the fluxes and location of all sources in a field. These were compared to the NRAO VLA Sky Survey (NVSS). Sources found in one dataset but not the other were considered candidate long-term transient. To search for short-term transients, she generated image cubes with each plane consisting of 30 seconds worth of data. An average of all plans was subtracted out, leaving only noise, interference, and variable sources.

Two long-term transients were detected. Many possible short-term transients below the accurate detection level of 10mJy and 10sigma were detected, but no reliable candidates above this level were found. These results are available at http://www.gb.nrao.edu/~glangsto/m81/

Anandkumar Shetiya, of New Mexico Tech, NM, USA,
worked with Sanjay Bhatnagar on

Optimization of Scale Sensitive Deconvolution Algorithms

The fundamental goal of scale sensitive deconvolution algorithms is to decompose the image in a set of scale sensitive basis functions (called Adaptive Scale Pixon or Asp components). Since such a basis is potentially non-orthogonal, the algorithms are computationally expensive. This expense is further increased for interferometric imaging due to the fact that the point spread function (PSF) couples widely separated pixels in the image. For complex astronomical images with large number of components, search for the optimal set of scales for these Asp components becomes computationally expensive. The computational expense of the scale sensitive Asp-Clean algorithm (Bhatnagar & Cornwell, A&A, 2004, in press), is of order (N² log(N)) per optimization step per Asp-component. Wavelet transform decomposes the image into spatially localized but orthogonal functions at different scales in O(N²) computations. It can thus provide information about a number of scales faster, compared to the computational load of the Asp-Clean method.

In this project, Anand explored the use of a wavelet transform to design a quicker method to simultaneously estimate the number of dominant scales in the image. Toward this goal, Anand implemented a wavelet server in AIPS++ using a fast wavelet transform scheme (the Lifting scheme). This is now available as a standard tool in the AIPS++ package. He then explored algorithms related to the technique of thresholding in the wavelet space (ForWaRD algorithm, Neelamani et al., IEEE Sig. Proc, 2003) and implemented a simple scheme of thresholding the wavelet transform of the residual image to estimate the dominant scales. He found that hard thresholding at various scales did provide a crude but quicker estimate of the local scales in the residual image, and outlined an iterative scheme to construct a model image. Further work to feed this information into the Asp-Clean algorithm is in progress.

Christine Simpson, of Wellesley College,
worked with Mark Claussen on

Water Masers Toward Class I Protostar YLW16A

Water masers are bright, compact objects that emit strong radiation at 22.2 GHz, and are perfect Very Long Baseline Interferometry (VLBI) targets to trace the motions of the gas where they are found. In 2003 Dr. Claussen observed a strong red-shifted water maser toward Class I young stellar object (YSO) YLW 16A with the VLBA. YLW 16A is located in a very active star formation region of the rho Ophiuchus cloud, which is only 140 pc distant. Several VLBA proper motion studies have been done toward Class 0 YSOs, and in general have found that water masers trace proper motions along the axes of large-scale gas outflows. These are the first VLBA observations toward a Class I YSO.

Christine reduced and imaged six epochs of phase referenced VLBA data spread over two months in 2003. These data were part of the first phase referenced observing program of water masers. She determine absolute positions for the maser spots via phase referencing, and determine the masers' three-dimensional velocities and angles of inclination to the sky. She found that these masers are moving much slower than masers toward Class 0 YSOs for which similar studies have been done. She also found that the masers are traveling close to perpendicular to the plane of the sky, which is consistent with 12CO maps of the large-scale molecular outflows toward this source.

David Stewart, of Virginia Tech,
worked with Shing-Kuo Pan on

Prototype Design of a New Orthomode Transition Based on the Active Balun Technique

An ortho-mode transducer is the part of a radio frequency receiver that converts electromagnetic waves into electric currents. A new OMT is needed for the GBT receivers. Gain and noise temperature stability must be improved by using fewer connectors and better physical temperature stability. The rf passband must be made smoother in both gain and noise temperature through the elimination of trapped mode resonances, the reduction in path lengths, and the reduction in impedance mismatches. A lower noise temperature could be obtained by reducing losses and by improving the impedance match to the low noise amplifier and waveguide. The active balun approach, where four low-noise amplifiers are integrated into a new balanced OMT design, shows promise in achieving the above goals while also increasing the operational bandwidth

Dave's project was to provided reliable performance expectations for a newly designed OMT. Dave used a computer aided design program (Computer Simulation Technology's, "Microwave Studio") to evaluate and and improve different designs of the OMTs. According to the simulations, this new OMT will be significantly better than the one it is intended to replace, which currently in use in several receivers of the GBT.

Adrienne Stilp, of University of Wisconsin-Madison,
worked with Steve Myers on

Observations of the Sunyaev-Zeldovich Effect with the Cosmic Background Imager

The Cosmic Background Imager (CBI) is a small 13-element interferometer that operates in Chile at the ALMA site in the Andes. Since 1999, the CBI has been observing the cosmic microwave background (CMB) and the Sunyaev-Zeldovich Effect (SZE) in clusters of galaxies (at radio wavelengths clusters appear dark against the CMB due to Compton upscattering of CMB photons by cluster gas). The CBI team has been observing a large sample of clusters.

Using both radio and previously-published X-ray data, Adrienne studied the SZE in galaxy clusters Abell 3558 and Abell 3266 in depth this summer in order to derive both information about the gas structure in the clusters as well as the Hubble constant. Because foreground sources can contaminate the signal in visibilities, they must be subtracted. Adrienne used VLA data to determine the flux and the location of these sources, and subtracted them from the CBI data in the uv-plane. She wrote a program in MATLAB to model the residual visibilities from the equation derived for the SZE intensity on the sky. Finally, she found the best fit model for the data by using two methods: maximum likelihood and Markov Chain Monte Carlo distributions. From the parameter models (one of which included the angular distances to the clusters), she was able to calculate the gas distribution in the clusters in addition to the Hubble constant. For the two clusters we obtain a value of 67.4 ± 14.7 km/s/Mpc, which is consistent with the currently-accepted value of 72 ± 5 km/s/Mpc measured by WMAP. However, this error includes only statistical errors from the CBI data and the published X-ray models. We hope to continue the project into fall 2004, adding in other factors like a noise term due to the CMB. We would also like to improve our methods of dealing with foreground source contamination and of computing best-fit models.

Ben Zeiger, of Willamette University,
worked with Shami Chatterjee & Walter Brisken on

Time Evolution in the Supernova Remnant CTB 80

The supernova remnant CTB 80 and the associated radio pulsar B1951+32 form a fascinating system to study the interaction of a neutron star with its environment, with the pulsar traveling toward the edge of an inner core within the larger remnant. For his summer project, Ben combined 1.4 GHz archival VLA data taken in 1989 and 2003 with the array in its A-, C- and D-array configurations. He produced images of the nebula as it appeared at both epochs in order to study its structural evolution. The 14.5 yr time baseline allowed an improved determination of the pulsar proper motion: Ben measured a proper motion of -29.4+-1.3 mas/yr in right ascension and -16.7+-1.3 mas/yr in declination, an improvement in precision by a factor of two over previous measurements. Between the two epochs, Ben found that the stand-off distance from the bow shock to the pulsar decreased by 44 mas, indicating a change in the density of the ambient medium through which the pulsar is traveling and providing support for the models of CTB80's inner core as a pulsar wind-driven nebula.

In the future, images created as part of this project can be compared with x-ray and optical counterparts for correspondence. Further analysis of the evolution of the inner core and continued observations of the pulsar will also improve knowledge of the system. Using the reference sources found in this study, VLBI measurements of the proper motion are also possible.

This section lists short summaries of the projects for participants in the NRAO Summer Teacher program. The symbol to the right indicates the two teachers who were supported under the National Science Foundation (NSF)'s Research Experiences for Teachers (RET) program. The other teacher was supported by a NASA IDEAS Program Grant.

Charles G. Gear, of Elkins High School, Elkins WV,
worked with Ron Maddalena & Sue Ann Heatherly on

RFI Detector Calibration & Curriculum Development

This summer, Charles worked in the Quiet Skies Project testing the prototype small portable RFI detector, calibrating it, and developing a curriculum for its use for inquiry based learning for middle school and high school students.

Charles James Kelly, of Rockbridge County HS, Rockbridge VA,
worked with Karen O'Neil on

Visualization of Pulsar Spigot Data

This summer, James created a data analysis program to display pulsar information coming from the Green Bank Telescope pulsar spigot card in semi-real time. The program can then be used both for snap-shot images of pulsars, to insure that data quality is good, and to monitor the system power levels. The program was written in the python language to allow ready portability between various software platforms (windows, Linux, etc.).

C. Steve Rapp, of A. Linwood Holton Governor's School of Abington VA,
worked with Ron Maddalena on

RFI Detection and Mitigation and the NRAO Quiet Zone

This summer, Steve worked with the Radio Frequency Mitigation group at Green Bank to investigate the mitigation issues in and around Green Bank. He field tested a small portable RFI detection unit being developed to determine its limitations, calibration, and usability by middle school and high school students for inquiry based learning projects.

Thirteen of the NRAO summer program participants, including 9 of the REU students and both of the RET participants, will travel to San Diego, CA, to attend the 205th Meeting of the American Astronomical Society, from January 9-13 2005. Below are the titles and abstracts of the posters they will present describing the results of their summer research.

[11.01] Radio Observations of Brown Dwarfs

L. C. Quick (NC A&T State University), R. Osten, T. Bastian (NRAO), S. Hawley (University of Washington)

Radio emission commonly signifies the presence of magnetic activity in the coronae of late-type stars, while emission from the H-alpha transition is a sign of magnetic activity in their chromospheres. Surveys of H-alpha emission from ultracool dwarfs of spectral types late M, L, and T have not shown this indicator of magnetic activity. As a result, it was believed that all magnetic activity declined in these cool bodies. Although sparse, the most recent detections of radio emission contradict this behavior. As part of a large VLA survey of nearby ultracool dwarfs out to 13pc, the aim of my research was to determine how common radio emission is in these late-type stars. Data from 9 L and T dwarfs was reduced, and evidence for emission was detected from three of these objects. This research was conducted as a part of the NRAO Summer Student program, with partial funding from the National Science Foundation.

[68.07] Short and Long Term Radio Transient Searches

S. A. Scoles (Agnes Scott College), G. I. Langston (NRAO)

Transient radio sources are markers of unique phenomena and important probes of fundamental physics. We discuss the currently available limits on the number of radio bright transient events and describe a plan for detection of transient radio sources using Very Large Array archive data. The data analysis plan for transient source detection is tested by examination of two epochs of observation of galaxy M81.

We present a study of two epochs of observations of galaxy M81 to find transient radio sources brighter than 10 mJy and 10 sigma occurring on time scales of 30 s to 30 m and 10 to 15 years. Candidate transients are proposed and analyzed.

A comparison is made by generating a map of each data set and finding the coordinates and peak flux of each source in the field. By coincidence, one transient, SN1993J, is re-detected using this method.

To search for short-term transients, we use VLA observations to generate a graph of the average flux over a series of 30 s time intervals. One candidate short term event was found using this method and confirmed in the appropriate images when the data sets were individually subtracted from an average flux image. This short-term transient, however, is more probably explained by local interference than by an astronomical phenomena.

The detection of two candidate transients in a small angular area of the sky is unexpected as previous upper limits of transient density are much lower.

If you would like more information about this abstract, please follow the link to http://www.gb.nrao.edu/~glangsto/m81.

[69.07] The Hubble Constant Derived from the Sunyaev-Zel'dovich Effect

A.M. Stilp (University of Wisconsin-Madison/NRAO), S.T. Myers (NRAO)

One powerful way to determine the distance to galaxy clusters is the combination of the Sunyaev-Zel'dovich Effect (SZE) with thermal bremsstrahlung from hot gas in the intracluster medium. This technique allows a measurement independent of the cosmic distance ladder. We will present an analysis of two low redshift (z < 0.1) galaxy clusters, A3266 and A3558, using the above method. By combining SZE observations from the Cosmic Background Imager (CBI) with results of previously-published X-ray data, we fit models of cluster gas structure to the data using both a maximum likelihood method and a Markov Chain Monte Carlo (MCMC) algorithm. The best-fit models yield a measurement of distance to the galaxy clusters, and a value for H₀ can be calculated from the best-fit distances and published redshift data. We obtained a result of H₀ = 65±14 km s^-1 Mpc^-1 as an average of the H₀ values for each cluster, which is consistent with the value of 72±5 km s^-1 Mpc^-1 measured by WMAP. We will discuss the application of the MCMC algorithm to SZE and X-ray data as well as display the results of our own analysis using this technique. This work was supported by a NSF-REU site grant to Associated Universities, Inc./National Radio Astronomy Observatories.

[96.04] Monitoring Radio Frequency Interference: The Quiet Skies Project

S. Rapp (Linwood Holton Governor's School), C. Gear (Elkins High School), R.J. Maddalena, S.A. Heatherly (NRAO)

The Quiet Skies Project is a result of the Research Experience for Teacher (RET) program during the summer of 2004. Teachers were involved in discovering the relationship between radio frequency interference (RFI) and radio astronomy observations. S. Rapp participated in astronomy observations with the Green Bank Telescope in order to characterize RFI issues at radio observatories and worked closely with the Green Bank Interference Protection Group. This work included such tasks as mitigation of locally-generated RFI from power poles and running radiation propagation studies for transmitters within the National Radio Quiet Zone.

A curriculum was created to allow high school students to participate in a research effort to determine RFI levels in their communities. The aim of the project is to promote student awareness of radio astronomy and radio frequency interference through an inquiry-based science curriculum. It is hoped that the project will go national by 2007.

A prototype RFI detector was created and tested at four wavelengths; 850, 900, 1425, and 1675 MHz. High school students used a beta version of the RFI detector to explore the occurrence of RFI at their schools and in their communities. The student goals of the Quiet Skies Project are to:

• Measure interference levels at their schools and in their communities;
• Reduce and transmit their data to an NRAO data base;
• Use online spectrum allocation data, and local information to determine possible causes of interference in their area;
• Analyze the complex trade-offs between radio astronomy's need for quiet skies, and other commercial, and non-commercial uses of the spectrum and share their insights with others.

This work was funded by the NSF-RET program and a grant from the NASA-IDEAS program. If you would like more information about this abstract, please follow the link to http://www.nrao.edu/epo/.

[98.09] High Resolution Imaging of Three Starless Cores Using N₂H⁺

J.M. Grcevich (University of Wisconsin - Madison/ NRAO), Y.L. Shirley (NRAO)

Pre-protostellar cores are dense, cold regions in molecular cloud complexes, but do not show signs of an internal source of luminosity. It is thought that pre-protostellar cores represent the evolutionary stage just prior to low-mass star formation. Diazenylium (N₂H⁺) provides an excellent density tracer for late stage pre-protostellar cores because it is resistant to depletion, and its hyperfine structure can yield useful information about optical depths. We present high resolution BEARS maps of the N₂H⁺ 1-0 hyperfine transition for three pre-protostellar cores, Lynds 1498, Lynds 1512, and Lynds 1544.

A more detailed analysis of the L1498 N₂H⁺ 1-0 hyperfine line ratios indicates that this transition is optically thick over much of the map. The peak column density of L1498 was found to be (8.3 ±3.4) X 10¹² cm^-2 after optical depth correction. N₂H⁺ abundance in L1498 is fairly constant to a radius of 15,000 AU. The width of the N₂H⁺ 1-0 lines in L1498 are also constant to the maximum radii sampled in these observations.

In addition, we present CSO observations of the N₂H⁺ 3-2 transition. The N₂H⁺ 3-2 transition was detected in L1512 and L1544, the more centrally condensed cores. This work was supported by a NSF-REU site grant to Associated Universities, Inc./National Radio Astronomy Observatory.

[104.01] Exploring the Jet Proper Motions of SS433

K. Schillemat (Clarkson University and National Radio Astronomy Observatory), A. Mioduszewski, V. Dhawan, M. Rupen (National Radio Astronomy Observatory)

SS433, an X-ray binary located in the constellation Aquila and the supernova remnant W50, has been studied extensively in the radio and optical for over 20 years. The currently accepted model was developed to explain the moving optical lines, and also fits very well the morphology of the twin precessing radio jets. SS 433 is the one case for which the outflow velocity in the jet (0.26c) is determined by Doppler shifted line emission. We analyzed a sequence of images from ~40 daily VLBA observations at 1.4 GHz of SS 433, to study the kinematics of bright radio-emitting regions in the jet outflow. The motion of 8 pairs of ejected blobs can be followed for ~40 days in this unprecedented data set spanning one quarter of a precession cycle of ~164 days. We demonstrate clearly that the apparent velocities of individual components deviate from the kinematic model by more than 10 percent, even though the model still fits the radio morphology on scales of 50-500 AU. This means the radio emission does not trace the ballistic flow of material, but rather the motion of an overlying pattern of enhanced density, magnetic field or shocks in the jet.

This research was supported by the National Radio Astronomy Observatory Summer Student program, with partial support from the National Science Foundation.

[106.11] The Proper Motion of PSR B1951+32 and Its Interaction with CTB80

B. Zeiger (Willamette University, NRAO), W. F. Brisken (NRAO), S. Chatterjee (NRAO, CfA)

The supernova remnant CTB80 and the associated radio pulsar B1951+32 form a fascinating system to study the interaction of a neutron star with its environment, with the pulsar traveling toward the edge of an inner core within the extended remnant. Using 12 reference sources and a 14.5 yr time baseline, the proper motion of the pulsar was measured as -29.4± 1.3 mas yr^-1 RA and -16.7± 1.3 mas yr^-1 Dec, an improvement by a factor of two over the precision of previous measurements.

Between the two epochs the stand-off distance from the bow shock to the pulsar decreased from 2.258" in 1989 to 2.106" in 2003. The change in stand-off distance indicates a decrease of 13 the pulsar is traveling, providing support the model of CTB80?s inner core as a pulsar wind-driven nebula interacting with a cloud within the extended remnant.

We would like to thank the National Science Foundation for its generous support of this research through the Research Experiences for Undergraduates program.

[110.01] High Frequency VLBA/VLBI Imaging of M87

C. Ly (UCLA), R. C. Walker (NRAO/Socorro), W. Junor (LANL)

New 43 GHz VLBI observations of M87 along with previous observations at 43 GHz and one observation at 22 GHz are presented. These data allow us to image the base of the jet where many questions regarding the formation of radio jets are left unanswered. These observations occurred in 1999, 2000, 2001, 2002 and 2004. The counter-jet for M87 has been detected from a 22 GHz observation and three epochs at 43 GHz. Moreover, at 43 GHz the edge-brightened structure is present at each epoch and a wide opening angle at the base is confirmed from an averaged image of all the epochs.

Proper motion measurements at 43 GHz reveal that lower limits on the pattern speed of the jet are 0.25 to 0.40c and 0.17c for the counter-jet. Therefore, yearly-sampled epochs cannot provide accurate proper motion measurements. These results lead us to pursue more observations to make a proper movie of the jet base of M87 at 43 GHz with the VLBA. This project was conducted through the NRAO Summer Student program with partial support from the National Science Foundation.

[110.12] Dating COINS: Kinematic Ages for Compact Symmetric Objects

N. E. Gugliucci (Lycoming College), G. B. Taylor (National Radio Astronomy Observatory), A. B. Peck (Harvard-Smithsonian CfA), M. Giroletti (Istituto do Radioastronomia del CNR)

We present multi-epoch VLBA observations of Compact Symmetric Objects (CSOs) from the COINS sample (CSOs Observed In the Northern Sky). CSOs are a class of AGN with emission on both sides of the central engine and with small sizes (< 1 kpc) that are thought to be due to their youth. Their ages are derived from the motions of the hotspots as they move away from each other with time. Our new observations allow us to make estimates of, or place limits on, the kinematic ages for 12 sources with well-identified hot spots. This study significantly increases the number of CSOs with well-determined ages or limits. The age distribution is found to be sharply peaked under 500 years and within a range from 240 to 3000 years, suggesting that many CSOs die young, or are episodic in nature, and very few survive to evolve into FR~II sources like Cygnus~A. Jet components are found to have higher velocities than hot spots, which is consistent with their movement down cleared channels. We also present the first detections of significant polarization in two CSOs, J0000+4054 (2.1%) and J1826+1831 (8.8%). In both cases the polarized emission is found in jet components on the stronger side of the center of activity.

This research was part of the National Science Foundation's (NSF) Research Experience for Undergraduates (REU) at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico.

If you would like more information about this abstract, please follow the link to http://student1.lycoming.edu/~gugnico/research.html.

[136.01] Motions of Water Masers toward Class I Protostar YLW16A

C. M. Simpson (Wellesley College and NRAO), M. J. Claussen (NRAO), B. A. Wilking (Univ. of Missouri-St. Louis), H. A. Wootten (NRAO), K. B. Marvel (AAS)

We present three epochs of phase referenced VLBA observations of water masers toward Class I protostar YLW16A, which is located in the \rho Ophiuchus cloud. We determine absolute positions of the strongest maser and show that the absolute motion is due to the parallax, global motion of the cloud, and the proper motion of the maser itself. Assuming that the \rho Ophiuchus cloud is 150 pc distant, and estimating the global motion of the cloud via Hipparcos stellar proper motions, we estimate the proper motion of the strong maser reference feature to be 6.2+/-3.5 kms^-1. Combined with the radial velocity of this feature, we find the space motion to be 14.8+/-3.5 kms^-1 and the angle of inclination to the plane of the sky to be 65+/-12 degrees. We also track the motion of a weaker maser between epochs.

The NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. Part of this research was carried out under the auspices of the National Science Foundation's Research Experience for Undergraduates (REU) program at the NRAO, and we gratefully acknowledge the funding for this program.

[141.11] Cataloging Radio Point Sources in the Center of M31.

K. M. Hess (Department of Physics, Cornell University)

X-ray observations of the nucleus of M31 with the Chandra X-ray Observatory have led to the detection of 3 sources separated by only a few arcseconds, that, at various times, have been identified as the super massive black hole, M31*. From recent observations of the central 10 arcminutes of M31 with the Very Large Array (VLA) at 6 cm, 312 point sources are detected, including M31*. They are cataloged and compared to 3.6 cm VLA archive, 20 cm VLA survey, H\alpha and [SII] survey data. An attempt is made to determine the relative astrometry between the Chandra observations and the VLA observations to identify M31* from among the X-ray candidates. Supernova SN1885A lies less than an arcminute from the core of M31. It creates a striking absorption feature in Hubble images. However it has not previously been detected at radio wavelengths. Observations confirm no radio emission from the remnant of supernova 1885A in M31, and upper limit of 15 \muJy is determined for the flux density at 6 cm, and 12 \muJy at 3.6 cm. We gratefully acknowledge support from the NSF Research Experience for Undergraduates program.

[153.05] A Pipeline for VLA Data Reduction

P. B. Cameron (Caltech)

I present software for the rapid reduction of large quantities of continuum and spectral line data from the Very Large Array. The first component of the software consists of procedures written for the Astronomical Image Processing System (AIPS) which can quickly accomplish basic flagging, robust calibration, and simple imaging of a single, multi-source UV data file. The second piece consists of a python script that drives these AIPS procedures through numerous UV data sets. The script is designed to require almost zero user input while keeping the user informed of progress and possible problems. It accomplishes this task by gathering all of the information relevant for reduction from the raw data header and various VLA calibrator manuals, then delivering it to AIPS. This pipeline is well suited for projects involving large amounts of public data from the NRAO Data Archive.

I acknowledge support from the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

[153.13] Pseudo-Real-Time Signal Visualization during Pulsar Observations on the Green Bank Telescope

C.J. Kelly, K O'Neil (NRAO-Greenbank)

When using the Robert C. Byrd Green Bank Telescope (GBT) for pulsar observations, observers need to be able to insure the data reaching the observer is of the highest quality possible. To do this, telescope users need to be able to monitor, in real time, the raw signal intensity of data as it flows in from the GBT. In the summer of 2004 at NRAO-Greenbank, my Research Experience For Teachers project was spent developing this utility. For portability and compatibility, the computer language python was used to build the visualization utility. The major hurdle in developing the python modules was in reading and manipulating the tremendous quantity of unprocessed data acquired during an observation. (The spigot data rate is set to be 25 Mb/s.) The data stream is intercepted by a "spigot" card, buffered and then stored on a hard drive as a series of binary files. The python modules attempt to read, parse and organize these binary files to ultimately produce a simple intensity versus time plot of the data stream. The modules developed run as a loop to update the plot several times per minute. Integrating the knowledge and experience of this research in the classroom involves an introductory unit on radio astronomy and astrophysics. Additionally, students will have the opportunity to analyze data collected from the Crab Nebula Pulsar and experience backend processes such as data folding. These activities will be described. This work was funded by the National Science Foundation RET program.