Fifteen students from colleges and universities in the mainland and Puerto Rico participated in the NAIC Summer Student Program at Arecibo Observatory this year. The program again included a local teacher, Betzaida Ortiz, from University of Puerto Rico (UPR), who worked on projects in conjunction with the Visitor Center and its teacher training workshops, and two students supported by research grants of observatory scientists. One, Carlos Vargas, continued his work of last summer on hot molecular cores of regions of massive star formation with Peter Hofner from the UPR -- Rio Piedras. The other, Derek Kopon from Cornell University, returned for a second summer at Arecibo to continue his research with Murray Lewis on OH/IR stars (evolved stars with circumstellar shells). All the students arrived in time to participate in the first NAIC-NRAO School on Single-dish Radio Astronomy held at the Observatory June 10-15. The students spent the remainder of their summer working on individual research projects in radar and radio astronomy, atmospheric science and electronics with their advisors. In addition to the regular summer student talks by the observatory staff and visiting scientists, the students also worked on some specially designed hands-on observing projects. One of the students, Ivelisse Cabrera, spent part of her summer observing solar flares with a small radio telescope (radio JOVE) developed by her advisor, Carmen Pantoja, in the UPR campus. Derek Velez from Williams College (Massachusetts), a summer student at the Observatory last year, returned for 3 weeks to continue research with Sixto Gonzalez before taking up a job as a high school physics teacher.

The NSF Research Experience for Undergraduates (REU) program sponsored eight undergraduates and one teacher. The NASA Capability Enhancement program, based at the University of Puerto Rico, sponsored three, and two other students supported by research grants of individual scientists. In addition, a senior undergraduate level student was supported by funding from the NAIC.

The students had many opportunities this summer to observe with the Arecibo telescope. Many of them participated in the ongoing summer student observing project, supervised by Murray Lewis. They monitored spectral lines of OH maser emission from OH/IR stars, to investigate the possible variability as compared with pre-upgrade observations. In addition, all the students worked on specially designed hands-on observing projects. The topics included pulsar, continuum and spectral line astronomy, supervised by the observatory staff (Ramesh Bhat, Jo Ann Eder, Chris Salter and Tapasi Ghosh). Along with the students, the observatory staff members Lisa Wray, Gomathi Thai, and the REU teacher, Betzaida Ortiz, also took part in these observing projects. The hands-on projects involved planning and performing the observations, reducing and analyzing the data, and giving short presentations on their experience and findings. In addition, a number of students took advantage of gaining further observing experience by taking part in the observatory staff's ongoing observing projects. Two students had their own observing programs as part of their summer projects. Among the other high points were an independent student-generated observing project (by Karin Sandstrom from Harvard) to study OH emission lines from molecular clouds to determine their densities and velocity dispersions. The astronomy students will present the results from their summer research at the upcoming AAS meeting in Washington, DC (see below for more details).

The summer started off with a technical bang when the Single Dish Summer School began, educating with lectures and entertaining with a formal party by the pool. The students and guests were treated to some local Puerto Rican musical talent (Senor Dimas and company) and traditional cuisine (big fat cooked pig!). Seven students (and one newly joined staff member) became certified scuba divers and went diving off the west coast, but they returned. Besides many organized trips around Puerto Rico, some students rented cars and toured the island themselves. They explored many islands this year, including Culebra, Vieques, St. John, and Tortolla. The highlight trip was a weekend sojourn to Vieques, during the midst of a hectic political week before the referendum concerning the Navy's presence on the island.

Thanks to the administrative staff of the Observatory, the housing situation for this year's students was very convenient, far exceeding the standards enjoyed by previous summer students. All but two were housed on-site in the visiting scientist's quarters. They were extremely comfortable with access to satellite TV, computers, hot water and the observatory car for errands. The off-site students were highly accommodating despite living in several (3) houses during their stay. One anomaly this year was the lack of vegetarians among the students; no problems were posed by the cafeteria or the traditional Puerto Rican foods.

Coordination of the program this year was aided to a great extent by the valuable guidance and assistance from our Den Mother, Jo Ann Eder, who has been organizing the summer student program for the past many years.

Supported by NSF REU Funds:

Sun Mi Chung (Wesleyan University) studied the neutral hydrogen content in broad absorption line (BAL) quasars. Her advisors, Tapasi Ghosh and Chris Salter, along with Daniel Altschuler, had earlier made Arecibo observations of PKS1004+13, the only radio-loud, low redshift, BAL quasar yet observed. Sun Mi's project involved reduction of these data in order to detect any possible HI absorption feature. The broad absorption lines are associated with high ionization nuclear outflow regions. During the course of the project, Sun Mi also developed some IDL routines that will help excise any persistent RFI (radio frequency interference) from the individual spectra. They find a suggestive 4-sigma absorption feature at the expected velocity of the quasar. Further observations and results will help determine the orientation of the nuclear outflow region relative to the quasar.

Daniel Dougherty (University of Alabama) worked with Dr. Sixto Gonzalez on a theoretical investigation to examine the possibility of detecting ion waves in the topside ionosphere using the Arecibo 430 MHz radar. A new ionospheric model developed by Huba and Joyce for mid- and low-latitude suggests that ion sound waves can be generated in the topside ionosphere at sunrise and sunset with periods on the order of tens minutes. These waves, if they exist, may potentially be detected by the Arecibo incoherent scatter radar. Existing Arecibo data unfortunately do not go beyond 1000 km where the effect of ion sound waves is most obvious. Daniel ran the Huba and Joyce model under different conditions. The results suggest that it may be possible to verify the existence of these waves with the radar if one observes at summer solstice using adequate time and range resolution.

Lindsay DeRemer (Wellesley College) analyzed the continuous wave radar data of near-Earth asteroids under the direction of Mike Nolan and Ellen Howell. The data had been taken at Arecibo Observatory over the last two years. Using this database, Lindsay calculated parameters such as circular polarization ratio, the radar albedo, and the rotation periods, etc. for more than a dozen asteroids. Preliminary results show that asteroids with a diameter of approximately 300 meters or less have a much greater range of values in both circular polarization ratio and radar albedo than asteroids with larger diameters. This indicates surprisingly rough surfaces, and a wide diversity in surface structure among the smallest near-Earth asteroids. Further, some of the smallest asteroids have extremely slow rotation rates, while others spin very rapidly. The results will be presented in the forthcoming DPS (Division for Planetary Sciences) meeting in New Orleans, LA. Lindsay also assisted her advisors in observing the Comet LINEAR 2001 A2-B, both in the 18-cm OH spectral lines and with the S-band (2380 MHz) radar.

Natalia Figueroa (University of Puerto Rico -- Rio Piedras) worked on the design of circularly polarized antennas with her advisor, Lisa Wray. Arecibo Observatory has receivers in the frequency range from 300 MHz up to 6 GHz, and plans to extend this range up to 10 GHz. The currently available test antennas are only vertical linearly polarized. Natalia's project involved designing, constructing and testing circularly polarized antennas to cover the frequency range needed. Important considerations were minimizing the cost, use of materials that are impervious to the humid and salty environment and a moderate size. They started with the design of helical antennas, and experimented with various shapes and materials, by measuring their input impedance, return loss, gain, radiation pattern, polarization purity, etc. The results showed that the maximum bandwidth achievable with a helical antenna is about a decade in frequency, and hence at least 5 antennas are needed to cover the entire frequency range.

Marko Krco (Colgate University) and his advisor, Snezana Stanimirovic, mapped the tip of the Magellanic Stream at the 21 cm wavelength from a week-long Arecibo observations made during this summer. When combined with previous observations made with Arecibo, these maps formed the most detailed information of the Magellanic Stream to date. Marko also expanded on pre-existing IDL routines to create a new software for the reduction of HI maps with Arecibo. Their analysis revealed a variety of interesting and surprising features in the small-scale morphology of the Stream. Further analysis will allow them to estimate the characteristics of the clumps within the Stream and will constrain the possible theories for the origin of the Stream. The results will be presented in a poster paper at the winter AAS meeting.

Mike Nicolls (Cornell University) worked on three software projects for the space and atmospheric sciences group under the supervision of Nestor Aponte and Sixto Gonzalez. The first project was on the development of an interactive web-based software for users to conveniently access the Arecibo World Day data. The online, interactive graphing interface can also be used internally as a means of data analysis. The second project was to develop a real-time monitoring software that will allow any external users with internet access to look at the Arecibo ionospheric observations in real-time. The third was an interactive publication list for the Aeronomy group. For more information on the project, see http://www.naic.edu/menuimag/atmosfer.htm.

Betzaida Ortiz (University of Puerto Rico) was the 2001 Teacher-in-Residence at the Angel Ramos Foundation Visitor Center, under the supervision of young Jose Alonso. Betsy prepared several modules that will help teachers to integrate the use of science and technology in their classrooms. She prepared handy manuals for the use of some of the Texas Instruments and also designed a number of hands-on activities using this technology. Betsy also contributed with many assessment tools used during the teachers workshops. She made excellent use of her opportunities to take part in the various academic activities organized for the REU summer students, including a hands-on project with the 1000-ft telescope. Betsy showed tremendous enthusiasm in observing and studying some pulsars which show the phenomenon of ``pulse nulling'' (i.e., lack of emission from pulsar for a certain number of periods). When she returns to the school, she will write an article describing her summer experience for publication in a local educational newsletter.

Val Phillips (University of Colorado) worked on the distribution of gas in dwarf spiral and irregular galaxies, using the data from observations with the VLA C-array by her advisor, Jo Ann Eder. They mapped the neutral hydrogen distribution of three dwarf spirals and two dwarf irregular galaxies, which were previously detected with the Arecibo telescope. Their analysis revealed that the gas disks extend far beyond the optical galaxies. In fact, the highest gas surface densities were often outside the stellar regions. The rotation in these far regions will allow them to estimate the total dynamic mass of the systems, and thus the dark matter content. Further, they find no clear differences between the gas distributions of the bulge and the bulge-free galaxies. The results will be presented in a poster paper at the winter AAS meeting.

Karin Sandstrom (Harvard University) worked on probing the local interstellar environment through use of pulsar measurements. Her advisor, Ramesh Bhat, earlier studied the Local Bubble and Loop I, the two prominent structures. Karin's work involved extending this type of analysis to several other known structures including Radio Loops II to IV, the Gum Nebula, and the purported giant super-bubble of Heiles (1998). The existing database and the analysis software were considerably revised and the sample selection algorithm was streamlined. The most striking among the results is evidence for an excess scattering (over and above the predictions for a uniform medium) in almost all directions in the local interstellar medium. The Loop II structure, a supernova remnant previously recognized in the all-sky radio continuum map, was studied in detail. This structure has a well constrained angular size, but the distance estimates range from 60 to 170 parsecs. Even larger distances, perhaps as high as 320 parsecs, are favored by the current analysis. Further analysis using pulsar proper motions in conjunction with the scintillation data will help to validate the new results.

Karin also took it upon herself to write an independent proposal for telescope time to study molecular clouds. The proposal was accepted and given special director's discretionary time because of its merit. Karen observed the OH spectra of eleven molecular clouds to determine the densities and velocity dispersions. When she returns to Harvard, she will complete the analysis of the data in order to use the Chandrasekhar-Fermi method to find the plane-of-sky magnetic field strength. In addition, comparisons will be made with line widths and densities derived from other tracers such as 13CO to determine the effects of using different tracers on the calculated magnetic field. The scientific results from these observations will be part of her senior thesis.

Supported by Other Funds:

Ivelisse Cabrera (University of Puerto Rico, Mayaguez) studied infrared and optical images of spiral galaxies with her advisor, Carmen Pantoja. A total of 50 spiral galaxies that had previously been detected at Arecibo at 21-cm were searched in the 2MASS survey using the Public Release Image Server. These galaxies lie in the galactic plane towards the anticenter region. The goal was to find a criterion to classify their infrared images morphologically and compare them with their optical counterparts. The images were processed using the ``unsharp masking'' technique using two types of smoothing: "Laplacian" and "boxcar." This research suggest some of the infrared images resemble the two-arm spirals as found by Block et al. (1991,Nature, 353). The work will be extended to include galaxies that were not detected at Arecibo but for which optical redshifts are known. Ivelisse spent part of her summer working on the Radio JOVE project, an educational project developed by NASA and initiated at the UPR campus. A dipole antenna installed on the roof of the building connected to a receiver built by students was used to study solar flares, verification of detections was made by comparison with data available through the internet.

Homero Cersosimo (University of Puerto Rico -- Humacao) worked with Egdar Castro in the Engineering department, assisting with the design of two projects: modeling the helium support structure for the new multibeam receiver, and a mechanical layout of the 20-40 MHz baseband mixer. Both projects involved using AutoCAD as a drawing design tool, which has extraordinary 3D drawing capabilities. The constraints for the design of the cable rack system for the multibeam receiver were: (a) the use of semi-flexible helium cables (with minimum flex radius of 35 cm), (b) rotatable through 180 degrees, and (c) the rack must minimize space and be accessible for maintenance, plus a special pulley system to take up the slack as the receiver rotates. The new mixer is a prototype circuit to be constructed on PC board using surface mount technology, and can replace the existing 20-yr old design. It takes advantage of current engineering technology; the old circuit measures 70 cm x 70 cm, and the new circuit is only 7 cm x 13 cm. The multibeam receiver project will make use of the new circuit.

Mike Eydenberg (New Mexico Tech) worked with Shikha Raizada and Craig Tepley in the Rayleigh lidar observations during the summer. Mike developed an IDL code to determine the mesospheric temperature perturbations inferred from Rayleigh data and also worked on the interpretation of the density and temperature measurements. In addition, Mike took a great deal of interest in understanding the different laser systems at Arecibo. In paarticular, he got involved in working with the dye laser and the generation of UV light using mixing crystal which is used for the resonance lidar measurements of certain metallic species like Fe, Ca, etc. Mike gained valuable experience in operating the laser systems first-hand, such as, fine alignment of the optical systems, dealing with burned optical components band contaminated dye.

Derek Kopon (Cornell University) came to Arecibo for the summer, with support from one of Professor Yervant Terzian's grants. He spent 10 weeks with us, and participated in all of the summer student activities. His project was to make identifications from the preliminary 2MASS near-IR database with radio positions for OH/IR stars in the Galactic Center that had been previously catalogued with the Australian Compact Array. The IR positions have a precision circa 0.2 arcsecond, while the radio positions have an advertised precision circa 1 arcsecond. The density of 2MASS sources is such that only close associations are likely to be correct: almost all of the suggested identifications were verified against positions from the MSX (Midcourse Space Experiment) survey at 8-24 microns, which has a precision of ~2 arcseconds, but is also particularly apposite to OH/IR stars. They also need to have reasonable to large J-K color indices.

Esther Santos (University of Puerto Rico -- Mayaguez) worked on single-pulse studies of several interesting pulsars using the data taken by her advisors, Leszek Nowakowski and Ramesh Bhat with the up-graded Arecibo. With their unprecedented quality, these new data allow a variety of investigations towards gaining improved insights into the radio emission mechanism of pulsars. Esther's work this summer focused on the study of pulse profile stability, specifically, on the phenomenon of ``mode switching.'' Analysis of these data confirmed the intensity dependence of average profiles earlier seen in PSR 0611+22 and PSR 1133+16 using the data from pre-upgrade observations. Further, mode switching in PSR 0611+22 was studied in great detail. The results of average profiles obtained for different pulse intensity ranges suggest weaker and stronger pulses originate from different altitudes of the emitting region in the pulsar magnetosphere. The new results were compared and contrasted against those obtained by applying a similar analysis to PSR B1237+25, a classical mode switching pulsar.

Carlos Vargas (University of Puerto Rico -- Mayaguez) continued his work of last summer on the study of methanol masers with Peter Hofner. Their aim is to create a catalog of methanol masers at 44 GHz toward regions of massive star formation that can be used as phase reference calibrators for Q band (7 mm) observations with the Very Large Array (VLA) in New Mexico. Carlos' work this summer involved data reduction for 27 sources, selected on the basis of their relations with ultra compact HII regions, infrared sources, and water and hydroxyl masers. Their VLA observations led to the localization of 101 masers in 22 of the 27 sources, with flux densities in the range from $\sim$0.5 Jy to $\sim$230 Jy. Further, they find evidence that the 44 GHz methanol maser is often coincident with molecular outflows. In particular, in the field of IRAS20126+4104, they find five methanol masers coincident with the shock-excited molecular hydrogen gas associated with an outflow.

TALKS:

Wed, June 27: Planetary Nebulae with the Hubble Space Telescope

[Yervant Terzian, Cornell University]

Tue, July 3: Pulsar Timing and Binary Star Astrophysics

[David Nice, Princeton University]

Thu, July 12: Asteroids [Mike Nolan, NAIC/Arecibo]

Thu, July 19: Geology of Puerto Rico [Ellen Howell, NAIC/Arecibo]

Tue, July 24: Electronics for Radio Astronomers [Jon Hagen, NAIC/Arecibo]

Tue, July 31: Studies of the Upper Atmosphere with Incoherent Scatter Radars [Nestor Aponte, NAIC/Arecibo]

Summer Student Symposia:

Fri, June 29: 2-MASS Identifications of OH/IR Stars [Derek Kopon]

Tue, August 7: Temperature and Density Measurements Using LIDAR [Mike Eydenberg]

Tue, August 7: Still Looking at Methanol Masers [Carlos Vargas]

Tue, August 7: Two projects for the Electronics Group: Multi-beam cable rack system & 20-40 MHz Baseband Mixer [Homero Cersosimo]

Wed, August 8: Three Web-Based Projects for the Aeronomy Group[Mike Nicolls]

Wed, August 8: Ionospheric Modeling and the Presence of Topside Sound Waves [ Daniel Daugherty ]

Wed, Aug 8: Circularly Polarized Antenna Design [Natalia Figueroa]

Thu, Aug 9: Near-Earth Asteroid Observations at Arecibo

[Lindsay DeRemer]

Thu, Aug 9: HI Mapping of the Magellanic Stream [Marko Krco]

Fri, Aug 10: Neutral Hydrogen in BAL Quasars, PKS1004+13 [Sun Mi Chung]

Fri, Aug 10: Distribution of HI in Dwarf-spiral and Irregular Galaxies [Val Phillips]

Mon, Aug 13: Probing the Local Interstellar Environment with Pulsars

[Karin Sandstrom]

Mon, Aug 13: Single-pulse studies with new Arecibo data: Pulse profile stability and Mode changing [Esther Santos]

Mon, Aug 13: Optical and Near-Infrared Galaxies Detected on HI in the Zone of Avoidance

[Ivelisse Cabrera]

TOURS:

* Trip to a Sardinara beach nearby to Arecibo, activities include: swimming and limited snorkeling, sand-play, sitting in the sun.

* Tour of Old San Juan including the old forts, museums and shopping.

* Performance of the Brahms Requiem at the Casals Festival at the Belles Artes Theater.

* Nighttime trip to a local beach where giant turtles (in excess of 800 pounds) breach out of the ocean to lay their eggs. A local expert in the turtle field supervised this trip.

* Beach party for the Patron Saint John.

* Four day trip to one of the US Virgin Islands, St. John, renowned for the snorkeling, diving and beautiful beaches.

* Lisa Wray and Ramesh Bhat gave tours of the platform, Gregorian dome and receiver room for small groups of students.

* Horseback riding through almond groves and along deserted beaches.