REU Site: Research Experiences for Undergraduates in Astronomy at Cerro Tololo Inter-American Observatory Annual Project Report (Year 1) 1 October 2011 – 30 September 2012 Submitted to the National Science Foundation Nigel Sharp, PhD, NSF Program Officer Pursuant to Cooperative Support Agreement No. AST-1062976 Cooperative Agreement No. AST-0809409 NOAO is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation NATIONAL OPTICAL ASTRONOMY OBSERVATORY 2012 CTIO REU Students and CTIO Director Dr. R. Chris Smith. From left to right, back row: Samuel Meyer and Dr. R. Chris Smith; middle row: Bezia Laderman and Clara Thomann, Front Row: Melissa Butner, Kimberly Emig, and Christine Gilfrich.
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REU Site: Research Experiences for Undergraduates in Astronomy at
Cerro Tololo Inter-American Observatory
Annual Project Report (Year 1) 1 October 2011 – 30 September 2012
Submitted to the National Science Foundation
Nigel Sharp, PhD, NSF Program Officer
Pursuant to Cooperative Support Agreement No. AST-1062976
Cooperative Agreement No. AST-0809409
NOAO is operated by the Association of Universities for Research in Astronomy (AURA)
under cooperative agreement with the National Science Foundation
NATIONAL OPTICAL ASTRONOMY
OBSERVATORY
2012 CTIO REU Students and CTIO Director Dr. R. Chris Smith. From left to right, back row: Samuel Meyer and Dr. R. Chris Smith; middle row: Bezia Laderman and Clara Thomann, Front Row: Melissa Butner, Kimberly Emig, and Christine Gilfrich.
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Contents
1 ACTIVITIES AND FINDINGS ............................................................................................ 1
1.1 Research and Education Activities..................................................................... 1
1.1.1 Overview of Program Award .............................................................. 1
1.1.2 Science Program .................................................................................. 1
1.1.3 Student Activities & Local Arrangements ........................................... 7
Figure 1: Group photo of the 2012 CTIO REU/PIA program students with Cerro Tololo in the background taken from Cerro Pachón. From left to right: Melissa Butner, Kimberly Emig, Samuel Meyer, Catherine Kaleida (REU Student Coordinator), Christine Gilfrich, Mayte Alfaro (PIA student), Bezia Laderman, Odette Toloza (PIA student), and Clara Thomann. Photo by Peter Pessev (Gemini).
The REU grant provides funding for a three-day field trip to a site of astronomical significance,
which allows the students to get a taste of other observatories and get acquainted with their unique
telescopes, instruments, and operations. For the 2012 CTIO REU program, the students visited
observatories on Cerro Paranal, Cerro Pachón, Cerro Las Campanas, and Cerro La Silla.
Cerro Paranal is the site of the European Southern Observatory (ESO), one of the premier
astronomical sites in the world, and home to the Very Large Telescope (VLT). The VLT is an array
of four 8.2-m telescopes that operate either as stand-alone telescopes or combined through an
interferometric network to act as one large aperture. The observatory is a three-hour drive from
Antofagasta in Northern Chile, through some of the most arid (and beautiful!) terrain on Earth.
While at Cerro Paranal, the students toured the telescopes and observatory facilities, and over lunch
they met a former CTIO REU student Dr. Gabriel Brammer (2001 CTIO REU program alumnus).
Dr. Brammer is currently a postdoctoral research fellow at ESO Chile, working at Paranal
Observatory. He shared the story of his journey from being a CTIO REU student to an ESO Fellow,
and told the students how the REU program helped him to get to where he is today.
Cerro Pachón is home to two telescopes: the 8.0-m Gemini Telescope, and the 4.2-m SOAR
Telescope. Proximity to CTIO, both geographic and institutional, allowed for easy arrangement of a
site tour for the 2012 REU students. Dr. Peter Pessev (Gemini) and Dr. Tiago Ribeiro (SOAR) led
exciting tours for the REU/PIA students, the REU Student Coordinator, and one Gemini student,
introducing the various instruments and modes of observing at each telescope (Figure 2).
Figure 2: The 2012 CTIO REU/PIA program students in front of the Gemini 8-m mirror. From left to right, front row: Felipe Et (Gemini student), Bezia Laderman, Samuel Meyer; back row: Odette Toloza (PIA student), Mayte Alfaro (PIA student), Clara Thomann, Kimberly Emig, Melissa Butner, Catherine Kaleida (REU Student Coordinator), and Christine Gilfrich.
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This year’s REU and PIA students were very interested to see as many of the major
observatories in Chile as possible during their time here. Thus, the REU Student Coordinator also
arranged for tours of the observatory facilities on Cerro Las Campanas (Las Campanas Observatory)
and Cerro La Silla (ESO’s La Silla Observatory) with sack lunches and transportation paid for by
the students. As La Silla and Las Campanas are relatively near (~2 hours driving) La Serena, this
was an affordable expense and seven of the eight REU/PIA students chose to attend.
Through visiting many different observatories, the students were able to learn about the various
types of telescope designs and their benefits and detriments.
Other Field Trips
Maintaining dark skies for astronomical research and for the general public is an important issue for
future astronomers, as the increase of inefficient lighting and light-emitting diode (LED) billboards
threatens the night skies more every year. To illustrate this point, the students visited the summit of
Cerro Grande, the highest peak near the city of La Serena. On Cerro Grande, they measured the light
pollution from the city, and they honed their astrophotography skills under the guidance of Dr.
Malcolm Smith (CTIO). Using a Sky Quality Meter, they measured the sky brightness and
quantified the difference between the sky brightness in the direction of La Serena and the opposite
direction. Former CTIO Director Dr. Malcolm Smith is a skilled amateur astrophotographer, and he
taught the students how best to use their cameras to capture images of the night sky. The students
took many beautiful shots of the southern sky that evening (Figure 3).
During their time in Chile, the students visited two universities in the La Serena/Coquimbo area:
Universidad de La Serena (ULS), and Universidad Católica de Norte. The purpose of these visits
was to facilitate more interactions between the US students and Chilean students and professors, as
Figure 3: From atop Cerro Grande, REU/PIA students observe the planet Venus and measure the light pollution from the cities of La Serena and Coquimbo. Photo by REU student Clara Thomann.
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well as to supplement their cultural and environmental education while in Chile. Mayte Alfaro, a
2012 CTIO PIA participant and ULS student, arranged a meeting with the astrophysics research
group at ULS. The students learned about the research being conducted at the university and
attended an astronomy seminar, “Stars Outside Galaxies,” by Dr. Sergio Torres Flores.
The REU/PIA students also paid a visit to the Marina Biology department at the Universidad
Católica de Norte in Coquimbo, a neighboring city to La Serena. At the Marine Biology department,
Professor Martin Thiel introduced the group to the “stars of the sea,” giving everyone a tour of the
fish and marine life research facilities and the university’s public aquarium. The students then rolled
up their pant legs and explored the rocky coastline next to the university, using the knowledge they
had just gained to find and identify the organisms. In return, Professor Thiel and his Marine Biology
students were invited to the La Cancha Summer Star Party, organized by CTIO, to see the stars in
the sky. The students enjoyed this exchange tremendously, and there will be a similar visit with next
year’s students.
1.1.3 Student Activities & Local Arrangements
The six US REU students, together with the two Chilean PIA students, shared a fully furnished
house on CTIO’s La Serena compound, for which they were charged a modest rent. This
arrangement maximized the cross-cultural interaction for all of them. The students have consistently
rated this cultural component of the CTIO REU/PIA program to be a successful and important part
of their overall experience. The students were provided with a workspace and a computer in the
public computer area of CTIO’s La Serena facility. Each student had a reserved place in the
computer room and was guaranteed access to a computer previously purchased through this REU
grant. The use of the public computer room promoted the opportunity to interact with visiting
astronomers, several of the technical staff, and other interns. As a result, the students were well
integrated in the daily work and social activities of the Observatory.
The REU and PIA students and the REU/PIA program in general received excellent
administrative support from the staff in Chile and the NOAO Central Administrative Services (CAS)
staff in Tucson. The students encountered no problems with the logistical arrangements during their
time in La Serena.
Program Travel
For travel to/from Chile, and for the domestic flight to Antofagasta for the trip to Cerro Paranal, in-
house personnel were used to coordinate all REU logistics with a local, Chilean travel agency. In the
past, this has proven to be the most reliable and often cheapest option. The on-site availability of this
logistical support enables easy troubleshooting should any problems arise. A travel agent in Tucson
with institutional ties to NOAO was used for 2011 REU student travel to the January 2012 AAS
conference. The travel arrangements for that 2012 AAS meeting were done in a timely and
organized manner, and the plan is to continue this relationship for the 2013 AAS conference and in
the future.
Student travel to Chile this year was subject to a delayed flight in Dallas that resulted in having
to spend the night in hotels in Dallas and Santiago before finally arriving in La Serena. This
situation reconfirmed that it is important that the REU Student Coordinator (who was returning from
the 219th AAS meeting) accompany the REU students on their flight from the US to Chile. The
travel to Chile is often the first international flight for the majority of the students and is an
unfamiliar experience for all of them. Support for transportation and accommodation in La Serena
by local CTIO employees was outstanding.
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1.1.4 Conclusions
After 17 years of successful operations, the CTIO REU program continues to provide a positive
educational experience for all participants, not only in learning about astronomy, but also about the
nature and operation of a national observatory, the future and function of the national and
international astronomy facilities, and how one lives and works in a multicultural setting. Each year,
an evaluation questionnaire is distributed to the REU and PIA students by email. They are asked to
complete the questionnaire and are assured that the results will be considered anonymously. An
online form was created that ensures the anonymity of the students. The main purpose of this
evaluation process is to help determine what parts of the REU program curriculum worked well or
poorly, in order to improve the program in following years. It also provides a measure of the impact
of the program on the students and the degree to which they enjoyed their Chilean REU experience.
When asked, “How do you think the REU/PIA experience has changed you and your outlook on
astronomy and astronomical research?” in the online evaluation, one student answered, “[M]y #1
choice for grad school will be an astrophysics department.” The 2012 program was a positive
educational experience for all of the students, not only in learning about astronomy, but also about
the nature of a national observatory, about the future of the national and international astronomy
facilities, and about how one lives and works in a multicultural setting. The students’ impressions of
the program and their reactions to the experience were extremely positive.
1.2 FINDINGS
At the end of the program, each student presented the results of their 10 weeks of research at a
Student Symposium held in the AURA Lecture Hall on the AURA campus in La Serena. Scientific
staff members of CTIO, SOAR, and Gemini attended this symposium. Each student gave a 10- to
15-minute presentation followed by 5 minutes of questions from the audience. The following are
abstracts of the REU/PIA students’ research projects, written by the students and their mentors:
Melissa Butner: “Spectral Classification of Members of a Candidate Cluster in Telescopium”
We characterize whether the spectral types, colors, magnitudes and astrometry for a sample of
stars in the constellation Telescopium are consistent with constituting a true star cluster. The
candidate cluster was first noticed by E. Mamajek as an excess of A-type stars with similar proper
motions in the HD catalog. Based on the number of A-type stars seen, the candidate cluster could be
surprisingly rich, and hence it would surprising that it had remained undetected until now. We
derived accurate spectral types for these stars using optical spectra from the SMARTS 1.5-m
telescope at Cerro Tololo and comparing them to a grid of MK spectral standards. Our initial
analysis is suggestive that a real group may exist, at distance 400 pc and age 630 Myr (similar to the
Hyades).
Kimberly Emig: “Simulated Star Clusters with MASSCLEAN: Testing a Stellar Grouping
Selection Method”
An accurate selection method for identifying and characterizing stellar groupings in nearby
galaxies is essential for determining the size scales of stellar clustering. By generating fields of
simulated star clusters with known ages, masses, sizes and metallicities, the accuracy of such a
selection algorithm can be analyzed. Using code developed in IDL, the Massive Cluster Evolution
and Analysis Package (MASSCLEAN) and SkyMaker have been used to simulate clusters of
varying ages, masses, and sizes with properties tuned to mimic stellar groupings found in Hubble
Space Telescope, Wide Field Camera 3, and F336W images of the dwarf irregular galaxy NGC
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4214. The point spread function (PSF) has been modeled using Tiny Tim. An archive of simulated
star cluster fields with varying numbers of clusters (∼10–200) and randomly selected positions
within the field has been created. Primarily we examine the number of clusters generated versus the
number retained and discuss the limitations of the selection algorithm in light of these results. A
reliable selection method is imperative for studying the size scales and disruption time of stellar
groupings in nearby galaxies and the relationship between the properties of stellar groupings and
their host galaxies.
Christine Gilfrich: “Orbital Period of WD + M Binaries”
Studying WD + M binaries can give insight into the evolution of cataclysmic variables because
of their presence in CVs’ evolutionary process. SDSSJ0256 is a WD + M binary found in the
SLOAN Digital Sky Survey which has not previously been studied; the SLOAN data does not
include an orbital period. I used spectroscopic data from the Goodman Spectrograph on SOAR
collected at various dates to find the changes in H-α emission lines from the main sequence star
throughout its orbit. From these wavelengths, I calculated the velocities, which were analyzed using
a Lomb-Scargle periodogram to find SDSSJ0256’s orbital period to be 2.6 hours (with a false-
positive probability of 10%), its radial velocity semi-amplitude to be 32 ± 5 km/s, and its gamma
velocity to be 19 ± 4 km/s. We compared this to other possible periods from the Lomb-Scargle
periodogram using their power, false-positive probability as outlined by Frescura et al (2008), and χ2
testing. Although the fit to our data is far from perfect, the phase diagram shows a reasonably close
trend. As such, this study points to an orbital period of approximately 2.6 hours for SDSSJ0256, to
be made more certain by additional observations.
Bezia Laderman: “Finding Periodicities CP Eri”
Between January 27 and January 29 the IBWD (interacting binary white dwarf) CP Eri was
observed from the CTIO 0.9m during a period of quiescence. The data was reduced, light curves
were created by comparing CP Eri to other non-variable stars in the field, and periodograms where
generated from the light curves. An unexpected signal corresponding to a 32-minute periodicity was
found, but the expected signal from previous studies at about 29 minutes was not seen, prompting
the need for follow up observations during periods of quiescence.
Samuel Meyer: “Expanding Integrated-Light Photometry of LMC Star Clusters in the NIR to
Extremely Young Ages”
The goal of this project is to extend the sample of LMC clusters with integrated-light
photometry available to the limits set by the depth of the 2MASS Atlas Images. Using recently
published new catalogs of Magellanic Clouds clusters ages, we are focusing mainly on the clusters
populating the parameter space between 250 and 800 Myr. Such clusters are severely under-
represented in the samples available so far. There are two main reasons for this: (i) samples so far
were focused on clusters with reliable age and metallicity determinations; (ii) the masses (hence
luminosities) of the Magellanic Clouds clusters are decreasing with decreasing age. Clusters
younger than ~1 Gyr are much more challenging from an observational point of view and more
difficult for analysis. To tackle the problem we are adopting a statistical approach, analyzing
hundreds of objects populating the selected age interval. Our data reduction and analysis were
focused on obtaining reliable integrated-light magnitudes and error estimates in J, H, and Ks
2MASS filters. The final sample consisted of 30 objects, effectively tripling the number of objects
with integrated-light measurements available in this age interval. The depth of the imaging data
turned out to be the main limitation. We found that particular care needed to be taken in order to
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mitigate the effects of the stochastic fluctuations in the stellar population. The results of the present
study are crucial for our understanding of the LMC star clusters system. They are paving the road
for the deeper Magellanic Clouds surveys that are going to be available in the future. Considering
that the Magellanic Clouds are invaluable astrophysical laboratory affecting many fields of the
modern astronomy, surely this new dataset will play an important role beyond its original purpose.
We are also considering expanding the dataset using dedicated observations in the future.
Clara Thomann: “A Photometric and Spectroscopic Survey of Solar-type Stars in Open Cluster
Collinder 70”
Presented in this review are preliminary results regarding cluster membership and age via
photometry and fiber spectroscopy observations of 70 low-mass stars in open cluster Collinder 70.
The targets were originally selected from color-magnitude diagrams, and subsequently refined by
using low-resolution spectroscopy to determine the presence of H-alpha and Li I. The members of
Collinder 70 were finalized by a measurement of lithium equivalent widths via Gaussian fitting and
direct integration, concluding with a list of 23 probable members. Model isochrones from Baraffe et
al. (2002) evolutionary models are overlaid on a lithium equivalent width and color plot with target
stars, suggesting that Collinder 70 is less than 50 million years old. Other lines of evidence—low
mass stars with un-depleted levels of lithium, indications of giant-like pre-main sequence stars, and
infrared excess—indicate that the cluster is younger, but the age cannot be constrained without
further observations and more lithium-rich members.
1.3 TRAINING AND DEVELOPMENT
The main goal of the CTIO REU program is to provide an opportunity for students to carry out a
research project, supervised by one of the staff astronomers at CTIO, SOAR, or Gemini and by the
REU Student Coordinator. At the end of the program, the students report on their work in the form
of a written report and short presentation. The students were encouraged to work independently, but
those who lacked research experience were given more direct guidance when necessary by their
mentor or the REU Student Coordinator. The CTIO summer students also had the opportunity to
observe on Cerro Tololo, using the CTIO/SMARTS 1.0-m telescope. The objective of the observing
run was to introduce the students to observing techniques and to allow them to sample different
methods of observing, as dictated by various projects that had different scientific objectives. Thus,
the students experienced the three main tasks of a professional observational astronomer:
observation, analysis of results, and subsequent reporting and publication.
Furthermore, the student selection committee aims to select not only the best students, but also
the students who will benefit the most from the CTIO REU program. For example, the committee
ensures that the students come from a mix of large and small astronomy departments. In addition,
the students are selected to have a wide range of abilities and experience to encourage peer
mentoring. The students obtain teaching skills from answering one another’s questions in their area
of expertise (i.e., computing, telescope operations, etc.), and they gain useful tools and information
from the knowledge of their fellow students.
1.4 OUTREACH ACTIVITIES
One of the highlights of this year’s program was the students’ participation in the Summer Star Party
organized by the Education and Public Outreach (EPO) team at CTIO. The Summer Star Party is a
free event offering sky tours of the night sky, viewing of astronomical objects with small telescopes,
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and astronomy-related activities for children. The Star Party is open to the families and friends of all
observatory staff members (including custodians, human resource staff, mechanical shop employees,
etc.). It is held at a dark-sky site called “La Cancha” that is along the road to Cerro Tololo and Cerro
Pachón and away from the city lights of La Serena. The telescopes on Cerro Tololo are clearly
visible from the La Cancha site, and provide a spectacular setting to observe the Southern skies. The
students were each given a small telescope, called a Galileoscope, which they assembled themselves
and learned to use in a mini-workshop given by the EPO team a few days before the event. With
these Galileoscopes, the students assisted the CTIO EPO team with showing stars, planets, and star
clusters to the attendees of the event. At the end of the event, the students experimented with the
night photography skills they obtained while on Cerro Grande and posed for a photo taken by a
fellow Star Party participant, Hérnan Stockebrand (Figure 4).
2 JOURNAL PUBLICATIONS
Over 100 publications have resulted from collaborations with the REU students since the beginning
of the CTIO program in 1995. An updated list of publications is available at a webpage on the REU
CTIO website (http://www.ctio.noao.edu/noao/content/publications-related-ctio-reu-projects). The
following is a list of recent publications by CTIO REU students. These include publications by the
2011 REU cohorts. The 2012 REU students will present their work at the January 2013 meeting of
the AAS. Students’ names are in boldface text.
Figure 4: The CTIO REU and PIA students pose for a photo with the night sky above Cerro Tololo after participating in a Star Party event for the observatory families and friends at the La Cancha site. From left to right, front row: Bezia Laderman, Catherine Kaleida (REU Student Coordinator), and Clara Thomann; back row: Samuel Meyer, Melissa Butner, Christine Gilfrich, Odette Toloza (PIA student), Mayte Alfaro (PIA student), and Felipe Et (Gemini student). Photo by Hernán Stockebrand.