Past Interns and Projects: Summer 2003
 
 SAO Summer Intern Program Projects, 2003


INTERN: Cassandra Fallscheer (California Polytechnic San Luis Obispo)

PROJECT TITLE: A COMPLETE Search for Young Stellar Outflows
ADVISOR: Dr. Alyssa Goodman
MENTORS:

ABSTRACT:
One way to identify active star formation is to search for molecular outflows, because they have been observed toward protostars in high frequency. Outflows are an important source of turbulence in star-forming molecular clouds, and they inject significant amounts of energy into the surrounding medium.

The COMPLETE Survey of Star-Forming Regions (cfa-www.harvard.edu/COMPLETE) will provide the perfect database for an outflow search. COMPLETE is comprised of COordinated Molecular Probe Line Extinction and Thermal Emission observations of three large star-forming regions scheduled to be extensively observed by SIRTF. What is unique about COMPLETE is its coordinated approach. Prior observations of the types Included in COMPLETE abound, but they only rarely fully-sample any region, and no survey has ever covered a single (~10 pc) region fully with molecular line, extinction, and dust emission observations. The lack of an unbiased survey like COMPLETE has left star formation theories without statistical constraints on the temporal and spatial frequency of: inward motions, outflow motions, star formation; cloud disruption; core formation and several other key parameters.

Using the COMPLETE molecular line maps taken at FCRAO, a summer intern should be able to search for molecular outflows and make an important contribution to the field of star formation.


INTERN: Wesley Fraser (McMaster University)

PROJECT TITLE: Outer Planet satellites
ADVISOR: Dr. Matt Holman
MENTORS:

ABSTRACT:
Unavailable.


INTERN: Joleen Miller (Villanova)

PROJECT TITLE: Extrasolar planets
ADVISOR: Dr. Pete Nisenson
MENTORS:

ABSTRACT:
Direct imaging of extra-solar planets or planetary systems would provide coarse photometric and spectroscopic information, giving insights into the planet's atmospheric composition. It would also give an unambiguous determination of the planet's mass (if combined with radial velocity data) by eliminating the ambiguity in the orbital inclination. Direct imaging is extremely difficult due to the large dynamic range required to separate the light from the central star from the light reflected by the nearby planet. Both the diffraction from the telescope aperture and scattered light need to be controlled with extreme precision for planet imaging.

We have a program (partially supported by an NSF grant) to test a concept for achieving the very high dynamic range required for detection of reflected light from exo-planets. We will use an Apodized Square Aperture (ASA) (Nisenson and Papaliolios, 2001) to control the telescope diffraction. ASA adjusts the transmission of the telescope pupil and dramatically reduces diffraction by the telescope except along two narrow crossed, on-axis strips, perpendicular to the edges of the aperture. ASA was originally conceived to be used, in the visible, in NASA's Terrestrial Planet Finder mission as an alternative to an infrared interferometer for finding and characterizing terrestrial-sized extra-solar planets. In this program, ASA could also be used, when combined with adaptive optics and speckle techniques, to detect the light from optimally placed giant planets (orbits known from radial velocity measurements) orbiting nearby stars.

We are currently setting up to perform lab simulations that allow us to test our cameras, apodizing technique, and data analysis algorithms. A summer intern could help us take test data, help develop the software for data analysis (using IDL), analyze the simulation data, and even help us write a paper on the results. This will prepare us for observing runs using these techniques that will start next fall.


INTERN: Michael Mortonson (Massachusetts Institute of Technology)

PROJECT TITLE: X-ray detector development
ADVISOR: Dr. Eric Silver
MENTORS:

ABSTRACT:
I am interested in offering a summer project to an intern interested in experimental physics. The intern will learn about low temperature physics and cryogenic techniques applicable to the development of high resolution x-ray detectors. This may include traveling to the National Institute of Standards and Technology (NIST) to participate in laboratory astrophyiscs measurements on an Electron beam Ion Trap. I will have a better idea of the exact project once I meet with the student.


INTERN: Chris Orban (University of Illinois Urbana Champaign)

PROJECT TITLE: X-ray stars in open clusters
ADVISOR: Dr. Brian Patten
MENTORS:

ABSTRACT:
For this project, X-ray sources will be identified and net source counts will be extracted in eight ROSAT HRI images in the regions of the NGC 2232 and Cr 140 open clusters. These X-ray data will be combined with ground-based photometry and spectroscopy in order to identify candidate G, K, and early-M type members of these clusters.

At present, no members later than about F5 in spectral type are currently known for either cluster. With ages of about 25 Myr and at a distance of just 320 to 360 parsecs, the late-type memberships of the NGC 2232 and Cr 140 clusters will yield an almost unique sample of solar-type stars in the post-T Tauri/pre-main sequence phase of evolution.

The data generated by this project will be used to bolster the late-type membership of these clusters (crucial for the study of the evolution of magnetic dynamo activity in young solar-type stars) as well to re-assess the likely ages and distances of these clusters.


INTERN: Nada Petrovic (University of Chicago)

PROJECT TITLE: Microlensing
ADVISOR: Dr. Rosanne DiStefano
MENTORS:

ABSTRACT:
Microlensing is an exciting tool to probe for dark matter, to study binary stars, and, potentially, to discover distant planets. The project we would work on this summer would have 2 possible components: (1) comparing different microlensing techniques to discover planets, and (2) to study the influences that source and lens binarity have on estimates of the optical depth. The optical depth is a measure of the amount of dark matter that may be in the form of compact massive halo objects (MACHOs).


INTERN: Dan Perley (Cornell University)

PROJECT TITLE: Search for galaxy clusters
ADVISOR: Dr. Paul Green
MENTORS:

ABSTRACT:
Unavailable.


INTERN: Caroline Ring (University of North Carolina Greensboro)

PROJECT TITLE: Infrared star forming regions
ADVISOR: Dr. Lori Allen
MENTORS:

ABSTRACT:
This August the NASA SIRTF telescope system is due to launch, and it is expected to discover thousands of very young stars in the nearest star-forming complexes by observing at mid-infrared wavelengths. To prepare for our group's observing programs with this telescope, we want to assemble complementary near-infrared observations of our target regions, made in the last several years with the ground-based 2MASS telescope. These data have just been released, and are easily accessible over the internet. This program is an opportunity for a student to make a comprehensive study of the stellar content of nearby star-forming regions, and to learn useful techniques of data analysis.


INTERN: Paul Taylor (Boston College)

PROJECT TITLE: Small Magellanic Cloud
ADVISOR: Dr. Andreas Zezas
MENTORS:

ABSTRACT:
With Chandra we can obtain very sharp images of other galaxies. This allows us to probe their X-ray source populations to much fainter limits than was possible before. We chose to observe one of our nearest star-forming galaxies, the Small Magellanic Cloud, in order to study its low luminosity X-ray sources. The main aim of this project is to detect the discrete sources in the five fields of our SMC survey and perform a preliminary study of their X-ray properties (hardness ratios and possibly variability by comparison with earlier ROSAT and Einstein source lists). In a later stage these results will be used to produce an X-ray luminosity function of these sources. Comparison with results from other galaxies studied at this depth (eg Milky Way, M33, M31) as well as with other more distant galaxies will be used to understand the relation between star-formation activity and X-ray source populations. The SMC has been extensively observed in the optical so we will be able to identify optical counterparts of the X-ray sources by cross-correlating them with lists of optical sources.

A student who will work on this project will learn how to analyze X-ray and optical data using existing and previously tested software (CIAO, Sherpa, IRAF). There are ready made scripts and tasks to do parts of this analysis which will be used by the student (after of course the required training). They will also be exposed to the interpretation of scientific data and learn about the different types of sources in galaxies and how we can distinguish between them using observations in different wavebands (mainly optical and X-rays). This way they will learn about the current views of the connections between galactic X-ray source populations and stellar populations. Finally they will learn how to do background literature research on a specific topic.


INTERN: Deborah Turner-Bey (Rockhurst University)

PROJECT TITLE: Magnetism in A-type Stars
ADVISOR: Dr. Vinay Kashyap
MENTORS:

ABSTRACT:
To explore the limits of magnetic dynamo activity on stars at the high-mass end of the the main sequence. The magnetic dynamo begins to operate for late A type stars and is the cause of coronal X-ray emission. No early type A stars have been detected in X-rays, and the location of the boundary where magnetic activity (and hence coronal X-ray emission) turns on has been an open question for decades. Observations with Chandra provide a means to attack this problem. Starting from optical catalogs of bright blue stars and then searching through the ChaMP database to determine whether these stars have been detected or whether upper limits must be set on the flux, we can study the onset of magnetic activity and coronal emission on normal stars.


INTERN: Katherine Whitaker (University of Massachusetts Amherst)

PROJECT TITLE: X-rays from Cluster Abell 119
ADVISOR: Dr. Ralph Kraft
MENTORS:

ABSTRACT:
We will study the X-ray emission from the nearby (z=0.0442) cluster of galaxies Abell 119 using archival XMM-Newton data. Previous optical and X-ray observations suggest that this cluster is undergoing a minor merger. We will use the X-ray data to determine the temperature, the pressure, and the elemental abundances of the gas. From this we will be able to compute the total gravitating mass (i.e. dark matter) in the cluster. We will also create a temperature map to search for evidence of structures related to the merger. Such phenomena include 'cold-fronts', possible 'abundance-fronts', and shocks. The scientific goal of this project is to better understand the hydrodynamics of cluster mergers and the formation of structure.


Abstracts for end-of-summer talks

1)   Cassandra Fallscheer (CalPoly/San Luis Obispo)

The study of molecular outflows is very important in the quest for understanding the process of star formation. Using data collected in the Coordinated Molecular Probe Line Extinction Thermal Emission (COMPLETE) Survey, a list of known molecular outflows in the Perseus Cloud Complex was compiled. A process was developed to search the COMPLETE data for new candidates of molecular outflows.


2)   Wesley Fraser (McMaster University)

Pencil Beam Search Technique and the Size Inclination Distribution of the Kuiper Belt

In this paper we discuss a new technique of finding moving objects in a series of images. this technique implements a 'shift and add' method of stacking images, and allows a deeper probing than the standard three image detection routine. We describe the results of using this technique on an ecliptic Kuiper belt survey. We use this and three other ecliptic surveys to analyze the possibility of different size distributions for the high and low inclination objects. We find it highly likely (99%) that there is only one size distribution between the two groups.


3)   Joleen Miller (Villanova)

Calculating Velocity Shifts Between the Pre- and Post-Upgrade AFOE Data Sets

We present the results of our efforts to develop a procedure to determine the velocity shifts between the stellar reference spectra before and after the upgrade of the Advanced Fiber Optic Echelle (AFOE). When the AFOE spectrograph was upgraded to increase its ability to measure radial velocity variations, the change necessitated taking new stellar references for each star system. All velocity measurements for a given star are made relative to this reference, which is simply an observation of the star on a particular night. However, there is an unknown velocity shift between every pair of new and old stellar reference spectra simply because they were observed on different nights. In addition, other intrinsic differences between the two spectra prevent us from simply recalculating all of the velocities relative to one reference or the other. To overcome this problem, we have begun developing a procedure that calculates the velocity shift between a pair of new and old stellar references. We perform the calculation independently for each wavelength range of the new spectrum that overlaps the old spectrum, which gives us twelve measurements of the velocity. The spread in our results gives us an idea of the precision of our calculations, and we hope to be able to measure the velocity shift with a precision of ~ 1m/s. In this paper we explain our procedures in more detail and discuss our progress of calculating the velocity shift for the star beta Aquilae.


4)   Michael Mortonson (MIT)

Commissioning a New X-ray Microcalorimeter for Laboratory Astrophysics

We have completed a new X-ray microcalorimeter system to detect X-rays from plasmas produced by an Electron Beam Ion Trap at the National Institute of Standards of Technology. the instrument is an upgrade to a detector that was previously used for laboratory astrophysics; it has a 1x4 array of microcalorimeter detectors and improved cooling and data acquisition capabilities. During the test run of the new instrument, spectra of highly charged ions of neon, argon, and krypton were obtained and calibrated using observations of X-rays from a calibration target. We report on the data and the performance of the instrument, noting its advantages over the previous detector as well as a few new technical problems that must me addressed.


5)   Chris Orban (UIUC)

Late-type Membership in the Open Cluster NGC 2232

NGC 2232 is one of the nearest open clusters (~360 pc) with an age of ~25 Myr. This places it in the unique position to study the transition from T Tauri activity to the Zero Age Main Sequence. In order for those studies to begin, late-type members must be identified for the clusters. X-ray observations combined with ground-based photometry and spectroscopy offers the best way to accomplish this goal. We present photometry in the VRI bands, 2Mass near-infrared measurements in the J, H, K bands and spectra for the suspected optical counterparts to the X-ray sources in the field of NGC 2232. 46 late-type members were identified through these efforts.


6)   Nada Petrovic (University of Chicago)

The Role of Binary Sources and Binary Lenses in Microlensing Surveys of MACHOS

Microlensing is a fascinating phenomenon which both provides a confirmation of the General Theory of relativity as well as yields information about the portions of our galaxy that we cannot see, such as dark matter. early microlensing observational searches located strong candidates of point lens, point source light curves as well as binary source and binary lens light curves. However, very few mildly perturbed light curves were observed, which a problematic omission. Also, Di Stefano has suggested that the failure to take binary effects into account may have influence`d the estimates of optical depth derived from microlensing surveys. This paper is a first step in a systematic analysis of binary lenses and binary sources and their impact on statistical microlensing surveys. In order to begin assessing this problem, we ran large-scale Monte Carlo simulations of various microlensing events involving binary stars (both as the source and as the lens) in order to study the lensing and perturbation rates. The five situations we focussed on were a point lens/point source case, the point lens/binary source without binary motion, point lens/binary source with binary motion, binary lens/point source, and a binary lens/binary source including binary motion. For each lensing event we recorded the parameters of the system as well as the times where the curve reached 1.34 magnification. We also sampled the characteristic light curve and recorded the chisq value of a point lens fit to this light curve as will as the maximum magnification. Finally, we recorded the numbers of repeating events, or events which temporarily dipped below the 1.34 magnification value. Using the recorded parameters for each system we were able to reconstruct our sampling range for each individual value of closest approach in order to directly compare the lensing rates in all five of the cases. We found that the binary source light curves had a lensing rate approximately 1.04 times the rate of the point source/point lens light curves. On the other hand, the binary lens light curves had a rate of approximately 1.4 times the rate of the point lens/point source case. Using the chisq values for the fits, and defining a chisq of greater than 1.5 to be perturbed, we found the perturbation rate of binary source light curves to be approximately 5-6% and the perturbation rate due to binary lenses to be approximately 32% which increased to 35% with addition of a binary source to the binary lens. We found significant rates of repeating events in all cases but the point source/point lens. The point lens/binary source with motion, and the binary source/binary lens case had significant fractions of repeating events with more than one repeat, while the binary lens point source and the binary source with no motion mainly caused events with one repeat. We used the starting and ending times of the curves to determine the duration rates of the various lensing events. We noted that the durations were slightly different for each of the five simulations, and that the binary lens cases tended to have a larger fraction of short duration events. Finally, we used the maximum values of the sampled curves to calculate the distance of closest approach as it would be calculated by observers, noting that in the binary lens case an artificially high number of events appeared to have small distances of closest approach due to the high magnifications caused by caustic crossings.


7)   Dan Perley (Cornell University)

Explorations in Multiwavelength Cluster Detection Using Chandra

In this project, we search for serendipitous X-ray clusters, investigate their properties and assess their detectability in optical surveys. Using automatic and manual methods, we search 62 Chandra observations retrieved from archival data in ChaMP, the Chandra Multiwavelength Project, for extended sources. We use visual inspection and red_sequence analysis to evaluate these sources, isolating possible new clusters from spurious detections and non-cluster sources. In addition to detecting five previously known sources, we find two new probable clusters and one additional cluster candidate. Cluster detections are analyzed to estimate redshifts, X-ray luminosities, and other information. We also investigate the Voronoi Tessellation and Percolation (VTP) algorithm in combination with red sequence-based color filtration as a potential cluster finding tool. In preliminary tests, we find that filtered VTP successfully detects all seven (primarily optically faint) clusters in the sample to which it is applied, but a large number of apparently spurious sources are also detected that would have to be screened out via color-magnitude analysis or another confirmatory method. Early results are very encouraging, but further investigation will be needed to establish the practical effectiveness of the algorithm in optical cluster detection.


8)   Caroline Ring (University of North Carolina at Greensboro)

An Examination of Starless Molecular Cloud Cores in SIRTF Core-to-Disks Sample

The SIRTF Legacy Cores-to-Disks (c2d) program has compiled a database of molecular cloud cores planned for observations using SIRTF. Cores in the c2d sample have not been examined for star formation using a uniform database since IRAS (launched 1983). We use the 2MASS database to examine the c2d sample of molecular cloud cores which have been classified as "starless" for infrared excess sources, which, if found, would imply that their classification whould be changed. (J-H) - (H-K) color-color diagrams are used to identify sources with infrared (IR) excess. IR excess sources whose projected position lie within the boundaries of the molecular cloud cores are examined further, using spectral energy distributions, in an attempt to classify them.


9)   Paul Taylor (Boston College)

A Chandra Survey of the Bar Region in the Small Magellanic Cloud

We present the results of a survey of the central part of the Small Magellanic Cloud Galaxy by the Chandra X-ray Observatory. The field of view covered an area of 1280 square arcmin along the most active region of the SMC with five observations between May and October, 2002. This survey was performed with ACIS (Advanced CCD Imaging Spectrometer) in an energy range 05.-0.7 keV. Sources were detected using the wavdetect algorithm, and then spectral and timing analyses were performed on bright detections. the survey yielded a total of 122 significant sources (at 3 sigma level) down a flux near 1e-14 erg/sec/cm2 in the full band (0.7-1.0 keV) and near 1e-15 erg/s/cm2 for the soft band (0.1-2 keV). Among these sources we identify two supernova remnants, seven known X-ray binaries, and eight sources which are most likely pulsar binaries, based on spectra and variability from the Chandra data. Log(N)-Log(S) relations were used to compute the number of detected sources not associated with the SMC region, and that value was found to be at most 155 sources, with a minimum of ~50 sources. Comparisons were made with previous X-ray and optical surveys for identification of sources, namely the ROSAT PSPS and HRI, ASCA, and UBVR surveys, and then cross-correlated with the SIMBAD database. In all, 18 ASCA sources, 26 PSPC, 15 HRI and 38 UBVR were associated with Chandra sources. Due to the high density of optical sources, the probability of chance overlap was calculated and found to be ~30 sources.


10)   Deborah Turner-Bey (Rockhurst University)

The Onset of Magnetic Dynamo Activity in A-Type Stars

A solar type magnetic dynamo is believed to come into operation in late-A stars. Because coronal activity is strongly dependent on the presence of a magnetic dynamo, X-ray emission is a tracer of this dynamo. We have carried out a systematic search for A type stars in Chandra observations using the database of serendipitous detections derived from the Chandra Multi-wavelength Project (ChaMP). No X-ray emission has been conclusively detected in early-A stars, and the ChaMP database provides a significant opportunity to constrain the onset of the dynamo in main sequence stars. In this preliminary survey, we have identified numerous X-ray sources as A star candidates, and find that the data are consistent with main sequence stars becoming X-ray emitters at V-R ~ 0.15, between A6 and A9.


11)   Katherine Whitaker (UMass at Amherst)

An XMM-Newton Study of the X-ray Emission from Abell 119

We have analyzed archival XMM-Newton data of the nearby cluster of galaxies Abell 119 (A119), studying the X-ray emission from the intracluster medium. Using the beta model, derive the luminosity to be 1.64e+44 ergs/s at a radius of 0.73 Mpc, with a central density of 1.63e-3g/cm3. The total gravitating mass within a radius of 0.73 Mpc is 3.76e+15 solar masses, with a plasma mass of 3.11e+14 solar masses, giving a ratio on 8.3%. We measure the average temperature of A119 to be 5.99 keV. A temperature map and azimuthally symmetric profile with the beta model has a minor merger in the northeast region, believed to be falling in at a temperature of 4.41+/-0.44 keV along one of three filaments in the cluster.


 
 

Clay Fellow Warren Brown