2011
Links to:
List of colloquium talks given during the summer of 2011
Program of the SAO Summer Intern Symposium, August 10, 2011
2011 Summer Program Calendars for June , July , and August
Abstracts for posters presented at the January, 2012 AAS Meeting
INTERN: Kate Alexander (Brown University)
ADVISOR: Prof. Alicia Soderberg (OIR Division)
CO-ADVISOR: Dr. Laura Chomiuk (OIR Division)
PROJECT TITLE: A Blind Search for Radio Transients in M51 and Associated Radio Observations of SN1994I
Abstract:
The student will conduct a search for radio transients in M51 using archival data from the Very Large Array collected over a period of six months following the discovery of the Type I supernova 1994I on May 2, 1994. The student will also construct light curves and analyse spectra for the supernova 1994I for the three available epochs, April 10, May 4, and August 8, 1994, and will use these data to study the physical properties of the supernova explosion and model the nature of the progenitor.
INTERN: Joanna Barnes (St. Andrews University)
ADVISOR: Dr. Rosanne DiStefano (TA Division)
CO-ADVISOR: Dr. Joshua Carter (OIR Division)
PROJECT TITLE: Gravitational Lensing Events
Abstract:
The study of nearby lenses is a relatively new endeavor and there are a variety of projects, both theoretical and observational, that can be productive on short time scales. The project I propose for this summer would provide training on both the theoretical aspects and observational aspects of searching for evidence of nearby lenses. The student would learn to compute both the astrometric and photometric shifts induced by gravitational lensing. She would then compare the results with what is and/or can be observed by a variety of telescopes, from those used by amateurs, to the Hubble Space Telescope. Very likely, the student will co-author one or more papers within the year after completing the summer program.
INTERN: Emily Cunningham (Haverford College)
ADVISOR: Dr. Francesca Civano (HEA Division)
CO-ADVISOR: Dr. Tom Aldcroft (HEA Division)
PROJECT TITLE: Properties of X-ray Emitting Quasar Close Pairs from the Chandra COSMOS Survey
Abstract:
Pairs of X-ray emitting sources within a small range of redshift and at a distance of 10-20kpc one to the other have been found in the Chandra COSMOS survey. Galaxy evolution theory says their host galaxies are likely to merge, and that their activity may be stimulated by tidal disruptions of their ISM. Questions we wish to address include: Does being in a pair, on a 'death plunge' affect the quasars, or are they unaware of the fate that is in store? Do their optical spectra look any different from normal quasars? Do their X-ray to radio spectral energy distributions look peculiar or normal? Do these quasar pairs lie in an unusual place on any diagnostic diagrams, i.e. the mass (M) versus luminosity (L) plane or optical vs near-IR slope?
We have reduced optical and X-ray data on ~15 such quasar pairs from the COSMOS survey. The student will measure X-ray and optical spectra of this sample of quasar pairs, extract SEDs, measure quasar mass, luminosity, optical slope and NIR slopes, and put these pairs on diagnostic diagrams such as Mass versus Luminosity or optical versus near-IR slope. These results will then be compared with simulations to estimate the significance of their numbers relative to what is predicted from standard clustering models.
INTERN: Chelsea Harris (UC Santa Barbara)
ADVISOR: Dr. Stella Offner (TA Division)
CO-ADVISOR:Dr. Helen Kirk (RG Division)
PROJECT TITLE: Dynamics of Dense Cores in Simulated and Observed Molecular Clouds
Abstract:
Background:
Within our close galactic neighborhood (a few hundred parsecs or lightyears), many molecular clouds have been detected where star formation is ongoing. Many puzzles remain in understanding star formation, including the influence of the large-scale cloud properties on the formation and evolution of the embedded forming stars. To better understand these processes, large surveys are underway at several telescopes focussing on nearby molecular clouds, and an unprecedented amount of data is becoming available. One of the precursors to these multi-telescope, multi-cloud surveys was COMPLETE (led by Dr. Goodman, [1]), which focussed on star formation in several molecular clouds, particularly the Perseus molecular cloud. Most stars appear to form in clusters, where interactions between dense star-forming cores may play an important role in subsequent evolution. Observations from the COMPLETE survey have shown that dense cores in Perseus tend to have very small motions relative to their immediate surroundings, and that the motions between cores within a clustered region are a factor of two smaller then the large-scale gas motions [2]. Interpretation of these results is challenging without knowledge of the 3D structure and dynamics of the cloud. The most promising avenue to improving understanding is through comparisons with numerical simulations of star-formation, where the intial environmental conditions and the 3D cloud structure is known.
Project:
In this project, the student will create and analyze synthetic observations of simulated high-resolution turbulent molecular clouds [3]. The student will use existing code to derive the observed velocity distribution of various molecules, like N2H+ and 13CO, and obtain measurements in a manner that mimics real observing modes. Comparisons between the `observed' and real 3D dynamical properties will provide insight into how the actual observational data can be interpreted. Comparisons can also help to constrain the important physics and initial conditions used
[1] Ridge, N. et al., "The COMPLETE Survey of Star Forming Regions: Phase 1 Data", 2006, AJ, 131, 2921 [2] Kirk, H., Pineda, J., Johnstone, D., & Goodman, A. "The Dynamics of Dense Cores in the Perseus Molecular Cloud. II. The Relationship Between Dense Cores and the Cloud," 2010, ApJ, 723, 457 [3] Offner, S., Klein, R., & McKee, C. "Driven and Decaying Turbulence Simulations of Low-Mass Star Formation: From Clumps to Cores to
INTERN: John Hoffman (University of Illinois)
ADVISOR: Dr. Hans Moritz Guenter (HEA Division)
CO-ADVISOR: Dr. Nick Wright (HEA Division)
PROJECT TITLE: Stellar Cycles
Abstract:
Our sun has a well-known activity cycle of 11 years. Activity can be traced in cromospheric signatures like Ca H and K and traditionally this has been the way to search for cycles on other stars as well (the famous Mount Wilson S index), however on our sun the difference between minimum and maximum activity is much stronger in X-rays than in the Chromosphere. Only very few stars have observed cyclic variability in X-rays and only in one case (our sun) actually more than one cycle is observed. Individual stars, which are monitored on a long-term basis are e.g. alpha Cen and 61 Cyg.
Project:
XMM-Newton and Chandra have been launched more than a decade ago and there are plenty of fields in the archive, which have been observed for several times for varying reasons. Nick has looked at the stellar content of the COSMOS field and in this project the student would analyse archival data. It it a well-defined and self-contained project, which leads the student through the analysis of X-ray data from selecting the data in the archive, downloading it, reduce it, detect point sources, measure count rates (and compare his/her results with pipeline products), extract and fit spectra (to confirm it is a star - this goes beyond pipeline products), generate long-term lightcurves and search for periodicities.
We will start with XMM-Newton observations of the spectroscopic cal targets and look for the stars in the field of the MOS and PN fields, because these fields have been visited a large number of times. Depending on the progress the project makes we can easily extend it (we have a list of sky regions XMM has looked at more then 10 times and we also had a first look at some of the repreated Chandra observations, e.g. the stars in the Deep Field South).
If we find stellar cycles, this will result in the publication, if not, we will try to estimate and upper limit and the magnitude and length of average stellar cycles.
INTERN: Mackenzie Jones (Butler University)
ADVISOR: Dr. Elisabeth Adams (OIR Division)
CO-ADVISOR: Dr. Joshua Carter (OIR Division)
PROJECT TITLE: The Complete Life-Cycle of an Exoplanet Transit Light Curve
Abstract:
I have a stockpile of a dozen or more good-quality transit light curves from several exoplanets, which I would really like to fully reduce and fit (and, ideally, publish). The student would get to see the entire life cycle of a transit light curve: photometry to get the best light curve, literature search for other light curves of the same planet, joint fits of all the light curves to get a consistent set of orbital parameters, examining the timing and other parameters, and then writing up the results. Most of the transits were observed with a new PI instrument on the IRTF, and I have five transits scheduled to be remotely observed with the same instrument between early June and late July; it would be great if the intern could help me with those observations.
INTERN: Ali Ahmad Khostovan (UC Irvine)
ADVISOR: Dr. Jan Forbrich (HEA Division)
CO-ADVISOR: Drs. Charlie Lada, Karin Oberg (RG Division)
PROJECT TITLE: Initial Conditions of Star Formation in the Pipe Nebula
Abstract:
Stars in the mass range of our own Sun form in molecular cloud cores. Starless cores thus are ideal laboratories for the initial conditions of low-mass star formation. The best tool to study these cold cloud cores (with temperatures of ~10 K) are observations in molecular transition lines that occur in the millimeter wavelength (microwave) radio range.
The Pipe Nebula is a nearby molecular cloud complex with an unusually low star formation rate. The region contains hundreds of starless cores and only a single cluster of young stars. The starless cores have been identified by observations of how the Pipe Nebula affects background starlight (extinction mapping). We have surveyed the entire region extensively with various observational techniques, and we have obtained observations of ten different molecular transition lines toward the sample of starless cores using single-dish radio telescopes in North America and Australia. Early results suggest that cores with similar properties (e.g. mass, radius, density, stability, etc.) show very different molecular line emission, and the underlying chemical differences are likely related to their relative evolutionary stages. While most of the chemistry in dense cores occurs in the gas phase, the surfaces of dust grains are involved as well. The millimeter radio observations will thus allow us to study chemical differences across the sample that will shed new light on the question why the Pipe Nebula region has but one region of active star formation. In addition to the pointed observations of starless cores, we also have data to a analyze the spatial structure of selected cores, for example from molecular line mapping observations. This project will start with a survey of the literature concerning the chemistry of starless cores. In a second step the results will be applied to the Pipe Nebula observations, beginning with a cross-correlation of the molecular line detections and other properties of the cores.
INTERN: Sajjan Mehta (Drexel University)
ADVISOR: Dr. Scott W. Randall (HEA Division)
CO-ADVISOR: Dr. Paul Nulsen (HEA Division)
PROJECT TITLE: X-ray Properties of the Intra-Cluster Medium in Optically Selected Galaxy Groups
Abstract:
As the largest virialized structures in the Universe, clusters of galaxies are extremely useful probes of cosmology. Since galaxy clusters are filled with diffuse, high temperature gas that shines brightly at X-ray wavelengths (the intracluster medium, or ICM), X-ray observations are particularly well suited to the detection and study of clusters. If one is to use X-ray observations to catalog the properties of galaxy clusters, it is important to understand the physics of the ICM. Galaxy groups, the lower-mass cousins of galaxy clusters, are ideal for the study of physical processes in the ICM since there are more of them nearby, and since such processes will have a larger relative impact on the ICM in groups due to their shallower gravitational potentials. Furthermore, although groups are less massive than clusters, they are more numerous, and contain a significantly larger fraction of the total mass in the Universe as compared to clusters. They are therefore interesting objects to study
One concern when dealing with X-ray selected samples of galaxy clusters or groups is the inherent selection bias in such samples. X-ray brighter objects will be preferentially detected over fainter ones, leading to an over-representation of such objects in samples. Thus, X-ray selected samples may not be a fair representation of the full population of groups and clusters. With this project, we will examine the X-ray properties of an optically selected sample of galaxy groups. Although optically selected samples will have their own selection biases, these biases are expected to be different from, and largely independent of, X-ray selection biases. A difference between the X-ray properties of X-ray selected and optically selected group samples would indicate significant selection biases, which would need to be fully understood to properly interpret our samples. In particular, we will search for a bimodal distribution in the central entropy of optically selected groups, which is observed cluster samples. Groups with higher central entropy may be overlooked in X-ray selected group samples, since they are expected to be less X-ray bright than low central entropy groups (as is observed with clusters).
The student will learn the fundamentals of high energy astrophysics in the context of the study of galaxy groups and clusters, and the basics of analyzing X-ray data from working with archival Chandra observations. The work will involve understanding, running, and possibly modifying some "homemade" code to carry out the analysis. Some coding experience, particularly a familiarity with Perl, is a plus (although not required).
INTERN: Alex Spatzier (Oberlin College)
ADVISOR: Dr. Catherine Espaillat (RG Division)
CO-ADVISOR: Dr. Scott Wolk (HEA Division)
PROJECT TITLE: A Multi-Wavelength View at a Stellar Nursery
Abstract:
Stars similar to our Sun form deeply embedded in molecular clouds. As they evolve, they become less and less embedded, and they form circumstellar disks, the birthplace of planets. The processes of low- mass star formation can be best studied by observations of nearby young clusters. IC 348 is such a nearby cluster of young stars that lies at a distance of only about 300 pc (1000 light years) from the Sun. To characterize the population of this cluster, astronomers use observations at very different wavelengths. It has become a common tool to use both infrared and X-ray data to assemble a census of young stars in different evolutionary stages. We have recently obtained new X-ray images of this cluster with the Chandra X-ray Observatory, improving both on the sensitivity and the spatial coverage of previous datasets. These images will allow us to find previously undetected X-ray sources and better characterize the population of this cluster. The new X-ray sources that we will find can then be characterized by existing infrared, centimeter radio, and submillimeter observations. The infrared data, both from ground-based telescopes and the Spitzer Space Telescope, will tell us about the evolutionary stage of the sources by providing information on the existence of circumstellar disks. We will use the submillimeter data, obtained at longer wavelengths than the far infrared, to characterize the youngest sources that are still deeply embedded in their natal cloud cores. Finally, radio data at centimeter wavelengths can help us to further constrain the high-energy processes that are related to the X-ray emission.
INTERN: Jordan Wheeler (University of Missouri - Columbia)
ADVISOR: Dr. Huiqun Wang (AMP Division)
CO-ADVISOR: Dr. Sarah Stewart (EPS Department, Harvard University)
PROJECT TITLE: Martian Weather Observations Using Mars REconnaissance Orbiter (MRO) Data
Abstract:
This project consists of making Mars Daily Global Maps from images taken by the MRO Spacecraft and using them to study the pattern of Martian weather. MRO Mars Color Imager takes 13 sets of multispectral global map swaths each day. These images will be radiometrically and photometrically corrected, projected and merged into a global weather map each day. Dust storms and clouds will be identified, recorded and classified. Patterns of dust storms and clouds of various types will be summarized. If there is still time left, then the results above can be compared to atmospheric eddies derived from the concurrent temperature data and modeled by a Mars General Circulation Model. Student working on this project will practice IDL image processing of spacecraft data, gain expert knowledge of Martian weather, and apply atmospheric science principles to another planet.