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Philip
S. Muirhead
Ph.D. Student in Astronomy (CV) NASA Earth and Space Science Fellow 208 Space Sciences Building Cornell University Ithaca, NY 14853 muirhead at astro.cornell.edu Advisor: James Lloyd |
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Hi! Welcome to my lame website. Below you will find information about my research and summer softball. For IDL programs related to TripleSpec, go down to Downloads at the bottom of the page.
My main area of research is stellar infrared interferometry. That is, using the interference properties of light at infrared wavelengths to study stars, including detecting orbiting extrasolar planets.
T-EDI
I am currently working on a project involving the combination of a fixed-delay interferometer and a moderate-resolution, near-infrared spectrograph (TripleSpec) on the Palomar 200-inch Hale Telescope in southern California. We will use the instrument to search for potentially habitable extrasolar planets orbiting small and cool stars (compared to the Sun), which are bright in the infrared but dim at optical wavelengths. The fixed-delay interferometer boosts the radial velocity precision of the spectrograph so that we can detect exoplanets using the Doppler technique. The interferometer/spectrograph combination is particularly well suited for infrared radial velocimetry, where conventional high-resolution spectroscopy is hampered by large systematic errors. The TripleSpec Externally Dispersed Interferometer (T-EDI, pronounced "teddy") is a collaboration between Cornell University, the University of California, Berkeley, and the Lawrence Livermore National Laboratory. Some publications:
"Radial Velocity Precision in the Near-Infrared with TEDI"
"TEDI: the TripleSpec Exoplanet Discovery Instrument"
"The T-EDI Instrument for near-IR Radial Velocity Surveys,"
"Noise Studies for Externally Dispersed Interferometry"
"Mass producing an efficient NIR spectrograph" (TripleSpec SPIE Paper)
MIRC on CHARA
Before arriving at Cornell, I was an undergraduate at the University of Michigan working with John Monnier on an image-plane beam combiner for the CHARA interferometer on Mt. Wilson near Pasadena, California. The Michigan Infrared Combiner (MIRC) uses single-mode fibers to spatially filter the light from the CHARA telescopes and can in principal interfere all combinations of all six telescope beams at once, allowing for the maximum number of visibility measurements and atmosphere-independent closure-phases. Currently MIRC can interfere 4 CHARA telescopes and has used closure-phases to map the surface of Altair:
Credit: Ming Zhao (University of Michigan)
Some more publications:
"CHARA Michigan phase-tracker (CHAMP): design and fabrication"
"Michigan Infrared Combiner (MIRC): commissioning results at the CHARA Array"
"The Michigan Infrared Combiner (MIRC): IR imaging with the CHARA Array"
Softball
I'm the "skipper" of the Cornell Astronomy Department's summer softball team, the Big Bangers. If you're interested in playing, please email me. My friend and colleague Babs has some pictures from our last game in 2006, when all the dudes wore skirts. I still don't understand this tradition:
I'm wearing the pink one.
Downloads (updated May 25, 2009)
Here are some IDL programs for extracting point-source Palomar TripleSpec spectra using a Gaussian profile with Optimal Extraction (Horne 1986, PASP) and simultaneously calibrating the OH/OI sky emission lines by fitting an offset underneath the Gaussian. It requires the file tspecdata.idl to be in the same directory as the programs (see the headers for information). These aren't particularly well written programs (I'm not a stickler about commenting, vectorizing, etc.), but it should do the job on point sources:
Removes detector crosstalk and capacitive coupling (parameters worked out by Terry Herter), and optionally returns the calculated photon noise in each pixel as an array of variances. You can use this in place of the IDL Astro library routine 'readfits' or 'mrdfits':
tspec_clean.pro
Creates a flat and optionally returns the read noise variances and a bad pixel mask given dome flats and dome darks. (Add the read noise variances from this to the photon noise variances returned by tspec_clean and pass that to tspec_calibrate and tspec_extract):
tspec_flatfield.pro
Locates the position of a star on the detector and calibrates the width of the Gaussian profile (use this on a bright target in the same slit location as your faint target):
tspec_calibrate.pro
Extracts spectra using the Gaussian and Optimal Extraction. Ignores poorly fitting points (cosmic rays, detector anomalies, etc.):
tspec_extract.pro
A program for calculating the wavelength and slit solution for the detector. Required by tspec_calibrate and tspec_extract:
poly2d_tspec.pro
File containing parameters for the wavelength and slit solution for the detector (parameters worked out by Terry Herter), required by everything. Just put it in the same folder as the routines, and the routines will find it:
tspecdat.idl
You can download all of these files as a bundle here:
tspec_extract.zip