New Debris Disks With Spitzer Space Telescope Heidi Larson, David Koerner, Sam Kim Northern Arizona University

What are Debris Disks? Circumstellar disks made up of dust All stars have a protostellar disk at formation, but this dissipates in less than 107 years Circumstellar dust that remains for longer timescales is thought to originate from collisions of larger rocky bodies, called planetesimals

How are Debris Disks Detected? Dust absorbs light from the star at higher frequencies and re-radiates it at lower infrared frequencies.

Spitzer Space Telescope & MIPS The Multiband Imaging Photometer (MIPS) on the Spitzer Space Telescope takes images at 24, 70, and 160 microns. Our data were taken at 24 and 70 microns Warm dust near the star is most easily detected at 24 microns Colder dust from the outer disk can be detected at 70 microns. Many debris disks consist entirely of a cold outer disk

Survey Sample 634 stars within 25 parsecs with magnitudes V<9, (stars earlier than M0) Some stars had high background emission at 70 microns and were omitted, leaving 436 stars observed at 70 microns

MIPS Photometry Measure flux density (Watts per unit area per unit frequency) in an image at a particular frequency. Subtract sky background emission Subtract noise from the telescope and detector

Excess Identification With SED Fitting Fit photosphere model to optical and near infrared measurements Fit blackbody curve to 24 or 70 micron points that lie above photosphere emission

Results 42 sources at 24 microns and 25 at 70 microns with excesses above 3 sigma One object with excess at both 24 and 70 microns Contrary to previous surveys, we did not find a correlation between late type stars and a lack of disk detections