NOAO >   Observing Info >   Approved Programs >   2018A-0184

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Program Information for 2018A-0184


PI: Courtney Crawford, U. of Oklahoma, courtneylaurencrawford@ou.edu
Address: Department of Physics and Astronomy, Room 131 Nielsen Hall, Norman, OK, 73019-0225 USA

CoI: Kyra Dame, U. of Oklahoma
CoI: Jeff Munn, US Naval Observatory
CoI: Mukremin Kilic, U. of Oklahoma

Title: J and H Photometry of Ultracool White Dwarfs

Abstract: We have recently identified 2839 disk and 135 halo white dwarfs based on proper motion measurements from our Bok 90inch and USNO 1.3m telescope data over 3,000 square degrees. We have also constructed disk and halo luminosity functions, and used them to constrain the ages of the Galactic disk and halo. These ages rely heavily on the faintest, and coolest stars in the sample, which have temperature/age estimates based on our model fits to the SDSS optical photometry. However, the spectral energy distributions of ultracool white dwarfs peak near 1 micron. Further, white dwarf temperatures are sensitive to the relative contributions of hydrogen and helium in their atmospheres. While atmospheric composition has negligible effect on optical colors, it has easily distinguishable effects on infrared colors. Hence, temperatures based on optical photometry alone cannot be trusted. Here we propose to obtain NIRI J and H-band observations of all 32 ultracool white dwarfs (that are visible in 2018A) in our disk and halo luminosity functions to constrain their atmospheric compositions and temperatures precisely. All of our targets are predicted to be cooler than 4000 K, and older than 9 Gyr (white dwarf cooling age). NIRI observations will give us 32 independent age estimates for the Galactic disk and halo.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2018A):  GEM-NQ/NIRI -- 15.8hrs band 3 (GN-2018A-Q-322 )


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2018A-0184

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