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Session 68 - Disk Galaxies.
Display session, Wednesday, January 15
The darkest K band skies from any ground based site are available on the Antarctic plateau. Shortward of 2.27 \mu m, OH airglow blankets the spectrum. Between 2.27 \mu m and the atmospheric cutoff of the K window, the thermal radiation from the telescope and sky that dominates the background at mid latidude sites drops precipitously due to the extreme temperatures of the Antarctic winter (often below -60C). The 16.8 mag arcsec^-2 background in the K_dark (2.27-2.43 micron) bandpass offers the ability to reach unprecedented depth, particularly for extended sources. Over large areas, flatfielding is possible to only a fixed fraction of the sky background, typically 0.1%. For this reason, surface photometry in the K_dark band is possible from the South Pole reaching 2-3 magnitudes fainter than any other ground based site. During the 1996 Austral winter, the South Pole Infrared Explorer (SPIREX) 60cm telescope took deep K_dark images of southern spiral galaxies. These images reach 23.7 mag arcsec^-2 with SNR=1 over 8x8 arcmin fields. In these data, the edge-on Sc galaxy ESO/Uppsala 240-G11 shows evidence of an near infrared halo similar to that recently observed around NGC5907. Ongoing analysis and additional data will determine whether this emission is the tail of the known spheroid component, or if it maps a dark matter halo.
Program listing for Wednesday