The Pleiades reflection nebula. I. Ultraviolet, optical, and far-infrared imaging photometry.
GIBSON S.J. and NORDSIECK K.H.
Abstract (from CDS):
We present new wide-field optical and ultraviolet images of the Pleiades reflection nebula that allow a more thorough evaluation of the dust scattering than any prior data set. Vacuum-UV images were taken at 1650 and 2200 Å during the first flight of the Wide-Field Imaging Survey Polarimeter (WISP), a sounding rocket-borne telescope. WISP captured the brighter parts of the nebula at both wavelengths, with 3 σ sensitivities of 22.5 and 23.4 UV mag arcsec–2, respectively. The 5°.0x1°.7 WISP field was also mapped at 4400 Å with a mosaic of 40 Burrell Schmidt CCD frames using a broadband BJfilter. The Schmidt mosaic shows extensive and intricate nebulosity down to a 5 σ sensitivity limit of 27.6 B mag arcsec–2, including features undetected by photographic surveys. We explore the intensity and color behavior of the nebula in our UV and optical images and far-infrared IRAS data. We find that the photometric structure near bright stars is more complex than previous studies have implied, but general trends are still apparent. The color gradients around the stars are caused by phase function effects rather than internal reddening. The greater concentration of scattered light versus thermal emission indicates that most of the observed scattering is from foreground dust. A somewhat greater concentration of UV versus optical light suggests grain scattering is more forward-directed at shorter wavelengths. The UV nebula is much fainter than expected from the stellar photometry and interstellar reddening. Explaining this UV faintness requires either more reddening than is measured or significant alterations to current dust property estimates.