• The contour intervals are
  • 1, 2, 3, 4, 5, 10, 25, 50 and 75% of peak at 850um and
  • 2, 4, 6, 8, 10, 25, 50 and 75% of peak at 450um.

HL Tau has a compact unresolved core, but the star is associated with faint extended emission, clearly visible above the error beam both at 850 and 450 micron. The measured FWHM is 14.8" at 850 micron and 8.0" at 450 micron, while the corresponding values for CRL618 in the same time period are 14.7" and 7.9" for 850 and 450 micron, respectively. At 850 micron it is estimated that HL Tau contributes to about 430 mJy in a 30" radius and about 960 mJy in a 60" radius surrounding the star. For 450 micron the amount of extended emission is more uncertain, because examining data over December 1997 show variations of the integrated error lobe of the order of 15 - 20 % for benign conditions. However, the corresponding estimates are about 2.3 Jy and 3.6 Jy for 60 and 120" apertures, respectively. Most of the extended emission is relatively compact and at low level, but it is recommended not to observe HL Tau with chop throws shorter than 60".

GS has data taken with a 120" azimuth chop and the source setting that produces negative emission in the SW of the reconstructed map : as if the chopping was onto other emisison. It is unlikely to significantly affect the flux of HLTau, and needs verifying.

There is no indication of variability in the 850um data taken between 1998 and 2001.