Astron. Astrophys. 320, 167-171 (1997)

2. Observations and data reduction

Optical imaging observations towards Class II YSOs in Bok globules (Yun & Clemens 1995) were carried out during the nights of 1993 December 13-16 using the European Southern Observatory 0.9 m Dutch telescope equipped with a 512 512 pixel CCD detector. Images were obtained using a set of filters which included broad-band B, V, R, I filters. The detector was used at a plate scale of 0.46 arcsec per pixel, resulting in a field of view of 3.9 3.9 arcmin² on the sky. In addition, in 1994 December and 1995 December, we obtained medium resolution ( 7Å per pixel) optical spectra and additional R-band images, using the ESO Danish 1.54 m telescope equipped with the Danish Faint Object Spectrograph and Camera (DFOSC) detector. Calibration lamps (He and Ne) were observed immediately before or after each object spectrum.

Near-infrared observations were made in 1993 December 20 using the IRAC2 NICMOS 3 infrared array camera mounted on the ESO 2.2 m telescope. We obtained a set of 9 dithered frames in the JHK-bands, with a total integration time per frame of 30 seconds.

Standard CCD image reduction procedures (dark and bias subtraction, and flat-fielding) were applied to the optical CCD images, using the NOAO Image Reduction and Analysis Facility (IRAF ¹). Similarly, standard IRAF packages were used to make the spectroscopic reductions (SPECRED).

Reduction of the near-infrared images were performed by subtraction of a sky frame (computed by median filtering of the 9 dithered images) followed by flat-fielding. The final flat-fielded images were subsequently corrected for the presence of bad pixels and mosaicked, co-adding the overlapping regions.

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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