Astron. Astrophys. 344, 632-638 (1999)

2. Observations

2.1. Optical images

Optical images were obtained in October 1991 with the High Resolution Camera (HR Cam) of the CFHT. This camera enabled us to obtain images with spatial resolution of 0.5-0.8 arcsec (500-800 AU at NGC 7129). We employed the SAIC 1 CCD which has a field of view of 2.2 x 2.2 arcmin and a pixel size of 18 µm. The scale is 0.13 arcsec/pixel (see McClure et al. 1989for details on HR Cam).

We obtained images in two narrow band filters with the specifications; H ( Å and FWHM = 30 Å) and [S II] ( Å and FWHM = 47 Å; both 6716 Å and 6731 Å lines are transmitted). We also used a broad band I filter. We obtained four images in each bandpass for a total exposure time of 1 hour in the narrow band filters and a total of 15 minutes for the I band image. The data were reduced using the Munich Image Data Analysis System. Images are bias-corrected and flat-fielded in the standard manner. Images with similar good seeing have been co-added to obtain the images shown in Fig. 1.

Fig. 1. Optical images of GGD 34. The condensations are named following Gómez de Castro et al. (1993) in order of increasing right ascension. The orientation corresponding to position angle +79o is shown by a straight line. The 5 main knots are marked on top of the H image. The position of the radio source is also marked with an asterisk.

2.2. 3.6 cm and 6 cm radiocontinuum observations

The GGD 34 region was observed at 3.6 and 6 cm using the Very Large Array of NRAO. The dates and other parameters of the observations are given in Table 1. The observations were made in the continuum mode with an effective bandwidth of 100 MHz. The data were calibrated and natural weight maps were made using the tasks of the Astronomical Image Processing System. The 3.6 cm data was tapered slightly to produce 3.6 and 6 cm maps of comparable angular resolution (about 5 arcsec). The maps are shown in Fig. 2. A faint, unresolved radio source was detected south west of GGD 34. The parameters of this source are given in Table 2.

Fig. 2. VLA maps at 6 cm (top panel ) and 3.6 cm (bottom panel ) of the GGD 34 region. The synthesized beam is shown in the bottom left corner of each panel. The contours are -3, 3, 4, 5, 6, and 7 times the rms noise of the maps (27 µJy for 6 cm and 21 µJy for 3.6 cm).

Table 1. GGD 34 VLA observations

Table 2. Parameters of detected VLA source

2.3. ¹²CO(3-2) observations

A low resolution mosaic of ¹²CO(3-2) emission (excited molecular gas) around GGD 34 was kindly provided by R. Padman. The ¹²CO(3-2) observations were made with the James Clerk Maxwell Telescope (JCMT) in January 1993. The map is centred at (1950)=18:s28, (1950)=65^o 55´ 00" coinciding approximately with the position of the central condensation: GGD 34/B. The spatial resolution of the map is of 14". The grid of observed positions consists of an ensemble of 5 parallel east-west strips sampled every 7". The sampling in the north-south direction was the same but 7 strips were made in total.

© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999
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