Astron. Astrophys. 334, 609-617 (1998)

2. Observation and results

The stars selected for the present work have [12-25] ¹ which corresponds to the region VII of VH (0.160 [12-25] 1.156), whatever is their 60 µm flux quality. The samples selected are thus limited by the quality of 25 µm fluxes and not, as in our previously studied samples, by the quality of 60 µm fluxes (Paper I).

We have completed the observations of the anticenter sample already presented in paper I () in the latitude range b and considered new samples in the 2 directions: ( l : intermediate 1) and ( l : intermediate 2) in the same range of latitude (Table 1). These latter directions have been selected to avoid contamination by massive young stellar objects that may have comparable infrared colours. The observed areas avoid the peaks of 5 GHz emission (Haynes et al. 1978), that might indicate active star formation.

Table 1. Description of the 5 samples discussed in the text. All stars have 0.160 [12-25] 1.156 and good quality fluxes at 12 and 25 µm.
Notes: Epchtein et al. 1987, 1990; Fouqué et al. 1992; Guglielmo et al. 1993

Observations have been carried out between 9-19 of January 1993 using the standard ESO infrared photometer (Moorwood, 1982) attached to the ESO 1-m telescope. The near-IR counterparts were searched for around the IRAS positions, in most cases in the L band. Photometric measurements were done through a 15" aperture. The beam-switching was achieved in the East-West direction with a throw of 20". The JHKL fluxes were calibrated according to the ESO system (Koornneef 1983). Photometric accuracies are given in Table 2. The IRAS positions are usually good to 10 arcsec. As this accuracy is of the same order as the one of the ESO 1-m telescope in relative pointing (5-10 arcsec.), we have not attempted to improve the IRAS positions.

Table 2. Mean errors on photometric data

Observational results are listed in Table 3. Column 1 gives the IRAS name, Col. 2 the K magnitude, Cols. 3 to 8 the infrared colours, Col. 9 and 10 the VH and Epchtein et al. (1987) classifications, Col. 11 indicates previous identifications in usual catalogues, as detailed in Table 4.

Due to lack of observing time, only a fraction of the samples could be measured. This fraction is indicated in Table 1 as well as for 2 other directions observed for Paper I (inner disk and center), that are also discussed in Sect. 3.2. Observations in the anticenter, intermediate 1 and inner samples are essentially complete, but the center and intermediate 2 samples are still poorly observed.

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998

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