VIMOS 171.A-3045

A Large Programme 171.A-3045 (PI: Cesarsky) has been approved in period 71 to carry out a spectroscopic survey in the CDF-S with VIMOS, now installed on UT3. The Observations started in August 2004 and are going on.

Raw data and calibration files become immediately public, and can be retrieved through the ESO Science Archive Facility-VIMOS Data Products (follow the links in the table below).

Run ID Telescope Instrument Hours Priority Notes
171.A-3045(A) UT3 VIMOS 1.0 B Preimaging
171.A-3045(B) UT3 VIMOS 10.0 B MOS (LR_Blue/MR grisms)
171.A-3045(D) UT3 VIMOS 102.0 B MOS (LR_Blue/MR grisms)
171.A-3045(E) UT3 VIMOS 3.0 B Preimaging
171.A-3045(F) UT3 VIMOS 1.5 B Preimaging

The proposal is available here: gzipped ps file (220KB)

 
A VIMOS pointing (left). The VIMOS coverage of the GOODS field (right).

Overview of the VIMOS spectroscopic strategy

The cumulative source counts on the CDF-S field taken from the deep public FORS1 data, shows that at the limit of the VIMOS capability (VAB=25) there are ~6000 objects over the 160 arcmin2 of the GOODS field, or ~37 arcmin-2. Moreover, the VIMOS geometry (16' x 18', with a cross gap of 2' between the quadrants) is such that only 50% of it can overlap with the 10' x 16' GOODS field. Hence up to 400 objects at a time can be observed. 4 VIMOS pointings are required to cover the whole GOODS area. 24 masks (6 per pointing) are necessary to ensure ~96% completeness in the spectroscopic coverage of ~6000 targets. With an average integration time of 4h per mask and 30% overheads, this makes a total of 125h.

The VIMOS spectroscopic campaign is designed to complement the FORS2 spectroscopic program. A Medium resolution campaign in the red (VIMOS MR_orange grism) is dedicated to reaching the required completeness in the 0.5 < z < 1.3 redshift range. A low resolution spectroscopic campaign is conducted with the VIMOS LR_Blue grism to cover the 2.3 < z < 3.5 redshift range not considered by the FORS2 spectroscopy. The target selection is based on BzK objects (see for detail Daddi et al. 2004), u-dropouts, sub-u-dropouts and Chandra sources. The table below shows for the variuos redshift intervals the features most useful for redshift determination, and the most appropriate instrument/grism combination for detecting such features.

Redshift Key Features Instrument/grism
z < 0.5 [OII],Hbeta,[OIII],(Halpha),CaII H&K VIMOS LR_Blue
0.5 < z <1.3 [OII],Hbeta,CaII H&K VIMOS MR / FORS2
1.3 < z <2.3 [OII],CaII H&K;CIV,AlIII FORS2
2.3 < z < 3.5 Lyalpha,SiIII,CII,CIV,OI,SiIV VIMOS LR_Blue
z > 3.5 Lyalpha,SiIII,CII,CIV,OI,SiIV FORS2

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Last modified: Thu Oct 20 14:21:50 MEST 2005
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