The FORS Deep Field (FDF)

BRI composite-image of the FORS Deep Field
The FORS Deep Field (FDF)

1. The project

The FORS Deep Field (FDF) was established as a key project by the FORS consortium (Landessternwarte Heidelberg, Universitäts-Sternwarte Göttingen and Universitätssternwarte München) in order to make efficient use of the guaranteed time granted to the consortium in compensation for building the two FORS instruments attached to the VLT telescopes. The PI of the FDF is I. Appenzeller. In addition the FDF is one of the main topics within projects supported by the Deutsche Forschungsgemeinschaft (SFB 439 "Galaxies in the young Universe", Heidelberg; SFB 375 "Astro particle physics", Munic) and the Volkswagen Foundation (I/76 520 "Kinematic evolution of galaxies", Göttingen).

2. Scientific motivation

Undoubtedly, the Hubble Deep Field North and follow-up observations with Keck were of particular importance to improove our knowledge of galaxy evolution in the redshift range z = 1-4. However, due to its relatively small field of view (~5.6sq.arcmin.) the results obtained are subject to large-scale variations and limitations due to small samples. The main aim of the FDF is to probe the galaxy evolution up to z~5. The FDF programme has been carried out mostly with the ESO VLT and FORS instruments at a site, which offers excellent seeing conditions and allows imaging to almost the depths of the HDFs. The larger field of view compared to the HDFs (about 4 times the combined HDFs) alleviates the problem of the large-scale structure and results in larger samples of interesting objects. Moreover, spectroscopic follow-up studies with FORS can make full use of the entire field. Using the FORS2 MXU-facility, up to ~60 spectra of objects down to m_I = 25 can be taken simultaneously.

3. Characteristics of the FDF

The location of FDF was chosen according to restrictions typical for classical pencil-beam surveys. Amongst them are low galactic extinction, absence of bright radio and x-ray sources, low HI column density and FIR cirrus emission, and the absence of bright stars in the field. To maximize the observability of the FDF from the VLT-site a region near the south galactic pole was chosen. To study the IGM along the linie-of-sight a high-redshift (z > 3) Quasar had to be incorporated. In the end a region containing the QSO Q0103-260 (z = 3.36) was chosen as the FDF. The field selection is described in Heidt et al. (2003). The main characteristics of the FDF are summarized in Table 1.
Table 1 Characteristics of the FDF
Field center 1h 6m 3.6s -25° 45' 46" (2000)
mean E(B-V) 0.018
HI column density 1.92 • 1020 cm-2
Radio sources (NVSS) non with flux > 2.5 mJy
IRAS Cirrus (100 μm) 0.035 Jy
Bright stars (<5 mag) none within 5°

4. Observations

Since 1999 photometric observations in the optical have been obtained in broad-band UBgRI and medium-band z-filters with FORS1/2 at the VLT telescopes. In addition, narrow-band images centered at 4850, 5300, 8100, 8150, 8230 and 8340 Å were taken to search specifically for Lyα-galaxies at the redshift of Q 0136-260 and z ~ 5.7. The data were complemented by J and Ks-observations in the NIR with SofI at the ESO-NTT. Finally, the FDF was observed with the VLA at 1.6 GHz and 5 GHz. A broad-band photometric catalog containing about 8700 objects in the FDF have been published by Heidt et al. (2003) and can be found here.
Using the photometric data photometric redshifts were estimated for about 5000 objects in the FDF. Follow-up spectroscopical observations of about 500 FDF objects with FORS1/2 at the VLT telescopes have been carried out since 1999. For about 340 FDF objects redshifts and types could be derived. The spectroscopic catalog has been published by Noll et al. (2004) and can be found here.

5. Scientific projects

A summary of the scientific highlights obtained so far in "Exploring cosmic evolution with the FORS Deep Field", by Appenzeller et al. 2004, The Messenger 116, 18.

6. Further information

The FDF-team

Publications obtained from the FORS Deep Field


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Maintained by Jochen Heidt
Last modified: 26.09.2008