3.1 Instrumental Setup for the DFOSC April 1994 Observing Run

Table

below describes the instrumental setup for the April 1994 observing run with the Danish 1.5 meter telescope, La Silla, equipped with the DFOSC instrument. The data from this observing run will be referred to as the DFOSC data, or just DFOSC. The entire HydraI photometry sample used in this work is based on the DFOSC data, cf. the remaining sections of this chapter and Chapter

. Part of the HydraI spectroscopy sample used in this work is also based on the DFOSC data, cf. Chapter

Note that the Coma sample also used in the analysis (Chapter

) is not introduced until Sect.

Table: Instrumental Setup for the DFOSC April 1994 Observing Run

General information

Dates April 7-8 to April 21-22, 1994 (night 0-14)

Observer Inger Jørgensen

Observatory ESO, La Silla, Chile

Telescope Danish 1.5 m

Instrument DFOSC

CCD ESO #17

CCD size 1024 pixels $\times$ 1024 pixels

Pixel size 0.5073 arcsec/pixel

Read-out-noise 4.39 e^-

Conversion factor 1.95 e^-/ADU

CCD temperature 129 K (night 0-5), 139.5 K (night 6-14)

Dark current 10.9 e^-/h (night 0-5), 33.7 e^-/h (night 6-14)

Information specific to the photometry

Field size $8.7' \times 8.7'$

Passbands for the galaxy photometry $^{\rm a}$ Gunn r, Johnson B, and Johnson U

Number of HydraI fields observed 43 $^{\rm b}$ (see Fig. , p. )

Information specific to the spectroscopy

Wavelength range 4954.2-5612.5 Å

Slitwidth 2.5 arcsec

Instrumental dispersion ( $\sigma$ ) $^{\rm c}$ 1.36 Å, 79 km/s

Grism #13 + order sorter filter

CCD Readout window 401 pixels (spatial) $\times$ 1024 pixels ( $\lambda$ )

Binning $1 \times 1$

Number of HydraI E and S0 galaxies observed 21 $^{\rm d}$

Notes: $^{\rm a}$ In addition Johnson V was used for standard star observations. $^{\rm b}$ In Johnson U only 5 HydraI fields were observed. $^{\rm c}$ The instrumental dispersion is determined as sigma in a Gaussian fit to the 5577 Å sky emission line. The equivalent dispersion in km/s is determined at 5177 Å. $^{\rm d}$ In total 35 E and S0 galaxies were observed: 21 in HydraI, 9 in Abell 3574, and 5 in the field. All the galaxies were used in the comparison with the literature, cf. Sect.