SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 330, 57-62 (1998)

Previous Section Next Section Title Page Table of Contents

4. Colour of the deflector

The redshift of the lensing galaxy can be constrained by the [FORMULA] colour. In Fig. 4, we compare the colour of the candidate (the shaded region) with theoretical colours corresponding to five galaxy types. These colours were obtained from the PEGASE "Projet d'Etude des GAlaxies par Synthèse Evolutive" atlas (Leitherer et al. 1996; Fioc and Rocca-Volmerange 1997). The five types correspond to E, Sa, Sb, Sc and Sd galaxies in a critical density universe with [FORMULA] (Rocca-Volmerange and Fioc 1996). The theoretical colours are a function of redshift. The thick lines include the effect of galaxy evolution; the thin lines do not.

[FIGURE] Fig. 4. [FORMULA] as a function of redshift for different galaxy types (see Sect. 4 for more details). The shaded region shows the colour of the lensing galaxy, error bars included. The thick lines show the models which take into account galaxy evolution; the thin lines do not. A solid arrow shows the redshift of the QSO pair. The two strongest metal absorption line systems, at redshifts [FORMULA] and [FORMULA], are marked with dotted arrows.

The colour of the candidate constrains the object to be a galaxy with a redshift beyond [FORMULA], probably between z=1 and z=2. The redshifts of the two strongest metal absorption line systems, at [FORMULA] and [FORMULA] (Smette et al. 1995 and Wisotzki et al. 1993) are marked with dotted arrows in Fig. 4.

Without a firm redshift for the lens, its absolute magnitude is unknown. However, if the galaxy is between [FORMULA] and [FORMULA] (as also suggested by Smette et al. 1995) it is many times more luminous than a typical large galaxy, which would have [FORMULA]. This value we adopted for [FORMULA] is the average between the value determined by Glazebrook et al. (1995) and the one from Mobasher et al. (1993).

Previous Section Next Section Title Page Table of Contents

© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998
helpdesk.link@springer.de