Artículo de revista
A close separation double quasar lensed by a gas-rich galaxy
Fecha
2000-06Registro en:
Astronomical Journal, 119:2535-2539, 2000 June
1538-3881
Autor
Gregg, Michael D.
Wisotzki, Lutz
Becker, Robert H.
Maza Sancho, José
Schechter, Paul L.
White, Richard L.
Brotherton, Michael S.
Winn, Joshua N.
Institución
Resumen
In the course of a Cycle 8 snapshot imaging survey with the Space Telescope Imaging Spectrograph
(STIS), we have discovered that the z\1.565 quasar HE 0512[3329 is a double with image separation
0A.644, di ering in brightness by only 0.4 mag. This system is almost certainly gravitationally lensed.
Although separate spectra for the two images have not yet been obtained, the possibility that either
component is a Galactic star is ruled out by a high signal-to-noise composite ground-based spectrum
and separate photometry for the two components: the spectrum shows no trace of any zero-redshift
stellar absorption features belonging to a star with the temperature indicated by the broadband photometry.
The optical spectrum shows strong absorption features of Mg II, Mg I, Fe II, Fe I, and Ca I, all at
an identical intervening redshift of z\0.9313, probably due to the lensing object. The strength of Mg II
and the presence of the other low-ionization absorption features is strong evidence for a damped Lya
system, likely the disk of a spiral galaxy. Point-spread function Ðtting to remove the two quasar components
from the STIS image leads to a tentative detection of a third object, which may be the nucleus
of the lensing galaxy. The brighter component is signiÐcantly redder than the fainter, due to either di erential
extinction or microlensing.