The Gravitational Lens System Q0957+561 in the Ultraviolet
Abstract
Photometric and polarimetric observations of both images of the gravitationally lensed quasar Q0957 + 561 (z_em_ = 1.41) were obtained in the UV in 1993 with the High Speed Photometer on board the Hubble Space Telescope. The images exhibited no significant polarization in a bandpass centered on 2770 A (observer's frame); p <= 3.2% (2 σ upper limit) in each image. The ratio of the flux density in image A to that in image B in late 1993 had a constant value, 1.021 +/- 0.008, in four different UV bandpasses between 1400 A and 3040 A (observer's frame). These results are consistent with the prediction of the gravitational lens interpretation that the photometric ratio of the images measured simultaneously should be independent of frequency. Reprocessed archival spectra of the two images obtained between 1981 and 1983 by the International Ultraviolet Explorer show that the photometric ratio of A to B varies between 0.96 and 2.0 in the Lyα emission line, and between 0.77 and 1.8 in the O VI λ1037 emission line (quasar rest frame). The photometric ratio of A to B at any single epoch is often significantly different in the two emission lines. Accepting the system as a gravitational lens implies that in the quasar the flux in the Lyα emission line can vary independently of the flux in the O VI emission line.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/175425
- Bibcode:
- 1995ApJ...442...87D
- Keywords:
-
- Astronomical Polarimetry;
- Galaxies;
- Gravitational Lenses;
- Lyman Alpha Radiation;
- Quasars;
- Ultraviolet Photometry;
- Flux Density;
- Hubble Space Telescope;
- Image Analysis;
- Iue;
- Spectrum Analysis;
- Astrophysics;
- COSMOLOGY: GRAVITATIONAL LENSING;
- GALAXIES: QUASARS: INDIVIDUAL ALPHANUMERIC: 0957;
- 561;
- POLARIZATION;
- ULTRAVIOLET: GALAXIES