GC 0248+430 : a possibly micro-lensed quasar behind a tidal arm of a merging galaxy system.
Abstract
Optical observations of a new interesting case of a close angular association between a quasar (z=1.311) and a galaxy system (z=0.051) are presented. The quasar GC0248+430 is a well studied flat spectrum - variable - radio source. The galaxy system AN0248+430 consists of two galaxies in the merging process. Both nuclei show non-thermal activity. Furthermore a strong FIR flux was detected by IRAS indicating a violent starburst. The two nuclei are separated by 3.5 arcsec corresponding to a projected distance of 3.2kpc (H_0_=75 km s^-1^Mpc^-1^). A tidal arm of the disturbed galaxy system is found to be located just in front of the quasar which is 15 arcsec away from the brighter nucleus. We discuss whether the foreground galaxy system is able to cause significant gravitational macro- or micro-lens effects on observable properties of GC0248+430. Since there are probably no additional macro-lens images of the quasar, we can set an upper limit of M/L<10 (solar units) for the matter projected into a 15 arcsec radius circle around the brighter nucleus. To search for micro-lensing variability we carried out an optical photometric monitoring of the quasar since Oct. 1988. We detected variations with two different timescales corresponding to those in the radio. Both timescales can be interpreted in terms of micro-lensing. A confirmation depends on further monitoring. Then it should be possible to detect low-mass stars in the tidal arm and/or the galaxy halo and to get hints on the shape of the compact optical continuum source in the quasar. Surprisingly, our system shows many similarities to the carefully observed association between the quasar PKS 1327-206 and the disturbed galaxy ESO 1327-2041 where the quasar is at a projected distance of 13 kpc to the galaxy centre and lies very close to a tidal arm, too. Both cases are two out of only three where strong NaD absorption was detected in a quasar spectrum due to an intervening galaxy.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- March 1991
- Bibcode:
- 1991A&A...243...93B
- Keywords:
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- Active Galactic Nuclei;
- Gravitational Lenses;
- Interacting Galaxies;
- Quasars;
- Infrared Astronomy Satellite;
- Radio Sources (Astronomy);
- Stellar Spectra;
- Astrophysics