Observations of the new gravitational lens system UM 673 = Q 0142-100.
Abstract
In order to better understand the effects of gravitational lensing on the observed quasar luminosity function, on the source counts of extragalactic objects, etc., we have recently initiated a high resolution direct imaging survey of a selected sample of Highly Luminous Quasars (HLQs). The observations are being carried out with the 2.2 m telescope at ESO, and with the VLA at the NRAO, New Mexico. Following a first observing run at ESO, we have reported the discovery of a new gravitational lens system for the HLQ UM 673 = Q0142-100. Additional observations supporting this interpretation are discussed here. We confirm that UM 673 is resolved into two quasi-stellar images A(m_V_=17.0) and B(m_V_=19.1) separated by 2.22" and having essentially the same redshift (z_e_=2.719 with z_e_(A)- z_e_(B)=-0.0002 +/-0.0008). Their emission (Lyα, N V, Si IV, C IV, etc.) as well as absorption (including a high ionization system at z_a_=2.3564) line spectra also appear to be quite identical. Further evidence for the presence of a lensing galaxy (m_R_=19, z_g_=0.49) between the two QSO images is given by the detection of faint absorption lines due to Ca II H and K, and possibly Na I D1 and D2, at a redshift z=0.493 in the spectrum of UM 673 B. Application of gravitational optometry to this system is given in the present article: a value of M_0_ = 2.4 10^11^ M_sun_ is derived for the mass of the lensing galaxy located between UM 673 A and B and a most likely estimate of {DELTA}t = 7 weeks is found for the expected delay between the arrival times of a similar variability event in the two lensed images of the quasar (H_0_=75 km s^-1^ Mpc^-1^, q_0_=0). A VLA observation of UM 673 has been obtained at 6 cm in the hybrid C/D-array configuration. This radio map indicates the presence of a faint elongated structure which is possibly associated with the UM 673 gravitational lens system.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1988
- Bibcode:
- 1988A&A...198...49S
- Keywords:
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- Astronomical Spectroscopy;
- Gravitational Lenses;
- Quasars;
- Absorption Spectra;
- Astronomical Maps;
- Emission Spectra;
- Galactic Mass;
- Line Spectra;
- Very Large Array (Vla);
- Astrophysics