Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996mnras.278..139w&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 278, Issue 1, pp. 139-145.
Astronomy and Astrophysics
Astronomy
56
Gravitational Lensing
Scientific paper
We present spectroscopic and imaging observations of a candidate optical Einstein ring. The deflector is a luminous early-type galaxy, M_B_T=-20.9+5logh (q_0=0.1), at redshift z=0.485. Superposed on the otherwise normal spectrum of the galaxy is a strong emission feature at 5588A. No other emission lines are evident over the wavelength range lambdalambda4456-7912A. Narrow-band imaging of the system at the emission-line wavelength reveals a semicircular arc, radius r=1.35 arcsec, centred on the peak of the galaxy surface brightness distribution. The properties of the system can be reproduced by a gravitational lens model in which the deflector has a constant mass-to-light ratio (corrected for evolution) of M/L_B_(0)~20h and the source is an intrinsically small, but resolved, object at high redshift, either at z=3.597 (if the line is Lyalpha lambda1216), or at z=2.607 (if the line is CIV lambda1549). Alternatives to the lensing explanation, in which the emission feature is associated with [OII] lambda3727, with a velocity difference of 2900 km s^-1 relative to the absorption-line redshift of the galaxy, appear to be extremely improbable. Unambiguous identification of the system as a gravitational lens requires the detection of a second emission line, and would confirm the system as the first Einstein ring to be discovered in the optical.
Hewett Paul C.
Iovino Angela
Lewis Geraint F.
Moller Palle
Shaver Peter A.
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