Spectroscopy of Gravitational Lens Candidates from the HST Survey of BL Lac Objects

Scarpa, Riccardo
Bibliographical reference

HST Proposal ID #8135

Advertised on:
7
1999
Number of authors
1
IAC number of authors
0
Citations
0
Refereed citations
0
Description
We propose spectroscopic observations of two new gravitational lens candidates, 0502+675 and 1440+122, discovered in our HST R-band snapshot survey of ~100 BL Lac objects. Each contains a double point source with separation of only 0.3 arcsec. In each case, a candidate for the lensing galaxy is also found. For 0502+675, a subsequent NICMOS H-band image shows that the two point sources have similar R-H colors. STIS long-slit spectra of each point source will determine whether these candidates are lenses and also measure the redshift of the possible lensing galaxy. Due to the small image separation, HST spatial resolution is essential. These two sources, if confirmed as lenses, are particularly valuable for estimating H_0 because of the large amplitude and rapid flux variability that characterize BL Lac objects.