Bibcode
DOI
Scarpa, Riccardo; Urry, C. Megan; Falomo, Renato; Pesce, Joseph E.; Webster, Rachel; O'Dowd, Matthew; Treves, Aldo
Referencia bibliográfica
The Astrophysical Journal, Volume 521, Issue 1, pp. 134-144.
Advertised on:
8
1999
Revista
Número de citas
44
Número de citas referidas
41
Descripción
We present Hubble Space Telescope (HST) observations of seven unusual
objects from the HST ``snapshot survey'' of BL Lacertae objects, of
which four are gravitational lens candidates. In three cases a double
point source is observed: 0033+595, with 1.58" separation, and 0502+675
and 1440+122, each with ~0.3" separation. The last two also show one or
more galaxies, which could be either host or lensing galaxies. If any
are confirmed as lenses, these BL Lac objects are excellent candidates
for measuring H_0 via gravitational time delay because of their
characteristic rapid, high-amplitude variability. An additional
advantage is that, like other blazars, they are likely superluminal
radio sources, in which case the source plane is mapped out over a
period of years, providing strong additional constraints on the lensing
mass distribution. The fourth gravitational lens candidate is 1517+656,
which is surrounded by three arclets forming an almost perfect ring of
radius 2.4". If this is indeed an Einstein ring, it is most likely a
background source gravitationally lensed by the BL Lac object host
galaxy and possibly a surrounding group or cluster. In the extreme case
that all four candidates are true lenses, the derived frequency of
gravitational lensing in this BL Lac sample would be an order of
magnitude higher than in comparable quasar samples. We also report on
three other remarkable BL Lac objects: 0138-097, which is surrounded by
a large number of close companion galaxies; 0806+524, whose host galaxy
contains an uncommon arclike structure; and 1959+650, which is hosted by
a gas-rich elliptical galaxy with a prominent dust lane of ~5x10^5
M_solar.