3 research outputs found
Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing through Galaxy Clustering
We report the serendipitous discovery of two strong gravitational lens
candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with
the Advanced Camera for Surveys on the Hubble Space Telescope, each less than
40 arcsec from the previously known gravitational lens system CLASS B1608+656.
The redshifts of both lens galaxies have been measured with Keck and Gemini:
one is a member of a small galaxy group at z~0.63, which also includes the
lensing galaxy in the B1608+656 system, and the second is a member of a
foreground group at z~0.43. By measuring the effective radii and surface
brightnesses of the two lens galaxies, we infer their velocity dispersions
based on the passively evolving Fundamental Plane (FP) relation. Elliptical
isothermal lens mass models are able to explain their image configurations
within the lens hypothesis, with a velocity dispersion compatible with that
estimated from the FP for a reasonable source-redshift range. Based on the
large number of massive early-type galaxies in the field and the number-density
of faint blue galaxies, the presence of two additional lens systems around
CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are
predominantly early-type galaxies, which are clustered, and the lensed quasar
host galaxies are also clustered. Therefore, obtaining deep high-resolution
images of the fields around known strong lens systems is an excellent method of
enhancing the probability of finding additional strong gravitational lens
systems.Comment: Submitted to ApJ. 8 pages, 6 figure
Preliminary optical design for a 2.2 degree diameter prime focus corrector for the Blanco 4 meter telescope
We describe a five element corrector for the prime focus of the 4 meter Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile that will be used in conjunction with a new mosaic CCD camera as part of the proposed Dark Energy Survey (DES). The corrector is designed to provide a flat focal plane and good images in the SDSS g, r, i, and z filters. We describe the performance in conjunction with the scientific requirements of the DES, particularly with regard to ghosting and weak-lensing point spread function (PSF) calibration
Report of the Dark Energy Task Force
Dark energy appears to be the dominant component of the physical Universe, yet there is no persuasive theoretical explanation for its existence or magnitude. The acceleration of the Universe is, along with dark matter, the observed phenomenon that most directly demonstrates that our theories of fundamental particles and gravity are either incorrect or incomplete. Most experts believe that nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration. For these reasons, the nature of dark energy ranks among the very most compelling of all outstanding problems in physical science. These circumstances demand an ambitious observational program to determine the dark energy properties as well as possible