Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userHE 1113-0641: The Smallest Separation Gravitational Lens Identified by a Ground-based Optical Telescope
228
0
0.0
(
0
)
Authors
Jeffrey A. Blackburne MIT
Ask ChatGPT about the research
No Arabic abstract
The Hamburg/ESO quasar HE 1113-0641 is found to be a quadruple gravitational lens, based on observations with the twin 6.5m Magellan telescopes at the Las Campanas Observatory, and subsequently with the Hubble Space Telescope. The z_S=1.235 quasar appears in a cross configuration, with i band magnitudes ranging from 18.0 to 18.8. With a maximum image separation of 0.67, this is the smallest-separation quadruple ever identified using a ground-based optical telescope. PSF subtraction reveals a faint lensing galaxy. A simple lens model succeeds in predicting the observed positions of the components, but fails to match their observed flux ratios by up to a magnitude. We estimate the redshift of the lensing galaxy to be z_L~0.7. Time delay estimates are on the order of a day, suggesting that the flux ratio anomalies are not due to variability of the quasar, but may result from substructure or microlensing in the lens galaxy.
rate research
Read More
We report the discovery of a new gravitationally lensed QSO, at a redshift z = 1.689, with four QSO components in a cross-shaped arrangement around a bright galaxy. The maximum separation between images is 2.6 arcsec, enabling a reliable decomposition of the system. Three of the QSO components have g = 19.6, while component A is about 0.6 mag brighter. The four components have nearly identical colours, suggesting little if any dust extinction in the foreground galaxy. The lensing galaxy is prominent in the i band, weaker in r and not detected in g. Its spatial profile is that of an elliptical galaxy with a scale length of $sim$ 12 kpc. Combining the measured colours and a mass model for the lens, we estimate a most likely redshift range of 0.3 < z < 0.4. Predicted time delays between the components are $la$ 10 days. The QSO shows evidence for variability, with total g band magnitudes of 17.89 and 17.71 for two epochs separated by $sim 2$ months. However, the relative fluxes of the components did not change, indicating that the variations are intrinsic to the QSO rather than induced by microlensing.
We report the discovery of the new gravitational lens system HE~0230$-$2130, a QSO at redshift $z=2.162$ consisting of at least five distinct components. Three of these are clearly lensed images of the QSO, one is most likely the lensing galaxy, while for the fifth component the identity is unclear: It could be a fourth QSO image (if so, then highly reddened), or another intervening galaxy, or a superposition of the two. Differential reddening seems to be important also for the first three QSO images. The surface density of faint galaxies near the QSO appears to be enhanced by a factor of $ga 2$, indicating the presence of a distant cluster close to the line of sight.
The lens candidate RXJ 0921+4529 consists of two z_s=1.66 quasar separated by 6.93 with an H band magnitude difference of Delta m=1.39. The lens appears to be a z_l=0.31 X-ray cluster, including a m_H=18.5 late-type galaxy lying between the quasar images. We detect an extended source overlapping the faint quasar but not the bright quasar. If this extended source is the host galaxy of the fainter quasar, then the system is a quasar binary rather than a gravitational lens.
We present observations of CLASS B2108+213, the widest separation gravitational lens system discovered by the Cosmic Lens All-Sky Survey. Radio imaging using the VLA at 8.46 GHz and MERLIN at 5 GHz shows two compact components separated by 4.56 arcsec with a faint third component in between which we believe is emission from a lensing galaxy. 5-GHz VLBA observations reveal milliarcsecond-scale structure in the two lensed images that is consistent with gravitational lensing. Optical emission from the two lensed images and two lensing galaxies within the Einstein radius is detected in Hubble Space Telescope imaging. Furthermore, an optical gravitational arc, associated with the strongest lensed component, has been detected. Surrounding the system are a number of faint galaxies which may help explain the wide image separation. A plausible mass distribution model for CLASS B2108+213 is also presented.
We study the optical properties of an oblate gravitational lens, such as the solar gravitational lens, which, in addition to a monopole, is characterized by the presence of a small quadrupole zonal harmonic. We obtain a new type of diffraction integral using our recently developed angular eikonal method. We evaluate this integral using the method of stationary phase. The resulting quartic equation can be solved algebraically using the method first published by Cardano in 1545. We find that the resulting solution provides a good approximation to the electromagnetic field almost everywhere in the image plane, yielding the well-known astroid caustic of the quadrupole lens. The sole exception is the immediate vicinity of the caustic boundary, where a numerical treatment of the diffraction integral yields better results. We also convolve the quartic solution with the point-spread function of a thin-lens optical telescope. We explore the direct relationship between the algebraic properties of the quartic, the geometry of the astroid caustic, and the geometry and shape of the resulting Einstein-cross that appear on the image sensor of the model telescope. This leads to improvements in numerical simulations as the quartic solution is computationally far less expensive than numerical integration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
