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Register a new userDiscovery of a Quadruple Lens in CANDELS with a Record Lens Redshift z=1.53
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Using spectroscopy from the Large Binocular Telescope and imaging from the Hubble Space Telescope we discovered the first strong galaxy lens at z(lens)>1. The lens has a secure photometric redshift of z=1.53+/-0.09 and the source is spectroscopically confirmed at z=3.417. The Einstein radius (0.35; 3.0 kpc) encloses 7.6 x 10^10 Msol, with an upper limit on the dark matter fraction of 60%. The highly magnified (40x) source galaxy has a very small stellar mass (~10^8 Msol) and shows an extremely strong [OIII]_5007A emission line (EW_0 ~ 1000A) bolstering the evidence that intense starbursts among very low-mass galaxies are common at high redshift.
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We report the serendipitous discovery of a quadruply-lensed source behind the z=0.095 edge-on disk galaxy 2MASXJ13170000-1405187, based on public imaging survey data from Pan-STARRS PS1 and the VISTA Hemisphere Survey. Follow-up imaging from Magellan/LDSS3 shows that the background source is spatially extended (i.e. not a QSO), and that two of the lensed images are observed through a prominent dust ring in the disk of the lens galaxy. We summarise results of preliminary modelling, which indicates an Einstein radius of 1.44 arcsec, and a K-band mass-to-light ratio of 0.5, relative to the solar value.
High resolution MERLIN observations of a newly-discovered four-image gravitational lens system, B0128+437, are presented. The system was found after a careful re-analysis of the entire CLASS dataset. The MERLIN observations resolve four components in a characteristic quadruple-image configuration; the maximum image separation is 542 mas and the total flux density is 48 mJy at 5 GHz. A best-fit lens model with a singular isothermal ellipsoid results in large errors in the image positions. A significantly improved fit is obtained after the addition of a shear component, suggesting that the lensing system is more complex and may consist of multiple deflectors. The integrated radio spectrum of the background source indicates that it is a GigaHertz-Peaked Spectrum (GPS) source. It may therefore be possible to resolve structure within the radio images with deep VLBI observations and thus better constrain the lensing mass distribution.
We report the discovery of a multiply lensed Ly Alpha (Lya) emitter at z = 3.90 behind the massive galaxy cluster WARPS J1415.1+3612 at z = 1.026. Images taken by the Hubble Space Telescope(HST) using ACS reveal a complex lensing system that produces a prominent, highly magnified arc and a triplet of smaller arcs grouped tightly around a spectroscopically confirmed cluster member. Spectroscopic observations using FOCAS on Subaru confirm strong Lya emission in the source galaxy and provide redshifts for more than 21 cluster members, from which we obtain a velocity dispersion of 807+/-185 km/s. Assuming a singular isothermal sphere profile, the mass within the Einstein ring (7.13+/-0.38) corresponds to a central velocity dispersion of 686+15-19 km/s for the cluster, consistent with the value estimated from cluster member redshifts. Our mass profile estimate from combining strong lensing and dynamical analyses is in good agreement with both X-ray and weak lensing results.
We report the serendipitous discovery of a quadruply lensed source at $z_{rm s}=3.76$, HSC~J115252+004733, from the Hyper Suprime-Cam (HSC) Survey. The source is lensed by an early-type galaxy at $z_{rm l}=0.466$ and a satellite galaxy. Here, we investigate the properties of the source by studying its size and luminosity from the imaging and the luminosity and velocity width of the Ly-$alpha$ line from the spectrum. Our analyses suggest that the source is most probably a low-luminosity active galactic nucleus (LLAGN) but the possibility of it being a compact bright galaxy (e.g., a Lyman-$alpha$ emitter or Lyman Break Galaxy) cannot be excluded. The brighter pair of lensed images appears point-like except in the HSC $i$-band (with a seeing $sim0.5$). The extended emission in the $i$-band image could be due to the host galaxy underneath the AGN, or alternatively, due to a highly compact lensed galaxy (without AGN) which appears point-like in all bands except in $i$-band. We also find that the flux ratio of the brighter pair of images is different in the Ks-band compared to optical wavelengths. Phenomena such as differential extinction and intrinsic variability cannot explain this chromatic variation. While microlensing from stars in the foreground galaxy is less likely to be the cause, it cannot be ruled out completely. If the galaxy hosts an AGN, then this represents the highest redshift quadruply imaged AGN known to date, enabling study of a distant LLAGN. Discovery of this unusually compact and faint source demonstrates the potential of the HSC survey.
We use high-resolution adaptive optics (AO) imaging on the Keck II telescope to study the gravitational lens B0128+437 in unprecedented detail, allowing us to resolve individual lensed quasar components and, for the first time, detect and measure properties of the lensing galaxy. B0128+437 is a small separation lens with known flux-ratio and astrometric anomalies. We discuss possible causes for these anomalies, including the presence of substructure in the lensing galaxy, propagation effects due to dust and a turbulent interstellar medium, and gravitational microlensing. This work on B0128 demonstrates that AO will be an essential tool for studying the many new small-separation lenses expected from future surveys.
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