We present an imaging study of the black hole binary candidate SDSS J1536+0441 (z {approx} 0.3893), based on deep, high-resolution V z K images collected at the ESO/Very Large Telescope. The images ...clearly show an asymmetric elongation, indicating the presence of a companion source at {approx}1'' ({approx}5 kpc projected distance) east from the quasar. The host galaxy of the quasar is marginally resolved. We find that the companion source is a luminous galaxy, the light profile of which suggests the presence of an unresolved, faint nucleus (either an obscured active galactic nucleus or a compact stellar bulge). The study of the environment around the quasar indicates the occurrence of a significant overdensity of galaxies with a redshift compatible with z {approx} 0.4. This suggests that it resides in a moderately rich cluster of galaxies.
PKS 2155-304 is one of the brightest BL Lac objects in the sky and a very well-studied target from radio to TeV bands. We report on high-resolution (~0".12) direct imaging of the field of PKS ...2155-304 using adaptive optics near-IR (NIR) observations in the J and K s bands obtained with the ESO Multi-Conjugate Adaptive Optics Demonstrator on the Very Large Telescope. These data are complemented with archival Very Large Array images at various frequencies to investigate the properties of the close environment of the source. We characterize the faint galaxies that form the poor group associated with the target. No radio emission is present for these galaxies, while an old radio jet at ~20 kpc from the nucleus of PKS 2155-304 and a jet-like structure of ~2 kpc (~1") in the eastern direction are revealed. No counterparts of these radio jets are found in the NIR or in archival Chandra observations.
The XGS instrument on-board THESEUS Fuschino, F.; Campana, R.; Labanti, C. ...
Journal of physics. Conference series,
10/2016, Volume:
763, Issue:
1
Journal Article
Peer reviewed
Open access
Consolidated techniques used for space-borne X-ray and gamma-ray instruments are based on the use of scintillators coupled to Silicon photo-detectors. This technology associated with modern very low ...noise read-out electronics allows the design of innovative architectures able to reduce drastically the system complexity and power consumption, also with a moderate-to-high number of channels. These detector architectures can be exploited in the design of space instrumentation for gamma-spectroscopy with the benefit of possible smart background rejection strategies. We describe a detector prototype with 3D imaging capabilities to be employed in future gamma-ray and particle space missions in the 0.002-100 MeV energy range. The instrument is based on a stack of scintillating bars read out by Silicon Drift Detectors (SDDs) at both ends. The spatial segmentation and the crystal double-side readout allow a 3D position reconstruction with ∼3 mm accuracy within the full active volume, using a 2D readout along the two external faces of the detector. Furthermore, one of the side of SDDs can be used simultaneously to detect X-rays in the 2-30 keV energy range. The characteristics of this instrument make it suitable in next generation gamma-ray and particle space missions for Earth or outer space observations, and it will be briefly illustrated.
PDF
