The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. ?? 2013 Elsevier B.V. All rights reserved

THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) followup with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift ∼10, signatures of Pop III stars, sources and physics of reionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).

Aims. Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9 • in width, with an inner circular FoV at 1.6 • , thus spanning the solar atmosphere from 1.7 R to about 9 R , owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation. Methods. Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H i Lyman-α line at 121.6 nm. The visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the K corona. The coronal images in both the UV H i Lyman-α and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 second can be achieved when observing coronal fluctuations in visible light. Results. The Metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (CMEs) take place. The near-Sun multi-wavelength coronal imaging performed with Metis, combined with the unique opportunities offered by the Solar Orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the Sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections. Conclusions. This paper presents the scientific objectives and requirements, the overall optical design of the Metis instrument, t...

We present near-infrared imaging of the host galaxies of low-luminosity quasars at 1 < z < 2, aimed at investigating the relationship between the nuclear and host-galaxy luminosities at high redshift. This work complements our previous study to trace the cosmological evolution of the host galaxies of high-luminosity quasars. The sample consists of nine radio-loud (RLQ) and six radio-quiet (RQQ) low-luminosity quasars. They have similar redshift and optical luminosity distributions, and together with the high-luminosity quasars, cover a large range of the quasar luminosity function. For all but two of the quasars, we have been able to derive the global properties of the surrounding nebulosity. The host galaxies of both types of quasars are massive inactive ellipticals between L Ã and 10L Ã , with RLQ hosts being significantly more luminous than RQQ hosts. This luminosity gap is independent of the rest-frame U-band luminosity but correlated with the rest-frame R-band luminosity. The color difference between the RQQs and the RLQs is likely a combination of an intrinsic difference in the strength of the thermal and nonthermal components in their SEDs, and a selection effect due to internal dust extinction. For the combined set of quasars, we find a reasonable correlation between the nuclear and the host luminosities. This correlation is less apparent for RQQs than for RLQs. If the R-band luminosity represents the bolometric luminosity, and the host luminosity is proportional to the black hole mass, as in nearby massive spheroids, quasars emit in a relatively narrow range with respect to their Eddington luminosity and with the same distribution for RLQs and RQQs.

All-organic nanostructured host-guest systems, based on dyes inserted in the nanochannels of perhydrotriphenylene (PHTP) and deoxycholic acid (DCA), show enhanced fluorescence properties with quantum yields even higher than those of the dyes in solution, thanks to the high concentration of emissive molecules with controlled spatial and geometrical organization that prevents aggregation quenching. Both host molecules crystallize, growing with the long axis oriented along the direction of the nanochannels where the linear-chain dyes are inserted, to yield crystals emitting well-polarized light. For the DCA-based host-guests, homogeneous thin films suitable for several applications are obtained. Colour emission in such films can be tuned by co-inclusion of two or three dyes due to resonant energy-transfer processes. We show that films obtained by low-cost techniques, such as solution casting and spin-coating, convert UV light into visible light with an efficiency much higher than that of the standard polymeric blends.

We present the analysis of the photometric and spectroscopic properties of a sample of 29 low redshift (z < 0.6) QSOs for which both HST WFPC2 optical images and ultraviolet HST FOS spectra are available. For each object we measure the R band absolute magnitude of the host galaxy, the C IV (1550 Å) line width and the 1350 Å continuum luminosity. From these quantities we can estimate the black hole (BH) mass through the M BH − L bulge relation for inactive galaxies, and from the virial method based on the kinematics of the regions emitting the broad lines. The comparison of the masses derived from the two methods yields information on the geometry of the gas emitting regions bound to the massive BH.

-2 -We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of 16 low luminosity radio-quiet quasars at the epoch around the peak of the quasar activity (2 < z < 3), aimed at investigating their host galaxies. For 11 quasars, we are able to detect the host galaxies and derive their properties, while for the other five quasars, upper limits to the host luminosity are estimated. The luminosities of the host galaxies of radio-quiet quasars at high redshift are in the range of those of massive inactive elliptical galaxies.This work complements our previous systematic study of quasar hosts aimed to trace the cosmological luminosity evolution of the host galaxies up to z ∼ 2 and extends our pilot study of a few luminous quasars at z > 2. The luminosity trend with cosmic epoch resembles that observed for massive inactive galaxies, suggesting a similar star formation history. In particular, both quasar host galaxies and massive inactive galaxies appear mostly assembled already at the peak age of the quasar activity. This result is of key importance for testing the models of joint formation and evolution of galaxies and their active nuclei.

The properties of high redshift quasar host galaxies are studied, in order to investigate the connection between galaxy evolution, nuclear activity, and the formation of supermassive black holes. We combine new near-IR observations of three high redshift quasars ( 2 < z < 3), obtained at the ESO-Very Large Telescope equipped with adaptive optics, with selected data from the literature.