I. Porceddu

Theoretical electron affinities of PAHs and electronic absorption spectra of their mono-anions

We present theoretical electron affinities, calculated as total energy differences, for a large sample of polycyclic aromatic hydrocarbons (PAHs), ranging in size from azulene (C10H8) to dicoronylene (C48H20). For 20 out of 22 molecules under study we obtained electron affinity values in the range 0.4-2.0 eV, showing them to be able to accept an additional electron in their LUMO π � orbital. For the mono-anions we computed the absolute photo-absorption cross-sections up to the vacuum ultraviolet (VUV) using an implementation in real time and real space of the Time-Dependent Density Functional Theory (TD-DFT), an approach which has already been proven to yield accurate results for neutral and cationic PAHs. Comparison with available experimental data hints that this is the case for mono-anions as well. We find that PAH anions, like their parent molecules and the corresponding cations, display strong π ∗ ← π electronic transitions in the UV. The present results provide a quantitative foundation to estimate the fraction of specific PAHs which can be singly negatively charged in various interstellar environments, to simulate their photophysics in detail and to evaluate their contribution to the interstellar extinction curve.

Sardinia Radio Telescope: the new Italian project

This contribution gives a description of the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna proposed by the Institute of Radio Astronomy (IRA) of the National Institute for Astrophysics. The radio telescope is under construction near Cagliari (Sardinia) and it will join the two existing antennas of Medicina (Bologna) and Noto (Siracusa) both operated by the IRA. With its large antenna size (64m diameter) and its active surface, SRT, capable of operations up to about 100GHz, will contribute significantly to VLBI networks and will represent a powerful single-dish radio telescope for many science fields. The radio telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and the standing wave between secondary mirror and feed. After the start of the contract for the radio telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the radio telescope inauguration in late 2006.

Status of the Sardinia Radio Telescope project

We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radiotelescope capable to operate with high efficiency in the 0.3-116 GHz frequency range. The instrument is the result of a scientific and technical collaboration among three Structures of the Italian National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomy Observatory (in Sardinia,) and the Arcetri Astrophysical Observatory in Florence. Funding agencies are the Italian Ministry of Education and Scientific Research, the Sardinia Regional Government, and the Italian Space Agency (ASI,) that has recently rejoined the project. The telescope site is about 35 km North of Cagliari. The radio telescope has a shaped Gregorian optical configuration with a 7.9 m diameter secondary mirror and supplementary Beam-WaveGuide (BWG) mirrors. With four possible focal positions (primary, Gregorian, and two BWGs), SRT will be able to allocate up to 20 remotely controllable receivers. One of the most advanced technical features of the SRT is the active surface: the primary mirror will be composed by 1008 panels supported by electromechanical actuators digitally controlled to compensate for gravitational deformations. With the completion of the foundation on spring 2006 the SRT project entered its final construction phase. This paper reports on the latest advances on the SRT project.

Sardinia Array Demonstrator: Instrument overview and status

In the framework of the Square Kilometer Array (SKA) project, the Italian Institute for Astrophysics (INAF) has addressed several efforts in the design and prototyping of aperture arrays for low-frequency radio astronomical research. The Sardinia Array Demonstrator (SAD) is a national project aimed to develop know-how in this area and to test different architectural technologies and calibration algorithms. SAD consists of 128 prototypical dual-polarized Vivaldi antennas designed to operate at radio frequencies below 650 MHz. The antennas will be deployed at the Sardinia Radio Telescopes site with a versatile approach able to provide two different array configurations: (i) all antennas grouped in one large station or (ii) spread among a core plus few satellite stations. This paper provides an overview of the SAD project from an instrumental point of view, and illustrates its status after 2 years from its start.

Sardinia aperture array demonstrator

We present a project aimed at realizing an Italian aperture array demonstrator constituted by prototypical Vivaldi antennas designed to operate at radio frequencies below 500 MHz. We focus on an array composed of a core plus a few satellite phased-array stations to be installed at the Sardinia Radio Telescope (SRT) site. The antenna elements are mobile and thus it will be possible to investigate the performance in terms of both uv-coverage and synthesized resolution resulting from different configurations of the array.

Automatic data reduction in support of the FLAMES-UVES VLT facility

With the deployment of the new FLAMES facility at the Kueyen Unit Telescope of the VLT, multi object, fibre fed capability will be added to the UVES spectrograph. The FLAMES-UVES Data Reduction Software is a C Library embedded in the MIDAS environment. It is designed to extend the UVES pipeline functionalities to support the operation and to monitor the night and long term performance of FLAMES-UVES at Kueyen telescope of the VLT. The peculiar spectral format of FLAMES-UVES imposes very stringent constraints on instrument stability, and poses some major challenges. Some of them are common to any multi fibre fed echelle spectrograph, such as automatic order and fibre location and identification, deblending of spectra carried by neighboring fibres, flagging and removal of cosmic ray hits etc.; others are typical of FLAMES/UVES, such as the automatic measurement and correction of some spectrograph instabilities which, although irrelevant for slit mode operation, would severely cripple the maximum achievable S/N ratio in the fibre-fed case, if neglected. Throughout the reduction, errors are thoroughly propagated from raw frames to the final data products, pixel by pixel, easing the assessment of the actual, physical significance of weak features. We shortly discuss the performance of the pipeline and to what extent the DRS can be expected to recover the full information content without introducing artifacts, showing its results on test data.

Dust pollution monitoring at the TNG telescope

The Italian Galileo telescope (TNG) is part of the Roque de Los Muchachos astronomical complex, also referred as ENO, European Northern Observatory. Astronomical sites must be carefully selected in order to maximize the scientific return from the fairly large investment they require, both in terms of money as well as of human resources. This also means to maximize (and/or optimize) the amount of time available for observations, so that the requirements of the telescope to have good performance in both optical and NIR wavelengths strongly depends on meteorological conditions (e.g. differential air temperature between inside and outside telescope dome, presence of atmospheric dust, etc.). TNG site is monitored on a continuous basis by an automatic weather station, which provides on line measurements of a few local meteorological parameters, e.g. temperature and relative humidity. Since a few month we added a multichannel dust monitor to the set of meteorological sensors. This four channel facility provides the size distribution of atmospheric dust particles, being able to detect and discriminate among four different particles sizes: 0.3, 0.5, 1 and 5 micron. This contribution will present the first preliminary data which have collected at the Roque site close to the TNG dome, in order to analyze the (possible) relationship between dust data and meteorological parameters trend.

Three years of dust monitoring at the Galileo telescope

Since summer 2001, dust pollution of the air is regularly measured through a particle counter at the Telescopio Nazionale Galileo (TNG) located at the Roque de los Muchachos Observatory (La Palma - Canary Islands). Canary Islands are normally interested by a dominant atmospheric circulation with NE winds. Depending on their strenght, and their exact direction, winds may bring with themselves small to large amount of dust from the Sahara desert, with important consequences on the transparency of the sky. Meteorological satellites gave us some impressive examples of such these phenomenon. We show here the results of trying a correlation between dust-pollution data and the nightly atmospheric extinction measured at other telescopes. While the transparency is mostly affecting the astronomical work, other effects like changes of air temperature and humidity are clearly visible; for this reason dust-pollution data are also compared with the weather data recorded at the TNG meteo tower.

Commissioning of the Sardinia Radio Telescope in Italy: Results and perspectives

On 30 September 2013, the opening ceremony of SRT has signed the contractual ending of the instrumental commissioning of the Sardinia Radio Telescope. In February 2014 it has been completed also the “fine tuning process” aimed at defining the first optimizations parameters needed to make calibrated radio astronomical observations. Since then, the final Astronomical Validation, that was just started in parallel with the previous activities, has taken the lead of the users allocated time. At the time of the real presentation in August we expect to be able to present the experimental quantitative results of the commissioning that at the time of this writing are still under analysis.

Identifying specific interstellar polycyclic aromatic hydrocarbons

Interstellar Polycyclic Aromatic Hydrocarbons (PAHs) have been thought to be ubiquitous for more than twenty years, yet no single species in this class has been identified in the Interstellar Medium (ISM) to date. The unprecedented sensitivity and resolution of present Infrared Space Observatory (ISO) and forthcoming Herschel observations in the far infrared spectral range will offer a unique way out of this embarassing impasse.