The star formation history of redshift z ~ 2 galaxies： the role of the infrared prior

We build a sample of 298 spectroscopically-confirmed galaxies at redshift z - 2, selected in the z850-band from the GOODS-MUSIC catalog. By utilizing the rest frame 8 p.m luminosity as a proxy of the star formation rate （SFR）, we check the accuracy of the standard SED-fitting technique, finding it is not accurate enough to provide reliable estimates of the physical parameters of galaxies. We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable Rv. Then we exploit the new method to re-analyze our galaxy sample, and to robustly determine SFRs, stellar masses and ages. We find that there is a general trend of increasing attenuation with the SFR. Moreover, we find that the SFRs range between a few to 103 M~ yr-1, the masses from 109 to 4 ~ 1011 Mo, and the ages from a few tens of Myr to more than 1 Gyr. We discuss how individual age measurements of highly attenuated objects indicate that dust must have formed within a few tens of Myr and already been copious at 〈 100 Myr. In addition, we find that low luminosity galaxies harbor, on average, significantly older stellar populations and are also less massive than brighter ones; we discuss how these findings and the well known ＇downsizing＇ scenario are consistent in a framework where less massive galaxies form first, but their star formation lasts longer. Finally, we find that the near-IR attenuation is not scarce for luminous objects, contrary to what is customarily assumed; we discuss how this affects the interpretation of the observed M,/L ratios.     

First alkaline magmatism during Iberia–Newfoundland rifting

The age and origin of alkaline rocks emplaced into the sediments of the rift‐related continental Lusitanian basin were investigated to constrain earliest magmatic activity occurring prior to oceanic plate formation between Iberia and Newfoundland. The U–Pb titanite ages are 146.5 ± 1.6 (2σSTERR), 145.3 ± 1.4 and 142.3 ± 1.0 Ma, and initial Pb isotopic ratios of feldspars lie at 18.418–18.978 for ²⁰⁶Pb/²⁰⁴Pb, at 15.594–15.925 for ²⁰⁷Pb/²⁰⁴Pb and at 37.105–39.216 for ²⁰⁸Pb/²⁰⁴Pb. Initial ⁸⁷Sr/⁸⁶Sr ratios measured in the same feldspar fractions lie at 0.705409–0.706462. This episode of magmatic activity lasting for at least 4.2 ± 2.6 Myr most likely marks a phase of maximum lithospheric thinning during which zones of weakness were created to allow deep magmas to reach the surface. Such zones are preferentially re‐activated Palaeozoic faults of the Iberian plate. The isotope data suggest that the dominant volume of alkaline magmas was generated by partial melting of the metasomatized subcontinental Iberian mantle.     

The Campo Imperatore Near Earth Object Survey (CINEOS)

The Campo Imperatore Near Earth Object Survey (CINEOS) is an Italian survey dedicated to the search and follow-up of Near Earth Objects (NEOs). It is operated with the 90 cm f/3 Schmidt telescope at the Campo Imperatore of the Rome Astronomical Observatory (INAF-OAR) as a joint project with the Istituto di Astrofisica Spaziale and Fisica Cosmica (INAF-IASF) in Rome. Since the end of 2001 CINEOS has covered about 4,250 sq. deg to 20th magnitude in the course of about 160 nights. This effort led to the discovery of 7 Near Earth Asteroids (NEAs), 1 comet (167P/CINEOS; a member of the Centaur group) and a few other unusual objects including 2004 XH₅₀ with a unique comet-like orbit. CINEOS has also contributed almost 2,200 preliminary designations and over 30,000 detections to the Minor Planet Center. About 20% of the survey effort was carried out at low solar elongations (LSE), although no object with an orbit interior (Inner Earth Objects, IEO class) or nearly interior to the Earth (Aten class) was found. The work at LSE was, however, very important to test survey strategies implemented with larger telescopes. We also provide the results of a CINEOS simulation on a reliable NEO population model based on the results of two larger scale surveys, Spacewatch and LINEAR.     

Pattern of deformation around the central Aeolian Islands: evidence from multichannel seismics and GPS data

The tectonics of the central Aeolian Islands, which are located within the Tyrrhenian backarc basin, has been investigated through a marine seismic reflection survey. We find that compressional structures dominate around the islands, whereas extensional faults occur only to the north of Salina and Filicudi, towards the Marsili basin. This pattern of deformation, although different from previously reported, is in agreement with the strain field and stress regime obtained from GPS measurements and seismological data. Age constraints suggest that contractional deformation was active since middle Pleistocene, being coeval with the building of the volcanic edifices of the Aeolian Islands, and is superimposed on pre‐existing extensional deformation. Compressional and extensional regimes, therefore, can coexist within a backarc setting. Seismic profiles show that the Tindari‐Letojanni fault, considered as a major tectonic element, does not extend to the north towards the island of Vulcano as a throughgoing fault; rather, deformation is accommodated in a broader belt displaying greater structural complexity.     

Jet-Disc Coupling in the Accreting Black Hole Xte J1118+480

We interpret the rapid correlated UV/optical/X-ray variability of XTE J1118+480 as a signature of the coupling between the X-ray corona and a jet emitting synchrotron radiation in the optical band. We propose a scenario in which the jet and the X-ray corona are fed by the same energy reservoir where large amounts of accretion power are stored before being channelled into either the jet or the high energy radiation. This time-dependent model reproduces the main features of the rapid multi-wavelength variability of XTE J1118+480. A strong requirement of the model is that the total jet power should be at least a few times larger than the observed X-ray luminosity, implying a radiative efficiency for the jet ∊_j3 × 10⁻³. This would be consistent with the overall low radiative efficiency of the source. We present independent arguments showing that the jet probably dominates the energetic output of all accreting black holes in the low-hard state. Partially supported by PPARC     

Intergalactic medium metal enrichment through dust sputtering

We study the motion of dust grains into the intergalactic medium (IGM) around redshift   z = 3  , to test the hypothesis that grains can efficiently pollute the gas with metals through sputtering. We use the results available in the literature for radiation-driven dust ejection from galaxies as initial conditions and follow the motion onwards. Via this mechanism, grains are ejected into the IGM with velocities  >100 km s⁻¹  ; as they move supersonically, grains can be efficiently eroded by non-thermal sputtering. However, Coulomb and collisional drag forces effectively reduce the charged grain velocity. Up-to-date sputtering yields for graphite and silicate (olivine) grains have been derived using the code transport of ions in matter ( trim ), for which we provide analytic fits. After training our method on a homogeneous density case, we analyse the grain motion and sputtering in the IGM density field as derived from a Λ cold dark matter (CDM) cosmological simulation at   z = 3.27  . We found that only large  ( a ≳ 0.1μm)  grains can travel up to considerable distances (few  ×100 kpc  physical) before being stopped. Resulting metallicities show a well-defined trend with overdensity δ. The maximum metallicities are reached for  10 < δ < 100  [corresponding to systems, in quasi-stellar object (QSO) absorption spectra, with  14.5 < log N (H  i ) < 16  ]. However the distribution of sputtered metals is very inhomogeneous, with only a small fraction of the IGM volume polluted by dust sputtering (filling factors of 18 per cent for Si and 6 per cent for C). For the adopted size distribution, grains are never completely destroyed; nevertheless, the extinction and gas photoelectric heating effects resulting from this population of intergalactic grains are well below current detection limits.     

Extensional tectonics and volcano lateral collapses: insights from Ollagüe volcano (Chile‐Bolivia) and analogue modelling

Understanding the process of volcanic lateral collapse, which may be governed by numerous possible factors, can be significantly improved by identifying the role of each factor. Here we test the perturbation induced in a volcano by tectonic normal faulting in the basement, magma inflation and multiple flank deformation, based on fieldwork and analogue experiments. Ollagüe Volcano (Chile‐Bolivia) provides a good example of a sector collapse with exposed substrate extensional tectonics, and our experiments have been done with conditions consistent with field data. Results show that none of the possible tectonic conditions led to complete lateral failure; in agreement also with the field data, sector collapse of the model cone occurred only when a shallow magmatic intrusion within the volcano was reproduced. We also found out that volcano flank deformation is enhanced if a previous flank destabilization occurred, interleaved by new cone growth. Terra Nova, 18, 282–289, 2006     

Rolling down from the 30 keV peak: Modelling the Hard X-Ray and γ-Ray Backgrounds

We will briefly discuss the importance of sensitive X-ray observations above a few tens of keV for a better understanding of the physical mechanisms associated to the Supermassive Black Hole primary emission in both radio quiet and radio loud AGN and to the cosmological evolution of the most obscured sources.     

From Astrometry to Celestial Mechanics: Orbit Determination with Very Short Arcs

Contemporary surveys provide a huge number of detections of small solar system bodies, mostly asteroids. Typically, the reported astrometry is not enough to compute an orbit and/or perform an identification with an already discovered object. The classical methods for preliminary orbit determination fail in such cases: a new approach is necessary. When the observations are not enough to compute an orbit we represent the data with an attributable (two angles and their time derivatives). The undetermined variables range and range rate span an admissible region of solar system orbits, which can be sampled by a set of Virtual Asteroids (VAs) selected by an optimal triangulation. The attributable results from a fit and has an uncertainty represented by a covariance matrix, thus the predictions of future observations can be described by a quasi-product structure (admissible region times confidence ellipsoid), which can be approximated by a triangulation with each node surrounded by a confidence ellipsoid. The problem of identifying two independent short arcs of observations has been solved. For each VA in the admissible region of the first arc we consider prediction at the time of the second arc and the corresponding covariance matrix, and we compare them with the attributable of the second arc with its own covariance. By using the penalty (increase in the sum of squares, as in the algorithms for identification) we select the VAs which can fit together both arcs and compute a preliminary orbit. Even two attributables may not be enough to compute an orbit with a convergent differential corrections algorithm. The preliminary orbits are used as first guess for constrained differential corrections, providing solutions along the Line Of Variations (LOV) which can be used as second generation VAs to further predict the observations at the time of a third arc. In general the identification with a third arc will ensure a least squares orbit, with uncertainty described by the covariance matrix.