Are z>2 Herschel galaxies proto-spheroids?

We present a backward approach for the interpretation of the evolution of the near-infrared and the far-infrared luminosity functions across the redshift range 0<z<3. In our method, late-type galaxies are treated by means of a parametric phenomenological method based on PEP/HerMES data up to z~4, whereas spheroids are described by means of a physically motivated backward model. The spectral evolution of spheroids is modelled by means of a single-mass model, associated to a present-day elliptical with K-band luminosity comparable to the break of the local early-type luminosity function. The formation of proto-spheroids is assumed to occurr across the redshift range 1< z < 5. The key parameter is represented by the redshift z_0.5 at which half proto-spheroids are already formed. A statistical study indicates for this parameter values between z_0.5=1.5 and z_0.5=3. We assume as fiducial value z_0.5~2, and show that this assumption allows us to describe accourately the redshift distributions and the source counts. By assuming z_0.5 ~ 2 at the far-IR flux limit of the PEP-COSMOS survey, the PEP-selected sources observed at z>2 can be explained as progenitors of local spheroids caught during their formation. We also test the effects of mass downsizing by dividing the spheroids into three populations of different present-day stellar masses. The results obtained in this case confirm the validity of our approach, i.e. that the bulk of proto-spheroids can be modelled by means of a single model which describes the evolution of galaxies at the break of the present-day early type K-band LF.Comment: Accepted for publication in ApJ; 26 pages; 13 figure

A coordinate-dependent superspace deformation from string theory

Starting from a type II superstring model defined on $R^{2,2}\times CY_6$ in a linear graviphoton background, we derive a coordinate dependent $C$-deformed ${\cal N}=1$, $d=2+2$ superspace. The chiral fermionic coordinates $\theta$ satisfy a Clifford algebra, while the other coordinate algebra remains unchanged. We find a linear relation between the graviphoton field strength and the deformation parameter. The null coordinate dependence of the graviphoton background allows to extend the results to all orders in $\alpha'$.Comment: 14 pages, reference added, accepted for publication in JHE

Spin dependent transport in organic light-emitting diodes

Electrically Detected Magnetic Resonance (EDMR) was used to study a series of multilayer organic devices based on aluminum (III) 8-hydroxyquinoline. These devices were designed to identify the micoscopic origin of different spin dependent process, i.e. hopping and exciton formation. EDMR is demonstrated to probe molecular orbitals of charge, and thus indirectly explore interfaces, exciton formation, charge accumalation and electric fields in operating organic based devices

Copper and Barium Abundances in the Ursa Major Moving Group

We present Cu and Ba abundances for 7 G-K dwarf stars, members of the solar-metallicity, 0.3 Gyr old Ursa Major Moving Group. All analyzed member stars show [Ba/Fe] excesses of +0.3-plus, associated with [Cu/Fe] deficiencies of up to -0.23 dex. The present results suggest that there is an anti-correlation between the abundances of Cu and the heavy elements produced by the main component of the neutron capture s-process. Other possible anomalies are Na and C deficiencies with respect to normal solar-metallicity stars. The new data do not confirm the recent claim that the group member HR6094 is a Ba dwarf star.Comment: 8 pages, 6 figures, accepted to MNRA

A photometric and spectroscopic survey of solar twin stars within 50 parsecs of the Sun: I. Atmospheric parameters and color similarity to the Sun

Solar twins and analogs are fundamental in the characterization of the Sun's place in the context of stellar measurements, as they are in understanding how typical the solar properties are in its neighborhood. They are also important for representing sunlight observable in the night sky for diverse photometric and spectroscopic tasks, besides being natural candidates for harboring planetary systems similar to ours and possibly even life-bearing environments. We report a photometric and spectroscopic survey of solar twin stars within 50 pc of the Sun. Hipparcos absolute magnitudes and (B-V)_Tycho colors were used to define a 2 sigma box around the solar values, where 133 stars were considered. Additional stars resembling the solar UBV colors in a broad sense, plus stars present in the lists of Hardorp, were also selected. All objects were ranked by a color-similarity index with respect to the Sun, defined by uvby and BV photometry. Moderately high-resolution, high-S/N spectra were used for a subsample of equatorial-southern stars to derive Teff, log g, and [Fe/H] with average internal errors better than 50 K, 0.20 dex, and 0.08 dex, respectively. Ages and masses were estimated from theoretical HR diagrams. The color-similarity index proved very successful. We identify and rank new excellent solar analogs, which are fit to represent the Sun in the night sky. Some of them are faint enough to be of interest for moderately large telescopes. We also identify two stars with near-UV spectra indistinguishable from the Sun's. We present five new "probable" solar twin stars, besides five new "possible" twins. Masses and ages for the best solar twin candidates lie very close to the solar values, but chromospheric activity levels range somewhat. We propose that the solar twins be emphasized in the ongoing searches for extra-solar planets and SETI searches.Comment: 25 pages, 15 figures, 14 table

A Physical Model for Co-evolution of QSOs and of their Spheroidal Hosts

At variance with most semi-analytic models, in the Anti-hierarchical Baryon Collapse scenario (Granato et al. 2001, 2004) the main driver of the galaxy formation and evolution is not the merging sequence but are baryon processes. This approach emphasizes, still in the framework of the hierarchical clustering paradigm for dark matter halos, feedback processes from supernova explosions and from active nuclei, that tie together star formation in spheroidal galaxies and the growth of black holes at their centers. We review some recent results showing the remarkably successful predictive power of this scenario, which allows us to account for the evolution with cosmic time of a broad variety of properties of galaxies and active nuclei, which proved to be very challenging for competing models.Comment: Invited talk at the Specola Vaticana Workshop on "AGN and Galaxy Evolution", Castel Gandolfo, 3-6 October 2005, 10 pages, 2 figure

From First Galaxies to QSOs: feeding the baby monsters

We present a physical model for the coevolution of massive spheroidal galaxies and active nuclei at their centers. Supernova heating is increasingly effective in slowing down the star formation and in driving gas outflows in smaller and smaller dark matter halos. Thus the more massive protogalaxies virializing at early times are the sites of faster star formation. The correspondingly higher radiation drag causes a faster angular momentum loss by the gas and induces a larger accretion rate onto the central black hole. In turn, the kinetic energy of the outflows powered by the active nuclei can unbind the residual gas in a time shorter for larger halos. The model accounts for a broad variety of dynamical, photometric and metallicity properties of early-type galaxies, for the M_BH -- \sigma relation and for the local supermassive black-hole mass function.Comment: 6 pages, contributed paper to Proceedings of the Conference on "Growing Black Holes" held in Garching, Germany, on June 21-25, 2004, edited by A. Merloni, S. Nayakshin and R. Sunyaev, Springer-Verlag series of "ESO Astrophysics Symposia