16046540
Observational tests of the evolution of spheroidal galaxies and predictions for SIRTF/Spitzer cosmological surveys
Granato et al(2004) have elaborated a physically grounded model exploiting the mutual feedback between star-forming spheroidal galaxies and the active nuclei growing in their cores to overcome, within the hierarchical clustering scenario for galaxy formation, one of the main challenges facing such scenario, the fact that massive spheroidal galaxies appear to have formed earlier and faster than predicted by previous models. Adopting the choice by Granato et al for the parameters governing the history of the SF,of chemical abundances and of the gas and dust content of galaxies, we are left with only two parameters affecting the time and mass dependent SED of spheroidal galaxies. After complementing the model with a simple description of evolutionary properties of starburst, normal late-type galaxies and AGNs we have successfully compared the model with a broad variety of observational data, deep K-band, ISO, IRAS, SCUBA, radio counts, the corresponding redshift distributions, the IR background spectrum, and also with data for EROs. We also present detailed predictions for the GOODS and SWIRE surveys with the Spitzer Space Telescope. We find that the GOODS deep survey at 24$\mu$m and the SWIRE surveys at 70 and 160$\mu$m are likely to be severely confusion limited. The GOODS surveys in the IRAC channels are expected to resolve most of the background, to explore the full passive evolution phase of spheroidal galaxies and most of their active star-forming phase, detecting galaxies up to z\simeq 4. A substantial number of high z star-forming spheroidal galaxies should also be detected by the 24\mum SWIRE and GOODS surveys, while the 70 and 160\mum will be particularly useful to study the evolution of such galaxies in the range 1 \lsim z \lsim 2.[abridged]
1119742
Old massive ellipticals and S0 in the Hubble deep field vanish from view at z > 1.3: Possible solutions of the enigma
We have investigated the properties of a bright K-band selected sample of early-type galaxies in the Hubble Deep Field, as representative of the field galaxy population. This dataset, based on public archives from HST and from deep observations at Hawaii and Kitt-Peak, is unique as for the morphological information on faint high-z sources, and for complete photometric and spectroscopic coverage. The majority of bright early-type galaxies in this field are found at redshifts z ≤ 1.3 to share common properties with those of high-z cluster samples, as for the age and mass of the dominant stellar population – which are found to be as old as 3-5 Gyr and as massive as 10 M⊙ already at z ≃ 1. The bright end of the E/S0 population is already in place by that cosmic epoch, with space densities, masses and luminosities consistent with those of the local field population. There is no evidence of a steepening of the mass function from z=0 to z=1, as inferred by some authors from analyses of optically-selected samples and favoured by hierarchical clustering models forming most of the E/S0s at z 1.3, which would be expected as clearly detectable above the flux limits, given the aged properties of the lower redshift counterparts. So, something hide them at high redshifts. Merging could be an explanation, but it would require that already formed and old stellar systems would assemble on short timescales of Dipartimento di Astronomia, Vicolo Osservatorio 5, I-35122, Padova, Italy. E-mail: Franceschini@astrpd.pd.astro.it International School for Advanced Studies, Via Beirut, I34014 Trieste, Italy Osservatorio Astronomico, Vicolo dell’Osservatorio 5, I35122 Padova, Italy.
19031056
Panchromatic models of galaxies: GRASIL
We present here a model for simulating the panchromatic spectral energy distribution of galaxies, which aims to be a complete tool to study the complex multi‐wavelength picture of the universe. The model take into account all important components that concur to the SED of galaxies at wavelengths from X‐rays to the radio. We review the modeling of each component and provide several applications, interpreting observations of galaxy of different types at all the wavelengths.
116437401
COMPASS RESULTS ON GLUON POLARISATION FROM HIGH PT HADRON PAIRS
AbstractOne of the goals of the COMPASS experiment is the determination of the gluonpolarisation ∆G/G, for a deep understanding of the spin structure of the nucleon.In DIS the gluon polarisation can be measured via the Photon-Gluon-Fusion (PGF)process, identiﬁed by open charm production or by selecting high p T hadron pairsin the ﬁnal state. The data used for this work were collected by the COMPASSexperiment during the years 2002-2004, using a 160 GeV naturally polarised positivemuon beam scattering on a polarised nucleon target. A new preliminary result of thegluon polarisation ∆G/G from high p T hadron pairs in events with Q 2 > 1 (GeV/c) 2 is presented. In order to extract ∆G/G, this analysis takes into account the leadingprocess γq contribution together with the PGF and QCD Compton processes. Anew weighted method based on a neural network approach is used. A preliminary∆G/G result for events from quasi-real photoproduction (Q 2 < 1 (GeV/c) 2 ) is alsopresented. 1 Introduction
121546704
Experimental Program of the Future COMPASS-II Experiment at CERN
Over the last decade the COMPASS experiment has successfully obtained precise results on nucleon structure and hadron spectroscopy, with statistical errors much lower than previously reported. Recently, the new COMPASS-II program, focused on the study of a more complete nucleon description, was approved by CERN. The goal of the program is to access the nucleon structure beyond the collinear approxi-mation, including the quark intrinsic transverse momentum distributions, which are described by the Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs) and by Generalised Parton Distributions (GPDs). The COMPASS collaboration proposes to measure the TMD PDFs, for the first time, via the polarised Drell-Yan process. The results will be complementary to those already obtained in polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS). The GPDs can be accessed using deeply virtual Compton scattering and hard exclusive meson production using an unpolarised hydrogen target in a kinematic region not yet covered by any existing experiment. Also unpolarised SIDIS will be studied, by improving the knowledge of the strange quark PDF and obtaining the kaon fragmentation functions. Another topic covered in this COMPASS-II program is the measurement of the pion and kaon polarisabilities using the Primakoff reaction, which corresponds to a test of the chiral perturbative theory.
125350297
COMPASS results on gluon polarisation