UV--NIR Restframe Luminosity Functions of the Galaxy Cluster EIS0048 at z~0.64

We derive the galaxy luminosity functions in V, R, I, and K bands of the cluster EIS 0048 at z~0.64 from data taken at the ESO Very Large Telescope. The data span the restframe wavelength range from UV, which is sensitive to even low rates of star formation, to the NIR, which maps the bulk of the stellar mass. By comparing our data and previous results with pure luminosity evolution models, we conclude that bright (M<= M^*+1) cluster galaxies are already assembled at z~1 and that star formation is almost completed at z~1.5.Comment: 11 pages, 5 figures. A&A accepte

Optical (VRI) Photometry in the Field of the Galaxy Cluster AC 118 at z=0.31

We present new photometric V-, R- and I-band data for the rich galaxy cluster AC 118 at z=0.31. The new photometry covers an area of 8.6x8.6 arcmin$^2$, corresponding to 2.9$\times$2.9 Mpc$^2$ (H$_0=50$ km s$^{-1}$ Mpc$^{-1}$, q$_0=0.5$ and $\Lambda = 0$). The data have been collected for a project aimed at studying galaxy evolution through the color-magnitude relation and the fundamental plane. We provide a catalogue including all the sources (N = 1206) detected in the cluster field. The galaxy sample is complete to V=22.8 mag (N_gal=574), R=22.3 mag (N_gal=649) and I=20.8 mag (N_gal=419). We give aperture magnitudes within a fixed aperture of 4.4 arcsec and Kron magnitudes. We also give photometric redshifts for 459 sources for which additional U- and K-band photometry is available. We derive and discuss the V- and R-band luminosity functions. The catalogue, which is distributed in electronic form, is intended as a tool for studies in galaxy evolution.Comment: 15 pages, 6 figures, A&A in pres

Evolution of UV -- NIR Structural Properties of Cluster Galaxies

Structural parameters (half light radius r_e, mean surface brightness _e and Sersic index n) are derived for the galaxy cluster A 209, at z = 0.21, in UV and optical restframe, and for the cluster EIS 0048, at z = 0.64, in UV, optical and NIR restframe. This data set, together with previous optical and NIR measurements for the cluster AC 118 at z=0.31}, constitutes the first large sample (N~250) of cluster galaxies whose UV - NIR structure can be investigated up to a look-back time of ~6 Gyr (Omega_m=0.3, Omega_L=0.7 and H_0=70 Km/s/Mpc). The analysis is performed (1) by direct comparison of log r_e, and log n, in UV-OPT and OPT-NIR, and (2) by using the structural parameters to estimate UV-OPT and OPT-NIR internal colour gradients of galaxies. We classify the galaxies as spheroids or disks according to the shape of the optical light profile of galaxies, and investigate separately the evolution in the properties of both populations. On the average, we find that the bulk of spheroids and disks are more concentrated at longer wavelengths, having Delta(log r_e) > 0, and Delta(log n) < 0. The mean value of Delta(log n) in OPT-NIR seems to be the quantity more dependent on z, in the sense that it decreases at higher redshift. In particular, we find a strong decrease in the ratio of OPT to NIR Sersic indices for the disks at z~0.64. By comparing the estimated colour gradients (grad(UV-OPT) and grad(OPT-NIR)) with age and metallicity models, we find that, for the spheroids, both grad(UV-OPT) and grad(OPT-NIR) are weakly dependent on the redshift, confirming that metallicity is the primary effect to drive the gradients. For the disks, metallicity is not able at all to describe the observed range of colour gradients. Age or age+metallicity are responsible for the radial colour distribution of disk dominated galaxies

(Ti,Sn) solid solution-based gas sensors for new monitoring of hydraulic oil degradation

The proper operation of a fluid power system in terms of efficiency and reliability is directly related to the fluid state; therefore, the monitoring of fluid ageing in real time is fundamental to prevent machine failures. For this aim, an innovative methodology based on fluid vapor analysis through metal oxide (shortened: MOX) gas sensors has been developed. Two apparatuses were designed and realized: (i) a dedicated test bench to fast-age the fluid under controlled conditions; (ii) a laboratory MOX sensor system to test the headspace of the aged fluid samples. To prepare the set of MOX gas sensors suitable to detect the analytes’ concentrations in the fluid headspace, different functional materials were synthesized in the form of nanopowders, characterizing them by electron microscopy and X-ray diffraction. The powders were deposited through screen-printing technology, realizing thick-film gas sensors on which dynamical responses in the presence of the fluid headspace were obtained. It resulted that gas sensors based on solid solution TixSn1–xO2 with x = 0.9 and 0.5 offered the best responses toward the fluid headspace with lower response and recovery times. Furthermore, a decrease in the responses (for all sensors) with fluid ageing was observed

CHANTI: a Fast and Efficient Charged Particle Veto Detector for the NA62 Experiment at CERN

The design, construction and test of a charged particle detector made of scintillation counters read by Silicon Photomultipliers (SiPM) is described. The detector, which operates in vacuum and is used as a veto counter in the NA62 experiment at CERN, has a single channel time resolution of 1.14 ns, a spatial resolution of ~2.5 mm and an efficiency very close to 1 for penetrating charged particles

Age, Metallicity and Star Formation History of Cluster Galaxies at z~0.3 F

We investigate the color-magnitude distribution in the rich cluster AC 118 at z=0.31. The sample is selected by the photometric redshift technique, allowing to study a wide range of properties of stellar populations, and is complete in the K-band, allowing to study these properties up to a given galaxy mass. We use galaxy templates based on population synthesis models to translate the physical properties of the stellar populations - formation epoch, time-scale of star formation, and metallicity - into observed magnitudes and colors. In this way we show that a sharp luminosity-metallicity relation is inferred without any assumption on the galaxy formation scenario (either monolithic or hierarchical). Our data exclude significant differences in star formation histories along the color-magnitude relation, and therefore confirm a pure metallicity interpretation for its origin, with an early (z~5) formation epoch for the bulk of stellar populations. The dispersion in the color-magnitude diagram implies that fainter galaxies in our sample (K~18) ceased to form stars as late as z~0.5, in agreement with the picture that these galaxies were recently accreted into the cluster environment. The trend with redshift of the total stellar mass shows that half of the luminous mass in AC 118 was already formed at $z~2, but also that 20% of the stars formed at z<1.Comment: 16 pages, 10 figures. ApJ in pres

Dark Matter in the Universe: Evidence, Candidates and Searches

Contribution from the students of the 4th CERNCLAF School of High-Energy Physics who participated in the Discussion Session addressing the issues of dark matter in the Universe