VizieR Online Data Catalog: Radial velocities of galaxies in A523 field (Girardi+, 2016)

Multi-object spectroscopic observations of A523 were carried out at the TNG in 2012 December and 2014 January. We used the instrument DOLORES in MOS mode with the LR-B Grism. In summary, we observed six MOS masks for a total of 210 slits. The total exposure time was 3600s for three masks, 5400s for two masks and 7200s for the last one. Our photometric observations were carried out with the Wide Field Camera (WFC), mounted at the prime focus of the 2.5-m INT telescope. We observed A523 in g, r and i Sloan-Gunn filters in photometric conditions and a seeing of ~1.4arcsec. (1 data file)

Puzzling large-scale polarization in the galaxy cluster Abell 523

Large-scale magnetic fields reveal themselves through diffuse synchrotron sources observed in galaxy clusters such as radio halos. Total intensity filaments of these sources have been observed in polarization as well, but only in three radio halos out of about one hundred currently known. In this paper we analyze new polarimetric Very Large Array data of the diffuse emission in the galaxy cluster Abell 523 in the frequency range 1-2 GHz. We find for the first time evidence of polarized emission on scales of ~ 2.5 Mpc. Total intensity emission is observed only in the central part of the source, likely due to observational limitations. To look for total intensity emission beyond the central region, we combine these data with single-dish observations from the Sardinia Radio Telescope and we compare them with multi-frequency total intensity observations obtained with different instruments, including the LOw Frequency ARray and the Murchison Widefield Array. By analysing the rotation measure properties of the system and utilizing numerical simulations, we infer that this polarized emission is associated with filaments of the radio halo located in the outskirts of the system, in the peripheral region closest to the observer.Comment: 14 pages, 12 figures, accepted for publication on MNRA

Spectro-polarimetric observations of the CIZA J2242.8+5301 northern radio relic: no evidence of high-frequency steepening

Observations of radio relics at very high frequency (>10 GHz) can help to understand how particles age and are (re-)accelerated in galaxy cluster outskirts and how magnetic fields are amplified in these environments. In this work, we present new single-dish 18.6 GHz Sardinia Radio Telescope and 14.25 GHz Effelsberg observations of the well known northern radio relic of CIZA J2242.8+5301. We detected the relic which shows a length of $\sim$1.8 Mpc and a flux density equal to $\rm S_{14.25\,GHz}=(9.5\pm3.9)\,mJy$ and $\rm S_{18.6\,GHz}=(7.67\pm0.90)\,mJy$ at 14.25 GHz and 18.6 GHz respectively. The resulting best-fit model of the relic spectrum from 145 MHz to 18.6 GHz is a power-law spectrum with spectral index $\alpha=1.12\pm0.03$: no evidence of steepening has been found in the new data presented in this work. For the first time, polarisation properties have been derived at 18.6 GHz, revealing an averaged polarisation fraction of $\sim40\%$ and a magnetic field aligned with the 'filaments' or 'sheets' of the relic.Comment: 10 pages, 8 figure

Spectral study of the diffuse synchrotron source in the galaxy cluster Abell 523

The galaxy cluster Abell 523 (A523) hosts an extended diffuse synchrotron source historically classified as a radio halo. Its radio power at 1.4 GHz makes it one of the most significant outliers in the scaling relations between observables derived from multiwavelength observations of galaxy clusters: it has a morphology that is different and offset from the thermal gas, and it has polarized emission at 1.4 GHz typically difficult to observe for this class of sources. A magnetic field fluctuating on large spatial scales (similar to 1 Mpc) can explain these peculiarities but the formation mechanism for this source is not yet completely clear. To investigate its formation mechanism, we present new observations obtained with the LOw Frequency ARray at 120-168 MHz and the Jansky Very Large Array at 1-2 GHz, which allow us to study the spectral index distribution of this source. According to our data the source is observed to be more extended at 144 MHz than previously inferred at 1.4 GHz, with a total size of about 1.8 Mpc and a flux density S-144 MHz = (1.52 +/- 0.31) Jy. The spectral index distribution of the source is patchy with an average spectral index alpha similar to 1.2 between 144 MHz and 1.410 GHz, while an integrated spectral index alpha similar to 2.1 has been obtained between 1.410 and 1.782 GHz. A previously unseen patch of steep spectrum emission is clearly detected at 144 MHz in the south of the cluster. Overall, our findings suggest that we are observing an overlapping of different structures, powered by the turbulence associated with the primary and a possible secondary merger.Peer reviewe

N. 6 Schede di catalogo: n. 7.6 Vescovo Lazzaro, Breviario Armeno; n. 7.7 Copista e miniatore ignoti, Evangeliario armeno; n. 7.8 Officina mesopotamica, Mattoni di fondazione con iscrizione cuneiforme; n. 7.18 Ambito veneziano (?), Lavanda dei piedi; n. 7.19 Ambito Italia centrale (?), San Carlo Borromeo e San Filippo Neri; n. 8.6 Attilio Spaccarelli, Coppa con scene dionisiache

La mostra presenta al pubblico – per la prima volta in modo organico – la raccolta vasta e sorprendente che i coniugi statunitensi George Washington Wurts ed Henriette Tower misero insieme a cavallo fra XIX e XX secolo e donarono poi allo Stato italiano, per l’esattezza al museo di Palazzo Venezia, dove tuttora è conservata. Alla base della mostra vi è comunque anche l’idea di restituire il contesto della raccolta Wurts, ovvero quella particolare forma di collezionismo che tra Ottocento e Novecento si legò così intimamente all’Italia, fino a concretizzarsi spesso nella donazione allo Stato di singole opere o di intere raccolte. La mostra illustra le dinamiche del collezionismo, soprattutto anglo-americano, e del mercato internazionale, sullo sfondo dei radicali cambiamenti vissuti in quegli anni dalla giovane nazione italiana e dalla sua nuova capitale, Roma. La costruzione del Vittoriano, iniziato nel 1885 e inaugurato nel 1911 nell’occasione dell’Esposizione che celebrava il cinquantenario dell’Unità d’Italia, diviene l’emblema che caratterizza la città all’alba del Novecento