Spectral Ages of CSOs and CSS Sources

This paper deals with the spectral ageing study of a representative sample of compact symmetric objects (CSOs) and compact steep spectrum (CSS) sources. Observations reveal a distinctive high-frequency steepening of the radio spectra of many of these sources. The existence of such a spectral feature is expected or may be naturally interpreted in terms of radiative ageing of synchrotron emitting electrons. The small angular size of CSS sources makes it relatively easy to measure their integrated spectra over a wide frequency range for a conspicuous number of objects. For those sources whose emission is dominated by the mini-lobes, the integrated spectra can be used to constrain the source age. Assuming equipartition magnetic fields, the spectral ages we found are in the range from 10^2 to 10^5 yr. Multifrequency VLBA observations allow us to study the spectral properties of two CSOs: B1323+321 and B1943+546. The case of B1943+546 is particularly interesting since for this source a kinematic age has been derived from the proper motion of the hot spots. We found that spectral and kinematic ages agree within a factor of 2. The overall results presented here confirm that the CSOs and CSS sources are indeed young objects. Finally, we show some examples of compact sources characterised by an extraordinary steep and curved spectrum. It is plausible that these are relic sources in which the injection of fresh electrons has ceased for a significant fraction of their lifetime. These observations may indicate either the presence of intermittent activity or a class of short-living objects.Comment: 11 pages, 5 figures, Refereed and accepted by Publications of the Astronomical Society of Australia, as part of the proceedings of the 3rd GPS/CSS workshop, eds. T. Tzioumis, W. de Vries, I. Snellen, A. Koekemoe

Novel constraints on noncold, nonthermal dark matter from Lyman-alpha forest data

In this paper, we present an efficient method for constraining both thermal and nonthermal dark matter (DM) scenarios with the Lyman-\u3b1 forest based on a simple and flexible parametrization capable of reproducing the small-scale clustering signal of a large set of noncold DM (NCDM) models. We extract new limits on the fundamental DM properties through an extensive analysis of the high resolution, high redshift data obtained by the MIKE/HIRES spectrographs. By using a large suite of hydrodynamical simulations, we determine constraints on both astrophysical, cosmological, and NCDM parameters by performing a full Monte Carlo Markov chain analysis. We obtain a marginalized upper limit on the largest possible scale at which a power suppression induced by nearly any NCDM scenario can occur, i.e., \u3b1<0.03 Mpc/h (2\u3c3 C.L.). We explicitly describe how to test several of the most viable NCDM scenarios without the need to run any specific numerical simulations due to the novel parametrization proposed and due to a new scheme that interpolates between the cosmological models explored. The shape of the linear matter power spectrum for standard thermal warm DM models appears to be in mild tension ( 3c2\u3c3 C.L.) with the data compared to nonthermal scenarios. We show that a DM fluid composed by both a warm (thermal) and a cold component is also in tension with the Lyman-\u3b1 forest, at least for large \u3b1 values. This is the first study that allows us to probe the linear small-scale shape of the DM power spectrum for a large set of NCDM models

Mega-parsec scale magnetic fields in low density regions in the SKA era: filaments connecting galaxy clusters and groups

The presence of magnetic fields in galaxy clusters has been well established in recent years, and their importance for the understanding of the physical processes at work in the Intra Cluster Medium has been recognized. Halo and relic sources have been detected in several tens clusters. A strong correlation is present between the halo and relic radio power and the X-ray luminosity. Since cluster X-Ray luminosity and mass are related, the correlation between the radio power and X-ray luminosity could derive from a physical dependence of the radio power on the cluster mass, therefore the cluster mass could be a crucial parameter in the formation of these sources. The goal of this project is to investigate the existence of non-thermal structures beyond the Mpc scale, and associated with lower density regions with respect to clusters of galaxies: galaxy filaments connecting rich clusters. We present a piece of evidence of diffuse radio emission in intergalactic filaments. Moreover, we present and discuss the detection of radio emission in galaxy groups and in faint X-Ray clusters, to analyze non-thermal properties in low density regions with physical conditions similar to galaxy filaments. We discuss how SKA1 observations will allow the investigation of this topic and the study of the presence of diffuse radio sources in low density regions. This will be a fundamental step to understand the origin and properties of cosmological magnetic fields.Comment: 9 pages, 5 figures - to appear as part of 'Cosmic Magnetism' in Proceedings 'Advancing Astrophysics with the SKA (AASKA14)', PoS(AASKA14)10

Non-linear damping of superimposed primordial oscillations on the matter power spectrum in galaxy surveys

Galaxy surveys are an important probe for superimposed oscillations on the primordial power spectrum of curvature perturbations, which are predicted in several theoretical models of inflation and its alternatives. In order to exploit the full cosmological information in galaxy surveys it is necessary to study the matter power spectrum to fully non-linear scales. We therefore study the non-linear clustering in models with superimposed linear and logarithmic oscillations to the primordial power spectrum by running high-resolution dark-matter-only N-body simulations. We fit a Gaussian envelope for the non-linear damping of superimposed oscillations in the matter power spectrum to the results of the N-body simulations for k less than or similar to 0.6 h/Mpc at 0 &lt;= z &lt;= 5 with an accuracy below the percent. We finally use this fitting formula to forecast the capabilities of future galaxy surveys, such as Euclid and Subaru, to probe primordial oscillation down to non-linear scales alone and in combination with the information contained in CMB anisotropies

Comparisons of Cosmological MHD Galaxy Cluster Simulations to Radio Observations

Radio observations of galaxy clusters show that there are $\mu$G magnetic fields permeating the intra-cluster medium (ICM), but it is hard to accurately constrain the strength and structure of the magnetic fields without the help of advanced computer simulations. We present qualitative comparisons of synthetic VLA observations of simulated galaxy clusters to radio observations of Faraday Rotation Measure (RM) and radio halos. The cluster formation is modeled using adaptive mesh refinement (AMR) magneto-hydrodynamic (MHD) simulations with the assumption that the initial magnetic fields are injected into the ICM by active galactic nuclei (AGNs) at high redshift. In addition to simulated clusters in Xu et al. (2010, 2011), we present a new simulation with magnetic field injections from multiple AGNs. We find that the cluster with multiple injection sources is magnetized to a similar level as in previous simulations with a single AGN. The RM profiles from simulated clusters, both $|RM|$ and the dispersion of RM ($\sigma_{RM}$), are consistent at a first-order with the radial distribution from observations. The correlations between the $\sigma_{RM}$ and X-ray surface brightness from simulations are in a broad agreement with the observations, although there is an indication that the simulated clusters could be slightly over-dense and less magnetized with respect to those in the observed sample. In addition, the simulated radio halos agree with the observed correlations between the radio power versus the cluster X-ray luminosity and between the radio power versus the radio halo size. These studies show that the cluster wide magnetic fields that originate from AGNs and are then amplified by the ICM turbulence (Xu et al. 2010) match observations of magnetic fields in galaxy clusters.Comment: Accepted for publication in Ap

Octave bias in an absolute pitch identification task

Octave errors are common within musicians, even among absolute pitch possessors. Overall, evidence shows pitch class and octave to be perceived in a different way, even if they are highly connected. We investigated whether pitch class perception, in an absolute pitch identification task, can be influenced by the octave context, examined among two consecutive octaves. Participants, all musicians with formal musical education, showed different response patterns in the two octaves even if the octave context was explicitly told to be task irrelevant. The direction of errors revealed a consistent tendency to underestimate pitch height in the lowest octave and to overestimate pitch height in the highest octave. Thus, pitch class identification showed to be biased by the octave context. These results are discussed in terms of polarity and pitch enhancement

Thermographic study of the ovine mammary gland during different working vacuum levels

Thermography is a non-contact, non-invasive technique that detects surface heat emitted as infrared radiation. Because skin temperature reflects the status of underlying tissue metabolism and blood circulation, abnormal thermal patterns can signify areas of superficial inflammation or circulatory impairments (i.e. congestion). In sheep different methods have been adopted to measure udder blood circulation and the effect of cold exposure and lactation on the distribution of blood flow. The effect of milking procedures on udder and teat skin temperature was investigated in cows through thermographic scanning. Thermography results in a very useful tool to evaluate, estimate and differentiate short and longer-term tissue reactions to machine milking. The objective of this study was to evaluate the influence of working vacuum level on udder and teat temperature changes during milking procedures and the recovery by indirect monitoring of the circulatory impairments of teat tissue via infrared thermography. Two groups of six lactating Sarda ewes were milked experimentally at two vacuum levels (28 and 42 kPa) and same pulsation parameters (120 cycles/min and 60% ratio). Thermographic images (Flir System, ThermaCam P25, sensitivity of 0.08 °C) of posterior udder area (PUA) and teats (teat base – TB; mid teat – MT and teat tip – TT) were taken pre-milking (PM), during milking (M) (only for PUA), and immediately after milking (IAM) up to 2 minutes after milking (AM+). Temperatures were recovered by processing the thermographic images in ThermaCam Researcher Basic 2.8 SR-1 Software (Flir System). The PUA showed a drop of 1°C in both treatments between PM and M. After milking, values did not show remarkable changes. The vacuum level effect on teats temperature results to be different between treatments. Results during IAM indicate a general drop of the teats temperatures and specifically for high vacuum level (from 39.82 to 37.92°C and from 39.71 to 37.75°C for low and high vacuum level respectively). During AM+ (monitored up to 60 sec - AM +30; up to 90 sec - AM+60 and up to 120 sec – AM+90) the increase of teat temperatures were different (P&lt;0.05) between vacuum levels (AM+30: 38.12 vs 37.54°C; AM+60: 38.19 vs 37.96°C and AM+90: 39.02 vs 38.58°C for low and high vacuum level respectively). Differences among TB, MT and TT were evident also at AM+90 only for the high vacuum level while in low one, at the same time, it was persistent only the difference between TT and TB. The higher teat temperature for the low vacuum level could be attributable to a faster return to a normal condition of the blood flow in all teat locations. Teat circulation impairments due to milking procedures need further surveys

Relativistic plasma and ICM/radio source interaction

The first detection of a diffuse radio source in a cluster of galaxies, dates back to the 1959 (Coma Cluster, Large et al. 1959). Since then, synchrotron radiating radio sources have been found in several clusters, and represent an important cluster component which is linked to the thermal gas. Such sources indicate the existence of large scale magnetic fields and of a population of relativistic electrons in the cluster volume. The observational results provide evidence that these phenomena are related to turbulence and shock-structures in the intergalactic medium, thus playing a major role in the evolution of the large scale structure in the Universe. The interaction between radio sources and cluster gas is well established in particular at the center of cooling core clusters, where feedback from AGN is a necessary ingredient to adequately describe the formation and evolution of galaxies and host clusters.Comment: 8 pages, Review talk at the 274 IAU Symposium "Advances in Plasma Astrophysics", 6-10 Sept 2010, Giardini Naxos, Italy, A. Bonanno, E. de Gouveia Dal Pino and A. Kosovichev, ed

Lyman- \u3b1 Forest Constraints on Primordial Black Holes as Dark Matter

The renewed interest in the possibility that primordial black holes (PBHs) may constitute a significant part of dark matter has provided motivation for revisiting old observational constraints, as well as developing new ones. We present new limits on the PBH abundance, from a comprehensive analysis of high-resolution high-redshift Lyman-\u3b1 forest data. Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction. Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters, we obtain a marginalized upper limit on the PBH mass of fPBHMPBH 3c60M at 2\u3c3, when a Gaussian prior on the reionization redshift is imposed, preventing its posterior distribution from peaking on very high values, which are disfavored by the most recent estimates obtained both through cosmic microwave background and intergalactic medium observations. Such a bound weakens to fPBHMPBH 3c170M when a conservative flat prior is instead assumed. Both limits significantly improve on previous constraints from the same physical observable. We also extend our predictions to nonmonochromatic PBH mass distributions, ruling out large regions of the parameter space for some of the most viable PBH extended mass functions

Out-Of-Focus Holography Tool for the Sardinia Radio Telescope

This document represents a short guide to the out-of-focus holography package for the SRT