Cosmic rays in magnetized intracluster plasma

Recent results are reported on Magnetic Fields in Clusters of Galaxies, Diffuse Radio Emission, and Radio - X-ray connection in Radio Halos.Comment: 2 pages, 1 figure, Invited talk at the JD15 "Magnetic Fields in Diffuse Media", IAU XXVII General Assembly, Rio de Janeir

A double radio halo in the close pair of galaxy clusters Abell 399 and Abell 401

Radio halos are faint radio sources usually located at the center of merging clusters of galaxies. These diffuse radio sources are rare, having so far been found only in about 30 clusters of galaxies, suggesting that particular conditions are needed to form and maintain them. It is interesting to investigate the presence of radio halos in close pairs of interacting clusters in order to possibly clarify their origin in relation to the evolutionary state of the merger. In this work, we study the case of the close pair of galaxy clusters A399 and A401. A401 is already known to contain a faint radio halo, while a hint of diffuse emission in A399 has been suggested based on the NVSS. To confirm this possibility, we analyzed deeper Very Large Array observations at 1.4 GHz of this cluster. We find that the central region of A399 is permeated by a diffuse low-surface brightness radio emission that we classify as a radio halo with a linear size of about 570 kpc and a central brightness of 0.3 micro-Jy/arcsec^2. Indeed, given their comparatively small projected distance of about 3 Mpc, the pair of galaxy clusters A401 and A399 can be considered as the first example of double radio halo system. The discovery of this double halo is extraordinary given the rarity of these radio sources in general and given that current X-ray data seem to suggest that the two clusters are still in a pre-merger state. Therefore, the origin of the double radio halo is likely to be attributed to the individual merging histories of each cluster separately, rather than to the result of a close encounter between the two systems.Comment: 6 pages, 4 figures, accepted for publication in A&

The giant radio halo in Abell 2163

New radio data is presented for the rich cluster Abell 2163. The cluster radio emission is characterized by the presence of a radio halo, which is one of the most powerful and extended halos known so far. In the NE peripheral cluster region, we also detect diffuse elongated emission, which we classify as a cluster relic. The cluster A2163 is very hot and luminous in X-ray. Its central region is probably in a highly non relaxed state, suggesting that this cluster is likely to be a recent merger. The existence of a radio halo in this cluster confirms that halos are associated with hot massive clusters, and confirms the connection between radio halos and cluster merger processes. The comparison between the radio emission of the halo and the cluster X-ray emission shows a close structural similarity. A power law correlation is found between the radio and X-ray brightness, with index = 0.64. We also report the upper limit to the hard X-ray emission, obtained from a BeppoSAX observation. We discuss the implications of our results.Comment: 7 pages, 8 figures (5 in ps and 3 in gif), Accepted for publication in Astron. Astrop

A giant radio halo in the low luminosity X-ray cluster Abell 523

Radio halos are extended and diffuse non-thermal radio sources present at the cluster center, not obviously associated with any individual galaxy. A strong correlation has been found between the cluster X-ray luminosity and the halo radio power. We observe and analyze the diffuse radio emission present in the complex merging structure Abell 523, classified as a low luminosity X-ray cluster, to discuss its properties in the context of the halo total radio power versus X-ray luminosity correlation. We reduced VLA archive observations at 1.4 GHz to derive a deep radio image of the diffuse emission, and compared radio, optical, and X-ray data. Low-resolution VLA images detect a giant radio halo associated with a complex merging region. The properties of this new halo agree with those of radio halos in general discussed in the literature, but its radio power is about a factor of ten higher than expected on the basis of the cluster X-ray luminosity. Our study of this giant radio source demonstrates that radio halos can also be present in clusters with a low X-ray luminosity. Only a few similar cases have so far been found . This result suggests that this source represent a new class of objects, that cannot be explained by classical radio halo models. We suggest that the particle reacceleration related to merging processes is very efficient and/or the X-ray luminosity is not a good indicator of the past merging activity of a cluster.Comment: 5 pages, 6 figures, Astronomy and Astrophysics Letter in pres

Diffuse radio emission in a REFLEX cluster

Deep Very Large Array radio observations are presented for the REFLEX clusters RXCJ0437.1+0043 and RXCJ1314.4-2515. They are at similar distance and show similar X-ray luminosity, but they are quite different in X-ray structure. Indeed RXCJ0437.1+0043 is regular and relaxed, whereas RXCJ1314.4-2515 is characterized by substructure and possible merging processes. The radio images reveal no diffuse emission in RXCJ0437.1+0043, and a complex diffuse structure in RXCJ1314.4-2515. The diffuse source in the latter cluster consists of a central radio halo which extends to the West toward the cluster periphery and bends to the North to form a possible relic. Another extended source is detected in the eastern cluster peripheral region. Although there could be plausible optical identifications for this source, it might also be a relic candidate owing to its very steep spectrum. The present results confirm the tight link between diffuse cluster radio sources and cluster merger processes.Comment: Accepted for publication in A&A. Figures here have been degraded to reduce their size. A version with full resolution figures is available at http://www.ira.cnr.it/~lferetti/OUTGOING/papREFLEX.ps.g

New radio halos and relics in clusters of galaxies

We present here new images of relics and halo sources in rich cluster of galaxies and the correlation between the halo radio surface brightness versus the cluster bolometric X-ray luminosity.Comment: 2 pages, 4 figures. To appear in the Proceedings of the International Conference: "The Origin and Evolution of Cosmic Magnetism"; Bologna 29 August - 2 September 2005; eds R. Beck, G. Brunetti, L. Feretti, and B. Gaensler (Astronomische Nachrichten, 2006

Comparative analysis of the diffuse radio emission in the galaxy clusters A1835, A2029, and Ophiuchus

We recently performed a study of a sample of relaxed, cooling core galaxy clusters with deep Very Large Array observations at 1.4 GHz. We find that in the central regions of A1835, A2029, and Ophiuchus the dominant radio galaxy is surrounded by a diffuse low-brightness radio emission that takes the form of a mini-halo. Here we present the results of the analysis of the extended diffuse radio emission in these mini-halos. In order to investigate the morphological properties of the diffuse radio emission in clusters of galaxies we propose to fit their azimuthally averaged brightness profile with an exponential, obtaining the central brightness and the e-folding radius from which the radio emissivity can be calculated. We investigate the radio properties of the mini-halos in A1835, A2029, and Ophiuchus in comparison with the radio properties of a representative sample of mini-halos and halos already known in the literature. We find that radio halos can have quite different length-scales but their emissivity is remarkably similar from one halo to the other. In contrast, mini-halos span a wide range of radio emissivity. Some of them, like the Perseus mini-halos, are characterized by a radio emissivity which is more than 100 times greater than that of radio halos. On the other hand, the new mini-halos in cooling core clusters analyzed in this work, namely A2029, Ophiuchus, and A1835, have a radio emissivity which is much more typical of halos in merging clusters rather than similar to that of the other mini-halos previously known.Comment: 17 pages, 11 figures, A&A in press. For a version with high quality figures, see http://erg.ca.astro.it/preprints/mini_halo_2

The Effects of Spondylolisthesis on the Human Body

Spondylolisthesis is a rare and unknown disorder to many. The anatomical perplexity beneath its diagnosis is extensive yet crucial to truly understanding this unique anomaly. As a condition that is too often undistinguished and unexplained to countless, it warrants and demands undisputed attention. Spondylolisthesis is an atypical spinal disorder characterized by one vertebra sliding forward in position over the vertebra below it (Rodts, 2017). The victim of this condition faces excruciating pain radiating throughout one’s lower back and frequently into the lower extremities. In cases of increased severity, individuals pursue a variety of treatment modalities ranging from conservative measures such as rest and physical therapy to extensive surgical procedures including spinal fusion. From an outsider’s perspective, one might ask why investigate and study such a rare and random topic? But as a twenty-one-year-old female diagnosed with this exact disease at the age of sixteen, this disorder holds extreme significance and correspondence to my own health hardships. Within the last five years, my personal battle with the neuropathic pain has worsened, forcing me to explore focused research to determine future decisions in relation to my own case of spondylolisthesis. Unfortunately, I found an overall lack of evidence-based research on this uncommon spinal disorder. In order to be better equipped in my knowledge of the disease and its overall effects on the human body, I completed numerous hours of observation at the Boston Children’s Hospital Micheli Center in Waltham, Massachusetts to determine injury prevention methods and proper body mechanic techniques to delay the worsening of spinal disorder symptoms. I also spent time shadowing on an orthopedic unit at Boston Children’s Hospital where they encounter numerous post-operative spinal fusion patients. With the findings from my interdisciplinary collaboration with health care professionals and specialists, I was able to reflect on the prevention methods and current treatment modalities that could be used for an individual at risk or coping with spondylolisthesis, such as myself. As a senior nursing major at the University of Rhode Island, my goal is to utilize the information that I have gained in not only my own personal life but also in my future nursing career as I cross paths with individuals who face spondylolisthesis and similar spinal disorders

The intracluster magnetic field power spectrum in Abell 2382

The goal of this work is to put constraints on the strength and structure of the magnetic field in the cluster of galaxies A2382. We investigate the relationship between magnetic field and Faraday rotation effects in the cluster, using numerical simulations as a reference for the observed polarization properties. For this purpose we present Very Large Array observations at 20 cm and 6 cm of two polarized radio sources embedded in A2382, and we obtained detailed rotation measure images for both of them. We simulated random three-dimensional magnetic field models with different power spectra and thus produced synthetic rotation measure images. By comparing our simulations with the observed polarization properties of the radio sources, we can determine the strength and the power spectrum of intra-cluster magnetic field fluctuations that best reproduce the observations. The data are consistent with a power law magnetic field power spectrum with the Kolmogorov index $n=11/3$, while the outer scale of the magnetic field fluctuations is of the order of 35 kpc. The average magnetic field strength at the cluster center is about 3 $\mu$G and decreases in the external region as the square root of the electron gas density. The average magnetic field strength in the central 1 Mpc$^{3}$ is about 1 $\mu$G.Comment: Comments: 18 pages, 13 figures, accepted by A&A. For a version with high quality figures, see http://erg.ca.astro.it/preprints/guidetti2007