A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.

doi:10.1093/mnras/stv2827

Cited by 42 publications

(95 citation statements)

References 81 publications

(97 reference statements)

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“…In fact, as mentioned in the caption, the circle size refers to the local mean velocity as computed with respect to the galaxy and its ten neighbors. We also performed the 3D optimized adaptive-kernel method of Pisani (1993Pisani ( , 1996; hereafter 3D-DEDICA, see also Girardi et al 2016). The method detects two important density peaks, significant at the > 99.99% confidence level of 31 and 15 galaxies.…”

Section: Optical Propertiesmentioning

confidence: 99%

“…In particular, the detection of polarized emission from radio halos is the key to investigate the magnetic field power spectrum in galaxy clusters (Murgia et al 2004, Govoni et al 2006, Vacca et al 2010, Govoni et al 2013. However, detecting this polarized signal is a very hard task with current radio facilities and so far only three examples of large-scale filamentary polarized structures possibly associated with halo emission have been detected (A2255; Govoni et al 2005, Pizzo et al 2011, MACS J0717.5+3745; Bonafede et al 2009, A523;Girardi et al 2016). …”

Section: Introductionmentioning

confidence: 99%

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Sardinia Radio Telescope observations of Abell 194

Govoni

Murgia

Vacca

et al. 2017

A&A

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Aims. We study the intra-cluster magnetic field in the poor galaxy cluster Abell 194 by complementing radio data, at different frequencies, with data in the optical and X-ray bands. Methods. We analyze new total intensity and polarization observations of Abell 194 obtained with the Sardinia Radio Telescope (SRT). We use the SRT data in combination with archival Very Large Array observations to derive both the spectral aging and Rotation Measure (RM) images of the radio galaxies 3C 40A and 3C 40B embedded in Abell 194. To obtain new additional insights in the cluster structure we investigate the redshifts of 1893 galaxies, resulting in a sample of 143 fiducial cluster members. We analyze the available ROSAT and Chandra observations to measure the electron density profile of the galaxy cluster.Results. The optical analysis indicates that Abell 194 does not show a major and recent cluster merger, but rather agrees with a scenario of accretion of small groups, mainly along the NE-SW direction. Under the minimum energy assumption, the lifetimes of synchrotron electrons in 3C40 B measured from the spectral break are found to be 157±11 Myrs. The break frequency image and the electron density profile inferred from the X-ray emission are used in combination with the RM data to constrain the intra-cluster magnetic field power spectrum. By assuming a Kolmogorov power law power spectrum with a minimum scale of fluctuations of Λ min = 1 kpc, we find that the RM data in Abell 194 are well described by a magnetic field with a maximum scale of fluctuations of Λ max = (64 ± 24) kpc. We find a central magnetic field strength of B 0 = (1.5 ± 0.2) µG, the lowest ever measured so far in galaxy clusters based on Faraday rotation analysis. Further out, the field decreases with the radius following the gas density to the power of η=1.1±0.2. Comparing Abell 194 with a small sample of galaxy clusters, there is a hint of a trend between central electron densities and magnetic field strengths.

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Section: Optical Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sardinia Radio Telescope observations of Abell 194

Govoni

Murgia

Vacca

et al. 2017

A&A

Self Cite

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“…They are characterised by a low surface brightness (S ν ∼ 0.1 − 1 µJy/arcsec 2 at 1.4 GHz), with a steep power-law spectrum (S ν = S 0 (ν/ν 0 ) −α , α 1). Although radio haloes are synchrotron sources, they are generally observed to be unpolarized, though polarized radio halo emission as been detected (up to ∼20% at 1.4 GHz), in galaxy clusters A2255 (Govoni et al 2005), MACS J0717.5+3745 (Bonafede et al 2009), and A523 (Girardi et al 2016). The absence of polarized emission in radio haloes could be attributed to two types of depolarization effects: internal and external depolarization.…”

Section: Introductionmentioning

confidence: 99%

Rotation measure synthesis applied to synthetic SKA images of galaxy clusters

Loi

Murgia

Govoni

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Future observations with next generation radio telescopes will help us to understand the presence and the evolution of magnetic fields in galaxy clusters through the determination of the so-called Rotation Measure (RM). In this work, we applied the RM-synthesis technique on synthetic SKA1-MID radio images of a pair of merging galaxy clusters, measured between 950 and 1750 MHz with a resolution of 10 and a thermal noise of 0.1µJy/beam. The results of our RM-synthesis analysis are compared to the simulations' input parameters. We study two cases: one with radio haloes at the cluster centres, and another without. We found that the information obtained with the RM-synthesis is in general agreement with the input information. Some discrepancies are however present. We characterise them in this work, with the final goal of determining the potential impact of SKA1-MID on the study of cluster magnetic fields.

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“…There are various dynamical signatures of this mass accretion process: (i) the presence of substructures in the galaxy density distribution of the cluster on the sky and in redshift space (e.g., Geller & Beers 1982;Dressler & Shectman 1988;Ramella et al 2007;Grillo et al 2015;Girardi et al 2015;Balestra et al 2016, and references therein), (ii) the clumpy distribution either of the hot intracluster medium (ICM) observed in the X-ray band (e.g., Mohr et al 1993;Kolokotronis et al 2001;Jeltema et al 2005;Zhang et al 2010;Parekh et al 2015) or (iii) of the dark matter distribution inferred from gravitational lensing effects (e.g., Kneib et al 1996;Hoekstra et al 2000;Okabe et al 2014), and (iv) the presence of diffuse radio emission with elongated or peculiar morphologies (e.g., Girardi et al 2016, and references therein).…”

Section: Introductionmentioning

confidence: 99%

The Unrelaxed Dynamical Structure of the Galaxy Cluster Abell 85

Diaferio

Agulli

et al. 2016

ApJ

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For the first time, we explore the dynamics of the central region of a galaxy cluster within r 500 ∼600 h −1 kpc from its center by combining optical and X-ray spectroscopy. We use (1) the caustic technique, whichidentifies the cluster substructures and their galaxy members with optical spectroscopic data, and (2) the X-ray redshift fitting procedure, which estimates the redshift distribution of the intracluster medium (ICM). We use the spatial and redshift distributions of the galaxies and of the X-ray-emitting gas to associate the optical substructures to the X-ray regions. When we apply this approach to Abell 85 (A85), a complex dynamic structure of A85 emerges from our analysis: a galaxy group, with redshift z=0.0509±0.0021 is passing through the cluster center along the line of sight dragging part of the ICM present in the cluster core; two additional groups, at redshift z=0.0547±0.0022 and z=0.0570±0.0020, are going through the cluster in opposite directions, almost perpendicularly to the line of sight, and have substantially perturbed the dynamics of the ICM. An additional group in the outskirts of A85, at redshift z=0.0561±0.0023, is associated with a secondary peak of X-ray emission, at redshift = -+ z 0.0583 0.0047 0.0039 . Although our analysis and results on A85 need to be confirmed by high-resolution spectroscopy, they demonstrate how our new approach can be a powerful tool to constrain the formation history of galaxy clusters by unveiling their central and surrounding structures.

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A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

Cited by 42 publications

References 81 publications

Sardinia Radio Telescope observations of Abell 194

Sardinia Radio Telescope observations of Abell 194

Rotation measure synthesis applied to synthetic SKA images of galaxy clusters

The Unrelaxed Dynamical Structure of the Galaxy Cluster Abell 85

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