scholarly journals ATCA observations of the MACS-Planck Radio Halo Cluster Project

2018 ◽  
Vol 611 ◽  
pp. A94 ◽  
Author(s):  
G. Martinez Aviles ◽  
M. Johnston-Hollitt ◽  
C. Ferrari ◽  
T. Venturi ◽  
J. Democles ◽  
...  
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Wide Band ◽  
Radio Sources ◽  
Diffuse Emission ◽  
Radio Halo ◽  
Full Resolution ◽  
Radio Imaging ◽  
Upper Limits ◽  
Multi Wavelength

Aim. A fraction of galaxy clusters host diffuse radio sources whose origins are investigated through multi-wavelength studies of cluster samples. We investigate the presence of diffuse radio emission in a sample of seven galaxy clusters in the largely unexplored intermediate redshift range (0.3 < z < 0.44). Methods. In search of diffuse emission, deep radio imaging of the clusters are presented from wide band (1.1–3.1 GHz), full resolution (~5 arcsec) observations with the Australia Telescope Compact Array (ATCA). The visibilities were also imaged at lower resolution after point source modelling and subtraction and after a taper was applied to achieve better sensitivity to low surface brightness diffuse radio emission. In case of non-detection of diffuse sources, we set upper limits for the radio power of injected diffuse radio sources in the field of our observations. Furthermore, we discuss the dynamical state of the observed clusters based on an X-ray morphological analysis with XMM-Newton. Results. We detect a giant radio halo in PSZ2 G284.97-23.69 (z = 0.39) and a possible diffuse source in the nearly relaxed cluster PSZ2 G262.73-40.92 (z = 0.421). Our sample contains three highly disturbed massive clusters without clear traces of diffuse emission at the observed frequencies. We were able to inject modelled radio haloes with low values of total flux density to set upper detection limits; however, with our high-frequency observations we cannot exclude the presence of RH in these systems because of the sensitivity of our observations in combination with the high z of the observed clusters.

scholarly journals A low-frequency radio halo survey of the South Pole Telescope SZ-selected clusters with the GMRT

2020 ◽  
Vol 500 (2) ◽  
pp. 2236-2249
Author(s):  
Ramij Raja ◽  
Majidul Rahaman ◽  
Abhirup Datta ◽  
Reinout J van Weeren ◽  
Huib T Intema ◽  
...  
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Radio Sources ◽  
Synchrotron Emission ◽  
Diffuse Emission ◽  
Radio Halo ◽  
South Pole Telescope ◽  
New Radio ◽  
Upper Limits ◽  
Correlation Line

ABSTRACT The presence of non-thermal electrons and large-scale magnetic fields in the intracluster medium is known through the detection of megaparsec (Mpc) scale diffuse radio synchrotron emission. Although a significant amount of progress in finding new diffuse radio sources has happened in the last decade, most of the investigation has been constrained towards massive low-redshift clusters. In this work, we explore clusters with redshift z &gt; 0.3 in search of diffuse radio emission, at 325 MHz with the Giant Metrewave Radio Telescope. This campaign has resulted in the discovery of two new radio haloes (SPT-CL J0013−4906 and SPT-CL J0304−4401) along with two other detections (SPT-CL J2031−4037 and SPT-CL J2248−4431), previously reported (at 325 MHz) in the literature. In addition, we detect a halo candidate in one cluster in our sample, and upper limits for haloes are placed in eight clusters where no diffuse emission is detected. In the P1.4–LX plane, the detected haloes follow the observed correlation, whereas the upper limits lie above the correlation line, indicating the possibility of future detection with sensitive observations.

scholarly journals Exploring Diffuse Radio Emission in the Southern Sky

2021 ◽  
Author(s):  
◽  
Sara Shakouri
Keyword(s):  
Magnetic Field ◽  
Galaxy Clusters ◽  
Magnetic Field Direction ◽  
Diffuse Sources ◽  
Radio Halo ◽  
New Correlation ◽  
Upper Limits ◽  
Multi Wavelength ◽  
High Resolution Images ◽  
Radio Halos

<p>This thesis investigates currently observed correlations between the thermal and non-thermal (radio halos) components of galaxy clusters, and seeks to verify the reliability of the proposed radio halo scaling relations presented in the literature. It employs a two-pronged approach: 1) a statistical examination of 15 galaxy clusters; and 2) detailed multi-wavelength analysis of individual objects of interest.  We first investigated radio data for 15 galaxy clusters drawn from the parent REXCESS sample observed with the ATCA at 1.4 GHz to conduct a radio halo survey. Examination of available and re-processed low resolution images revealed cluster-scale diffuse objects in three clusters. One was a radio halo candidate in Abell 3888 (A3888), with the two remaining diffuse sources being radio relic candidates. Follow-up observations of the candidate clusters were performed in July and December 2011, and March 2012, with the upgraded ATCA (CABB). Radio observations with CABB in different array configurations were used to provide the required resolution and sensitivity to a wider range of angular scales to probe the candidate diffuse sources. Examination of the final CABB images confirmed the existence of the radio halo in A3888; however, the remaining candidates were found to be a head-tail galaxy and a very bright radio galaxy with extended emission. As this thesis presents some of the earliest CABB observations, new data reduction and imaging procedures were necessarily developed and presented here.  The statistical component of this thesis uses a halo sample obtained from the combined detection of this work and the literature to derive new correlations between the cluster observables and the radio halo power. The new correlation between the X-ray luminosity and radio halo power derived here is flatter than the previous correlation in the literature, suggesting that massive clusters may host lower power halos than previously thought. In addition, we derived the upper limits of the undetected power of possible radio halos for our non-halo clusters via injection of fake radio halos into the UV data. Our derived upper limits with respect to the anticipated halo powers according to the previous and new correlations and their interpretations are discussed in the thesis. The distribution of the combined upper limits (this work and the literature) compared to our new correlation shows no sign of the strong bi-modality found in the literature.  As previously mentioned, we detected a giant radio halo in A3888. We observed A3888 with the AAOmega spectrograph to infer the dynamics of the cluster. We measured the spectra of 254 galaxies within a 300 radius from the core of A3888 and combined these data with the available literature redshifts in the region. We identified 71 member galaxies of A3888 and examined the density contours, which indicated that the distribution of the member galaxies is elongated along an east-west axis. This elongation might be indicative of dynamical interactions in the cluster; however, there is no statistically significant deviation from Gaussianity in the velocity data. We then carried out a Lee-Fitchett 3D substructure test and found that A3888 is bimodal and has two subgroups.  The head-tail galaxy mentioned earlier in one of the clusters was originally thought to be a radio relic candidate. Owing to available broadband polarimetric data and well-separated jets of the head-tail galaxy, we investigated the magnetic field direction of the head-tail galaxy and conclude it is highly likely that a helical magnetic field is present in the jets.  We present the high-resolution images of our 15 clusters and create a catalogue of the detected sources. Finally, we discuss concerns with the current radio halo detections in the literature, and how radio halo surveys could be designed in the future to yield unbiased results.</p>

scholarly journals Exploring Diffuse Radio Emission in the Southern Sky

2021 ◽  
Author(s):  
◽  
Sara Shakouri
Keyword(s):  
Magnetic Field ◽  
Galaxy Clusters ◽  
Magnetic Field Direction ◽  
Diffuse Sources ◽  
Radio Halo ◽  
New Correlation ◽  
Upper Limits ◽  
Multi Wavelength ◽  
High Resolution Images ◽  
Radio Halos

<p>This thesis investigates currently observed correlations between the thermal and non-thermal (radio halos) components of galaxy clusters, and seeks to verify the reliability of the proposed radio halo scaling relations presented in the literature. It employs a two-pronged approach: 1) a statistical examination of 15 galaxy clusters; and 2) detailed multi-wavelength analysis of individual objects of interest.  We first investigated radio data for 15 galaxy clusters drawn from the parent REXCESS sample observed with the ATCA at 1.4 GHz to conduct a radio halo survey. Examination of available and re-processed low resolution images revealed cluster-scale diffuse objects in three clusters. One was a radio halo candidate in Abell 3888 (A3888), with the two remaining diffuse sources being radio relic candidates. Follow-up observations of the candidate clusters were performed in July and December 2011, and March 2012, with the upgraded ATCA (CABB). Radio observations with CABB in different array configurations were used to provide the required resolution and sensitivity to a wider range of angular scales to probe the candidate diffuse sources. Examination of the final CABB images confirmed the existence of the radio halo in A3888; however, the remaining candidates were found to be a head-tail galaxy and a very bright radio galaxy with extended emission. As this thesis presents some of the earliest CABB observations, new data reduction and imaging procedures were necessarily developed and presented here.  The statistical component of this thesis uses a halo sample obtained from the combined detection of this work and the literature to derive new correlations between the cluster observables and the radio halo power. The new correlation between the X-ray luminosity and radio halo power derived here is flatter than the previous correlation in the literature, suggesting that massive clusters may host lower power halos than previously thought. In addition, we derived the upper limits of the undetected power of possible radio halos for our non-halo clusters via injection of fake radio halos into the UV data. Our derived upper limits with respect to the anticipated halo powers according to the previous and new correlations and their interpretations are discussed in the thesis. The distribution of the combined upper limits (this work and the literature) compared to our new correlation shows no sign of the strong bi-modality found in the literature.  As previously mentioned, we detected a giant radio halo in A3888. We observed A3888 with the AAOmega spectrograph to infer the dynamics of the cluster. We measured the spectra of 254 galaxies within a 300 radius from the core of A3888 and combined these data with the available literature redshifts in the region. We identified 71 member galaxies of A3888 and examined the density contours, which indicated that the distribution of the member galaxies is elongated along an east-west axis. This elongation might be indicative of dynamical interactions in the cluster; however, there is no statistically significant deviation from Gaussianity in the velocity data. We then carried out a Lee-Fitchett 3D substructure test and found that A3888 is bimodal and has two subgroups.  The head-tail galaxy mentioned earlier in one of the clusters was originally thought to be a radio relic candidate. Owing to available broadband polarimetric data and well-separated jets of the head-tail galaxy, we investigated the magnetic field direction of the head-tail galaxy and conclude it is highly likely that a helical magnetic field is present in the jets.  We present the high-resolution images of our 15 clusters and create a catalogue of the detected sources. Finally, we discuss concerns with the current radio halo detections in the literature, and how radio halo surveys could be designed in the future to yield unbiased results.</p>

scholarly journals Diffuse radio emission in the galaxy cluster SPT-CL J2031−4037: a steep-spectrum intermediate radio halo?

2020 ◽  
Vol 493 (1) ◽  
pp. L28-L32 ◽  
Author(s):  
Ramij Raja ◽  
Majidul Rahaman ◽  
Abhirup Datta ◽  
Jack O Burns ◽  
H T Intema ◽  
...  
Keyword(s):  
Radio Emission ◽  
Spectral Index ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Transition System ◽  
Cluster Galaxy ◽  
Radio Halo ◽  
Spectrum Radio ◽  
Upper Limits ◽  
The Galaxy

ABSTRACT The advent of sensitive low-frequency radio observations has revealed a number of diffuse radio objects with peculiar properties that are challenging our understanding of the physics of the intracluster medium. Here, we report the discovery of a steep-spectrum radio halo surrounding the central brightest cluster galaxy (BCG) in the galaxy cluster SPT-CL J2031−4037. This cluster is morphologically disturbed yet has a weak cool core, an example of a cool-core/non-cool-core transition system, which harbours a radio halo ∼0.7 Mpc in size. The halo emission detected at 1.7 GHz is less extended compared to that in the 325 MHz observation, and the spectral index of the part of the halo visible at the 325 MHz to 1.7 GHz frequencies was found to be −1.35 ± 0.07. Also, P1.4 GHz was found to be 0.77 × 1024 W Hz−1, which falls in the region where radio mini-haloes, halo upper limits and ultra-steep-spectrum (USS) haloes are found in the P1.4 GHz–LX plane. Additionally, simulations presented in the paper provide support for the scenario of the steep spectrum. The diffuse radio emission found in this cluster may be a steep-spectrum ‘intermediate’ or ‘hybrid’ radio halo that is transitioning into a mini-halo.

scholarly journals Extended radio emission in clusters of galaxies: recent Westerbork observations

1978 ◽  
Vol 79 ◽  
pp. 153-155
Author(s):  
E.A. Valentijn ◽  
H. van der Laan
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Extended Radio

Whether galaxy clusters, in addition to a number of radio sources associated with individual cluster members, have an extended radio emitting region designated as cluster halo is in an interesting way related to several questions concerning cluster characteristics:

Multi-wavelength emission from dark matter annihilation processes in galaxy clusters and dark matter sub-halos

2019 ◽  
Vol 15 (S356) ◽  
pp. 390-392
Author(s):  
Remudin Reshid Mekuria
Keyword(s):  
Dark Matter ◽  
Radio Emission ◽  
Galaxy Clusters ◽  
High Mass ◽  
Stellar Content ◽  
Dark Matter Annihilation ◽  
Multi Wavelength ◽  
Crucial Information ◽  
Wavelength Emission ◽  
Statistical Studies

AbstractMulti-wavelength emission maps from dark matter (DM) annihilation processes in galaxy clusters are produced using Marenostrum-MultiDark SImulation of galaxy Clusters (MUSIC-2) high resolution cosmological simulations. Comparison made with observational radio emission flux data (spectral shape) and the spatial distribution from the simulated emission maps show that secondary particles from DM annihilation could describe the origin of energetic particles which are the sources of the diffuse radio emission observed in large number of galaxy clusters. DM sub-halos which are dominantly composed of DM, but with very little or no gas and stellar content, are ideal objects to study the nature and properties of DM. Therefore, statistical studies of a large number of them as well the emission maps of high mass-to-light ratio DM sub-halos will not only explain the observed diffused radio emission but also provide very crucial information about the nature and properties of DM particles.

scholarly journals Evolutionary phases of merging clusters as seen by LOFAR

2019 ◽  
Vol 622 ◽  
pp. A25 ◽  
Author(s):  
A. Wilber ◽  
M. Brüggen ◽  
A. Bonafede ◽  
D. Rafferty ◽  
T. W. Shimwell ◽  
...  
Keyword(s):  
Radio Emission ◽  
Energy Losses ◽  
Archival Data ◽  
Radio Sources ◽  
Mass System ◽  
Radio Halo ◽  
Cluster Centre ◽  
Sky Survey ◽  
Low Mass ◽  
Larger Sample

Massive, merging galaxy clusters often host giant, diffuse radio sources that arise from shocks and turbulence; hence, radio observations can be useful for determining the merger state of a cluster. In preparation for a larger study, we selected three clusters – Abell 1319, Abell 1314, and RXC J1501.3+4220 (Z7215) – making use of the new LOFAR Two-Metre Sky Survey (LoTSS) at 120–168 MHz, and together with archival data, show that these clusters appear to be in pre-merging, merging, and post-merging states, respectively. We argue that Abell 1319 is likely in its pre-merging phase, where three separate cluster components are about to merge. There are no radio haloes nor radio relics detected in this system. Abell 1314 is a highly disturbed, low-mass cluster that is likely in the process of merging. This low-mass system does not show a radio halo, however, we argue that the merger activates mechanisms that cause electron re-acceleration in the large 800 kpc radio tail associated with IC 711. In the cluster Z7215 we discover diffuse radio emission at the cluster centre, and we classify this emission as a radio halo, although it is dimmer and smaller than expected by the radio halo power versus cluster mass correlation. We suggest that the disturbed cluster Z7215 is in its post-merging phase. Systematic studies of this kind over a larger sample of clusters observed with LoTSS will help to constrain the timescales involved in turbulent re-acceleration and the subsequent energy losses of the underlying electrons.

scholarly journals Diffuse Extragalactic Emission at Low Frequencies within the Epoch of Reionization 0-hour Field

2021 ◽  
Author(s):  
◽  
Stefan Duchesne
Keyword(s):  
Radio Emission ◽  
Sample Size ◽  
Galaxy Clusters ◽  
Low Frequency ◽  
Small Sample ◽  
Point Sources ◽  
Scaling Relations ◽  
Low Frequencies ◽  
Cluster Emission ◽  
Radio Halo

<p>Low-frequency radio imaging of the southern sky has become available with the advent of the Murchison Widefield Array (MWA). The topic of this thesis is the study of extended, low-frequency radio emission, with a primary focus on the non-thermal synchrotron emission associated with the intra-cluster medium (ICM) of galaxy clusters. We do not limit the study to such emission, however, and investigate a small sample of other interesting and extended radio emission from objects in the southern sky.   A significant portion of this work is invested in detecting, and characterising, extended, diffuse radio emission from galaxy clusters within a 45 degree by 45 degree region of the southern sky centred on R.A. = 0 hours, decl. = -27 degrees. This field is chosen as a deep MWA image has been made available which is sensitive to extended structures. Within the field we search for low-frequency, diffuse cluster emission, previously detected or otherwise. In doing so we find 34 diffuse radio sources, 3 of which are newly detected haloes, 1 newly detected relic with many new candidates of each. Further, we detect a new phoenix candidate as well as 2 candidate dead radio galaxies at the centre of clusters. We confirm previous observations of such emission as well, and measure properties such as their integrated flux densities, spectral indices, and sizes where possible. We compare our sample of haloes with previously detected haloes and revisit established scaling relations of the radio halo power with the cluster X-ray luminosity and mass. We find that both scaling relations are consistent with previous findings despite the increase in sample size, though note that the raw scatter in the data for best-fitting parameters increases with increase in sample size. In this, we demonstrate the utility of low-frequency radio telescopes like the MWA in detecting such emission, showing that the MWA is pushing into higher-redshift, lower-mass systems, though we caution that the low resolution of the MWA can work against us.  We follow-up on two galaxy clusters found to host extended emission - Abell S1136 and Abell S1063. In the case of Abell S1136 we observe the emission at its centre with the Australia Telescope Compact Array (ATCA) and determine the presence of a core, suggesting the emission to be that of an ancient episode of an active galactic nucleus in the central elliptical of the cluster, ESO 470-G020. After reducing archival ATCA data for Abell S1063 we find no evidence of a halo and consider the source to be constructed of blended point sources. We close with a description of a strong double-lobed radio source associated with a non-elliptical host ESO 472-G013, likely a spiral or irregular galaxy, that was found serendipitously whilst searching for diffuse cluster emission. We explore the host within the context of star-formation, and consider the possible origins of the AGN and lobes due to interaction with either the nearby spiral, ESO 472-G012, or a past or ongoing merger event.</p>

scholarly journals Particle acceleration in a nearby galaxy cluster pair: the role of cluster dynamics

2019 ◽  
Vol 630 ◽  
pp. A77 ◽  
Author(s):  
A. Botteon ◽  
R. Cassano ◽  
D. Eckert ◽  
G. Brunetti ◽  
D. Dallacasa ◽  
...  
Keyword(s):  
Radio Emission ◽  
Galaxy Clusters ◽  
Surface Brightness ◽  
Power Spectra ◽  
Galaxy Cluster ◽  
Cluster Center ◽  
Nearby Galaxy ◽  
X Ray ◽  
Radio Halo ◽  
Cluster Pair

Context. Diffuse radio emission associated with the intracluster medium (ICM) is observed in a number of merging galaxy clusters. It is currently believed that a fraction of the kinetic energy in mergers is channeled into nonthermal components, such as turbulence, cosmic rays, and magnetic fields, which may lead to the formation of giant synchrotron sources in the ICM. Aims. Studying merging galaxy clusters in different evolutionary phases is fundamental for understanding the origin of radio emission in the ICM. Methods. We observed the nearby galaxy cluster pair RXC J1825.3+3026 (z ∼ 0.065) and CIZA J1824.1+3029 (z ∼ 0.071) at 120 − 168 MHz with the LOw Frequency ARray (LOFAR) and made use of a deep (240 ks) XMM-Newton dataset to study the nonthermal and thermal properties of the system. RXC J1825.3+3026 is in a complex dynamical state, with a primary ongoing merger in the E-W direction and a secondary later stage merger with a group of galaxies in the SW, while CIZA J1824.1+3029 is dynamically relaxed. These two clusters are in a pre-merger phase. Results. We report the discovery of a Mpc-scale radio halo with a low surface brightness extension in RXC J1825.3+3026 that follows the X-ray emission from the cluster center to the remnant of a galaxy group in the SW. This is among the least massive systems and the faintest giant radio halo known to date. In contrast to this, no diffuse radio emission is observed in CIZA J1824.1+3029, nor in the region between the pre-merger cluster pair. The power spectra of the X-ray surface brightness fluctuations of RXC J1825.3+3026 and CIZA J1824.1+3029 are in agreement with the findings for clusters exhibiting a radio halo and clusters where no radio emission has been detected, respectively. Conclusions. We provide quantitative support to the idea that cluster mergers play a crucial role in the generation of nonthermal components in the ICM.

scholarly journals New giant radio sources and underluminous radio halos in two galaxy clusters

2018 ◽  
Vol 609 ◽  
pp. A61 ◽  
Author(s):  
V. Cuciti ◽  
G. Brunetti ◽  
R. van Weeren ◽  
A. Bonafede ◽  
D. Dallacasa ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Recent Literature ◽  
Radio Sources ◽  
Diffuse Emission ◽  
Very Large Array ◽  
Radio Halo ◽  
Mechanisms Of Formation ◽  
Formation And Evolution ◽  
Radio Power ◽  
Radio Halos

Aims. The aim of this work is to analyse the radio properties of the massive and dynamically disturbed clusters Abell 1451 and Zwcl 0634.1+4750, especially focusing on the possible presence of diffuse emission. Methods. We present new Giant Metrewave Radio Telescope (GMRT) 320 MHz and Jansky Very Large Array (JVLA) 1.5 GHz observations of these two clusters. Results. We found that both Abell 1451 and Zwcl 0634.1+4750 host a radio halo with a typical spectrum (α ~ 1−1.3). Similarly to a few other cases reported in the recent literature, these radio halos are significantly fainter in radio luminosity with respect to the current radio power-mass correlations and they are smaller than classical giant radio halos. These underluminous sources might contribute to elucidating the complex mechanisms of formation and evolution of radio halos. Furthermore, we detected a candidate radio relic at large distance from the cluster centre in Abell 1451 and a peculiar head-tail (HT) radio galaxy in Zwcl 0634.1+4750, which might be interacting with a shock front.

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