scholarly journals LOFAR detection of a low-power radio halo in the galaxy cluster Abell 990

2020 ◽  
Vol 501 (1) ◽  
pp. 576-586
Author(s):  
D N Hoang ◽  
T W Shimwell ◽  
E Osinga ◽  
A Bonafede ◽  
M Brüggen ◽  
...  
Keyword(s):  
Low Frequency ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Radio Halo ◽  
The Galaxy ◽  
Major Merger ◽  
Murchison Widefield Array ◽  
Low X ◽  
Massive Clusters ◽  
Radio Power

ABSTRACT Radio haloes are extended (∼Mpc), steep spectrum sources found in the central region of dynamically disturbed clusters of galaxies. Only a handful of radio haloes have been reported to reside in galaxy clusters with a mass $M_{500}\lesssim 5\times 10^{14}\, \mathrm{ M}_\odot$. In this paper, we present a LOw Frequency ARray (LOFAR) 144 MHz detection of a radio halo in the galaxy cluster Abell 990 with a mass of $M_{500}=(4.9\pm 0.3)\times 10^{14}\, \mathrm{ M}_\odot$. The halo has a projected size of ${\sim} 700\, {\rm kpc}$ and a flux density of $20.2\pm 2.2\, {\rm mJy}$ or a radio power of $1.2\pm 0.1\times 10^{24}\, {\rm W\, Hz}^{-1}$ at the cluster redshift (z = 0.144) that makes it one of the two haloes with the lowest radio power detected to date. Our analysis of the emission from the cluster with Chandra archival data using dynamical indicators shows that the cluster is not undergoing a major merger but is a slightly disturbed system with a mean temperature of $5\, {\rm keV}$. The low X-ray luminosity of $L_{\mathrm{ X}}=(3.66\pm 0.08)\times 10^{44}\, {\rm erg\, s}^{-1}$ in the 0.1–2.4 keV band implies that the cluster is one of the least luminous systems known to host a radio halo. Our detection of the radio halo in Abell 990 opens the possibility of detecting many more haloes in poorly explored less massive clusters with low-frequency telescopes such as LOFAR, Murchison Widefield Array (MWA, Phase II), and upgraded Giant Metrewave Radio Telescope (uGMRT).

scholarly journals Reaching thermal noise at ultra-low radio frequencies

2020 ◽  
Vol 642 ◽  
pp. A85 ◽  
Author(s):  
F. de Gasperin ◽  
G. Brunetti ◽  
M. Brüggen ◽  
R. van Weeren ◽  
W. L. Williams ◽  
...  
Keyword(s):  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Radio Halo ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Background Turbulence ◽  
Post Shock

Context. Ultra-low frequency observations (< 100 MHz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. Nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays. Aims. We aim to obtain the first thermal-noise limited (∼1.5 mJy beam−1) deep continuum radio map using the Low Frequency Array’s Low Band Antenna (LOFAR LBA) system. Our demonstration observation targeted the galaxy cluster RX J0603.3+4214 (known as the Toothbrush cluster). We used the resulting ultra-low frequency (39–78 MHz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo. Methods. We describe the data reduction we used to calibrate LOFAR LBA observations. The resulting image was combined with observations at higher frequencies (LOFAR 150 MHz and VLA 1500 MHz) to extract spectral information. Results. We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using all Dutch stations at a central frequency of 58 MHz. With eight hours of data, we reached an rms noise of 1.3 mJy beam−1 at a resolution of 18″ × 11″. Conclusions. The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA. The analysis of the radio spectra shows that the radio relic extends to distances of 800 kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of < 300 kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated downstream by background turbulence, possibly combined with projection effects with respect to the radio halo.

scholarly journals A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2–4420: a mini-halo in transition?

2019 ◽  
Vol 486 (1) ◽  
pp. L80-L84 ◽  
Author(s):  
Ruta Kale ◽  
Krishna M Shende ◽  
Viral Parekh
Keyword(s):  
Radio Source ◽  
Surface Brightness ◽  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Radio Sources ◽  
Cluster Galaxy ◽  
X Ray ◽  
Radio Halo ◽  
The Galaxy ◽  
Radio Power

ABSTRACT Diffuse radio sources associated with the intra-cluster medium are direct probes of the cosmic ray electrons and magnetic fields. We report the discovery of a diffuse radio source in the galaxy cluster RXCJ0232.2–4420 (SPT-CL J0232–4421, z = 0.2836) using 606 MHz observations with the Giant Metrewave Radio Telescope. The diffuse radio source surrounds the Brightest Cluster Galaxy in the cluster-like typical radio mini-haloes. However the total extent of it is 550 × 800 kpc2, which is larger than mini-haloes and similar to that of radio haloes. The BCG itself is also a radio source with a marginally resolved core at 7 arcsec (30 kpc) resolution. We measure the 606 MHz flux density of the RH to be 52 ± 5 mJy. Assuming a spectral index of 1.3, the 1.4 GHz radio power is 4.5 × 1024 W Hz−1. The dynamical state of the cluster has been inferred to be 'relaxed’ and also as 'complex’, depending on the classification methods based on the morphology of the X-ray surface brightness. This system thus seems to be in the transition phase from a mini-halo to a radio halo.

scholarly journals Galaxy and Mass Assembly (GAMA): Selection of the Most Massive Clusters

2014 ◽  
Vol 11 (S308) ◽  
pp. 215-216
Author(s):  
Héctor J. Ibarra-Medel ◽  
Maritza Lara-López ◽  
Omar López-Cruz
Keyword(s):  
Galaxy Cluster ◽  
Mass Range ◽  
Clusters Of Galaxies ◽  
The Galaxy ◽  
Sunyaev Zel'dovich Effect ◽  
Point Correlation ◽  
Point Correlation Function ◽  
Mass Assembly ◽  
Massive Clusters ◽  
Selection Of

AbstractWe have developed a galaxy cluster finding technique based on the Delaunay Tessellation Field Estimator (DTFE) combined with caustic analysis. Our method allows us to recover clusters of galaxies within the mass range of $10^{12}$ to $10^{16}\ \mathcal{M}_{\odot}$. We have found a total of 113 galaxy clusters in the Galaxy and Mass Assembly survey (GAMA). In the corresponding mass range, the density of clusters found in this work is comparable to the density traced by clusters selected by the thermal Sunyaev Zel'dovich Effect; however, we are able to cover a wider mass range. We present the analysis of the two-point correlation function for our cluster sample.

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 Ultra-steep spectrum emission in the merging galaxy cluster Abell 1914

2019 ◽  
Vol 622 ◽  
pp. A22 ◽  
Author(s):  
S. Mandal ◽  
H. T. Intema ◽  
T. W. Shimwell ◽  
R. J. van Weeren ◽  
A. Botteon ◽  
...  
Keyword(s):  
Low Frequency ◽  
Galaxy Cluster ◽  
Diffuse Emission ◽  
Radio Observations ◽  
Very Large Array ◽  
Radio Halo ◽  
The Galaxy ◽  
Distinct Source ◽  
Relativistic Particles ◽  
Massive Galaxy

A number of radio observations have revealed the presence of large synchrotron-emitting sources associated with the intra-cluster medium. There is strong observational evidence that the emitting particles have been (re-)accelerated by shocks and turbulence generated during merger events. The particles that are accelerated are thought to have higher initial energies than those in the thermal pool but the origin of such mildly relativistic particles remains uncertain and needs to be further investigated. The galaxy cluster Abell 1914 is a massive galaxy cluster in which X-ray observations show clear evidence of merging activity. We carried out radio observations of this cluster with the LOw Frequency ARay (LOFAR) at 150 MHz and the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. We also analysed Very Large Array (VLA) 1.4 GHz data, archival GMRT 325 MHz data, CFHT weak lensing data and Chandra observations. Our analysis shows that the ultra-steep spectrum source (4C38.39; α ≲ −2), previously thought to be part of a radio halo, is a distinct source with properties that are consistent with revived fossil plasma sources. Finally, we detect some diffuse emission to the west of the source 4C38.39 that could belong to a radio halo.

scholarly journals Diffuse galaxy cluster emission at 168 MHz within the Murchison Widefield Array Epoch of Reionization 0-h field

2021 ◽  
Vol 38 ◽  
Author(s):  
S. W. Duchesne ◽  
M. Johnston-Hollitt ◽  
A. R. Offringa ◽  
G. W. Pratt ◽  
Q. Zheng ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Galaxy Cluster ◽  
Scaling Relations ◽  
Cluster Emission ◽  
X Ray ◽  
Diffuse Sources ◽  
Radio Halo ◽  
The Galaxy ◽  
Murchison Widefield Array

Abstract We detect and characterise extended, diffuse radio emission from galaxy clusters at 168 MHz within the Epoch of Reionization 0-h field: a $45^{\circ} \times 45^{\circ}$ region of the southern sky centred on R. A. ${}= 0^{\circ}$ , decl. ${}=-27^{\circ}$ . We detect 29 sources of interest; a newly detected halo in Abell 0141; a newly detected relic in Abell 2751; 4 new halo candidates and a further 4 new relic candidates; and a new phoenix candidate in Abell 2556. Additionally, we find nine clusters with unclassifiable, diffuse steep-spectrum emission as well as a candidate double relic system associated with RXC J2351.0-1934. We present measured source properties such as their integrated flux densities, spectral indices ( $\alpha$ , where $S_\nu \propto \nu^\alpha$ ), and sizes where possible. We find several of the diffuse sources to have ultra-steep spectra including the halo in Abell 0141, if confirmed, showing $\alpha \leq -2.1 \pm 0.1$ with the present data making it one of the steepest-spectrum haloes known. Finally, we compare our sample of haloes with previously detected haloes and revisit established scaling relations of the radio halo power ( $P_{1.4}$ ) with the cluster X-ray luminosity ( $L_{\textrm{X}}$ ) and mass ( $M_{500}$ ). We find that the newly detected haloes and candidate haloes are consistent with the $P_{1.4}$ – $L_{\textrm{X}}$ and $P_{1.4}$ – $M_{500}$ relations and see an increase in scatter in the previously found relations with increasing sample size likely caused by inhomogeneous determination of $P_{1.4}$ across the full halo sample. We show that the MWA is capable of detecting haloes and relics within most of the galaxy clusters within the Planck catalogue of Sunyaev–Zel’dovich sources depending on exact halo or relic properties.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

Imaging the Cosmic Microwave Background with the Arcminute Cosmology Bolometer Array Receiver

2005 ◽  
Vol 216 ◽  
pp. 43-50
Author(s):  
J. B. Peterson ◽  
A. K. Romer ◽  
P. L. Gomez ◽  
P. A. R. Ade ◽  
J. J. Bock ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Cosmological Parameters ◽  
Galaxy Cluster ◽  
Clusters Of Galaxies ◽  
Microwave Background ◽  
Bolometer Array ◽  
The Galaxy ◽  
Millimeter Wave Receiver ◽  
Array Receiver

The Arcminute Cosmology Bolometer Array Receiver (Acbar) is a multifrequency millimeter-wave receiver optimized for observations of the Cosmic Microwave Background (CMB) and the Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. Acbar was installed on the 2.1 m Viper telescope at the South Pole in January 2001 and the results presented here incorporate data through July 2002. The power spectrum of the CMB at 150 GHz over the range ℓ = 150 — 3000 measured by Acbar is presented along with estimates for the values of the cosmological parameters within the context of ΛCDM models. The inclusion of ΩΛ greatly improves the fit to the power spectrum. Three-frequency images of the SZ decrement/increment are also presented for the galaxy cluster 1E0657–67.

scholarly journals Sunyaev-Zel’dovich detection of the galaxy cluster Cl J1449+0856 at z = 1.99: The pressure profile in uv space

2019 ◽  
Vol 629 ◽  
pp. A104 ◽  
Author(s):  
R. Gobat ◽  
E. Daddi ◽  
R. T. Coogan ◽  
A. M. C. Le Brun ◽  
F. Bournaud ◽  
...  
Keyword(s):  
Spatial Scales ◽  
High Redshift ◽  
Galaxy Cluster ◽  
Pressure Profile ◽  
Cluster Galaxy ◽  
X Ray ◽  
Amplitude Profile ◽  
The Galaxy ◽  
Sunyaev Zel'dovich Effect ◽  
Massive Clusters

We present Atacama Large Millimetre Array and Atacama Compact Array observations of the Sunyaev-Zel’dovich effect in the z = 2 galaxy cluster Cl J1449+0856, an X-ray-detected progenitor of typical massive clusters in the present day Universe. While in a cleaned but otherwise untouched 92 GHz map of this cluster little to no negative signal is visible, careful subtraction of known sub-millimetre emitters in the uv plane reveals a decrement at 5σ significance. The total signal is −190 ± 36 μJy, with a peak offset by 5″–9″ (∼50 kpc) from both the X-ray centroid and the still-forming brightest cluster galaxy. A comparison of the recovered uv-amplitude profile of the decrement with different pressure models allows us to derive total mass constraints consistent with the ∼6 × 1013M⊙ estimated from X-ray data. Moreover, we find no strong evidence for a deviation of the pressure profile with respect to local galaxy clusters, although a slight tension at small-to-intermediate spatial scales suggests a flattened central profile, opposite to that seen in a cool core and possibly an AGN-related effect. This analysis of the lowest mass single SZ detection so far illustrates the importance of interferometers when observing the SZ effect in high-redshift clusters, the cores of which cannot be considered quiescent, such that careful subtraction of galaxy emission is necessary.

scholarly journals Galaxies and clusters of galaxies as peak patches of the density field

2019 ◽  
Vol 490 (2) ◽  
pp. 1693-1696 ◽  
Author(s):  
Masataka Fukugita ◽  
Hans Böhringer
Keyword(s):  
Gravitational Lensing ◽  
Mass Density ◽  
Galaxy Cluster ◽  
Mass Range ◽  
Mass Function ◽  
Clusters Of Galaxies ◽  
Density Fraction ◽  
The Galaxy ◽  
Consistent Picture ◽  
Low Mass

ABSTRACT The mass function of galaxies and clusters of galaxies can be derived observationally based on different types of observations. In this study we test if these observations can be combined to a consistent picture which is also in accord with structure formation theory. The galaxy data comprise the optical galaxy luminosity function and the gravitational lensing signature of the galaxies, while the galaxy cluster mass function is derived from the X-ray luminosity distribution of the clusters. We show the results of the comparison in the form of the mass density fraction that is contained in collapsed objects relative to the mean matter density in the Universe. The mass density fraction in groups and clusters of galaxies extrapolated to low masses agrees very well with that of the galaxies: both converge at the low mass limit to a mass fraction of about 28 per cent if the outer radii of the objects are taken to be r200. Most of the matter contained in collapsed objects is found in the mass range $M_{200} \sim 10^{12}\!-\!10^{14}\, h^{-1}_{70} \, \mathrm{M}_\odot$, while a larger amount of the cosmic matter resides outside of r200 of collapsed objects.

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