Social/Cultural Anthropology: On the Edge of the Forest: Cultural Adaptation and Cognitive Development in Central Africa. <i>J. W. Berry, J. M. H. van de Koppel, C. Sénéchal, R. C. Annis, S. Bahuchet, L. L. Cavalli‐Sforza</i>, and <i>H. A. Witkin.</i>

Price‐Williams, Douglass

doi:10.1525/aa.1988.90.3.02a00430

Cited by 23 publications

(41 citation statements)

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“…The frequency range covered is 115 − 162 MHz. We expect to achieve approximately ≈ 50 − 100 µJy beam −1 sensitivity with LOFAR (based on similar observations by Williams et al 2016). Table 2.…”

Section: Ancillary Multi-wavelength Observations Of the Superclass Fieldsupporting

confidence: 58%

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

Battye¹,

Brown²,

Casey

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The SuperCLuster Assisted Shear Survey (SuperCLASS) is a legacy programme using the e-MERLIN interferometric array. The aim is to observe the sky at L-band (1.4 GHz) to a r.m.s. of 7 µJy beam −1 over an area of ∼ 1 deg 2 centred on the Abell 981 supercluster. The main scientific objectives of the project are: (i) to detect the effects of weak lensing in the radio in preparation for similar measurements with the Square Kilometre Array (SKA); (ii) an extinction free census of star formation and AGN activity out to z ∼ 1. In this paper we give an overview of the project including the science goals and multi-wavelength coverage before presenting the first data release. We have analysed around 400 hours of e-MERLIN data allowing us to create a Data Release 1 (DR1) mosaic of ∼ 0.26 deg 2 to the full depth. These observations have been supplemented with complementary radio observations from the Karl G. Jansky Very Large Array (VLA) and optical/near infra-red observations taken with the Subaru, Canada-France-Hawaii and Spitzer Telescopes. The main data product is a catalogue of 887 sources detected by the VLA, of which 395 are detected by e-MERLIN and 197 of these are resolved. We have investigated the size, flux and spectral index properties of these sources finding them compatible with previous studies. Preliminary photometric redshifts, and an assessment of galaxy shapes measured in the radio data, combined with a radio-optical cross-correlation technique probing cosmic shear in a supercluster environment, are presented in companion papers.

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Section: Ancillary Multi-wavelength Observations Of the Superclass Fieldsupporting

confidence: 58%

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

Battye¹,

Brown²,

Casey

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…(2016a) and Williams et al (2016) to correct for DI effects (see de Gasperin et al 2019 for a description of the latest version of this pipeline). The processing was performed on compute facilities that are local to the LOFAR long term archive sites to mitigate issues with downloading large quantities of data to local compute clusters (see Mechev et al 2018).…”

Section: Gmrt Data Reductionmentioning

confidence: 99%

Revived fossil plasma sources in galaxy clusters

Mandal

Intema

Weeren

et al. 2020

A&A

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It is well established that particle acceleration by shocks and turbulence in the intra-cluster medium can produce cluster-scale synchrotron emitting sources. However, the detailed physics of these particle acceleration processes is still not well understood. One of the main open questions is the role of fossil relativistic electrons that have been deposited in the intra-cluster medium by radio galaxies. These synchrotron-emitting electrons are very difficult to study, as their radiative life time is only tens of Myrs at GHz frequencies, and are therefore a relatively unexplored population. Despite the typical steep radio spectrum due to synchrotron losses, these fossil electrons are barely visible even at radio frequencies well below a GHz. However, when a pocket of fossil radio plasma is compressed, it boosts the visibility at sub-GHz frequencies, creating so-called radio phoenices. This compression can be the result of bulk motion and shocks in the ICM due to merger activity. In this paper, we demonstrate the discovery potential of low frequency radio sky surveys to find and study revived fossil plasma sources in galaxy clusters. We used the 150 MHz TGSS and 1.4 GHz NVSS sky surveys to identify candidate radio phoenices. A subset of three candidates were studied in detail using deep multi-band radio observations (LOFAR and GMRT), X-ray (Chandra or XMM-Newton) and archival optical observations. Two of the three sources are new discoveries. Using these observations, we identified common observational properties (radio morphology, ultra-steep spectrum, X-ray luminosity, dynamical state) that will enable us to identify this class of sources more easily, and helps to understand the physical origin of these sources.

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“…Aftewards, the calibration scheme and pipelines developed for LoTSS were applied (see Shimwell et al 2019 for more details). In particular, the PREFACTOR pipeline Williams et al 2016) and version v2.2-167 of the DDFacet pipeline 1 (see Tasse et al 2018;Tasse et al in prep. ) were used to perform direction-independent and dependent calibration, respectively, using the default parameters.…”

Section: Lofar Observations At 144 Mhz and Data Reductionmentioning

confidence: 99%

Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388

Brienza

Morganti

Harwood

et al. 2020

A&A

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Context. Restarted radio galaxies represent a unique tool for investigating the duty cycle of the jet activity in active galactic nuclei (AGN). The radio galaxy 3C388 has long been claimed to be a peculiar example of an AGN with multi-epoch activity because it shows a very sharp discontinuity in the GHz spectral index distribution of its lobes. Aims. We present here for the first time a spatially resolved study of the radio spectrum of 3C388 down to MHz frequencies aimed at investigating the radiative age of the source and constraining its duty cycle. Methods. We used new low-frequency observations at 144 MHz performed with the Low Frequency Array and at 350 MHz performed with the Very Large Array that we combined with archival data at higher frequencies (614, 1400, and 4850 MHz).Results. We find that the spectral indices in the lower frequency range, 144-614 MHz, have flatter values (α low ∼0.55-1.14) than those observed in the higher frequency range, 1400-4850 MHz, (α high ∼0.75-1.57), but they follow the same distribution across the lobes, with a systematic steepening towards the edges. However, the spectral shape throughout the source is not uniform and often deviates from standard models. This suggests that mixing of different particle populations occurs, although it remains difficult to understand whether this is caused by observational limitations (insufficient spatial resolution and/or projection effects) or by the intrinsic presence of multiple particle populations, which might be related to the two different outbursts.Conclusions. Using single-injection radiative models, we compute that the total source age is 80 Myr and that the duty cycle is about t on /t tot ∼ 60%, which is enough to prevent the intracluster medium from cooling, according to X-ray estimates. While to date the radio spectral distribution of 3C388 remains a rare case among radio galaxies, multi-frequency surveys performed with new-generation instruments will soon allow us to investigate whether more sources with the same characteristics exist.

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Social/Cultural Anthropology: On the Edge of the Forest: Cultural Adaptation and Cognitive Development in Central Africa. J. W. Berry, J. M. H. van de Koppel, C. Sénéchal, R. C. Annis, S. Bahuchet, L. L. Cavalli‐Sforza, and H. A. Witkin.

Cited by 23 publications

References 0 publications

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

Revived fossil plasma sources in galaxy clusters

Radio spectral properties and jet duty cycle in the restarted radio galaxy 3C388

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