The highest frequency detection of a radio relic : 16 GHz AMI observations of the 'Sausage' cluster

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters. © 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We observed the cluster CIZA J2242.8+5301 with the Arcminute Microkelvin Imager at 16 GHz and present the first high radio-frequency detection of diffuse, non-thermal cluster emission. This cluster hosts a variety of bright, extended, steep-spectrum synchrotron-emitting radio sources, associated with the intracluster medium, called radio relics. Most notably, the northern, Mpc-wide, narrow relic provides strong evidence for diffusive shock acceleration in clusters. We detect a puzzling, flat-spectrum, diffuse extension of the southern relic, which is not visible in the lower radio-frequency maps. The northern radio relic is unequivocally detected and measures an integrated flux of 1.2 ± 0.3 mJy. While the low-frequency (<2 GHz) spectrum of the northern relic is well represented by a power law, it clearly steepens towards 16 GHz. This result is inconsistent with diffusive shock acceleration predictions of ageing plasma behind a uniform shock front. The steepening could be caused by an inhomogeneous medium with temperature/density gradients or by lower acceleration efficiencies of high energy electrons. Further modelling is necessary to explain the observed spectrum.Peer reviewe

Reconciling drainage and receiving basin signatures of the Godavari River system

The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OC_(terr); 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OC_(terr) is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFAs), sedimentological properties (e.g. grain size, mineral surface area, etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e. mineral surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in the preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ^(13)C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more ^(13)C enriched carbon than the lower stream, resulting from the regional vegetation gradient and/or net balance between the upper (C_4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ^(14)C_(OC)) in deep soils and eroding riverbanks suggests these are likely sources of old or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. While changes in water flow and sediment transport resulting from recent dam construction have drastically impacted the flux, loci, and composition of OC exported from the modern Godavari basin, complicating reconciliation of modern-day river basin geochemistry with that recorded in continental margin sediments, such investigations provide important insights into climatic and anthropogenic controls on OC cycling and burial

Branched glycerol monoalkyl glycerol tetraethers (brGMGTs) and geochemical proxies in soils, SPM and riverbed sediments in the Godavari River basin (India)

Branched Glycerol Monoalkyl Glycerol Tetraethers (brGMGTs) in soils, suspended particulate matter (SPM) and riverbed sediments of the Godavari River basin (India), the largest river of peninsular India that is fed by the Southwest monsoon. Surface soils (0-10 cm) were collected near the Godavari River, and SPM (10-80 L, filtered over 0.7 μm GFF filters) and bulk and fine (≤63 μm) riverbed sediments were collected in a dry (February/March 2015) and wet season (July/August 2015). BrGMGT fractional abundances and concentrations were analysed using ultra high performance liquid chromatography-mass spectrometry. BrGMGT loadings were normalised to Mineral Surface Area (MSA data for soils and dry season sediments from Usman et al., 2018). %TN and C:N were measured in soils and sediments, %TOC was from Kirkels et al. (2021)

Branched glycerol dialkyl glycerol tetraethers, crenarchaeol and geochemical parameters in soils, SPM and riverbed sediments in the Godavari River basin (India)

The concentration and fractional abundance of branched Glycerol Dialkyl Glycerol Tetraethers (brGDGTs), including 5-methyl and 6-methyl isomers, were investigated in the soils, suspended particulate matter (SPM) and riverbed sediments of the Godavari River basin, the largest non-Himalayan river in India and fed by the Southwest monsoon. Surface soils (0-10 cm) were collected near the Godavari River, and SPM and riverbed sediments were collected in a dry (February/March) and wet season (July/August) in 2015. Crenarchaeol was measured, as well as pH, TOC, and soil and sediment geochemistry

Isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) lipids in soils, SPM, and riverbed sediments in the Godavari Basin (India)

The concentration and fractional abundance of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) were investigated in the soils, suspended particulate matter (SPM) and riverbed sediments of the Godavari River basin, the largest non-Himalayan river in India and fed by the Southwest monsoon. Surface soils (0-10 cm) were collected near the Godavari River, and SPM and riverbed sediments were collected in a dry (February/March) and wet season (July/August) in 2015

Physicochemical parameters and stable water isotopes in the Godavari River basin, India

This dataset contains physicochemical parameters (Electrical Conductivity, Temperature) and stable water isotope measurements of river surface waters and depth profiles in the Godavari River basin, India, in the pre-monsoon and monsoon season

Reconciling drainage and receiving basin signatures of the Godavari River system

The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OCterr; 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OCterr is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFAs), sedimentological properties (e.g. grain size, mineral surface area, etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e. mineral surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in the preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ13C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more 13C enriched carbon than the lower stream, resulting from the regional vegetation gradient and/or net balance between the upper (C4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ14COC) in deep soils and eroding riverbanks suggests these are likely sources of old or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. While changes in water flow and sediment transport resulting from recent dam construction have drastically impacted the flux, loci, and composition of OC exported from the modern Godavari basin, complicating reconciliation of modern-day river basin geochemistry with that recorded in continental margin sediments, such investigations provide important insights into climatic and anthropogenic controls on OC cycling and burial

Reconciling drainage and receiving basin signatures of the Godavari River system

The modern-day Godavari River transports large amounts of sediment (170 Tg per year) and terrestrial organic carbon (OCterr; 1.5 Tg per year) from peninsular India to the Bay of Bengal. The flux and nature of OCterr is considered to have varied in response to past climate and human forcing. In order to delineate the provenance and nature of organic matter (OM) exported by the fluvial system and establish links to sedimentary records accumulating on its adjacent continental margin, the stable and radiogenic isotopic composition of bulk OC, abundance and distribution of long-chain fatty acids (LCFAs), sedimentological properties (e.g. grain size, mineral surface area, etc.) of fluvial (riverbed and riverbank) sediments and soils from the Godavari basin were analysed and these characteristics were compared to those of a sediment core retrieved from the continental slope depocenter. Results show that river sediments from the upper catchment exhibit higher total organic carbon (TOC) contents than those from the lower part of the basin. The general relationship between TOC and sedimentological parameters (i.e. mineral surface area and grain size) of the sediments suggests that sediment mineralogy, largely driven by provenance, plays an important role in the stabilization of OM during transport along the river axis, and in the preservation of OM exported by the Godavari to the Bay of Bengal. The stable carbon isotopic (δ13C) characteristics of river sediments and soils indicate that the upper mainstream and its tributaries drain catchments exhibiting more 13C enriched carbon than the lower stream, resulting from the regional vegetation gradient and/or net balance between the upper (C4-dominated plants) and lower (C3-dominated plants) catchments. The radiocarbon contents of organic carbon (Δ14COC) in deep soils and eroding riverbanks suggests these are likely sources of old or pre-aged carbon to the Godavari River that increasingly dominates the late Holocene portion of the offshore sedimentary record. While changes in water flow and sediment transport resulting from recent dam construction have drastically impacted the flux, loci, and composition of OC exported from the modern Godavari basin, complicating reconciliation of modern-day river basin geochemistry with that recorded in continental margin sediments, such investigations provide important insights into climatic and anthropogenic controls on OC cycling and burial