VLBI observation of giant radio galaxy J1313+696 at 2.3/8.4 GHz

We report the result of VLBI observation of the giant radio galaxy J1313+696 (4C +69.15) at 2.3/8.4 GHz, only the core component of the giant radio galaxy was detected in the VLBI observation at the dual frequencies. The result shows a steep spectrum core with $\alpha=-0.82$ ($S \propto \nu^{\alpha}$) between 2.3 GHz and 8.4 GHz. The steep spectrum core may be a sign of renewed activity. Considering also the upper limit flux density of 2.0 mJy at 0.6 GHz from Konar et al. 2004 the core has a GHz-peaked spectrum, implying that the core is compact and absorbed. Further high resolution VLBI observations are needed to identify if the steep spectrum core is consisting of a core and steep spectrum jet.Comment: 3 pages, 3 figure

CO(1-0) detection of molecular gas in the massive Spiderweb Galaxy (z=2)

The high-redshift radio galaxy MRC 1138−262 (‘Spiderweb Galaxy’; z = 2.16) is one of the most massive systems in the early Universe and surrounded by a dense ‘web’ of proto-cluster galaxies. Using the Australia Telescope Compact Array, we detected CO(1–0) emission from cold molecular gas – the raw ingredient for star formation – across the Spiderweb Galaxy. We infer a molecular gas mass of MH2 = 6 × 1010 M⊙ (for MH2/L′CO = 0.8). While the bulk of the molecular gas coincides with the central radio galaxy, there are indications that a substantial fraction of this gas is associated with satellite galaxies or spread across the intergalactic medium on scales of tens of kpc. In addition, we tentatively detect CO(1–0) in the star-forming proto-cluster galaxy HAE 229, 250 kpc to the West. Our observations are consistent with the fact that the Spiderweb Galaxy is building up its stellar mass through a massive burst of widespread star formation. At maximum star formation efficiency, the molecular gas will be able to sustain the current star formation rate (SFR ≈ 1400 M⊙ yr−1, as traced by Seymour et al.) for about 40 Myr. This is similar to the estimated typical lifetime of a major starburst event in infrared luminous merger systems

Barbell-shaped giant radio galaxy with ~100 kpc kink in the jet

Galaxie

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

Integrated global assessment of the natural forest carbon potential

Forests are a substantial terrestrial carbon sink, but anthropogenic changes in land use and climate have considerably reduced the scale of this system1. Remote-sensing estimates to quantify carbon losses from global forests2,3,4,5 are characterized by considerable uncertainty and we lack a comprehensive ground-sourced evaluation to benchmark these estimates. Here we combine several ground-sourced6 and satellite-derived approaches2,7,8 to evaluate the scale of the global forest carbon potential outside agricultural and urban lands. Despite regional variation, the predictions demonstrated remarkable consistency at a global scale, with only a 12% difference between the ground-sourced and satellite-derived estimates. At present, global forest carbon storage is markedly under the natural potential, with a total deficit of 226 Gt (model range = 151–363 Gt) in areas with low human footprint. Most (61%, 139 Gt C) of this potential is in areas with existing forests, in which ecosystem protection can allow forests to recover to maturity. The remaining 39% (87 Gt C) of potential lies in regions in which forests have been removed or fragmented. Although forests cannot be a substitute for emissions reductions, our results support the idea2,3,9 that the conservation, restoration and sustainable management of diverse forests offer valuable contributions to meeting global climate and biodiversity targets

A 325-MHz GMRT survey of the Herschel-ATLAS/GAMA fields

We describe a 325-MHz survey, undertaken with the Giant Metrewave Radio Telescope (GMRT), which covers a large part of the three equatorial fields at 9, 12 and 14.5 h of right ascension from the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) in the area also covered by the Galaxy AndMass Assembly (GAMA) survey. The full data set, after some observed pointings were removed during thedata reduction process, comprises 212 GMRT pointings covering ~90 deg of sky. We have imaged and catalogued the data using a pipeline that automates the process of flagging, calibration, self-calibration and source detection for each of the survey pointings. The resulting images have resolutions of between 14 and 24 arcsec and minimum rms noise (away from bright sources) of ~1 mJy beam, and the catalogue contains 5263 sources brighter than 5Σ. We investigate the spectral indices of GMRT sources which are also detected at 1.4 GHz and find them to agree broadly with previously published results; there is no evidence for any flattening of the radio spectral index below S = 10 mJy. This work addsto the large amount of available optical and infrared data in the H-ATLAS equatorial fields and will facilitate further study of the low-frequency radio properties of star formation and AGN activity in galaxies out to z ~ 1.Peer reviewe

Extended radio jets in the high-redshift quasars 3C 9 and 280.1

Wetensch. publicatieFaculteit der Wiskunde en Natuurwetenschappe

HI absorption towards low luminosity radio-loud AGNs of different accretion modes and WISE colours

<p>HI absorption studies of active galaxies enable us to probe their circumnuclear regions and the general interstellar medium, and study the supply of gas which may trigger the nuclear activity. We investigated the detection rate of HI absorption on the nature of radio galaxies based on their emission-line spectra, nature of the host galaxies based on the WISE colours and their radio structure, which may help understand the different accretion modes. The highest detection rate of HI absorption is found in the `late-type' galaxies with WISE infrared colours W2-W3 > 2, which is typical of gas-rich systems, along with a compact radio structure. Almost all the high-excitation radio galaxies (HERGs) in our sample have W2-W3 > 2. The HI detection rate for low-excitation radio galaxies (LERGs) with W2-W3 > 2 and compact radio structure is high (~ 71 %). This is similar to compact HERGs with W2-W3 > 2 where, although the numbers are small, all three sources are detected with HI absorption. In HERGs, compact radio structure in the nuclear or circumnuclear region could give rise to absorption by gas in the dusty torus in addition to gas in the interstellar medium. However, higher specific star formation rate (sSFR) for the LERGs with W2-W3 > 2 suggests that HI absorption may be largely due to star-forming gas in their hosts.</p

Radio Properties of a ‘Quarter Jansky Sample’ of Extragalactic Sources,Defined at 408 Mhz

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