The Square Kilometre Array (SKA)

Abstract:

We report the discovery of multi-scale X-ray jets from the accreting neutron star X-ray binary, Circinus X-1. The bipolar outflows show wide opening angles and are spatially coincident with the radio jets seen in new highresolution radio images of the region. The morphology of the emission regions suggests that the jets from Circinus X-1 are running into a terminal shock with the interstellar medium, as is seen in powerful radio galaxies. This and other observations indicate that the jets have a wide opening angle, suggesting that the jets are either not very well collimated or precessing. We interpret the spectra from the shocks as cooled synchrotron emission and derive a cooling age of ∼1600 yr. This allows us to constrain the jet power to be 3×1035 erg s-1 ≲ Pjet ≲ 2×1037 erg s-1, making this one of a few microquasars with a direct measurement of its jet power and the only known microquasar that exhibits stationary large-scale X-ray emission. © 2010. The American Astronomical Society. All rights reserved.

Abstract:

We present an analysis of observations of the doubly-lensed double hotspot in the giant radio galaxy J0816+5003 from MERLIN, MDM, WIYN, WHT, UKIRT and the VLA. The images of the two hotspot components span a factor of two in radius on one side of the lensing galaxy at impact parameters of less than 500pc. Hence we measure the slope of the lensing potential over a large range in radius, made possible by significant improvement in the accuracy of registration of the radio and optical frame and higher resolution imaging data than previously available. We also infer the lens and source redshifts to be 0.332 and > 1 respectively. Purely on the basis of lens modelling, and independently of stellar velocity dispersion measurements, we find the potential to be very close to isothermal.

Abstract:

The Very Small Array (VSA) has been used to survey the l = 27 to 46 deg, |b|<4 deg region of the Galactic plane at a resolution of 13 arcmin. The survey consists of 44 pointings of the VSA, each with a r.m.s. sensitivity of ~90 mJy/beam. These data are combined in a mosaic to produce a map of the area. The majority of the sources within the map are HII regions. We investigated anomalous radio emission from the warm dust in 9 HII regions of the survey by making spectra extending from GHz frequencies to the FIR IRAS frequencies. Acillary radio data at 1.4, 2.7, 4.85, 8.35, 10.55, 14.35 and 94 GHz in addition to the 100, 60, 25 and 12 micron IRAS bands were used to construct the spectra. From each spectrum the free-free, thermal dust and anomalous dust emission were determined for each HII region. The mean ratio of 33 GHz anomalous flux density to FIR 100 micron flux density for the 9 selected HII regions was 1.10 +/-0.21x10^(-4). When combined with 6 HII regions previously observed with the VSA and the CBI, the anomalous emission from warm dust in HII regions is detected with a 33 GHz emissivity of 4.65 +/- 0.4 micro K/ (MJy/sr) at 11.5{\sigma}. The anomalous radio emission in HII regions is on average 41+/-10 per cent of the radio continuum at 33 GHz.

Abstract:

The Very Small Array (VSA) has been used to survey the ℓ∼ 27° to forumla region of the Galactic plane at a resolution of 13 arcmin. This ℓ-range covers a section through the Local, Sagittarius and the Cetus spiral arms. The survey consists of 44 pointings of the VSA, each with an rms sensitivity of ∼90 mJy beam⁻¹. These data are combined in a mosaic to produce a map of the area. The majority of the sources within the map are H II regions.

The main aim of the programme was to investigate the anomalous radio emission from the warm dust in individual H II regions of the survey. This programme required making a spectrum extending from GHz frequencies to the far-infrared (FIR) IRAS frequencies for each of nine strong sources selected to lie in unconfused areas. It was necessary to process each of the frequency maps with the same u, v coverage as was used for the VSA 33 GHz observations. The additional radio data were at 1.4, 2.7, 4.85, 8.35, 10.55, 14.35 and 94 GHz in addition to the 100, 60, 25 and 12 μm IRAS bands. From each spectrum the free–free, thermal dust and anomalous dust emission were determined for each H II region. The mean ratio of 33 GHz anomalous flux density to FIR 100 μm flux density for the nine selected H II regions was ΔS(33 GHz)/S(100 μm) = 1.10 ± 0.21 × 10⁻⁴. When combined with six H II regions previously observed with the VSA and the Cosmic Background Imager, the anomalous emission from warm dust in H II regions is detected with a 33 GHz emissivity of 4.65 ± 0.40 μK (MJy sr−1)−1 (11.5σ). This level of anomalous emission is 0.3 to 0.5 of that detected in cool dust clouds.

A radio spectrum of the H II region anomalous emission covering GHz frequencies is constructed. It has the shape expected for spinning dust composed of very small grains. The anomalous radio emission in H II regions is on average 41 ± 10 per cent of the radio continuum at 33 GHz. Another result is that the excess (i.e. non-free–free) emission from H II regions at 94 GHz correlates strongly with the 100 μm emission; it is also inversely correlated with the dust temperature. Both these latter results are as expected for very large grain dust emission. The anomalous emission on the other hand is expected to originate in very small spinning grains and correlates more closely with the 25 μm emission.