Hintze Centre for Astrophysical Surveys

Abstract:

The diffuse cm wave IR-correlated signal, the 'anomalous' CMB foreground, is thought to arise in the dust in cirrus clouds. We present Cosmic Background Imager (CBI) cm wave data of two translucent clouds, ζ Oph and LDN 1780 with the aim of characterizing the anomalous emission in the translucent cloud environment. In ζ Oph, the measured brightness at 31GHz is 2.4σ higher than an extrapolation from 5-GHz measurements assuming a free-free spectrum on 8 arcmin scales. The SED of this cloud on angular scales of 1° is dominated by free-free emission in the cm range. In LDN 1780 we detected a 3σ excess in the SED on angular scales of 1° that can be fitted using a spinning dust model. In this cloud, there is a spatial correlation between the CBI data and IR images, which trace dust. The correlation is better with near-IR templates (IRAS 12 and 25μm) than with IRAS 100μm, which suggests a very small grain origin for the emission at 31GHz. We calculated the 31-GHz emissivities in both clouds. They are similar and have intermediate values between that of cirrus clouds and dark clouds. Nevertheless, we found an indication of an inverse relationship between emissivity and column density, which further supports the VSGs origin for the cm emission since the proportion of big relative to small grains is smaller in diffuse clouds. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Abstract:

We use new mid-infrared (mid-IR) photometry from the Spitzer Space Telescope to study the relations between low-frequency radio luminosity density, mid-IR (12μm rest frame) luminosity and optical emission-line ([Oii]) luminosity L]Oii], for a complete sample of z∼ 1 radio galaxies from the 3CRR, 6CE, 6C*, 7CRS and TOOT00 surveys. The narrow redshift span of our sample (0.9 < z < 1.1) means that it is unbiased to evolutionary effects. We find evidence that these three quantities are positively correlated. The scaling between and L[Oii] is similar to that seen in other active galactic nuclei samples, consistent with both and L[Oii] tracing accretion rate. We show that the positive correlation between and implies that there is a genuine lack of objects with low values of at high values of Given that traces accretion rate, while traces jet power, this can be understood in terms of a minimum accretion rate being necessary to produce a given jet power. This implies that there is a maximum efficiency with which accreted energy can be chanelled into jet power and this efficiency is of the order of unity. © 2010 The Authors Monthly Notices of the Royal Astronomical Society © 2010 RAS.

Abstract:

We describe the current status of the HARMONI instrument design, which will form the basis for the first-light integral field spectrograph on the European Extremely Large Telescope. We review the phase A design, and highlight current on-going work to evolve the design in-line changing telescope requirements and lessons learned during the Phase A work. We also outline the key science drivers for the instrument, and describe briefly the requirements for the laser tomographic adaptive optics system which is expected to feed HARMONI.

Abstract:

LOFT (Large area Observatory For x-ray Timing) is an innovative mission concept for the next generation of X-ray experiments, submitted to the ESA Call for Medium size missions “M3”. Recent developments in the field of Silicon detectors allowed us to design a realistic observatory devoted to X-ray timing studies with an effective area above 10 m2, operating in the energy range 2-30 keV with an energy resolution of ∼250 eV. Such an exceedingly large area (20 times that of RXTE/PCA), with a time resolution better than 10 µs, will enable unprecedently fast and accurate time variability studies related to accreting collapsed objects (e.g. fast coherent pulsations and QPOs). The scientific payload is complemented by a coded-mask wide field monitor based on similar detectors. In this paper we present the mission concept, the payload design and the expected performances.

Abstract:

The coupling between accretion processes and ejection mechanisms in accreting black holes in binary systems can be investigated by empirical relations between the X-ray/radio and X-ray/optical-infrared luminosities. These correlations are valid over several orders of magnitude and were initially thought to be universal. However, recently, many black hole binaries have been found to produce jets that, given certain accretion-powered luminosities, are fainter than expected from the earlier correlations. This shows that black holes with similar accretion flows can produce a broad range of outflows in power, suggesting that some other parameters or factors might be tuning the accretion-ejection coupling. Recent work has already shown that this jet power does not correlate with the reported black hole spin measurements. Here we discuss whether fixed parameters of the binary system (orbital period, disc size, inclination), as well as the properties of the outburst, produce any effect on the energy output in the jet. No obvious dependence is found. We also show that there is no systematic variation in the slope of the radio-X-ray correlation with normalization. We define a jet-toy model in which the bulk Lorentz factor becomes larger than ̃1 above ̃0.1 per cent of the Eddington luminosity. With this model, if we assume random inclination angles which result in highly variable boosting at large Eddington ratios, we are able to reproduce qualitatively the scatter of the X-ray-radio correlation and the 'radio-quiet' population. However, the model seems to be at odds with some other observed properties of the systems. We also compare the 'radio-quiet' black holes with the neutron stars. We show that if a mass correction from the Fundamental Plane is applied, the possibility that they are statistically indistinguishable in the X-ray-radio plane cannot be completely ruled out. This result suggests that some of the outliers could actually be neutron stars or that the disc-jet coupling in the 'radio-quiet' black holes is more similar to the one in neutron stars. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.