Hintze Centre for Astrophysical Surveys

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.

Abstract:

We present Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) and radio follow-up observations of two Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS)-detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81), we detect [Oiii]88μm and [Cii]158μm lines at a signal-to-noise ratio of ~5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0-005343 (SDP.130). Currently, SDP.81 is the faintest submillimetre galaxy with positive line detections with the FTS, with continuum flux just below 200mJy in the 200-600μm wavelength range. The derived redshift of SDP.81 from the two detections isz= 3.043 ± 0.012, in agreement with ground-based CO measurements. This is the first detection byHerschelof the [Oiii]88μm line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photodissociation region (PDR) models with different physical conditions, we derive the PDR cloud densityn≈ 2000cm-3 and the far-ultraviolet ionizing radiation fieldG0≈ 200 (in units of the Habing field - the local Galactic interstellar radiation field of 1.6 × 10-6 W m-2). Using the CO-derived molecular mass and the PDR properties, we estimate the effective radius of the emitting region to be 500-700pc. These characteristics are typical for star-forming, high-redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local far-infrared/radio (FIR/radio) correlation, which hints that some fraction of the radio emission is coming from an active galactic nucleus (AGN). The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33 per cent. These indications, together with the high [Oiii]/FIR ratio and the upper limit of [Oi]63μm/[Cii]158μm, suggest that some fraction of the ionizing radiation is likely to originate from the AGN. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Abstract:

In recent years, much effort has been devoted to unravelling the connection between the accretion flow and the jets in accreting compact objects. In the present work, we report new constraints on these issues, through the long-term study of the radio and X-ray behaviour of the black hole candidate H1743-322. This source is known to be one of the 'outliers' of the universal radio/X-ray correlation, i.e. a group of accreting stellar-mass black holes displaying fainter radio emission for a given X-ray luminosity than expected from the correlation. Our study shows that the radio and X-ray emission of H1743-322 are strongly correlated at high luminosity in the hard spectral state. However, this correlation is unusually steep for a black hole X-ray binary: b~ 1.4 (with Lradio∝LbX). Below a critical luminosity, the correlation becomes shallower until it rejoins the standard correlation with b~ 0.6. Based on these results, we first show that the steep correlation can be explained if the inner accretion flow is radiatively efficient during the hard state, in contrast to what is usually assumed for black hole X-ray binaries in this spectral state. The transition between the steep and the standard correlation would therefore reflect a change from a radiatively efficient to a radiatively inefficient accretion flow. Finally, we investigate the possibility that the discrepancy between 'outliers' and 'standard' black holes arises from the outflow properties rather than from the accretion flow. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.