Hintze Centre for Astrophysical Surveys

Abstract:

We announce the discovery of an extended emission-line region associated with a high-redshift type-2 quasi-stellar object (QSO). The halo, which was discovered in our new wide-field narrow-band survey, resides at z = 2.85 in the Spitzer First Look Survey region and is extended over ∼80 kpc. Deep very long baseline interferometry (VLBI) observations imply that approximately 50 per cent of the radio emission is extended on scales >200 pc. The inferred active galactic nuclei (AGN) luminosity is sufficient to ionize the extended halo, and the optical emission is consistent with being triggered coevally with the radio source. The Lyα halo is as luminous as those found around high-redshift radio galaxies; however, the active nucleus is several orders of magnitude less luminous at radio wavelengths than those Fanarof-Riley type II (FRIIs) more commonly associated with extended emission-line regions. AMS05 appears to be a high-redshift analogue to the radio-quiet quasar E1821+643 which is core dominated, but which also exhibits extended Fanarof-Riley type I (FRI)-like structure and contains an optically powerful AGN. We also find evidence for more quiescent kinematics in the Lyα emission line in the outer regions of the halo, reminiscent of the haloes around the more powerful FRIIs. The optical to mid-infrared spectral energy distribution is well described by a combination of an obscured QSO (Lbol ∼ 3.4 ± 0.2 × 1013 L⊙) and a 1.4 Gyr old simple stellar population with mass ∼3.9 ± 0.3 × 10 11 M⊙. © 2009 RAS.

Abstract:

We present a preliminary analysis of the H I properties of early-type galaxies in the ATLAS3D sample. Using WSRT data for ~100 galaxies outside the Virgo cluster and data from the Alfalfa project for galaxies inside Virgo, we discuss the dependence of H I properties on environment. We detect H I in about half of the galaxies outside Virgo. For these systems, the H I morphology and kinematics change as a function of environment, going from regular, rotating systems around “isolated” galaxies to progressively more disturbed structures for galaxies with neighbours or in groups. In denser environment, inside Virgo, nearly none of the galaxies contains H I. We discuss future work in this field which will be enabled by next-generation, pre-SKA radio instruments. We present a simulated Apertif H I observation of an ATLAS3D early-type galaxy, showing how its appearance and detection level vary as a function of redshift.

Abstract:

We report an anticorrelation between continuum luminosity and the equivalent width (EW) of the Hα emission line in X-ray binary systems. The effect is evident both in a universal monotonic increase in Hα EW with time following outbursts, as systems fade, and in a comparison between measured EWs and contemporaneous X-ray measurements. The effect is most clear for black hole binaries in the low/hard X-ray state, which is prevalent at X-ray luminosities below ∼1 per cent of the Eddington luminosity. We do not find strong evidence for significant changes in line profiles across accretion state changes, but this is hampered by a lack of good data at such times. The observed anticorrelation, highly significant for black hole binaries, is only marginally so for neutron star systems, for which there are far less data. Comparison with previously established correlations between optical and X-ray luminosity suggests that the line luminosity is falling as the X-ray and optical luminosities drop, but not as fast, approximately, as LHα ∝ L∼0.4X ∝ L∼0.7opt. We briefly discuss possible origins for such an effect, including the optical depth, form of the irradiating spectrum and geometry of the accretion flow. Further refinement of the relation in the future may allow measurements of Hα EW to be used to estimate the luminosity of, and hence the distance to, X-ray binary systems. Beyond this, further progress will require a better sample of spectrophotometric data. © 2009 RAS.