We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Images Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9 h , 12 h and 14.5 h ). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-µm luminosity with respect to radio-quiet quasars with the same optical luminosites. Even if we use a two-temperature grey-body model to describe the FIR data, the FIR luminosity excess remains at lower optical luminosities. These results suggest that powerful radio jets are associated with star formation especially at lower accretion rates.

In order to understand the role of radio-quiet quasars (RQQs) in galaxy evolution, we must determine the relative levels of accretion and star-formation activity within these objects. Previous work at low radio flux-densities has shown that accretion makes a significant contribution to the total radio emission, in contrast with other quasar studies that suggest star formation dominates. To investigate, we use 70 RQQs from the Spitzer-Herschel Active Galaxy Survey. These quasars are all at z ∼ 1, thereby minimising evolutionary effects, and have been selected to span a factor of ∼ 100 in optical luminosity, so that the luminosity dependence of their properties can be studied. We have imaged the sample using the Karl G. Jansky Very Large Array (JVLA), whose high sensitivity results in 35 RQQs being detected above 2 σ. This radio dataset is combined with far-infrared luminosities derived from grey-body fitting to Herschel photometry. By exploiting the far-infrared-radio correlation observed for starforming galaxies, and comparing two independent estimates of the star-formation rate, we show that star formation alone is not sufficient to explain the total radio emission. Considering RQQs above a 2-σ detection level in both the radio and the far-infrared, 92 per cent are accretion-dominated, and the accretion process accounts for 80 per cent of the radio luminosity when summed across the objects. The radio emission connected with accretion appears to be correlated with the optical luminosity of the RQQ, whilst a weaker luminosity-dependence is evident for the radio emission connected with star formation.

We present results from an analysis of the largest high-redshift (z > 3) X-ray-selected active galactic nucleus (AGN) sample to date, combining the Chandra C-COSMOS and ChaMP surveys and doubling the previous samples. The sample comprises 209 X-ray-detected AGN, over a wide range of rest frame 2-10 keV luminosities log L X = 43.3 − 46.0 erg s −1 . X-ray hardness rates show that ∼39% of the sources are highly obscured, N H > 10 22 cm −2 , in agreement with the ∼37% of type-2 AGN found in our sample based on their optical classification. For ∼26% of objects have mismatched optical and X-ray classifications. Using the 1/V max method, we confirm that the comoving space density of all luminosity ranges of AGNs decreases with redshift above z > 3 and up to z ∼ 7. With a significant sample of AGN (N = 27) at z > 4, it is found that both source number counts in the 0.5 -2 keV band and comoving space density are consistent with the expectation of a luminosity dependent density evolution (LDDE) model at all redshifts, while they exclude the luminosity and density evolution (LADE) model. The measured comoving space density of type-1 and type-2 AGN shows a constant ratio between the two types at z > 3. Our results for both AGN types at these redshifts are consistent with the expectations of LDDE model.

We investigate the [O II] emission-line properties of 18 508 quasars at z < 1.6 drawn from the Sloan Digital Sky Survey (SDSS) quasar sample. The quasar sample has been separated into 1692 radio-loud and 16 816 radio-quiet quasars (hereafter RLQs and RQQs) matched in both redshift and i -band absolute magnitude.We use the [O II]λ3726 + 3729 line as an indicator of star formation. Based on these measurements we find evidence that star formation activity is higher in the RLQ population. The mean equivalent widths (EW) for [O II] are EW([O II]) RL = 7.80 ± 0.30 Å and EW([O II]) RQ = 4.77 ± 0.06 Å for the RLQ and RQQ samples, respectively. The mean [O II] luminosities are log 10 [L([O II]) RL /W] = 34.31 ± 0.01 and log 10 [L([O II]) RQ /W] = 34.192 ± 0.004 for the samples of RLQs and RQQs, respectively. Finally, to overcome possible biases in the EW measurements due to the continuum emission below the [O II] line being contaminated by young stars in the host galaxy, we use the ratio of the [O II] luminosity to rest-frame i -band luminosity; in this case, we find for the RLQs log 10 [L([O II]) RL /L opt ] = −3.89 ± 0.01 and log 10 [L([O II]) RQ /L opt ] = −4.011 ± 0.004 for RQQs. However the results depend upon the optical luminosity of the quasar. RLQs and RQQs with the same high optical luminosity log 10 (L opt /W) > 38.6 tend to have the same level of [O II] emission. On the other hand, at lower optical luminosities log 10 (L opt /W) < 38.6, there is a clear [O II] emission excess for the RLQs. As an additional check of our results we use the [O III] emission line as a tracer of the bolometric accretion luminosity, instead of the i -band absolute magnitude, and we obtain similar results.Radio jets appear to be the main reason for the [O II] emission excess in the case of RLQs. In contrast, we suggest active galactic nuclei feedback ensures that the two populations acquire the same [O II] emission at higher optical luminosities.

Striking similarities have been seen between accretion signatures of Galactic X-ray binary (XRB) systems and active galactic nuclei (AGN). XRB spectral states show a V-shaped correlation between X-ray spectral hardness and Eddington ratio as they vary, and some AGN samples reveal a similar trend, implying analogous processes at vastly larger masses and timescales. To further investigate the analogies, we have matched 617 sources from the Chandra Source Catalog to SDSS spectroscopy, and uniformly measured both X-ray and optical spectral characteristics across a broad range of AGN and galaxy types. We provide useful tabulations of X-ray spectral slope for broad and narrow line AGN, star-forming and passive galaxies and composite systems, also updating relationships between optical (Hα and [O III]) line emission and X-ray luminosity. We further fit broadband spectral energy distributions with a variety of templates to estimate bolometric luminosity. Our results confirm a significant trend in AGN between X-ray spectral hardness and Eddington ratio expressed in X-ray luminosity, albeit with significant dispersion. The trend is not significant when expressed in the full bolometric or template-estimated AGN luminosity. We also confirm a relationship between the Xray/optical spectral slope α ox and Eddington ratio, but it may not follow the trend predicted by analogy with XRB accretion states.

We present an analysis of XMM-Newton spectra of the low-redshift quasar IRAS 13349+2438. The RGS spectrum shows a large number of absorption lines from two zones of warm absorption, with velocities of ∼ −600 km s −1 , as noted by previous authors. Additionally, we find robust evidence from multiple Lyα absorption lines for a previously undiscovered ultra-fast zone of absorption, with an outflow velocity of -0.13±0.01c. The warm absorbers and ultra-fast outflow have similar mass outflow rates, around 40% of the Eddington accretion rate, but the kinetic power is dominated by the high velocity gas, which has a power of ∼ 4% of the Eddington luminosity.

Several studies support the existence of a link between the AGN and star formation activity. Radio jets have been argued to be an ideal mechanism for direct interaction between the AGN and the host galaxy. A drawback of previous surveys of AGN is that they are fundamentally limited by the degeneracy between redshift and luminosity in flux-density limited samples. To overcome this limitation, we present far-infrared Herschel observations of 74 radio-loud quasars (RLQs), 72 radio-quiet quasars (RQQs) and 27 radio galaxies (RGs), selected at 0.9 < z < 1.1 which span over two decades in optical luminosity. By decoupling luminosity from evolutionary effects, we investigate how the star formation rate (SFR) depends on AGN luminosity, radio-loudness and orientation. We find that: 1) the SFR shows a weak correlation with the bolometric luminosity for all AGN sub-samples, 2) the RLQs show a SFR excess of about a factor of 1.4 compared to the RQQs, matched in terms of black hole mass and bolometric luminosity, suggesting that either positive radio-jet feedback or radio AGN triggering are linked to star-formation triggering and 3) RGs have lower SFRs by a factor of 2.5 than the RLQ sub-sample with the same BH mass and bolometric luminosity. We suggest that there is some jet power threshold at which radio-jet feedback switches from enhancing star formation (by compressing gas) to suppressing it (by ejecting gas). This threshold depends on both galaxy mass and jet power.

We report the discovery of a kiloparsec-scale triple supermassive black hole system at z = 0.256: SDSS J1056+5516, discovered by our systematic search for binary quasars. The system contains three strong emission-line nuclei, which are offset by < 250 km s −1 and by 15-18 kpc in projected separation, suggesting that the nuclei belong to the same physical structure. The system includes a tidal arm feature spanning ∼ 100 kpc in projected distance at the systems' redshift, inhabiting an ongoing or recent galaxy merger. Based on our results, such a structure can only satisfy one of the three scenarios; a triple supermasive black hole (SMBH) interacting system, a triple AGN, or a recoiling SMBH. Each of these scenarios is unique for our understanding of the hierarchical growth of galaxies, AGN triggering, and gravitational waves.