We present the results from a survey for 12 CO emission in 40 luminous sub-millimetre galaxies (SMGs), with 850-µm fluxes of S 850µm = 4 − 20 mJy, conducted with the Plateau de Bure Interferometer. We detect 12 CO emission in 32 SMGs at z ∼ 1.2 -4.1, including 16 SMGs not previously published. Using multiple 12 CO line (J up = 2-7) observations, we derive a median spectral line energy distribution for luminous SMGs and use this to estimate a mean gas mass of (5.3 ± 1.0) × 10 10 M . We report the discovery of a fundamental relationship between 12 CO FWHM and 12 CO line luminosity in high-redshift starbursts, which we interpret as a natural consequence of the baryon-dominated dynamics within the regions probed by our observations. We use far-infrared luminosities to assess the star-formation efficiency in our SMGs, finding a steepening of the L CO -L FIR relation as a function of increasing 12 CO J up transition. We derive dynamical masses and molecular gas masses, and use these to determine the redshift evolution of the gas content of SMGs, finding that they do not appear to be significantly more gas rich than less vigorously star-forming galaxies at high redshifts. Finally, we collate X-ray observations, and study the interdependence of gas and dynamical properties of SMGs with their AGN activity and supermassive black hole masses (M BH ), finding that SMGs lie significantly below the local M BH -σ relation. We conclude that SMGs represent a class of massive, gas-rich ultraluminous galaxies with somewhat heterogeneous properties, ranging from starbursting disc-like systems with L∼ 10 12 L , to the most highly star-forming mergers in the Universe.

We present integral field spectroscopy observations, covering the [O III] λλ4959, 5007 emission-line doublet of eight high-redshift (z = 1.4-3.4) ultraluminous infrared galaxies (ULIRGs) that host active galactic nucleus (AGN) activity, including known submillimetre luminous galaxies. The targets have moderate radio luminosities that are typical of high-redshift ULIRGs (L 1.4 GHz = 10 24 -10 25 W Hz −1 ) and therefore are not radio-loud AGNs. We decouple kinematic components due to the galaxy dynamics and mergers from those due to outflows. We find evidence in the four most luminous systems (L [O III] 10 43 erg s −1 ) for the signatures of large-scale energetic outflows: extremely broad [O III] emission (full width at half-maximum ≈ 700-1400 km s −1 ) across ≈4-15 kpc, with high velocity offsets from the systemic redshifts (up to ≈850 km s −1 ). The four less luminous systems have lower quality data displaying weaker evidence for spatially extended outflows. We estimate that these outflows are potentially depositing energy into their host galaxies at considerable rates (Ė ≈ 10 43 -10 45 erg s −1 ); however, due to the lack of constraints on the density of the outflowing material and the structure of the outflow, these estimates should be taken as illustrative only. Based on the measured maximum velocities (v max ≈ 400-1400 km s −1 ) the outflows observed are likely to unbind some fraction of the gas from their host galaxies, but are unlikely to completely remove gas from the galaxy haloes. By using a combination of energetic arguments and a comparison to ULIRGs without clear evidence for AGN activity, we show that the AGN activity could be the dominant power source for driving all of the observed outflows, although star formation may also play a significant role in some of the sources.

We present a new sample of purely near-infrared-selected K Vega < 16.5 [K AB < 18.4] extremely red [(J − K) Vega > 2.5] quasar candidates at z ∼ 2 from 900 deg 2 of data in the UKIDSS Large Area Survey (LAS). Five of these are spectroscopically confirmed to be heavily reddened type 1 active galactic nuclei (AGN) with broad emission lines bringing our total sample of reddened quasars from the UKIDSS-LAS to 12 at z = 1.4-2.7. At these redshifts, Hα (6563 Å) is in the K band. However, the mean Hα equivalent width of the reddened quasars is only 10 per cent larger than that of the optically selected population and cannot explain the extreme colours. Instead, dust extinction of A V ∼ 2-6 mag is required to reproduce the continuum colours of our sources. This is comparable to the dust extinctions seen in submillimetre galaxies at similar redshifts. We argue that the AGN are likely being observed in a relatively short-lived breakout phase when they are expelling gas and dust following a massive starburst, subsequently turning into UV-luminous quasars. Some of our quasars show direct evidence for strong outflows (v ∼ 800-1000 km s −1 ) affecting the Hα line consistent with this scenario. We predict that a larger fraction of reddened quasar hosts are likely to be submillimetre bright compared to the UV-luminous quasar population. We use our sample to place new constraints on the fraction of obscured type 1 AGN likely to be missed in optical surveys. Taken at face value our findings suggest that the obscured fraction depends on quasar luminosity. The space density of obscured quasars is approximately five times that inferred for UV-bright quasars from the Sloan Digital Sky Survey (SDSS) luminosity function at M i < −30 but seems to drop at lower luminosities even accounting for various sources of incompleteness in our sample. We find that at M i ∼ −28 for example, this fraction is unlikely to be larger than ∼20 per cent although these fractions are highly uncertain at present due to the small size of our sample. A deeper K-band survey for highly obscured quasars is clearly needed to test this hypothesis fully and is now becoming possible with new sensitive all-sky infrared surveys such as the VISTA Hemisphere Survey and the Wide Infrared Survey Explorer (WISE) All Sky Survey.

We present new [CI](1-0) and 12 CO(4-3) Plateau de Bure Interferometer (PdBI) observations of five Sub-Millimeter Galaxies (SMGs) and combine these with all available [CI](1-0) literature detections in SMGs to probe the gas distribution within a sample of 14 systems. We explore the [CI](1-0) properties of the SMG population, particularly investigating the ratio of the [CI](1-0) luminosity to various 12 CO transition and far-infrared luminosities. We find that the SMGs with new observations extend the spread of L [CI](1−0) /L FIR to much higher values than found before, with our complete sample providing a good representation of the diverse z > 2 SMG population. We compare the line ratios to the outputs of photodissociation region (PDR) models to constrain the physical conditions in the interstellar medium (ISM) of the SMGs, finding an average density of log(n/cm −3 ) = 4.3 ± 0.2 and an average radiation field (in terms of the local field value, G 0 ) of log(G 0 ) = 3.9 ± 0.4. Overall, we find the SMGs are most comparable to local ULIRGs in G 0 and n, however a significant tail of 5 of the 14 SMGs are likely best compared to less compact, local starburst galaxies, providing new evidence that many SMGs have extended star formation distributions and are therefore not simply scaled up versions of local ULIRGs. We derive the ISM properties of a sample of quasars also finding that they have higher densities and radiation fields on average than the SMGs, consistent with the more extreme local ULIRGs, and reinforcing their interpretation as transition objects. We explore the limitations of using simple PDR models to understand [CI], which may be concomitant with the bulk H 2 mass rather than PDR-distributed. We therefore also assess [CI] as a tracer of H 2 , finding that for our sample SMGs, the H 2 masses derived from [CI] are often consistent with those determined from low excitation 12 CO. We conclude that [CI] observations provide a useful tool to probe the bulk gas and gas processes occurring within merging SMGs, however more detailed, resolved observations are required to fully exploit [CI] as a diagnostic.