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To exploit synergies between the Herschel Space Observatory and next generation radio facilities, we have extended the semi-empirical extragalactic radio continuum simulation of Wilman et al. to the mid- and far-infrared. Here, we describe the assignment of infrared spectral energy distributions (SEDs) to the star-forming galaxies and active galactic nuclei, using Spitzer 24, 70 and 160 μm and SCUBA 850 μm survey results as the main constraints. Star-forming galaxies dominate the source counts, and a model in which their far-infrared–radio correlation and infrared SED assignment procedure are invariant with redshift underpredicts the observed 24 and 70 μm source counts. The 70 μm deficit can be eliminated if the star-forming galaxies undergo stronger luminosity evolution than originally assumed for the radio simulation, a requirement which may be partially ascribed to known non-linearity in the far-infrared–radio correlation at low luminosity if it evolves with redshift. At 24 μm, the shortfall is reduced if the star-forming galaxies develop SEDs with cooler dust and correspondingly stronger polycyclic aromatic hydrocarbon emission features with increasing redshift at a given far-infrared luminosity, but this trend may reverse at in order not to overproduce the submillimetre source counts. The resulting model compares favourably with recent Balloon-borne Large Aperture Submillimetre Telescope ( BLAST) results, and we have extended the simulation data base to aid the interpretation of Herschel surveys. Such comparisons may also facilitate further model refinement and revised predictions for the Square Kilometre Array and its precursors. [ABSTRACT FROM AUTHOR]

We have developed a semi-empirical simulation of the extragalactic radio continuum sky suitable for aiding the design of next generation radio interferometers such as the Square Kilometre Array (SKA). The emphasis is on modelling the large-scale cosmological distribution of radio sources rather than the internal structure of individual galaxies. Here we provide a description of the simulation to accompany the online release of a catalogue of ≃320 million simulated radio sources. The simulation covers a sky area of 20 × 20 deg2– a plausible upper limit to the instantaneous field of view attainable with future (e.g. SKA) aperture array technologies – out to a cosmological redshift of z= 20, and down to flux density limits of 10 nJy at 151, 610 MHz, 1.4, 4.86 and 18 GHz. Five distinct source types are included: radio-quiet active galactic nuclei (AGN), radio-loud AGN of the Fanaroff–Riley type I (FR I) and FR II structural classes, and star-forming galaxies, the latter split into populations of quiescent and starbursting galaxies. In our semi-empirical approach, the simulated sources are drawn from observed (or extrapolated) luminosity functions and grafted on to an underlying dark matter density field with biases which reflect their measured large-scale clustering. A numerical Press–Schechter style filtering of the density field is used to identify and populate clusters of galaxies. For economy of output, radio source structures are constructed from point source and elliptical subcomponents, and for FR I and FR II sources an orientation-based unification and beaming model is used to partition flux between the core and extended lobes and hotspots. The extensive simulation output gives users the flexibility to post-process the catalogues to achieve more complete agreement with observational data in the years ahead. The ultimate aim is for the ‘idealized skies’ generated by this simulation and associated post-processing to be fed to telescope simulators to optimize the design of the SKA itself. [ABSTRACT FROM AUTHOR]

ABSTRACT We measure the angular clustering of ∼2000 radio sources in the Bootes Deep Field, covering 5.3 deg[sup 2] down to S[sub 1.4GHz]= 0.2 mJy . With reference to work by Blake & Wall, we show that the size distribution of multi-component radio galaxies dominates the overall clustering signal, and that its amplitude extrapolates smoothly from their measurements above 5 mJy. The upper limits on any true galaxy–galaxy clustering are consistent with the clustering of sub-mJy radio-loud active galatic nuclei (AGN) being effectively diluted by the more weakly clustered IRAS-type starburst galaxies. Source count models imply that the survey contains ≃400 of the latter galaxies above 0.2 mJy out to z∼ 1–2 . Measurement of their clustering must await their identification via the optical and infrared data due on this field. [ABSTRACT FROM AUTHOR]

The origin of rovibrational H[sub 2] emission in the central galaxies of cooling flow clusters is poorly understood. Here we address this issue using data from our near-infrared spectroscopic survey of 32 of the most line-luminous such systems, presented in the companion paper by Edge et al. We consider excitation by X-rays from the surrounding intracluster medium (ICM), ultraviolet (UV) radiation from young stars, and shocks. The v = 1-0 K-band lines with upper levels within 10[sup 4] K of the ground state appear to be mostly thermalized (implying gas densities ... 10[sup 5] cm[sup -3]), with the excitation temperature typically exceeding 2000 K, as found earlier by Jaffe, Bremer & van der Werf. Together with the lack of strong v = 2-0 lines in the H-band, this rules out UV radiative fluorescence. Using the CLOUDY photoionization code, we deduce that the H[sub 2] lines can originate in a population of dense clouds, exposed to the same hot (T ∼ 50000 K) stellar continuum as the lower density gas which produces the bulk of the forbidden optical line emission in the Hα-luminous systems. This dense gas may be in the form of self-gravitating clouds deposited directly by the cooling flow, or may instead be produced in the high-pressure zones behind strong shocks. Furthermore, the shocked gas is likely to be gravitationally unstable, so collisions between the larger clouds may lead to the formation of globular clusters. [ABSTRACT FROM AUTHOR]

We exploit the gravitational potential of a massive, rich cluster at to study the internal properties of a gravitationally lensed galaxy at . Using high-resolution Hubble Space Telescope imaging together with optical (VIMOS) and near-infrared (SINFONI) integral field spectroscopy, we have studied the rest-frame ultraviolet and optical properties of the lensed galaxy seen through the cluster RCS0224−002. Using a detailed gravitational lens model of the cluster, we reconstruct the source-frame morphology on 200 pc scales and find an Lyman-break galaxy with an intrinsic size of only , a velocity gradient of and an implied dynamical mass of within 2 kpc. We infer an integrated star formation rate of just from the intrinsic [O ii]λ3727 emission-line flux. The Lyα emission appears redshifted by with respect to the [O ii] emission. The Lyα is also significantly more extended than the nebular emission, extending over 11.9 × 2.4 kpc. Over this area, the Lyα centroid varies by less than . We model the asymmetric Lyα emission with an underlying Gaussian profile with an absorber in the blue wing and find that the underlying Lyα emission-line centroid is in excellent agreement with the [O ii] emission-line redshift. By examining the spatially resolved structure of the [O ii] and Lyα emission lines, we investigate the nature of this system. The model for local starburst galaxies suggested by Mas-Hesse et al. provides a good description of our data, and suggests that the galaxy is surrounded by a galactic-scale bipolar outflow which has recently bursted out of the system. The outflow, which appears to be currently located ≳30 kpc from the galaxy, is escaping at a speed of upto . Although the mass of the outflow is uncertain, the geometry and velocity of the outflow suggests that the ejected material is travelling far faster than escape velocity and will travel more than 1 Mpc (comoving) before eventually stalling. [ABSTRACT FROM AUTHOR]