R. J. Wilman

A semi-empirical simulation of the extragalactic radio continuum sky for next generation radio telescopes

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 similar or equal to 320 million simulated radio sources. The simulation covers a sky area of 20x20 deg^2 - 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.

The discovery of a galaxy-wide superwind from a young massive galaxy at redshift z ≈ 3

High-velocity galactic outflows, driven by intense bursts of star formation and black hole accretion, are processes invoked by current theories of galaxy formation to terminate star formation in the most massive galaxies and to deposit heavy elements in the intergalactic medium. From existing observational evidence (for high-redshift galaxies) it is unclear whether such outflows are localized to regions of intense star formation just a few kiloparsecs in extent, or whether they instead have a significant impact on the entire galaxy and its surroundings. Here we present two-dimensional spectroscopy of a star-forming galaxy at redshift z = 3.09 (seen 11.5 gigayears ago, when the Universe was 20 per cent of its current age): its spatially extended Lyα line emission appears to be absorbed by H i in a foreground screen covering the entire galaxy, with a lateral extent of at least 100 kpc and remarkable velocity coherence. This screen was ejected from the galaxy during a starburst several 108 years earlier and has subsequently swept up gas from the surrounding intergalactic medium and cooled. This demonstrates the galaxy-wide impact of high-redshift superwinds.

A survey of molecular hydrogen in the central galaxies of cooling flows

We present a large sample of H- and K-band spectra of 32 optically line-luminous central cluster galaxies. We find significant rovibrational H2 emission in 23 of these galaxies as well as H recombination and/or (FeII) emission in another 5. This represents a fourfold increase in the number of molecular line detections known. A number of the detections are of extended emission (5-20 kpc). In several objects we find significant (SiVI) emission that appears to correlate with the strength of high ionization lines in the optical (e.g. (OIII)). This comprehensive sample builds on previous work and confirms that warm (1000-2500 K) molecular hydrogen is present wherever there is ionized material in the cores of cooling flows and in most cases it also coincides with CO molecular line emission.

Discovery of atomic and molecular mid-infrared emission lines in off-nuclear regions of NGC 1275 and NGC 4696 with the Spitzer Space Telescope

ABSTRACT We present Spitzer high-resolution spectra of off-nuclearregions in the central cluster galax-ies NGC1275and NGC4696in the Perseus and Centaurus clusters, respectively.Both objectsare surrounded by extensive optical emission-line filamentary nebulae, bright outer parts ofwhich are the targets of our observations. The 10–37 µm spectra show strong pure rotationallines from molecular hydrogen revealing a molecular component to the filaments which hasan excitation temperature of ∼ 300−400K. The flux in the 0-0S(1) molecular hydrogen linecorrelates well with the strength of the optical lines, having about 3 per cent of the Hα+[NII]emission. The 11.3µm PAH feature is seen in some spectra. Emission is also seen from bothlow and high ionization fine structure lines. Molecular hydr ogen cooler than ∼400K domi-nates the mass of the outer filaments; the nebulae are predomi nantly molecular.Key words: galaxies: clusters: general – galaxies: clusters: individual: NGC 1275 – galaxies:clusters: individual: NGC 4696 – – intergalactic medium – in frared: galaxies

The nature of the molecular gas system in the core of NGC 1275

We present near-infrared integral field spectroscopy of the central kiloparsec of NGC 1275 at the heart of the Perseus cluster of galaxies, obtained with the Integral Field Unit (IFU) of the United Kingdom Infrared Telescope (UKIRT) Imaging Spectrometer (UIST). The nuclear rovibrational H 2 emission is spatially resolved and is likely to originate approximately 50 pc from the active nucleus. The Paα emission is, by contrast, spatially unresolved. The requirements for thermal excitation of the H 2 by nuclear X-radiation, its kinematics on subarcsec scales and its stability against self-gravity together suggest that the observed H 2 is part of a clumpy disc rotating about the radio-jet axis. The sharp jump in the H 2 velocity across the nucleus implies a black hole mass of 3.4 x 10 8 M ○. , with a systematic error of ±0.18 dex due to the uncertainty in the radio-jet inclination. This agrees well with the value implied by the empirical correlation between black hole mass and stellar velocity dispersion for nearby elliptical galaxies, and is ∼100 times the stellar mass in this region.

An infrared–radio simulation of the extragalactic sky: from the Square Kilometre Array to Herschel

The definitive version can be found at: http://www3.interscience.wiley.com/ Copyright Royal Astronomical Society

Resolved spectroscopy of a gravitationally lensed L* lyman-break galaxy at z ∼ 5

We exploit the gravitational potential of a massive, rich cluster at z= 0.77 to study the internal properties of a gravitationally lensed galaxy at z= 4.88 . 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 ~L* Lyman-break galaxy with an intrinsic size of only 2.0 × 0.8 kpc , a velocity gradient of ≲60 km s^(−1) and an implied dynamical mass of 1.0 × 10^(10) M_⊙ within 2 kpc. We infer an integrated star formation rate of just 12 ± 2 M_⊙ yr^(−1) from the intrinsic [O ii]λ3727 emission-line flux. The Lyα emission appears redshifted by +200 ± 40 km s^(−1) 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 10 km s^(−1) . 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 ~500 km s^(−1) . 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.

Herschel photometry of brightest cluster galaxies in cooling flow clusters

Herschel photometry of brightest cluster galaxies in cooling flow clusters , A. C. Edge1, J. B. R. Oonk2, R. Mittal3, S. W. Allen4, S. A. Baum3, H. Bohringer5, J. N. Bregman6, M. N. Bremer7, F. Combes8, C. S. Crawford9, M. Donahue10, E. Egami11, A. C. Fabian9, G. J. Ferland12, S. L. Hamer1, N. A. Hatch13, W. Jaffe2, R. M. Johnstone9, B. R. McNamara14, C. P. O’Dea15, P. Popesso5, A. C. Quillen16, P. Salome8, C. L. Sarazin17, G. M. Voit10, R. J. Wilman18, and M. W. Wise19

Probing the absorbing haloes around two high-redshift radio galaxies with VLT-UVES

We present VLT-UVES echelle spectroscopy of the HI and C IV absorption in the spatially- extended Lyemission around two high-redshift radio galaxies 0200+015 (z=2.23) and 0943- 242 (z=2.92). The absorbers in 0943-242 exhibit little additional struct ure compared with previous low- resolution spectroscopy and the main absorber is still consistent with HI column density of ∼ 10 19 cm 2 . This is consistent with a picture in which the absorbing gas has low density and low metallicity and is distributed in a smooth absorbing shell located beyond the emission- line gas. However, the main absorbers in 0200+015 are very different. The previous single absorber fit of H I column density ≃ 10 19 cm 2 , now splits into two ∼ 4 × 10 14 cm 2 ab- sorbers which extend more than 15 kpc to obscure additional Lyemission coincident with a radio lobe in these high-resolution observations. Althoug h consistent with the shell-like dis- tribution for the absorption systems, 0200+015 requires a much higher metal enrichment than 0943-242. The metallicity, inferred from the C IV absorption, is considerably lower in 0943- 242 than in 0200+015. We explain these differences with an evolutionary scenario based on the size of the radio source. In both sources the HI absorption gas originates from either a gas-rich merger or pristine cluster gas which cools and collapses towards the centre of the dark matter halo. The higher metallicity in the larger radio source (0200+015) may be a result of a starburst driven superwind (concurrent with the triggering of the radio emission) which has engulfed the outer halo in this older source. We also find a significant blue asymmetry in the HeII �1640 emission line, suggesting that the line emitting gas is outflowing from the central regi ons. Dust obscuration toward the central engine, presumably due to the dusty torus invoked in Unified Scheme, prevents us from seeing outflow away from our line-of-sight.

MASSIVE MOLECULAR GAS FLOWS IN THE A1664 BRIGHTEST CLUSTER GALAXY

We report ALMA Early Science CO(1-0) and CO(3-2) observations of the brightest cluster galaxy (BCG) in A1664. The BCG contains 1.1 × 1010 M ☉ of molecular gas divided roughly equally between two distinct velocity systems: one from –250 to +250 km s–1 centered on the BCGs systemic velocity and a high-velocity system blueshifted by 570 km s–1 with respect to the systemic velocity. The BCGs systemic component shows a smooth velocity gradient across the BCG center, suggestive of rotation about the nucleus. However, the mass and velocity structure are highly asymmetric and there is little star formation coincident with a putative disk. It may be an inflow of gas that will settle into a disk over several 108 yr. The high-velocity system consists of two gas clumps, each ~2 kpc across, located to the north and southeast of the nucleus. Each has a line of sight velocity spread of 250-300 km s–1. The velocity of the gas in the high-velocity system increases toward the BCG center and may be a massive flow into the nucleus. However, the velocity gradient is not smooth. These structures are also coincident with low optical-ultraviolet surface brightness regions, which could indicate dust extinction associated with each clump. The structure is complex, making a clear interpretation difficult, but if the dusty, molecular gas lies predominantly in front of the BCG, the blueshifted velocities would indicate an outflow. Based on the energy requirements, such a massive outflow would most likely be driven by the active galactic nucleus. A merger origin is unlikely but cannot be ruled out.