Cold molecular gas has recently been detected in several cooling flow clusters of galaxies containing huge optical nebula. These optical filaments are tightly linked to cooling flows and related phenomena, such as rising bubbles of relativistic plasma fed by radio jets. We present here a map, in the CO(2-1) rotational line, of the cold molecular gas associated with some of the Hα filaments surrounding the central galaxy of the Perseus cluster: NGC 1275. The map, extending to about 50 kpc (135 arcsec) from the center of the galaxy, has been made with the 18-receiver array HERA at the focus of the IRAM 30 m telescope. Although most of the cold gas is concentrated to the center of the galaxy, the CO emission is also clearly associated with the extended filaments conspicuous in ionised gas, and could trace a possible reservoir fueling the star formation there. Some of the CO emission is also found where the X-ray gas could cool down more efficiently at the rims of the central X-ray cavities (where the hot gas is thought to have been pushed out and compressed by the expanding radio lobes of the central AGN). The CO global kinematics do not show any rotation in NGC 1275. The cold gas is probably a mixture of gas falling down on the central galaxy and of uplifted gas dragged out by a rising bubble in the intracluster medium. As recently suggested in other cluster cores, the cold gas peculiar morphology and kinematics argue for the picture of an intermittent cooling flow scenario where the central AGN plays an important role.

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Abstract. We have measured the angular correlation function, w(θ), of radio sources in the 1.4 GHz NVSS and FIRST radio surveys. Below ∼6 the signal is dominated by the size distribution of classical double radio galaxies, an effect underestimated in some previous studies. We model the physical size distribution of FRII radio galaxies to account for this excess signal in w(θ). The amplitude of the true cosmological clustering of radio sources is roughly constant at A 1 × 10 −3 for flux limits of 3-40 mJy, but has increased to A 7× 10 −3 at 200 mJy. This can be explained if powerful (FRII) radio galaxies probe significantly more massive structures compared to radio galaxies of average power at z ∼ 1. This is consistent with powerful high-redshift radio galaxies generally having massive (forming) elliptical hosts in rich (proto-)cluster environments. For FRIIs we derive a spatial (comoving) correlation length of r 0 = 14±3 h −1 Mpc. This is remarkably close to that measured for extremely red objects (EROs) associated with a population of old elliptical galaxies at z ∼ 1 by Daddi et al. (2001). Based on their similar clustering properties, we propose that EROs and powerful radio galaxies may be the same systems seen at different evolutionary stages. Their r 0 is ∼2× higher than that of QSOs at a similar redshift, and comparable to that of bright ellipticals locally. This suggests that r 0 (comoving) of these galaxies has changed little from z ∼ 1 to z = 0, in agreement with current ΛCDM hierarchical merging models for the clustering evolution of massive early-type galaxies. Alternatively, the clustering of radio galaxies can be explained by the galaxy conservation model. This then implies that radio galaxies of average power are the progenitors of the local field population of early-types, while the most powerful radio galaxies will evolve into a present-day population with r 0 comparable to that of local rich clusters.

We examine the radio properties of the Brightest Cluster Galaxies (BCGs) in a large sample of X-ray selected galaxy clusters comprising the Brightest Cluster Sample (BCS), the extended BCS (eBCS) and ROSAT-ESO Flux Limited X-ray (REFLEX) cluster catalogues. We have multi-frequency radio observations of the BCG using a variety of data from the Australia Telescope Compact Array (ATCA), Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA) telescopes. The radio spectral energy distributions (SEDs) of these objects are decomposed into a component attributed to on-going accretion by the active galactic nuclei (AGN) that we refer to as 'the core', and a more diffuse, ageing component we refer to as the 'non-core'. These BCGs are matched to previous studies to determine whether they exhibit emission lines (principally H-α), indicative of the presence of a strong cooling cluster core. We consider how the radio properties of the BCGs vary with cluster environmental factors. Line emitting BCGs are shown to generally host more powerful radio sources, exhibiting the presence of a strong, distinguishable core component in about 60% of cases. This core component more strongly correlates with the BCG's [OIII]5007 Å line emission. For BCGs in line-emitting clusters, the X-ray cavity power correlates with both the extended and core radio emission, suggestive of steady fueling of the AGN over bubble-rise timescales in these clusters.

High-velocity galactic outflows, driven by intense bursts of star formation and black hole accretion, are invoked by current theories of galaxy formation 1 to terminate star formation in the most massive galaxies and to deposit heavy elements in the intergalactic medium. From existing observational evidence 2,3 on 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 4 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 HI in a foreground screen covering the entire galaxy, with a lateral extent of at least 100kpc and remarkable velocity coherence. It was plausibly ejected from the galaxy during a starburst several 10 8 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.The formation of galaxies requires gas to cool in haloes of dark matter that collapse under gravity from the expansion of the Universe. However, cooling alone overproduces bright galaxies at the present day, so models incorporate thermal conduction, photoionization and galaxy merging, together with additional 'feedback' 1 in the form of galactic-scale outflows. The latter are powered by supernovae and massive stellar winds, or by relativistic winds and jets resulting from gas accretion onto supermassive black holes. Although starburst superwinds have been studied 5 in local dwarf galaxies (such as M82), observational evidence for their counterparts in young massive galaxies at high redshift has been less direct.In Lyman-break galaxies (LBGs) -high-redshift galaxies with moderate masses and star-formation rates -spectroscopic evidence points to powerful outflows 2,3 of interstellar gas, with absorption lines being blueshifted by several hundred kilometres per second from the galaxy's systemic velocity. The gravitationally lensed LBG MS1512-cB58 at redshift z=2.73 is a clear example 3 : absorbing gas is outflowing at ∼ 255 km s −1 at a rate exceeding the star-formation rate, and although it covers the entire starforming region, this shows only that the radius of any shell exceeds ∼ 1 kpc; it is not known whether the outflows are collimated and localized to star-forming regions, or whether they are galaxy-wide. The latter is suggested by the observed decrease in the intergalactic medium (IGM) HI opacity in background quasar sightlines that are close in projection to LBGs 6 (within 0.7 Mpc co-moving). This may indicate that LBGs drive superwinds at ∼ 600 km s −1 for several 10 8 yr, or it might be a statistical fluctuation since there are few LBG-quasar pairs at the smallest separations.To characterize such outflows better via absorption studies, a background light source...