We report subarcsec-resolution X-ray imaging of the core of the Perseus cluster around the galaxy NGC 1275 with the Chandra X-ray Observatory. The ROSAT-discovered holes associated with the radio lobes have X-ray bright rims which are cooler than the surrounding gas and not due to shocks. The holes themselves may contain some hotter gas. We map strong photoelectric absorption across the Northern lobe and rim due to a small infalling irregular galaxy, known as the high velocity system. Two outer holes, one of which was previously known, are identified with recently found spurs of low-frequency radio emission. The spiral appearance of the X-ray cooler gas and the outer optical parts of NGC 1275 may be due to angular momentum in the cooling flow.Comment: 5 pages, 7 figures (6 colour), accepted by MNRAS, high resolution version at http://www-xray.ast.cam.ac.uk/papers/per_chandra.ps.g

We present preliminary results from a deep observation lasting almost 200 ks, of the centre of the Perseus cluster of galaxies around NGC 1275. The X-ray surface brightness of the intracluster gas beyond the inner 20 kpc, which contains the inner radio bubbles, is very smooth apart from some low amplitude quasi-periodic ripples. A clear density jump at a radius of 24 kpc to the NE, about 10 kpc out from the bubble rim, appears to be due to a weak shock driven by the northern radio bubble. A similar front may exist round both inner bubbles but is masked elsewhere by rim emission from bright cooler gas. The continuous blowing of bubbles by the central radio source, leading to the propagation of weak shocks seen as the observed fronts and ripples, gives a rate of working which balances the radiative cooling within the inner 50 kpc of the cluster core.

We present preliminary results from a deep observation lasting almost 200 ks, of the centre of the Perseus cluster of galaxies around NGC 1275. The X-ray surface brightness of the intracluster gas beyond the inner 20 kpc, which contains the inner radio bubbles, is very smooth apart from some low amplitude quasi-periodic ripples. A clear density jump at a radius of 24 kpc to the NE, about 10 kpc out from the bubble rim, appears to be due to a weak shock driven by the northern radio bubble. A similar front may exist round both inner bubbles but is masked elsewhere by rim emission from bright cooler gas. The continuous blowing of bubbles by the central radio source, leading to the propagation of weak shocks and viscously-dissipating sound waves seen as the observed fronts and ripples, gives a rate of working which balances the radiative cooling within the inner 50 kpc of the cluster core.Comment: Accepted for publication in MNRAS (minor changes) Higher picture quality available from http://www-xray.ast.cam.ac.uk/papers/per_200ks.pd

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.

The giant elliptical galaxy NGC 1275, at the centre of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments 1,2 , which are plausibly about >10 8 yr old 3 . The filaments are dragged out from the centre of the galaxy by the radio bubbles rising buoyantly in the hot intracluster gas 4 before later falling back. They act as dramatic markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding 4×10 7 K gas has been unclear. Here we report new observations that resolve thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.The images presented here (Figs. 1-4) were taken with the Advanced Camera for Surveys (ACS) on the NASA Hubble Space Telescope (HST) using three filters; F625W in the red contains the Hα line, F550M is mostly continuum and F435W in the blue which highlights young stars. In Fig. 2 we show part of the Northern filament ~27 kpc from the nucleus (we adopt H 0 =71 km s -1 Mpc -1 which at a redshift 0.0176 for NGC 1275 gives 352 pc arcsec -1 ). The filaments seen in the WIYN groundbased image (right) are just resolved into narrow threads with the HST ACS (see Supplementary Information). This also occurs in many other filaments including the north-west "horseshoe" filament ( Fig. 3) which lies immediately interior to the outer ghost bubble in X-ray images 5 . A fine thread of emission is seen in the Northern filament system extending about 16 arcsec or 5.8 kpc. Averaged over kpc strips it is about 4 pixels (0.2 arcsec) or about 70 pc wide. (This is an upper limit as the point spread function of the ACS is about one half this value.) The aspect ratio (length / thickness) therefore approaches 100. The top of the horseshoe which is about 6 kpc across is similar, as are many other relatively isolated filaments.In order to estimate the required magnetic field we need to know the properties of a filament and its surroundings. We shall concentrate on a thread of radius 35 pc and length 6 kpc at a distance of 25 kpc from the nucleus of NGC 1275 (Fig. 2) as a basic structural unit typical of what is now resolved in the filaments. To estimate the mass for such a thread we scale from the total gas mass of 10 8 M⊙ inferred from CO emission 6 observed in a 22 arcsec IRAM beam on the same Northern filament complex. Assuming that the mass scales with Hα emission, which is the case for the H 2 emission measured with Spitzer 7 , then our fiducial thread has a mass of about 10 6 M⊙. Its mean density is then ~2 cm -3 and perpendicular column density N ~ 4×10 20 cm -2 or Σ ┴ ~ 7×10 -4 g cm -2 . The lengthwise column density, Σ∥, is l/2r times larger.The variation in projected rad...