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We present VLT-SINFONI K-band integral field spectroscopy of the central galaxies in the cool core clusters A1664, A2204 and PKS 0745−191, to probe the spatio-kinematic properties of the Paα and ro-vibrational H2 line emission. In A1664, the two emission-line velocity systems seen in our previous Hα spectroscopy appear in both Paα and H2 emission, with notable morphological differences. The recession velocity of the red component of Paα increases linearly with decreasing radius, particularly along an 8 kpc filament aligned with the major axis of the underlying galaxy and the cluster X-ray emission. These kinematics are modelled as gravitational free-fall as gas cools rapidly out of the hot phase. In A2204, the gas shows three or four filaments reaching radii of 10 kpc, three of which lie towards ‘ghost bubbles’ seen in X-ray imaging by Sanders et al. For PKS 0745−191, we confirm the twin-arm morphology in the narrow-band images of Donahue et al.; the Paα kinematics suggest rotational motion about an axis aligned with the kiloparsec-scale radio jet; on nucleus, we find an underlying broad Paα component [full width at half-maximum (FWHM) ] and a secondary H2 velocity system redshifted by . The S(3)/Paα ratio is the highest in the most isolated and extended regions where it matches the levels in the NGC 1275 filaments as modelled by Ferland et al. Regions with much lower ratios highlight active star formation and are often kinematically quiescent (FWHM ). Our findings suggest that the three clusters may be captured in different stages of the ‘cold feedback’ cycle of Pizzolato & Soker, with A1664 in a short-lived phase of extreme cooling and star formation prior to an active galactic nucleus (AGN) heating event; PKS 0745−191 in an outburst state with the AGN accreting from a cool gas disc, and A2204 in a later phase in which cool gas is dragged out of the galaxy by the buoyant rise of old radio bubbles. [ABSTRACT FROM AUTHOR]

We present optical integral field spectroscopy of the Hα-luminous central cluster galaxies in the cores of the cooling flow clusters A1664, A1835, A2204 and Zw8193. From the [N ii]+Hα complex in these moderate resolution (70–150 km s−1) spectra we derive 2D views of the distribution and kinematics of the emission-line gas, and further diagnostics from the [S ii] and [O i] lines. The Hα emission shows a variety of disturbed morphologies, ranging from smooth but distorted to clumpy and filamentary, with velocity gradients and splittings of several hundred km s−1 on spatial scales of 20 kpc or more. Despite the small sample size, there are some generic features. The most disturbed Hα emission appears to be associated with secondary galaxies within 10–20 kpc (projected) of the central galaxy and close in velocity to the Hα. The global Hα kinematics match those of the CO(1–0) emission in single-dish data. The [N ii]/Hα, [S ii]/Hα and [O i]/Hα ratios vary little with position, local Hα surface brightness or between clusters. We propose that the Hα and CO emission arise in molecular clouds heated by a starburst, and that the latter has been triggered by interaction with a secondary galaxy. Such CO emission is known to trace massive compact (<20 kpc) reservoirs of cool molecular gas, and it is plausible that an infalling galaxy would disturb this gas, distorting the Hα morphology and initiating widespread star formation. We also examine the role of cloud–cloud collisions in the undisturbed molecular gas reservoir, and suggest that they might be an important source of excitation for the emission-line gas in the cores of lower Hα luminosity clusters with less intense star formation. [ABSTRACT FROM AUTHOR]

Abstract We present a large sample of H - and K -band spectra of 32 optically line-luminous central cluster galaxies. We find significant rovibrational H 2 emission in 23 of these galaxies as well as H recombination and/or [Fe ii] emission in another five. 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 [Si vi] emission that appears to correlate with the strength of high ionization lines in the optical (e.g. [O iii]). 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. [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]