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Cool Cores in Galaxy Groups

Cool Cores in Galaxy Groups. Ewan O’Sullivan Harvard-Smithsonian Center for Astrophysics In Collaboration with T. J. Ponman ( University of Birmingham ), J. Vrtilek & L. P. David ( CfA ), A. J. R. Sanderson ( University of Illinois ). Introduction.

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Cool Cores in Galaxy Groups

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  1. Cool Cores in Galaxy Groups EwanO’Sullivan Harvard-Smithsonian Center for Astrophysics In Collaboration with T. J. Ponman (University of Birmingham), J. Vrtilek & L. P. David (CfA), A. J. R. Sanderson (University of Illinois) The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  2. Introduction • The majority of galaxies in the universe are found in galaxy groups (Tully 1987), and many elliptical- dominated groups have massive hot gas halos (Mulchaey 2003). • A general X-ray study of galaxy groups with Chandra and XMM-Newton (and ROSAT), focusing particularly on cooling and feedback processes Questions • It is now clear that AGN heating stops cooling flows in clusters - is this also true in groups? • How does group gas become enriched with metals? The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  3. Groups Sample • 23 groups from XMM archive,18 from Chandra The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  4. Analysis • 2-D multi-component surface brightness fits • Radial spectral profiles (circular or elliptical, deprojected) • Derive mass, entropy, cooling time, etc. profiles, assuming hydrostatic equilibrium • What about disturbed systems? • Adaptively binned spectral maps - each pixel represents a separate spectral fit, but fits are not independent. Behaviour comparable to adaptive smoothing Current focus on XMM data, work in progress! The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  5. NGC 5044 From ROSAT (David et al 1994) • Cooling flow (20 M/yr) • Cooling wake indicates ~100 km/s motion of galaxy From Chandra / XMM: • No CF, no gas kT<0.6 keV (Tamura et al 2003; Buote et al 2003) Our XMM analysis: • No CF, but cooling time less than 109 yrs • Minimal AGN activity, so what prevents cooling? • Is cooling wake seen? Deprojected temperature Gas cooling time Deprojected abundance The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  6. Cooling wake  XMM X-ray image with optical contours Temperature map The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  7. NGC 4636 • Jones et al (2002) use Chandra to find ‘spiral arms’ in core • Shocks from AGN outburst? • Ohto et al (2003) find high kT, excess NH west of core • Cavity blown by AGN jets during previous outburst? Chandra image with VLA-First contours The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  8. Chandra image XMMtemperature • Cavity to E clearly visible • SW ‘Spiral arm’ marks cavity boundary • Highest abundance gas outside galaxy core? Complex spectra… XMM abundance The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  9. NGC 4636 spectral maps XMM Temperature XMM Abundance • Hot gas surrounds core on N and E sides • Highest abundances to SW The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  10. NGC 4636 southwest region • Plume of cool gas to SW with high abundance • AGN driving galaxy/group gas mixing? XMM Temperature XMM Abundance The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  11. NGC 507 • ROSAT shows strong cooling in core (Kim & Fabbiano 1995) • FR-I radio galaxy (Parma et al 1986) • Paolillo et al (2003) find X-ray / radio structure correlated but no CF • AGN power sufficient to stop cooling • Kraft et al (2004) find abundance edge NE of core The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  12. XMM gaussian smoothed XMM temperature DSS optical XMM abundance The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  13. Bright groups comparison • Comparable Mtotal, Mgas profiles • Large difference in kT, central density, Entropy • NGC 507 AGN most active, NGC 4636 activity beginning • AGN cycle governs core entropy? The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  14. AWM 4 & MKW 4: poor clusters • ~2.5 keV systems chosen to be regular, undisturbed • Very large central dominant galaxies • NGC 4073 in MKW4 is radio quiet • NGC 6051 in AWM4 has 100 kpc radio jets The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  15. AWM 4 • Relaxed system, SB profile well described by two -models • Isothermal kT profile • kT and abundance clearly affected by AGN activity - cavity to E, shock and high abundance to NW XMM temperature XMM abundance The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  16. MKW 4 • SB fits show cluster is asymmetrical • Strong kT drop in core but no gas <0.5 keV XMM temperature XMM abundance • Maps show highest abundances in core and to SE, where SB profile shows steepest drop The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  17. MKW 4 / AWM 4 comparison • Very similar mass profiles • MKW4 has cooler, denser, more gas-rich core • Rapid cooling • Gas fraction step in AWM 4  Gas pushed out by AGN The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  18. AWM 4 / MKW 4 summary • Slight difference in core Mtotal caused by difference in BCG mass (factor ~2) • Remaining differences caused by AGN cycle - AWM 4 isothermal because of AGN heating - MKW 4 is cooling, soon to trigger AGN? • Current radio power in AWM 4 ~1041 erg/s, but expect mechanical power to be up to 104 times greater • Energy required to raise MKW 4 temperature to that of AWM 4: ~9x1058 erg or ~3x1043 erg/s for 100 Myr - reasonable for AGN The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

  19. Conclusions • Cooling Flow / AGN connection holds across wide range of mass scales (1 keV groups to massive clusters) • Enrichment of groups through AGN galaxy / group gas mixing likely (at least in central regions) • AGN outbursts probably a major source of energy feedback in groups as well as clusters The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

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