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Cold Gas in Cooling Flows

Cold Gas in Cooling Flows. Cooled or just cold?. Alastair Edge - Durham. Charlottesville June 1st 2003. 25 th December 1998. 10-15 clusters with >1000 M o yr -1 flows. Dozens of central galaxies from ROSAT Survey known to have strong optical line emission.

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Cold Gas in Cooling Flows

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  1. Cold Gas in Cooling Flows Cooled or just cold? Alastair Edge - Durham Charlottesville June 1st 2003

  2. 25th December 1998 • 10-15 clusters with >1000 Moyr-1 flows • Dozens of central galaxies from ROSAT • Survey known to have strong optical • line emission • Only NGC1275 known to have cold gas • The gap between cold gas expected to • cold gas known has never been wider

  3. 26th December 1998 • The upgrade to the A-band receiver took place in December 1998 and offered enhanced sensitivity over A2. • The highest redshift cooling flows have CO(3-2) redshifted into the A-band. • The total deposited mass within the A3 beam in these systems should be high. • I obtained service observations to see….

  4. A bit like buses……… • Buoyed by the success with the JCMT the next logical step was looking for CO(1-0) with IRAM-30m • From three runs in 1999, 2000 and 2002, we made 20 CO(1-0) detections with IRAM • More CO(3-2), CO(4-3) and CO(5-4) data from CSO and JCMT • Derived molecular gas masses lie between • 109-1011.5M⊙ (=1-300 x 109)

  5. Is this just selection? • There are now 60 clusters with recent IRAM-30m data (Edge 2001, Salome & Combes 2003 and Edge etal in prep). • Of these, 24 are detected with the detection fraction strongly dependent on optical line flux. • The detected CO line width distribution is relatively narrow (200-400km s-1).

  6. Where is the gas? • The JCMT, IRAM-30m and CSO data are of limited resolution (15-30”). • Obtaining higher spatial resolution requires mm-interferometry. • Apply for Owens Valley time (OVRO) • Five clusters observed so far (Edge & Frayer 2003, submitted) • Implied column densities >1022cm-2

  7. Where there is gas, there is dust • From JCMT SCUBA observations of A1835 and A2390 it is clear that there is a significant mass of cool dust in cDs as found from FIR data from IRAS. • Using SCUBA we made two more detections (A1068 and RXJ0821+07) and Chapman etal 2002 detect Zw3146 and E1455+22.

  8. Gas-to-Dust Ratios • Using SCUBA and IRAS detections and limits we can determine gas-to-dust ratios using a fixed dust temperature. • Mean gas-to-dust ratio is 1825 (Tdust=40K) or 925 (Tdust=35K). These values are higher than Galactic values but bracket values for ULIRGs and starbursts.

  9. Widening the net with Richard Wilman • Recent UKIRT UIST IFU and VLT VIMOS IFU observations very promising! • Having obtained detailed information on the molecular and ionised Hydrogen in these galaxies, the obvious next step is to look for atomic Hydrogen at 21cm. • Search in higher redshift cooling flows

  10. Origin of the cold gas • NGC1275 exhibits a number of peculiar features that have been attributed to a recent merger. • Most of the other 24 CO-detected central cluster galaxies share the properties of NGC1275. • Is this a coincidence or telling us that there is a common origin to all of these features?

  11. It’s cooled • The simplest explanation of the cool molecular gas we detect is that it is the long-awaited `sink’ of gas. • With the radically `down-sized’ X-ray cooling flow deposition rates, it is possible that the 109-11.5 M⊙of molecular gas found is deposited gas that is yet to be formed into stars.

  12. Alternatives? • Can mergers with gas-rich galaxies supply enough gas often enough given the HI-deficiency found in clusters? • Is this the ISM of the central galaxy? • Why the close link to short central cooling times?

  13. 5 Year Plan…. • SIRTF - FIR spectroscopy and photometry to get other cooling lines (CII 158μm and OI 63μm) and dust masses two orders of magnitude better than IRAS+SCUBA. • SOFIA – sub-mm/FIR spectroscopy of • brightest objects. • More mm-interferometry from Plateau de Bure or CARMA

  14. Points for discussion • Links to optical line emission? • Why are the CO lines so narrow? • Why isn’t Cygnus-A detected? • What fraction of the stars in the central galaxy form from cooled gas? • Can we trace the growth of the `cold sink’ with look back time?

  15. Conclusions • No-one in the audience today can ever state in a paper that there is no evidence for cold molecular gas in cooling flows! • Even you, James.

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