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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

Cold Gas in Cooling Flows

Cooled or just cold?

Alastair Edge - Durham

Charlottesville June 1st 2003

25 th december 1998
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
26 th december 1998
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….
a bit like buses
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)
is this just selection
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).
where is the gas
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
where there is gas there is dust
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.
gas to dust ratios
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.
widening the net with richard wilman
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
origin of the cold gas
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?
it s cooled
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.
  • 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?
5 year plan
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
points for discussion
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?
  • 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.