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The Australia Telescope National Facility Colloquium
11:00-12:00 Fri 27 May 2005

AAO Lecture Theatre

Dr Carlos de Breuck


Spitzer and CO observations of high redshift radio galaxies - Dr Carlos de Breuck Colloquium

Powerful radio galaxies are the most luminous galaxies known
in K-band out to z=5.2. I will introduce a Spitzer Cycle 1 program aimed
at showing that these galaxies are also the most massive galaxies known
at every redshift, with baryonic masses of ~10^12 M_Sun. Using 8-band
mid-IR imaging and supporting optical + near-IR photometry and optical
polarimetry, we shall disentangle the stellar light from the direct and
scattered contributions from the AGN and from the narrow-line regions.
Using (sub)mm photometry, we will disentangle the hot, AGN heated dust
from the cooler starburst-heated dust, providing an improved measure of
the instantaneous star formation rate. Our Spitzer observations are
still ongoing, but I shall present some preliminary results from our

Next, I shall discuss the thermal dust and CO emission in high redshift
radio galaxies. A survey of >70 radio galaxies shows a clear increase in
the FIR luminosity at z>3, indicating a higher star formation rate at
high redshift. I shall discuss the 7 CO detections in z>2 radio galaxies
reported to date. Some trends are starting to emerge, but also some
observational biasses such as the heavy dependence on prior submm
thermal dust detections and the reliance of high-order CO transitions.
Some sources with high gas/dust ratios, or less dense molecular gas may
still be under-represented in the ~35 high redshift CO detection
reported thus far.

More information


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