We propose Herschel observations of the CO Spectral Line Energy Distribution (SLED) in a sample of seven local (z < 0.1) radio galaxies with the highest CO(1-0) luminosities. These radio galaxies fall into two classes in terms of their infrared (IR)-to-CO luminosity ratio, or star formation efficiency - those with high IR/CO similar to IR luminous starburst galaxies, and those with low IR/CO ratios comparable to low luminosity spiral galaxies. The observed dichotomy in IR/CO likely represents (1) intrinsic differences in the star formation efficiencies within the sample, (2) an enhancement in the infrared luminosity of the galaxies with high IR/CO by AGN dust heating, (3) or inaccuracies in the star formation efficiency determinations introduced through the use of a constant CO luminosity-to-molecular gas mass conversion factor, or through the use of CO(1-0) to trace the molecular gas actively involved in star formation. With the Herschel Spire FTS, we will detect high-J (>5) rotation CO transitions, enabling (1) an accurate determination of the star-forming molecular gas mass, temperature and density, and thus a more accurate estimate of the star formation efficiency, (2) an assessment of the effect AGN and starbursts have on the excitation of the high-J CO transitions, and possibly of H2O and OH lines. In addition, we will make use of our data in concert with the HERCULES dataset to (3) determine whether the high-J CO transitions scale with far-IR luminosity, and are therefore useful tracers of the star formation rates of radio galaxies. These observations will provide, for the first time, a truly robust insight into star formation and AGN heating of gas in radioselected, AGNdominated environments. In addition, the analysis will be applicable to the interpretation of highJ CO emission from high redshift AGN hosts done with Herschel and ALMA.
Publication
Instrument
SPIRE_SpireSpectrometer_
Temporal Coverage
2012-09-23T18:24:27Z/2012-09-23T20:54:47Z
Version
SPG v14.1.0
Mission Description
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, evans et al., 2013, 'High-J CO Emission Lines in Molecular Gas-Rich Radio Galaxies with Low and High Star Formation Efficiencies', SPG v14.1.0, European Space Agency, https://doi.org/10.5270/esa-89pwv5l
