Prediction of the Cosmic Evolution of the CO-Luminosity Functions

Journal article

We predict the emission line luminosity functions (LFs) of the first 10 rotational transitions of CO in galaxies at redshift z=0 to z=10. This prediction relies on a recently presented simulation of the molecular cold gas content in ~3e7 evolving galaxies based on the Millennium Simulation. We combine this simulation with a model for the conversion between molecular mass and CO-line intensities, which incorporates the following mechanisms: (i) molecular gas is heated by the CMB, starbursts (SBs), and active galactic nuclei (AGNs); (ii) molecular clouds in dense or inclined galaxies can overlap; (iii) compact gas can attain a smooth distribution in the densest part of disks; (iv) CO-luminosities scale with metallicity changes between galaxies; (v) CO-luminosities are always detected against the CMB. We analyze the relative importance of these effects and predict the cosmic evolution of the CO-LFs. The most notable conclusion is that the detection of regular galaxies (i.e. no AGN, no massive SB) at high z>7 in CO-emission will be dramatically hindered by the weak contrast against the CMB, in contradiction to earlier claims that CMB-heating will ease the detection of high-redshift CO. The full simulation of extragalactic CO-lines and the predicted CO-LFs at any redshift can be accessed online, prior registration required} and they should be useful for the modeling of CO-line surveys with future telescopes, such as ALMA, the LMT, or the SKA.

Authors: Obreschkow, D; Heywood, I; Kloeckner, H; Rawlings, S

• Publication status: Published
• Publisher: Institute of Physics Publishing
• Journal: ApJ
• Volume: 702
• Issue: 2
• Pages: 1321-1335
• Publication date: 2009-07-17
• DOI: 10.1088/0004-637X/702/2/1321
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: astro-ph.CO; astro-ph.GA