Seymour, N. and Huynh, M. and Dwelly, T. and Symeonidis, M. and Hopkins, A. and McHardy, I. M. and Page, M. J. and Rieke, G. (2009) Investigating the far-IR/radio correlation of star-forming Galaxies to z= 3. Monthly Notices of the Royal Astronomical Society, 398 (3). pp. 1573-1581. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20091001-110942836
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In order to examine the far-infrared (far-IR)/radio correlation at high redshift, we have studied the Spitzer 70 μm /far-IR properties of sub-mJy radio sources from the 13^H XMM–Newton/Chandra Deep Field by redshift and galaxy type: active galactic nucleus (AGN) or star-forming galaxy (SFG). We directly detect 70 μm counterparts (at >3σ significance) for 22.5 per cent (92/408) of the radio sources, while for the rest we perform stacking analysis by redshift and galaxy type. For the sources detected at 70 μm , we find that the median and scatter of the observed flux density ratio, q_(70), are similar to previous results in the literature, but with a slight decrease in q_(70) towards higher redshifts. Of the radio sources detected at 70 μm 8/92 were already classified as AGN, but two of which maybe SFGs. For the stacked sources, we obtain a detection for the SFGs at every redshift bin which implies they have mean flux densities a factor ~5 below the original 70 μm detection limit. For the stacked AGN, we obtain a detection only in our highest redshift bin (1 ≤ z ≤ 5) where we may be sampling hot dust associated with the AGN at rest frame 12−35 μm . The combined observed mean value of q_(70) for the SFGs (detected and non-detected at 70 μm) decreases gradually with redshift, consistent with tracks derived from empirical spectral energy distributions (SEDs) of local SFGs. Upon closer inspection and when comparing with tracks of appropriate luminosity, the values of q_(70) broadly agree at low redshift. However, at z ~ 1, the observed q_(70) [for ultraluminous infrared galaxies (ULIRGs)] is 2 σ below the value seen for local ULIRGs tracks, implying a difference in the SED between local and z ~ 1 ULIRGs. At higher redshifts, the convergence of the tracks and the higher uncertainties in q_(70) do not allow us to determine if such a difference persists.
|Additional Information:||© 2009 RAS. Accepted 2009 June 9. Received 2009 June 8; in original form 2008 December 23. We thank the anonymous reviewer for many helpful comments that improved the clarity and presentation of this paper. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work was partially supported by JPL/Caltech contract 1255094 to the University of Arizona.|
|Subject Keywords:||galaxies: evolution; starburst; infrared: galaxies; radio continuum: galaxies|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||05 Oct 2009 16:54|
|Last Modified:||26 Dec 2012 11:26|
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