2.  Extragalactic radio surveys at 1.4 GHz  An overview of the survey (hereafter UDS20) and some results  The nature of the radio population

3. Sensitive to star-forming galaxies (SFGs) and active galactic nuclei (AGNs) Unaffected by dust obscuration Dust-enshrouded SFGs Torus-obscured AGNs High-resolution proxy for submillimetre and far-infrared (FIR) observations exploits the FIR-radio correlation Ikarashi et al. 2010, Michalowski et al. 2011 (in prep.) Condon 1992 Simpson C. et al., 2006, MNRAS,372, 741

4. Mosaic of 14 pointings (red circles) in the Subaru/XMM- Newton Deep Survey Field ~ 1.3 deg 2 160 hrs in A,B and C->DnC configurations of the NRAO Very Large Array at 1.4 GHz High resolution ≈ 1.82” Contours at 8 (blue), 10 (red), 15 (green), 20 (gold), 30 (purple), 50 (cyan) & 100 (yellow) μJy beam -1 UDS rms noise <8 μJy beam -1 towards the centre and Central 0.7 deg 2 - ~10 μJy beam -1 Coincides with UKIDSS Ultra Deep Survey (UDS) region Yielded a 4σ (local rms) catalogue with 6861 sources

7. AGN AGN L 1.4 GHz > 10 24.5 W Hz -1 Robust AGN/SFG discrimination needed! Faint radio population consists of a mix of AGNs and SFGs

8. AGN O X-ray sources * * IRAC colour-colour plot (Stern et al. 2005)

9. IRAC-MIPS colour-colour plot (Ivison et al. 2004)

10.  Extragalactic radio surveys play an important role in understanding galaxy evolution  Sensitive to synchrotron emission from SFGs and AGNs  UDS20 has deep, high-resolution radio data  Complemented by multi-wavelength data, this should allow for the study of the faint radio population  The faint radio population is believed to consist of a mix of AGNs and SFGs  Robust starburst/AGN diagnostics needed to disentangle the two – work in progress…