Extragalactic radio surveys at 1.4 GHz

An overview of the survey (hereafter UDS20) and some results

The nature of the radio population

• 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

•Mosaic of 14 pointings (red circles) in the Subaru/XMM-Newton Deep Survey Field ~ 1.3 deg2

• 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 deg2 - ~10 μJy beam-1

•Coincides with UKIDSS Ultra Deep Survey (UDS) region

•Yielded a 4σ (local rms) catalogue with 6861 sources

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dN

dS45μJy−1000μJydA=12.7 ± 9.4 Sν

−2.41±0.09

AGN

AGN

AGN L1.4 GHz > 1024.5 W Hz-1 Robust AGN/SFG discrimination needed!

Faint radio population consists of a mix of AGNs and SFGs

AGN AGNO X-ray sources

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IRAC colour-colour plot (Stern et al. 2005)

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

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…