A prelude to SKA. High-resolution mapping of the ujy radio population. Ian Smail ICC, Durham University Tom Muxlow, JBCA, University of Manchester

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1 QuickTime and a decompressor are needed to see this picture. The University of Manchester Jodrell Bank Observatory A prelude to SKA The e-merge Legacy Survey: High-resolution mapping of the ujy radio population Ian Smail ICC, Durham University Tom Muxlow, JBCA, University of Manchester SKA, 3/10

2 Outline The key role of sensitive radio surveys in tracking the SF history of the Universe MERLIN studies of ujy radio sources Resolving SF in starburst galaxies at z~1 SF and AGN activity in sub-mm galaxies at z~2 Statistical properties of the radio population down to ~µjy The e-merge Legacy program: An ultra-deep e-merlin study of the ujy population What might we learn from e-merlin (and SKA)?

3 SFH of the Universe & FIR-Radio Correlation Star formation history of the Universe is a fundamental constraint on models of galaxy formation and evolution Radio continuum luminosity correlates with far-infrared emission, which traces star formation in galaxies. Radio is thus an excellent tracer of (obscured) star formation (need to remove AGN & calibrate FIR-radio vs z)

4 ujy Radio Sources Below ~100µJy the radio population becomes dominated by (apparently) star-forming galaxies, typical at z<1.5 with inferred SF rates many times those seen in nearby galaxies Around 15% of the population lie at higher redshifts, many of which are also identified as sub-mm sources.

5 MERLIN observation of HDF-N Muxlow et al 2005 Size VLA detected 92 sources at L-Band in a arcmin field centred on the HDF-N above a completeness limit of 40uJy. Combination of L-Band MERLIN & VLA observations can resolve the radio emission in the majority of sources, typical sizes are ~0.8 (~5kpc).

6 MERLIN & high-z ULIRGs Chapman et al. 2004; Casey et al High-res radio imaging a powerful diagnostic of AGN and star formation in the diverse high-z ULIRG populations at z~2. 65% show resolved/multiple radio morphologies on ~8kpc (1 ) scales: SF arises in extended, obscured regions that are forming stars at starburst limit (40Mo/kpc 2 /yr) Some AGN found masquerading as UV-bright starbursts

7 Statistical Studies of ujy Sources To probe the even fainter population: Radio emission at the level of a few µjy can be statistically detected from faint galaxies z<26 by stacking Radio emission around 13,000 z-band galaxies [excluding bright sources and close galaxy pairs] Identify z~24-26 galaxies as extended radio sources with properties similar to the SF galaxies studied individually at >40uJy How can we study these faint sources individually? Muxlow et al 2007

8 The e-merlin Galaxy Evolution Survey (e-merge) A two-tier e-merlin Legacy proposal the e-merge Survey is designed to study the formation and evolution of starforming galaxies and AGN out to z > 5 and disentangle their activity using high resolution multi-frequency observations Tier 0 Imaging radio emission from normal galaxies out to z ~ 5 Deep imaging through a cluster lens to utilise gravitational amplification Tier 1 A very deep directed survey of the μjy radio source population Deep imaging of the µjy radio source population in GOODS-N >60 co-is from 9 countries Coordinators: Tom Muxlow [JBCA, Tier 1], Ian Smail [ICC, Tier 0], 918 hours of e-merlin time allocated: (Tier 0-180hr, L-band / Tier 1-360hr, L-band; 378hr, C-band)

9 Tier 1: New Ultra-Deep Study of GOODS-N e-merge will exceed the depth of the existing MERLIN combination map in just 24 hours of on-source integration. L-Band: Single pointing centre, 20 full tracks including LT+40hr EVLA Central 10 arcminute field 1σ ~ 300nJy/beam Outer 30 arcminute field 1σ ~ 700nJy/beam cf Original study:18 full tracks +42 hours VLA A-array Central 10 arcminute field only 1σ ~ 3.3 µjy/beam sources >40µJy 60 starburst galaxies 32 AGN systems

10 Tier 1: New Ultra-Deep Study of GOODS-N e-merge will exceed the depth of the existing MERLIN combination map in just 24 hours of on-source integration. L-Band: Single pointing centre, 20 full tracks including LT+40hr EVLA Central 10 arcminute field 1σ ~ 300nJy/beam Outer 30 arcminute field 1σ ~ 700nJy/beam e-merge will image ~850 individual starburst and AGN with an angular resolution of ~150mas, complete to ~3µJy (>10 times deeper than the original study) In the surrounding 800 square arcmins, e-merge will image ~2500 star-forming galaxies and ~1200 AGN with >6µJy :92 >50x increase in source numbers

11 Tier 1: C-band Study of GOODS-N New C-Band image: 7 pointing centres each with 3 long tracks Mosaic pattern set for Lovell 3 beam Inner 6 1σ ~ 500nJy/beam σ ~ 700nJy/beam Resolution 40 mas Additional C (and L)-Band EVLA data (42hrs) increases the sensitivity by a factor~1.5 and adds short-spacing uv-coverage to recover the very heavily resolved radio structures with sizes > 1

12 Tier 1: C-band Study of GOODS-N New C-Band image: 7 pointing centres each with 3 long tracks Mosaic pattern set for Lovell 3 beam The Inner ultra-deep 6 1σ ~ C-Band 500nJy/beam image will: Map 6-10 any 1σ star-forming ~ 700nJy/beam regions in even greater detail Separate Resolution the 40 AGN mas and starburst components of the radio emission Additional C (and Study the role that the AGN play in controlling star-formation via L)-Band EVLA data feedback - on sub-kpc scales for several hundred galaxies (42hrs) increases Produce the sensitivity spectral maps by for >30uJy sources a factor~1.5 and adds short-spacing uv-coverage to recover the very heavily resolved radio structures with sizes > 1

13 Tier 0: Detecting sub-1ujy galaxies A single 180-hr L-band pointing on strong lensing cluster A2218 (z=0.18). Starburst Sub-mm 40µJy 3µJy 0.3µJy Expect ~50 amplified sources with intrinsic fluxes as faint as 0.3uJy Measure faint radio counts May include SF galaxies with SFR~30Mo/yr to z~5

14 Serendipity: The Eyelash Nature, 22 March arxiv: Swinbank et al 2010 EVLA Ka CO(1-0) map 32x APEX submm map of MACS : X-ray luminous cluster at z=0.32 Bright source: S 870um =106+/-3mJy (brighter than any other SMG) 32x amplified submm galaxy, ~3mJy = Arp220 (300Mo/yr) at z=2.35

15 Serendipity: The Eyelash Swinbank et al 2010 EVLA Ka CO(1-0) map 32x APEX submm map of MACS : X-ray luminous cluster at z=0.32 Bright source: S 870um =106+/-3mJy (brighter than any other SMG) 32x amplified submm galaxy, ~3mJy = Arp220 (200Mo/yr) at z=2.35

16 Internal Properties 3kpc SMA/VLA/VLT Source plane morphology comprises ~4 (+AGN) clumps across ~2kpc. Highest resoln. beam is 0.2 or 0.02 in source plane: pc SF regions in SMMJ2135 at fixed size are ~10x more luminous at rest-frame 250um than GMCs. Most similar to <1Myr HII regions Has intrinsic L-band flux ~10uJy - demonstrates the level of detail which will come from high-s/n radio maps with <0.1 resolution.