1. Gravitational lensing and the problem of faint galaxies Alicia Berciano Alba (JIVE / Kapteyn institute) Mike Garret (JIVE) Leon Koopmans (Kapteyn institute)

2. The problem of sub-mm Galaxies Hughes et al. (Nature 1998)

3. Nature of sub-mm galaxies SCUBA sources = faint dusty star forming galaxies at high z obscured in optical but not in sub-mm and radio At low z  rare objects (M82, Arp220) At high z  the peak is shifted from FIR to sub-mm electrons die like SN Massive stars a lot of dust A lot of uv-radiation FIR Emission

4. Solution: Gravitational lensing as a telescope If we are lucky… very massive object Between sub-mm source and us several images with magnification in size and flux density we can “see” the iceberg below the sea strong GL effect YES, we are : Abell 2218 GL in clusters of galaxies MS0451.6-0305

5. Abell 2218 Sources: Star forming galaxy (z=2.516)  3 images arc#289(Z=1.034) arc#289 Kneib et al. (2004) Data: Optical images (HST) NIR imagin / spectroscopy (WHT/ Keck) Sub-mm (SCUBA 850 mm) Radio (VLA 8.2 GHz / WSRT 1.4 GHz) Kneib et al. (2004) Knudsen (2004) Sheth et al. (2004) Garrett et al. (2005)

6. MS0451.6-0305 Borys et al. (2004) DATA - Optical image (HST) - VLT (Very Large Telescope) spectrocopy - Sub-mm (SCUBA 850 mm)  solid line - X-ray (Chandra)  dotted line - X-ray point sources (Molar et al. 2002)  croses - NIR (Near Infra-Red) objects  circles SOURCES - 2 lens images of a fold arc (ARC1)  LBG - 3 lens images of 2 objects (B/C)  2 EROs - P  very blue object

7. Trying to find the radio counterpart… Cluster´s centre • Data • From VLA archive • Freq = 1.36 GHz (L-band) AB config. • Obs time (”on-source” ) = 7h 46min • 1s rms = 9 mJy / beam

8. The • Comparison • Between • Sub-mm • and • radio alineation problem • Radio emission is coincident with the sub-mm emission & extended on the same angular scale. • Radio & sub-mm emission due to the same source(s) • Two emissions magnified by GL effect • Radio  St > 100 mJy (few tens mJy) • Sub-mm  St >>10 mJy (few mJy) • S850 mm / S1.4 Ghz ~ 100  as we expect

9. Borys et al. conclusions ARC1 (LBG) • Sources of sub-mm emission B/C pair (EROs) 2/3 of the total flux • Borys et al. can´t • reproduce • the sub-mm emission!!!

10. OurpreliminarResults • B1/C1 at the edge of the radio emission  maybe not related with the emissions? • We can explain the elongation in the top of sub-mm emission  new radio source • We can explain the gap in the borys simulation  3 new radio sources • No radio detection in B3/C3  is not a surprise

11. Future Work • Obtain the HST and SCUBA images from Borys to make a correct alignament with the radio image • know the error positions of ARC1 and EROs • Try to reproduce the detailed morphology of the radio map with a similar simulation used by Borys • Understand what´s going on with the radio image in terms of lensing model • Make a tapered low resolution and higher resolution uniformly weighted image of the radio data • Look for more data in the VLA rachive (5 and 8 GHz) • Apply for VLA data in A configuration  1” resolution (instead of the actual 5” resolution)

12. Conclusions • We detect the second multiply imaged radio emission associated with massive cluster lensing • We find 1 radio source to explain the the excess of scuba emission in the top left part of the image • We find 3 radio sources to explain the gap in Bory´s simulation • We can´t be sure about the contribution of the B/C pair in the radio and sub-mm emissions The answer (I hope) in the next meeting…

14. Summary The only way to detect this sources is through the GL effect • We have 2 systems with sub-mm and radio to study their nature  we are looking for more • We must finish the analysis of radio data in MS0451.6-0305 • The case of MS0451.6-0305 is more complex than A2218  we need better radio images to know the nature of the sub-mm emmision