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

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

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

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

Abell 2218 Sources: Star forming galaxy (z=2.516)  3 images arc#289 (Z=1.034) Data: Optical images (HST) NIR imagin / spectroscopy (WHT/ Keck) Sub-mm (SCUBA 850  m) Radio (VLA 8.2 GHz / WSRT 1.4 GHz) VLA (8.2 GHz) SMM intrinsic flux density 3  Jy 1  rms Noise6  Jy/beam Integration time with lensing 24 h (4  ) Integration time without lensing 100 days (5  ) Garrett et al. (2005) Kneib et al. (2004) Knudsen (2004) Sheth et al. (2004) Kneib et al. (2004) arc#289

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 MS Borys et al. (2004)

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

 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  Jy (few tens  Jy) Sub-mm  St >>10 mJy (few mJy) S 850  m / S 1.4 Ghz ~ 100  as we expect The Comparison Between Sub-mm and radio alineation problem

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

Our preliminar Results 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

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)

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…

Our preliminar results B1/C1 are not in the peak of the radio image The peak of the radio image have the same orientation as the sub-mm image We can explain the gap in the Borys´ simulation  2 radio images The middle radio source could be associated with one of the Tanaka´s EROs

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 MS The case of MS is more complex than A2218  we need better radio images to know the nature of the sub-mm emmision

The problem of sub-mm Galaxies Faint SMG dominate energetically the cosmic far-infrared background (Knudsen 2004) SCUBA-detected galaxies are often extremely faint in the optical because the dust responsible for the sub-mm luminosity absorbs radiation at other wavelenghts  redshifts, morphologies and spectral energy distributions are dificult to obtain With current sensitivity limits, actual telescopes can only detect the bright tail of the SMG population Flux density of SMG  < 2mJy

WSRT 1.4 GHz Contours= -3, 3, 5, 10, 20,  noise level = 15  Jy / beam Integration time=12 h VLA 8.2 GHz Contours = -3, 3, 4, 7,  noise level = 6  -Jy / beam Integration time= 24 h Garrett et al Abell 2218 (radio)

Abell 2218 Sources: Star forming galaxy (z=2.516)  3 images arc#289 (Z=1.034) Data: Optical images (HST) NIR imagin / spectroscopy (WHT/ Keck) Sub-mm (SCUBA 850 mm) Radio (VLA 8.2 GHz / WSRT 1.4 GHz) SCUBA (850 mJy) WSRT (1.4 GHz) VLA (8.2 GHz) SMM intrinsic flux density 0.8 mJy 14  Jy3  Jy Noise2 mJy 15  Jy / beam6  Jy / beam Integration time 39.7 h12 h (24 days)24 h (36 days) Garrett et al. (2005) Kneib et al. (2004) Knudsen et al. (2004) Sheth et al. (2004)

Abell 2218 (sub-mm) Sub-mm sources (SCUBA 850 mJy) -Star forming galaxy (z=2.516)  3 images -SMM J (Z=1.034)  arc#289 Kneib et al. (2004b) SMM A SMM B SMM C Arc#289 Observed total flux density M-JyMagnif SMM-A11 m-Jy14 SMM-B17 m-Jy22 SMM-C9 m-Jy9 Arc# m-Jy7 Knudsen (2004)

Abell 2218 Sources: Star forming galaxy (z=2.516)  3 images arc#289 (Z=1.034) Data: Optical images (HST) NIR imagin / spectroscopy (WHT/ Keck) Sub-mm (SCUBA 850  m) Radio (VLA 8.2 GHz / WSRT 1.4 GHz) SCUBA (850 mJy) WSRT (1.4 GHz) VLA (8.2 GHz) SMM intrinsic flux density 0.8 mJy 14  Jy3  Jy 1  rms Noise 1.5 mJy/beam 15  Jy/beam6  Jy/beam Integration time with lensing 39.7 h (6  ) 12 h (7  ) 24 h (4  ) Integration time without lensing 145 days (5  ) 12.5 diays (5  ) 100 days (5  ) Garrett et al. (2005) Kneib et al. (2004) Knudsen (2004) Sheth et al. (2004) Kneib et al. (2004) arc#289

Nature of the sources ARC1 VLT spectroscopy  LBG (Lyman Break Galaxy) at z=2.911 Lens model (kneib et al / 96)  identification of ARC1 ci B/C pair NIR color–magnitude diagram  2 EROs Lens model  identification of the 3 images with correct parity if B/C pair it´s at z=2.85 problem ARC1 and B/C at aprox. same z  separation in source plane =10 kpc  3 interacting galaxies  origin of a violent starburst revealed by the strong sub-mm emission No x-ray detection of C2

Which is the source of the sum-mm emmision?? -Connection between sub-mm galaxies and EROs well stablished -ARC1 spectrum similar to the most absorved LBG  reddest and most dust-extinted Simulation - blank SCUBA-like map with sources in B1,B2,B3, ARC1 - relative fluxes fixed by lensing model predictions - the peak flux needs to match the observations  12 mJy - We need the two sources to expain the sub-mm observations - 2/3 of sub-mm flux is coming from the EROs Conclusions dusty starbust 4” to the NE of B3/C3 (Tanaka et al. 2003) They CAN´T reproduce the sub-mm observation only with this 2 sources

More problems…