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 ofuv-radiationFIR

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

strong

GL effect

several images with

magnification in size

and flux density

we can “see”

the iceberg below the sea

MS0451.6-0305

Abell 2218GL in clusters of galaxies

Abell 2218Sources:

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 Noise 6 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

MS0451.6-0305 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-1rms = 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)

S850 m / S1.4 Ghz ~ 100 as we expect

The Comparison

BetweenSub-mm

and radio

alineationproblem

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!!!

Ourpreliminar

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…

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