gravitational lensing and the problem of faint galaxies alicia berciano alba (jive / kapteyn...
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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
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