Transcript Gravitational lensing and the problem of faint galaxies

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
obscured in optical but not in sub-mm and radio
At
(M82,
Arp220)
At low
highz zrare
theobjects
peak is
shifted
from FIR to sub-mm
die like SN
a lot of
dust
FIR
Emission
electrons
Massive stars
A lot of
uv-radiation
Solution: Gravitational lensing as a
telescope
If we are lucky…
very massive
object
Between
sub-mm
source
and us
stron
g
GL
effect
several images
with
magnification
in size
and
flux density
YES, we are :
GL in clusters of galaxies
Abell 2218
MS0451.6-0305
we can
“see”
the iceberg
below
the sea
Abell 2218
Sources:
Star forming galaxy (z=2.516)  3 images
arc#289 (Z=1.034)
VLA
(8.2 GHz)
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)
SMM intrinsic flux
density
3 mJy
1s rms Noise
6 mJy/beam
Integration time
with lensing
24 h
(4s)
Integration time
without lensing
100 days
(5s)
Kneib et al. (2004)
Knudsen (2004)
Sheth et al. (2004)
Garrett et al. (2005)
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
MS0451.6-0305
SOURCES
- 2 lens images of a fold arc (ARC1)  LBG
- 3 lens images of 2 objects (B/C)  2 EROs
- P  very blue object
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
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
Borys et al. conclusions
•
ARC1 (LBG)
Sources of sub-mm emission
B/C pair (EROs)
Borys et al. can´t
reproduce
the sub-mm
emission!!!
2/3 of the total flux
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
The
answer
(I hope)the the excess
• We find 1 radio
source
to explain
of scuba emission
the meeting…
top left part of the image
in theinnext
• 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
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