<=== observer ===>
"LMETCALF",\
"Metcalfe, L.",\
"",\
"SAI",\
"ESTEC",\
"Keplerlaan 1",\
"2200 AG",\
"Noordwijk",\
"The Netherlands",\
"31 1719 83616",\
"31 1719 85434",\
"lmetcalf@isosa6.estec.esa.nl"
<=== proposal ===>
"ARCS",1,5,\
{"gravitational lensing","galaxy clusters"},\
{"B. Altieri","B.Mc. Breen","K. Leech", "B. Schulz"}
<=== title ===>
ISO Observations of Gravitationally Lensed Arcs:
<=== abstract ===>
SCIENTIFIC ABSTRACT
We propose deep imaging with ISOCAM of fields containing gravitationally lensed
galaxies (giant arcs) with redshifts up to 2.2. In this way we take advantage
of the vast ``gravitational telescopes'' constituted by distant galaxy clusters
to study the infrared flux from the lensed galaxies themselves and to probe
these fields to high redshift for other, IR luminous, lensed objects.
These observations will:
a) - generate infrared images of known giant arcs.
b) - provide the infrared flux of the giant arcs and hence extend our knowledge
of the properties of field galaxies at high redshift.
c) - search for infrared arcs that would be produced by a primeval population of
infrared luminous galaxies.
d) - will be complementary to ISOCAM proposals to make deep integrations on
galaxy clusters.
OBSERVATION SUMMARY
Given the R magnitudes for these arcs, and assuming normal galaxy colours, we
can calculate their flux in the M band (4.8 microns). This is, for the arcs
to be studied here, in the range 3 to 12 microJanskys per square arcsecond.
We will use CAM in micro--scanning mode (4x4 microscan, 1.3 pixel step size) in
the following configurations, for all targets:
- filter LW1 (4 to 5 microns), on chip integration time (tint) 20 seconds, pixel
f.o.v. 1.5 arcseconds, exposure time 3600 seconds and
- filter LW6 (7 to 8.5 microns), on chip integration time (tint) 20 seconds,
pixel f.o.v. 3 arcseconds, exposure time 3600 seconds.
These configurations will allow us to reach S/N ratios of 3 and 11.5 respectiv-
ely, in the two configurations described above, for arcs having fluxes of 8
microJanskys per square arcsecond. Therfore, while this is a difficult measure-
ment, it is nonetheless well within the bounds of possibility that the arcs
can be detected with CAM given its sensitivity.
Quite apart from the sensitivity of CAM, another potentially serious constraint
is the possibility of confusion of the IR arc images with foreground galaxies in
the lensing cluster. The diameter of the ISO diffraction spot is roughly, in
arcseconds, 0.84 times the wavelength. This implies diffraction spot sizes of
3.8 and 6.5 arcsedonds, in the filters chosen here. We have therfore chosen the
1.5 arcsecond per pixel p.f.o.v. with the LW1 filter and the 3 arsecond p.f.o.v.
with the LW6 filter. These allow optimal sampling of the PSF for the wavelenghts
employed and should avoid serious confusion with nearby sources for the arcs
studied here except for the case of A370, where careful modelling of the
foreground cluster will be necessary in order to compensate, during data
reduction, for source confusion.
Observing between 4 and 5 microns reduces flat-fielding problems inherent at
longer wavelengths where the background is higher. The choice of the LW1 filter
and the 1.5 arcsec per pixel field of view maximises the resolution and the
sampling of the PSF, vital if the confusion limit is to be avoided. The
combination of the 3 arcsecond p.f.o.v. and the LW6 filter allows us to take
advantage of any growth in the IR flux going further into the IR (if the lensed
galaxies are AGNs) and provides greater sensitivity due to the larger pixel
size.
For the 1.5" p.f.o.v the Zodiacal background flux is comparable with the source
flux (both are about 1 ADU per readout). For the 3" p.f.o.v, the Zodiacal
background flux is much greater than the source flux. In both cases then,
detector responsive transients, which can occur when a source moves over the
array, should not be too severe, since the array sees essentially uniform
illumination, even during microscanning, after the initial transient at source
acquisition. The transient behaviour of the detector should be better for the
higher pixel signal encountered with the higher background seen in the LW6
filter.
Micro-scanning reduces the impact of residual flat-fielding noise and enhances
the possibilities for later application of super-resolution techniques.
<=== scientific_justification ===>
Time distribution for spring launch targets:
Team top 0% second 75%% last 25%
SOT : 00000 22200 7404
Time distribution for autumn launch targets:
Team top 0% second 75%% last 25%
SOT : 00000 22200 7404
<=== autumn_launch_targets ===>
1, "CAM01", 2.0, "N", "A370_arc", 2.62236, -1.79806, 1950, 0., 0., 3780, 2
2, "CAM01", 2.0, "N", "A370_arc", 2.62236, -1.79806, 1950, 0., 0., 3620, 0
3, "CAM01", 2.0, "N", "MS1237_arc", 21.62222, -23.88888, 1950, 0., 0., 3780, 4
4, "CAM01", 2.0, "N", "MS1237_arc", 21.62222, -23.88888, 1950, 0., 0., 3620, 0
5, "CAM01", 2.0, "N", "MS0440_arc", 4.67742, 2.08111, 1950, 0., 0., 3780, 6
6, "CAM01", 2.0, "N", "MS0440_arc", 4.67742, 2.08111, 1950, 0., 0., 3620, 0
7, "CAM01", 3.0, "N", "CL2244_arc", 22.74417, -2.35708, 1950, 0., 0., 3780, 8
8, "CAM01", 3.0, "N", "CL2244_arc", 22.74417, -2.35708, 1950, 0., 0., 3620, 0
<=== spring_launch_targets ===>
1, "CAM01", 2.0, "N", "A370_arc", 2.62236, -1.79806, 1950, 0., 0., 3780, 2
2, "CAM01", 2.0, "N", "A370_arc", 2.62236, -1.79806, 1950, 0., 0., 3620, 0
3, "CAM01", 2.0, "N", "MS2137_arc", 21.62222, -23.88888, 1950, 0., 0., 3780, 4
4, "CAM01", 2.0, "N", "MS2137_arc", 21.62222, -23.88888, 1950, 0., 0., 3620, 0
5, "CAM01", 2.0, "N", "MS0440_arc", 4.67742, 2.08111, 1950, 0., 0., 3780, 6
6, "CAM01", 2.0, "N", "MS0440_arc", 4.67742, 2.08111, 1950, 0., 0., 3620, 0
7, "CAM01", 3.0, "N", "CL2244_arc", 22.74417, -2.35708, 1950, 0., 0., 3780, 8
8, "CAM01", 3.0, "N", "CL2244_arc", 22.74417, -2.35708, 1950, 0., 0., 3620, 0