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Date: Fri, 27 Aug 1999 10:58:35 +0200
To: fahlman@cfht.hawaii.edu
From: Laurent Vigroux <vigroux@discovery.saclay.cea.fr>
Subject: MEGACAM proposal and Survey group
Cc: John.Hutchings@hia.nrc.ca
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Proposal for a combined MEGACAM/XMM/VIRMOS Large Scale Structure survey.
---------------------------------------------------------

PROPOSERS:

PI: Marguerite PIERRE CEA/SAp mpierre@cea.fr

Co-I:

CEA/SAp  Saclay
O. Boulade
R. Teyssier
L. Vigroux

IAP Paris
B. Fort
Y. Mellier
P. Petitjean

LAS Marseille
V. Lebrun
O. Le Fevre
A. Mazure


CONTEXT:

In the context of the XMM Announcement of Opportunity AO-1, we have proposed
to perform an X-ray survey covering an area of 8x8 sq.deg, centered on the 2
sq.deg area that we will observe as part of our guaranteed time (XMM Medium
Deep Survey). The sensitivity will be 5E-15 erg/s/cm2 in the [0.5-2]keV band.
Some 700 galaxy clusters are expected out to z=1 and 10 times as many
QSOs/AGNs out to z~3. The complete cluster/goup population will be detected
out to z=0.5.

The main goal of the survey is to study the large scale structures underlined
by clusters and AGN out to z=1. For the first time, it will be possible to
compute the cluster 2pt-correlation function in the 0.5<z<1 range.

Another key aspect will be the systematic search for distant clusters beyond
z >1 since the X-ray sensitivity will enable the detection of massive
clusters out to z~2, if they exist.

FULL SCIENTIFIC AND TECHNICAL INFORMATION ABOUT THIS PROJECT AS WELL AS
DETAILED SIMULATIONS CAN BE FOUND AT:
http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/index_e.html


PROPOSED MEGACAM SURVEY:

We propose to perform a MEGACAM optical survey associated to the XMM survey
in order to obtain the necessary X-ray source identification. Subsequent
spectroscopic follow-up will be done at the VIRMOS/VLT and other 8m class
telescopes accessible to the consortium. The optical survey of the central 2
sq.deg area has already started using CFH12K.

This survey will also enable a unique detailed study of the evolutionary
X-ray/optical properties of the cluster and QSO population. On the same area,
we plan to combine the X-ray survey with a weak lensing analysis (using the
MEGACAM data, cf proposal by Y. Mellier) and further, with a
Sunyaev-Zel'dovich survey
(http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/sz_srv_e.html). The whole
data set will provide an unprecedented mapping of the mass distribution in
the universe using three independent methods and for truly cosmological
distances.

The optical survey can also be used in a "standalone mode" in order to study
rich clusters at high redshift (about 400 Abell R>=1 clusters are expected in
64 sq.deg with 0.5<z<1) and filaments between clusters. It will also allow
the study of the large scale structure clustering and two-point correlation
function. The photometric redshifts will be used to estimate the redshift of
the galaxies, identify galaxy clusters and optimize the weak lensing
analysis.

Observations will be performed in the UBVRI bands at a depth of I ~ 25 , thus
ensuring deep high quality images. Data pipelines and processing are
currently being developed by the TERAPIX consortium; this will provide object
catalogues and astrometric positions for the entire surveyed region.

1) Location

We have selected an equatorial region on the basis of XMM visibility and low
NH criteria:
		8x8 sq.deg. around RA = 2h20 Dec=-5 deg.
(more details on
http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/srv_char_e.html)

2) Sensitivity

AB magnitude	Megacam exposure time

I 24.8			1h
R 25.4			1h
V 25.4    		1h30
B 25.7			2h
(U 26.1			~5h)


The above sensitivities are chosen in order to: (1) provide the
identifications of the X-ray sources (mainly I band), (2) enhance  the galaxy
density contrast using color criteria in the case of distant galaxy clusters
(z~1), (3) provide preliminary photometric redshifts for galaxies (0<z<1),
(4) enable a detailed X/optical evolutionary analysis of the properties of
QSO and clusters.

3) Time scale

The MEGACAM/XMM/VIRMOS survey is expected to start in 2001 and to end-up in
2003.

************************************************************

PROPOSED SCIENTIST FOR THE MEGACAM SURVEY WORKING GROUP:

The proposed scientist for the MEGACAM Survey Working Group is Laurent Vigroux


************************************************************

Declaration of interest to serve in the MEGACAM Survey Working Group

Since several years, I have a strong interest in wide field imaging. I
alaways wanted to push scientific projects making use of the large
detectors available today. I originally proposed the Large Imaging
Telescope (LITE) in 1993 to ESO, without succes. It was too early, then
with Bernard Fort and yannick Mellier, we send the MEGACAM proposal to CFH.
later on, I withdraw the CEA MEGACAM PI responsibility  and leave it to
Olivier Boulade instead. the main reason was that I had not enough time to
follow all the technical developments of MEGACAM and Terapix. Olivier was
actually doing this job for quite a while. from a management point of view,
it was much better to hav Olivier Boulade officially PI rather than doing
the work but without the official responsibility. However, I am stil very
interested in the science to be done with MEGACAM, and I was still involved
in the discussion about the survey time. I have pushed hard to get this
working group set up, and I volunteer to serve on him.


Laurent Vigroux