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Studying Clusters of Galaxies with IFUs
Studying Galaxy Clusters with IFUs
Marco Scodeggio, Bianca Garilli, Dario Maccagni,
Micol Bolzonella, Paolo Franzetti, Alessandra
Zanichelli
IASF - CNR, Milano, Italy IRA - CNR, Bologna,
Italy
Euro3D Kick-off Meeting, IAC July 2002
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Why study clusters of galaxies
1. for themselves, as tracers of the large-scale
distribution of matter in the Universe 2. for
the galaxies they "contain", to study the
processes of galaxy formation and evolution
Euro3D Kick-off Meeting, IAC July 2002
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REFLEX Clusters (Guzzo 2002)
2dF Galaxies (Peacock et al. 2001)
Euro3D Kick-off Meeting, IAC July 2002
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Despite the different density of objects,
galaxies and clusters trace the same 3D
structures, with clusters covering (potentially)
larger volumes
Notice how the best fitting model is just one,
the same for galaxies and for clusters,
scaled to the different "mass" of these objects
(Guzzo 2002)
Euro3D Kick-off Meeting, IAC July 2002
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Evolution of cluster abundance with redshift
No evolution for a low W0 Universe
Strong evolution for a high W0 Universe
(Bahcall Fan 1997)
Euro3D Kick-off Meeting, IAC July 2002
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Galaxy properties the Fundamental Plane
From the Virial theorem we have GM/ltRgt
kEltV2gt/2 The observed quantities can be related
to the physical ones via Re kRltRgt s2
kVltV2gt L kLRe2 S And one derives the
relation Re kFP s2 S-1 (M/L)-1 To be
compared with the observed one
Log Re a Log s b Log S with coefficients
a Y 1.5 and b Y - 0.85
Euro3D Kick-off Meeting, IAC July 2002
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Local Universe
High -z Universe
(Kelson et al. 1997)
(Scodeggio et al. 1997)
Euro3D Kick-off Meeting, IAC July 2002
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Evolution of the M/L ratio with redshift,
and implications on the formation epoch of
cluster elliptical galaxies
(van Dokkum 2001)
Euro3D Kick-off Meeting, IAC July 2002
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How to study clusters of galaxies
1. from a survey, build a candidates
sample 2. confirm spectroscopically the
candidates (and get a measure of the cluster
redshift) 3. study in detail the cluster and
its galaxies (obtain spectra for many
cluster galaxies)
Euro3D Kick-off Meeting, IAC July 2002
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The spectroscopic work is trivial at low
redshift (z lt 0.1) but becomes very difficult at
medium / high redshift (z gt 0.5)
(Dickinson 1997)
Euro3D Kick-off Meeting, IAC July 2002
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Targetting cluster galaxies the MOS case
Euro3D Kick-off Meeting, IAC July 2002
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Targetting cluster galaxies the IFU case
Euro3D Kick-off Meeting, IAC July 2002
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IFU dominates over MOS for clusters work
Same limiting magnitude
Same exposure time
Euro3D Kick-off Meeting, IAC July 2002
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Conclusions
1. MOS observations are not well suited for
studying medium/ high redshift clusters (z gt
0.5), as they not even always provide enough
redshifts to confirm the cluster presence 2. IFU
observations, on the contrary, always provide
enough data to confirm the cluster presence,
and most of the time also enough data to
study the cluster properties and build a
significant sample of cluster galaxies 3. The
number of target cluster galaxies in deep IFU
observations depends very mildly on the cluster
redshift
Euro3D Kick-off Meeting, IAC July 2002
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To be continued....
Euro3D Kick-off Meeting, IAC July 2002