On the Iron content in rich nearby Clusters

1
On the Iron content in rich nearby Clusters

• S. De Grandi
• In collaboration with
• S. Molendi (IASF/CNR),
• S. Ettori (ESO),
• M. Longhetti (INAF/AO Brera)

2
The BeppoSAX sample
22 Galaxy Clusters Nearby objects z 0.02-
0.1 r 20 - 50 of rvir
Cluster Ra Dec Exp(ks)

• A85
• A426 (Perseus)
• A496
• A1795
• A2029
• A2142
• A2199
• A3526 (Centaur.)
• A3562
• A3571
• 2A0335096
• PKS0745-191
• A119
• A754
• A1367
• A1656 (Coma)
• A2256

10.3750 -9.3833 93 49.9550
41.5075 80 68.4071 -13.2619 92 207.2080
26.5917 121 227.7313 5.7439
42 239.5833 27.2333 102 247.1592 39.5514
101 192.2054 -41.3111 70 203.4100 -31.6700
46 206.8667 -32.8656 65 54.6458 9.9650
105 116.8792 -19.2958 92 14.0667 -1.2494
128 137.3421 -9.6878 185 176.1208 19.8339
97 194.8950 27.9450 92 255.9929 78.6419
132 290.3025 43.9494 105 67.8379
-61.4444 76 90.4058 -39.9903 110
243.5917 -60.8722 34 249.5833 -64.3578
49
3
The BeppoSAX sample
NCC
22 Galaxy Clusters Nearby objects z 0.02-
0.1 r 20 - 50 of rvir
10.3750 -9.3833 93 49.9550
41.5075 80 68.4071 -13.2619 92 207.2080
26.5917 121 227.7313 5.7439
42 239.5833 27.2333 102 247.1592 39.5514
101 192.2054 -41.3111 70 203.4100 -31.6700
46 206.8667 -32.8656 65 54.6458 9.9650
105 116.8792 -19.2958 92 14.0667 -1.2494
128 137.3421 -9.6878 185 176.1208 19.8339
97 194.8950 27.9450 92 202.7188 -1.8408
101 255.9929 78.6419 132 290.3025 43.9494
105 67.8379 -61.4444 76 90.4058
-39.9903 110 243.5917 -60.8722
34 249.5833 -64.3578 49

• 10 NCC (cooling in core not important) mean
  profile is flat ( 0.220.02).
• 12 CC (cooling in core present) mean profile
  enhanced at center ( 0.5),
  then similar to that of
  NCC ( 0.270.02).

CC
De Grandi Molendi 2001
4
The ICM Iron mass

• The Fe Mass enclosed within a certain radius
  R is

Since rFe ?ZFeng, from the deprojected ng and
ZFe profiles we compute (Ettori, De Grandi,
Molendi 2002, AA, 391, 841 )
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ICM Iron Mass vs. Lbol and kT
_at_ ?2500
MFe,10 a L44 b a 0.35 0.07 b 0.61
0.07 ?LogMFe 0.12
MFe,10 c kT d c 0.04 0.03 d 1.99
0.40 ?LogMFe 0.29
The MFe-L relation is tighter than the MFe-T
relation.
6
ICM Iron Mass vs. Lbol and kT
_at_ ?2500
Lbol,44 a kT ß a 0.03 0.06
-0.02 ß 3.21 0.60 ?Log Lbol 0.39
L-T like MFe-T shows a large scatter.
We assume that MFe correlates with Lbol and that
MFe-T results from the combination of MFe-Lbol
and Lbol-T.
7

• Accordingly we have computed the parameters and
  scatter for MFe-T from those of MFe-Lbol and
  Lbol-T and compared them with those derived from
  direct fitting of MFe-T.
• We find that the parameters computed from
  MFe-Lbol and Lbol-T are in good agreement with
  those derived from direct fitting of MFe-T
• ?logMFe, expected 0.28
• ?logMFe,best-fit 0.29

_at_ ?2500
We conclude that the most important relation is
the one between MFe and Lbol
8

• We have found that the important relation is MFe
  vs. LX
• LX is an observed quantity related to the gas
  mass LX ? n2gasT1/2
• We investigate the MFe-Mgas relation

MFe,10 a Mgas,13 b a 2.34 0.3 b 0.94
0.09 ?LogMFe 0.14

• The scatter is small ? the MFe-Mgas relation is
  tight
• MFe scales linearly with Mgas

All clusters have the same metallicity
(ZFeMFe/Mgas) ?The mass in stars in clusters
is closely related to Mgas
9

• The XMFeF and XLF have similar shapes
• The slope at the small Fe mass end is larger than
  that at the faint end for the L.
• At the knee (MFe) the XMFeF drops more rapidly
  than the XLF at L.

• From the MFeaLb relation for a given L we can
  derive a reliable estimate of MFe.
• We can use the MFe-L relation to derive a local
  X-ray iron mass function (XMFeF) from the local
  XLF.

XLF
XMFeF
where
To derive the XMFeF we use the XLF from the
REFLEX Cluster Survey (Boehringer et al. 2002)
and the MFe-L0.1-2.4keV relation.
10
Mechanisms that could be responsible of the
central Fe excess in CC
The Iron Mass excess in CC clusters
CC NCC

• Settling of heavy ions towards the center is
  unlikely as tdrift gtgt tHubble
• Ram-pressure stripping of metal rich ISM of
  cluster member galaxies is unlikely (it fails to
  explain the differences btw CC and NCC clusters)
• Ejection of metal-rich gas directly by the BCG
  (via SN-or AGN-driven
  winds)

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The Iron Mass excess in CC clusters
CC

• In the outermost regions, i.e. r/r200 gt 0.2, the
  deprojected Fe abundance of CC clusters is
  0.270.02 (solar units)
• The Fe excess is defined as
• The iron mass excess within r is

12

• From BeppoSAX measures we obtain
• MFeexc 10-20 of the total ICM iron mass _at_
  ?2500.
• Is this mass due to metals ejected from the BCG?
• We have collected optical magnitudes from the
  literature for the 12 BCGs (e.g. Schombert 1987)
  of our BeppoSAX sample and using the models of
  Bruzual Charlot we have estimated the M/L and
  then the stellar mass for each galaxy
• We have then used the model of chemical evolution
  of E galaxies from Pipino et al. (2002, NewA, 7,
  227) to convert these stellar masses into Fe
  masses ejected from the galaxies obtaining
• ?The BCG is able to produce the MFeexc during
  its life

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The following theories have been proposed to
explain the origin of BCGs

• Galaxy merging in the early history of the
  formation of the cluster as expected in
  hierarchical cosmological models.
• Post-cluster formation models
• Gas accretion and star formation from cooling
  flows,
• Galactic cannibalism or accretion of existing
  galaxy population through dynamical friction
  and/or tidal stripping

The main difference is that primordial origin
assumes that there is little SF activity after
cluster virialization, while galactic
cannibalism/CF are ongoing as the cluster
evolves.
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Iron Mass excess vs. kT
MexcFe,9 a L44 b a 0.05, b 2.23,
?LogMFeexc 0.26
A possibility to explain this relation is
that more massive clusters contain more massive
BCGs, which are producing larger quantities of
Iron during their life
KT (Mtot) ? BCG (SN,SF) ? MFeexc If so we expect
that MoptBCG ? KT and that MoptBCG ?
MFeexc
A number of authors (e.g. Edge Steward 1991,
Edge 1991, Takayama et al. 2002) found that the
optical luminosity of a BCG is positively
correlated with the LX and kT of its host
cluster.
15
Optical Luminosity vs. kT
A number of authors (e.g. Edge Steward 1991,
Edge 1991, Takayama et al. 2002) found that the
optical luminosity of a BCG is positively
correlated with the LX and kT of its host
cluster.
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Iron Mass excess vs. Optical Luminosity
MexcFe,9 10 abMopt a -13.1, b -0.930
Optical Magnitudes are from Postman Lauer
(1995) and Hoessel, Gunn Thuan (1980).
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Cluster (i.e. kT,Mtot)
Early CF (i.e. Lcool)
MFeexc
BCG (i.e. Mopt)

• Hp common origin of cluster and BCG

Hp common origin of early CF and BCG
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Iron Mass excess vs. Lcool
Lcool from Peres et al. (1998)
MexcFe,9 a Lcool,44 ß a 0.76, b 0.461/2
An alternative scenario consistent with our
data could be the following
Lcool (early CF) ? BCG (SF,SN) ? MFeexc If so we
expect that MoptBCG ? MFeexc and
that MoptBCG ? Lcool
.
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Optical Luminosity vs. Lcool
No significant correlation is present.
20
Cluster (i.e. kT,Mtot)
Early CF (i.e. Lcool)
MFeexc
BCG (i.e. Mopt)

• Hp common origin of cluster and BCG

Hp common origin of early CF and BCG
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Summary ICM MFe

• We have estimated the ICM Iron masses for a
  sample of 22 clusters by integrating de-projected
  gas and abundance profiles
• The relationship btw MFe and other fundamental
  quantities (i.e. T, Mtot,..) is through Mgas
• The MFe-Mgas relation is a very simple one the
  MFe/Mgas (i.e. the metal abundance) is the same
  for all clusters
• Since the Fe in the ICM has been formed in stars
  our result supports a scenario where the mass in
  stars in clusters is closely related to the gas
  mass
• We have used the MFeL relation to derive the
  local XMFeF from the local XLF

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Summary MFeexc

• For the first time we have estimated the Iron
  mass excess in CC clusters (1-5x109 Msun) using
  BeppoSAX data for 12 objects.
• MFeexc is 10-20 of the total ICM iron mass _at_
  ?2500.
• The BCG is able to produce the MFeexc observed in
  CC clusters during its life.
• Our data does not favor a scenario where MFeexc
  is due to gas accretion from the cooling flow.
• Our data favors a scenario where the properties
  of the BCG are related to those of the cluster.

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ICM Iron Mass to Light ratio

• IMLR MFe/LB (Ciotti et al 1991) ? fundamental
  for understanding cluster enrichment history
  (Renzini 1997)
• From global Z measurements (Renzini et al. 1993)
  
• IMLR 0.01-0.02 M?/L?
• From spatially resolved Ab measurements
• IMLR (_at_?1000) 0.006 M?/L?
• ? IMLR for CCs was overestimated by a factor 2-3
  because of the effect of Z gradients on the
  global emission-weighted measure of Z.
• IMLR is still constant with kT
• ? uniform
  SF history in clusters

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ICM Iron Mass vs. total Mass
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Predicted vs. observed Fe excess profiles
The abundance excess in the expected profiles is
completely due to the Brigthest Cluster Galaxy
(BCG)
The abundance is defined as ZFe(r)nFe(r)/nH(r)
Hypothesis nFe(r) ? l(r), where l(r) is the
LIGHT DISTRIBUTION
0.6 Mpc (z0.033)
1.4 Mpc (z0.077)
Probably we are just observing the accumulation
of metal ejection from the BCG into the ICM
1.1 Mpc (z0.057)
0.6 Mpc (z0.019)