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On the Iron content in rich nearby Clusters

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). The BeppoSAX sample. NCC. 22 Galaxy Clusters : Nearby objects: z ~ 0.02- 0.1 r ~ 20% - 50% of r vir.

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On the Iron content in rich nearby Clusters

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  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 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 (~ 0.22±0.02). • 12 CC (cooling in core present): mean profile enhanced at center (~ 0.5), then similar to that of NCC (~ 0.27±0.02). CC De Grandi & Molendi 2001

  3. The ICM Iron mass The Fe Mass enclosed within a certain radius R is: Since rFe ZFe•ng, fromthe deprojected ng and ZFe profileswe compute: (Ettori, De Grandi, Molendi 2002, A&A, 391, 841)

  4. ICM Iron Mass vs. Lbol and kT @ ∆=2500 MFe,10 = a L44b a = 0.35 ± 0.07 b = 0.61 ± 0.07 бLogMFe= 0.12 MFe,10 = c kTd c = 0.04 ± 0.03 d = 1.99 ± 0.40 бLogMFe= 0.29 The MFe-L relation is tighter than the MFe-T relation.

  5. ICM Iron Mass vs. Lbol and kT @ ∆=2500 Lbol,44 = α kTβ α = 0.03 +0.06 -0.02 β = 3.21 ± 0.60 бLog 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.

  6. @ ∆=2500 • 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: бlogMFe, expected =0.28 бlogMFe,best-fit =0.29 We conclude that the most important relation is the one between MFe and Lbol

  7. 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 бLogMFe= 0.14 • The scatter is small  the MFe-Mgas relation is tight • MFe scales linearly with Mgas All clusters have the same metallicity (ZFe=MFe/Mgas) The mass in stars in clusters is closely related to Mgas

  8. The Iron Mass excess in CC clusters Mechanisms that could be responsible of the central Fe excess in CC CC NCC • Settling of heavy ions towards the center is unlikely as tdrift >> 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)

  9. From BeppoSAX measures we obtain: MFeexc ~ 10%-20% of the total ICM iron mass @ Δ=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

  10. 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.

  11. Iron Mass excess vs. kT MexcFe,9 = a L44b a = 0.05, b = 2.23, бLogMFeexc= 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  KTand thatMoptBCG  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.

  12. Iron Mass excess vs. Optical Luminosity MexcFe,9 = 10 a+bMopt a = -13.1, b = -0.930 Optical Magnitudes are from Postman & Lauer (1995) and Hoessel, Gunn & Thuan (1980).

  13. Cluster (i.e. kT,Mtot) Early CF (i.e. Lcool) Hp: common origin of cluster and BCG MFeexc BCG (i.e. Mopt) Hp: common origin of early CF and BCG

  14. Iron Mass excess vs. Lcool Lcool from Peres et al. (1998) MexcFe,9 = α Lcool,44β a = 0.76, b = 0.46~1/2 An alternative scenario consistent with our data could be the following: Lcool (early CF) BCG (SF,SN)  MFeexc If so we expect that MoptBCG MFeexcand thatMoptBCG  Lcool .

  15. Optical Luminosity vs. Lcool No significant correlation is present.

  16. Cluster (i.e. kT,Mtot) Early CF (i.e. Lcool) Hp: common origin of cluster and BCG MFeexc BCG (i.e. Mopt) Hp: common origin of early CF and BCG

  17. 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 MFe–L relation to derive the local XMFeF from the local XLF

  18. 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 @ Δ=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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