Chemical and Thermal History of the Intracluster Medium

Clusters of galaxies can be seen as giant astrophysical laboratories enclosing matter in a large enough volume, so that the matter composition can be taken as representing the composition of our Universe. X-ray observations allow a very precise investigation of the physical properties of the intracluster plasma allowing us to probe probe the cluster structure, determine its total mass, and measure the baryon fraction in clusters and in the Universe as a whole. We can determine the abundance of heavy elements from O to Ni which originate from supernova explosions and draw from this important conclusions on the history of star formation in the cluster galaxy population. From the entropy structure of the intracluster medium we obtain constraints on the energy release during early star bursts. With the observational capabilities of the X-ray observatories XMM-Newton and Chandra this field of research is rapidly evolving. In particular, first detailed observations of the intracluster medium of the Virgo cluster around M87 have provided new insights. The present contribution gives an account of the current implications of the intracluster medium observations, but more importantly illustrates the prospects of this research for the coming years.Comment: conference review article, 10 pages, 7 figures. to appear in "Recycling intergalactic and interstellar matter" IAU Symposium Series, Vol. 217, 2004, P.-A. Duc, J. Braine, E. Brinks (eds.

Galaxy Clusters: Cosmic High-Energy Laboratories to Study the Structure of Our Universe

This contribution illustrates the study of galaxy clusters as astrophysical laboratories as well as probes for the large-scale structure of the Universe. Using the REFLEX Cluster Survey, the measurement of the statistics of the large-scale structure on scales up to 500 $h^{-1}$ Mpc is illustrated. The results clearly favour a low density Universe. Clusters constitute, in addition, well defined astrophysical laboratory environments in which some very interesting large-scale phenomena can be studied. As an illustration we show some spectacular new XMM X-ray spectroscopic results on the thermal structure of cooling flows and the interaction effects of AGN with this hot intracluster medium. The X-ray observations with XMM-Newton show a lack of spectral evidence for large amounts of cooling and condensing gas in the centers of galaxy clusters believed to harbour strong cooling flows. To explain these findings we consider the heating of the core regions of clusters by jets from a central AGN. We find that the power output the AGN jets is well sufficient. The requirements such a heating model has to fulfill are explored and we find a very promising scenario of self-regulated Bondi accretion of the central black hole.Comment: 12 pages, 8 figures, Contribution to the MPA/ESO/MPE/USM conference "Lighthouses of the Universe", Sunyaev et al. (eds.), ESO Astrophysics Symposia, Springer Verla

Baptism, Confirmation and First Communion: Christian Initiation in the Contemporary Church

(Excerpt) Made, Not Born, is the title of a remarkable book produced by the remarkable program of liturgical studies conducted at the University of Notre Dame, and also the title of Frank Quinn\u27s keynote address yesterday. The correspondence of the two titles is surely no accident. The notion that Christians are made and not born may well come as a shock not only to Lutherans but to all those Christians that prize the Reformation emphasis on the priority of grace. We have for so long insisted on the gift character of baptism that such a title jars. A Christian is made? Never! is our first response, for faith is the gift of God, the necessary undergirding for the new life bestowed in baptism

Grace Upon Grace: living Water

(Excerpt) Two months ago, on February 22, a Lutheran pastor and his wife, both faithful and fruitful servants of our Lord, began their personal celebration of the feast of victory for our God. They now chant with the saints and all the heavenly host. Worthy is Christ the Lamb who was slain, whose blood set us free to be people of God. It would only be just if the choir director had chosen that hymn of praise to be sung by the choir that day, because the two I speak of were the Rev. Herbert and Ruth Undemann. Pastor Undemann left at least two great monuments to his passion for his Lord, this Institute of Liturgical Studies and the Lutheran Book of Worship. They also left us memories of a gracious, cultured way of life controlled by an abiding love of the Church and her worship

Cluster science from ROSAT to eROSITA

Galaxy clusters are one of the important cosmological probes to test the consistency of the observable structure and evolution of our Universe with the predictions of specific cosmological models. We use results from our analysis of the X-ray flux-limited REFLEX cluster sample from the ROSAT All-Sky Survey to illustrate the constraints on cosmological parameters that can be achieved with this approach. The upcoming eROSITA project of the Spektrum-Roentgen-Gamma mission will increase these capabilities by two orders of magnitude and importantly also increase the redshift range of such studies. We use the projected instrument performance to make predictions on the scope of the eROSITA survey and the potential of its exploitation.Comment: 5 pages, 8 figures, accepted for publication in Astronomische Nachrichten; the proceedings of the XMM-Newton Science Workshop: "Galaxy Clusters as Giant Cosmic Laboratories" at ESAC, Madrid, Spain, 21-23 May 201

Witnessing a merging bullet being stripped in the galaxy cluster, RXCJ2359.3-6042

We report the discovery of the merging cluster, RXCJ2359.3-6042, from the REFLEX II cluster survey and present our results from all three detectors combined in the imaging and spectral analysis of the XMM-Newton data. Also known as Abell 4067, this is a unique system, where a compact bullet penetrates an extended, low density cluster at redshift z=0.099 clearly seen from our follow-up XMM-Newton observation. The bullet goes right through the central region of the cluster without being disrupted and we can clearly watch the process how the bullet component is stripped of its layers outside the core. There is an indication of a shock heated region in the East of the cluster with a higher temperature. The bulk temperature of the cluster is about 3.12 keV implying a lower mass system. Spearheading the bullet is a cool core centred by a massive early type galaxy. The temperatures and metallicities of a few regions in the cluster derived from the spectral analysis supports our conjecture based on the surface brightness image that a much colder compact component at 1.55 keV with large metallicity (0.75 Zsol) penetrates the main cluster, where the core of the infalling component survived the merger leaving stripped gas behind at the centre of the main cluster. We also give an estimate of the total mass within r500, which is about 2e14Msol from the deprojected spherical-beta modelling of the cluster in good agreement with other mass estimates from the M--Tx and M-sigma_v relations.Comment: 5 pages, 4 figures, A&A in press. Images with better resolution will be available through the journa

Disturbed galaxy clusters are more abundant in an X-ray volume-limited sample

We present first strong observational evidence that the X-ray cool-core bias or the apparent bias in the abundance of relaxed clusters is absent in our REFLEX volume-limited sample (ReVols). We show that these previously observed biases are due to the survey selection method such as for an flux-limited survey, and are not due to the inherent nature of X-ray selection. We also find that the X-ray luminosity distributions of clusters for the relaxed and for the disturbed clusters are distinct and a displacement of approximately 60 per cent is required to match two distributions. Our results suggest that to achieve more precise scaling relation one may need to take the morphology of clusters and their fractional abundance into account.Comment: A&A, 606, L4, 4 pages, 3 figure