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See detailThe Search for Worlds Like Our Own
Fridlund, Malcolm; Eiroa, Carlos; Henning, Thomas et al

in Astrobiology (2010), 10(1), 5-17

The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets -- particularly, their evolution, their atmospheres, and their ability to host life ... [more ▼]

The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planets -- particularly, their evolution, their atmospheres, and their ability to host life -- constitute a significant problem. The quest for other worlds as abodes of life has been one of mankind's great questions for several millennia. For instance, as stated by Epicurus 300 BC: Other worlds, with plants and other living things, some of them similar and some of them different from ours, must exist. Demokritos from Abdera (460-370 BC), the man who invented the concept of indivisible small parts - atoms - also held the belief that other worlds exist around the stars and that some of these worlds may be inhabited by life-forms. The idea of the plurality of worlds and of life on them has since been held by scientists like Johannes Kepler and William Herschel, among many others. Here, one must also mention Giordano Bruno. Born in 1548, Bruno studied in France and came into contact with the teachings of Nicolas Copernicus. He wrote the book De l'Infinito, Universo e Mondi in 1584, in which he claimed that the Universe was infinite, that it contained an infinite amount of worlds like Earth, and that these worlds were inhabited by intelligent beings. At the time, this was extremely controversial, and eventually Bruno was arrested by the church and burned at the stake in Rome in 1600, as a heretic, for promoting this and other equally confrontational issues (though it is unclear exactly which idea was the one that ultimately brought him to his end). In all the aforementioned cases, the opinions and results were arrived at through reasoning--not by experiment. We have only recently acquired the technological capability to observe planets orbiting stars other than 6our Sun; acquisition of this capability has been a remarkable feat of our time. We show in this introduction to the Habitability Primer that mankind is at the dawning of an age when, by way of the scientific method and 21st-century technology, we will be able to answer this fascinating controversial issue that has persisted for at least 2500 years. [less ▲]

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See detailThe XMM-LSS survey. Survey design and first results
Pierre, Marguerite; Valtchanov, Ivan; Altieri, Bruno et al

in Journal of Cosmology and Astroparticle Physics [= JCAP] (2004), 09

The XMM Large Scale Structure survey (XMM-LSS) is a medium deep large area X-ray survey. Its goal is to extend large scale structure investigations attempted using ROSAT cluster samples to two redshift ... [more ▼]

The XMM Large Scale Structure survey (XMM-LSS) is a medium deep large area X-ray survey. Its goal is to extend large scale structure investigations attempted using ROSAT cluster samples to two redshift bins between 0<z<1 while maintaining the precision of earlier studies. Two main goals have constrained the survey design: the evolutionary study of the cluster cluster correlation function and of the cluster number density. The adopted observing configuration consists of an equatorial mosaic of 10 ks pointings, separated by 20^\prime and covering 8° à 8°, giving a pointsource sensitivity of {\sim } 5\times 10^{-15}~{\mathrm {erg~cm^{-2}~s^{-1}}} in the 0.5 2 keV band. This will yield more than 800 clusters of galaxies and a sample of X-ray AGN with a space density of about 300 deg[SUP]-2[/SUP]. We present the expected cosmological implications of the survey in the context of LgrCDM models and cluster evolution. We give an overview of the first observational results. The XMM-LSS survey is associated with several other major surveys, ranging from the UV to the radio wavebands, which will provide the necessary resources for X-ray source identification and further statistical studies. In particular, the associated CFHTLS weak lensing and AMiBA Sunyaev Zel'dovich surveys over the entire XMM-LSS area will provide for the first time a comprehensive study of the mass distribution and of cluster physics in the universe on scales of a few hundred Mpc. We describe the main characteristics of our wavelet-based X-ray pipeline and source identification procedures, including the classification of the cluster candidates by means of a photometric redshift analysis. This permits the selection of suitable targets for spectroscopic follow-up. We present preliminary results from the first 25 XMM-LSS pointings: X-ray source properties, optical counterparts, and highlights from the first Magellan and VLT/FORS2 spectroscopic runs as well as preliminary results from the NIR search for z>1 clusters. The results are promising and, so far, in accordance with our predictions. In particular: (1) we reproduce the logN logS distribution for point sources obtained from deeper surveys at our sensitivity; (2) we find a cluster number density of 15 20 deg[SUP]-2[/SUP] (3) for the first time, we statistically sample the group mass regime at a redshift out to {\sim } 0.5 . Paper based on observations obtained with the XMM,CFH, ESO (Prg: P70. A-0283 .A-0733), VLA, CTIO and Las Campanas observatories. [less ▲]

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