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Title: Science Case Reference: MUSE-MEM-SCI-052 Issue: 1.3 Date: 04/02/2004 Page: 23/100 Preparation). This extends the results from Moller & Fynbo (2001) to z=3. The peak in PDF at higher fluxes corresponds roughly to the values calculated in Figure 2-8, supporting the idea that large areas may ‘light up’ if these surface brightnesses can be detected. References Alcock, C., & Paczy’nski, B. 1979, Nature, 281, 358 Evrard, A. E., Summers, F. J., & Davis M. 1994, ApJ, 422, 11 Furlanetto, S., Schaye, J., Springel, V., & Hernquist, L. 2003, ApJ, in press, astroph/0311006 Gould, A., & Weinberg, D. H. 1996, ApJ, 468, 462 Haiman, Z. & Rees, M. J. 2001, ApJ, 556, 87 Kunth, D. et al. 2003, ApJ, in press, astro-ph/0307555 Moller, P., & Fynbo, J. U. 2001, A&A, 372, L57 Rauch, M. 1998, ARA&A, 36, 267 Steidel, C. C. et al. 1999, ApJ, 519, 1 Steidel, C. C. et al. 2000, ApJ, 532, 170 Weidinger, M., M˜oller, P., Fynbo, J. U., Thomsen, B., & Egholm, M.P. 2002, A&A, 391, 13 White, S. D. M., Frenk, C. S., Davis, M., & Efstathiou, G. 1987, ApJ, 313, 505 Zel'dovich, Ya. B. 1970, A&A, 5, 84 3
Title: Science Case Reference: MUSE-MEM-SCI-052 Issue: 1.3 Date: 04/02/2004 Page: 24/100 2.4. Reionization Because of the absence of any significant continuum absorption blueward of Ly α in the spectra of QSOs at redshifts as high as z≥5 (the so called Gunn-Peterson trough) hydrogen in the universe is highly ionized (i.e. to better than 1 part in 10000) for redshifts below 5. It is usually assumed that the hard spectra of QSOs and the softer spectra of hot stars are the prime ionizing sources at these redshifts. A similar analysis for Helium indicates that at redshifts below z≈3, Helium is also double ionized, whereas at higher redshift Helium ionization is at best only patchy. The transition in the opacity of HeII at redshift 3-4 coincides with an obvious jump in the temperature of the intergalactic medium (IGM) by a factor of ~2 (Theuns et al. 2002). This result is usually interpreted by the transition of a soft UV radiation field at z>4 that is incapable of ionizing HeII and that is dominated by stars, to a hard, HeII-ionizing UV radiation field with significant or even dominating contributions from QSOs at z6 in the SDSS followed by their spectroscopy is providing invaluable clues to the evolution of the universe at its earliest epochs. Even though QSOs at z=6.5 are far to rare to contribute significantly to the UV background, the mere presence of a luminous QSO at z=6.5, i.e. an epoch when the universe was less than 1 Gyr old, is indicative that massive structures (including supermassive black holes) must have formed at very early cosmological epochs. Within the concordance ΛCDM scenario such luminous QSOs would be hosted in halos with masses of 10 13 M sun . Even more excitingly, however, these QSO show clear indication of continuum absorption blue ward of Ly α corresponding to a neutral hydrogen fraction of ≥1% (by mass) and ≥ 0.1% (by volume), respectively. The standard interpretation is that we are witnessing the latest stages of the reionization epoch. According to numerical simulations of the propagation of ionizing photons in a ΛCDM universe (Gnedin 2000), the final stages of the reionization of the universe (the percolation phase) should happen almost instantaneously with a sharp transition from almost neutral to an almost fully ionized stage. Due to the strongly changing optical depth, a strong evolution of the abundance and the properties of so-called Ly α -emitters, the likely source of ionizing photons, is expected (see below). The red wavelength range of MUSE (probing Ly α at the redshift interval z=6-6.7) is well adapted for this crucial cosmological epoch. A second, very interesting result has been recently provided by the cosmic microwave background satellite, WMAP. Cross correlations between the temperature and polarization measurements of the CMB indicate that the total optical depth of free electrons is τ≈0.17, while a suddenly reionization at z=6.5 results in a significantly lower optical depth of τ≈0.04. However, the WMAP results are still preliminary as they are based on a cross correlation between the temperature and polarization measurements only. A detailed analysis of the polarization power spectrum is still awaiting publication. Nevertheless, should the WMAP polarization measurement be confirmed, it will highlight a very interesting inconsistency between IGM and CMB data. Unfortunately, the CMB polarization signal is only providing a
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Exposure Time Calculator and Perfor
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to achieve. To show the importance
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ANNEX - ETC mathcad sheet Roland Ba
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Science preparation and key personn
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If we interpret the broad width of
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8. Curriculum vitae We give here sh
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