Galaxy formation in the reionization epoch as hinted by WideField Camera 3 observations of the Hubble Ultra Deep Field

作     者：Hao-Jing Yan Rogier A. Windhorst Nimish E Hathi Seth H. Cohen Russell E.Ryan Robert W. O＇Connell Patrick J. McCarthy 

作者机构：Center for Cosmology and AstroParticle Physics The Ohio State University 191 West Woodruff Avenue Columbus OH 43210 USA School of Earth and Space Exploration Arizona State University Tempe AZ 85287 USA Department of Physics ＆ Astronomy University of California Riverside CA 92521 USA Department of Physics University of California One Shields Avenue Davis CA 95616 USA Astronomy Department University of Virginia P.O. Box 3818 Charlottesville VA 22903 USA Observatories of the Carnegie Institution of Washington 813 Santa Barbara Street Pasadena CA 91101 USA 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2010年第10卷第9期

页      面：867-904页

核心收录：

学科分类：0709[理学-地质学] 080901[工学-物理电子学] 07[理学] 0809[工学-电子科学与技术（可授工学、理学学位）] 08[工学] 0708[理学-地球物理学] 070401[理学-天体物理] 0704[理学-天文学] 0825[工学-航空宇航科学与技术] 

基　　金：supported in part by the NASA JWST Interdisciplinary Scientist grant NAG5-12460 from GSFC 

主　　题：cosmology observations -- cosmology early universe -- galaxies evolution -- galaxies luminosity function, mass function -- infrared galaxies 

摘      要：We present a large sample of candidate galaxies at z ≈ 7 - 10, selected in the Hubble Ultra Deep Field using the new observations of the Wide Field Camera 3 that was recently installed on the Hubble Space Telescope. Our sample is composed of 20 z850-dropouts （four new discoveries）, 15 Y105-dropouts （nine new discoveries） and 20 J125-dropouts （all new discoveries）. The surface densities of the Z850-dropouts are close to what was predicted by earlier studies, however, those of the Y105- and J125-dropouts are quite unexpected. While no Y105- or J125-dropouts have been found at AB ≤ 28.0 mag, their surface densities seem to increase sharply at fainter levels. While some of these candidates seem to be close to foreground galaxies and thus could possibly be gravitationally lensed, the overall surface densities after excluding such cases are still much higher than what would be expected if the luminosity function does not evolve from z ～ 7 to 10. Motivated by such steep increases, we tentatively propose a set of Schechter function parameters to describe the luminosity functions at z ≈8 and 10. As compared to their counterpart at z ≈ 7, here L^＊ decreases by a factor of ～ 6.5 and Ф^＊ increases by a factor of 17-90. Although such parameters are not yet demanded by the existing observations, they are allowed and seem to agree with the data better than other alternatives. If these luminosity functions are still valid beyond our current detection limit, this would imply a sudden emergence of a large number of low-luminosity galaxies when looking back in time to z ≈ 10, which, while seemingly exotic, would naturally fit in the picture of the cosmic hydrogen reionization. These early galaxies could easily account for the ionizing photon budget required by the reionization, and they would imply that the global star formation rate density might start from a very high value at z ≈ 10, rapidly reach the minimum at z≈ 7, and start to rise again towards z ≈ 6. In this scenario, the maj