The Mudcat Café TM
Thread #70797 Message #1221058
Posted By: Amos
07-Jul-04 - 10:11 PM
Thread Name: BS: What Do Physicists Think About?? IV
Subject: RE: BS: What Do Physicists Think About?? IV
Meanwhile, another scale of anomaly altogether:
Nature 430, 184 - 187 (08 July 2004); doi:10.1038/nature02668
Old galaxies in the young Universe
A. CIMATTI1, E. DADDI2, A. RENZINI2, P. CASSATA3, E. VANZELLA3, L. POZZETTI4, S. CRISTIANI5, A. FONTANA6, G. RODIGHIERO3, M. MIGNOLI4 & G. ZAMORANI4
1 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Firenze, Italy 2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching, Germany 3 Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio, 2, I-35122 Padova, Italy 4 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna, Italy 5 INAF - Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy 6 INAF - Osservatorio Astronomico di Roma, via dell'Osservatorio 2, Monteporzio, Italy
Correspondence and requests for materials should be addressed to A.C. (cimatti@arcetri.astro.it).
More than half of all stars in the local Universe are found in massive spheroidal galaxies, which are characterized by old stellar populations with little or no current star formation. In present models, such galaxies appear rather late in the history of the Universe as the culmination of a hierarchical merging process, in which larger galaxies are assembled through mergers of smaller precursor galaxies. But observations have not yet established how, or even when, the massive spheroidals formed, nor if their seemingly sudden appearance when the Universe was about half its present age (at redshift z 1) results from a real evolutionary effect (such as a peak of mergers) or from the observational difficulty of identifying them at earlier epochs. Here we report the spectroscopic and morphological identification of four old, fully assembled, massive (1011 solar masses) spheroidal galaxies at l.6 < z < 1.9, the most distant such objects currently known. The existence of such systems when the Universe was only about one-quarter of its present age shows that the build-up of massive early-type galaxies was much faster in the early Universe than has been expected from theoretical simulations.