I found this in today's Nature Contents,
Al.
Letter
Nature 442, 786-789(17 August 2006) | doi:10.1038/nature05052; Received 25 April 2006; Accepted 6 July 2006
The rapid formation of a large rotating disk galaxy three billion years after the Big Bang
R. Genzel
1,
2, L. J. Tacconi
1, F. Eisenhauer
1, N. M. Förster Schreiber
1, A. Cimatti
1,
3, E. Daddi
4, N. Bouché
1, R. Davies
1, M. D. Lehnert
1, D. Lutz
1, N. Nesvadba
1, A. Verma
1, R. Abuter
1, K. Shapiro
5, A. Sternberg
6, A. Renzini
7, X. Kong
8, N. Arimoto
9 and M. Mignoli
10
Top of page Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe1,2,3. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks—the primary components of present-day galaxies—were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models4,5,6,7. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.
Editor's Summary
17 August 2006
An epoch-making galaxy
Large ground-based telescopes equipped with the latest near-infrared imaging spectroscopes and adaptive optics are capable of observing events that took place at a crucial period of galaxy formation, about 3 billion years after the Big Bang, when the Universe was only about 20% of its present age. Observations of a high-redshift (
z=2.38) star-forming galaxy from this epoch reveal its internal structure. A massive rotating protodisk is channelling gas towards an accreting black hole in a central stellar bulge. Previously the timescales and processes involved in the hierarchical build-up of galaxies were matters of conjecture; now they are the stuff of observation.
News and Views: Astronomy: Young spirals get older
These days, galaxies come in very different shapes and sizes. Cutting-edge technologies allow a detailed peek at how things looked in the Universe's early days — 'the same, but different' is the tentative message.
Robert C. Kennicutt, Jr
