Аннотация
Over the last decade and a half, an avalanche of new data from
multiwavelength imaging and spectroscopic surveys has revolutionized our view
of galaxy formation and evolution. Making sense of it all and fitting it
together into a coherent picture remains one of astronomy's great challenges.
Here we review the range of complementary techniques and theoretical tools that
are allowing astronomers to map the cosmic history of star formation, heavy
element production, and reionization of the universe from the cosmic "dark
ages" to the present epoch. A consistent picture is emerging from modern galaxy
surveys, whereby the star formation rate density peaked about 3.5 Gyr after the
Big Bang, at redshift 1.9, and declined exponentially at later times, with an
e-folding timescale of 3.9 Gyr. Half of the stellar mass observed today was
formed before redshift 1.3. Less than 1% of today's stars formed during the
epoch of reionization, at redshift greater than 6. Under the simple assumption
of a universal initial mass function, the global stellar mass density inferred
at any epoch matches reasonably well the time integral of all the preceding
star formation activity, although a mild disagreement may still point to
unresolved issues with the measurements, or to deviations in the stellar
initial mass function from conventional assumptions. The assembly histories of
the stellar component of galaxies and their central black holes were quite
similar, offering evidence for the co-evolution of black holes and their host
galaxies. The rise of the mean metallicity of the universe to about 0.001 solar
by redshift six, one Gyr after the Big Bang, appears to have been accompanied
by the production of fewer than ten hydrogen Lyman-continuum photons per
baryon, a rather tight budget for cosmological deionization.
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