Аннотация
This paper presents new deep and wide narrow-band surveys undertaken with
UKIRT, Subaru and the VLT; a unique combined effort to select large, robust
samples of H-alpha (Ha) emitters at z=0.40, 0.84, 1.47 and 2.23 (corresponding
to look-back times of 4.2, 7.0, 9.2 and 10.6 Gyrs) in a uniform manner over ~2
deg^2 in the COSMOS and UDS fields. The deep multi-epoch Ha surveys reach
~3M_sun/yr out to z=2.2 for the first time, while the wide area and the
coverage over two independent fields allow to greatly overcome cosmic variance.
A total of 1742, 637, 515 and 556 Ha emitters are homogeneously selected at
z=0.40, 0.84, 1.47 and 2.23, respectively, and used to determine the Ha
luminosity function and its evolution. The faint-end slope is found to be
-1.60+-0.08 over z=0-2.23, showing no evolution. The characteristic luminosity
of SF galaxies, L*, evolves significantly as logL*(z)=0.45z+logL*(z=0).
This is the first time Ha has been used to trace SF activity with a single
homogeneous survey at z=0.4-2.23. Overall, the evolution seen in Ha is in good
agreement with the evolution seen using inhomogeneous compilations of other
tracers of star formation, such as FIR and UV, jointly pointing towards the
bulk of the evolution in the last 11 Gyrs being driven by a strong luminosity
increase from z~0 to z~2.2. Our uniform analysis allows to derive the Ha star
formation history of the Universe, for which the simple parametrisation
log(SFRD)=-2.1/(1+z) is a good approximation for z<2.23. Both the shape and
normalisation of the Ha star formation history are consistent with the
measurements of the stellar mass density growth, confirming that our Ha
analysis traces the bulk of the formation of stars in the Universe up to z~2.2.
The star formation activity over the last ~11Gyrs is responsible for producing
~95% of the total stellar mass density observed locally today.
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