Abstract
Popular cosmological scenarios predict that galaxies form hierarchically from
the merger of many progenitors, each with their own unique star formation
history (SFH). We use the approach recently developed by Pacifici et al. (2012)
to constrain the SFHs of 4517 blue (presumably star-forming) galaxies with
spectroscopic redshifts in the range 0.2<z<1.4 from the All-Wavelength Extended
Groth Strip International Survey (AEGIS). This consists in the Bayesian
analysis of the observed galaxy spectral energy distributions with a
comprehensive library of synthetic spectra assembled using state-of-the-art
models of star formation and chemical enrichment histories, stellar population
synthesis, nebular emission, and attenuation by dust. We constrain the SFH of
each galaxy in our sample by comparing the observed fluxes in the B, R, I and
Ks bands and rest-frame optical emission-line luminosities with those of one
million model spectral energy distributions. We explore the dependence of the
resulting SFHs on galaxy stellar mass and redshift. We find that the average
SFHs of high-mass galaxies rise and fall in a roughly symmetric bell-shaped
manner, while those of low-mass galaxies rise progressively in time, consistent
with the typically stronger activity of star formation in low-mass compared to
high-mass galaxies. For galaxies of all masses, the star formation activity
rises more rapidly at high than at low redshift. These findings imply that the
standard approximation of exponentially declining SFHs widely used to interpret
observed galaxy spectral energy distributions is not appropriate to constrain
the physical parameters of star-forming galaxies at intermediate redshifts.
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