  It is commonly believed that the earliest stages of star-formation in the
Universe were self-regulated by global radiation backgrounds - either by the
ultraviolet Lyman-Werner (LW) photons emitted by the first stars (directly
photodissociating H_2), or by the X-rays produced by accretion onto the black
hole (BH) remnants of these stars (heating the gas but catalyzing H_2
formation). Recent studies have suggested that a significant fraction of the
first stars may have had low masses (a few M_sun). Such stars do not leave BH
remnants and they have softer spectra, with copious infrared (IR) radiation at
photon energies around 1eV. Similar to LW and X-ray photons, these photons have
a mean-free path comparable to the Hubble distance, building up an early IR
background. Here we show that if soft-spectrum stars, with masses of a few
M_sun, contributed more than 1% of the UV background (or their mass fraction
exceeded 90%), then their IR radiation dominated radiative feedback in the
early Universe. The feedback is different from the UV feedback from high-mass
stars, and occurs through the photo-detachment of H^- ions, necessary for
efficient H_2 formation. Nevertheless, we find that the baryon fraction which
must be incorporated into low-mass stars in order to suppress H_2-cooling is
only a factor of few higher than for high-mass stars.
