Rapid dust production in submillimeter galaxies at z>4 - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate

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Abstract: The existence of submillimeter-selected galaxies SMGs at redshifts z>4 hasrecently been confirmed. Using simultaneously all the available data from UV toradio we have modeled the spectral energy distributions of the six knownspectroscopically confirmed SMGs at z>4. We find that their star formationrates average ~2500 MSun yr^{-1}, stellar ~3.6x10^{11} MSun and dust~6.7x10^{8} MSun masses, extinction A V~2.2 mag, and gas-to-dust ratios~60 are within the ranges for 1.74 andlower-redshift SMGs. Those at z>4 tend to be among the most star-forming, leastmassive and hottest ~60 K SMGs and exhibit the highest fraction of stellarmass formed in the ongoing starburst ~45%. This indicates that at z>4 we seeearlier stages of evolution of submillimeter-bright galaxies. Using the derivedproperties for z>4 SMGs we investigate the origin of dust at epochs less than1.5 Gyr after the big bang. This is significant to our understanding of theevolution of the early universe. For three z>4 SMGs, asymptotic giant branchstars could be the dominant dust producers. However, for the remaining threeonly supernovae SNe are efficient and fast enough to be responsible for dustproduction, though requiring a very high dust yield per SN 0.15-0.65 MSun.The required dust yields are lower if a top-heavy initial mass function orsignificant dust growth in the interstellar medium is assumed. We estimatelower limits of the contribution of SMGs to the cosmic star formation andstellar mass densities at z~4-5 to be ~4% and ~1%, respectively.

Author: Michał J. Michałowski, Darach Watson, Jens Hjorth

Source: https://arxiv.org/


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