# A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34

**Authors:** Dominik A. Riechers, C. M. Bradford, D. L. Clements, C. D. Dowell, I. Perez-Fournon, R. J. Ivison, C. Bridge, A. Conley, Hai Fu, J. D. Vieira, J. Wardlow, J. Calanog, A. Cooray, P. Hurley, R. Neri, J. Kamenetzky, J. E. Aguirre, B. Altieri, V. Arumugam, D. J. Benford  
**arXiv:** [1304.4256](https://arxiv.org/abs/1304.4256)  
**Date:** 2013-04-15  
**Summary page:** https://www.summarizepaper.com/en/paper/1304.4256v1/

## Key points

- Massive present-day early-type galaxies gained their stellar mass and heavy elements through intense starbursts in the most massive dark matter halos at early epochs
- The redshift distribution of dusty, massive starbursts is biased towards lower redshifts due to selection effects
- Researchers have identified a massive starburst galaxy at a redshift of 6.34 using a submillimeter color-selection technique
- The galaxy contains a highly excited and chemically evolved interstellar medium with a mass of at least a hundred billion solar masses, constituting at least 40% of the baryonic mass of the galaxy
- The star formation rate in this galaxy is more than 2,000 times that of our Milky Way, making it one of the highest observed rates at any epoch
- Environments capable of forming such massive and intense starbursts already existed as early as 880 million years after the Big Bang
- This finding provides important insights into the early universe's ability to produce and sustain extreme levels of star formation in galaxies

## Summary

Massive present-day early-type galaxies, such as elliptical and lenticular galaxies, are believed to have gained their stellar mass and heavy elements through intense starbursts in the most massive dark matter halos at early epochs. However, it is still unknown how soon after the Big Bang these massive starburst progenitors existed. The redshift distribution of dusty, massive starbursts has long been suspected to be biased towards lower redshifts due to selection effects. Recent findings have confirmed this suspicion by detecting systems out to a redshift of z~5. In this study, researchers report the identification of a massive starburst galaxy at an even higher redshift of 6.34 using a submillimeter color-selection technique. The redshift was determined with certainty through the analysis of molecular and atomic fine structure cooling lines. The measurements revealed that this galaxy contains a highly excited and chemically evolved interstellar medium with a mass of at least a hundred billion solar masses. This constitutes at least 40% of the baryonic mass of the galaxy. The star formation rate in this "maximum starburst" galaxy is more than 2,000 times that of our Milky Way, making it one of the highest observed rates at any epoch. Despite the overall decrease in cosmic star formation towards higher redshifts, this discovery suggests that environments capable of forming such massive and intense starbursts already existed as early as 880 million years after the Big Bang. This finding provides important insights into the early universe's ability to produce and sustain extreme levels of star formation in galaxies. It highlights the existence of mature environments capable of hosting these intense starbursts relatively soon after cosmic dawn. Further studies will continue to explore the formation mechanisms and evolutionary processes involved in these early massive starburst galaxies, shedding light on their role in shaping galactic evolution throughout cosmic history.