Journal Article

GRB 090423 at a redshift of z ≈ 8.1

Salvaterra, R., Nousek, J., Fernández-Soto, A., Maiorano, E., Cusumano, G., Mannucci, F., Fugazza, D., Markwardt, C. B., Margutti, R., De Pasquale, M., Marinoni, S., Piranomonte, S., Antonelli, L. A., Racusin, J. L., Palazzi, E., Molinari, E., Guidorzi, C., Tagliaferri, G., Guetta, D., Masetti, N., Thöne, C. C., Ferrero, P., Mao, J., Barthelmy, S. D., Andreuzzi, G., Fiore, F., Amati, L., Covino, S., Palmer, D. M., Pagani, C., Valle, M. Della, Testa, V., Campana, S., D’Avanzo, P., Stella, L., Pian, E., Chincarini, G., Holland, S. T., Israel, G. L., Marshall, F. E., D’Elia, V., Giommi, P., Fenimore, E. E., Hunt, L. K., Hurley, K.

2009

Overview

Bursting at high redshift Two groups present redshift determinations and other spectroscopic data for the γ-ray burst GRB 090423 — now the earliest and most distant astronomical object known. Salvaterra et al . report its initial detection with the Swift satellite on 23 April 2009, and a redshift determination with the Telescopio Nazionale Galileo on La Palma 14 hours after the burst, obtaining z ≈ 8.1. Tanvir et al . used the United Kingdom Infrared Telescope, Hawaii, from about 20 minutes after the burst and arrive at z ≈ 8.2. The previous highest redshift known for any object was z = 6.96 for a Lyman-α emitting galaxy. These measurements imply that massive stars were being produced and were dying as γ-ray bursts as early as about 600 million years after the Big Bang, and that their properties are very similar to those stars producing γ-ray bursts 10 billion years later. Long-duration γ-ray bursts (GRBs), thought to result from the explosions of certain massive stars, are bright enough that some of them should be observable out to redshifts of z > 20. So far, the highest redshift measured for any object has been z = 6.96, for a Lyman-α emitting galaxy. Here, and in an accompanying paper, GRB 090423 is reported to lie at a redshift of z ≈ 8.2, implying that massive stars were being produced and dying as GRBs approximately 620 million years after the Big Bang. Gamma-ray bursts (GRBs) are produced by rare types of massive stellar explosion. Their rapidly fading afterglows are often bright enough at optical wavelengths that they are detectable at cosmological distances. Hitherto, the highest known redshift for a GRB was z = 6.7 (ref. 1 ), for GRB 080913, and for a galaxy was z = 6.96 (ref. 2 ). Here we report observations of GRB 090423 and the near-infrared spectroscopic measurement of its redshift, z = . This burst happened when the Universe was only about 4 per cent of its current age 3 . Its properties are similar to those of GRBs observed at low/intermediate redshifts, suggesting that the mechanisms and progenitors that gave rise to this burst about 600,000,000 years after the Big Bang are not markedly different from those producing GRBs about 10,000,000,000 years later.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: Astronomy / Astrophysics / Cosmic rays / Gamma rays / Humanities and Social Sciences / letter / Light / multidisciplinary / Observations / Properties / Science / Science (multidisciplinary) / Spectra / Stars & galaxies / Telescopes / Wavelengths