English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Dust is known to be produced in the envelopes of AGB stars, the expandedshells of supernova (SN) remnants, and in situ grain growth in the ISM,although the corresponding efficiency of each of these dust formationmechanisms at different redshifts remains a topic of debate. During the firstGyr after the Big Bang, it is widely believed that there was not enough time toform AGB stars in high numbers, so that the dust at this epoch is expected tobe purely from SNe, or subsequent grain growth in the ISM. The time periodcorresponding to z ~5-6 is thus expected to display the transition from SN-onlydust to a mixture of both formation channels as we know it today. Here we aimto use afterglow observations of GRBs at redshifts larger than $z > 4$ in orderto derive host galaxy dust column densities along their line-of-sight and totest if a SN-type dust extinction curve is required for some of the bursts. GRBafterglow observations were performed with the 7-channel GROND Detector at the2.2m MPI telescope in La Silla, Chile and combined with data gathered with XRT.We increase the number of measured $A_V$ values for GRBs at z > 4 by a factorof ~2-3 and find that, in contrast to samples at mostly lower redshift, all ofthe GRB afterglows have a visual extinction of $A_V$ < 0.5 mag. Analysis of theGROND detection thresholds and results from a Monte-Carlo simulation show that,although we partly suffer from an observational bias against highlyextinguished sight-lines, GRB host galaxies at 4 < z < 6 seem to contain onaverage less dust than at z ~ 2. Additionally, we find that all of the GRBs canbe modeled with locally measured extinction curves and that the SN-like dustextinction curve provides a better fit for only two of the afterglow SEDs. Forthe first time we also report a photometric redshift of $z = 7.88$ for GRB100905A, making it one of the most distant GRBs known to date.

Dust reddening and extinction curves towards gamma-ray bursts at z > 4