Short gamma-ray bursts track further into the distant universe

Short gamma-ray bursts track further into the distant universe

Short gamma-ray bursts host galaxies throughout cosmic time. Credit: WM Keck Observatory/Adam Makarenko

A Northwestern University-led team of astronomers has developed the largest comprehensive inventory yet of galaxies from which short gamma-ray bursts (SGRBs) originate.

Using several highly sensitive instruments and sophisticated galaxy modeling, the researchers accurately determined the galaxy homes for 84 of the SGRBs and explored the properties of 69 of the identified galaxies. host galaxies. Among their findings, they discovered that about 85% of the studied SGRBs come from young, actively forming stars. galaxies.

The astronomers also found that more SGRBs occurred at earlier times, when the universe was much younger – and at distances greater than Host The centers of galaxies – than was known before. Surprisingly, many SGRBs have been seen far away from their host galaxies — as if they were “ejected,” a finding that raises questions about how they managed to travel so far.

“This is the biggest index “No SGRB host galaxies ever existed, so we expect it to be the gold standard for many years to come,” said Anya Nugent, a Northwestern University graduate student who led the study that focused on modeling host galaxies. field to advance our understanding of these remarkable events and what happens to stars after they die.”

The team will publish two papers, detailing the new catalog. Both papers will be published on Monday, November 21 in Astrophysical Journal. Because SGRBs are among the brightest explosions in the universe, the team named their catalog BRIGHT (Broadband Repository for the Investigation of Gamma-ray Burst Host Attributes). All data and modeling products for BRIGHT are publicly available online for community use.

Nugent is a graduate student in physics and astronomy at Northwestern University’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She was advised by Wen-fai Fong, assistant professor of physics and astronomy at Weinberg and a principal member of CIERA, who led a second study focused on observations of the SGRB host.

A benchmark for future comparisons

when two Neutron stars They collide, generating temporary flashes of intense gamma ray light, known as SGRBs. While gamma rays last only a few seconds, optical light can last for hours before fading below detection levels (an event called afterglow). SGRBs are some of the brightest explosions in the universe, with dozens of explosions detected and precisely identified each year. It is currently the only way to study and understand a large number of compact neutron star systems.

Since NASA’s Neil Gehrels Swift Observatory first detected the SGRB afterglow in 2005, astronomers have spent the past 17 years trying to understand which galaxies are producing these powerful bursts. Stars within the galaxy could give insight into the environmental conditions needed to produce SGRBs and could link mysterious explosions to the origins of neutron star mergers. To date, only one SGRB (GRB 170817A) has a confirmed neutron star merger origin – it was discovered only seconds later. Gravitational wave detectors Note the binary merger between neutron stars (GW170817).

Short gamma-ray bursts track further into the distant universe

Short gamma-ray bursts host galaxies throughout cosmic time. Credit: WM Keck Observatory/Adam Makarenko

“Within a decade, the next generation of gravitational-wave observatories will be able to detect neutron star mergers to the same distances that we do today in SGRBs,” Fung said. “Thus, our catalog will serve as a benchmark for future discoveries of neutron star mergers.”

“The index can trigger effects beyond just one class of transients such as SGRBs,” said Yuxin “Vic” Dong, study co-author and PhD in astrophysics. Student at Northwestern University. “With the abundance of data and results presented in the catalog, I believe a variety of research projects will benefit from it, perhaps even in ways we have not yet considered.”

An insight into neutron star systems

To create the catalog, the researchers used several highly sensitive instruments at the W.M. Keck Observatory, the Gemini Observatories, the MMT Observatory, the Large-Eyes Telescope Observatory, and the Magellan telescopes at Las Campanas Observatory to take deep images and spectral analyzes of some of the fainter galaxies. identified in a survey of SGRB hosts. The team also used data from two of NASA’s great observatories, the Hubble Space Telescope and the Spitzer Space Telescope.

Prior to these new studies, astronomers had distinguished host galaxies from only a few dozen SGRBs. The new catalog is four times as many samples as there are. Taking advantage of a much larger data set, the catalog shows that SGRB host galaxies can be young and star-forming. or age and near death. This means that neutron star systems form in a wide range of environments and many have fast timelines from formation to merger. Because neutron star mergers create heavy elements such as gold and platinum, the catalog data will also deepen scientists’ understanding of when precious metals were first created in the universe.

“We suspect that the younger SGRBs we find in young host galaxies come from binary star systems that formed in a star formation ‘explosion’ and are so tightly bound that they can merge very quickly,” Nugent said. “Old theories suggested that there must be ways for neutron stars to merge quickly, but so far, we haven’t been able to see them. We have found evidence of older SGRBs in much older galaxies and we think that the stars in those galaxies either took longer to form a binary system or It was a binary system that was further separated. Hence, it took longer for these galaxies to merge.”

JWST capabilities

With the ability to detect the faintest host galaxies since very early times in the universe, NASA’s new flagship infrared observatory, the James Webb Space Telescope (JWST), is poised to further advance understanding of neutron star mergers and how far back in time they are. seem.

“I am very excited about the possibility of using the James Webb Space Telescope to probe deeper into the homes of these rare explosive events,” Nugent said. “JWST’s ability to spot fainter galaxies in the universe could reveal more SGRB host galaxies that are currently evading detection, and perhaps even reveal a missing cluster and link to the early universe.”

“I started the observations for this project 10 years ago, and it was a great pleasure to be able to pass the torch on to the next generation of researchers,” said Fung. “It gives me great pleasure to see years of work brought to life in this catalog, thanks to the young researchers who have taken this study to the next level.”

more information:
Short I GRB host galaxies: optical and spectral catalogs, host associations, and central galaxy offsets, Astrophysical Journal (2022). …847/1538-4357/ac91d0

Short GRB II host galaxies: an ancient sample of redshift, properties of stellar clusters, and implications for the origins of neutron star mergers, Astrophysical Journal (2022). …847/1538-4357/ac91d1

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