Making better measurements of the composition of galaxies

A research utilizing knowledge from telescopes on Earth and within the sky resolves an issue plaguing astronomers working within the infrared, and will assist make higher observations of the composition of the universe with the James Webb Area Telescope and different devices. The work is revealed April 20 in Nature Astronomy.

“We’re attempting to measure the composition of gases inside galaxies,” mentioned Yuguang Chen, a postdoctoral researcher working with Professor Tucker Jones within the Division of Physics and Astronomy on the College of California, Davis.

Most components aside from hydrogen, helium and lithium are produced inside stars, so the composition and distribution of heavier components—particularly the ratio of oxygen to hydrogen—might help astronomers perceive what number of and what sorts of stars are being fashioned in a distant object.

Astronomers use two strategies to measure oxygen in a galaxy, however sadly, they provide totally different outcomes. One widespread technique, collisionally excited traces, provides a powerful sign, however the outcomes are considered delicate to temperature modifications, Chen mentioned. A second technique makes use of a special set of traces, known as recombination traces, that are fainter however not considered affected by temperature.

The recombination line technique constantly produces measurements about double these from collisionally excited traces. Scientists attribute the discrepancy to temperature fluctuations in gasoline clouds, however this has not been immediately confirmed, Chen mentioned.

Chen, Jones and colleagues used optical and infrared astronomy to measure oxygen abundance in dwarf galaxy Markarian 71, about 11 million gentle years from Earth. They used archived knowledge from the just lately retired SOFIA flying telescope and the retired Herschel Area Observatory, in addition to making observations with telescopes on the W.M. Keck Observatory in Mauna Kea, Hawaii.

SOFIA (Stratospheric Observatory For Infrared Astronomy) was a telescope mounted in a Boeing 747 plane. By flying at 38,000 to 45,000 ft, the plane may get above 99% of the water vapor in Earth’s ambiance, which successfully blocks infrared light from deep space from reaching floor stage. A joint mission of NASA and the German space company, SOFIA made its final operational flight in September 2022 and is now headed for a museum show in Tucson.

The Herschel Area Observatory, named after astronomers William and Caroline Herschel, was an infrared space telescope operated by the European Area Company. It was energetic from 2009 to 2013.

A stunning consequence

With knowledge from these devices, Chen and Jones examined oxygen abundance in Markarian 71 whereas correcting for temperature fluctuations. They discovered that the consequence from collisionally excited infrared traces was nonetheless 50% lower than that from the recombination line technique, even after eliminating the impact of temperature.

“This consequence could be very stunning to us,” Chen mentioned. There isn’t any consensus on a proof for the discrepancy, he mentioned. The crew plans to take a look at extra objects to determine what properties of galaxies correlate with this variation, Chen mentioned.

One of many objectives of the James Webb Area Telescope, launched in 2022, is to make infrared observations of the composition of distant galaxies within the first billion years of the universe. The brand new outcomes present a framework for making these measurements with the JWST and the Atacama Massive Millimeter Array in Chile.

Further co-authors on the paper are: Ryan Sanders and Erin Huntzinger, UC Davis; Dario Fadder, Jessica Sutter and Robert Minchin, SOFIA Science Heart, NASA Ames Analysis Heart; Peter Senchyna, Observatories of the Carnegie Institute for Science, Pasadena; Daniel Stark and Benjamin Weiner, Steward Observatory, College of Arizona; Justin Spilker, Texas A&M College; and Guido Roberts-Borsani, UCLA.