The halo of the young galaxy offers clues about its growth and evolution

Maunakea, Hawaii – A team of astronomers discovered a new way to unravel the mysteries of the formation and evolution of early galaxies

In a study published today in Astrophysical Journal Letters Lead author Dawn Erb of the University of Wisconsin-Milwaukee and his team used for the first time new capabilities at the WM Keck Observatory of Maunakea, Hawaii to review Q2343- BX418, a small galaxy located about 10 billion light years from Earth. .

This distant galaxy is an analog for younger galaxies that are too weak to be studied in detail, making it an ideal candidate to learn about what galaxies looked like shortly after the birth of the galaxy. ;universe.

BX418 also attracts the attention of astronomers because its gaseous halo gives off a particular type of light.

"In recent years, we have learned that the gaseous halos surrounding galaxies shine with a particular ultraviolet wavelength called Lyman's Alpha Emissions. There are many different theories about what produces this Lyman alpha emission in the halos of galaxies, but at least a part is probably due to the light that is originally produced by the formation of stars in the galaxy. "The team Erb, who includes Charles Steidel and Yuguang Chen of Caltech, used one of the latest observatory instruments, the Keck Cosmic Web Imager (KCWI), to perform a detailed spectral analysis. gaseous halo of BX418; its properties could provide clues to the stars that form inside the galaxy.

"Most of the ordinary matter in the universe is not in the form of star or planet, but of gas., But around and between them," Erb said.

The halo is where gas enters and exits the system. The gas surrounding the galaxies can supply them; gas from a galaxy can also escape in the halo. "The influx of new gases accumulating in a galaxy fuels the formation of new stars, while gas flows limit the ability of a galaxy to form stars by eliminating gases," explains Erb. .

"Therefore, understanding the complex interactions that occur in this gaseous halo is essential to discover how galaxies form stars and evolve."

This study is part of a large ongoing investigation led by Steidel for many years. Previously, Steidel's team studied BX418 using other instruments at the Keck Observatory.

This latest study using KCWI adds detail and clarity to the galaxy and its gaseous halo that was not possible before; The instrument is specifically designed to study the vaporous streams of weak gas that connect galaxies, known as the cosmic web.

"Our study was really facilitated by the design and sensitivity of this new instrument: it's not just an ordinary spectrograph, it's a full-field spectrograph, which means that 39 "is a kind of combined camera." The power of KCWI, combined with the location of Keck telescopes on Maunakea where observational conditions are among the most untouched on Earth, provides some of the most glimpsing insights more detailed of the cosmos.

The Erb team used KCWI to take spectra of the BX418 halo Lyman's alpha emission. This allowed them to trace the gas, plot its velocity and spatial extent, and then create a three-dimensional map showing the structure of the gas and its behavior.

The team's data suggest that the galaxy is surrounded by a spherical gas flow and that there are significant variations in the range of density and velocity of this gas.

Erb says this analysis is the first of its kind. Because it's only been tested on one galaxy, other galaxies need to be studied to see if these results are typical.

Now that the team has discovered a new way of knowing the properties of the gaseous halo, we hope that a more in-depth analysis of the data collected and computer simulations modeling the processes will help to better understand the characteristics of the gaseous halo. first galaxies. in our universe.

"As we work to complete the more detailed modeling, we will be able to test how the properties of the Lyman alpha emission in the gaseous halo are related to the properties of the galaxies themselves, which will then tell us some something about how the star formation in the galaxy influences the gas in the halo, "said Erb.