JWST observations reveal the stellar structure of the star-forming galaxy GN20

An international team of astronomers has used the James Webb Space Telescope (JWST) to observe a bright, dusty star-forming galaxy known as GN20. The results of the monitoring campaign, published April 26 in arXiv Preprint server, providing important insights into the stellar structure of this galaxy.

At a redshift of 4.05, GN20 is one of the most dusty-forming stars around. galaxies (DSFGs) known to date. GN20 is located in a primary cluster or hyperdensity galaxy, has an infrared luminosity of about 18.6 solar luminosities, and a star formation rate (SFR) of about 1860. solar masses every year. The molecular gas distribution in this galaxy appears lumpy star structure It has a diameter of about 45,600 light years and kinematics consistent with that of the massive turntable.

Recently, a group of astronomers led by Luis Colina of the Spanish Center for Astrobiology in Madrid, Spain, decided to carry out mid-infrared observations of GN20, with the aim of shedding more light on its properties. For this purpose, they used the JWST medium infrared instrument (MIRI).

“Images of the GN20 JWST were acquired from November 23-24, 2022, using a MIRI imager (MIRIM, Bouchet et al, 2015) in an F560W filter as part of the European MIRI Consortium Guaranteed Time (Program ID 1264),” the researchers explain.

Observations found that GN20 has a stellar structure characterized by an unresolved (magnitude -22.35) luminous core and an extended, diffuse atmosphere. This stellar structure forms new stars at a steady, high rate of about 500 solar masses per year, for 100 million years.

The core is less than 2,600 light-years across, carries 9% of the total flux and coincides with an emission of cold compressed nuclear dust. The stellar envelope has an effective radius of about 11,740 light-years, and its position corresponds to that of Carbon Monoxide molecular gas, but its centroid is roughly 3,300 light-years away from the stellar core. This displacement could be the result of a gravitational encounter or a recent merger.

By analyzing the JWST images, the team also identified additional faint stellar masses that appear to be associated with some of the ultraviolet and carbon monoxide masses. Moreover, astronomers have found that the stellar core appears to have the highest concentration cold dust But not the largest concentration of molecular gas.

Summarizing the results, the paper’s authors note that GN20 has all the properties needed to evolve into a quiet massive galaxy at mean redshift.

“It is a large, luminous galaxy at z = 4.05 that is involved in a short, massive starburst centered in the stellar nucleus and extending over the entire galaxy, to a radius of 4 kbps, likely caused by interaction or merger with a member of the primordial cluster” , the researchers explained.

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