Chris Richardson co-authors publication about hidden molecular gas in dwarf galaxies

By Christopher Richardson, faculty

October 20, 2023

The constellation of Ursa Major (The Great Bear) is home to Messier 101, the Pinwheel Galaxy. One of the biggest and brightest spiral galaxies in the night sky, Messier 101 is also the subject of one of Hubble's most famous images (heic0602). Like the Milky Way, Messier 101 is not alone, with smaller dwarf galaxies in its neighbourhood. NGC 5477, one of these dwarf galaxies in the Messier 101 group, is the subject of this image from the NASA/ESA Hubble Space Telescope. Without obvious structure, but with visible signs of ongoing starbirth, NGC 5477 looks much like an archetypal dwarf irregular galaxy. The bright nebulae that extend across much of the galaxy are clouds of glowing hydrogen gas in which new stars are forming. These glow pinkish red in real life, although the selection of green and infrared filters through which this image was taken makes them appear almost white. The observations were taken as part of a project to measure accurate distances to a range of galaxies within about 30 million light-years from Earth, by studying the brightness of red giant stars. In addition to NGC 5477, the image includes numerous galaxies in the background, including some that are visible right through NGC 5477. This serves as a reminder that galaxies, far from being solid, opaque objects, are actually largely made up of the empty space between their stars. This image is a combination of exposures taken through green and infrared filters using Hubble's Advanced Camera for Surveys. The field of view is approximately 3.3 by 3.3 arcminutes. 

Associate Professor Chris Richardson co-authors journal publication with colleagues that uses a novel approach to finding hidden molecular gas in dwarf galaxies

Nearby dwarf galaxies serve as suitable proxies for galaxies in the early universe that present many observational challenges. Molecular gas plays a crucial role in understanding how star formation progresses in dwarf galaxies, but the methods of detecting the most common molecules, H2 and CO, require a number of assumptions about the conditions present within the galaxy.

Lise Ramambason at the University of Heidelberg led a research group that included Associate Professor of Astrophysics Chris Richardson in using a novel method of accounting for “dark” molecular gas that doesn’t emit light that astronomers can observationally detect but shows up in numerical models of the dwarf galaxies.

This new technique predicts that a substantial amount of molecules sit in shielded clumps of invisible gas in dwarf galaxies, which helps understand a key ingredient for star formation in early universe. The article describing the results was recently accepted for publication in the top-tier Astrophysics & Astronomy journal, while a pre-print version of the paper is available here.

Posted in: Academics & Research

Tagged:

People in this article: