Star formation continues to be shrouded in mystery because the
process can be hidden behind curtains of dust and gas. However, Webb’s
infrared capabilities made it possible to peer through the murk using
several wavelengths of light that highlight different properties of the
galaxy.
While dark brown tendrils of heavy dust are threaded throughout M82’s
glowing white core even in an infrared view, Webb’s NIRCam revealed a
level of detail obscured in views from other telescopes. Closer to the
center, small specks depicted in green denote concentrated areas of
iron, most of which are remnants of supernovas. Small patches that
appear red signify regions where molecular hydrogen is illuminated by a
nearby young star’s radiation.
“This image shows the power of Webb,” said study co-author Rebecca
Levy M.S. ’17, Ph.D. ’21 of the University of Arizona, Tucson. “Every
single white dot in this image is either a star or a star cluster.
We can start to distinguish all of these tiny point sources, which
enables us to acquire an accurate count of all the star clusters in this
galaxy.”
Looking at M82 in slightly longer infrared wavelengths, clumpy
tendrils represented in red can be seen extending above and below the
galaxy’s plane. These gaseous streamers are a galactic wind rushing out
from the core of the starburst.
In part, Bolatto and his co-authors wanted to understand where this
galactic wind originates and how hot and cold components interact within
the wind. Webb’s NIRCam was able to trace the structure of the galactic
wind by following a trail of polycyclic aromatic hydrocarbons
(PAHs)—small dust grains that survive in cooler temperatures but are
destroyed in hot conditions.
To the team’s surprise, Webb’s view of the PAH emission highlights
the galactic wind’s fine structure—an aspect previously unknown.
Depicted as red filaments, the emission extends away from the central
region where the heart of star formation is located. Webb’s observations
of M82 in near-infrared light spur further questions about star
formation, some of which the team hopes to answer with additional Webb
data, including that of another starburst galaxy. The team is also
working on papers that will characterize the stellar clusters and
correlations among wind components of M82.
The team will soon have spectroscopic observations
of M82 from Webb ready for their analysis, as well as complementary
large-scale images of the galaxy and wind. Spectral data will help
astronomers determine accurate ages for the star clusters and provide a
sense of timing for how long each phase of star formation lasts in a
starburst galaxy environment.
UMD astronomy Professor Sylvain Veilleux, who also co-authored the
study, said that he and Bolatto will continue to use Webb data to study
the galactic winds of M82 and other objects.
“This is just the beginning since Alberto and I were recently awarded
additional time on Webb to observe 10 objects with known, large-scale
galactic winds, including M82,” Veilleux said. “We’ll be mapping both
the dust and the warm molecular gas, as well as the ionized gas
entrained in large-scale galactic winds, to learn how closely they lie
relative to each other.”
This article is based in part on a text by the Space Telescope Science Institute