The entire Sculptor Galaxy has been captured in unprecedented detail in a single wide-angle view, displaying thousands of colors observed by the European Southern Observatory’s Very Large Telescope (ESO’s VLT).
While galaxies span vast distances, measured in the hundreds of thousands of light-years, smaller-scale forces drive their evolution. The clarity and detail of the new imagery allows astronomers to investigate the galaxy’s details while appreciating its totality.
Making Sense of Color
The many colors of distant galaxies are not only eye-pleasing, but also provide insights into their makeup. Varying colors correspond to specific kinds of gas, dust, and stars, allowing astronomers to identify their characteristics, including composition, age, and motion. With its precise recording of thousands of unique colors, the new Sculptor Galaxy map provides far greater insight than typical images of distant regions of space in which coloration is often limited.
“The Sculptor Galaxy is in a sweet spot,” says lead author ESO researcher Enrico Congiu. “It is close enough that we can resolve its internal structure and study its building blocks with incredible detail, but at the same time, big enough that we can still see it as a whole system.”
Capturing the Sculptor Galaxy
A single instrument, the VLT’s Multi Unit Spectroscopic Explorer (MUSE), captured more than 100 images in the over 50 hours of observations that went into the new map. The area observed sprawls for 65,000 light-years and lies 11 million light-years from Earth. The team created their final composite image by combining those separate observations.
Previously, only much smaller dwarf galaxies and the sparse Magellanic Clouds have been pieced together in such mosaics. The final image covered about 9 million spectra and had a whopping file size of 300 GB.
“We can zoom in to study individual regions where stars form at nearly the scale of individual stars, but we can also zoom out to study the galaxy as a whole,” said co-author Kathryn Kreckel of Heidelberg University.
Sculptor is one of the closest star-forming galaxies to our Milky Way. About a third of its stars are generated from a starburst ring consisting of 10 molecular clouds.
Reading the Galactic Map
Initial analysis of the Sculptor Galaxy imagery yielded unprecedented levels of detections, including 500 planetary nebulae, and estimated the galaxy’s distance as 17% farther from Earth than earlier work, although the team suggests that cosmic dust may be skewing that result. This far eclipses observations of other galaxies when it comes to the planetary nebulae regions of gas and dust that occur during the dying phase of stars similar to our Sun.
“Beyond our galactic neighbourhood, we usually deal with fewer than 100 detections per galaxy,” said co-author Fabian Scheuermann, a doctoral student at Heidelberg University
“Finding the planetary nebulae allows us to verify the distance to the galaxy — a critical piece of information on which the rest of the studies of the galaxy depend,” said co-author Adam Leroy, a professor at The Ohio State University.
Other researchers’ projects based on the Sculptor Galaxy map are already in the works. These include studies of gas flow, composition changes, and star formation in the galaxy.
“How such small processes can have such a big impact on a galaxy whose entire size is thousands of times bigger is still a mystery,” says Congiu, describing the necessity for understanding the interplay of various scales as is made possible in the new map.
The paper “The MUSE View of the Sculptor Galaxy: Survey Overview and the Planetary Nebulae Luminosity Function” will appear in Astronomy & Astrophysics.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.