These four striking images exemplify a subset of galaxy clusters integral to the most extensive study aiming to unravel the mysteries behind star formation triggers in the universe’s largest galaxies. Recently detailed in latest press release, this research, conducted with NASA’s Chandra X-ray Observatory and other telescopes, underscores a fascinating revelation – the conditions fostering stellar conception within these immensely massive galaxies have remained unaltered over the past ten billion years.
Galaxy clusters, colossal entities united by gravity, harbor vast quantities of hot gas observable in X-rays. The weight of this hot gas surpasses several times the combined mass of all stars within the hundreds of galaxies typically found in these clusters. In the accompanying graphics featuring four galaxy cluster images, Chandra’s purple hues depict X-rays emitted by hot gas, while the yellow and cyan represent optical data from NASA’s Hubble Space Telescope, predominantly showcasing galaxies within the clusters. This comprehensive exploration unveils the enduring and consistent nature of star-forming conditions within these cosmic giants.
In this extensive study, researchers delved into the realm of the universe’s brightest and most massive galaxies, known as brightest cluster galaxies (BCGs), situated at the cores of 95 galaxy clusters. The selected clusters themselves represent an extreme subset, identified as the most massive clusters within a comprehensive survey employing the South Pole Telescope (SPT), with financial backing from the National Science Foundation and Department of Energy. Spanning distances between 3.4 and 9.9 billion light-years from Earth, these galaxy clusters offer a unique perspective on the universe’s evolution.
Highlighted are four specific galaxy clusters, each at varying distances from Earth—3.9 billion (SPT-CLJ0106-5943), 5.6 billion (SPT-CLJ0307-6225), 6.4 billion (SPT-CLJ0310-4647), and 7.7 billion (SPT-CLJ0615-5746) light-years away. The corresponding images portray dimensions ranging from 1.7 to 2.4 million light-years across, emphasizing the vast scale of these cosmic structures in comparison to our galaxy, which is approximately 100,000 light-years wide.
Within these images, gravitational lensing contributes to the presence of long, narrow features, where the mass within the clusters distorts light from galaxies situated behind them. Notably, the images have been rotated from the standard astronomer’s configuration, with variations in degree and direction for each cluster—clockwise or counterclockwise—to provide a clearer perspective on the intricate details of these celestial formations.
The research team uncovered a crucial determinant for triggering star formation in the galaxies under examination—the tipping point occurs when the level of disordered motion in the hot gas, referred to as “entropy,” drops below a critical threshold. Once this threshold is breached, the hot gas inevitably cools, paving the way for the birth of new stars.
The findings, reliant on X-ray data from the Chandra X-ray Observatory and radio data from the South Pole Telescope (SPT), were augmented by additional datasets. These include radio data from the Australia Telescope Compact Array and the Australian SKA Pathfinder Telescope, infrared data from NASA’s WISE satellite, and input from various optical telescopes—Magellan 6.5-m Telescopes, Gemini South Telescope, Blanco 4-m Telescope (DECam, MOSAIC-II), and Swope 1m Telescope. Notably, the study consumed almost 50 days of Chandra observing time to arrive at these significant results.
Michael Caldazilla from the Massachusetts Institute of Technology (MIT) unveiled these groundbreaking findings at the 243rd meeting of the American Astronomical Society in New Orleans, LA. Caldazilla is also the lead author of a paper submitted to The Astrophysical Journal, providing an in-depth exploration of this result (preprint available here).
Collaborating on this research are Michael McDonald (MIT), Bradford Benson (University of Chicago), Lindsay Bleem (Argonne National Laboratory), Judith Croston (The Open University, UK), Megan Donahue (Michigan State University), Alastair Edge (University of Durham, UK), Gordon Garmire (Penn State University), Julie Hvalacek-Larrondo (University of Colorado), Minh Huynh (CSIRO, Australia), Gourav Khullar (University of Pittsburgh), Ralph Kraft (Center for Astrophysics | Harvard & Smithsonian), Brian McNamara (University of Waterloo, Canada), Allison Noble (Arizona State University), Charles Romero (CfA), Florian Ruppin (University of Lyon, France), Taweewat Somboonpanyakul (Stanford University), and Mark Voit (Michigan State).
The Chandra program is managed by NASA’s Marshall Space Flight Center, with the Smithsonian Astrophysical Observatory’s Chandra X-ray Center overseeing science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Visual Portraits of four Galaxy Clusters Unveiled by Chandra X-ray Observatory.
This release showcases composite images of four galaxy clusters arranged in a two-by-two grid. Each image presents a mesmerizing display with a purple haze representing X-rays emitted by hot gas, skillfully captured by Chandra. Complementing this, optical data unveils distant galaxies surrounding the hot gas clouds, depicted in radiant golden yellows with subtle hints of vibrant cyan blue.
In the upper-left corner, the galaxy cluster labeled SPT-CLJ0310-4647 reveals a cosmic canvas where the vast darkness of space is adorned with gleaming specks of white, golden yellow, and bright blue light—each representing individual galaxies. Some galaxies appear as blurred, glowing dots, while others showcase the distinct curving arms of spiral formations. The center of the image features a faint purple cloud enveloping several of the cluster’s brightest galaxies, adding to the celestial spectacle.
Moving to the upper-right corner, we encounter an image of SPT-CLJ0615-5746. As the most distant cluster among the four, the galaxies within it appear relatively diminutive, concentrated mainly near the image’s center. The spherical purple cloud of hot gas exhibits a light purple spot at its core, contributing to the cosmic tapestry. Transitioning to the lower-right quadrant, SPT-CLJ0307-6225 unfolds with a vast, misty purple cloud representing X-rays from hot gas, dominating much of the image. The cloud’s brightest spot, a light purple dot near the lower-right corner, draws attention. Notably, a pixelated spiral galaxy stands out above and to the left of the center, adding a captivating element to the composition.
In the lower-left region is the galaxy cluster labeled SPT-CLJ0106-5943. This cluster showcases a scattering of cyan-blue galaxies, some of which appear stretched or elongated due to gravitational lensing effects. At the image’s center, a purple gas cloud with a bright white speck at its core captures the viewer’s gaze, creating a visually striking celestial tableau.
