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<\/a>In Summer of 2022, SALT achieved a milestone by observing its first celestial object in the infrared. The target was a familiar one, the Eagle Nebula \u2014 made famous by the Hubble Telescope\u2019s imagery that revealed its unfathomable size and active stellar nursery. The nebula is located in the constellation Serpens and made for an ideal first target because of its intriguing structure and many star-forming regions.<\/p>\n\n\n\n
\u201cPeople came out of the woodwork for this momentous occasion. They had logged many long-hour days helping us prepare for this moment and weren\u2019t going to miss the event, even though it meant staying even longer into the night,\u201d says Marsha Wolf, senior scientist at the University of Wisconsin\u2013Madison Department of Astronomy and principal investigator for the SALT Near-Infrared Washburn Astronomical Laboratories Spectrograph. \u201cThere were lots of high-fives going around the room.\u201d<\/p>\n\n\n
<\/a>The SALT telescope is led by the South African Astronomical Observatory in partnership with more than 10 universities and observatories, including the UW\u2013Madison Department of Astronomy and the Space Science and Engineering Center who helped design and build the NIRWALS.<\/p>\n\n\n\n
The SALT uses an array of 91 hexagonal mirrors to collect cosmic light and focus it toward three detectors: the SALT Imaging and Acquisition Camera or SALTICAM, the Robert Stobie Spectrograph, and the NIRWALS. Each is sensitive to different wavelengths of light, including the visible and the near-infrared spectrum. Astronomers use both types of light to observe and study all aspects of celestial objects like stars, galaxies and nebulae.<\/p>\n\n\n\n
Wolf\u2019s research focuses on galaxy formation and evolution. By using both the infrared and visible light gathered by the telescope, she and her team are able to witness changes in the structure of galaxies over time. In particular, they study galaxies that have active supermassive black holes at their center, known as active galactic nuclei. When these black holes feed on nearby matter like gas and stars, much of the matter is ejected far away from the center at blistering speeds. The resulting shockwaves can be forceful enough to disrupt the formation of nearby stars within the galaxy. These violent interactions emit light in the visible and infrared frequencies that are captured by the SALT telescope detectors.<\/p>\n\n\n
<\/a>Credit: Lisa Crause<\/figcaption><\/figure>\n<\/div>\n\n\n
\u201cStars form through the gravitational collapse of gas, so one way to stop this process is to heat the gas enough so that thermal motions of its particles overpower gravity and prevent it from condensing into stars,\u201d says Wolf. \u201cOne proposed feedback culprit is the supermassive black hole at the center of nearly every galaxy.\u201d<\/p>\n\n\n\n
The idea is that the hot gasses and matter that are not consumed by the black hole collide with other particles in the galaxy, causing those areas to heat up. This redistribution of energy could interrupt a nearby star\u2019s formation and better match observations with computer simulated galaxy formations.<\/p>\n\n\n\n
Wolf and her team will use the SALT to investigate hundreds of nearby galaxies to search for evidence of black hole disruptions and outflows of energy away from the center. According to Wolf, a large sample size is needed because each galaxy observed by the SALT provides only an instantaneous snapshot of a process that takes place over millions of years. Image by image, the team will be able to witness different phases of a galaxy\u2019s evolution and the activity from its black hole.<\/p>\n\n\n\n
\u201cThe near-infrared spectra from our new instrument will give information on shocks in the gas from active galactic nuclei outflows, past supernovae, and the very youngest stellar populations,\u201d says Wolf. \u201cPutting these data all together, this will paint a clearer picture of if and how the nuclei have regulated the star formation histories of galaxies.\u201d<\/p>\n\n\n\n