NASA JPL Caltech Spitzer | sig10-023 | 18 Nov 2010
The Buried Starburst in the Interacting Galaxy II Zw 096 as Revealed by the Spitzer Space Telescope - H Inami et alA Powerful Shrouded Starburst
These images show how a brilliant burst of star formation (red glow, right image) is revealed in infrared observations from NASA's Spitzer Space Telescope. The collision of two spiral galaxies, has triggered this luminous starburst, the brightest ever seen taking place far away from the centers, or nuclei, of merging galaxies.
The merging galaxies, known collectively as II Zw 096, can be clearly seen in the image from NASA's Hubble Space Telescope (left). This image combines light spanning the far-ultraviolet through the near-infrared. The real action in this galactic train wreck is barely hinted at in the red speckles near the middle of it all.
The booming blast of star formation only jumps out when Spitzer's mid-infrared view, represented in red, is folded into the mix (right). This tiny region may be as small as 700 light-years across - just a tiny portion of the full 50,000 light-year extent of II Zw 096 - yet it blasts out 80 percent of the infrared light from this galactic tumult. The surrounding shroud of dust renders the stars here nearly invisible in other wavelengths of light.
Researchers were surprised to see such a brilliant infrared glow in an area so far offset from the center of the spiral galaxy. Starbursts are often found crammed into the very centers of merging galaxies, but this is the brightest starburst ever seen outside a galaxy's nucleus. Based on Spitzer data, researchers estimate the starburst is cranking out stars at the breakneck pace of around 100 solar masses, or masses of our Sun, per year.
The Hubble image (left) represents ultraviolet light at a wavelength of 0.15 microns as blue, visible light at 0.44 microns as cyan, and near infrared light at 0.9 microns as red.
In the combined image (right) Hubble's far-ultraviolet and visible light at wavelengths of 0.15 and 0.44 microns is shown as blue, and the near infrared light at 0.9 microns is cyan. Spitzer's infrared light at 4.5 microns is represented by orange, and the mid-infrared light at 8.0 and 24 microns is red.
Credit: NASA/JPL-Caltech/STScI/H. Inami (SSC/Caltech)
Astronomers using NASA's Spitzer Space Telescope have found a stunning burst of star formation that beams out as much infrared light as an entire galaxy. The collision of two spiral galaxies has triggered this explosion, which is cloaked by dust that renders its stars nearly invisible in other wavelengths of light.
The starburst newly revealed by Spitzer stands as the most luminous ever seen taking place away from the centers, or nuclei, of merging parent galaxies. It blazes ten times brighter than the nearby Universe's previous most famous "off-nuclear starburst" that gleams in another galactic smashup known as the Antennae Galaxy.
The new findings show that galaxy mergers can pack a real star-making wallop far from the respective galactic centers, where star-forming dust and gases typically pool.
"This discovery proves that merging galaxies can generate powerful starbursts outside of the centers of the parent galaxies," says Hanae Inami, first author of a paper detailing the results in the July issue of The Astronomical Journal. Inami is a graduate student at The Graduate University for Advanced Studies in Japan and the Spitzer Science Center at the California Institute of Technology. She adds: "The infrared light emission of the starburst dominates its host galaxy and rivals that of the most luminous galaxies we see that are relatively close to our home, the Milky Way."
"No matter how you slice it, this starburst is one of the most luminous objects in the local Universe," agrees Lee Armus, second author of the paper and a senior research astronomer also at the Spitzer Science Center.
- Astronomical Journal 140(1) 63 (July 2010) DOI: 10.1088/0004-6256/140/1/63
arXiv.org > astro-ph > arXiv:1004.3543 > 20 Apr 2010