Astronomers using the NASA/ESA Hubble Space Telescope have captured a detailed image of an extremely distant, gravitationally lensed galaxy they believe contains two dozen patches of newborn stars.
This artist’s illustration portrays what the gravitationally lensed galaxy SGAS 1110 might look like up close. A sea of young, blue stars is streaked with dark dust lanes and studded with bright pink patches that mark sites of star formation. SGAS 1110 is one of more than 70 studied as part of the Sloan Giant Arcs Survey, an imaging survey that searched 240 galaxy clusters to find new examples of gravitational lensing. Image credit: NASA / ESA / Z. Levay, STScI.
The galaxy in question, SGAS J111020.0+645950.8 (SGAS 1110 for short), is a clumpy, star-forming galaxy approximately 11 billion light-years away.
The Hubble observations of SGAS 1110 were enabled by a cosmic effect known as gravitational lensing.
The gravity of the massive galaxy cluster SDSS J1110+6459, located between SGAS 1110 and Earth, distorts the galaxy’s light, stretching it into an arc and also magnifying it almost 30 times.
“When we saw the reconstructed image we said, ‘Wow, it looks like fireworks are going off everywhere’,” said team member Dr. Jane Rigby, an astronomer at NASA’s Goddard Space Flight Center.
Dr. Rigby and colleagues had to develop special computer code to remove the distortions caused by the gravitational lens, and reveal the disk galaxy as it would normally appear.
In this Hubble photograph of the massive galaxy cluster SDSS J1110+6459, which is located about 6 billion light-years from Earth, a spotty blue arc stands out against a background of red galaxies. That arc is actually three separate images of the same background galaxy SGAS 1110. The galaxy has been gravitationally lensed, its light magnified and distorted by the intervening galaxy cluster. On the right: how SGAS 1110 would look to Hubble without distortions. Image credit: NASA / ESA / T. Johnson, University of Michigan.
Surprisingly, the reconstructed image revealed two dozen clumps of newborn stars, each spanning about 200 to 300 light-years.
This contradicted theories suggesting that star-forming regions in the distant, early Universe were much larger, 3,000 light-years or more in size.
“The cosmic explosions forming new stars across SGAS 1110 are happening on surprisingly small scales,” said team member Dr. Kate Whitaker, assistant professor of physics at the University of Connecticut.
“Previously it was thought that these distant, early galaxies formed new stars in giant supersized star clusters, but we lacked the angular resolution to know this for sure.”
“These observations challenge that commonly held idea.”
“There are star-forming knots as far down in size as we can see,” said team member Traci Johnson, a doctoral student at the University of Michigan.
“Without the magnification boost of the gravitational lens, the disk galaxy would appear perfectly smooth and unremarkable to Hubble.”
“This would give astronomers a very different picture of where stars are forming.”
The team’s findings were published this week in a paper in the Astrophysical Journal Letters and two additional papers in the Astrophysical Journal.
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J.R. Rigby et al. 2017. Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459, II: What is missed at the normal resolution of the Hubble Space Telescope? ApJ 843, 79; doi: 10.3847/1538-4357/aa775e
Traci L. Johnson et al. 2017. Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation down to 30 parsec scales. ApJL 843, L21; doi: 10.3847/2041-8213/aa7516
Traci L. Johnson et al. 2017. Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459, I: Lens Modeling and Source Reconstruction. ApJ 843, 78; doi: 10.3847/1538-4357/aa7756
