Thanks to the presence of a cosmic zoom lens, Hubble and Spitzer space telescopes got a uniquely close-up look at one of the farthest galaxies ever seen.
Salmon et al were able to detect a hint of light from SPT0615-JD because it was magnified as it passed around the massive galaxy cluster SPT-CL J0615-5746 as it traveled towards Earth. Image credit: NASA / ESA / B. Salmon, STScI.
The newly-discovered galaxy, named SPT0615-JD, is observed 500 million years after the Big Bang.
It has a mass of approximately 3 billion solar masses and is less than 2,500 light-years across, half the size of the nearby Small Magellanic Cloud.
SPT0615-JD is considered prototypical of young galaxies that emerged during the epoch shortly after the Big Bang.
Though a few other primitive galaxies have been seen at this early epoch, they have essentially all looked like red dots given their small size and tremendous distances.
However, in this case, the gravitational field of a massive foreground galaxy cluster, called SPT-CL J0615-5746, not only amplified the light from SPT0615-JD but also smeared its image into an arc (about 2 arcseconds long).
“No other candidate galaxy has been found at such a great distance that also gives you the spatial information that this arc image does,” Space Telescope Science Institute astronomer Dr. Brett Salmon, lead author of a paper accepted for publication in the Astrophysical Journal Letters (arXiv.org preprint).
“By analyzing the effects of gravitational lensing on the image of this galaxy, we can determine its actual size and shape.”
SPT0615-JD was identified in an extensive observing program called Reionization Lensing Cluster Survey (RELICS) and companion S-RELICS Spitzer program.
“RELICS was designed to discover distant galaxies like these that are magnified brightly enough for detailed study,” said Dr. Dan Coe, Principal Investigator of RELICS.
RELICS observed 41 massive galaxy clusters for the first time in the infrared with Hubble to search for such distant lensed galaxies.
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Brett Salmon et al. 2018. A Candidate z∼10 Galaxy Strongly Lensed into a Spatially Resolved Arc. ApJL, in press; arXiv: 1801.03103
