By combining the power of NASA’s Hubble and Spitzer space telescopes, an international team of astronomers has discovered a candidate for the most distant galaxy known to date.
A study, accepted for publication in the Astrophysical Journal (arXiv.org version), reports the discovery of a galaxy located about 13.3 billion light-years away. The light from this galaxy, labeled MACS0647-JD, is from 420 million years after the Big Bang.
Due to the gravitational lensing by a massive galaxy cluster called MACS J0647+7015, the astronomers have observed three magnified images of MACS0647-JD. The cluster’s gravity boosted the light from the faraway galaxy, making the images appear brighter than they otherwise would, enabling the team to detect them more efficiently and with greater confidence.
“This cluster does what no manmade telescope can do,” said study co-author Dr Marc Postman of the Space Telescope Science Institute in Baltimore. “Without the magnification, it would require a Herculean effort to observe this galaxy.”
The object is so small it might have been in the first embryonic steps of forming an entire galaxy. An analysis shows that the galaxy is less than 600 light-years wide. Based on observations of somewhat closer galaxies, astronomers estimate that a typical galaxy of that epoch should be about 2,000 light-years wide. For comparison, the Large Magellanic Cloud, a companion dwarf galaxy to the Milky Way, is 14,000 light-years wide. Our Milky Way is 150,000 light-years across.
“This object may be one of many building blocks of a galaxy,” said lead author Dr Dan Coe of the Space Telescope Science Institute. “Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments.”
The estimated total mass of the stars in MACS0647-JD is roughly equal to 100 million to a billion Suns, or about 0.1 percent to 1 percent the mass of our Milky Way’s stars.
The study estimates that MACS0647-JD has a redshift of 11, the highest ever observed. The wavelengths of near-ultraviolet light from the galaxy have been stretched into the near-infrared part of the spectrum as the light traveled through an expanding Universe.
“The first galaxies probably formed somewhere between 100 million and 500 million years after the Big Bang,” the astronomers said. “Galaxies formed at such early times are more pristine than those formed later; they are relatively free of the heavy elements generated by later generation of supernovae.”
“Going forward, we hope to search for more embryonic galaxies at these early epochs,” concluded co-author Dr Daniel Kelson of the Carnegie Institute for Science’s Carnegie Observatories in Pasadena. “If these things are numerous, then they could have provided the energy to burn off the fog of hydrogen that pervaded the Universe, a process called reionization, ultimately making the Universe transparent to light.”
Bibliographic information: Dan Coe et al. 2012. CLASH: Three Strongly Lensed Images of a Candidate z ~ 11 Galaxy. Accepted for publication in the Astrophysical Journal; arXiv: 1211.3663