Oldest Oxygen Shows Earliest Stars Formed 250 Million Years After Big Bang

Postado Mai 16, 2018

The galaxy's stars are believed to have formed 250 million years after the birth of the universe, earlier than any others known. This discovery also represents the most distant oxygen ever detected in the Universe and the most distant galaxy ever observed by ALMA or the VLT. They found that the observed brightness of the galaxy is well-explained by a model where the onset of star formation corresponds to only 250 million years after the Universe began [2].

"This extremely distant, extremely young galaxy has a remarkable chemical maturity to it", said Wei Zheng, an astronomer at Johns Hopkins University in Baltimore, who led the discovery of this galaxy with the Hubble Space Telescope and estimated its distance. Oxygen forms in stars, which then release it into the surrounding space when they die.

"The mature stellar population in MACS1149-JD1 implies that stars were forming back to even earlier times, beyond what we can now see with our telescopes".

New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) reveal the faint, telltale signature of oxygen coming from a galaxy at a record-setting distance of 13.28 billion light-years from Earth, meaning we are observing this object it as it appeared when the universe was only 500 million years old, or less than 4 percent its current age.

After that, objects in the Universe become progressively easier to see, and it's one of these that was the focus of an worldwide team of astronomers, led by Takuya Hashimoto, an astronomer at Osaka Sangyo University and the National Astronomical Observatory of Japan.

Researchers were able to detect the ionized oxygen from a signal whose infrared light was stretched into microwave wavelengths by the expansion of the universe. These observations independently verify that MACS1149-JD1 is the most distant galaxy with a precise distance measurement. This also broke their own record for finding the most distant source of oxygen. ALMA has been used previously to break the record for the most distant known galaxy, it did so twice in 2016 finding galaxies 13.1 billion light-years away, and 13.2 billion light-years away.

"I was thrilled to see the signal of the distant oxygen in the ALMA data". The distance to the galaxy determined from this observation is consistent with the distance from the oxygen observation.

The team then reconstructed the star formation history in the galaxy using infrared data taken with the NASA/ESA Hubble Space Telescope and NASA Spitzer Space Telescope.

Titled "The onset of star formation 250 million years after the Big Bang", the paper, involving a large global team of researchers, was published online Wednesday in the journal Nature. Which leads back to the question of when did the very first galaxies emerge from an epoch known as the "cosmic dawn" - a period of total darkness that followed after the Big Bang.

"With MACS1149-JD1, we have managed to probe history beyond the limits of when we can actually detect galaxies with current facilities".

Professor Ellis said: "Determining when cosmic dawn occurred is akin to the "Holy Grail" of cosmology and galaxy formation". There is renewed optimism we are getting closer and closer to witnessing directly the birth of starlight.

For MACS1149-JD1 to contain substantial amounts of oxygen, many stars must have already gone through that whole life cycle. A calculation based on the latest cosmological parameters measured with Planck (H0=67.3 km/s/Mpc, Ωm=0.315, Λ=0.685: Planck 2013 Results) yields the distance of 13.28 billion light-years.

The Atacama Large Millimeter/submillimeter Array (ALMA) is not your standard, run-of-the-mill telescope.