The earliest galaxies did not have dust - only gas - but astronomers have discovered a dusty galaxy from the beginning of the universe. The findings show how quickly dust enriched galaxies. Galaxies with dust and gases like carbon and oxygen, have what it takes to form planets.
Astronomers have glimpsed at the first detection of dust in one of the most distant galaxies ever observed, according to press releases from the Niels Bohr Institute at the University of Copenhagen, the European Southern Observatory (ESO) and the Science and Technology Facilities Council (STFC) in the U.K.
By using ALMA (Atacama Large Millimeter/submillimeter Array) and the Very Large Telescope's (VLT) X-shooter, the team, lead by by Darach Watson, from the University of Copenhagen, found evidence for the evolution of galaxies after the Big Bang. ALMA was used to find the far-off galaxy of A1689-zD1 and ESO's VLT measured the distance.
Astronomers were surprised that A1689-zD1 was much more evolved that expected, according to the press releases. The galaxy had "a fraction of dust similar to a very mature galaxy, such as the Milky Way. Such dust is vital to life, because it helps form planets, complex molecules and normal stars," according to the press release from ESO.
A1689-zD1 was seen due to its brightness caused by a gravitational lens - a galaxy cluster, Abell 1689 - located between the galaxy and Earth.
"After confirming the galaxy's distance using the VLT we realized it had previously been observed with ALMA. We didn't expect to find much, but I can tell you we were all quite excited when we realized that not only had ALMA observed it, but that there was a clear detection," said Watson, an astrophysicist with the Dark Cosmology Centre at the Niels Bohr Institute, according to the press release from ESO. "One of the main goals of the ALMA observatory was to find galaxies in the early universe from their cold gas and dust emissions -- and here we had it!"
"Although the exact origin of galactic dust remains obscure," Watson continued, , "our findings indicate that its production occurs very rapidly, within only 500 million years of the beginning of star formation in the universe -- a very short cosmological time frame, given that most stars live for billions of years."
The University of Edinburgh's Michal Michalowski led the effort to model and calculate the brightness, wavelengths, amount of dust and stars and rapidness of resupply. "A1689-zD1 has turned out to be a hundred times less massive than the Milky Way, but forming new stars significantly faster," Michalowski said, according to the press release from STFC. "Most of this star formation activity is completely hidden from us by galactic dust, and we have not seen this before at such large distances. ALMA is the only telescope in the world sensitive enough to detect such remote galaxies."
What we are seeing from A1689-zD1 is from when the galaxy was only 700 million years old - during the period of reionization - 5 percent of its current age. "It is the first time dust has been discovered in one of the most distant galaxies ever observed -- only 700 million years after the Big Bang," said Watson, according to the press release by the University of Copenhagen. "It is a galaxy of modest size and yet it is already full of dust. This is very surprising and it tells us that ordinary galaxies were enriched with heavier elements far faster than expected."
At the young age of 700 million years old, astronomers would expect the galaxy not to have heavier chemical elements, like carbon, oxygen and nitrogen, but A1689-zD1 showed a great amount of radiation being emitted in the far infrared, according to the press release by ESO. A1689-zD1 showed a dust-to-gas ratio similar to galaxies that are much older.
"We looked for the most distant galaxies in the universe. Based on the colors of the light observed with the Hubble Space Telescope we can see which galaxies could be very distant," said Lise Christensen, an astrophysicist at the Dark Cosmology Centre, according to the press release from the Niels Bohr Institute. "Using observations from the very sensitive instrument, the X-shooter spectrograph on the Very Large Telescope, VLT, in Chile, we measured the galaxy's spectrum and from that calculated its redshift, i.e., the change in the light's wavelength as the object recedes from us. From the redshift we can calculate the galaxy's distance from us and it turned out to be, as we suspected, one of the most distant galaxies we know of to date."
"It is this far-infrared light, which tells us that there is dust in the galaxy," Watson said, according to the press release. "It is very surprising and it is the first time that dust has been found in such an early galaxy. The process of star formation must therefore have started very early in the history of the universe and be associated with the formation of dust. The detection of large amounts of solid material shows that the galaxy was enriched very early with solids which are a prerequisite for the formation of complex molecules and planets."
Co-author Kirsten Knudsen from the Chalmers University of Technology in Sweden added: "This amazingly dusty galaxy seems to have been in a rush to make its first generations of stars. In the future, ALMA will be able to help us to find more galaxies like this, and learn just what makes them so keen to grow up."
The team is composed of D. Watson (Niels Bohr Institute, University of Copenhagen, Denmark), L. Christensen (University of Copenhagen), K. K. Knudsen (Chalmers University of Technology, Sweden), J. Richard (CRAL, Observatoire de Lyon, Saint Genis Laval, France), A. Gallazzi (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy) and M. J. Michalowski (SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, UK).
The study, "A dusty, normal galaxy in the epoch of reionization," by D. Watson et al., was published in the journal Nature.
