Our Milky Way, and other galaxies like it, have 100 billion stars and are not isolated from other galaxies. Galaxies have clustered in tens or even thousands in the 13.8 billion years since the Big Bang, according to a press release from ESA.
"Because we are looking so far back in time, and because the the universe is assumed to be homogenous in all directions, we think it's very similar to looking at the equivalent of what a baby cluster might look like," said Brenda L. Frye, an assistant astronomer at the University of Arizona's Steward Observatory, according to a press release from the University of Arizona. "In contrast to previous observations, for which the odd one or two baby clusters was found which one would put in a zoo, we now have found a real sample of 200 baby clusters."
So, where did these clusters come from?
The goal was to create a map of the beginning of the universe, factoring in dark matter. Researchers found a few good candidates for "proto-clusters" - precursors of the large, mature galaxy clusters we see in the universe today.
"Hints of these kinds of objects had been found earlier in data from Herschel and other telescopes, but the all-sky capability of Planck revealed many more candidates for us to study," said Hervé Dole of the Institut d'Astrophysique Spatiale, Orsay, according to ESA's press release. Dole is the lead scientist of the analysis published in Astronomy & Astrophysics.
"We still have a lot to learn about this new population, requiring further follow-up studies with other observatories," Dole added. "But we believe that they are a missing piece of cosmological structure formation."
"We are now preparing an extended catalogue of possible proto-clusters detected by Planck, which should help us identify even more of these objects," added Ludovic Montier, a CNRS researcher at the Institut de Recherche en Astrophysique et Planétologie, Toulouse. Montier is the lead scientist of the Planck catalogue of high-redshift source candidates.
"This exciting result was possible thanks to the synergy between Herschel and Planck: rare objects could be identified from the Planck data covering the entire sky, and then Herschel was able to scrutinise them in finer detail," sad ESA's Herschel Project Scientist, Göran Pilbratt, according to ESA's press release. "Both space observatories completed their science observations in 2013, but their rich datasets will be exploited for plentiful new insights about the cosmos for years to come."
"High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE," is authored by the Planck Collaboration.
From ESA's press release:
"Planck detected the sky at nine frequencies, from 30 GHz to 857 GHz. The Planck frequencies used to detect the candidate proto-clusters in this study were 857 GHz, 545 GHz and 353 GHz. The follow-up observations made by Herschel's SPIRE instrument were at 250, 350 and 500 microns. The SPIRE 350 micron and 500 micron bands overlap with Planck's High Frequency Instrument (HFI) at 857 GHz and 545 GHz.
"The Planck Scientific Collaboration consists of all the scientists who have contributed to the development of the mission, and who participate in the scientific exploitation of the data during the proprietary period. These scientists are members of one or more of four consortia: the LFI Consortium, the HFI Consortium, the DK-Planck Consortium and ESA's Planck Science Office. The two European-led Planck Data Processing Centres are located in Paris, France and Trieste, Italy. The LFI consortium is led by N. Mandolesi, ASI, Italy (deputy PI: M. Bersanelli, Universita' degli Studi di Milano, Italy), and was responsible for the development and operation of LFI. The HFI consortium is led by J.L. Puget, Institut d'Astrophysique Spatiale in Orsay, France (deputy PI: F. Bouchet, Institut d'Astrophysique de Paris, France), and was responsible for the development and operation of HFI."
