Dark Matter Aids In Finding Nursery Of The Universe

An international team of researchers that includes astrophysicists of Heidelberg University has discovered a galaxy straight from the nursery of the universe. MACS1149-JD1 was created less than 500 million years after the Big Bang, making it the most remote galaxy ever to be observed. The discovery was made possible by a natural phenomenon known as “gravitational lens” that enhances the brightness of astronomical objects. The findings will be published in “Nature” on 20 September 2012.

Galaxy Candidate MACS1149-JD Closeup
Credit: NASA, ESA, W. Zheng (JHU), M. Postman (STScI), and the CLASH Team 

Our universe came into being approx. 13.7 billion years ago with a Big Bang. 400 to 500 million years later, conditions in the cosmos allowed for the formation of the first stars. “There was almost no hope of ever receiving a signal from any object of this time period; if there already were galaxies back then, their brightness would be far weaker than the light of a candle on the moon. There’s no telescope on earth that would be able to discover such an object”, explains Prof. Dr. Matthias Bartelmann of Heidelberg University’s Centre for Astronomy (ZAH).

The natural luminosity enhancer that helped researchers discover the galaxy consists of dark matter, so called because it can only be perceived indirectly, e.g. by its light-attracting properties. Galaxy clusters in which hundreds or thousands of galaxies move in a relatively small space contain large amounts of dark matter. If such a galaxy cluster with its dark matter is located at a certain distance from Earth, it acts like a magnifying lens – it makes objects located behind it appear larger and brighter by bundling their light. It is this effect of the gravitational lens that led to the discovery of MACS1149-JD1.

Credit: NASA, ESA, W. Zheng (JHU), M. Postman (STScI), and the CLASH Team 

“Galaxies going through an intensive phase of star formation show a certain distinctive and characteristic gradation in their spectral energy distribution. We can detect this gradation by observing a galaxy through a telescope with different filters“, states Dr. Adi Zitrin, who is part of Prof. Bartelmann’s work group. However, the gradation shifts in just as characteristic a manner depending on how far away the galaxy is. In the case of MACS1149-JD1 this shift, known as redshift, has a value of 9.6. According to the Heidelberg scientists, this puts the galaxy at a distance which light has covered within 13.2 billion years.

Essential clues that led to the discovery of MACS1149-JD1 were provided by a method of analysis also developed at the ZAH. This method has scientists measuring the distortion of the telescope images of galaxies located far behind the galaxy clusters, a distortion that is caused by the large amount of invisible dark matter in the clusters. In the case of MACS1149+22, the researchers detected a total of seven background galaxies whose image was enhanced, distorted and split into 23 multiple images by the gravitational effect of the galaxy cluster. This enabled the team to predict the location of a light-enhanced galaxy at a redshift of 9.6. The scientists concluded that the galaxy must have formed as early as 490 million years after the Big Bang.

At the heart of this research are images provided by the Hubble space telescope that has been closely observing certain galaxy clusters since 2010. Headed by Prof. Dr. Wei Zheng from Johns Hopkins University in Baltimore, USA, the project counts research teams from Chile, China, Denmark, Germany, Italy, the Netherlands, Spain, Taiwan, the UK and the U.S. among its contributors. In Germany, this project is supported by the Baden-Württemberg Stiftung.
 

Source: Heidelberg University

Citation: W. Zheng, M. Postman, A. Zitrin, J. Moustakas, X. Shu, S. Jouvel, O. Host, A. Molino, L. Bradley, D. Coe, L. A. Moustakas, M. Carrasco, H. Ford, N. Benitez, T. R. Lauer, S. Seitz, R. Bouwens, A. Koekemoer, E. Medezinski, M. Bartelmann, T. Broadhurst, M. Donahue, C. Grillo, L. Infante, S. W. Jha, D. D. Kelson, O. Lahav, D. Lemze, P. Melchior, M. Meneghetti, J. Merten, M. Nonino, S. Ogaz, P. Rosati, K. Umetsu, A. van der Wel: A highly magnified candidate for a young galaxy seen when the Universe was about 500 Myr old, Nature (20 September 2012), doi10.1038/nature11446