Himiko (astronomy)

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Himiko (after a legendary Japanese ruler ) is an astronomical object at a distance of 12.9 billion light years that was discovered in 2007 by Masami Ouchi using the Subaru telescope in Hawaii and identified as a Lyman alpha emitter by April 2009 .

What we see of Himiko today took place around 800 million years after the Big Bang , i.e. during the reionization epoch . Himiko is unusually large for an object of this era, so it plays an important role in studying the formation of the first galaxies in the early universe .

discovery

The object was discovered in 2007 by a group of Japanese scientists in the XMM Newton Deep Survey Field (SXDS). In the SXDS, 207 objects were found in the optical range that could be galaxies. Himiko was so bright that the scientists did not initially believe in a distant object.

The electromagnetic spectrum was then examined with the Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS) at the Keck Observatory in Hawaii and the Inamori Magellan Areal Camera and Spectrograph (IMACS) at the Las Campanas Observatory in Chile . A clear Lyman α line could be identified at a redshift of z  = 6.595, which corresponds to an observation epoch 800 million years after the Big Bang.

The star formation rate and the mass of the galaxy were determined with the Spitzer Space Telescope , the United Kingdom Infrared Telescope and other instruments .

description

Himiko is located in the constellation Whale . Recordings of the object show no detailed structure, which led to the characterization as blob ("blob"). The spectrum shows a clear Lyman α line, which originates from ionized hydrogen gas , and continuum emission from stars.

It is currently unclear by which mechanism the hydrogen gas was heated and ionized so that it now radiates in the Lyman α line. Based on the data, it is assumed that the gas is located in a galaxy 17  kpc (or 55,000 light years) in diameter, roughly half the size of our Milky Way . Himiko has a star formation rate of 34  solar masses / year and is believed to be 40 billion solar masses. It is unclear whether it is sufficient for the ionization of the hydrogen gas that the hydrogen gas is in the gravitational potential of the galaxy, or whether further mechanisms have to be used. Are discussed e.g. B. Heating by an active galaxy core (which would imply the presence of a supermassive black hole ) or the collision of two galaxies .

Planned further research

These possibilities should be confirmed or excluded by further observations. In particular, star formation in Himiko is to be investigated further with the Keck Observatory and the possibility of a black hole with the Chandra X-ray Observatory . The Hubble Space Telescope could also be used to consider the collision of two smaller galaxies as a possibility.

Individual evidence

  1. ↑ a b Masami Ouchi et al .: Discovery of a giant Lyα Emitter near the Reionization Epoch . In: The Astrophysical Journal . tape 696 , 2009, p. 1164–1175 , doi : 10.1088 / 0004-637X / 696/2/1164 , arxiv : 0807.4174v2 .
  2. ↑ a b Space.com: Experts Puzzled by Strange Space Blob. (No longer available online.) News.aol.ca, April 24, 2009, archived from the original on April 27, 2009 ; accessed on April 29, 2009 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / news.aol.ca
  3. ^ Subaru Telescope, National Astronomical Observatory of Japan: Press Release - Mysterious Space Blob Discovered at Cosmic Dawn. April 22, 2009, accessed April 29, 2009 .

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