Skip to ContentSkip to Navigation
About usNews and EventsNews articles

Diffuse neutral hydrogen in the local universe

29 January 2010

Promotie: dhr. A. Popping, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen
Proefschrift: Diffuse neutral hydrogen in the local universe
Promotor(s): prof.dr. J.M. van der Hulst
Faculteit: Wiskunde en Natuurwetenschappen
Contact: Attila Popping, tel. 00 33 495 04 4100, e-mail:,

Diffuse neutral hydrogen in the local universe

In the last years the realization has emerged, that galaxies do not dominate the mass budget of the Universe. Galaxies are the regions with the highest densities, in an underlying extended Cosmic Web. Imaging this structure is essential to better understand the evolution of galaxies and the Universe. Not only are galaxies formed here, this it is also the place where interaction happens between galaxies and the surrounding Intergalactic medium, which determines the life cycle of a galaxy. Numerical simulations predict that the Cosmic Web exists of extended and diffuse gas filaments, which are extremely hard to detect with current telescopes.

In this thesis we investigate diffuse gas regions in the Intergalactic medium, by using the 21-cm emission line of neutral hydrogen. In first instance we employ an advanced numerical simulation, from which the distribution of neutral hydrogen can be reconstructed. The statistical properties are compared with the statistics of earlier observations.

Observations from the Westerbork and Parkes radio telescopes are used to directly detect neutral hydrogen. The different data-sets cover the same region in the sky and are very sensitive to diffuse gas clumps. In the observations we find 16 new detections of neutral hydrogen at a very low brightness, that cannot be connected to a known galaxy. These new detections are potentially components of the Cosmic Web. With the observations we can increase our knowledge about the Intergalactic medium.

Last modified:15 September 2017 3.40 p.m.
printView this page in: Nederlands

More news

  • 11 July 2019

    Major companies’ annual reports too vague about climate impact

    Many major Dutch companies publish extensive information about climate impact in their annual reports. However, very few companies provide concrete, detailed information about their own CO2 emissions, the impact of climate change on their business...

  • 08 July 2019

    UG permanently closes Yantai project

    The University of Groningen (UG) has permanently closed the project aimed at creating a branch campus in Yantai. Discussions were held with China Agricultural University, the city of Yantai and the Province of Shandong.

  • 03 July 2019

    Cheap train tickets boost public transport use but reduce customer satisfaction

    Offers of cheap single train tickets through retailers such as Kruidvat or Etos have a positive impact on the number of kilometres travelled by rail. This impact is much bigger than that of more general TV, newspaper or magazine advertising. However,...