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Robin Kooistra (Kapteyn Astronomical Institute, University of Groningen)

Detecting HI 21 cm emission from the IGM in large scale filaments with current and future radio telescopes
Wann Am 04.07.2017 von 11:00 bis 12:00
  • Special Seminar
  • Kolloquium
Wo SH, Seminarraum
Termin übernehmen vCal / iCal

The cosmic web plays an important role in providing the environment for the formation and evolution of galaxies. Studying the role of local gas overdensities in the number density and general properties of galaxies requires  observations of the large scale IGM structure. However, cosmic web filaments have only been observed indirectly  through the positions of galaxies in large galaxy surveys or through absorption features in the spectra of high-redshift sources.

We propose to directly detect intergalactic medium filaments through their emission in the HI 21 cm line. This signal depends on the density in the filaments and the strength of the UV/X-ray background. We use high-resolution cosmological simulations to estimate the intensity of this emission in low-redshift filaments and use it to make predictions for the direct detectability of specific filaments previously inferred from galaxy surveys, in particular SDSS.

Given the expected signal of these filaments, our study shows that HI emission from large filaments can be observed by current and next-generation radio telescopes. We estimate that gas in filaments of length l >15 Mpc/h with relatively small inclinations to the line of sight (<10 deg) can be observed in ∼ 40–100 h with telescopes such as GMRT or EVLA. The large field of view allows upcoming instruments such as Apertif and ASKAP to detect large filaments independently of their orientation and curvature, which opens up the possibility of stacking the emission from multiple filaments. Furthermore, our estimates indicate that a more powerful future radio telescope like SKA can be used to completely map most of these filaments, which will allow them to be used as a strong cosmological probe.