Issue |
A&A
Volume 504, Number 1, September II 2009
|
|
---|---|---|
Page(s) | 15 - 32 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361/200911811 | |
Published online | 09 July 2009 |
The simulated H I sky at low redshift
1
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: popping@astro.rug.nl
2
Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia
3
Astronomy Department, University of Arizona, Tucson, AZ 85721, USA
Received:
8
February
2009
Accepted:
15
June
2009
Context. Observations of intergalactic neutral hydrogen can provide a wealth
of information about structure and galaxy formation, potentially
tracing accretion and feedback processes on Mpc scales. Below
a column density of cm-2, the
“edge” or typical observational limit for H i emission from galaxies, simulations predict a cosmic web of
extended emission and filamentary structures. Current observations
of this regime are limited by telescope sensitivity, which will soon
advance substantially.
Aims. We study the distribution of neutral hydrogen and its 21-cm emission
properties in a cosmological hydrodynamic simulation, to gain more
insight into the distribution of H i below
cm-2. Such Lyman limit systems are
expected to trace out the cosmic web and are relatively
unexplored.
Methods. Beginning with a 32 h-1 Mpc simulation, we extract the neutral
hydrogen component by determining the neutral fraction, including a
post-processed correction for self-shielding based on the thermal
pressure. We take molecular hydrogen into account, assuming an
average density ratio at
. The
statistical properties of the H i emission are
compared with observations, to assess the reliability of the
simulation. We then make predictions for upcoming surveys.
Results. The simulated H i distribution
robustly describes the full column density range between
and
cm-2
and agrees very well with available measurements from
observations. Furthermore there is good correspondence in the
statistics when looking at the two-point correlation function and
the H i mass function. The reconstructed maps
are used to simulate observations of existing and future
telescopes by adding noise and accounting for the sensitivity
of the telescopes.
Conclusions. The general agreement in statistical properties of H i suggests that neutral hydrogen, as modelled in this hydrodynamic simulation, is a fair representation of neutral hydrogen in the Universe. Our method can be applied to other simulations, to compare different models of accretion and feedback. Future H i observations will be able to probe the regions where galaxies connect to the cosmic web.
Key words: intergalactic medium / cosmology: miscellaneous / galaxies: structure
© ESO, 2009
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