2018MNRAS.479..377T -
Mon. Not. R. Astron. Soc., 479, 377-390 (2018/September-1)
Simulating the evolution of optically dark H I clouds in the Virgo cluster: will no one rid me of this turbulent sphere?
TAYLOR R., WUNSCH R. and PALOUS J.
Abstract (from CDS):
Most detected neutral atomic hydrogen (H I) at low redshift is associated with optically bright galaxies. However, a handful of H I clouds are known which appear to be optically dark and have no nearby potential progenitor galaxies, making tidal debris an unlikely explanation. In particular, 6 clouds identified by the Arecibo Galaxy Environment Survey are interesting due to the combination of their small size, isolation, and especially their broad line widths atypical of other such clouds. A recent suggestion is that these clouds exist in pressure equilibrium with the intracluster medium, with the line width arising from turbulent internal motions. Here, we explore that possibility by using the FLASH code to perform a series of 3D hydro simulations. Our clouds are modelled using spherical Gaussian density profiles, embedded in a hot, low-density gas representing the intracluster medium. The simulations account for heating and cooling of the gas, and we vary the structure and strength of their internal motions. We create synthetic H I spectra, and find that none of our simulations reproduce the observed cloud parameters for longer than ∼100 Myr: the clouds either collapse, disperse, or experience rapid heating which would cause ionization and render them undetectable to H I surveys. While the turbulent motions required to explain the high line widths generate structures which appear to be inherently unstable, making this an unlikely explanation for the observed clouds, these simulations demonstrate the importance of including the intracluster medium in any model seeking to explain the existence of these objects.
Abstract Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
galaxies: evolution - surveys: galaxies
Simbad objects:
3
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