Do High-Velocity Clouds trace the Dark Matter subhalo population?

Abstract

Within the cosmological concordance model, Cold Dark Matter (CDM) subhalos form the building blocks which merge hierarchically to more massive galaxies. Since intergalactic gas is accreted by massive galaxies, observable e.g. as high- velocity clouds (HVCs) around the Milky Way, with extremely low metallicities, these can be suggested to represent the baryonic content of primordial Dark Matter (DM) subhalos. Another possibility of their origin is that they stem from disrupted satellite galaxies, but in this case, these gas clouds move unaccompanied by a bound DM structure. Since HVCs are observed with long gas tails and with irregular substructures, numerical models are performed aiming at exploring their structure and compare them with observations. If HVCs are engulfed by DM subhalos, their gas must leave the DM gravitational potential and reflect this in their dynamics. On the other hand, the evolution and survival of pure gas models must be tested to distinguish between DM-dominated and DM-free clouds and to allow conclusions on their origin. The models demonstrate that purely baryonic HVCs with low masses are disrupted by ram-pressure stripping and Kelvin-Helmholtz instabilities, while more massive ones survive, losing their initially spherical shape and develop significant substructures including cometary elongations in the column density distribution ("head-tail structure"). On the contrary, HVCs with DM subhalos survive with more than 90% of their gas mass still bound and spherically shaped, approaching the Galactic disk like bullets. In addition, we find that velocity gradients along the cometary head-tail structures does not necessarily offer a possibility to distinguish between DM-dominated and purely gaseous HVCs. Comparison of models with observations let us conclude that HVCs are not embedded in a DM substructure and do not trace the cosmological subhalo population.

Accepted for publication in A&A

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Cited by in corpus (11)

• The Magellanic System: the puzzle of the leading gas stream
• The Smith Cloud and its dark matter halo: Survival of a Galactic disc passage
• The Magellanic Stream and Debris Clouds
• Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud
• New detections of embedded clusters in the Galactic halo
• Chemo-dynamical simulations of dwarf galaxy evolution
• A High-Velocity Cloud Impact Forming a Supershell in the Milky Way
• Exploring Hydrodynamic Instabilities along the Infalling High-Velocity Cloud Complex A
• The Long Tails of the Pegasus-Pisces Arch Intermediate Velocity Cloud
• Search for dark matter in compact hydrogen clouds
• The Observed O VI is Just the Tip of the Iceberg: Estimating the Hidden Material in Circumgalactic and Intergalactic Clouds