Dwarf galaxy formation with and without dark matter-baryon streaming velocities

Abstract

We study how supersonic streaming velocities of baryons relative to dark matter -- a large-scale effect imprinted at recombination and coherent over $\sim 3$ Mpc scales -- affects the formation of dwarf galaxies at $z\gtrsim 5$. We perform cosmological hydrodynamic simulations, including and excluding streaming velocities, in regions centered on halos with $M_{\mathrm{vir}}(z=0)\approx 10^{10}$ M${}_{\odot }$; the simulations are part of the Feedback In Realistic Environments (FIRE) project and run with FIRE-3 physics. Our simulations comprise many thousands of systems with halo masses between $M_{\mathrm{vir}}=2\times 10^5$ M${}_{\odot }$ and $2\times 10^9$ M${}_{\odot }$ in the redshift range $z=20-5$. A few hundred of these galaxies form stars and have stellar masses ranging from 100 to $10^7$ M${}_{\odot }$. While star formation is globally delayed by approximately 50 Myr in the streaming relative to non-streaming simulations and the number of luminous galaxies is correspondingly suppressed at high redshift in the streaming runs, these effects decay with time. By $z=5$, the properties of the simulated galaxies are nearly identical in the streaming versus non-streaming runs, indicating that any effects of streaming velocities on the properties of galaxies at the mass scale of classical dwarfs and larger do not persist to $z=0$.

12 pages, 8 figures, submitted to ApJ

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Cited by in corpus (2)

• The Effects of Dark Matter Annihilation and Dark Matter-Baryon Velocity Offsets at Cosmic Dawn
• Primordial black holes and the velocity acoustic oscillations features in 21 cm signals from the cosmic Dark Ages