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Cold streams: detectability, relation to structure and characteristics
Tobias Goerdt
Universidad AutСnoma de Madrid with Daniel Ceverino, Andi Burkert, Avishai Dekel, Amiel Sternberg


Cold streams


Detectability in absorption: Computed sky covering fraction
· Very low sky covering fraction · Low metallicity in streams


Stacked absorption line profiles
· Central geometry / 'down the barrel' · In agreement with Steidel et al. (2010) or BouchИ et al. (2013)


Emission: Lyman alpha blobs
· Cold streams loose potential energy released as Ly alpha photons. · Computed vs. Observed Surface brightness maps


Ly blob luminosity function
· Mass luminosity scaling relation correlated with Sheth Tormen mass function · Observational data from Matsuda et al. (2004, 2009)


Relation to structure:
· Ibata et al: Andromeda: thin disk of satellites · Cold streams carry clumps · Consequence: Coplanar satellite structure!


Relation to structure
· Double check with simulations: · High z: cold stream activity with clumps · Low z: Coplanar structure of satellites


Inflow velocity
· In units of virial velocity · Constant with radius · Power law with redshift and host halo mass · Emerging equation:


· Double Gaussian · Represents mergers and smooth infall · Observationally found by Sargent et al. (2012): star formation: main sequence | starburst activity

Inflow distribution


· Detectability in absorption:
­ Difficult (low sky covering fraction / metallicity)

· Cold stream emission: Ly blobs
­ Simulation maps very similar to observations in extent, shape, luminosity ­ Luminosity function fits data

· Relation to structure:
­ Thin satellite disks: natural consequence of streams

· Characteristics:
­ Velocity vs. radius: constant ­ Velocity vs. mass or redshift: power law ­ Inflow distribution: double Gaussian (like Sargent et al's star formation observations)