Hidden depths in the local Universe: The Stellar Stream Legacy Survey

Martínez-Delgado, David; Cooper, Andrew P.; Román, Javier; Pillepich, Annalisa; Erkal, Denis; Pearson, Sarah; Moustakas, John; Laporte, Chervin F. P.; Laine, Seppo; Akhlaghi, Mohammad; Lang, Dustin; Makarov, Dmitry; Borlaff, Alejandro S.; Donatiello, Giuseppe; Pearson, William J.; Miró-Carretero, Juan; Cuillandre, Jean-Charles; Domínguez, Helena; Roca-Fàbrega, Santi; Frenk, Carlos S.; Schmidt, Judy; Gómez-Flechoso, María A.; Guzman, Rafael; Libeskind, Noam I.; Dey, Arjun; Weaver, Benjamin A.; Schlegel, David; Myers, Adam D.; Valdes, Frank G.
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Astronomy and Astrophysics

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Context. Mergers and tidal interactions between massive galaxies and their dwarf satellites are a fundamental prediction of the Lambda-cold dark matter cosmology. These events are thought to provide important observational diagnostics of non-linear structure formation. Stellar streams in the Milky Way and Andromeda are spectacular evidence for ongoing satellite disruption. However, constructing a statistically meaningful sample of tidal streams beyond the Local Group has proven a daunting observational challenge, and the full potential for deepening our understanding of galaxy assembly using stellar streams has yet to be realised.
Aims: Here we introduce the Stellar Stream Legacy Survey, a systematic imaging survey of tidal features associated with dwarf galaxy accretion around a sample of ∼3100 nearby galaxies within z ∼ 0.02, including about 940 Milky Way analogues.
Methods: Our survey exploits public deep imaging data from the DESI Legacy Imaging Surveys, which reach surface brightness as faint as ∼29 mag arcsec−2 in the r band. As a proof of concept of our survey, we report the detection and broad-band photometry of 24 new stellar streams in the local Universe.
Results: We discuss how these observations can yield new constraints on galaxy formation theory through comparison to mock observations from cosmological galaxy simulations. These tests will probe the present-day mass assembly rate of galaxies, the stellar populations and orbits of satellites, the growth of stellar halos, and the resilience of stellar disks to satellite bombardment.