  We experimentally study the dynamics of a degenerate one-dimensional Bose gas
that is subject to a continuous outcoupling of atoms. Although standard
evaporative cooling is rendered ineffective by the absence of thermalizing
collisions in this system, we observe substantial cooling. This cooling
proceeds through homogeneous particle dissipation and many-body dephasing,
enabling the preparation of otherwise unexpectedly low temperatures. Our
observations establish a scaling relation between temperature and particle
number, and provide insights into equilibration in the quantum world.
