  The relative importance of density and phase fluctuations in ultracold one
dimensional atomic Bose gases is investigated. By defining appropriate
characteristic temperatures for their respective onset, a broad experimental
regime is found, where density fluctuations set in at a lower temperature than
phase fluctuations. This is in stark contrast to the usual experimental regime
explored up to now, in which phase fluctuations are largely decoupled from
density fluctuations, a regime also recovered in this work as a limiting case.
Observation of the novel regime of dominant density fluctuations is shown to be
well within current experimental capabilities for both $^{23}Na$ and $^{87}Rb$,
requiring relatively low temperatures, small atom numbers and moderate aspect
ratios.
