  We have studied the young low-mass pre-main sequence (PMS) stellar population
associated with the massive star-forming region DR 21 by using archival X-ray
Chandra observations and by complementing them with existing optical and IR
surveys. The Chandra observations have revealed for the first time a new highly
extincted population of PMS low-mass stars previously missed in observations at
other wavelengths. The X-ray population exhibits three main stellar density
peaks, coincident with the massive star-forming regions, being the DR 21 core
the main peak. The cross-correlated X-ray/IR sample exhibits a radial
"Spokes-like" stellar filamentary structure that extends from the DR 21 core
towards the northeast. The near IR data reveal a centrally peaked structure for
the extinction, which exhibits its maximum in the DR 21 core and gradually
decreases with the distance to the N-S cloud axis and to the cluster center. We
find evidence of a global mass segregation in the full low-mass stellar
cluster, and of an stellar age segregation, with the youngest stars still
embedded in the N-S cloud, and more evolved stars more spatially distributed.
The results are consistent with the scenario where an elongated overall
potential well created by the full low-mass stellar cluster funnels gas through
filaments feeding stellar formation. Besides the full gravitational well,
smaller-scale local potential wells created by dense stellar sub-clusters of
low-mass stars are privileged in the competition for the gas of the common
reservoir, allowing the formation of massive stars. We also discuss the
possibility that a stellar collision in the very dense stellar cluster revealed
by Chandra in the DR 21 core is the origin of the large-scale and
highly-energetic outflow arising from this region.
