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We present a catalog of 840 X-ray sources and first results from a 100 ksChandra X-ray Observatory imaging study of the filamentary infrared dark cloudG014.225$-$00.506, which forms the central regions of a larger cloud complexknown as the M17 southwest extension (M17 SWex). In addition to the richpopulation of protostars and young stellar objects with dusty circumstellardisks revealed by Spitzer Space Telescope archival data, we discover apopulation of X-ray-emitting, intermediate-mass pre--main-sequence stars (IMPS)that lack infrared excess emission from circumstellar disks. We model theinfrared spectral energy distributions of this source population to measure itsmass function and place new constraints on the inner dust disk destructiontimescales for 2-8 $M_{\odot}$ stars. We also place a lower limit on the starformation rate (SFR) and find that it is quite high ($\dot{M}\ge0.007~M_{\odot}$ yr$^{-1}$), equivalent to several Orion Nebula Clusters inG14.225$-$0.506 alone, and likely accelerating. The cloud complex has notproduced a population of massive, O-type stars commensurate with its SFR. Thisabsence of very massive (${\ge}20~M_{\odot}$) stars suggests that either (1)M17 SWex is an example of a distributed mode of star formation that willproduce a large OB association dominated by intermediate-mass stars butrelatively few massive clusters, or (2) the massive cores are still in theprocess of accreting sufficient mass to form massive clusters hosting O stars.

Rapid Circumstellar Disk Evolution and an Accelerating Star Formation Rate in the Infrared Dark Cloud M17 SWex