The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. XII. The
  Perseus YSO Population as Observed with IRAC and MIPS
  The Spitzer Space Telescope mapped the Perseus molecular cloud complex with
IRAC and MIPS as part of the c2d Spitzer Legacy project. This paper combines
the observations from both instruments giving an overview of low-mass star
formation across Perseus from 3.6 to 70 micron. We provide an updated list of
young stellar objects with new classifications and source fluxes from previous
works, identifying 369 YSOs in Perseus with the Spitzer dataset. By
synthesizing the IRAC and MIPS maps of Perseus and building on the work of
previous papers in this series (Jorgensen et al. 2006, Rebull et al. 2007), we
present a current census of star formation across the cloud and within smaller
regions. 67% of the YSOs are associated with the young clusters NGC 1333 and IC
348. The majority of the star formation activity in Perseus occurs in the
regions around the clusters, to the eastern and western ends of the cloud
complex. The middle of the cloud is nearly empty of YSOs despite containing
regions of high visual extinction. The western half of Perseus contains
three-quarters of the total number of embedded YSOs (Class 0+I and Flat SED
sources) in the cloud and nearly as many embedded YSOs as Class II and III
sources. Class II and III greatly outnumber Class 0+I objects in eastern
Perseus and IC 348. These results are consistent with previous age estimates
for the clusters. Across the cloud, 56% of YSOs and 91% of the Class 0+I and
Flat sources are in areas where Av > 5 mag, indicating a possible extinction
threshold for star formation.
