The Spitzer Survey of Interstellar Clouds in the Gould Belt. V.
  Ophiuchus North Observed with IRAC and MIPS
  We present Spitzer IRAC (2.1 sq. deg.) and MIPS (6.5 sq. deg.) observations
of star formation in the Ophiuchus North molecular clouds. This fragmentary
cloud complex lies on the edge of the Sco-Cen OB association, several degrees
to the north of the well-known rho Oph star-forming region, at an approximate
distance of 130 pc. The Ophiuchus North clouds were mapped as part of the
Spitzer Gould Belt project under the working name `Scorpius'. In the regions
mapped, selected to encompass all the cloud with visual extinction AV>3, eleven
Young Stellar Object (YSO) candidates are identified, eight from IRAC/MIPS
colour-based selection and three from 2MASS K/MIPS colours. Adding to one
source previously identified in L43 (Chen et al. 2009), this increases the
number of YSOcs identified in Oph N to twelve. During the selection process,
four colour-based YSO candidates were rejected as probable AGB stars and one as
a known galaxy. The sources span the full range of YSOc classifications from
Class 0/1 to Class III, and starless cores are also present. Twelve
high-extinction (AV>10) cores are identified with a total mass of approx. 100
solar masses. These results confirm that there is little ongoing star formation
in this region (instantaneous star formation efficiency <0.34%) and that the
bottleneck lies in the formation of dense cores. The influence of the nearby
Upper Sco OB association, including the 09V star zeta Oph, is seen in dynamical
interactions and raised dust temperatures but has not enhanced levels of star
formation in Ophiuchus North.
