870 Micron Dust Continuum of the Youngest Protostars in Ophiuchus
  We present a 0.15$^{\prime\prime}$ resolution (21 au) ALMA 870 $\mu$m
continuum survey of 25 pointings containing 31 young stellar objects in the
Ophiuchus molecular clouds. Using the dust continuum as a proxy for dust mass
and circumstellar disk radius in our sample, we report a mean mass of
2.8$^{+2.1}_{-1.3}$ and 2.5$^{+9.2}_{-1.1}$ M$_{\oplus}$ and a mean radii of
23.5$^{+1.8}_{-1.2}$ and 16.5$^{+2.8}_{-0.9}$ au, for Class I and Flat spectrum
protostars, respectively. In addition, we calculate the multiplicity statistics
of the dust surrounding young stellar objects in Ophiuchus. The multiplicity
fraction (MF) and companion star fraction (CSF) of the combined Class I and
Flats based solely on this work is 0.25 $\pm$ 0.09 and 0.33 $\pm$ 0.10,
respectively, which are consistent with the values for Perseus and Orion. While
we see clear differences in mass and radius between the Ophiuchus and
Perseus/Orion protostellar surveys, we do not see any significant differences
in the multiplicities of the various regions. We posit there are some
differences in the conditions for star formation in Ophiuchus that strongly
affects disk size (and consequently disk mass), but does not affect system
multiplicity, which could imply important variation in planet formation
processes.
