Title: Inside-Out Planet Formation. IV. Pebble Evolution and Planet Formation Timescales,
Abstract: Systems with tightly-packed inner planets (STIPs) are very common. Chatterjee
& Tan proposed Inside-Out Planet Formation (IOPF), an in situ formation theory,
to explain these planets. IOPF involves sequential planet formation from
pebble-rich rings that are fed from the outer disk and trapped at the pressure
maximum associated with the dead zone inner boundary (DZIB). Planet masses are
set by their ability to open a gap and cause the DZIB to retreat outwards. We
present models for the disk density and temperature structures that are
relevant to the conditions of IOPF. For a wide range of DZIB conditions, we
evaluate the gap opening masses of planets in these disks that are expected to
lead to truncation of pebble accretion onto the forming planet. We then
consider the evolution of dust and pebbles in the disk, estimating that pebbles
typically grow to sizes of a few cm during their radial drift from several tens
of AU to the inner, $\lesssim1\:$AU-scale disk. A large fraction of the
accretion flux of solids is expected to be in such pebbles. This allows us to
estimate the timescales for individual planet formation and entire planetary
system formation in the IOPF scenario. We find that to produce realistic STIPs
within reasonable timescales similar to disk lifetimes requires disk accretion
rates of $\sim10^{-9}\:M_\odot\:{\rm yr}^{-1}$ and relatively low viscosity
conditions in the DZIB region, i.e., Shakura-Sunyaev parameter of
$\alpha\sim10^{-4}$.