  We present a physical model for the origin of z~2 Dust-Obscured Galaxies
(DOGs), a class of high-redshift ULIRGs selected at 24 micron which are
particularly optically faint (24/R>1000). By combining N-body/SPH simulations
of high redshift galaxy evolution with 3D polychromatic dust radiative transfer
models, we find that luminous DOGs (with F24 > 0.3 mJy at z~2 are well-modeled
as extreme gas-rich mergers in massive (~5x10^12-10^13 Msun) halos, with
elevated star formation rates (~500-1000 Msun/yr) and/or significant AGN growth
(Mdot > 0.5 Msun/yr), whereas less luminous DOGs are more diverse in nature. At
final coalescence, merger-driven DOGs transition from being starburst dominated
to AGN dominated, evolving from a "bump" to a power-law shaped mid-IR (IRAC)
spectral energy distribution (SED). After the DOG phase, the galaxy settles
back to exhibiting a "bump" SED with bluer colors and lower star formation
rates. While canonically power-law galaxies are associated with being
AGN-dominated, we find that the power-law mid-IR SED can owe both to direct AGN
contribution, as well as to a heavily dust obscured stellar bump at times that
the galaxy is starburst dominated. Thus power-law galaxies can be either
starburst or AGN dominated. Less luminous DOGs can be well-represented either
by mergers, or by massive ($M_{\rm baryon} ~5x10^11 Msun) secularly evolving
gas-rich disc galaxies (with SFR > 50 Msun/yr). By utilising similar models as
those employed in the SMG formation study of Narayanan et al. (2010), we
investigate the connection between DOGs and SMGs. We find that the most heavily
star-forming merger driven DOGs can be selected as Submillimetre Galaxies
(SMGs), while both merger-driven and secularly evolving DOGs typically satisfy
the BzK selection criteria.
