Constraints on the History of Tidal Interactions/Mergers over the Last 8 Gyr

VC = 1 = E (non-interacting, smooth, pure bulge)	No strong morphological distortion. No gas/dust: looks very smooth. Circular/elliptical in projection. No disk signature, such as bar/spiral arm. Pure bulge: steeply declining surface brightness (SB) profile from the center outward, with no obvious break. NB: The criteria above will catch E (spheroidal systems) but also some S0. For cases where morphology is consistent with either 1 = E or 3 = S0/Sa, we assign VC = 1 = E. NB: Local examples = NGC 720 (E5) or NGC 1351 (S0).
VC = 3 = S0/Sa (non-interacting, smooth, bulge and disk)	No strong morphological distortion. No or little gas/dust: looks smooth. Circular/elliptical in projection. Bulge and disk: steeply declining central SB in bulge region, with a slowly declining SB proile in outer disk region. May have disk signatures such as a bar/spiral arms. But in hot or gas-poor disks these signatures are absent. NB: For cases where morphology is consistent with both 1 = E or 3 = S0/Sa, we assign VC = 1 = E. NB: Local examples = NGC 1351 (S0) or NGC N622 (SAab).
VC = 5 = Sb-Sd (non-interacting, gas and dust, bulge and disk)	No strong morphological distortion. Has gas/dust: galaxy looks clumpy, with structure (dust lane, SF regions). Circular/elliptical in projection. Bulge and disk: steeply declining central SB in bulge region, with a slowly declining SB proile in outer disk region. May have disk signatures such as a bar/spiral arms, but in unbarred disks, this signature will be absent. NB: Local example = NGC674 (SABc).
VC = 7 = Irr (non-interacting, local small-scale asymmetries)	These galaxies have small-scale asymmetries (as opposed to class 93/95). We consider small-scale asymmetries to be asymmetries that are correlated on scales of a few hundred pc, in contrast to large-scale asymmetries that are correlated on scales of several kpc. These small-scale asymmetries often consist of hot spot HII regions, and make up a "chicken pox" morphology. The reason we attempt to distinguish between small-scale and large-scale asymmetries is that small scale asymmetries can be internally driven by low v/σ and local SF, while large-scale asymmetries in class 93/95 are often due to an external disturbance. Lots of gas/dust: galaxy looks very clumpy, with lots of structure (dust lane, SF regions). NB: Local examples = LMC, SMC.
VC = 93 (interacting, high contrast large-scale distortions)	These galaxies have large-scale distortions that make up a high fraction (>30% as judged by eye) of the total light. Large-scale distortions are correlated on scales of ~1 kpc and include the following: tidal tails, shells, arcs, ripples, warps, double nuclei, an odd number of spiral arms, an even number of spiral arms, where some arms are strongly asymmetric with respect to other arms. NB: Local examples = Arp 244, NGC6745, NGC5426/5427, NGC4038/4039.
VC = 95 (interacting, low contrast large-scale distortions)	These galaxies have large-scale distortions that make up a low fraction (<30% as judged by eye) of the total light. NB: Local examples = NGC2782, M74, NGC1186, NGC3504, NGC6493.