Analysis of the disk stability against local fragmentation, following the methodology outlined in Kratter et al. (2010). The plot reports the dependence of two dimensionless parameters, Γ and ξ, whose relation defines two regions where the disk is stable (white) or prone to fragmentation (grey). Black empty circles mark the local values of Γ and ξ within the midlplane and they are labelled according to the pointing numbers in Table 2 (P2 and P8 overlap); red and blue diamonds mark values for the north-eastern and south-western apparent spirals, respectively. The upper and lower plots compare the behaviour of an angular velocity (Ω) which is either 70% of the Keplerian value (upper), or equal to it (lower). Reference error bars are indicated in red for an inner position (largest ticks in logarithmic scale), and they account for a 10% uncertainty in the local temperature and a positional uncertainty of half the beam size.