number of sources considered in Davis et al. (2014) to derive R_CO;

number of ULIRGs considered in Bellocchi et al. (2013) and Arribas et al. (2012) to derive R_star and R_Hα, respectively, from the VIMOS/VLT sample and combining VIMOS/VLT with the INTEGRAL/WHT samples;

number of sources for which the R_star can be derived; Col. (4, 5, 6, 7): Effective radius derived for the CO(2–1), dust, stellar and ionized gas (i.e., Hα) emissions, respectively. In Col. 4 the ‘*’ symbol means that the molecular size was derived as a combination of the CO, [CI] and dust tracers, as a robust average size of the cold ISM phase in their systems. Column (8): Stellar mass. Column (9): References with the following code: A12 Arribas et al. (2012), B13 Bellocchi et al. (2013), C13 Cappellari et al. (2013a), D13 Davis et al. (2013), D14 Davis et al. (2014), Bo17 Bolatto et al. (2017), K20 Kaasinen et al. (2020), L19 Lang et al. (2019), Chen17 Chen et al. (2017), Chen20 Chen et al. (2020), Cheng20 Cheng et al. (2020), T17 Tadaki et al. (2017), Ba14 Barro et al. (2014), Ba16 Barro et al. (2016), CR18 Calistro Rivera et al. (2018), H16 Hodge et al. (2016), S15 Straatman et al. (2015), FS18 Förster Schreiber et al. 2018, G18 Gullberg et al. (2018), F20 Fujimoto et al. (2020), Fa20 Faisst et al. (2020), V20 Valentino et al. (2020), W20 Wilman et al. (2020), L21 Leroy et al. (2021), P21 Pereira-Santaella et al. (2021), H21 Hogan et al. (2021), Pu21 Puglisi et al. (2021). Dots “...” signify that no data are available.