Left: three-color image of the Mon R2 cluster-forming hub-filaments system. Red: H₂ column density map derived from Herschel SPIRE and PACS observations (Didelon et al. 2015), green: 1.65 μm band of the Two Micron All Sky Survey (Skrutskie et al. 2006), and blue: 560 nm band of the Digitalized Sky Survey (Lasker et al. 1990). Center: Herschel H₂ column density (in cm⁻², Didelon et al. 2015). The black polygon shows the area surveyed with the IRAM-30 m telescope, while the white box corresponds to the inner 0.7 pc × 0.7 pc around the central hub and zoomed in the right panel. Right: Herschel H₂ column density (in cm⁻²) of the central hub of Mon R2. Gray contours show the H¹³CO⁺ (3 →2) emission tracing the high-density molecular gas (Treviño-Morales et al. 2014). The red star gives the position of IRS 1 (with coordinates α(J2000) = 06^h 07^m 46.2^s, δ(J2000) = − 06°23′08.3″). White stars indicate the positions of infrared sources. The white circle indicates the beam size of the IRAM-30 m telescope at 100 GHz(see Sect. 2). The colored symbols are the sources identified by Rayner et al. (2017): pink stars are protostars, green circles are bound clumps, and red triangles are unbound clumps.