and to confirm the presence of photodissociation regions. The action of the WR star HD157504 on the surrounding gas was also investigated. The molecular mass in the complex is estimated to be (4$\pm$2)$\times$10$^5$ . Mean electron densities derived from the radio data suggest electron densities $>$200 , indicating that NGC6357 is a complex formed in a region of high ambient density. The known massive stars in Pis24 and a number of newly inferred massive stars are mainly responsible for the excitation and photodissociation of the parental molecular cloud.
author:
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    C.E. Cappa$^{1,2}$[^1], R. Barbá$^{3,4}$, N.U. Duronea$^{1}$, J. Vasquez$^{1,2}$, E.M. Arnal$^{1,2}$, W.M. Goss$^{5}$, and E. Fernández Lajús$^{2,6}$\
    $^{1}$Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET), C.C. No. 5, 1894 Villa Elisa, Argentina\
    $^{2}$Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina\
    $^{3}$Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE-CONICET), Av. España Sur 1512, J5402DSP San Juan, Argentina\
    $^4$Departamento de Física, Universidad de La Serena, Cisternas 1200 Norte, La Serena, Chile\
    $^{5}$National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, USA\
    $^{6}$Instituto de Astrofísica de La Plata (IALP-CONICET), Paseo del Bosque s/n, 1900, La Plata, Argentina
date: 'Accepted 