Herschel observations of the nebula M1-67 around the Wolf-Rayet star WR
  124
  Infrared Herschel imaging and spectroscopic observations of the nebula M1-67
around the Wolf-Rayet star WR 124 have been obtained along with optical imaging
observations. The infrared images reveal a clumpy dusty nebula that extends up
to 1 pc. The comparison with the optical images shows that the ionized gas
nebula coincides with the dust nebula, the dust and the gas being mixed
together. A photodissociation region is revealed from the infrared
spectroscopic analysis. The analysis of the infrared spectrum of the nebula,
where forbidden emission lines of ionized elements were detected, showed that
the nebula consists of mildly processed material with the calculated abundance
number ratios being N/O = 1.0 +/- 0.5 and C/O = 0.46 +/- 0.27. Based on a
radiative transfer model, the dust mass of the nebula was estimated to be 0.22
Msun with a population of large grains being necessary to reproduce the
observations. The comparison of the mass-loss rate and the abundance ratios to
theoretical models of stellar evolution led to the conclusion that the nebular
ejection took place during a RSG/YSG evolutionary phase of a central star with
an initial mass of 32 Msun.
