Galactic mass-losing AGB stars probed with the IRTS. II.

We are using the 2002 data-release from the Japanese space experiment IRTS to investigate the spatial distribution of galactic mass-losing (>2x 10^-8 M_sund) AGB stars and the relative contribution of C-rich and O-rich ones to the replenishment of the ISM. Our sample contains 126 C-rich and 563 O-rich sources which are sorted on the basis of the molecular bands observed in the range 1.4-4.0 mu m, and for which we estimate distances and mass loss rates from near-infrared photometry (K and L'). There is a clear dependence on galactocentric distance, with O-rich sources outnumbering C-rich ones for r_GC< 8 kpc, and the reverse for r_GC> 10 kpc. The contribution to the replenishment of the ISM by O-rich AGB stars relative to C-rich ones follows the same trend. Although they are rare ( ~ 10% in our sample), sources with 10^-6 M_sund < dot {M} < 10^-5 M_sund dominate the replenishment of the ISM by contributing to ~ 50% of the total of the complete sample. We find 2 carbon stars at more than 1 kpc from the Galactic Plane, that probably belong to the halo of our Galaxy.

The complete Tables \ref{tab_C-rich} and \ref{tab_O-rich} are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/403/943}