Eta Carinae as seen by ALMA

 

Zulema Abraham (IAG)

 

Eta Carine was mapped with 23 antennas of the AL MA array in November 2012, in the continuum of  3 mm, 1.3 mm, 1 mm and  454 microns, the lowest submillimeter wavelength ever achieved, with resolution of 0.4 arcsec. Hydrogen recombination lines H42 alpha, H40 alpha, H30 alpha,  H28 alpha and H22 alpha were also detected at these wavelengths. The radio maps showed a very strong compact structure coincident with the position of the binary system and spectrum of bremsstrahlung emission,  with the turn over between optically thick and thin spectrum between 3 and 1.3 mm. The radio recombination lines are even stronger than the continuum, even at 454 microns, indicating departure of LTE and that the emitting region has electron densities in excess of 10^7 /cm^3 . The central velocity of the recombination lines coincides with the velocity of the Weigelt blobs. Besides the very strong unresolved source the radio maps show weak emission that extends for a few arc sec, with a structure similar to what was observed at higher wavelengths.