VLBI potential of the ALMA telescope in the millimetre

International audienceVLBI is not currently supported in the present ALMA construction plan. How- ever, the ALMA high gain antennas are equipped with receivers spanning several fre- quency ranges of interest to perform future mil- limetre (mm)/submillimetre (submm) VLBI ob- servations. The phased outputs of the full ALMA array or of subsets of the ALMA an- tennas will be supported in the future. In the mm/submm domain where spatial resolution is high but sensitivity is low in general, addition of the large ALMA collecting area to existing or fu- ture VLBI arrays would provide a definite detec- tion or mapping advantage. Fine details of com- pact components in bright AGNs and highly red- shifted sources could be revealed with good sen- sitivity −even though the brightest sources could remain unresolved with the longest terrestrial baselines. We briefly comment on the impor- tance of relatively short VLBI baselines (in the 100–1000 km range) to: (i) map the mm/submm cosmic maser sources excited in evolved stars or galactic star-forming regions; (ii) perform high precision astrometry of nearby stars. Finally, on the basis of recent ideas discussed in the ALMA correlator team, we briefly comment on the abil- ity of the ALMA correlator to support VLBI op- eration