The circumbinary spiral arms of L1551 IRS 5: a new discovery with ALMA

Most solar-type stars are created in multiple star systems. One of the effects of how the presence of a companion star influences the circumstellar environment is the formation of circumbinary disks surrounding circumstellar disks. Planetary formation in these systems is affected by the influence the multiple components have over the gas and dust. For example, the two stars truncate each other's disks inhibiting the formation of planets. On the other hand, circumbinary disks can feed material into the circumstellar disks and enhance planetary formation. L1551 IRS 5 is an interesting target to study the effects of multiplicity over dust and gas dynamics. The system is composed by a circumbinary disk surrounding two circumstellar disks, each surrounding a low mass star. Here we present ALMA observations of the 1.3 mm continuum at 20 au resolution in which we resolve both circumstellar disks and, for the first time, resolve structural details in the circumbinary disk. The circumbinary disk has a radius of ~100 au and it is composed of three spiral arms: two spiral arms to the south and one spiral arm to the north, which appears to be connected to the northern circumstellar disk