The substructure of the Perseus star-forming region: a survey with Gaia DR2

We use photometric and kinematic data from Gaia DR2 to explore the structure of the star-forming region associated with the molecular cloud of Perseus. Apart from the two well-known clusters, IC 348 and NGC1333, we present five new clustered groups of young stars, which contain between 30 and 300 members, named Autochthe, Alcaeus, Heleus, Electryon, and Mestor. We demonstrate that these are co-moving groups of young stars, based on how the candidate members are distributed in position, proper motion, parallax, and colour-magnitude space. By comparing their colour-magnitude diagrams to isochrones, we show that they have ages between 1 and 5Myr. Using 2MASS and WISE colours, we find that the fraction of stars with discs in each group ranges from 10 to similar to 50 per cent. The youngest of the new groups is also associated with a reservoir of cold dust, according to the Planck map at 353 GHz. We compare the ages and proper motions of the five new groups to those of IC 348 and NGC1333. Autochthe is clearly linked with NGC1333 and may have formed in the same star formation event. The seven groups separate roughly into two sets that share proper motion, parallax, and age: Heleus, Electryon, and Mestor as the older set, and NGC1333 and Autochthe as the younger set. Alcaeus is kinematically related to the younger set, but at a more advanced age, while the properties of IC 348 overlap with both sets. All older groups in this star-forming region are located at higher galactic latitude.

Automated summary

Using Gaia DR2 data, we identified five new young star clusters in the Perseus molecular cloud region, with ages between 1 and 5 million years and disk fractions ranging from 10% to 50%. The kinematic comparison showed two distinct sets of groups, with older groups at higher galactic latitude and younger groups sharing proper motion and age characteristics. Autochthe is closely linked to NGC1333, indicating a common origin in the star formation event.