Star formation in the Perseus complex : a tale of seven clusters

Abstract

Following the recent advances in astrometry of Gaia DR2, I use its photometric and kinematic data 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 NGC 1333, I present five new clusters, which contain between 30 and 300 members, named Autochthe, Alcaeus, Mestor, Electryon and Heleus. I construct reliable membership lists for the seven clusters and of the dispersed population of the complex.

I investigate the youth of individual sources within the clusters, and outside, using a combination of youth indicators from Gaia, WISE, Spitzer, and Planck data. These give the relative ages of the clusters and yield lists of young sources (τ[sub](age) ≲ 5 Myr). Based on this work, IC 348 spans ages from 1 Myr up to 5 Myr. Autochthe and NGC 1333 are the youngest clusters at 1 Myr. These three clusters constitute the star-forming centers of the cloud. Heleus and Mestor have average ages of about 4 Myr while Alcaeus and Electryon are at about 5 Myr. NGC 1333, Autochthe and IC 348 have the highest disc fractions (66±14%, 58±30% and 41±7%) while the rest four clusters have fractions below ∼30%.

Finally I construct the system Mass Function (MF) for all seven clusters by determining the masses of the cluster members using 2MASS photometry. For 0.08 < m/M[sub]☉︎ < 1.4 the MF slopes are in agreement for the seven clusters and range between 0.5 and 1.3. These are by and large smaller than the Kroupa (2001) slope of 1.3.

The region of Perseus exhibits a bimodal nature in proper motion, spatial distribution, and age span. This bimodality is supported by a star-formation scenario where the seven clusters have formed from two kinematically distinct sub-clouds.