Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster

TL;DR

This study uses Spitzer and 2MASS data to analyze the structure and evolution of the young embedded cluster NGC 1333, revealing its spatial distribution, disk fraction, and dynamical state.

Contribution

It provides a detailed spatial and evolutionary analysis of NGC 1333 using IR-excess identified members, highlighting its elongated shape and non-virialized, young dynamical state.

Findings

83% disk fraction among pre-main sequence stars

Distinct spatial distributions of Class I and II sources

Cluster is elongated and not in virial equilibrium

Abstract

We present a comprehensive analysis of structure in the young, embedded cluster, NGC 1333 using members identified with Spitzer and 2MASS photometry based on their IR-excess emission. In total, 137 members are identified in this way, composed of 39 protostars and 98 more evolved pre-main sequence stars with disks. Of the latter class, four are transition/debris disk candidates. The fraction of exposed pre-main sequence stars with disks is 83% +/- 11%, showing that there is a measurable diskless pre-main sequence population. The sources in each of the Class I and Class II evolutionary states are shown to have very different spatial distributions relative to the distribution of the dense gas in their natal cloud. However, the distribution of nearest neighbor spacings among these two groups of sources are found to be quite similar, with a strong peak at spacings of 0.045 pc. Radial and azimuthal density profiles and surface density maps computed from the identified YSOs show that NGC 1333 is elongated and not strongly centrally concentrated, confirming previous claims in the literature. We interpret these new results as signs of a low velocity dispersion, extremely young cluster that is not in virial equilibrium.