The Evolution of Circumstellar Disks Surrounding Intermediate Mass Stars: IC 1805

TL;DR

This study characterizes circumstellar disks around intermediate and high-mass stars in IC 1805, revealing their frequency, types, and evolutionary stages through multi-wavelength photometry and spectral analysis.

Contribution

It provides a detailed classification of disk types around stars >2 Msun in IC 1805 and assesses their evolutionary status based on spectral energy distributions.

Findings

Optically thick accretion disks are rare (~2%) among stars with 2-4 Msun.

Approximately 10% of stars with 2-4 Msun have evolved disks with various SED types.

Four classes of evolved disks are identified based on their spectral energy distributions.

Abstract

We report the results of a study of the intermediate and high mass stars in the young, rich star-forming complex IC 1805, based on a combination of optical, near-infrared, and mid-infrared photometry, and classification spectra. These data provide the basis for characterizing the masses and ages for stars more massive than ~2 Msun and enable a study of the frequency and character of circumstellar disks associated with intermediate- and high-mass stars. Optically thick accretion disks among stars with masses 2 < M/Msun <4 are rare (~2% of members) and absent among more massive stars. A larger fraction (~10%) of stars with masses 2 < M/Msun < 4 appear to be surrounded by disks that have evolved from the initial optically thick accretion phase. We identify four classes of such disks. These classes are based on spectral energy distributions (SEDs) of excess emsission above photospheric levels: disks that are (1) optically thin based on the magnitude of the observed excess emission from 2 to 24 um; (2) optically thin in their inner regions (r< 20 AU) and optically thick in their outer regions; (3) exhibit empty inner regions (r < 10 AU) and optically thin emission in their outer regions; and (4) exhibit empty inner regions and optically thick outer regions. We discuss, and assess the merits and liabilities of, proposed explanations for disks exhibiting these SED types and suggest additional observations that would test these proposals.