Spitzer-MIPS Observations of the eta Cha Young Association

TL;DR

This study used the Spitzer Space Telescope to observe the eta Chamaeleontis young stellar association in the far-infrared, detecting circumstellar disks around many members and analyzing their properties to understand disk evolution.

Contribution

First detailed far-infrared survey of eta Cha association revealing diverse disk types and evolutionary stages within a young stellar group.

Findings

All 16 members detected at 24 um; some at 70 and 160 um.

Approximately 62.5% of members show infrared excess indicating disks.

Presence of various disk optical depths and inner holes suggests a key evolutionary stage.

Abstract

We have mapped the eta Chamaeleontis young stellar association in the far-infrared with the Multiband Imaging Photometer for Spitzer (MIPS) on the Spitzer Space Telescope. All sixteen members within the map region were detected at 24 um, along with five members at 70 um and two at 160 um. Ten stars show far-infrared excess emission indicating the presence of circumstellar disks; six of these have central clearings as evidenced by the onset of excess emission at >5 um. No new infrared excess sources are identified among the 113 2MASS field stars with 24 um photometry but not seen as X-ray sources, indicating that membership lists derived from X-ray surveys are reasonably complete. Circumstellar disks in the eta Cha association span the range from 1e-1 to 1e-4 in their fractional infrared luminosity, with a median Ldust /Lstar of 0.04. The presence of optically thick, optically thin, and intermediate optical depth disks within the same stellar group, in combination with the large fraction of disks with inner holes, indicates that the Cha association represents a crucial stage in circumstellar disk evolution.