A background galaxy in the field of the beta Pic debris disk

TL;DR

This study uses Herschel imaging to analyze the debris disk around beta Pic, identifying a background galaxy through spectral and size comparisons, and clarifying the nature of a detected blob.

Contribution

It demonstrates that the observed blob near beta Pic is a background galaxy, not part of the debris disk, using multi-band photometry and spectral analysis.

Findings

The blob is likely a background galaxy at redshift 1.0 to 1.6.

The debris disk around beta Pic is well-resolved in Herschel bands.

The study distinguishes between disk features and background sources.

Abstract

Herschel images in six photometric bands show the thermal emission of the debris disk surrounding beta Pic. In the three PACS bands at 70 micron, 100 micron and 160 micron and in the 250 micron SPIRE band, the disk is well-resolved, and additional photometry is available in the SPIRE bands at 350 micron and 500 micron, where the disk is only marginally resolved. The SPIRE maps reveal a blob to the southwest of beta Pic, coinciding with submillimetre detection of excess emission in the disk. We investigated the nature of this blob. Our comparison of the colours, spectral energy distribution and size of the blob, the disk and the background sources shows that the blob is most likely a background source with a redshift between z =1.0 and z = 1.6.