Recent star formation in the Lupus clouds as seen by Herschel

TL;DR

This study uses Herschel and Spitzer data to analyze star formation in Lupus clouds, revealing different evolutionary stages and star formation efficiencies across the clouds.

Contribution

It provides a comprehensive census of prestellar and young stellar objects in Lupus, highlighting the clouds' star formation histories and evolutionary states.

Findings

Lupus III is the most evolved cloud with high SFE and declining SFR.

Lupus I is undergoing a major star formation event with increasing SFR.

Lupus IV shows increasing SFR but fewer prestellar sources, indicating early star formation stage.

Abstract

We present a study of the star formation histories of the Lupus I, III, and IV clouds using the Herschel 70-500 micron maps obtained by the Herschel Gould Belt Survey Key Project. By combining the new Herschel data with the existing Spitzer catalog we obtained an unprecedented census of prestellar sources and young stellar objects in the Lupus clouds, which allowed us to study the overall star formation rate (SFR) and efficiency (SFE). The high SFE of Lupus III, its decreasing SFR, and its large number of pre-main sequence stars with respect to proto- and prestellar sources, suggest that Lupus III is the most evolved cloud, and after having experienced a major star formation event in the past, is now approaching the end of its current star-forming cycle. Lupus I is currently undergoing a large star formation event, apparent by the increasing SFR, the large number of prestellar objects with respect to more evolved objects, and the high percentage of material at high extinction (e.g., above A_V=8 mag). Also Lupus IV has an increasing SFR; however, the relative number of prestellar sources is much lower, suggesting that its star formation has not yet reached its peak.