HST/ACS Hα imaging of the Carina Nebula: Outflow activity traced by irradiated Herbig-Haro Jets

Abstract

We report the discovery of new Herbig-Haro (HH) jets in the Carina Nebula, and we discuss the protostellar outflow activity of a young OB association. These are the first results of an Hα imaging survey of Carina conducted with the Hubble Space Telescope (HST)/Advanced Camera for Surveys. Adding to the one previously known example (HH 666), we detect 21 new HH jets, plus 17 new candidate jets, ranging in length from 0.005 to 3 pc. Using the Hα emission measure to estimate jet densities, we derive jet mass-loss rates ranging from 8 × 10-9 to ∼10-6 M⊙ yr-1, but a comparison to the distribution of jet mass-loss rates in Orion suggests that we may be missing a large fraction of the jets below 10-8 M⊙ yr-1. A key qualitative result is that even some of the smallest dark globules with sizes of ≲1 arcsec (0.01 pc) are active sites of ongoing star formation because we see HH jets emerging from them, and that these offer potential analogues to the cradle of our Solar system because of their proximity to dozens of imminent supernovae that will enrich them with radioactive nuclides like 60Fe. Although most proplyd candidates identified from ground-based data are dark cometary globules, HST images now reveal proplyd structures in the core of the Tr 14 cluster, only 0.1-0.2 pc from several extreme O-type stars. Throughout Carina, some HH jets have axes bent away from nearby massive stars, while others show no bend, and still others are bent toward the massive stars. These jet morphologies serve as 'wind socks'; strong photoevaporative flows can shape the jets, competing with the direct winds and radiation from massive stars. We find no clear tendency for jets to be aligned perpendicular to the axes of dust pillars. Finally, even allowing for a large number of jets that may escape detection, we find that HH jets are negligible to the global turbulence of the surrounding region, which is driven by massive star feedback. © 2010 The Authors. Journal compilation © 2010 RAS.