Near-Infrared Observations of Massive Protostellar Outflows

Abstract

Massive stars (M∗ ≳ 8M⊙) play important roles in determining the physical and chemical evolution of galaxies, thus exerting significant influence on the Universe. However, the physical mechanisms behind their formation remain poorly understood. Observations of massive stars in their formation stages are utterly challenging as they form deeply embedded in their parental clouds. Observations of jets and outflows in high-mass star-forming regions can provide crucial information about the physical processes governing their formation. We aim to characterise the star-forming region G45.47+0.05 in the near-infrared (NIR) using both imaging and spectroscopy. We unveil this region via outflow activity identification, association to their driving sources, and obtaining physical properties through Spectral Energy Distribution (SED) of these Young Stellar Objects (YSOs). Additionally, we compare our results with various star-forming tracers reported in the literature. In this work, we identify four infrared sources (IRSs) in the region G45.47+0.05, which are classified as YSOs candidates through their spectra. SED fitting indicates that these four IRSs are massive protostars or are expected to end up their formation as such. We detect NIR jets via [FeII] observations at 1.64μm obtained with the Hubble Space Telescope, as well as K−band (centred at 2.2μm) observations with the Very Large Telescope. The detection of star-forming tracers [FeII], H2, and Brγ reveals that the four IRSs are young, potentially jet-driving sources. For the main source, G45.47-IRS1, we identify four jet-knots. The alignment of various knots disclose the direction of two potential jet-axes, suggesting that the main source consists of an unresolved binary system. For the source G45.47-IRS4, we find jet-knot extended emission which have not been reported before. The findings presented in this thesis shed new light on the G45.47+0.05 region, including the detection of new jet knots, as well as the characterisation of YSOs candidates. These advances motivate further observational follow-up with next-generation telescopes, such as the James Webb Space Telescope.