Scott Chapman

How did the Universe begin and where did our Galaxy come from? Addressing these questions involves studying the millimeter-wave light emitted and affected by processes immediately after the Big Bang (the Cosmic Microwave Background – CMB), and the near-infrared through millimetre light from distant galaxies in the early Universe undergoing major episodes of star formation. The bulk of star formation is deeply obscured by dust, with ultra-violet radiation from young, hot stars being absorbed and reradiated at long wavelengths from dust heated to ~30K. In the formative periods of galaxies in the early Universe, when star formation rates (SFRs) were high enough to form the bulk of the stars in a typical galaxy in a few mega-years, the ‘proto-galaxies’ can be almost completely invisible at optical wavelengths. Submillimeter observations provide an opportunity to measure the total luminosities of star-forming galaxies from the earliest epochs of galaxy formation, by measuring the emission from the very dust that obscures young and forming stars. Observations of submillimeter atomic and molecular transitions, complemented by nebular line diagnostics redshifted into the near- and mid-infrared enable astronomers to model the detailed physics of the interstellar media in galaxies from the nearby universe to the largest distances, and in clouds in the Milky Way.

The difficulty of observations in the near-infrared, millimeter and far-infrared wavelengths of light, both from a technological perspective and from atmospheric attenuation of the signals, has resulted in slower progress than in optical astronomy. However, ground-based and satellite observations in these wavelengths have matured over the last decade. New millimetre cameras based on superconducting detectors under development are being employed with unprecedented sensitivities. Adaptive optics is revolutionizing the ground based capabilities in the near-infrared. My research group works at the interface between instrument development in these wavelengths and astrophysical interpretation of measurements made from other facilities, with the goal of improving our understanding of the origin of our Universe and the formation of galaxies and structures within it. In Vieira, Marrone, Chapman et al. (2013, Nature), and Miller, Chapman et al. (2018, Nature) we report the discovery of significant numbers of these SPTSMGs only 500 Myr after the Big Bang, revealing the true redshift distribution of SMGs without previous biases. My large telescope allocations towards this project (ALMA, VLT, Gemini, Chandra programs) have set the context for studying these luminous galaxies.

It has also become increasingly apparent that much of the information required to understand the formation and evolution of galaxies can be gleaned from high quality fossil record data on nearby galaxies (e.g., Abadi et al. 2003, ApJ, 597, 21). Within the framework of hierarchical structure formation (e.g., White & Rees 1978), large spiral galaxies like the Milky Way or Andromeda (M31) arose from the merger of many small galaxies and protogalaxies which began coalescing at high redshift. During this process, considerable dynamical and chemical evolution took place, as the primordial galaxy fragments were assimilated, stellar populations evolved. A parallel research strain of my group has been a detailed study of the outskirts of Andromeda (M31) galaxy and its satellites.

The development of new instrumentation is crucial for future astronomy and cosmological measurements. My strategy in choosing to work on various projects has been driven primarily by pursuing my research interests in extragalactic astronomy and cosmology. Projects I lead currently include (i) developing the adaptive optics system for the GIRMOS instrument on the Gemini telescope; (ii) leading the 350 micron camera for the CCATp telescope in Chile; (iii) developing the sky chopping mirror system for the Superspec instrument on the LMT telescope.

Contact Scott at scott dot chapman “at” ronininstitute {dot} org