Stockholm University, Sweden
The outskirts of galaxies have been studied from multiple perspectives for the past few decades. However, it is still unknown if all galaxies have clear-cut edges like everyday objects. In this contribution, I will tell you the story of how the development of imaging in astronomy, from the use of photographic plates in the 1930s to current CCD imaging, impacted the definition and measurement of galaxy size. I will then present physically motivated criteria to define the edges of galaxies, based on the gas density threshold required for either past or ongoing in-situ star formation. The analysis of 1000 nearby galaxies using ultra-deep optical imaging will be discussed, including how the radial location of their edges (R_edge) depends on galaxy morphology and global stellar mass. Remarkably, the stellar mass-size relation using R_edge as a physically motivated galaxy size measure has a very narrow intrinsic scatter (< 0.06 dex) over nearly four orders of magnitude in stellar mass. I will discuss the implication of these findings on the growth and evolution of galaxies.
2022 November 30, 13:30
Observatório Astronómico de Lisboa (Seminar room)
Tapada da Ajuda, 1349-018 Lisboa