Galaxy Formation from a Timescale Perspective

Timescales in astronomy comprise the largest range of any scientific discipline. In the construction of physical models, this circumstance may be both a blessing and a curse. For example, galaxy evolution occurs on typical timescales of hundreds of millions of years but is affected by atomic processes on sub-second timescales, posing a challenge in analytical and, in particular, in numerical models. On the other hand, the vast dynamic range implies that we can often make meaningful predictions by simply comparing characteristic timescales of the physical processes involved. This review, aimed primarily at non-astronomer scientists, attempts to highlight some occasions in the context of galaxy formation and evolution in which comparing timescales can shed light on astrophysical phenomena, as well as some of the challenges that may be encountered. In particular, we will explore the differences and similarities between theoretical predictions of dark matter halos and the observed distribution of galaxies. The review concludes with an account of the most recent observations with the James Webb Space Telescope, and how they purportedly seem to defy the timescales of the currently accepted concordance model of the structure and evolution of the Universe, the ΛCDM model.