That paper uses a nice unit I didn't know of; the 'Jansky' (Jy) ' 'non-SI unit of spectral flux density' https://en.wikipedia.org/wiki/Jansky
This is true for all SI units. Newton, watt, and joule are all lowercase, unless they appear at the beginning of a sentence or when you're referring to the original scientists.
People often get confused because the abbreviations for those units are capitalized.
[0] https://www.iau.org/publications/proceedings_rules/units/