Which tend to be oriented at right angles to the spiral arm nearest to our Solar System. (explanation, see below.)
According to Quantum FFF Theory: originated by the Big Bang Dual Splinter Black Holes forming Herbig Haro twin Bowshocks with stars in between,
see also: The Origin of Universal Structure: Herbig Haro -Electric Dark Matter Black Hole- Systems. http://vixra.org/pdf/1904.0599v1.pdf
see also: http://vixra.org/pdf/1905.0123v2.pdf
and: https://phys.org/news/2019-08-gaia-untangles-starry-milky.html?fbclid=IwAR2DqDKCAHhCj8EXLK2_DFCCluYvM8tP5pEksa7qTIzkbtmXmhqQ1zCDRp8
see also: https://twitter.com/leo_vuyk/status/725315620837924866
The Great misconception in Astrophysics: H H Bowshocks and Cometary Globules, are not seen as Dark Matter Black Holes