The Galaxy Evolution Years (1976-1984)

2. The Galaxy Evolution Years (1976-1984) Pioneered instrumental and observing techniques to measure the right kind of stuff for galaxies.

3. Common Theme: Evolution of Forms • Evolution of the land: subtleties of change in the desert landscape • Evolution of circumstellar material: from crud to planets • Evolution of Galaxies: from empty darkness to physical forms

4. Bothun-Strom Connection • One of his early papers stole my thesis title • Establishing a connection was initially difficult • Found common ground in 1982 • Hermann and the Blue Toad Misery Club • St. Louis Cardinals • Teaching at Amherst and softball ringer(1983)

5. We Start in 1976 • Photographic detectors predominate  issues of photometric calibration are rampant; Galaxy morphology is different on non-linear compared to linear detectors • The Hubble Sequence: Physical, Transformative or Transient • Density wave theory was popular  widely thought to adequately account for observed morphologies

6. Continuing The Universe in 1976 • The extensive nature of the dark matter component in galaxies was unknown • There were no known massive low surface brightness galaxies • The complex nature of the hierarchical clustering of galaxies was not even imagined by anyone. • Aperture photometry dominates our measurements of galaxies (hard work).

7. Properties of Galaxies –what can be measured? • Shape, structure (surface photometry), morphology • Stellar populations – young (optical), old (infrared) • Dynamics – rotation curves • Bulge/Halo properties • Abundance gradients (as related to density waves)

8. The Strom’s Legacy • Were really the first to systematically probe and integrate the various measurable properties of galaxies so that some coherent theory might arise • This approach influenced other “young” researchers at the time to enjoy the thrills of constant data overload

9. Legacy Chronology • Initial focus is on Abundance Gradients

10. Next: Integration of Wavelengths • This approach would prove to be a hallmark of Strom’s work and remember, detectors sucked back then. • This work was substantial and would allow for the structure of disk galaxies to be looked at in a new way

11. Next: Integration of Dynamics and Environmental Influences • To help understand variation in spiral arm strength/definition and prevalence of smooth arm spirals in clusters

12. Next: Size Matters • A prophetic statement: “… the true sizes of spiral galaxies must be considerably larger than currently believed”

13. Next: Pundit Time • After a mere 3 years of this effort:

14. And Just when you have it all figured out and wrote a review • Something unexpected comes along:

15. And then its time to move on • Perhaps its coincidental, but one can’t help wonder if the first author of this last paper helped drive this change in direction

16. So Where are we Today • Galaxies Look Prettier

17. Today • Massive LSB galaxies are known to exist (but, alas, they are not very pretty and are mostly just noise)

18. Today • Baryon’s don’t matter

19. Today • Galaxies are clustered in far more complex ways than anyone could ever have imagined. • Encounters/environmental influence is likely therefore larger

20. But what do we know Today? • Why is the Baryonic mass fraction of galaxies nearly constant? (Cortese etal 2008) • Why don’t galaxies have hard edges if star formation is density driven? (XUV disks) • Why is the Galactic Halo still being formed from stars streaming in? (SDSS new LG members) • What determines how many stars form in the first generation and how much material is left over (similar to planetary disk phenomena) • How does galaxy assembly really work?

21. Summary • So galaxy formation evolution, like planet formation, has gotten a lot more complicated. New data simply reminds us of all that we do not know. • Strom’s legacy as an astronomer lies in commitment to leverage all wavelengths to get a fully integrated physical view of the system. This how all of astronomy should be done.