Steve Strom – The Galaxy Evolution Years (1976-1984)

Pioneered instrumental and observing techniques to measure the right kind of stuff for galaxies.

The Universe in 1976

Photographic detectors predominate Dark Matter wasn’t an issue The hierarchical clustering pattern for

galaxies was not well known yet There were no large low surface brightness

galaxies Density wave theory was popular Early galaxies lived in clusters of galaxies

Properties of Galaxies

Shape, structure (surface photometry), morphology Stellar populations – young (optical), old (infrared) Dynamics – rotation curves Bulge/Halo properties Abundance gradients (as related to density waves) Environment/interaction index

Strom’s Legacy

Was really the first to systematically probe and integrate the various measurable properties of galaxies so that some coherent theory might arise

His approach influenced other “young” researchers at the time to enjoy the thrills of constant data overload

Legacy ChronologyLegacy Chronology

Initial focus is on Abundance Initial focus is on Abundance GradientsGradients

Next: Integration of Next: Integration of WavelengthsWavelengths

This approach would prove to be a This approach would prove to be a hallmark of Strom’s work and hallmark of Strom’s work and remember, detectors sucked back remember, detectors sucked back then.then.

Next: Integration of Dynamics and Environmental Influences To help understand variation in spiral arm

strength/definition and prevelance of smooth arm spirals in clusters

Next: Size MattersNext: Size Matters

A prophetic statement: “… A prophetic statement: “… the true sizes the true sizes of spiral galaxies must be considerably of spiral galaxies must be considerably larger than currently believed”larger than currently believed”

Next: Pundit Time

After a mere 3 years of this effort:

And Just when you have it all figured out and wrote a review

Something unexpected comes along:

And then its time to move on

To the intense study of bi-polar jets and other micro physics in star forming regions.

Perhaps its coincidental, but one can’t help wonder if the first author of this last paper helped drive this change in direction

So Where are we TodaySo Where are we Today

Galaxies Look PrettierGalaxies Look Prettier

TodayToday

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

TodayToday

Baryon’s don’t matterBaryon’s don’t matter

TodayToday

Galaxies are clustered in far more Galaxies are clustered in far more complex ways than anyone could ever complex ways than anyone could ever have imagined.have imagined.

Encounters/environmental influence is Encounters/environmental influence is likely therefore largerlikely therefore larger

But what do we know But what do we know Today?Today? Why is the Baryonic mass fraction of Why is the Baryonic mass fraction of

galaxies a constant?galaxies a constant? Why don’t galaxies have hard edges if Why don’t galaxies have hard edges if

star formation is density driven?star formation is density driven? Why is the Galactic Halo still being Why is the Galactic Halo still being

formed from stars streaming in?formed from stars streaming in? What determines how many stars in the What determines how many stars in the

dark matter dominated gravitational dark matter dominated gravitational potential form in the first generation.potential form in the first generation.

How does galaxy assembly really work?How does galaxy assembly really work?

SummarySummary

So galaxy evolution has gotten a lot So galaxy evolution has gotten a lot more complicated.more complicated.

We need another pioneer like Strom We need another pioneer like Strom to help make sense of it allto help make sense of it all

Strom’s legacy as a scientist is a Strom’s legacy as a scientist is a model of how to leverage all model of how to leverage all wavelengths to get a fully integrated wavelengths to get a fully integrated physical view. We should all physical view. We should all remember this is how astronomy is remember this is how astronomy is done.done.