The Galaxy Evolution Years (1976-1984)

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

galaxies.

Common Theme: Evolution of Common Theme: Evolution of FormsForms

Evolution of the land: subtleties of change Evolution of the land: subtleties of change in the desert landscapein the desert landscape

Evolution of circumstellar material: from Evolution of circumstellar material: from crud to planetscrud to planets

Evolution of Galaxies: from empty Evolution of Galaxies: from empty darkness to physical formsdarkness to physical forms

Bothun-Strom ConnectionBothun-Strom Connection

One of his early papers stole my thesis One of his early papers stole my thesis titletitleEstablishing a connection was initially Establishing a connection was initially difficultdifficultFound common ground in 1982Found common ground in 1982Hermann and the Blue Toad Misery ClubHermann and the Blue Toad Misery ClubSt. Louis CardinalsSt. Louis CardinalsTeaching at Amherst and softball Teaching at Amherst and softball ringer(1983)ringer(1983)

We Start in 1976We Start in 1976

• Photographic detectors predominate Photographic detectors predominate issues of photometric calibration issues of photometric calibration are rampant; Galaxy morphology is are rampant; Galaxy morphology is different on non-linear compared to different on non-linear compared to linear detectorslinear detectors

• The Hubble Sequence: Physical, The Hubble Sequence: Physical, Transformative or TransientTransformative or Transient

• Density wave theory was popular Density wave theory was popular widely thought to adequately account widely thought to adequately account for observed morphologiesfor observed morphologies

Continuing The Universe Continuing The Universe in 1976in 1976

• The extensive nature of the dark matter The extensive nature of the dark matter component in galaxies was unknowncomponent in galaxies was unknown

• There were no known massive low There were no known massive low surface brightness galaxiessurface brightness galaxies

• The complex nature of the hierarchical The complex nature of the hierarchical clustering of galaxies was not even clustering of galaxies was not even imagined by anyone.imagined by anyone.

• Aperture photometry dominates our Aperture photometry dominates our measurements of galaxies (hard workmeasurements of galaxies (hard work).).

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)

The Strom’s LegacyThe 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

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.

This work was substantial and would This work was substantial and would allow for the structure of disk allow for the structure of disk galaxies to be looked at in a new waygalaxies to be looked at in a new way

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

strength/definition and prevalence 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

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 Today?But what do we know Today?

Why is the Baryonic mass fraction of galaxies Why is the Baryonic mass fraction of galaxies nearly constant? (Cortese etal 2008)nearly constant? (Cortese etal 2008)

Why don’t galaxies have hard edges if star Why don’t galaxies have hard edges if star formation is density driven? (XUV disks)formation is density driven? (XUV disks)

Why is the Galactic Halo still being formed from Why is the Galactic Halo still being formed from stars streaming in? (SDSS new LG members)stars streaming in? (SDSS new LG members)

What determines how many stars form in the What determines how many stars form in the first generation and how much material is left first generation and how much material is left over (similar to planetary disk phenomena)over (similar to planetary disk phenomena)

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

SummarySummary

So galaxy formation evolution, like So galaxy formation evolution, like planet formation, has gotten a lot more planet formation, has gotten a lot more complicated. New data simply reminds complicated. New data simply reminds us of all that we do not know.us of all that we do not know.

Strom’s legacy as an astronomer lies in Strom’s legacy as an astronomer lies in commitment to leverage all commitment to leverage all wavelengths to get a fully integrated wavelengths to get a fully integrated physical view of the system. This how physical view of the system. This how all of astronomy should be done.all of astronomy should be done.