Binaries/rotation/dredge-up ages of giants

Had a conversation with Selma de Mink:
her claim: on the MS, stars more massive than 2Mo rotate a lot
faster than power-mass stars (because of magnitude field stars).
The question is whether some of that rotation survives recognizeably
into the giant phase.

Does Apogee have a rotation parameter? If so, does that correlate with mass?

Exploring Apogee's abundances space with chemical evolution models

Starting point

Jan Rybizki arrived Feb 1, 2016 and brought with him his one-zone chemical evolution model. The overall plan is to explore what we can learn about a) the Milky Way (its chemical evolution and the yields of the stars), b) the Apogee abundances, and c) Jan's one-zone model and its limitations.
.. and then learn it. Here's a set of HWR notes after talking with Jan.

Jan overplayed his (fiducial) model predictions to the Apogee abundances as-is. It looks like in the plots below, basically a mismatch... which is an OK starting point.

Towards understanding the data-model (mis-)match

The reasons why data and model may disagree are manyfold ...disagreement is good, it teaches us something new. 

Model parameters

The most immediate advantage of Jan's models is that it can 'fit data' via MCMC,

which makes the variation of many, even all model parameters feasible. The model parameters fall into two categories:

Galaxy History: This entails the SFR, the inflow and outflow terms form the box, and the IMF; this is a 'handful of parameters'

Stellar physics: this entails essentially the yields; these are in some sense parameters, but presumably the space of all possible yields is not spanned by a set of continuous parameters. Hence, see below.

Data Calibration

It is well known that the Apogee ASCAP pipeline, at least for some elements has systematic offsets that are far in excess of the typical error bars. One simple way to explore the role of possible offsets is to make a basic abundance offset [X/Fe]_0 a fitting parameter, presumably with some prior on it (to avoid complete 'runaway').

Yields

It would be good to think about how one can turn the options on yields into something that is parameterizable, and therefore fit-able.

Applicability of a 1-zone Model

The model as is, makes a 'unique prediction' for [X/H] or [X/Fe] = f(age). Clearly, the data show a 'spread' in their abundance patterns, well beyond their errors. In a galaxy where radial migration must be prevalent, a 1-zone model cannot be correct.

In the longer run, we should explore in which regime it is a useful approximation: this could be done by restricting the observations to a limited range in [Fe/H], if [Fe/H] has been a good birth-radius predictor (for stars younger than 8Gyrs). Or we could fit a superposition of 1-zone models.

Next Steps

What portion of [X/H]-age space can be reached by varying the parameters of a one-zone model of a given yield-table?

How to go about it? Perhaps by simply defining the fill range of plausible model parameters, (galaxy evolution and IMF, not yields)  and then sampling model predictions uniformly.

It would be good to have an approach, to figure out how degenerate (or not), variations in the IMF and of the SFH are (if one has Apogee-type data).

What is the best one-zone fit to the Apogee data under the (untenable) assumption that all yields are right, and the data have no systematic offsets?

Apparently for historical reasons it is still not 'easy' in Jan's model to hold an arbitrary number of parameters (including none) fixed, fitting the rest via emcee. That piece of infrastructure should probably be put in place as one of the first steps.

What is the best one-zone fit to the Apogee data under the (untenable) assumption that all yields are right, and the data may have systematic offsets?

Apparently for historical reasons it is still not 'easy' in Jan's model to hold an arbitrary number of parameters (including none) fixed, fitting the rest via emcee. That piece of infrastructure should probably be put in place as one of the first steps.

Can we learn about the yields?

Conceptually the next step would be to have a few yield-knobs to tune, and let them loose in the data fitting.

Sample selection:

We need to decide what good sample cuts are, to make the one-zone model a sensible framework. Options are:

-- spatial cut (solar radius)

-- abundance cut (FeH==birth radius) at solar FeH +- 0.x dex

-- no cuts

Thoughts on BigData/InferenceSummerSchool/KTS

Two basic issues:
1)  where does the disconnect between the astronomers and the ML/CS folks actually occur?
2)  are the any women of any seniority on the astro/data-mining world

On 1)
HWR's suspicion is that astronomers almost always deal with data that are noisy,
 and heteroscedastic at that.
Therefore, astronomers know how to write down likelihood, go Bayes, but: and then??
CS/ML folks have amazing tools to classify, but these tools almost all fail ungracefully in the
"very noisy" regime. I.e. are not good at simply ignoring differences in object labels that can sensibly
attributed to only noise, not to any inherent difference of the objects.

What's a good definition of noisy here:
Let's presume any object has many data points (e.g. pixels in the spectrum of a star);
there is the regime where the data variance at any one pixel due to noise is comparable
to the (to be classified) ensemble variance (noiseless) in that 'pixel'. What are good ML tools
in that regime.

What to do about it
a) try to spell this out clearly, and ask Hogg, DFM, ZI, BernhardSchöllkopf etc. for insights?
b) initiate some culture-gap bridging exercise with the HITS group, to see how useful that is..


On 2)
The Tel Aviv Big Data conference (Dec. 15), the search for lecturers for an IMPRS summer school,
showed the paucity of "obvious" female scientists to serve as lecturers or tutors.
What to do?
-- find out whether this is just a consequence of HWR's ignorance? Ask Hogg, Schöllkopf, Ivezic, Bailer-Jones, DFM for names...
-- initiate discussion with Reutter to see whether there might be any interest in initiating
   an "award", amounting to a 3-year fellowship, for women in data science.
  To be taken as a post-doc, or a repeat summer fellowship.

Tel Aviv notes

Post Tel Aviv

-- M-stars WD's with Dani

-- Cannon residual into Nikos Gianniotis' machinery

-- write-up for Chao Liu's PD.

PS1 Cepheids revisited

After doing some more thinking, learning a lot from Laura already, here's my current thinking about Cepheids:

1) in the context of Galactic disk evolution, Cepheids could should play the role of the ideal 'present-day', young star diagnostic.
They can answer: where and with what (detailed!!) abundances are stars born now.
2) With them, we can do the dynamics of "the other side of the galaxy" .

By now, quite a number of things are in the AS4 white paper by Byrd

Nano-Jasmin: ESA to participate in Japan's mini-Hipparchos?

Japan's National Observatory is planning to launch a 35kg astrometric satellite, dubbed Nano-Jasmin, to do astrometry at the very bright end. The idea might be: if ESA provides the launch, the the "Gaia team" will get access to the data. Ask Coryn what he knows about this...

LSST in Germany

After conversation with Steve Kahn, Michael Strauss (& at end -- Joe Mohr)

Basic plan:

get a DPG (not the whole community) going, which involves the usual suspects
and enough university participation that a DFG Schwerpunkt, as suggested by Krückeberg,
seems feasible..

DFG Schwerpunkt, deadline Oct 15; decision by March; Rundgespräch recommended


HWR's action to coordinate within the MPG:

-draft e-mail with the basic options:
Who want's to commit how many "individual slots"
Should we cast this is terms of a joint MPG participation group?
Should we approach the MPG Präsidium for central funds?