Jan Rybitzki's Chempy projects

Just to commit to memory here is a discussion draft of Jan's papers
[from HWR - JR conversations; and DWH input]

Paper II or I :
  -- write-up of the basic model chempy (with thesis advisor Andreas Just).
  -- science bit: given a set of yields, how much can the abundances of
      a single star constrain the chempy parameters: the SFR, high-mass IMF slope,
      the SN-delay, the feed-back-mass-loading, the fraction of WD's that go SN Ia, and
     the gas inflow rate.
    [corollary: is having the age of a star helpful, if the star is not very old]
 -- implementation: take the Sun and Arcturus abundances and ages, and
    construct a chempy parameter pdf triangle plot.
-- consider taking the 'cosmic abundance' instead of Arcturus
-- consider different yield tables
-- discussion:
    explain why this fails..


Paper I or II:
   -- are the APOGEE data good enough to tell us which (published) yields tables are "best"
  -- Melissa will canonize the Hawkins et al accurate APOGEE abundances/ages to the
     RC sample of APOGEE; we then presume that abundance zero-point systematics
     are a sub-dominant error source
  -- Jan will try all 9 yield table (3x) combination to match the APOGEE RC sample
     (effectively marginalizing over the chempy params) and ask which fits best --> make Hogg happy
    [How much of this could be in paper I]
CHANGE of scope: use the ~30 abundance standards of Jofre et al 2016, to fix the field tables...
  that stays Paper III

Aside: can we ask what the set of [X/H] zero-point shifts in APOGEE can be, that would make
Arcturus, the Sun, and the cosmic standard likely??


Paper III:
   -- goal: the (varied?) chemical prehistories of all stars in the APOGEE sample
  -- use ensemble fit to tweak yield tables (see Paper II); we then assume both the
      yields and the abundance zero points to be "correct" (i.e. we won't marginalize)
  -- chempy has four parameters that may plausibly vary from star-to-star:
     the SFR, high-mass IMF slope (?), the feed-back-mass-loading, and
     the gas inflow rate.
  -- construct the pdf of these parameters for every single star in APOGEE;
     also exploit the ages for the stars we have..
  -- this enables:
      ** did the IMF vary as a function of time, of FeH?
      ** does the inferred mass-loading, or the inflow correlate with other properties
        (age, FeH, etc..)

CHANGE of scope: apply all of this to the ~30 abundance standards of Jofre et al 2016

Paper IV (Hogg)