This utility page is for scaling and generating abundance files for MAPPINGS V,
but is also useful for manipulating and scaling elemental abundances in general.
The scaling can be simple uniform scaling, or a more sophisicated differential scaling based on a given element (usually Oxygen or Iron)
allowing other elements to scale differently, using what here is called ζ scaling.
A set of files and ruby generating scripts is available that allows the generation of many
abundance files offline: (gcgeneratingscritps1015.zip 3.5MB). It includes pre-generated files
for the local galactic abundances (GC) and the Asplund et al 2009 solar photosphere abundances, on linear and logarithmicly space abundances.
This work is based on Nicholls et al 2017, MNRAS. DOI:10.1093/mnras/stw3235
A preprint is available: 1612.03546.pdf (2.8MB).
Concordance Zeta Abundance Scaling
MW Galactic Enrichment Factor, ζ (zeta)
Lower Break: Χ_0 =
-0.5
dex
Upper Break: Χ_1 = 0.25
dex
- Scaling is from ζ = 0.0 : primordial, to ζ = 1.0 : GC preset values, ζ may be > 1.0 for metal rich cases.
- New log(X) = Base log(X) + Δ(X,ζ) + log(ζ) . Δ(X,ζ) is computed from the ζ scale in use, with the break values, and the base ratio, Ξ, for each element.
- Nitrogen is scaled similarly, but with a special Δ(N,ζ_O) function using the ζ_O scale.
- Scaling is applied linearly to helium from a primordial base value of 0.0835, (-1.0783dex) using the oxygen ζ_O scale until a better ζ_He scale becomes available.
- Scaling is applied to all elements, carbon (Z=6) and above.
- Li, Be, B are left constant, edit manually if required.
Use log(ζ)
Only fill 'missing' (log(X) < -15.0) values
ζ =
ζ > 0.0, (ζ 1.0 = change)
This work is based on Nicholls et al 2017, MNRAS, 466, 3, 4403.
DOI:10.1093/mnras/stw3235
A preprint is available here: NSDKG_sub_v2.pdf (2.8MB).
Please note this is as submitted, and may change in detail in the future.
Abundance Scaling in Stars, Nebulae and Galaxies
David C. Nicholls,⋆ Ralph S. Sutherland, Michael A. Dopita, Lisa J. Kewley, & Brent A. Groves
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, Australia
ABSTRACT
We present a new basis for scaling abundances with total metallicity in nebular photoionisation models,
based on extensive stellar abundance data, to replace the uniform scaling normally used in the
analysis of HII regions. Our goal is to provide a single scaling method and abundance reference
standard that can be used in nebular modelling and its key inputs, the stellar atmosphere and e
volutionary track models.
We introduce a parametric enrichment factor, ζ, to describe the metallicity,
which allow for a simple conversion between scales based on different reference elements
(usually oxygen or iron), and which can be used for any standard metallicity reference set.
The models and parametric description provide a more physically realistic approach than simple
uniform abundance scaling. With appropriate parameters, the methods described here may be
applied to HII regions in the Milky Way, large and dwarf galaxies in the local universe,
Active Galactic Nuclei (AGNs), and to star forming regions at high redshift.