SF_ECOGAL

A star formation and feedback module designed for high-resolution simulations with a resolved ISM. Typically used in conjunction with the chemistry module SGCHEM and the supernova-feedback module SNE.

TODO: add a short description of the probabilistic SF approach.

Usage

The SF_ECOGAL master switch enables the module.

Additional Parameters

Star Formation

  • SF_Mechanism Star formation prescription used. This parameter sets the criteria based on which a gas cell is marked as possibly or certainly star-forming. Currently, four modes are available and are labeled by the values 1-4:

    1. Density threshold only: In this mode, if a gas cell exceeds the density given by SFDensityThreshold, it always forms a star

    2. Density threshold + probabilistic: Same as (1), but instead marks the cell as possibly-star-forming. The probabilistic approach is then used to determine whether it forms a star in the current timestep.

    3. Jeans Mass + probabilistic: A cell is marked as possibly star-forming if its mass exceeds 1/8th of its local Jeans mass \(M_J\). If its mass is larger than \(M_J\), a star is immediately formed.

    4. Jeans Mass + density threshold + velocity dispersion + probabilistic: Same as (3) but two additional criteria need to be met by the cell: its density must exceed SFDensityThreshold, and its gas must be converging (\(\nabla\cdot v < 0\)).

    Note that models 3 & 4 also support additional features:

    • The 1/8 fraction of the Jeans mass can be customized at configuration time through JEANS_REFINEMENT (see below).

    • Both can add the additional requirement that a cell must be a local potential peak to be labeled as star-forming. This is enabled with SF_ECOGAL_POTENTIALPEAK.

    • In both models, star formation can be enforced if a given gas number density SFDensityThreshold is exceeded. This is enabled with SF_ECOGAL_FORCE_SF_IN_DENS_GAS. Note that this requires the use of the SGChem chemistry module.

    To summarize, in the full SF model (model 4 + above additional constraints), a gas cell is possibly star-forming if it respects all of the following criteria:

    1. It is a local minimum of the gravitational potential

    2. \(\nabla\cdot v < 0\)

    3. \(\rho \geq \rho_\mathrm{thresh}\)

    4. \(M_\mathrm{cell} > M_J/N_\mathrm{J,SF}\)

    If, in addition, it also satisfies one of the two following criteria, it certainly forms a star:

    1. \(M_\mathrm{cell} > M_J\)

    2. \(n > n_\mathrm{thresh}\) (only if SF_ECOGAL_FORCE_SF_IN_DENS_GAS is set)

  • SFDensityThreshold Density threshold for star formation, used by models 1,2 and 4. Note that this corresponds to a physical (i.e. proper) gas mass density in internal mass density units.

  • SFEfficiency Star-formation efficiency \(\varepsilon\). The star-formation rate (SFR) of a (possibly) star-forming gas cell is defined as

    \(\mathrm{SFR} = \varepsilon\frac{M_\mathrm{cell}}{t_\mathrm{ff}}\)

  • StellarTargetMass Target mass of star particles, used when SF_ECOGAL_STELLAR_TARGET_MASS is set.

  • ForceSFThreshold Gas number density threshold for star formation, used when SF_ECOGAL_FORCE_SF_IN_DENS_GAS is set. Note that this corresponds to a physical (i.e. proper) gas number density in internal units.

Stellar Feedback setup

  • SNStellarLifetime TODO

  • LifetimeShorteningFactor TODO

  • TimeForLifetimeIncrease TODO

Additional Config.sh Options

SF_ECOGAL

Master switch to enable the module.

SF_ECOGAL_CHECKS

TODO

SF_ECOGAL_POTENTIALPEAK

Adds an additional SF criterion, namely that the gas cell must be a local potential peak, to SF mechanisms 3 and 4.

SF_ECOGAL_FORCE_SF_IN_DENS_GAS

Adds an additional SF criterion, namely that the gas cell must exceed a provided number density threshold. Used for SF mechanisms 3 and 4.

SF_ECOGAL_STELLAR_TARGET_MASS

Enforces a user-provided target mass for created star particles.

JEANS_REFINEMENT

Enforce a custom value for the \(N_\mathrm{J,SF}\) parameter appearing in SF models 3 & 4. A cell is then flagged as possibly star-forming if its mass exceeds 1/JEANS_REFINEMENT of its local Jeans mass. When this flag is not set, \(N_\mathrm{J,SF}=8\) is used by default.

SF_ECOGAL_FEEDBACK

Master switch to enable stellar feedback.

SF_ECOGAL_FEEDBACK_REINJECT_MASS

TODO

SF_ECOGAL_FEEDBACK_PHOTOION

TODO

SF_ECOGAL_FEEDBACK_PHOTOION_STROMGRENAPPROX

TODO

SF_ECOGAL_FEEDBACK_PHOTOION_DEBUG

TODO

Authors

Acknowledgements

The authors thank …

Usage Policy and Citation

TODO

Papers to cite:

  • TODO