### **TIGRESS** is a numerical framework to simulate the **T**hree-phase **I**SM in **G**alaxies **R**esolving **E**volution with **S**tar formation and **S**upernova feedback.
[The TIGRESS code](https://github.com/PrincetonUniversity/Athena-TIGRESS/) is built on the [Athena MHD code](https://github.com/PrincetonUniversity/Athena-Cversion) package with additional physical modules including
* sink/star particles (see [Gong & Ostriker 2013](http://adsabs.harvard.edu/abs/2013ApJS..204....8G)) `--enable-starparticle --enable-starparstrict`
* SN rates and FUV luminosity as a function of cluster age and mass, based on [STARBURST99](http://adsabs.harvard.edu/abs/1999ApJS..123....3L)
* runaway OB stars from binaries
* 2/3 of SNe occur in binary OB stars
* secondary OB stars are ejected with the exponential velocity distribution for 20km/s < v < 200km/s with a characteristic velocity of v0=50km/s (motivated by Figure 2 in [Eldridge+ 2011](http://adsabs.harvard.edu/abs/2011MNRAS.414.3501E))
* supernova feedback (see also [Kim & Ostriker 2015](http://adsabs.harvard.edu/abs/2015ApJ...802...99K))
* optically thin cooling (tabulated) (see [Koyama & Inutsuka 2002](http://adsabs.harvard.edu/abs/2002ApJ...564L..97K) and [Sutherland & Dopita 1993](http://adsabs.harvard.edu/abs/1993ApJS...88..253S)) `--enable-cooling`
* time-dependent photoelectric heating due to FUV radiation from young stars
After extensive tests to determine the best working configuration with the ideal MHD solver `--with-gas=mhd`, TIGRESS adopts:
* the [van Leer integrator](http://adsabs.harvard.edu/abs/2009NewA...14..139S) `--with-integrator=vl`
* 2nd order (piecewise linear) interpolation `--with-order=2p`
* Roe's Riemann solver and [H-correction](http://adsabs.harvard.edu/abs/1998JCoPh.145..511S) `--with-flux=roe --enable-h-correction`
* first-order flux correction (see Appendix in [Lemaster & Stone 2009](http://adsabs.harvard.edu/abs/2009ApJ...691.1092L)) `--enable-fofc`
TIGRESS utilizes Athena's additional features including
* [Shearing Box](http://adsabs.harvard.edu/abs/2010ApJS..189..142S) `--enable-shearing-box`
* FARGO is _not_ used
* self-gravity solver using the FFT method (adopt Nicole Lemaster's implementation of [Plimpton's parallel FFT](http://www.sandia.gov/~sjplimp/docs/fft/README.html)) `--with-gravity=fft_disk --enable-fft`
* [shearing-periodic BCs in the horizontal directions](http://adsabs.harvard.edu/abs/2001ApJ...553..174G)
* [vacuum BCs in the vertical direction](http://adsabs.harvard.edu/abs/2009ApJ...693.1316K)
See the [TIGRESS method paper](http://adsabs.harvard.edu/abs/2017ApJ...846..133K) (Kim & Ostriker 2017) for details.
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© 2017 [Chang-Goo Kim](http://changgoo.github.io/index.html) and [Eve C. Ostriker](https://web.astro.princeton.edu/people/eve-ostriker)
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© 2017 [Chang-Goo Kim](http://changgoo.github.io/index.html) and [Eve C. Ostriker](https://web.astro.princeton.edu/people/eve-ostriker)
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