drft

drft is a package to modify RAMSES (Teyssier 2002) initial conditions (ICs) made by MUSIC (Hahn & Abel 2011) to include the effects of relative baryon-dark matter velocities (Tseliakhovich & Hirata 2010) from recombination to the starting time of your simulation. It contains routines for solving the evolution equations (py_vbc), which is essentially a Python reproduction of vbc_transfer in CICsASS (O'Leary & McQuinn 2012). drft was itself based on routines in seren3 written by David Sullivan.

How to use

The basic steps for running drft are:

1. Compute transfer functions that have separate amplitudes for baryon and dark matter velocities (e.g. using CAMB, Lewis et al. 2000)

2. Use these transfer functions to generate cubic ICs using MUSIC (this can be enforced by setting force_equal_extent=yes in the MUSIC configuration file)

3. Calculate the v_bc field (this can be done using yt_ic_vbc.py, which uses yt, Turk et al. 2011)

4. Run bias_ics.py (see work_ics.sh.example for an example script)

Cosmological parameters for py_vbc can be set using a .ini file, see py_vbc/planck2018_params.ini for an example. If you do want to change parameters, you will need to:

1. Change config_fname in py_vbc/constants.py to the new configuration filename

2. Regenerate transfer functions at z=1003, 1000, 997 and 200 (for the setup described in the paper) and place them in py_vbc/tfs/

3. Regenerate a RECFAST (Seager et al. 1999) output and place it in py_vbc/recfast/

Acknowledging

If you use results produced by this package in a scientific publication, please cite the methodology paper Conaboy et al. (2023) ADS.

References

Conaboy, L., Iliev, I. T., Fialkov, A., Dixon, K. L., Sullivan, D., 2023, Monthly Notices of the Royal Astronomical Society, 525, 5479

Hahn O., Abel T., 2011, Monthly Notices of the Royal Astronomical Society, 415, 2101

Lewis A., Challinor A., Lasenby A., 2000, The Astrophysical Journal, 538, 473

O’Leary R. M., McQuinn M., 2012, The Astrophysical Journal, 760, 4

Seager S., Sasselov D. D., Scott D., 1999, The Astrophysical Journal Letters, 523, L1

Teyssier R., 2002, Astronomy and Astrophysics, 385, 337

Tseliakhovich D., Hirata C., 2010, Physical Review D, 82, 083520

Turk M. J., Smith B. D., Oishi J. S., Skory S., Skillman S. W., Abel T., Norman M. L., 2011, The Astrophysical Journal Supplement Series, 192, 9