Setting Up the BEAST

Basics

  1. Define project and grid input parameters in beast_settings.txt. (This is the default file name used throughout the documentation and examples, but it can be named whatever you’d like.)

  2. Execute BEAST Run using python run_beast.py with appropriate task flags

    • Default Full Stack Run: python run_beast.py -p -o -t -f

BEAST Settings

Before running the BEAST, you will need to modify beast_settings.txt to specify the required parameters for generating models and fitting data. These parameters (and example values) are described below. An example beast_settings.txt can be found here.

Project Details

  • project: pathname of of working subdirectory.

  • surveyname: name of the survey.

  • filters: names of photometric filter passbands (matching library names).

  • basefilters: short versions of passband names.

  • obs_colnames: column names in obsfile for observed fluxes. The input data MUST be in fluxes, NOT in magnitudes and the fluxes MUST be in normalized Vega units.

  • obsfile: filename for input flux data.

Artificial Star Test (AST) File Parameters

The BEAST generates artificial star test (AST) input files based on additional input parameters from beast_settings.txt.

  • ast_models_selected_per_age: number of models to pick per age (default = 70).

  • ast_bands_above_maglimit: number of filters that must be above the magnitude limit for an AST to be included in the list (default = 3).

  • ast_realization_per_model: number of realizations of each included AST model to be put into the list (default = 20).

  • ast_maglimit: two options: (1) number of magnitudes fainter than the 90th percentile faintest star in the photometry catalog to be used for the mag cut (default = 1); (2) custom faint end limits (space-separated list of numbers, one for each band).

  • ast_with_positions: (optional; bool) if True, the AST list is produced with X,Y positions. If False, the AST list is produced with only magnitudes.

  • ast_density_table: (optional; string) name of density table, containing either the source density map or the background density map. If supplied, the ASTs will be repeated for each density bin in the table (default = None).

  • ast_N_bins: (optional; int) number of source or background bins that you want ASTs repeated over.

  • ast_pixel_distribution: (optional; float) minimum pixel separation between AST position and catalog star used to determine the AST spatial distribution. Used if ast_with_positions is True.

  • ast_reference_image: (optional; string) name of the reference image used by DOLPHOT when running the measured photometry. Required if ast_with_positions is True and no X,Y information is present in the photometry catalog.

  • ast_coord_boundary: (optional; list of two arrays) if supplied, these RA/Dec coordinates will be used to limit the region over which ASTs are generated (default = None).

  • ast_erode_selection_region: (optional; float) To avoid placing ASTs near the edge of the image, set this to the number of arcseconds (default=0.5, which is ~10 pixels for WFC3/UVIS) to shrink the allowed AST placement region. This is applied by doing an erosion to both ast_coord_boundary (if set) and a convex hull around the photometry catalog.

  • astfile: pathname to the AST files (single camera ASTs).

  • ast_colnames: names of columns for filters in the AST catalog (default is the basefilter list).

  • noisefile : pathname to the output noise model file.

  • absflux_a_matrix : absolute flux calibration covariance matrix for HST specfic filters.

Grid Definition Parameters

The BEAST generates a grid of stellar models based on aditional input parameters from beast_settings.txt. See <beast_grid_inputs.rst> for details on model libraries. For more on setting up priors, see BEAST priors.

  • n_subgrid: number of sub-grids to use (1 means no subgrids), useful for when the physics model grid is too large to read into memory.

  • velocity : heliocentric velocity of a galaxy (e.g., -300 km/s for M31).

  • distances: distance grid range parameters. [min, max, step], or [fixed number].

  • distance_unit: specify magnitude (units.mag) or a length unit.

  • distance_prior_model: specify a prior for distance parameter.

  • Stellar parameters

    • logt: age grid range parameters (min, max, step).

    • age_prior_model: specify a prior for age parameter.

    • mass_prior_model: specify a stellar IMF.

    • z: metallicity grid points.

    • met_prior_model: specify a prior for metallicity parameter.

    • oiso: isochrone model grid. Current choices: Padova or MIST. Default: PARSEC+CALIBRI: oiso = isochrone.PadovaWeb()

    • osl: stellar library definition. Options include Kurucz, Tlusty, BTSettl, Munari, Elodie and BaSel. You can also generate an object from the union of multiple individual libraries: osl = stellib.Tlusty() + stellib.Kurucz()

  • Dust parameters

    • extLaw: extinction law definition.

    • avs: dust column in magnitudes (A_V) grid range parameters (min, max, step).

    • av_prior_model: specify a prior for A_V parameter.

    • rvs: average dust grain size grid (R_V) range parameters (min, max, step).

    • rv_prior_model: specify a prior for R_V parameter.

    • fAs: mixture factor between “MW” and “SMCBar” extinction curves (f_A) grid range parameters (min, max, step).

    • avs: dust column in magnitudes (A_V) grid range parameters (min, max, step).

    • av_prior_model: specify a prior for A_V parameter.

    • rvs: average dust grain size grid (R_V) range parameters (min, max, step).

    • rv_prior_model: specify a prior for R_V parameter.

    • fAs: mixture factor between “MW” and “SMCBar” extinction curves (f_A) grid range parameters (min, max, step).

    • fA_prior_model: specify a prior for f_A parameter.

Optional Features

Add additional filters to grid

Define list of filternames as additional_filters and alter add_spectral_properties call:

add_spectral_properties_kwargs = dict(filternames=filters + additional_filters)

Allow non-interrupting warnings in verify_params

Set allow_verify_warnings boolean variable in beast_settings.txt to allow non-interrupting warnings. Default: raise UserWarning exception.

allow_verify_warnings = True

Remove constant SFH prior

Add prior_kwargs to beast_settings.txt:

prior_kwargs = dict(constantSFR=False)

Add kwargs defining code block before add_stellar_priors() call in run_beast.py:

if hasattr(settings, 'prior_kwargs'):
  prior_kwargs = settings.prior_kwargs
else:
  prior_kwargs = {}

Enable Exponential Av Prior

Set av_prior_model in beast_settings.txt:

av_prior_model = {'name': 'exponential', 'a': 2.0, 'N': 4.0}

BEAST Filters

The filters are defined in beast/libs/filters.hd5. The file contains two groups:

  • content: fields are TABLENAME (string), OBSERVATORY (string), INSTRUMENT (string), NORM (float), CWAVE (float), PWAVE (float), COMMENT (string)

  • filters has a group for each filter, with the same names as TABLENAME. The groups contain a dataset with the fields WAVELENGTH (float array, in Angstroms) and THROUGHPUT (float array).

The filters currently included in the BEAST filter library are as follows.

GROUND_JOHNSON_U

GROUND_JOHNSON_B

GROUND_JOHNSON_V

GROUND_COUSINS_R

GROUND_COUSINS_I

GROUND_BESSELL_J

GROUND_BESSELL_H

GROUND_BESSELL_K

HST_NIC2_F110W

HST_NIC2_F160W

HST_NIC2_F205W

HST_WFPC2_F218W

HST_ACS_HRC_F220W

HST_ACS_HRC_F250W

HST_WFPC2_F255W

HST_WFPC2_F300W

HST_ACS_HRC_F330W

HST_WFPC2_F336W

HST_ACS_HRC_F344N

HST_ACS_HRC_F435W

HST_ACS_WFC_F435W

HST_WFPC2_F439W

HST_WFPC2_F450W

HST_ACS_HRC_F475W

HST_ACS_WFC_F475W

HST_ACS_HRC_F502N

HST_ACS_WFC_F502N

HST_ACS_HRC_F550M

HST_ACS_WFC_F550M

HST_ACS_HRC_F555W

HST_ACS_WFC_F555W

HST_WFPC2_F555W

HST_ACS_HRC_F606W

HST_ACS_WFC_F606W

HST_WFPC2_F606W

HST_WFPC2_F622W

HST_ACS_HRC_F625W

HST_ACS_WFC_F625W

HST_ACS_HRC_F658N

HST_ACS_WFC_F658N

HST_ACS_HRC_F660N

HST_ACS_WFC_F660N

HST_WFPC2_F675W

HST_ACS_HRC_F775W

HST_ACS_WFC_F775W

HST_WFPC2_F791W

HST_ACS_HRC_F814W

HST_ACS_WFC_F814W

HST_WFPC2_F814W

HST_ACS_HRC_F850LP

HST_ACS_WFC_F850LP

HST_WFPC2_F850LP

HST_ACS_HRC_F892N

HST_ACS_WFC_F892N

CFHT_CFH12K_CFH7406

CFHT_CFH12K_CFH7504

CFHT_MEGAPRIME_CFH7605

CFHT_MEGAPRIME_CFH7701

CFHT_MEGAPRIME_CFH7803

CFHT_WIRCAM_CFH8002

CFHT_WIRCAM_CFH8101

CFHT_WIRCAM_CFH8102

CFHT_WIRCAM_CFH8103

CFHT_WIRCAM_CFH8104

CFHT_WIRCAM_CFH8201

CFHT_WIRCAM_CFH8202

CFHT_WIRCAM_CFH8203

CFHT_WIRCAM_CFH8204

CFHT_WIRCAM_CFH8301

CFHT_WIRCAM_CFH8302

CFHT_WIRCAM_CFH8303

CFHT_WIRCAM_CFH8304

CFHT_WIRCAM_CFH8305

CFHT_MEGAPRIME_CFH9301

CFHT_MEGAPRIME_CFH9401

CFHT_MEGAPRIME_CFH9601

CFHT_MEGAPRIME_CFH9701

CFHT_MEGAPRIME_CFH9801

HST_WFC3_F098M

HST_WFC3_F105W

HST_WFC3_F110W

HST_WFC3_F125W

HST_WFC3_F126N

HST_WFC3_F127M

HST_WFC3_F128N

HST_WFC3_F130N

HST_WFC3_F132N

HST_WFC3_F139M

HST_WFC3_F140W

HST_WFC3_F153M

HST_WFC3_F160W

HST_WFC3_F164N

HST_WFC3_F167N

HST_WFC3_F200LP

HST_WFC3_F218W

HST_WFC3_F225W

HST_WFC3_F275W

HST_WFC3_F280N

HST_WFC3_F300X

HST_WFC3_F336W

HST_WFC3_F343N

HST_WFC3_F350LP

HST_WFC3_F373N

HST_WFC3_F390M

HST_WFC3_F390W

HST_WFC3_F395N

HST_WFC3_F410M

HST_WFC3_F438W

HST_WFC3_F467M

HST_WFC3_F469N

HST_WFC3_F475W

HST_WFC3_F475X

HST_WFC3_F487N

HST_WFC3_F502N

HST_WFC3_F547M

HST_WFC3_F555W

HST_WFC3_F600LP

HST_WFC3_F606W

HST_WFC3_F621M

HST_WFC3_F625W

HST_WFC3_F631N

HST_WFC3_F645N

HST_WFC3_F656N

HST_WFC3_F657N

HST_WFC3_F658N

HST_WFC3_F665N

HST_WFC3_F673N

HST_WFC3_F680N

HST_WFC3_F689M

HST_WFC3_F763M

HST_WFC3_F775W

HST_WFC3_F814W

HST_WFC3_F845M

HST_WFC3_F850LP

HST_WFC3_F953N

HST_WFC3_FQ232N

HST_WFC3_FQ243N

HST_WFC3_FQ378N

HST_WFC3_FQ387N

HST_WFC3_FQ422M

HST_WFC3_FQ436N

HST_WFC3_FQ437N

HST_WFC3_FQ492N

HST_WFC3_FQ508N

HST_WFC3_FQ575N

HST_WFC3_FQ619N

HST_WFC3_FQ634N

HST_WFC3_FQ672N

HST_WFC3_FQ674N

HST_WFC3_FQ727N

HST_WFC3_FQ750N

HST_WFC3_FQ889N

HST_WFC3_FQ906N

HST_WFC3_FQ924N

HST_WFC3_FQ937N

HST_NIC3_F108N

HST_NIC3_F110W

HST_NIC3_F113N

HST_NIC3_F150W

HST_NIC3_F160W

HST_NIC3_F164N

HST_NIC3_F166N

HST_NIC3_F175W

HST_NIC3_F187N

HST_NIC3_F190N

HST_NIC3_F196N

HST_NIC3_F200N

HST_NIC3_F205M

HST_NIC3_F212N

HST_NIC3_F215N

HST_NIC3_F222M

HST_NIC3_F240M

CFHT_MEGAPRIME_CFH9702

HST_WFPC2_F170W

GALEX_FUV

GALEX_NUV

GROUND_2MASS_J

GROUND_2MASS_H

GROUND_2MASS_Ks

SPITZER_IRAC_36

SPITZER_IRAC_45

SPITZER_IRAC_58

SPITZER_IRAC_80

WISE_RSR_W1

WISE_RSR_W2

WISE_RSR_W3

WISE_RSR_W4

GROUND_SDSS_U

GROUND_SDSS_G

GROUND_SDSS_R

GROUND_SDSS_I

GROUND_SDSS_Z