Setting Up the BEAST¶
Basics¶
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.)Execute BEAST Run using
python run_beast.py
with appropriate task flagsDefault 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 inobsfile
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_reference_image_hdu_extension
: (optional; int) extension number of the reference image file where the WCS information is stored. 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. For PARSEC, 1e-4<=z<=0.02; For MIST, -4.0<=[Z/H]<=0.5met_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
has been updated in March, 2022 using stsynphot to have correct,
total throughput for HST filters and to remove unused filters.
The file contains two groups:
content
: fields areTABLENAME
(string),OBSERVATORY
(string),INSTRUMENT
(string),NORM
(float),CWAVE
(float),PWAVE
(float),COMMENT
(string)filters
has a group for each filter, with the same names asTABLENAME
. The groups contain a dataset with the fieldsWAVELENGTH
(float array, in Angstroms) andTHROUGHPUT
(float array).
The filters currently included in the BEAST filter library are as follows.
Please do not forget updating beast/libs/vega.hd5
as well when making
any updates in beast/libs/filters.hd5
. Vega fluxes and magnitudes in
udpated filters need to be correspondingly recomputed and saved in vega.hd5.
HST_WFC3_F218W |
HST_WFC3_F225W |
HST_WFC3_F275W |
HST_WFC3_F336W |
HST_WFC3_F390M |
HST_WFC3_F390W |
HST_WFC3_F410M |
HST_WFC3_F438W |
HST_WFC3_F467M |
HST_WFC3_F475W |
HST_WFC3_F547M |
HST_WFC3_F555W |
HST_WFC3_F606W |
HST_WFC3_F621M |
HST_WFC3_F625W |
HST_WFC3_F689M |
HST_WFC3_F763M |
HST_WFC3_F775W |
HST_WFC3_F814W |
HST_WFC3_F845M |
HST_WFC3_F098M |
HST_WFC3_F105W |
HST_WFC3_F110W |
HST_WFC3_F125W |
HST_WFC3_F127M |
HST_WFC3_F139M |
HST_WFC3_F140W |
HST_WFC3_F153M |
HST_WFC3_F160W |
HST_WFPC2_F122M |
HST_WFPC2_F157W |
HST_WFPC2_F336W |
HST_WFPC2_F410M |
HST_WFPC2_F467M |
HST_WFPC2_F547M |
HST_WFPC2_F439W |
HST_WFPC2_F569W |
HST_WFPC2_F675W |
HST_WFPC2_F791W |
HST_WFPC2_F170W |
HST_WFPC2_F185W |
HST_WFPC2_F218W |
HST_WFPC2_F255W |
HST_WFPC2_F300W |
HST_WFPC2_F380W |
HST_WFPC2_F555W |
HST_WFPC2_F622W |
HST_WFPC2_F450W |
HST_WFPC2_F606W |
HST_WFPC2_F702W |
HST_WFPC2_F814W |
HST_ACS_WFC_F435W |
HST_ACS_WFC_F475W |
HST_ACS_WFC_F550M |
HST_ACS_WFC_F555W |
HST_ACS_WFC_F606W |
HST_ACS_WFC_F625W |
HST_ACS_WFC_F775W |
HST_ACS_WFC_F814W |
GALEX_FUV |
GALEX_NUV |