Mocking Three-Dimensional Cube

This page introduces the usage of the cube3d module to simulate integral-field spectral cubes.

Overview

The module simulates a 3D datacube with dimensions (RA, DEC, Wavelength), combining both stellar continuum and ionized gas emission. The key class is:

from gehong import cube3d
u = cube3d.Cube3D(config, stellar_map=stellarcontinuum, gas_map=ionizedgas)

Where: - config is the global simulation configuration object. - stellar_map is a StellarPopulationMap instance. - gas_map is an IonizedGasMap instance.

StellarPopulationMap Inputs

The stellar population distribution is defined by map2d.StellarPopulationMap. Two working modes are supported:

(1) Surface brightness–calibrated mode (empirical):

stellar_map = map2d.StellarPopulationMap(
    config,
    sb=sb_map,
    sfh=sfh_map,          # optional
    ceh=ceh_map,          # optional
    vel=vel_map,
    vdisp=vdisp_map,
    ebv=ebv_map
)

  • sb: 2D surface brightness in mag/arcsec2

  • sfh: Scalar, 2D, or 3D star formation history

  • ceh: Scalar, 2D, or 3D chemical enrichment history

  • vel, vdisp, ebv: Kinematic and dust maps

(2) Physically calibrated mode (from SFH):

stellar_map = map2d.StellarPopulationMap(
    config,
    sfh=sfh_cube,
    sfh_age=sfh_age,
    ceh=ceh_cube,
    ceh_age=ceh_age,
    vdisp=vdisp_map,
    ebv=ebv_map,
    z=0.01,                 # scalar redshift
    vpec=vpec_map          # peculiar velocity map
)

  • sfh: 3D array [nx, ny, nage] of SFH

  • sfh_age: 1D age grid

  • z: Scalar redshift (required)

  • vpec: Peculiar velocity map (km/s)

IonizedGasMap Inputs

Ionized gas emission is defined by map2d.IonizedGasMap. Two modes are also supported:

(1) Halpha-calibrated mode:

gas_map = map2d.IonizedGasMap(
    config,
    halpha=halpha_map,
    zh=zh_map,
    vel=vel_map,
    vdisp=vdisp_map,
    ebv=ebv_map
)

  • halpha: 2D map of Hα flux (in 10-17 erg/s/cm2)

  • zh: Gas metallicity map

  • vel, vdisp, ebv: Kinematics and extinction

(2) Physically calibrated mode (from SFR):

gas_map = map2d.IonizedGasMap(
    config,
    sfr=sfr_map,
    zh=zh_map,
    z=0.01,               # scalar redshift
    vpec=vpec_map,
    vdisp=vdisp_map,
    ebv=ebv_map
)

  • sfr: 2D star formation rate map

  • z: Scalar redshift (required)

  • vpec: Peculiar velocity map

Template Configuration

To simulate spectra, first configure spectral templates:

from gehong import spec1d
stellar_tem = spec1d.StellarContinuumTemplate(config)
gas_tem = spec1d.EmissionLineTemplate(config, model='hii')

Generate the Cube

Use the make_cube method of Cube3D to generate the full spectrum:

u.make_cube(stellar_tem=stellar_tem, hii_tem=gas_tem)

This generates a cube with shape (nx, ny, nwave) and unit of 10-17 erg/s/cm2/Å.

Saving the Cube

You can export the cube to a FITS file with full WCS header:

u.savefits("mock_cube.fits")

The output will contain a primary HDU with metadata and a data HDU with the flux cube.

Inserting Single Spectra

To insert an individual spectrum into the cube center or with an offset:

u.insert_spec(spec, dx_arcsec=0.0, dy_arcsec=0.0)

This is useful for injecting AGN or other localized components.