make_ppv¶

turbustat.simulator.make_ppv(vel_field, dens_field, los_axis=0, m=<Quantity 2.34167066e-27 kg>, T=<Quantity 100. K>, los_length=<Quantity 1. pc>, vel_disp=None, chan_width=None, v_min=None, v_max=None, threads=1, max_chan=1000, vel_struct_index=0.5, verbose=False, return_hdu=True, pixel_ang_scale=<Quantity 1. arcmin>, restfreq=<Quantity 1.42 GHz>)[source] [edit on github]¶

Generate a mock, optically-thin HI PPV cube from a given velocity and density field. Currently, the conversion to K assumes the 21-cm column density conversion.

Parameters:

Parameters:	vel_field : `Quantity` Three-dimensional isotropic, velocity field. Must have units of velocity. dens_field : `Quantity` Three-dimensional isotropic, velocity field. Must have units of number density. los_axis : int, optional The axis used to produce the PPV cube. m : `Quantity`, optional Average particle mass. Defaults to 1.4 time the proton mass, appropriate for the neutral ISM at solar metallicity. Used to calculate the thermal line width. T : `Quantity`, optional Temperature of the gas. Defaults to 100 K. Used to calculate the thermal line width. los_length : `Quantity`, optional Set the total physical length of the density and velocity fields along the line-of-sight. Defaults to 1 pc. vel_disp : `Quantity`, optional Velocity dispersion of the 3D velocity field. When none is given, the mean of the projected standard deviation of the velocity field along `los_axis` is used. Used to set the extent of the velocity channels and estimate the channel widths, when not given. chan_width : `Quantity`, optional Width of a velocity channel. When the width is not given, an estimate is made based on Eq. 12 from Esquivel+2003. v_min : `Quantity`, optional Minimum velocity channel. Set to `vel_field - 4 * v_lim`, where `v_lim = sqrt(vel_disp2 + v_therm2)`, when a limit is not given. v_max : `Quantity`, optional Maximum velocity channel. Set to `vel_field + 4 * v_lim`, where `v_lim = sqrt(vel_disp2 + v_therm2)`, when a limit is not given. threads : int, optional Number of cores to run on. Defaults to 1. max_chan : int, optional Sets an upper limit on the number of velocity channels (default of 1000) to avoid using excessive amounts of memory. If the number of channels exceeds this limit, a `ValueError` is raised. vel_struct_index : float, optional Index of the velocity field. Used when automatically determining the channel width. Defaults to 0.5. verbose : bool, optional Print out the min and max velocity extents and the channel width prior to computing the cube. return_hdu : bool, optional Return the cube as a FITS HDU. Enabled by default. pixel_ang_scale : `Quantity`, optional Specify the angular scale of one spatial pixel to set values in the FITS header. Defaults to 1 arcmin. restfreq : `Quantity`, optional Rest frequency of the spectral line passed to the FITS header. Defaults to 1.42 GHz, roughly the 21-cm HI rest frequency.
Returns:	cube : `Quantity` or `PrimaryHDU` The PPV cube as an array (`return_hdu=False`) or a FITS HDU (`return_hdu=True`). vel_axis : `Quantity` When `return_hdu=False` is returned, the values for the velocity axis are returned.

vel_field : Quantity: Three-dimensional isotropic, velocity field. Must have units of velocity.
dens_field : Quantity: Three-dimensional isotropic, velocity field. Must have units of number density.
los_axis : int, optional: The axis used to produce the PPV cube.
m : Quantity, optional: Average particle mass. Defaults to 1.4 time the proton mass, appropriate for the neutral ISM at solar metallicity. Used to calculate the thermal line width.
T : Quantity, optional: Temperature of the gas. Defaults to 100 K. Used to calculate the thermal line width.
los_length : Quantity, optional: Set the total physical length of the density and velocity fields along the line-of-sight. Defaults to 1 pc.
vel_disp : Quantity, optional: Velocity dispersion of the 3D velocity field. When none is given, the mean of the projected standard deviation of the velocity field along los_axis is used. Used to set the extent of the velocity channels and estimate the channel widths, when not given.
chan_width : Quantity, optional: Width of a velocity channel. When the width is not given, an estimate is made based on Eq. 12 from Esquivel+2003.
v_min : Quantity, optional: Minimum velocity channel. Set to vel_field - 4 * v_lim, where v_lim = sqrt(vel_disp**2 + v_therm**2), when a limit is not given.
v_max : Quantity, optional: Maximum velocity channel. Set to vel_field + 4 * v_lim, where v_lim = sqrt(vel_disp**2 + v_therm**2), when a limit is not given.
threads : int, optional: Number of cores to run on. Defaults to 1.
max_chan : int, optional: Sets an upper limit on the number of velocity channels (default of 1000) to avoid using excessive amounts of memory. If the number of channels exceeds this limit, a ValueError is raised.
vel_struct_index : float, optional: Index of the velocity field. Used when automatically determining the channel width. Defaults to 0.5.
verbose : bool, optional: Print out the min and max velocity extents and the channel width prior to computing the cube.
return_hdu : bool, optional: Return the cube as a FITS HDU. Enabled by default.
pixel_ang_scale : Quantity, optional: Specify the angular scale of one spatial pixel to set values in the FITS header. Defaults to 1 arcmin.
restfreq : Quantity, optional: Rest frequency of the spectral line passed to the FITS header. Defaults to 1.42 GHz, roughly the 21-cm HI rest frequency.

Returns:

cube : Quantity or PrimaryHDU: The PPV cube as an array (return_hdu=False) or a FITS HDU (return_hdu=True).
vel_axis : Quantity: When return_hdu=False is returned, the values for the velocity axis are returned.