Disk Model

class galpak.DiskModel(flux_profile='exponential', thickness_profile='gaussian', dispersion_profile='thick', rotation_curve='arctan', line=None, redshift=None)

The first and default galpak Model (when unspecified). It simulates a simple disk galaxy using DiskParameters.

flux_profile: ‘exponential’ | ‘gaussian’ | ‘de_vaucouleurs’ | ‘sersicN2’ | ‘user’
The flux profile of the observed galaxy. The default is ‘exponential’. See http://en.wikipedia.org/wiki/Sersic%27s_law If ‘user’ provided flux map, specify flux_image. Currently unsupported
thickness_profile: ‘gaussian’ [default] | ‘exponential’ | ‘sech2’ | ‘none’
The perpendicular flux profile of the disk galaxy. The default is ‘gaussian’. If none, the galaxy will be a cylinder
rotation_curve: ‘arctan’ | ‘mass’ | ‘exp’ | ‘tanh’ | ‘isothermal’
The profile of the velocity v(r) can be in
  • ‘arctan’ (default) : ~ Vmax arctan(r/rV), rV=turnover radius
  • ‘tanh’ : Vmax tanh(r/rV), rV=turnover radius
  • ‘exp’ : inverted exponential, 1-exp(-r/rV)
  • ‘mass’ : a constant light-to-mass ratio v(r)=sqrt(G m(<r) / r)
  • ‘isothermal’ : an isothermal rotation curve v(r)=Vmax * sqrt(1-rV/r * arctan(r/rV)
dispersion_profile: ‘thick’ [default] | ‘thin’

The local disk dispersion from the rotation curve and disk thickness from Binney & Tremaine 2008, see Genzel et al. 2008. GalPak has 3 components for the dispersion:

  • a component from the rotation curve arising from mixing velocities of a disk with non-zero thickness.
  • a component from the local disk dispersion specified by disk_dispersion
  • a spatially constant dispersion, which is the output parameter velocity_dispersion.
line: None[default] | dict to fit doublets, use a dictionary with
line[‘wave’]=[l, lref] eg. [3726.2, 3728.9] # Observed or Rest line[‘ratio’]=[0.8, 1.0] eg. [0.8, 1.0] # The primary line for redshifts is the reddest
redshift: float
The redshift of the observed galaxy, used in mass calculus. Will override the redshift provided at init ; this is a convenience parameter. If this is not set anywhere, GalPak will not try to compute the mass.