Thindisk

thindisk is a simple Python program to compute the line emission from a geometrically thin protoplanetary disk. It creates a datacube in FITS format that can be processed in a data reduction package (such as GILDAS) to produce synthetic images and visibilities. These synthetic data can be compared with observations to determine the properties (e.g. central mass or inclination) of an observed disk.

The disk is assumed to be in Keplerian rotation at a radius lower than the centrifugal radius (which can be set to a large value, for a purely Keplerian disk), and in infall with rotation beyond the centrifugal radius.

Input file

Model parameters are read from an input file. Here is an example:

[disk]
mstar = 0.20
incl = 85.
pa = 3.
r0 = 80
dist = 140
[cube]
npix = 1024
pixsize = 0.005
nchan = 128
chanwidth = 0.1
[line]
frequency = 219560.3541
intensity = gaussian, 135., 1.56
width = 0.1
vlsr = 6.0
[output]
name = l1527-c18o

Parameters

• mstar: mass of the central object in solar masses
• incl: disk inclination in degrees (90 for edge-on, 0 for face-on). Default: 45.
• pa: position angle of projected disk rotation axis, in degrees (0 for a North-South, 90 for East-West). Default: 0.
• rc: centrifugal radius, in AU. Default: 1e4
• size: disk size, in AU. Default: infinite disk.
• dist: disk distance, in pc
• npix: number of pixels in RA and Dec offset. Default: 512.
• pixsize: size of a pixel, in arcsecs, Default: 0.1.
• nchan: number of velocity channels: Default: 128.
• chanwidth: channel width, in km/s. Default: 0.1.
• frequency: line frequency, in MHz
• intensity: line intensity of the disk surface. For a Gaussian distribution, set to gaussian,int0,fwhm where int0 is the peak intensity, and fwmh is the FWHM (in arcsecs). For a power-law, set to powerlaw,int_r1,r1,int_expn where int_r1 is the intensity at the radius r1 (in arcsecs), and int_expn is the powerlaw exponent. For a ring, set to ring,int_ring,r1,r2, where int_ring is the intensity between radii r1 and r2 (in arcsecs). For a tapered power-law (Andrew et al., Apj 700, 1502, 2009, Eq. 4), set to tapered_powerlaw,int_r1,r1,int_expn, where int_r1 is a normalization factor, r1 is a characteristic radius (in arcsecs) and int_expn is the power-law exponent.
• width: line width, in km/s. To set the linewidth to a fraction of the Keplerian velocity, use e.g. 0.1*vkep. Default: 0.1
• vlsr: source systemic velocity in the LSR, in km/s, Default: 0.
• name: base name of the output FITS file, Default: output.fits.

Usage

% python thindisk.py input.ini`

where input.ini is the name of the output file.

Citation

If you use this code in a scientific publication, please cite it using this DOI: