Website of Tobias Westmeier

H i mass calculator

The calculator on this page allows you to calculate the H i mass of a gas cloud by specifying either the total H i column density, the total brightness temperature, or the total flux density of the cloud, obtained by summing over all pixels of the map and all spectral channels. Of course I cannot guarantee for the correctness of the results.

Warning: The calculator makes use of JavaScript which must be enabled in your webbrowser. Due to the limited range of floating-point numbers, the results may be wrong if any of the parameters, including the calculated mass itself, exceeds a value of about 3.4 × 10³⁸ (on a 32-bit system).

Parameter	Input	Unit	Remarks
H i column density		cm⁻²	Sum over all pixels and channels.
or
Brightness temperature		K	Sum over all pixels and channels.
Spectral channel width		km s⁻¹
or
Flux density		Jy	Sum over all pixels and channels.
Spectral channel width		km s⁻¹
HPBW of the telescope		arcsec
Required in all 3 cases:
Angular size of a pixel		arcsec
Distance of the object		kpc	Leave blank if unknown.