Welcome to the HI Fidelity (HiFi) cosmology calculator. Please use the tab links above to access the provided calculators:

z, Width and Flux: calculation of source redshift, the conversion of profile width measurements between different units and reference frames, and the conversion of profile flux units.

Angles & Beam: calculation of telescope solid angle from FWHM beam parameters, and the conversion between observed frame angles and solid angles to rest frame physical scales.

Flux/Mass: conversion between observed flux and HI mass.

Flux/nHI: conversion between observed flux and HI column density.

Fluxd/Tb: conversion between observed flux density and brightness temperature.

Noise: flux and flux density uncertainty estimation from telescope array properties.

SNR: signal-to-noise estimation from source and observation characteristics.

These calculators were written by Martin Meyer building on the celestial cosmology functions and Shiny interface of CosmoCalc written by Aaron Robotham and Joseph Dunne. A description of the formulae used can be found in the reference document Meyer et. al., 2017, submitted.

Redshift

Enter the redshift for the flux and profile width conversions:

Calculate

Or calculate the redshift from the observed frame central frequency or observed frame central velocity (cz) of the profile:

Profile width conversion

Convert profile width measurements between frequency and velocity, and between observed and rest frames for a source at redshift z

Flux conversion

Convert between different flux units for a source at redshift z

Redshift & Cosmology

Enter the cosmological parameters for conversion between angular and physical scales:

Angle
Physical Size*

Solid Angle
Physical Area*

Gaussian Beam Solid Angle from FWHM

*small angle approximation

Flux
Mass

Enter the source details you which to convert:

Cosmology

Set cosmological parameters for the HI mass-flux conversion:

customise

Plot:

Change the parameters below to modify the redshift dependence plot of conversions from the given fixed value:

Enter frequency interval and integration time for which to calculate output flux and flux density RMS

Enter known flux or flux density RMS and corresponding frequency interval and integration time

Enter array properties below. The dish System Equivalent Flux Density (SEFD) can be either directly entered or calculated using the additional panels.

Results

*These estimates are for a naturally-weighted, Stokes-I, non-primary beam corrected interferometric image without regard to baseline distribution, weighting or tapering. These factors (and others) can reduce the obtained sensitivity of an observation.

SEFD from Ae/Tsys

Ae/Tsys

Signal-to-Noise

SOURCE

Enter the fixed rest frame properties of your source

over area

OBSERVATION

Enter the properties of your observation

Cosmology

Set cosmological parameters:

customise

Plot

Change the parameters below to modify the redshift dependence plot of conversions from the given fixed value: