astrocalc.distances.converter module

Convert distances between measurement scales

Author : David Young

class astrocalc.distances.converter.converter(log, settings=False)[source][source]

Bases: object

A converter to switch distance between various units of measurement

Key Arguments

  • log – logger

  • settings – the settings dictionary

Usage

To instantiate a converter object:

`python from astrocalc.distances import converter c = converter(log=log) `

distance_to_redshift(mpc)[source][source]

Convert a distance from MPC to redshift

The code works by iteratively converting a redshift to a distance, correcting itself and honing in on the true answer (within a certain precision)

Key Arguments

  • mpc – distance in MPC (assumes a luminousity distance).

Return

  • redshift

Todo

  • replace convert_mpc_to_redshift in all code

Usage

```python from astrocalc.distances import converter c = converter(log=log) z = c.distance_to_redshift(

mpc=500

)

print(z)

# OUTPUT: 0.108 ```

redshift_to_distance(z, WM=0.3, WV=0.7, H0=70.0)[source][source]

convert redshift to various distance measurements

Key Arguments

  • z – redshift measurement.

  • WM – Omega_matter. Default 0.3

  • WV – Omega_vacuum. Default 0.7

  • H0 – Hubble constant. (km s-1 Mpc-1) Default 70.0

Return

  • results – result dictionary including

  • dcmr_mpc – co-moving radius distance

  • da_mpc – angular distance

  • da_scale – angular distance scale

  • dl_mpc – luminosity distance (usually use this one)

  • dmod – distance modulus (determined from luminosity distance)

Todo

  • replace convert_redshift_to_distance in all other code

Usage

```python from astrocalc.distances import converter c = converter(log=log) dists = c.redshift_to_distance(

z=0.343

)

print(“Distance Modulus: “ + str(dists[“dmod”]) + “ mag”) print(“Luminousity Distance: “ + str(dists[“dl_mpc”]) + “ Mpc”) print(“Angular Size Scale: “ + str(dists[“da_scale”]) + “ kpc/arcsec”) print(“Angular Size Distance: “ + str(dists[“da_mpc”]) + “ Mpc”) print(“Comoving Radial Distance: “ + str(dists[“dcmr_mpc”]) + “ Mpc”)

# OUTPUT : # Distance Modulus: 41.27 mag # Luminousity Distance: 1795.16 Mpc # Angular Size Scale: 4.85 kpc/arcsec # Angular Size Distance: 999.76 Mpc # Comoving Radial Distance: 1339.68 Mpc

from astrocalc.distances import converter c = converter(log=log) dists = c.redshift_to_distance(

z=0.343, WM=0.286, WV=0.714, H0=69.6

)

print(“Distance Modulus: “ + str(dists[“dmod”]) + “ mag”) print(“Luminousity Distance: “ + str(dists[“dl_mpc”]) + “ Mpc”) print(“Angular Size Scale: “ + str(dists[“da_scale”]) + “ kpc/arcsec”) print(“Angular Size Distance: “ + str(dists[“da_mpc”]) + “ Mpc”) print(“Comoving Radial Distance: “ + str(dists[“dcmr_mpc”]) + “ Mpc”)

# OUTPUT : # Distance Modulus: 41.29 mag # Luminousity Distance: 1811.71 Mpc # Angular Size Scale: 4.89 kpc/arcsec # Angular Size Distance: 1008.97 Mpc # Comoving Radial Distance: 1352.03 Mpc ```