astrocalc.distances.converter

Convert distances between measurement scales

Author

David Young

Module Contents

Classes

converter

A converter to switch distance between various units of measurement

API

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

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:

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

Initialization

distance_to_redshift(mpc)

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

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)

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

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