cosmocalc module

Calculate useful values for a given cosmology. This module uses code adapted from CC.py (James Schombert) which is a Python version of the Cosmology Calculator (Ned Wright).

The following values are calculated:

Name	Value	Units
z	Input redshift
H0	Hubble constant
WR	Omega(radiation)
WK	Omega curvaturve = 1-Omega(total)
WM	Omega matter
WV	Omega vacuum
DTT	Time from z to now	Gyr
age	Age of Universe	Gyr
zage	Age of Universe at redshift z	Gyr
DCMR	Comoving radial distance	Gyr Mpc cm
VCM	Comoving volume within redshift	Gpc3
DA	Angular size distance	Gyr Mpc cm
DL	Luminosity distance	Gyr Mpc cm
PS	Plate scale - distance per arcsec	kpc cm

Copyright

Smithsonian Astrophysical Observatory (2009)

Author

Tom Aldcroft (aldcroft@head.cfa.harvard.edu)

tw_source_finder.cosmocalc.cosmocalc(z, H0=71, WM=0.27, WV=None)

Calculate useful values for the supplied cosmology.

This routine returns a dictionary of values in the form <name>: <value>, where the values are supplied in “natural” units for cosmology, e.g. 1/H0. In addition various useful unit conversions are done and stored in the dictionary as <name>_<unit>: <value>. E.g. angular size distance:

'DA': 0.38250549415474988,
'DA_Gyr': 5.2678010166833023,
'DA_Mpc': 1615.1022857909447,
'DA_cm': 4.9836849147807571e+27

Example:

>>> from cosmocalc import cosmocalc
>>> from pprint import pprint
>>> pprint(cosmocalc(3, H0=75, WM=.25))
{'DA': 0.39103776375786625,
 'DA_Gyr': 5.0980896720325548,
 'DA_Mpc': 1563.0689649039205,
 'DA_cm': 4.8231268630387788e+27,
 'DCMR': 1.564151055031465,
 'DCMR_Gyr': 20.392358688130219,
 'DCMR_Mpc': 6252.2758596156818,
 'DCMR_cm': 1.9292507452155115e+28,
 'DL': 6.25660422012586,
 'DL_Gyr': 81.569434752520877,
 'DL_Mpc': 25009.103438462727,
 'DL_cm': 7.717002980862046e+28,
 'DTT': 0.84826379084317027,
 'DTT_Gyr': 11.059097795819358,
 'H0': 75,
 'PS_cm': 2.3383178917293232e+22,
 'PS_kpc': 7.5779721961095019,
 'VCM': 1.2756009121294902,
 'VCM_Gpc3': 1023.7714254161302,
 'WK': 0.0,
 'WM': 0.25,
 'WR': 7.4044444444444448e-05,
 'WV': 0.74992595555555552,
 'age': 1.0133755371756261,
 'age_Gyr': 13.211714670004362,
 'z': 3,
 'zage': 0.16511174633245579,
 'zage_Gyr': 2.1526168741850036}

Parameters

• z – redshift

• H0 – Hubble constant (default = 71)

• WM – Omega matter (default = 0.27)

• WV – Omega vacuum (default = 1.0 - WM - 0.4165/(H0*H0))

Return type

dictionary of cosmology values (name_unit = value)

tw_source_finder.cosmocalc.get_options()

cosmocalc.py [options] redshift [name_unit [name_unit2 …]]

Allowed name_unit values:

DA DA_Gyr DA_Mpc DA_cm
DL DL_Gyr DL_Mpc DL_cm
DCMR DCMR_Gyr DCMR_Mpc DCMR_cm
PS_kpc PS_cm
DTT DTT_Gyr
VCM VCM_Gpc3
age age_Gyr
zage zage_Gyr
H0 WM WV WK WR z

If no name_unit values are supplied then all the above will be printed.

tw_source_finder.cosmocalc.main()