This may actually confuse you and not help! This is just my personal reaction. I'm going to take on faith what you say and tell you my reaction to the exercise. That is the rule so that we don't do anything that would give you unfair advantage or short-circuit the teacher's strategy for making sure the students learn. Then someone here could help you understand the concepts and think about the example.īut if this is something where you hand in the answer for a grade then you should take it to "homework help" section. Sometimes in a textbook they have examples and exercises to THINK ABOUT, but you don't have to hand in your answer for a grade. I think I understand your situation, maybe. I am a mature student studying Astronomy for the first time. The value of the Hubble parameter at a given redshift.This is not a homework question. The distance corresponding to c / h, where c is the speed of lightĪnd h is the Hubble parameter in units of 1 / time. Z ( float) – Redshift hubble_distance ( ) ¶ It is also only functional for Gadget simulations, at the moment. There should be no negative sign).Īt the moment, this only works using the parameterization given in Linder 2002Įq. This function computes the additional term that enters the expansion factor This is also the primary function integrated to calculate theĬosmological distances.
The ratio between the Hubble parameter at a given redshift and in_units ( "Msun/Mpc**3" )) expansion_factor ( z ) ¶ > from yt.smology import Cosmology > co = Cosmology () > print ( co. CosmologicalĬonstant case corresponds to w_a = 0. w_a is the derivative of w(a) evaluated at a = 1.
Default is None.Ĭosmological constant case corresponds to w_0 = -1. W_0 ( float, optional) – The Linder 2002 parameterization of w(a) is: w(a) = w_0 + w_a(1 - a). This,Īlong with w_0 and w_a, only matters in the function expansion_factor. Or to use the parameterization of w(a) as given in Linder 2002. Use_dark_factor ( Bool, optional) – The flag to either use the cosmological constant (False, default) Unit_system ( yt.units.unit_systems.UnitSystem, optional) – The units system to use when making calculations. Omega_curvature ( the fraction of the energy density of the Universe in) – curvature. Omega_radiation ( the fraction of the energy density of the Universe in) – relativistic matter at redshift zero. Omega_lambda ( the fraction of the energy density of the Universe in) – a cosmological constant. Omega_matter ( the fraction of the energy density of the Universe in) – matter at redshift zero. Hubble_constant ( float) – The Hubble parameter at redshift zero in units of 100 km/s/Mpc. The user should takeĬare to understand which reference frame is correct for the given calculation. X, x.to(“Mpc”) and x.to(“Mpccm”) will be the same. Simplicity, the proper and comoving frames are set equal to each other In the comoving or proper frame, depending on the specific quantity. WARNING: Cosmological distance calculations return values that are either Cosmology ( hubble_constant = 0.71, omega_matter = 0.27, omega_lambda = 0.73, omega_radiation = 0.0, omega_curvature = 0.0, unit_registry = None, unit_system = 'cgs', use_dark_factor = False, w_0 = - 1.0, w_a = 0.0 ) ¶Ĭreate a cosmology calculator to compute cosmological distances and times.įor an explanation of the various cosmological measures, see, for example
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