Comoving_distance_and_lookback_time_(Planck_2018).png
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Summary
Description Comoving distance and lookback time (Planck 2018).png |
English:
This plot shows the comoving distance and lookback time for the Planck 2018 cosmology parameters, from redshift 0 to 15, with distance (blue solid line) on the left axis, and time (orange dashed line) on the right. Note that the time that has passed (in giga years) from a given redshift until now is not the same as the distance (in giga light years) to that redshift, due to the expansion of space over the intervening period.
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Date | |
Source | Own work |
Author | Parejkoj |
This plot was generated with the following python code, using astropy, numpy, and matplotlib:
import matplotlib.pyplot as plt
import numpy as np
import astropy.units as u
from astropy.cosmology import Planck18
z = np.arange(0, 15, 0.01)
fig, ax1 = plt.subplots()
ax2 = ax1.twinx()
fontkwargs = {"fontweight": "bold", "fontsize": "large"}
color1 = "blue"
lines1 = ax1.plot(z, Planck18.comoving_distance(z).to(u.Glyr),
label="distance (left axis)", color=color1)
ax1.set_xlim(0, 15)
ax1.set_xlabel("redshift (z)", fontweight="bold")
ax1.set_xticklabels(ax1.get_xticks(), weight="bold")
ax1.set_ylabel("comoving distance (giga light years)", color=color1, **fontkwargs)
ax1.tick_params(axis='y', colors=color1)
ax1.set_yticklabels(ax1.get_yticks(), weight="bold")
color2 = "darkorange"
# put them on the same vertical scale:
ax2.set_ylim(ax1.get_ylim())
lines2 = ax2.plot(z, Planck18.lookback_time(z), "--",
label="time (right axis)", color=color2)
ax2.set_ylabel("lookback time (giga years)", color=color2, **fontkwargs)
ax2.tick_params(axis='y', colors=color2)
ax2.set_yticklabels(ax2.get_yticks(), weight="bold")
ax1.grid()
lines = lines1 + lines2
ax1.legend(lines, [line.get_label() for line in lines], fontsize="large")
plt.savefig("comoving_distance_and_time.png", dpi=300, bbox_inches="tight")
plt.show()
input()
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