pygrc 0.2.0

A package to read SPARC data for Galactic Rotation Curves

pygrc

Author

Aman Desai

Description

A package to read SPARC data for Galactic Rotation Curves

Installation

pip install pygrc

Example Usage

• 1. Import libraries

import math
import numpy as np
import matplotlib.pyplot as plt
import pygrc as gr

• 2. Read Sparc Data

df = gr.Reader.read(filepath="/home/amdesai/Physics/data/NGC5055_rotmod.dat")
gr.Plot().overlap(df,"Rad",["Vobs","Vgas","Vbul","Vdisk"],"observed velocity")
df

• 3. Some sample function

# mond and mass function are based on Galaxies 2018, 6(3), 70; https://doi.org/10.3390/galaxies6030070

def mass(r, M0, R0):
    return M0*(1- (1+(r/R0))*np.exp(-r/R0))

def mond(r, M0, rc, R0,b, beta):
    a = 1.2e-10
    G = 4.300e-6 #parsecs
    m = mass(r,M0, R0)
    f = (G*m/r)*(1 + b*(1+(r/rc)))#*10e-3
    return np.sqrt(f)*10e-3

def newton(r, M0, rc, R0,beta):
    a = 1.2e-10
    G = 4.30e-6 #parsecs
    m = mass(r,M0, R0)
    f = G*m/r
    #f = (G*m/r)*(1/np.sqrt(2)) * np.sqrt(1 + np.sqrt(1 + (r**4) * (2*a/(G*m))**2))
    return np.sqrt(f)*10e-3

• 4a. Perform fit (uses iminuit in the background)

r = np.linspace(1e-5,df['Rad'].max(),2000)

m_1=gr.Fit(df['Rad'],df['Vobs'],1.,1.,3,.35,1.)

m_2=gr.Fit(df['Rad'],df['Vobs'],1.,1.,3,1.)

• 4b. Continue:

m1= m_1.fit_lsq(mond, [(1.,1e17),(1.,10.),(2.,5.),(0.1,2),(0.1,2)],df['errV'],[False,False,True,True,True])
m1

• 4c. Continue:

m2 = m_2.fit_lsq(newton, [(1.,1e16),(1.,10.),(1,10),(0.1,2)],df['errV'],[False,True,True,True])
m2

• 5a. draw plots

m_2.get_profile(m2,'M0')
m_1.draw_contours(m1,['M0','rc'])

• 6b.

fig, ax =plt.subplots()
gr.Plot().plot_grc(df,m1,mond,'MOND','NGC',ax)
gr.Plot().plot_grc(df,m2,newton,'Newton','NGC',ax)
plt.savefig('1.pdf')

References:

• SPARC Data can be obtained from here: http://astroweb.cwru.edu/SPARC/
• Mond and Mass function are based on Galaxies 2018, 6(3), 70; https://doi.org/10.3390/galaxies6030070