Tutorials & Examples

Example: Accessing the database and creating a figure

This example creates a figure comparing half-light radius and absolute magnitude of dwarf galaxies and star clusters.

Load required packages.

import numpy as np
import matplotlib.pyplot as plt
import astropy.table as table

load the data from github

dsph_mw = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/dwarf_mw.csv')
dsph_m31 = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/dwarf_m31.csv')
dsph_lf = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/dwarf_local_field.csv')
ufsc = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/gc_ufsc.csv')
gc_disk = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/gc_disk.csv')
gc_harris = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/main/data/gc_harris.csv')

make a figure

def const_mu(muV, rhalf):
    return muV - 36.57 - 2.5 * np.log10(2.*np.pi*rhalf**2)
x = np.arange(1, 1e4, 1)
for mu in [24, 26, 28, 30, 32]:
    plt.plot(x,  [const_mu(mu, i/1000.) for i in x], c='k', lw=2, ls=':')

plt.errorbar(dsph_mw['rhalf_sph_physical'], dsph_mw['M_V'], fmt='o', label=r'${\rm Dwarf~MW}$', )
plt.plot(dsph_m31['rhalf_sph_physical'], dsph_m31['M_V'], 'o', label=r'${\rm Dwarf~M31}$')
plt.plot(dsph_lf['rhalf_sph_physical'],dsph_lf['M_V'], 'o', label=r'${\rm Dwarf~LF}$')
plt.plot(ufsc['rhalf_sph_physical'], ufsc['M_V'], 'o',label=r'${\rm UFSC}$')
plt.plot(gc_disk['rhalf_sph_physical'], gc_disk['M_V'], 'o',label=r'${\rm GC~New}$')
plt.plot(gc_harris['rhalf_sph_physical'], gc_harris['M_V'], 'o',label=r'${\rm GC~Harris}$')
plt.gca().set_xscale('log')
plt.gca().invert_yaxis()
plt.gca().set_xlabel(r'$r_{1/2}~({\rm pc})$')
plt.gca().set_ylabel(r'$M_V$')
plt.legend(loc=(2))
plt.ylim(3, -20)
plt.xlim(1, 4e3)
## plt.tight_layout()
## plt.savefig('/example_rhalf_MV.png')
plt.show()

Figure from the sample (this does include custom matplotlib stylefile and latex for the captions).

Some Recommendations

For detailed analysis, I would recommendation fixing the version of the tables instead of the current version. Each table can be loaded from a specific commit. For example, this loads an older version of the data/dwarf_mw.csv table.

dsph_mw = table.Table.read('https://raw.githubusercontent.com/apace7/local_volume_database/3a473c7f839f228a5702fa0293cebfea5fe3bcb6/data/dwarf_mw.csv')