SDSS spectra Examples

Figure 7.1

A sample of 15 galaxy spectra selected from the SDSS spectroscopic data set (see Section 1.5.5). These spectra span a range of galaxy types, from star-forming to passive galaxies. Each spectrum has been shifted to its rest frame and covers the wavelength interval 3000-8000 Angstroms. The specific fluxes, , on the ordinate axes have an arbitrary scaling.

Code output:

Python source code:

# Author: Jake VanderPlas
# License: BSD
#   The figure produced by this code is published in the textbook
#   "Statistics, Data Mining, and Machine Learning in Astronomy" (2013)
#   For more information, see http://astroML.github.com
#   To report a bug or issue, use the following forum:
#    https://groups.google.com/forum/#!forum/astroml-general
import numpy as np
from matplotlib import pyplot as plt

from sklearn.decomposition import RandomizedPCA
from astroML.datasets import sdss_corrected_spectra

#----------------------------------------------------------------------
# This function adjusts matplotlib settings for a uniform feel in the textbook.
# Note that with usetex=True, fonts are rendered with LaTeX.  This may
# result in an error if LaTeX is not installed on your system.  In that case,
# you can set usetex to False.
from astroML.plotting import setup_text_plots
setup_text_plots(fontsize=8, usetex=True)

#----------------------------------------------------------------------
# Use pre-computed PCA to reconstruct spectra
data = sdss_corrected_spectra.fetch_sdss_corrected_spectra()
spectra = sdss_corrected_spectra.reconstruct_spectra(data)
lam = sdss_corrected_spectra.compute_wavelengths(data)

#------------------------------------------------------------
# select random spectra
np.random.seed(5)
nrows = 5
ncols = 3
ind = np.random.randint(spectra.shape[0], size=nrows * ncols)
spec_sample = spectra[ind]

#----------------------------------------------------------------------
# Plot the results
fig = plt.figure(figsize=(5, 4))

fig.subplots_adjust(left=0.05, right=0.95, wspace=0.05,
                    bottom=0.1, top=0.95, hspace=0.05)

for i in range(ncols):
    for j in range(nrows):
        ax = fig.add_subplot(nrows, ncols, ncols * j + 1 + i)
        ax.plot(lam, spec_sample[ncols * j + i], '-k', lw=1)

        ax.yaxis.set_major_formatter(plt.NullFormatter())
        ax.xaxis.set_major_locator(plt.MultipleLocator(1000))
        if j < nrows - 1:
            ax.xaxis.set_major_formatter(plt.NullFormatter())
        else:
            plt.xlabel(r'wavelength $(\AA)$')

        ax.set_xlim(3000, 7999)
        ylim = ax.get_ylim()
        dy = 0.05 * (ylim[1] - ylim[0])
        ax.set_ylim(ylim[0] - dy, ylim[1] + dy)

plt.show()

[download source: fig_spec_examples.py]