SDSS Spectroscopic Data (pydl.pydlspec2d)

Introduction

This package provides functionality in the SDSS idlspec2d package. This package is used for processing and analyzing data from the SDSS optical spectrographs. The code is thus relevant to the SDSS Legacy, BOSS and eBOSS surveys. This package does not work with any infrared spectrograph data associated with the APOGEE-2 survey.

The primary technical focus of this particular implementation is the function combine1fiber(). This function is responsible for resampling 1D spectra onto a new wavelength solution. This allows for:

  1. Shifting a spectrum from observed redshift to rest frame.

  2. Coaddition of spectra of the same object, after resampling all spectra onto the same wavelength solution.

The primary scientific motivation of implementing combine1fiber() is to create template spectra based on curated spectra of, e.g., luminous red galaxies (LRGs). Principal Component Analysis (PCA) or other techniques may be used to construct template spectra, but putting all spectra on the same rest-frame wavelength solution is the first step.

The idlspec2d package is itself divided into a number of subpackages. Below we list the subpackages and the usability of the PyDL equivalent. The readiness levels are defined as:

Obsolete

No point in implementing because the purpose of the code lapsed many years ago.

Not Applicable (NA)

No point in implementing because another built-in or numpy/scipy/astropy package completely replaces this.

None

Not (yet) implemented at all.

Rudimentary

Only a few functions are implemented.

Fair

Enough functions are implemented to be useful, but some are missing.

Good

Pretty much anything you could do with the idlspec2d code you can do with the equivalent here.

Subpackage

Readiness Level

Comments

apo2d

None

Quick extraction code for quality assurance at observation time.

config

None

Extraction pipeline configuration parameters in object-oriented IDL.

fluxfix

None

Flux calibration

guider

None

Interface to guider camera.

inspect

None

Tools for manual inspection of spectra.

photoz

Obsolete

Photometric redshifts for SDSS objects using spectral templates.

plan

None

Tools for planning exposures and recordings summaries of exposures.

plate

Obsolete

Tools for designing SDSS spectroscopic plates, especially for star clusters.

science

None

Code for science analysis of sets of 1D spectra.

spec1d

Fair

Tools for processing 1D spectra, including redshift fitting.

spec2d

Fair

Tools for extracting spectra from 2D images.

specdb

Obsolete

Tests on storing spectroscopic results in SQL databases.

specflat

None

Flat-fielding of spectroscopic 2D images.

templates

None

Tools for constructing spectroscopic templates.

testsuite

None

Tools for high-level quality assurance, e.g. comparing two reductions of the same data.

API

pydl.pydlspec2d Package

This subpackage implements functions from the idlspec2d package.

Classes

Pydlspec2dException

Exceptions raised by pydl.pydlspec2d that don’t fit into a standard exception class like ValueError.

Pydlspec2dUserWarning

Class for warnings issued by pydl.pydlspec2d.

Class Inheritance Diagram

Inheritance diagram of pydl.pydlspec2d.Pydlspec2dException, pydl.pydlspec2d.Pydlspec2dUserWarning

pydl.pydlspec2d.spec1d Module

This module corresponds to the spec1d directory in idlspec2d.

Functions

findspec(*args, **kwargs)

Find SDSS/BOSS spectra that match a given RA, Dec.

latest_mjd(plate, **kwargs)

Find the most recent MJD associated with a plate.

number_of_fibers(plate, **kwargs)

Returns the total number of fibers per plate.

pca_solve(newflux, newivar[, maxiter, …])

Replacement for idlspec2d pca_solve.pro.

plot_eig(filename[, title])

Plot spectra from an eigenspectra/template file.

preprocess_spectra(flux, ivar[, loglam, …])

Handle the processing of input spectra through the combine1fiber() stage.

readspec(platein[, mjd, fiber])

Read SDSS/BOSS spec2d & spec1d files.

skymask(invvar, andmask[, ormask, ngrow])

Mask regions where sky-subtraction errors are expected to dominate.

spec_append(spec1, spec2[, pixshift])

Append the array spec2 to the array spec1 & return a new array.

spec_path(plate[, path, topdir, run2d])

Return the directory containing spPlate files.

template_input(inputfile, dumpfile[, flux, …])

Collect spectra and pass them to PCA or HMF solvers to compute spectral templates.

template_input_main()

Entry point for the compute_templates script.

template_metadata(inputfile[, verbose])

Read template metadata from file.

template_qso(metadata, newflux, newivar[, …])

Run PCA or HMF on QSO spectra.

template_star(metadata, newloglam, newflux, …)

Run PCA or HMF on stellar spectra of various classes.

wavevector(minfullwave, maxfullwave[, …])

Return an array of wavelengths.

Classes

FontProperties([family, style, variant, …])

A class for storing and manipulating font properties.

HMF(spectra, invvar[, K, n_iter, seed, …])

Class used to manage data for Heteroscedastic Matrix Factorization (HMF).

Class Inheritance Diagram

Inheritance diagram of pydl.pydlspec2d.spec1d.HMF

pydl.pydlspec2d.spec2d Module

This module corresponds to the spec2d directory in idlspec2d.

Functions

aesthetics(flux, invvar[, method])

Add nice values to a spectrum where it is masked.

combine1fiber(inloglam, objflux, newloglam)

Combine several spectra of the same object, or resample a single spectrum.

filter_thru(flux[, waveimg, wset, mask, …])

Compute throughput in SDSS filters.