Quasar Spectral FITting package
QSFit is a software package to automatically perform spectral analysis of Active Galactic Nuclei (AGN) optical/UV spectra.
It provides estimates of:
- AGN continuum luminosities and slopes at several rest frame wavelengths;
- host galaxy luminosities (for sources with z < 0.8);
- luminosities, widths and velocity offsets of 20 individual
emission lines (Hα, Hβ, MgII, [OIII], CIV, etc.), and luminosity of
the blended Balmer lines (n ≥ 7);
- luminosities of iron blended lines at optical and UV wavelengths;
- luminosity of the Balmer continuum;
- several "quality flags" to assess the reliability of the results.
The main purpose of QSFit is to allow anyone to perform AGN spectral analysis in a simple, replicable and shareable way.
The code is available on Github and can be easily customized for specific purposes.
The paper was published on MNRAS, 472, 4051-4080 (2017).
Preprint available from arXiv.
If you make use of the catalogue or the code, please unknowledge as: Calderone et al., MNRAS, 472, 4051 (2017)
New version released (v1.3.0)
A new QSFit version is available, see Changelog in Github
Also, a new online calculator is available.
Catalog of spectral properties ver. 1.2.4
After the publication of the paper we found a few small bugs
in the code affecting:
- the freezing/thawing of the iron template component at optical
wavelengths (this bug affected only the spectral estimates for the
sources with z < 0.4);
- the calculation of the spectral coverage of the emission lines
(this bug affected only those source with many spectral channels
whose quality mask is not zero, as marked by the SDSS reduction
- the spectral estimates of QSFit had a very weak dependence on the
data type precision of the input keyword Z and EBV: changing them
from FLOAT to DOUBLE would introduce slight discrepancies in the
We fixed all these bugs and generated a new QSFit catalogue. The
spectral estimates, in the vast majority of cases, are compatible with
the previous ones (within the quoted uncertainties).
The new catalogue is available here
and the new source code
release can be downloaded here
We used QSFit to analyze 71,251 optical spectra (from SDSS-DR10
) of Type 1 AGN at z < 2, and compiled a catalogue of spectral properties. See the reference paper.
The catalogue can be explored online using the dedicated web tools
or downloaded as a FITS file.
The complete data analysis can be easily replicated by running QSFit (as shown in the example below) on all the spectra in the sample.
The old version 1.2 is available here.
Source Code (Github)
The source code can be downloaded from Github
The software is written in IDL and released under the GPL license
The prerequisites to run QSFit are IDL (ver. >= 8.1) and Gnuplot
(ver. >= 5.0).
To run QSFit you should download and unzip the package from Github, then
change to the directory where you unpacked the source code and start an
IDL session. There is no need to change the IDL PATH system variable,
QSFit provides a simple way to compile all the required procedures:
at the IDL prompt.
The QSFit package already comes with a SDSS DR-10 FITS file to test the
code. The commands to run the analysis and plot the results are:
res = qsfit(’data/spec-0752-52251-0323.fits’, z=0.3806, ebv=0.06846)
Further informations may be found in Appendix B of the reference paper (arXiv