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QSFit: Automatic analysis of optical AGN spectra

QSFit: Automatic analysis of optical AGN spectra
QSFit: Automatic analysis of optical AGN spectra
We present QSFit (Quasar Spectral Fitting package), a new software package to automatically perform the analysis of active galactic nuclei (AGNs) optical spectra. The software provides luminosity estimates for the AGN continuum, the Balmer continuum, both optical and ultraviolet iron blended complex, host galaxy and emission lines, as well as width, velocity offset and equivalent width of 20 emission lines. Improving on a number of previous studies on AGN spectral analysis, QSFit fits all the components simultaneously, using an AGN continuum model which extends over the entire available spectrum, and is thus a probe of the actual AGN continuum whose estimates are scarcely influenced by localized features (e.g. emission lines) in the spectrum. We used QSFit to analyse 71  251 optical spectra of Type 1 AGN at z < 2 (obtained by the Sloan Digital Sky Survey, SDSS) and to produce a publicly available catalogue of AGN spectral properties. Such catalogue allowed us (for the first time) to estimate the AGN continuum slope and the Balmer continuum luminosity on a very large sample, and to show that there is no evident correlation between these quantities the redshift. All data in the catalogue, the plots with best-fitting model and residuals, and the idl code we used to perform the analysis, are available on a dedicated website. The whole fitting process is customizable for specific needs, and can be extended to analyse spectra from other data sources. The ultimate purpose of QSFit is to allow astronomers to run standardized recipes to analyse the AGN data, in a simple, replicable and shareable way.
0035-8711
4051-4080
Calderone, G.
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Nicastro, L.
42185586-078e-448c-b211-ff027710a690
Ghisellini, G.
fec5c1a5-4bd3-4773-9dac-9dd63972e63e
Dotti, M.
d18ba59a-6d52-4ec5-b66c-aeed4a6d7c46
Sbarrato, T.
d8a19c5c-1671-4b15-b653-a6331289d580
Shankar, F.
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Colpi, M.
cbdfd761-2a6c-41a3-8e1f-cd86ee437182
Calderone, G.
9d3e93d9-a15c-41eb-9886-52b4f1c8f5a1
Nicastro, L.
42185586-078e-448c-b211-ff027710a690
Ghisellini, G.
fec5c1a5-4bd3-4773-9dac-9dd63972e63e
Dotti, M.
d18ba59a-6d52-4ec5-b66c-aeed4a6d7c46
Sbarrato, T.
d8a19c5c-1671-4b15-b653-a6331289d580
Shankar, F.
b10c91e4-85cd-4394-a18a-d4f049fd9cdb
Colpi, M.
cbdfd761-2a6c-41a3-8e1f-cd86ee437182

Calderone, G., Nicastro, L., Ghisellini, G., Dotti, M., Sbarrato, T., Shankar, F. and Colpi, M. (2017) QSFit: Automatic analysis of optical AGN spectra. Monthly Notices of the Royal Astronomical Society, 472 (4), 4051-4080. (doi:10.1093/mnras/stx2239).

Record type: Article

Abstract

We present QSFit (Quasar Spectral Fitting package), a new software package to automatically perform the analysis of active galactic nuclei (AGNs) optical spectra. The software provides luminosity estimates for the AGN continuum, the Balmer continuum, both optical and ultraviolet iron blended complex, host galaxy and emission lines, as well as width, velocity offset and equivalent width of 20 emission lines. Improving on a number of previous studies on AGN spectral analysis, QSFit fits all the components simultaneously, using an AGN continuum model which extends over the entire available spectrum, and is thus a probe of the actual AGN continuum whose estimates are scarcely influenced by localized features (e.g. emission lines) in the spectrum. We used QSFit to analyse 71  251 optical spectra of Type 1 AGN at z < 2 (obtained by the Sloan Digital Sky Survey, SDSS) and to produce a publicly available catalogue of AGN spectral properties. Such catalogue allowed us (for the first time) to estimate the AGN continuum slope and the Balmer continuum luminosity on a very large sample, and to show that there is no evident correlation between these quantities the redshift. All data in the catalogue, the plots with best-fitting model and residuals, and the idl code we used to perform the analysis, are available on a dedicated website. The whole fitting process is customizable for specific needs, and can be extended to analyse spectra from other data sources. The ultimate purpose of QSFit is to allow astronomers to run standardized recipes to analyse the AGN data, in a simple, replicable and shareable way.

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QSFit: Automatic analysis of optical AGN spectra - Accepted Manuscript
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Accepted/In Press date: 30 August 2017
e-pub ahead of print date: 5 September 2017
Published date: December 2017

Identifiers

Local EPrints ID: 416089
URI: https://eprints.soton.ac.uk/id/eprint/416089
ISSN: 0035-8711
PURE UUID: 273a1daf-30a6-4cc0-b545-96a731c240ae

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Date deposited: 01 Dec 2017 17:30
Last modified: 13 Mar 2019 19:15

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