The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Resolving the active galactic nucleus and host emission in the mid-infrared using a model-independent spectral decomposition

Resolving the active galactic nucleus and host emission in the mid-infrared using a model-independent spectral decomposition
Resolving the active galactic nucleus and host emission in the mid-infrared using a model-independent spectral decomposition
We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1σ dispersion of 0.12 dex in luminosity and typical uncertainties of ~0.19 in the spectral index and ~0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies—currently inaccessible to ground-based observations—with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope. The decomposition code and templates are available at http://denebola.org/ahc/deblendIRS.
1538-4357
1-16
Hernán-Caballero, Antonio
5237c1fb-c6c6-4ec2-9074-364f6c2239a4
Alonso-Herrero, Almudena
8672ba48-8f27-45f2-a89f-2c62f8e34261
Hatziminaoglou, Evanthia
b900737e-d2b3-4e14-998c-5f699dfe7a22
Spoon, Henrik W.W.
2468094a-d8fc-485c-9e95-37b090d6d2be
Almeida, Cristina Ramos
407b9f57-0072-415e-826d-7f711fc5fe65
Santos, Tanio Díaz
e6e4d07f-2651-4815-931a-e303ec962313
Hoenig, Sebastian
be0bb8bc-bdac-4442-8edc-f735834f3917
González-Martín, Omaira
9d84142f-c1c3-4d3d-aaf6-ce241e356335
Esquej, Pilar
0a5aef84-f289-4141-a5c9-aff549ffac1a
Hernán-Caballero, Antonio
5237c1fb-c6c6-4ec2-9074-364f6c2239a4
Alonso-Herrero, Almudena
8672ba48-8f27-45f2-a89f-2c62f8e34261
Hatziminaoglou, Evanthia
b900737e-d2b3-4e14-998c-5f699dfe7a22
Spoon, Henrik W.W.
2468094a-d8fc-485c-9e95-37b090d6d2be
Almeida, Cristina Ramos
407b9f57-0072-415e-826d-7f711fc5fe65
Santos, Tanio Díaz
e6e4d07f-2651-4815-931a-e303ec962313
Hoenig, Sebastian
be0bb8bc-bdac-4442-8edc-f735834f3917
González-Martín, Omaira
9d84142f-c1c3-4d3d-aaf6-ce241e356335
Esquej, Pilar
0a5aef84-f289-4141-a5c9-aff549ffac1a

Hernán-Caballero, Antonio, Alonso-Herrero, Almudena, Hatziminaoglou, Evanthia, Spoon, Henrik W.W., Almeida, Cristina Ramos, Santos, Tanio Díaz, Hoenig, Sebastian, González-Martín, Omaira and Esquej, Pilar (2015) Resolving the active galactic nucleus and host emission in the mid-infrared using a model-independent spectral decomposition. The Astrophysical Journal, 803 (2), 1-16. (doi:10.1088/0004-637X/803/2/109).

Record type: Article

Abstract

We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1σ dispersion of 0.12 dex in luminosity and typical uncertainties of ~0.19 in the spectral index and ~0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies—currently inaccessible to ground-based observations—with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope. The decomposition code and templates are available at http://denebola.org/ahc/deblendIRS.

Text
__filestore.soton.ac.uk_users_skr1c15_mydocuments_eprints_ASTRO_Sebastian Hoenig_Resolving the AGN and Host emission in the mid.pdf - Accepted Manuscript
Download (1MB)

More information

Accepted/In Press date: 12 February 2015
Published date: 22 April 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 402385
URI: http://eprints.soton.ac.uk/id/eprint/402385
ISSN: 1538-4357
PURE UUID: c76adf18-0567-4509-b455-0ad248f16be6

Catalogue record

Date deposited: 08 Nov 2016 11:17
Last modified: 21 Nov 2021 04:19

Export record

Altmetrics

Contributors

Author: Antonio Hernán-Caballero
Author: Almudena Alonso-Herrero
Author: Evanthia Hatziminaoglou
Author: Henrik W.W. Spoon
Author: Cristina Ramos Almeida
Author: Tanio Díaz Santos
Author: Omaira González-Martín
Author: Pilar Esquej

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×