The University of Southampton
University of Southampton Institutional Repository

Do reverberation mapping analyses provide an accurate picture of the broad line region?

Do reverberation mapping analyses provide an accurate picture of the broad line region?
Do reverberation mapping analyses provide an accurate picture of the broad line region?
Reverberation mapping (RM) is a powerful approach for determining the nature of the broad-line region (BLR) in active galactic nuclei. However, inferring physical BLR properties from an observed spectroscopic time series is a difficult inverse problem. Here, we present a blind test of two widely used RM methods: MEMEcho (developed by Horne) and CARAMEL (developed by Pancoast and collaborators). The test data are simulated spectroscopic time series that track the H$\alpha$ emission line response to an empirical continuum light curve. The underlying BLR model is a rotating, biconical accretion disc wind, and the synthetic spectra are generated via self-consistent ionization and radiative transfer simulations. We generate two mock data sets, representing Seyfert galaxies and QSOs. The Seyfert model produces a largely *negative* response, which neither method can recover. However, both fail $"gracefully"$, neither generating spurious results. For the QSO model both CARAMEL and expert interpretation of MEMEcho's output both capture the broadly annular, rotation-dominated nature of the line-forming region, though MEMEcho analysis overestimates its size by 50%, but CARAMEL is unable to distinguish between additional inflow and outflow components. Despite fitting individual spectra well, the CARAMEL velocity-delay maps and RMS line profiles are strongly inconsistent with the input data. Finally, since the H$\alpha$ line-forming region is rotation dominated, neither method recovers the disc wind nature of the underlying BLR model. Thus considerable care is required when interpreting the results of RM analyses in terms of physical models.
astro-ph.GA
0035-8711
Mangham, S. W.
c2053240-de45-4451-8cad-213930722d2e
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Williams, P.
b5fece76-e353-4981-b238-8428535aac72
Horne, Keith
ffcda7c7-9cd8-4043-be08-c5db52b80e71
Pancoast, A.
40f24ac8-731e-4eb3-83a0-4a39b67dbcb4
Matthews, J. H.
8aa37525-32b9-460c-bb83-01c89269ac31
Long, K. S.
839b3509-5ef3-4126-97fa-912e3357d8ef
Sim, S. A.
7df85a4e-ebca-4700-b95c-90a6427985ea
Higginbottom, N.
0ffe077c-dde2-46d6-9684-867f54399d25
Mangham, S. W.
c2053240-de45-4451-8cad-213930722d2e
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Williams, P.
b5fece76-e353-4981-b238-8428535aac72
Horne, Keith
ffcda7c7-9cd8-4043-be08-c5db52b80e71
Pancoast, A.
40f24ac8-731e-4eb3-83a0-4a39b67dbcb4
Matthews, J. H.
8aa37525-32b9-460c-bb83-01c89269ac31
Long, K. S.
839b3509-5ef3-4126-97fa-912e3357d8ef
Sim, S. A.
7df85a4e-ebca-4700-b95c-90a6427985ea
Higginbottom, N.
0ffe077c-dde2-46d6-9684-867f54399d25

Mangham, S. W., Knigge, C., Williams, P., Horne, Keith, Pancoast, A., Matthews, J. H., Long, K. S., Sim, S. A. and Higginbottom, N. (2019) Do reverberation mapping analyses provide an accurate picture of the broad line region? Monthly Notices of the Royal Astronomical Society. (doi:10.1093/mnras/stz1713).

Record type: Article

Abstract

Reverberation mapping (RM) is a powerful approach for determining the nature of the broad-line region (BLR) in active galactic nuclei. However, inferring physical BLR properties from an observed spectroscopic time series is a difficult inverse problem. Here, we present a blind test of two widely used RM methods: MEMEcho (developed by Horne) and CARAMEL (developed by Pancoast and collaborators). The test data are simulated spectroscopic time series that track the H$\alpha$ emission line response to an empirical continuum light curve. The underlying BLR model is a rotating, biconical accretion disc wind, and the synthetic spectra are generated via self-consistent ionization and radiative transfer simulations. We generate two mock data sets, representing Seyfert galaxies and QSOs. The Seyfert model produces a largely *negative* response, which neither method can recover. However, both fail $"gracefully"$, neither generating spurious results. For the QSO model both CARAMEL and expert interpretation of MEMEcho's output both capture the broadly annular, rotation-dominated nature of the line-forming region, though MEMEcho analysis overestimates its size by 50%, but CARAMEL is unable to distinguish between additional inflow and outflow components. Despite fitting individual spectra well, the CARAMEL velocity-delay maps and RMS line profiles are strongly inconsistent with the input data. Finally, since the H$\alpha$ line-forming region is rotation dominated, neither method recovers the disc wind nature of the underlying BLR model. Thus considerable care is required when interpreting the results of RM analyses in terms of physical models.

Text
1906.11272v1 - Accepted Manuscript
Download (3MB)

More information

e-pub ahead of print date: 21 June 2019
Published date: 26 June 2019
Additional Information: 22 pages, 24 figures
Keywords: astro-ph.GA

Identifiers

Local EPrints ID: 432565
URI: https://eprints.soton.ac.uk/id/eprint/432565
ISSN: 0035-8711
PURE UUID: 4275314c-704c-4506-aac4-37b44c7ba19d
ORCID for S. W. Mangham: ORCID iD orcid.org/0000-0001-7511-5652

Catalogue record

Date deposited: 18 Jul 2019 16:30
Last modified: 26 Nov 2019 01:29

Export record

Altmetrics

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 https://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.

×