Issue |
A&A
Volume 543, July 2012
|
|
---|---|---|
Article Number | A142 | |
Number of page(s) | 9 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201219299 | |
Published online | 12 July 2012 |
The analysis of the broad hydrogen Balmer line ratios: Possible implications for the physical properties of the broad line region of AGNs
1
Department of AstronomyFaculty of Mathematics, University of
Belgrade,
Studentski trg 16,
11000
Belgrade,
Serbia
e-mail: dilic@matf.bg.ac.rs
2
Isaac Newton Institute of Chile, Yugoslavia Branch, 11060
Belgrade,
Serbia
3
Astronomical Observatory, Volgina 7, 11160
Belgrade,
Serbia
4
Dipartimento di Fisica e Astronomia, Università di
Padova, Vicolo
dell’Osservatorio, 35122
Padova,
Italy
Received: 28 March 2012
Accepted: 10 May 2012
Aims. We analyze the ratios of the broad hydrogen Balmer emission lines (from Hα to Hε) in the context of estimating the physical conditions in the broad line region (BLR) of active galactic nuclei (AGNs).
Methods. Our measurements of the ratios of the Balmer emission lines are obtained in three ways: i) using photoionization models obtained with a spectral synthesis code CLOUDY; ii) applying the recombination theory for hydrogenic ions; iii) measuring the lines in observed spectra taken from the Sloan Digital Sky Survey database. We investigate the Balmer line ratios in the framework of the so-called Boltzmann plot (BP), analyzing the physical conditions of the emitting plasma for which we could use the BP method. The BP considers the ratio of Balmer lines normalized to the atomic data of the corresponding line transition, and in that way differs from the Balmer decrement.
Results. We find that for a certain range of thermodynamic parameters, there are objects that follow the BP. These AGNs may have a BLR consisting of mostly high density plasma.
Key words: galaxies: active / quasars: emission lines / line: formation / plasmas
© ESO, 2012
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.