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The Balmer continuum in the spectra of AGN

The Balmer continuum in the spectra of AGN. Kova č evi ć , J., Popovic, L. Č., Kollatschny, W., Saikia, P. Introduction. In order to understand physical and kinematical properties of AGN emission regions we investigate the correlations between different spectral properties .

francesca-sereno
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The Balmer continuum in the spectra of AGN

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  1. The Balmer continuum in the spectra of AGN Kovačević, J., Popovic, L. Č., Kollatschny, W., Saikia, P.

  2. Introduction • In order to understand physical and kinematical properties of AGN emission regions we investigate the correlations between different spectral properties. • In previuos work we found: - kinematical linkage between optical Fe II lines and Intermediate Line Region (ILR), which indicates the ILR origin of optical Fe II. - different correlations between EWs of lines (and line components) vs. Lcont. - different correlations between spectral properties in “pure AGN” sample, and composit objects (AGN + starburst) sample, which indicates different physical processes in emission regions. - etc... (Kovačević et al. 2010, Popović et al. 2011) • Present work: extension of research to UV part of spectra! • GOAL: to compare UV and optical spectral properties (specially UV Fe II lines with optical Fe II, in order to find location of their emission region, etc.)

  3. UV pseudocontinuum • 1 step: determination ofthe UV pseudocontinuum in the sample! • Not easy because: 1. complex shape of UV pseudocontinuum: Power low + Balmer continuum(Grandi 1982) 2. Our sample contains spectra within spectral range: 2900 A – 5500 A (SDSS) (only two continuum windows : ~4200 A and ~5100A! Complex shape of UV pseudocontinuum cannot be fitted well! Tsuzuki et al. 2006

  4. Balmer continuum fitting: Tsuzuki et al. 2006, Sameshima et al. 2010 Sameshima et al. 2010

  5. Balmer continuum fitting: Jin et al. 2012 Convolving Balmer continuum equation with Gaussian (FWHM Gaussian = FWHM broad Hβ)

  6. Our model of Balmer continuum • We try to make model which: - we could use for fitting spectra within 2900 A – 5500 A range(with two continuum windows). It could be done by reducing number of free parameters: calculating the intensity of Balmer continuum! - we try to make good fit near Balmer edge (3646 A)! Our model consists of: Power law + Balmer continuum (λ<3646A) + high order Balmer lines (n=3-400), (λ>3646A) They are fitted by one Gaussian with the same width and shift as Hγ. The relative intensites for Balmer lines with n<50 are taken from the paper: Storey and Hummer 1995. Relative intensities for 50<n<400 are calculated using approximate formula: ≈1

  7. Examples of fit:

  8. Continuum window at 3000 A? 3000 A

  9. Conclusions: • The intensity of Balmer continuum near Balmer edge (~3646A) may be well estimated using fitting result for intensity of prominant Balmer lines (for example Hγ). • Model with high order Balmer lines n=3-400, for λ>3646A, improve the fit near Balmer edge. • Majority of analysed spectra have pseudocontinuum window at ~3000 A. • Calculated intensity of Balmer continuum, as well as one more continuum window (~3000A) should enable determination of UV pseudocontinuum in 2900 A – 5500 A range. • Future work: construction UV Fe II template, analysis of relationships between UV/optical spectral parameters... Thank you for your attention!

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