Long-Term Profile Variability of Double-Peaked Emmission Lines in AGNs

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The Interplay among Black Holes,Stars and ISM in Galactic Nuclei Proceedings IAU Symposium No.222,2004Th.Storchi Bergmann,L.C.Ho &H.R.Schmitt,eds.c 2004International Astronomical Union DOI:00.0000/X000000000000000X Long-Term Pro?le Variability of Double-Peaked Emission Lines in AGNs K.T.Lewis 1,M.Eracleous 1,J.P.Halpern 2&T.Storchi-Bergmann 31Department of Astronomy and Astrophysics,The Pennsylvania State University,525Davey Laboratory,University Park,PA 16802,USA 2Department of Astronomy,Columbia University,550West 120th Street,New York,NY 10027,USA 3Instituto de Fsica,UFRGS,91501-970Porto Alegre,RS,Brazi Abstract.An increasing number of AGNs exhibit broad,double-peaked Balmer emission lines,which arise from the outer regions of the accretion disk which fuels the AGN.The line pro?les vary on timescales of 5–10years.Our group has monitored a set of 20double-peaked emitters for the past 8years (longer for some objects).Here we describe a project to characterize the variability patterns of the double-peaked H αline pro?les and compare with those of two simple models:a circular disk with a spiral arm and an elliptical disk.

Lewis et al.

Figure1.Variability of data and model pro?le properties with time.(Left)PKS0921–213: The FWHM and FWQM,and corresponding shifts,are denoted with triangles and?lled circles, respectively.(Center)Spiral Arm Model:Variation of pro?le properties with phase for a disk with a one-armed spiral.The model parameters are:q=1.5;i=50?;ξ=1200–8000r g;σ=600 km/s;A=5;p=15?;δ=35?;andξsp=1200r g.The FWHM and FWQM are denoted with solid and dashed lines,respectively.(Right)Elliptical Model:Same as the Center panel,but for an elliptical disk with q=1.5,i=50?,ξ=1200–8000r g,σ=600km/s,e=0.15,andξe=1200r g. Thus,as a?rst step,we have begun characterizing the pro?le variability of our objects in a model independent way.Each pro?le is reduced to a set of easily measured quantities: the velocities of the red and blue peaks;the blue-to-red peak?ux ratio;the full widths at half and quarter maximum(FWHM and FWQM);and the velocity shifts of the FWHM and FWQM centroids.Sets of model pro?les,with a variety of input parameters,can be characterized in the same way for comparison with the data.

As an example,in Fig.1we show the pro?le parameter variations for PKS0921–213(left),a spiral arm model(center)and an elliptical disk model(right).The circular disk parameters(ξ1,ξ2,q,i,andσ)for both models are tuned to best-?t parameters of the average pro?le of PKS0931–213,while the additional model parameters are simply chosen for illustration.The most striking di?erence between the two models is that the elliptical disk pro?les always vary smoothly with phase,while those of the spiral arm model vary much more sharply.However,both models show potential for reproducing the observed pro?le variation.By creating“libraries”of model pro?les,we will be able to quickly select a small region of parameter space to test.

Acknowledgements

KTL is supported by a NASA GRSP grant NGT5-50387.

References

Eracleous,M.&Halpern,J.P.2003ApJ599,886.

Storchi-Bergmann,T.,Baldwin,J.A.,&Wilson,A.S.1993ApJL410,L11.