J/A+A/422/925 Profile variability in lines of NGC 5548 (Shapovalova+ 2004)
Profile variability of the Hα and Hβ broad emission lines in NGC 5548
Shapovalova A.I., Doroshenko V.T., Bochkarev N.G., Burenkov A.N.,
Carrasco L., Chavushyan V.H., Collin S., Valdes J.R., Borisov N.,
Dumont A.-M., Vlasuyk V.V., Chilingarian I., Fioktistova I.S.,
Martinez O.M.
<Astron. Astrophys. 422, 925 (2004)>
=2004A&A...422..925S 2004A&A...422..925S
ADC_Keywords: Active gal. nuclei ; Spectroscopy
Keywords: galaxies: active - galaxies: Seyfert -
galaxies: individual (NGC 5548) - line: profiles
Abstract:
Between 1996 and 2002, we have carried out a spectral monitoring
program for the Seyfert galaxy NGC 5548 with the 6m and 1m telescopes
of SAO (Russia) and with the 2.1m telescope of Guillermo Haro
Observatory (GHO) at Cananea, Mexico. High quality spectra with S/N>50
in the continuum near Hα and Hβ were obtained, covering the
spectral range ~(4000-7500)Å with a (4.5 to 15)Å-resolution.
We found that both the flux in the lines and the continuum gradually
decreased, reaching minimum values during May-June 2002. In the
minimum state, the wings of Hβ and Hα became extremely
weak, corresponding to a Sy1.8 type, not to a Sy1, as observed
previously when the nucleus was brighter. The line profiles were
decomposed into variable and constant components. The variable broad
component is well correlated with the continuum variation. It consists
of a double peaked structure with radial velocities ~±1000 km/s
relative to the narrow component. A constant component, whose presence
is independent of the continuum flux variations, shows only narrow
emission lines. The mean, rms, and the averaged over years, observed
and difference line profiles of Hβ and Hα reveal the same
double peaked structure. The relative intensity of these peaks changes
with time. During 1996, the red peak was the brightest, while in
1998-2002, the blue peak became the brighter one. Their radial
velocities vary in the ~(500-1200) km/s range. In 2000-2002 a distinct
third peak appeared in the red wing of Hα and Hβ line
profiles. The radial velocity of this feature decreased between 2000
and 2002: from the observed profiles, from ~+(2500-2600) km/s to
~+2000 km/s and is clearly seen on the difference profiles. The fluxes
of the various parts of the line profiles are well correlated with
each other and also with the continuum flux. The blue and red parts of
the line profiles at the same radial velocities vary in an almost
identical manner. Shape changes of the different parts of the broad
line are not correlated with continuum variations and, apparently, are
not related to reverberation effects. Changes of the integral Balmer
decrement are, on average, anticorrelated with the continuum flux
variations. This is probably due to an increasing role of collisional
excitation as the ionizing flux decreases. The behaviour of the Balmer
decrement of the various parts of the line profiles was different in
1996-2000 as compared with the 2001 behaviour. Our results favour the
formation of the broad Balmer lines in a turbulent accretion disc with
large and moving "optically thick" inhomogeneities, capable of
reprocessing the central source continuum.
Objects:
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RA (2000) DE Designation(s)
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14 17 59.65 +25 08 13.4 NGC 5548 = Mrk 1509
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
appenda.txt 74 91 Appendix A. "Modification of the spectrum scaling
method"
table2.dat 65 116 Log of the spectroscopic observations
table5.dat 58 116 Observed continuum, Hβ and Hα fluxes
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- No Number
5- 14 A10 "YYYY-MM-DD" Date UT date of the observation (G1)
16- 26 F11.3 d JD Julian Date
28- 29 A2 --- Tel A code assigned to each telescope +
equipment (G2)
31- 33 F3.1 arcsec AperW The projected spectrograph entrance
apertures (Slit Width)
35- 38 F4.1 arcsec AperL The projected spectrograph entrance
apertures (along Slit)
40- 43 I4 0.1nm Range1 Lower value of the spectral range
44 A1 --- --- [-]
45- 48 I4 0.1nm Range2 Upper value of the spectral range
50- 53 F4.1 0.1nm Resol Spectral Resolution
55- 57 F3.1 arcsec Seeing Seeing
59- 61 I3 deg PA ? Position Angle of the slit
63- 65 I3 --- S/N Signal-to-noise ratio in the continuum
at (5160-5220)Å near Hβ or
(6940-7040)Å near Hα
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 "YYYY-MM-DD" Date UT date of the observation (G1)
12- 22 F11.3 d JD Julian Date
24- 25 A2 --- Tel A code assigned to each telescope +
equipment (G2)
27- 31 F5.2 10-17W/m2/nm Fc ? The continuum flux at 5190Å, reduced
to the 1-m telescope aperture 4.2x19.8
arcsec (1)
32 A1 --- u_Fc Uncertainty flag (:) on Fc
33- 36 F4.2 10-17W/m2/nm e_Fc ? Estimated continuum flux error (1)
37 A1 --- ueFc Uncertainty flag (:) on e_Fc
38- 42 F5.2 10-16W/m2 FHbeta ? The Hβ total flux in spectral
range 4795-5018 Å (2)
44- 47 F4.2 10-16W/m2 e_FHbeta ? The Hβ flux error (2)
49- 53 F5.2 10-16W/m2 FHalpha ? The Hα total flux in spectral
range 6500-6800Å (2)
55- 58 F4.2 10-16W/m2 e_FHalpha ? The Hα flux error (2)
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Note (1): In units of 10-15erg/s/cm2/Å
Note (2): In units of 10-13erg/s/cm2
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Global notes:
Note (G1):
UT-date 2000-07-30 data were averaged inside 2 nights (2000-07-30 and
2000-07-31); for this case average JD is given.
Note (G2): The codes are:
L1: Observatory: SAO (Russia), Instrument: 1m+UAGS
L : Observatory: SAO (Russia), Instrument: 6m+UAGS
GH: Observatory: Guillermo Haro (Mexico), Instrument: 2.1m+B&C
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(End) A.N. Burenkov [SAO, Russia] 02-Aug-2004