J/AJ/111/696 Rotation curves of Seyfert galaxies with companions (Keel 1996)
Seyfert galaxies with companions: orbital and kinematic clues to AGN triggering
Keel W.C.
<Astron. J. 111, 696 (1996)>
=1996AJ....111..696K 1996AJ....111..696K
ADC_Keywords: Galaxies, Seyfert ; Spectroscopy
Abstract:
This paper presents imaging and optical spectroscopy of paired Seyfert
galaxies and their companions. The aim is to seek common properties of
Seyfert galaxies in interacting systems, which might provide evidence
of AGN triggering in a way independent of the usual two-sample
statistics which have proven ambiguous on this issue. Three kinds of
comparison have been made -- the kinds of interactions involving
Seyfert galaxies, the relative luminosities of the Seyferts and their
companions, and the level of kinematic disturbance as measured from
rotation curves. (1) Dynamics and tidal features have been used to
determine (or at least limit) the sense of orbital motion (direct/
retrograde/polar with respect to the Seyfert galaxy's disk) for many
of these pairs. There is no obviously preferred kind of interaction --
direct, polar, and retrograde encounters are all well represented,
despite the gross differences in dynamical response of a disk to these
various kinds of encounter. To the extent that triggering of Seyfert
nuclei occurs due to tidal encounters, the existence of a perturbation
seems more important than its exact duration or detailed effects on
the disk. However, the ratio of merging to paired Seyferts is higher
than for disk galaxies in general, consistent with more effective
triggering of AGN in this specific phase; the implied time scale for
enhanced occurrence during mergers is the same as the timescape for
merger remnants to appear as such, a few disk-edge crossing times
(typically several times 10^8yr). (2) Seyfert nuclei occur
preferentially in the brighter members of galaxy pairs, by a median of
0.93mag after making the maximal correction for contaminating
nonstellar light in the nuclei. Only about 1/3 of this effect can be
accounted for by the known tendency of Seyfert nuclei to occur in more
luminous galaxies. Enhancement of AGN by interactions is evidently
more effective for more luminous galaxies (though this will also be
the case if both star formation and AGN occurrence are enhanced in the
same galaxies). (3) The rotation curves of the paired Seyferts show
systematically small regions of rising or solid-body rotation compared
to the disk radius, as a group comparable to Sa but very different
from Sb or Sc galaxies (even for Seyfert galaxies with Hubble type
later than Sa). There is weak evidence that this difference is also
present with respect to more isolated Seyfert galaxies. Despite the
obvious utility of a dynamically disturbed disk for transport of
angular momentum and "feeding the monster," Seyfert galaxies in pairs
actually have smaller kinematic disturbances (measured by the maximum
departure from a symmetric rotation curve, normalized to the full
rotation amplitude) than found in a complete sample of non-Seyfert
spirals in pairs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2 64 1317 Rotation curve data
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Byte-by-byte Description of file: table2
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Object name
11- 15 F5.1 deg PA []? Position angle
17- 21 F5.1 km/s dHRV []? Correction to heliocentric velocity
23- 28 F6.1 pix Peak []? Pixel number of continuum peak
30- 32 I3 pix Pixel *Pixel number along the slit
34- 40 F7.1 km/s RVobs *Mean radial velocity
42- 47 F6.1 km/s e_RVobs 2-sigma error derived from photon statistics
49- 55 F7.1 --- IHa *Total H-alpha intensity (instrumental units)
57- 62 F6.1 --- ICont Continuum intensity
64- 64 I1 --- Nlines No. of emission lines measured at each point
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Note on Pixel:
Pixel number along the slit, at a scale of 0.78 arcsec/pix.
Note on RVobs:
Mean radial velocity, in the observed frame and the so-called
relativistic convention.
Note on IHa:
Total H-alpha intensity in instrumental units (neglecting the
broad-line component where it can be distinguished).
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Origin: AAS CD-ROM series, Volume 6, 1996 Lee Brotzman [ADS] 08-Mar-1996
(End) [CDS] 05-Sep-1996