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- Fathi, Kambiz, et al.
(författare)
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AN H alpha NUCLEAR SPIRAL STRUCTURE IN THE E0 ACTIVE GALAXY Arp 102B
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 736:2, s. 77-
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of a two-armed mini-spiral structure within the inner kiloparsec of the E0 LINER/Seyfert 1 galaxy Arp 102B. The arms are observed in H alpha emission and located east and west of the nucleus, extending up to approximate to 1 kpc from it. We use narrow-band imaging from the Hubble Space Telescope Advanced Camera for Surveys, in combination with archival Very Large Array radio images at 3.6 and 6 cm to investigate the origin of the nuclear spiral. From the H alpha luminosity of the spiral, we obtain an ionized gas mass of the order of 10(6) solar masses. One possibility is that the nuclear spiral represents a gas inflow triggered by a recent accretion event which has replenished the accretion disk, giving rise to the double-peaked emission-line profiles characteristic of Arp 102B. However, the radio images show a one-sided curved jet which correlates with the eastern spiral arm observed in the H alpha image. A published milliarcsecond radio image also shows a one-sided structure at position angle approximate to 40 degrees, approximately aligned with the inner part of the eastern spiral arm. The absence of a radio counterpart to the western spiral arm is tentatively interpreted as indicating that the jet is relativistic, with an estimated speed of 0.45c. Estimates of the jet kinetic energy and the ionizing luminosity of the active nucleus indicate that both are capable of ionizing the gas along the spiral arms. We conclude that, although the gas in the nuclear region may have originated in an accretion event, the mini spiral is most likely the result of a jet-cloud interaction rather than an inflowing stream.
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| 2. |
- Storchi-Bergmann, Thaisa, et al.
(författare)
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{Nuclear spirals as feeding channels to the Supermassive Black Hole: the case of the galaxy NGC6951
- 2007
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Ingår i: Astropjysical Journals. - : American Astronomical Society. ; 670:959
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- We report the discovery of gas streaming motions along nuclear spiral arms toward the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Hα, [N ii] λ6584, and [S ii] λλ6717, 6731 emission lines of the inner 7x15 arcsec of the galaxy. This region includes a circumnuclear star‐forming ring with a radius of 500 pc, a nuclear spiral inside the ring, and the LINER nucleus. The kinematics of the ionized gas is dominated by rotation, but subtraction of a kinematic model of a rotating exponential disk reveals deviations from circular rotation within the nuclear ring that can be attributed to (1) streaming motions along the nuclear spiral arms and (2) a bipolar outflow that seems to be associated with a nuclear jet. On the basis of the observed streaming velocities and geometry of the spiral arms, we estimate a mass inflow rate of ionized gas of ≈ 3x10^-4 M yr−1, which is on the order of the accretion rate necessary to power the LINER nucleus of NGC 6951. Similar streaming motions toward the nucleus of another galaxy with a LINER nucleus, NGC 1097, have been reported by our group in a previous paper. Taken together, these results support a scenario in which nuclear spirals are channels through which matter is transferred from galactic scales to the nuclear region to feed the supermassive black hole.
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