Decoupled nuclei and nuclear polar rings in regular spiral galaxies - NGC 7217

Citation
Ok. Sil'Chenko et Vl. Afanasiev, Decoupled nuclei and nuclear polar rings in regular spiral galaxies - NGC 7217, ASTRON ASTR, 364(2), 2000, pp. 479-490
Citations number
46
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
0004-6361 → ACNP
Volume
364
Issue
2
Year of publication
2000
Pages
479 - 490
Database
ISI
SICI code
0004-6361(200012)364:2<479:DNANPR>2.0.ZU;2-X
Abstract
The regular isolated Sab galaxy NGC 7217 has been studied with the Multi-Pu pil Fiber Spectrograph of the 6m telescope of the Special Astrophysical Obs ervatory RAS (Nizhnij Arkhyz, Russia) in two spectral ranges, the blue one including the strong absorption lines Mg I and Fe I and the red one includi ng the emission lines H alpha and [N II]lambda 6583. We confirm the existen ce of a circumnuclear gaseous polar disk with a radius of 3 " which we repo rted earlier. The same area, with a radius of 3 " -4 ", elongated orthogona lly to the line of nodes, is distinguished by high values of the Lick index [Fe] and shows a Mg/Fe ratio lower than solar. This implies that there wer e at least two discrete star formation bursts in the circumnuclear region w ith a temporal separation of a few Gyrs. We relate this pair of bursts to t he complex structure of the global brightness profile of the galaxy, which may be decomposed into three exponential segments with different scalelengt hs.