Hot gas and magnetic arms of NGC 6946 : indications for reconnection heating?

2016
journal article
article
5
dc.abstract.enContext. The grand-design face-on spiral galaxy NGC 6946 is remarkable because of its high star formation activity, the massive northern spiral arm, and the magnetic arms, which are observed in polarized radio synchrotron emission and are located between the optical arms and possibly are magnetic reconnection regions. Aims. We used electron densities and temperatures in star-forming (active) and less active regions and compared them to findings from the analysis of the radio data to study the energy budget of NGC 6946. The hot gas above the magnetic arms between the optical arms might suggest gas heating by reconnection. We also study the population of point sources in NGC 6946, including the origin of the puzzling ultra-luminous emission complex MF16. Methods. X-ray observations of NGC 6946 performed with XMM-Newton were used to study the emission from X-ray point sources and diffuse hot gas, including the magnetic arms and the halo. Spectral fitting of the diffuse X-ray emission allowed us to derive temperatures of the hot gas. With assumptions about the emission volume, this allowed us to estimate gas densities, masses, and cooling times. Results. To explain the X-ray emission from the spiral arms of NGC 6946 two-temperature plasma models are needed to account for the disk and halo emission. The interarm regions show only one thermal component. We observe that the temperature of the hot gas in and above the magnetic arm regions increases slightly when compared to the average temperatures in the areas in and above the spiral arms. For the southwestern part of the disk, which is depolarized in the radio range by Faraday rotation, we find more efficient mixing of disk and halo gas. Conclusions. We propose magnetic reconnection in the magnetic arm regions of NGC 6946 as the possible cause of the additional heating of the gas and ordering of the magnetic fields. In the southwestern part of the galactic disk we observed indications of a possible faster outflow of the hot gas. A very hot gas within the MF 16 nebula possibly suggests shock heating by a supernova explosion.pl
dc.affiliationWydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut – Obserwatorium Astronomicznepl
dc.contributor.authorWeżgowiec, Marek - 253977 pl
dc.contributor.authorEhle, M.pl
dc.contributor.authorBeck, R.pl
dc.date.accessioned2016-01-04T10:45:13Z
dc.date.available2016-01-04T10:45:13Z
dc.date.issued2016pl
dc.date.openaccess12
dc.description.accesstimepo opublikowaniu
dc.description.additionalReproduced with permission from Astronomy & Astrophysics, © ESOpl
dc.description.versionostateczna wersja wydawcy
dc.description.volume585pl
dc.identifier.articleidA3pl
dc.identifier.doi10.1051/0004-6361/201526833pl
dc.identifier.eissn1432-0746pl
dc.identifier.issn0004-6361pl
dc.identifier.projectROD UJ / Ppl
dc.identifier.urihttp://ruj.uj.edu.pl/xmlui/handle/item/18853
dc.languageengpl
dc.language.containerengpl
dc.rightsUdzielam licencji. Uznanie autorstwa - Użycie niekomercyjne - Na tych samych warunkach 4.0 Międzynarodowa*
dc.rights.licenceInna otwarta licencja
dc.rights.urihttp://creativecommons.org/licenses/by-nc-sa/4.0/legalcode.pl*
dc.share.typeotwarte czasopismo
dc.subject.engalaxies: individual: NGC 6946pl
dc.subject.engalaxies: ISMpl
dc.subject.engalaxies: spiralpl
dc.subject.engalaxies: magnetic fieldspl
dc.subtypeArticlepl
dc.titleHot gas and magnetic arms of NGC 6946 : indications for reconnection heating?pl
dc.title.journalAstronomy & Astrophysicspl
dc.typeJournalArticlepl
dspace.entity.typePublication
dc.abstract.enpl
Context. The grand-design face-on spiral galaxy NGC 6946 is remarkable because of its high star formation activity, the massive northern spiral arm, and the magnetic arms, which are observed in polarized radio synchrotron emission and are located between the optical arms and possibly are magnetic reconnection regions. Aims. We used electron densities and temperatures in star-forming (active) and less active regions and compared them to findings from the analysis of the radio data to study the energy budget of NGC 6946. The hot gas above the magnetic arms between the optical arms might suggest gas heating by reconnection. We also study the population of point sources in NGC 6946, including the origin of the puzzling ultra-luminous emission complex MF16. Methods. X-ray observations of NGC 6946 performed with XMM-Newton were used to study the emission from X-ray point sources and diffuse hot gas, including the magnetic arms and the halo. Spectral fitting of the diffuse X-ray emission allowed us to derive temperatures of the hot gas. With assumptions about the emission volume, this allowed us to estimate gas densities, masses, and cooling times. Results. To explain the X-ray emission from the spiral arms of NGC 6946 two-temperature plasma models are needed to account for the disk and halo emission. The interarm regions show only one thermal component. We observe that the temperature of the hot gas in and above the magnetic arm regions increases slightly when compared to the average temperatures in the areas in and above the spiral arms. For the southwestern part of the disk, which is depolarized in the radio range by Faraday rotation, we find more efficient mixing of disk and halo gas. Conclusions. We propose magnetic reconnection in the magnetic arm regions of NGC 6946 as the possible cause of the additional heating of the gas and ordering of the magnetic fields. In the southwestern part of the galactic disk we observed indications of a possible faster outflow of the hot gas. A very hot gas within the MF 16 nebula possibly suggests shock heating by a supernova explosion.
dc.affiliationpl
Wydział Fizyki, Astronomii i Informatyki Stosowanej : Instytut – Obserwatorium Astronomiczne
dc.contributor.authorpl
Weżgowiec, Marek - 253977
dc.contributor.authorpl
Ehle, M.
dc.contributor.authorpl
Beck, R.
dc.date.accessioned
2016-01-04T10:45:13Z
dc.date.available
2016-01-04T10:45:13Z
dc.date.issuedpl
2016
dc.date.openaccess
12
dc.description.accesstime
po opublikowaniu
dc.description.additionalpl
Reproduced with permission from Astronomy & Astrophysics, © ESO
dc.description.version
ostateczna wersja wydawcy
dc.description.volumepl
585
dc.identifier.articleidpl
A3
dc.identifier.doipl
10.1051/0004-6361/201526833
dc.identifier.eissnpl
1432-0746
dc.identifier.issnpl
0004-6361
dc.identifier.projectpl
ROD UJ / P
dc.identifier.uri
http://ruj.uj.edu.pl/xmlui/handle/item/18853
dc.languagepl
eng
dc.language.containerpl
eng
dc.rights*
Udzielam licencji. Uznanie autorstwa - Użycie niekomercyjne - Na tych samych warunkach 4.0 Międzynarodowa
dc.rights.licence
Inna otwarta licencja
dc.rights.uri*
http://creativecommons.org/licenses/by-nc-sa/4.0/legalcode.pl
dc.share.type
otwarte czasopismo
dc.subject.enpl
galaxies: individual: NGC 6946
dc.subject.enpl
galaxies: ISM
dc.subject.enpl
galaxies: spiral
dc.subject.enpl
galaxies: magnetic fields
dc.subtypepl
Article
dc.titlepl
Hot gas and magnetic arms of NGC 6946 : indications for reconnection heating?
dc.title.journalpl
Astronomy & Astrophysics
dc.typepl
JournalArticle
dspace.entity.type
Publication
Affiliations

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