A new symmetrical polarization structure near the galactic centre

Seiradakis, J. H.; Lasenby, A. N.; Yusef‐Zadeh, F.; Wielebinski, R.; Klein, U.

doi:10.1038/317697a0

Cited by 80 publications

(41 citation statements)

References 6 publications

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“…On the other hand, a faint point-like structure at the shell center seen in Figure 2 is not significant because it contains only 3 photons. Unlike Sgr B2, no radio nor any other wave band counterpart is found for G0.570−0.018 (see Oka et al 1998aOka et al , 1998bTsuboi, Handa, & Ukita 1999;Lis, & Carlstrom 1994;Mehlinger et al 1992Mehlinger et al , 1993Seiradakis et al 1989). …”

Section: X-ray Morphologymentioning

confidence: 99%

Unusual Diffuse X‐Ray Source in the Galactic Center Region

Senda

Murakami

Koyama

2002

ApJ

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We report the ASCA and Chandra discovery of a diffuse X-ray source in the Galactic center region. The X-ray spectrum is fitted with a nonequilibrium ionization (NEI) plasma model of about 6-keV temperature. The model requires higher than solar metal abundances, a young plasma age of ≃ 100 years and a large N H value of about 10. The N H value constrains the source position to be in the Galactic center region at about 8.5 kpc distance. The high resolution X-ray image with the Chandra ACIS shows a ring of 10 ′′ radius which corresponds to 0.4 pc at the Galactic center, and a tail-like structure. Although the morphology is peculiar, the other X-ray features are likely to be a very young supernova remnant, possibly in a free expansion phase.

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Section: X-ray Morphologymentioning

confidence: 99%

Unusual Diffuse X‐Ray Source in the Galactic Center Region

Senda

Murakami

Koyama

2002

ApJ

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“…Most of these have been studied in great detail regarding the fine structure, polarization at several frequencies and hence the RMs and spectral indices examined. These strongly polarized nonthermal features are very narrow, with lengths of tens of pc but widths of less than 0.5 pc * (e.g., Inoue et al 1984;Seiradakis et al 1985;Tsuboi et al 1986;Haynes et al 1992). All but one are perpendicular to the Galactic plane (Lang et al 1999b).…”

Section: The Galactic Centermentioning

confidence: 99%

“…• on each side of the Galactic plane (Seiradakis et al 1985;Tsuboi et al 1986;Haynes et al 1992). Later, radio observations using both single dish radio telescopes (Effelsberg 100 m, Nobeyama 45 m) and large synthesis telescopes (VLA, MOST, ATCA), have revealed many filaments, arcs or loops, threads (e.g., Anantharamaiah et al 1991;LaRosa et al 2000LaRosa et al , 2001Lang et al 1999a, b), plumes (e.g., Duncan et al 1998) and lobes (Sofue 1985).…”

Section: The Galactic Centermentioning

confidence: 99%

Milestones in the Observations of Cosmic Magnetic Fields

Han

Wielebinski

2002

Chin. J. Astron. Astrophys.

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Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of extragalactic radio sources, the pulsar RMs, radio polarization observations, as well as the newly implemented sub-mm and mm polarization capabilities. The magnetic field of the Galaxy was first discovered in 1949 by optical polarization observations. The local magnetic fields within one or two kpc have been well delineated by starlight polarization data. The polarization observations of diffuse Galactic radio background emission in 1962 confirmed unequivocally the existence of a Galactic magnetic field. The bulk of the present information about the magnetic fields in the Galaxy comes from analysis of rotation measures of extragalactic radio sources and pulsars, which can be used to construct the 3-D magnetic field structure in the Galactic halo and Galactic disk. Radio synchrotron spurs in the Galactic center show a poloidal field, and the polarization mapping of dust emission and Zeeman observation in the central molecular zone reveal a toroidal magnetic field parallel to the Galactic plane. For nearby galaxies, both optical polarization and multifrequency radio polarization data clearly show the large-scale magnetic field following the spiral arms or dust lanes. For more distant objects, radio polarization is the only approach available to show the magnetic fields in the jets or lobes of radio galaxies or quasars. Clusters of galaxies also contain widely distributed magnetic fields, which are reflected by radio halos or the RM distribution of background objects. The intergalactic space could have been magnetized by outflows or galactic superwinds even in the early universe. The Zeeman effect and polarization of sub-mm and mm emission can be used for the study of magnetic fields in some Galactic molecular clouds but it is observed only at high intensity. Both approaches together can clearly show the role that magnetic fields play in star formation and cloud structure, which in principle would be analogous to galaxy formation from protogalactic clouds. The origin of the cosmic magnetic fields is an active field of research. A primordial magnetic field has not been as yet directly detected, but its ⋆

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“…Radio polarization observations at higher frequencies allowed investigations deeper in the Galaxy, showing that even at the Galactic centre continuum polarization can be observed (e.g. Seiradakis, Lasenby, Yusef-Zadeh, et al 1985). The northern sky was mapped in polarization by Wolleben, Landecker, Reich, et al (2006) and the southern sky by Testori, Reich & Reich (2008) both with good angular resolution.…”

Section: Radio Continuum Polarizationmentioning

confidence: 99%

What do we really know about the magnetic fields of the Milky Way?

Wielebinski

2008

Proc. IAU

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Abstract.We have several methods of measuring magnetic fields in the Milky Way. We can study optical polarization, radio polarization, rotation measures of pulsars and extragalactic radio sources as well as include Zeeman results. Each of the above mentioned methods was at times used to make a model of the magnetic fields of the Milky Way. However one or two of the data sets by themselves cannot tell us the whole story. Any model of the magnetic fields must be able to fit all the observational results. At the present time a lot of progress has been made. We have increased our data bases in most of the observational areas. However a robust model of the magnetic field of the Milky Way has not yet emerged. We must possibly wait to the era of SKA.

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A new symmetrical polarization structure near the galactic centre

Cited by 80 publications

References 6 publications

Unusual Diffuse X‐Ray Source in the Galactic Center Region

Unusual Diffuse X‐Ray Source in the Galactic Center Region

Milestones in the Observations of Cosmic Magnetic Fields

What do we really know about the magnetic fields of the Milky Way?

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