The nature of nonthermal X-ray filaments near the galactic center

Yusef‐Zadeh, F.; Wardle, Mark; Muno, M. P.; Law, Casey J.; Pound, Marc W.

doi:10.1016/j.asr.2005.02.057

Cited by 31 publications

(58 citation statements)

References 21 publications

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“…There is some suggestion in the slice analysis that the spectral index is flatter in the fainter portions near the northern and southern ends of C3. The integrated spectral index was measured previously between 90 and 20 cm as À0:8 AE 0:1 (Anantharamaiah et al 1991) and 20 and 6 cm as $À0.8 (Yusef-Zadeh et al 2005), consistent with the present slice analysis. However, the integrated spectral index between 6 and 3.6 cm steepens significantly to $À2 (Yusef-Zadeh et al 2005).…”

Section: G35954+018 (Rf-c3supporting

confidence: 73%

“…The integrated spectral index was measured previously between 90 and 20 cm as À0:8 AE 0:1 (Anantharamaiah et al 1991) and 20 and 6 cm as $À0.8 (Yusef-Zadeh et al 2005), consistent with the present slice analysis. However, the integrated spectral index between 6 and 3.6 cm steepens significantly to $À2 (Yusef-Zadeh et al 2005). Figure 9 shows a clear 6 cm polarized counterpart to RF-C3, as had been noted before (Bally & Yusef-Zadeh 1989;YusefZadeh et al 1997).…”

Section: G35954+018 (Rf-c3supporting

confidence: 73%

“…Synchrotron cooling preferentially reduces the flux at higher frequencies, breaking the spectrum at a frequency b / B À3 t À2 (Blundell & Rawlings 2000). Several filaments have been observed with steeper spectral indices at higher frequencies ( Lang et al 1999b;LaRosa et al 2001;Yusef-Zadeh et al 2005), which is commonly attributed to synchrotron cooling of filament as a whole. This model can also explain the spectral index spatial gradients if electrons propagate from a single acceleration region; the steeper spectral indices are interpreted as being further from the acceleration region.…”

Section: Unusual Filamentsmentioning

confidence: 99%

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A Wide‐Area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths

Law

Yusef‐Zadeh

Cotton

2008

ASTROPHYS J SUPPL S

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We describe the results of a millijansky sensitivity VLA survey of roughly 1 deg 2 near the Galactic center at 6 and 20 cm. Catalogs of compact and filamentary structures are given and compared to previous surveys of the region. Eight of the unusual nonthermal radio filaments are detected in 6 cm polarized emission; three of these are the first such detections, confirming their nonthermal nature. This survey found emission from a filament at (l; b) ¼ (359:1; 0:75), or a projected distance from Sgr A Ã of 200 pc, greatly extending the latitude range observed with such features. There is also new evidence for spatial gradients in the 6/20 cm spectral indices of some filaments, and we discuss models for these gradients. In studying compact sources, the combination of spectral index and polarization information allows us to identify pulsar candidates and compact H ii regions in the survey. There is also some evidence that the flux measurements of compact sources may be affected by electron scattering from the interstellar medium in the central few hundred parsecs of the Galaxy.

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Section: G35954+018 (Rf-c3supporting

confidence: 73%

Section: G35954+018 (Rf-c3supporting

confidence: 73%

Section: Unusual Filamentsmentioning

confidence: 99%

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A Wide‐Area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths

Law

Yusef‐Zadeh

Cotton

2008

ASTROPHYS J SUPPL S

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“…Yusef-Zadeh et al (2005) detected X-ray emission from the radio filament G359.90−0.06, which they tentatively attributed to inverse Compton scattering of far-infrared photons from dust by the relativistic electrons that produce the radio synchrotron emission. Relying on dust thermal emission observations to constrain the dust parameters, they were able to infer the relativistic-electron density from the X-ray flux and then the magnetic field strength from the radio synchrotron flux.…”

Section: Radio Continuum Observationsmentioning

confidence: 99%

Interstellar magnetic fields in the Galactic center region

Ferrière¹

2009

A&A

104

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Aims. We seek to obtain a picture of the interstellar magnetic field in the Galactic center region that is as clear and complete as possible. Methods. We review the observational knowledge that has built up over the past 25 years on interstellar magnetic fields within ∼200 pc of the Galactic center. We then critically discuss the various theoretical interpretations and scenarios proposed to explain the existing observations. We also study the possible connections with the general Galactic magnetic field and describe the observational situation in external galaxies. Results. We propose a coherent picture of the magnetic field near the Galactic center, which reconciles some of the seemingly divergent views and which best accounts for the vast body of observations. Our main conclusions are the following. In the diffuse intercloud medium, the large-scale magnetic field is approximately poloidal and its value is generally close to equipartition with cosmic rays (∼10 μG), except in localized filaments where the field strength can reach ∼1 mG. In dense interstellar clouds, the magnetic field is approximately horizontal and its value is typically ∼1 mG.

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“…Yusef-Zadeh & Morris (1987b) noted that they are parts of large-scale "semicircular features". The radio and X-ray emission properties of sources E (G359.88-0.08) and F (G359.90-0.06) were examined in detail by Yusef-Zadeh et al (2005). Our new 6cm image (Fig.…”

Section: The "Curls" -Strongly Deformed Ntfsmentioning

confidence: 99%

Nonthermal filamentary radio features within 20 pc of the Galactic center

Morris¹,

Zhao

Goss³

2013

Proc. IAU

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Abstract. Deep imaging of the Sgr A complex at 6 cm wavelength with the B and C configurations of the Karl G. Jansky VLA † has revealed a new population of faint radio filaments. Like their brighter counterparts that have been observed throughout the Galactic Center on larger scales, these filaments can extend up to ∼10 parsecs, and in most cases are strikingly uniform in brightness and curvature. Comparison with a survey of Paschen-α emission reveals that some of the filaments are emitting thermally, but most of these structures are nonthermal: local magnetic flux tubes illuminated by synchrotron emission. The new image reveals considerable filamentary substructure in previously known nonthermal filaments (NTFs). Unlike NTFs previously observed on larger scales, which tend to show a predominant orientation roughly perpendicular to the Galactic plane, the NTFs in the vicinity of the Sgr A complex are relatively randomly oriented. Two well-known radio sources to the south of Sgr A -sources E and F -consist of numerous quasi-parallel filaments that now appear to be particularly bright portions of a much larger, strongly curved, continuous, nonthermal radio structure that we refer to as the Southern Curl. It is therefore unlikely that sources E and F are HII regions or pulsar wind nebulae. The Southern Curl has a smaller counterpart on the opposite side of the Galactic Center -the Northern Curl -that, except for its smaller scale and smaller distance from the center, is roughly point-reflection symmetric with respect to the Southern Curl. The curl features indicate that some field lines are strongly distorted, presumably by mass flows. The point symmetry about the center then suggests that the flows originate near the center and are somewhat collimated.

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The nature of nonthermal X-ray filaments near the galactic center

Cited by 31 publications

References 21 publications

A Wide‐Area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths

A Wide‐Area VLA Continuum Survey near the Galactic Center at 6 and 20 cm Wavelengths

Interstellar magnetic fields in the Galactic center region

Nonthermal filamentary radio features within 20 pc of the Galactic center

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