The magnetic field along the jets of NGC 4258

Krause, M.; Lohr, Andreas

doi:10.1051/0004-6361:20034165

Cited by 24 publications

(26 citation statements)

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“…Cecil et al (2000) claimed to have Herrnstein et al (1999); (3) van Albada (1980); (4) Miyoshi et al (1995); (5) Cecil et al (2000); (6) Krause & Löhr (2004); (7) this paper; (8) β is the angle between the nuclear jet axis and the rotational axis of the galaxy as discussed in Sect. 4.2 adopting the warped disk model by Herrnstein et al (2005) with a central disk inclination of 74…”

Section: Molecular Gas (mentioning

confidence: 92%

“…The interpretation of these two radio sources as being hot spots is, however, still under debate as the northern one has been classified as SNR candidate by Hyman et al (2001); Krause & Löhr (2004) detected linear polarization in the northern one but not in the southern. The first reliable single-dish observations with enough angular resolution to resolve the 12 CO(1-0) emission of NGC 4258 had been carried out with the 30-m IRAM telescope at Pico Veleta (Krause et al 1990).…”

Section: Molecular Gas (mentioning

confidence: 99%

“…Recent radio continuum observations revealed a total magnetic field strength of about 300 µG in the northern jet at about 5 kpc distance from the nucleus (with a linear resolution of about 100 pc) (Krause & Löhr 2004). This value is much higher than the usual field strengths measured in spiral galaxies (1-50 µG), but agrees surprisingly well with the above estimate in Eq.…”

Section: The Jet Magnetic Fieldmentioning

confidence: 99%

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Magnetic interaction of jets and molecular clouds in NGC 4258

Krause

Fendt

Neininger

2007

A&A

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Context. NGC 4258 is a well known spiral galaxy with a peculiar large scale jet flow detected in the radio and in Hα. Due to the special geometry of the galaxy, the jets emerge from the nuclear region through the galactic disk -at least in the inner region. Aims. Also the distribution of molecular gas looks different from that in other spiral galaxies:12 CO(1-0) emission has only been detected in the center and along the jets and only up to distances of about 50 (1.8 kpc) from the nucleus. This concentration of CO along the jets is similar to what is expected as fuel for jet-induced star formation in more distant objects. The reason for the CO concentration along the inner jets in NGC 4258 was not understood and is the motivation for the observations presented here. Methods. Using the IRAM interferometer at Plateau de Bure, we mapped the 12 CO(1-0) emission of the central part of NGC 4258 along the nuclear jet direction in the inner 3 kpc. In order to get a properly positioned overlay with Hα we observed NGC 4258 in Hα at the Hoher List Observatory of the University of Bonn. Results. We detected two parallel CO ridges along a position angle of −25• with a total length of about 80 (2.8 kpc), separated by a CO depleted funnel with a width of about 5 (175 pc). The Hα emission is more extended and broader than the CO emission with its maximum just in between the two CO ridges. It seems to be mixed in location and in velocity with the CO emission. In CO we see a peculiar velocity distribution in the iso-velocity map and p-v diagrams. We discuss different scenarios for an interpretation and present a model which can explain the observational results consistently. Conclusions. We propose here that the concentration of CO along the ridges is due to interaction of the rotating gas clouds with the jet's magnetic field by ambipolar diffusion (ion-neutral drift). This magnetic interaction is thought to increase the time the molecular clouds reside near the jet thus leading to the quasi-static CO ridge.

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Section: Molecular Gas (mentioning

confidence: 92%

Section: Molecular Gas (mentioning

confidence: 99%

Section: The Jet Magnetic Fieldmentioning

confidence: 99%

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Magnetic interaction of jets and molecular clouds in NGC 4258

Krause

Fendt

Neininger

2007

A&A

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“…Disk galaxies with such jets are even less common. In fact, the only examples of 15 kpc scale anomalous radio arms or double-sided radio jets in disk galaxies in the nearby universe are in NGC 4258 (e.g., Hummel et al 1989;Krause & Löhr 2004) and NGC 7479 (Laine & Gottesman 1998). The radio jet in NGC 4258 is detected out to about 14 kpc radius and is of spiral form, trailing with respect to the galaxy rotation.…”

Section: Introductionmentioning

confidence: 99%

Radio Continuum Jet in NGC 7479

Laine

Beck

2008

ApJ

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The barred galaxy NGC 7479 hosts a remarkable jetlike radio continuum feature: bright, 12 kpc long in projection, and hosting an aligned magnetic field. The degree of polarization is 6% Y8% along the jet and remarkably constant, which is consistent with helical field models. The radio brightness of the jet suggests strong interaction with the ISM and hence a location near the disk plane. We observed NGC 7479 at four wavelengths with the VLA and Effelsberg radio telescopes. The equipartition strength is 35Y40 G for the total and !10 G for the ordered magnetic field in the jet. The jet acts as a bright, polarized background. Faraday rotation between 3.5 and 6 cm and depolarization between 6 and 22 cm can be explained by magnetoionic gas in front of the jet, with thermal electron densities of '0.06 cm À3 in the bar and '0.03 cm À3 outside the bar. The regular magnetic field along the bar points toward the nucleus on both sides. The regular field in the disk reveals multiple reversals, probably consisting of field loops stretched by a shearing gas flow in the bar. The projection of the jet bending in the sky plane is in the sense opposite to that of the underlying stellar and gaseous spiral structure. The bending in 3D is most easily explained as a precessing jet, with an age less than 10 6 yr. Our observations are consistent with very recent triggering, possibly by a minor merger. NGC 7479 provides a unique opportunity to study interaction-triggered 15 kpc scale radio jets within a spiral galaxy.

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“…In the inner galaxy, the radio emission is clearly associated with jets, presumably related to the AGN activity associated with the supermassive black hole; however, at larger distances, the nature of the radio emission is not so clear (e.g. Krause & Löhr 2004, and references therein). A detailed discussion of this unusual galaxy is beyond the scope of this paper, and a proper discussion of the RC-FIR-CO correlations in this source would warrant a separate study.…”

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confidence: 99%

The molecular connection to the FIR-radio continuum correlation in galaxies

Murgia

Helfer

Ekers

et al. 2005

A&A

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Abstract.We have studied the relationships between the radio continuum (RC) and CO emission for a set of galaxies selected from the BIMA Survey of Nearby Galaxies. We find that the global CO-RC correlation is as tight as the global FIR-RC correlation for the 24 galaxies studied. Within 9 galaxies with ∼6 CO and RC data available, the CO and RC emission is as tightly correlated as its global value; the radially averaged correlation is nearly linear, extends over four order of magnitude and holds down to the smallest linear resolution of the observations, which is ∼100 pc. We define q CO/RC as the log of the ratio of the CO to RC flux as a way to characterize the CO-RC correlation. Combining 6 pixel-by-pixel comparisons across all sources yields an average small-scale correlation of q CO/RC = 1.1 ± 0.28; that is, the spatially resolved correlation has a dispersion that is less than a factor of 2. There are however systematic variations in the CO/RC ratio; the strongest organized structures in q CO/RC tend to be found along spiral arms and on size scales much larger than the resolution of the observations. We do not measure any systematic trend in CO/RC ratio as a function of radius in galaxies. The constancy of the CO/RC ratio stands in contrast to the previously measured decrease in the FIR/RC ratio as a function of radius in galaxies. We suggest that the excellent correlation between the CO, RC and FIR emission in galaxies is a consequence of regulation by hydrostatic pressure; this model links all three emissions without invoking an explicit dependence on a star formation scenario.

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The magnetic field along the jets of NGC 4258

Cited by 24 publications

References 24 publications

Magnetic interaction of jets and molecular clouds in NGC 4258

Magnetic interaction of jets and molecular clouds in NGC 4258

Radio Continuum Jet in NGC 7479

The molecular connection to the FIR-radio continuum correlation in galaxies

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