Measuring the Magnetic Field Strength in L1498 with Zeeman‐splitting Observations of CCS

Levin, S. M.; Langer, W. D.; Velusamy, T.; Kuiper, T. B. H.; Crutcher, R. M.

doi:10.1086/321518

Cited by 34 publications

(32 citation statements)

References 11 publications

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“…These values are consistent with the measurements of magnetic field strength in cores in Taurus in dense material (10 4 − 10 5 cm −3 ) traced by CCS emission: from 48 ± 31 µG in L1498 (Levin et al 2001) to 160 ± 42 µG in L1521E (Shinnaga et al 1999). We further estimated the ratio Ω m,vir /2Ω k , in order to determine whether, if our cores were virialised, the dominant mechanism for internal support would be magnetic energy or internal kinetic energy.…”

Section: Virial Balancesupporting

confidence: 91%

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Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Pattle¹

2017

Springer Theses

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Section: Virial Balancesupporting

confidence: 91%

“…Levin et al 2001;Kirk et al 2006;Troland & Crutcher 2008). It should be noted that no single observational technique can probe more than one component (either line-of-sight or plane-of-sky) of the magnetic field strength at a time.…”

Section: Magnetic Fieldsmentioning

confidence: 99%

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Pattle¹

2017

Springer Theses

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“…Dense molecular cores have weak magnetic fields with typical strengths of B ∼ 10 μG or less (Crutcher et al 2010). For example, CCS Zeeman observations of L1498 set an upper limit on B = 48 ± 31 μG for the line-of-sight component of the magnetic field (Levin et al 2001). The line shapes can be sensitive to random motions at the Alfvén velocity associated with the magnetic field B, v A = B/ 4πρ.…”

Section: Zeeman Effect Induced By Static Magnetic Fieldsmentioning

confidence: 99%

Searching for chameleon-like scalar fields with the ammonia method

Levshakov

Lapinov

Henkel

et al. 2010

A&A

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Context. In our previous work we found a statistically significant offset ΔV ≈ 27 m s −1 between the radial velocities of the HC 3 N J = 2−1 and NH 3 (J, K) = (1, 1) transitions observed in molecular cores from the Milky Way. This may indicate that the electron-toproton mass ratio, μ ≡ m e /m p , increases by ∼3 × 10 −8 when measured under interstellar conditions with matter densities of more than 10 orders of magnitude lower than with laboratory (terrestrial) environments. Aims. We map four molecular cores L1498, L1512, L1517, and L1400K selected from our previous sample to estimate systematic effects in ΔV due to possible velocity gradients or other sources across the cloud and to check the reproducibility of the velocity offsets on the year-to-year time base. Methods. We use the ammonia method, which involves observations of inversion lines of NH 3 complemented by rotational lines of other molecular species and allows us to test changes in μ caused by a higher sensitivity of the inversion frequencies to the μ-variation than with the rotational frequencies. Results. We find that in two cores L1498 and L1512 the NH 3 (1, 1) and HC 3 N (2-1) transitions closely trace the same material and show an offset of ΔV ≡ V lsr (HC 3 N) -V lsr (NH 3 ) = 26.9 ± 1.2 stat ± 3.0 sys m s −1 throughout the entire clouds. The offsets measured in L1517B and L1400K are 46.9 ± 3.3 stat ± 3.0 sys m s −1 and 8.5 ± 3.4 stat ± 3.0 sys m s −1 , respectively, and are, probably, subject to Doppler shifts due to spatial segregation of HC 3 N versus NH 3 . We also determine frequency shifts caused by external electric and magnetic fields and by the cosmic black body radiation-induced Stark effect and find that they are less than 1 m s −1 . Conclusions. The measured velocity offset in L1498 and L1512, when interpreted in terms of Δμ/μ ≡ (μ obs − μ lab )/μ lab , gives Δμ/μ = (26 ± 1 stat ± 3 sys ) × 10 −9 . Although this estimate is based on a limited number of sources and molecular pairs used in the ammonia method, it demonstrates a high accuracy with which the fundamental physics can be tested by means of radio observations. The non-zero signal in Δμ/μ should be further examined as larger and more accurate data sets become available.

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“…The VLA and VLBA have been used to study the Zeeman effect in water masers (Sarma et al 2001). More recently attempts to detect the Zeeman effect in a variety of lines have been made: the H30α recombination line by Thum and Morris (1999), the CN line by Crutcher et al (1999), and the CCS line by Levin et al (2001). Note that OH and H 2 O masers arise in very small regions in high-density clouds under special conditions.…”

Section: The Zeeman Effectmentioning

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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Measuring the Magnetic Field Strength in L1498 with Zeeman‐splitting Observations of CCS

Cited by 34 publications

References 11 publications

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Submillimetre Studies of Prestellar and Starless Cores in the Ophiuchus, Taurus and Cepheus Molecular Clouds

Searching for chameleon-like scalar fields with the ammonia method

Milestones in the Observations of Cosmic Magnetic Fields

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