skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH)

Abstract

We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam{sup −1} maser centered at an LSR velocity of 0.83 km s{sup −1}, we find a 20- σ detection of zB {sub los} = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ∼ 10{sup 7–8} cm{sup −3}, then the B versus n {sup 1/2} relation would imply, from comparison with Zeeman effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ∼10 mG. Combined with our detected zB {sub los} = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ∼5 Hz mG{sup −1}. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H{sub 2}O. Empirical attempts to determine z , as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH{sub 3}OH transition. Data from observations of a larger number of sources are needed to make such empiricalmore » determinations robust.« less

Authors:
 [1];  [2]
  1. National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
  2. Physics Department, DePaul University, 2219 N. Kenmore Avenue, Byrne Hall 211, Chicago, IL 60614 (United States)
Publication Date:
OSTI Identifier:
22663987
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 834; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BEAMS; CARBON NITRIDES; COMPARATIVE EVALUATIONS; COSMIC RADIATION; DETECTION; GHZ RANGE; MAGNETIC FIELDS; MASERS; METHANOL; MOLECULES; PARAMAGNETISM; POLARIZATION; STARS; VELOCITY; WATER; ZEEMAN EFFECT

Citation Formats

Momjian, E., and Sarma, A. P., E-mail: emomjian@nrao.edu, E-mail: asarma@depaul.edu. THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH). United States: N. p., 2017. Web. doi:10.3847/1538-4357/834/2/168.
Momjian, E., & Sarma, A. P., E-mail: emomjian@nrao.edu, E-mail: asarma@depaul.edu. THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH). United States. doi:10.3847/1538-4357/834/2/168.
Momjian, E., and Sarma, A. P., E-mail: emomjian@nrao.edu, E-mail: asarma@depaul.edu. Tue . "THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH)". United States. doi:10.3847/1538-4357/834/2/168.
@article{osti_22663987,
title = {THE ZEEMAN EFFECT IN THE 44 GHZ CLASS I METHANOL MASER LINE TOWARD DR21(OH)},
author = {Momjian, E. and Sarma, A. P., E-mail: emomjian@nrao.edu, E-mail: asarma@depaul.edu},
abstractNote = {We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam{sup −1} maser centered at an LSR velocity of 0.83 km s{sup −1}, we find a 20- σ detection of zB {sub los} = 53.5 ± 2.7 Hz. If 44 GHz methanol masers are excited at n ∼ 10{sup 7–8} cm{sup −3}, then the B versus n {sup 1/2} relation would imply, from comparison with Zeeman effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ∼10 mG. Combined with our detected zB {sub los} = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ∼5 Hz mG{sup −1}. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H{sub 2}O. Empirical attempts to determine z , as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH{sub 3}OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.},
doi = {10.3847/1538-4357/834/2/168},
journal = {Astrophysical Journal},
number = 2,
volume = 834,
place = {United States},
year = {Tue Jan 10 00:00:00 EST 2017},
month = {Tue Jan 10 00:00:00 EST 2017}
}
  • We report the discovery of the Zeeman effect in the 44 GHz Class I methanol (CH{sub 3}OH) maser line. The observations were carried out with 22 antennas of the Expanded Very Large Array toward a star-forming region in OMC-2. Based on our adopted Zeeman splitting factor of z = 1.0 Hz mG{sup -1}, we detect a line-of-sight magnetic field of 18.4 {+-} 1.1 mG toward this source. Since such 44 GHz CH{sub 3}OH masers arise from shocks in the outflows of star-forming regions, we can relate our measurement of the post-shock magnetic field to field strengths indicated by species tracingmore » pre-shock regions, and thus characterize the large-scale magnetic field. Moreover, since Class I masers trace regions more remote from the star-forming core than Class II masers, and possibly earlier phases, magnetic fields detected in 6.7 GHz Class II and 36 and 44 GHz Class I methanol maser lines together offer the potential of providing a more complete picture of the magnetic field. This motivates further observations at high angular resolution to find the positional relationships between Class I and Class II masers, and masers at various frequencies within each category. In particular, CH{sub 3}OH masers are widespread in high- as well as intermediate-mass star-forming regions, and our discovery provides a new method of studying the magnetic field in such regions, by observing small physical scales that are not accessible by any other lines.« less
  • We present a second epoch of observations of the 44 GHz Class I methanol maser line toward the star-forming region Orion Molecular Cloud 2. The observations were carried out with the Very Large Array, and constitute one of the first successful Zeeman effect detections with the new Wide-band Digital Architecture correlator. Comparing to the result of our earlier epoch of data for this region, we find that the intensity of the maser increased by 50%, but the magnetic field value has stayed the same, within the errors. This suggests that the methanol maser may be tracing the large-scale magnetic fieldmore » that is not affected by the bulk gas motions or turbulence on smaller scales that is causing the change in maser intensity.« less
  • We report the first detection of the Zeeman effect in the 36 GHz Class I CH{sub 3}OH maser line. The observations were carried out with 13 antennas of the EVLA toward the high mass star-forming region M8E. Based on our adopted Zeeman splitting factor of z = 1.7 Hz mG{sup -1}, we detect a line-of-sight magnetic field of -31.3 +- 3.5 mG and 20.2 +- 3.5 mG to the northwest and southeast of the maser line peak, respectively. This change in sign over a 1300 AU size scale may indicate that the masers are tracing two regions with different fields,more » or that the same field curves across the regions where the masers are being excited. The detected fields are not significantly different from the magnetic fields detected in the 6.7 GHz Class II CH{sub 3}OH maser line, indicating that CH{sub 3}OH masers may trace the large-scale magnetic field, or that the magnetic field remains unchanged during the early evolution of star-forming regions. Given what is known about the densities at which 36 GHz CH{sub 3}OH masers are excited, we find that the magnetic field is dynamically significant in the star-forming region.« less
  • We report on a large 44 GHz (7{sub 0}–6{sub 1} A {sup +}) methanol (CH{sub 3}OH) maser survey of the Galactic Center. The Karl G. Jansky Very Large Array was used to search for CH{sub 3}OH maser emission covering a large fraction of the region around Sgr A. In 25 pointings, over 300 CH{sub 3}OH maser sources (>10 σ ) were detected. The majority of the maser sources have a single peak emission spectrum with line of sight velocities that range from about −13 to 72 km s{sup −1}. Most maser sources were found to have velocities around 35−55 kmmore » s{sup −1}, closely following velocities of neighboring interacting molecular clouds (MCs). The full width at half-maximum of each individual spectral feature is very narrow (∼0.85 km s{sup −1} on average). In the north, where Sgr A East is known to be interacting with the 50 km s{sup −1} MC, more than 100 44 GHz CH{sub 3}OH masers were detected. In addition, three other distinct concentrations of masers were found, which appear to be located closer to the interior of the interacting MCs. It is possible that a subset of masers is associated with star formation, although conclusive evidence is lacking.« less
  • We report the results of a systematic survey for 95 GHz class I methanol masers toward a new sample of 192 massive young stellar object candidates associated with ongoing outflows (known as extended green objects or EGOs) identified from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The observations were made with the Australia Telescope National Facility (ATNF) Mopra 22 m radio telescope and resulted in the detection of 105 new 95 GHz class I methanol masers. For 92 of the sources our observations provide the first identification of a class I maser transition associated with these objectsmore » (i.e., they are new class I methanol maser sources). Our survey proves that there is indeed a high detection rate (55%) of class I methanol masers toward EGOs. Comparison of the GLIMPSE point sources associated with EGOs with and without class I methanol maser detections shows that they have similar mid-IR colors, with the majority meeting the color selection criteria -0.6 < [5.8]-[8.0] < 1.4 and 0.5 < [3.6]-[4.5] < 4.0. Investigations of the Infrared Array Camera and Multiband Imaging Photometer for Spitzer 24 {mu}m colors and the associated millimeter dust clump properties (mass and density) of the EGOs for the sub-samples based on the class of methanol masers they are associated with suggest that the stellar mass range associated with class I methanol masers extends to lower masses than for class II methanol masers, or alternatively class I methanol masers may be associated with more than one evolutionary phase during the formation of a high-mass star.« less