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1481. Rotational spectroscopy of CH_2_OH
ID:
ivo://CDS.VizieR/J/A+A/644/A123
Title:
Rotational spectroscopy of CH_2_OH
Short Name:
J/A+A/644/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
The hydroxymethyl radical (CH_2_OH) is one of the two structural isomers, together with the methoxy radical (CH_3_O), that can be produced by abstraction of a hydrogen atom from methanol (CH_3_OH). In the interstellar medium (ISM), both CH_2_OH and CH_3_O are suspected to be intermediate species in many chemical reactions, including those of formation and destruction of methanol. The determination of the CH_3_O/CH_2_OH ratio in the ISM would bring important information concerning the formation processes of these species in the gas and solid phases. Interestingly, only CH_3_O has been detected in the ISM so far, despite the recent first laboratory measurement of the CH_2_OH rotation-tunneling spectrum. This lack of detection is possibly due to the non-observation in the laboratory of the most intense rotational-tunneling transitions at low temperature. To support further searches for the hydroxymethyl radical in space, we have performed a thorough spectroscopic study of its rotation-tunneling spectrum, with particular focus on transitions involving the lowest quantum numbers of the species. We have recorded the rotation-tunneling spectrum of CH_2_OH at room temperature in the millimeter-wave domain using a frequency multiplication chain spectrometer associated to a fluorine-induced H-abstraction method. The radical was produced from methanol precursor. About 180 transitions were observed including those involving the lowest N and Ka quantum numbers, predicted intense under cold astrophysical conditions. These transitions were fitted together with available millimeter-wave lines from the literature. The systematic observation of all components of the rotational transitions yields a large improvement of the spectroscopic parameters which now allow confident searches of the hydroxymethyl radical in cold to warm environments of the ISM.
1482. Rotational spectrum of HCOO^13^CH_3_
ID:
ivo://CDS.VizieR/J/A+A/500/1109
Title:
Rotational spectrum of HCOO^13^CH_3_
Short Name:
J/A+A/500/1109
Date:
21 Oct 2021
Publisher:
CDS
Description:
Laboratory measurements and analysis of the microwave and millimeter-wave spectra of potential interstellar molecules are a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis provides spectroscopic parameters that are used in the assignment procedure of the laboratory spectra, and that also predict the frequencies of transitions not measured in the laboratory with a high degree of precision. An experimental laboratory study and its theoretical analysis is presented for ^13^C_2_-methyl formate (HCOO^13^CH_3_) allowing a search for this isotopologue in the Orion molecular cloud. The ^13^C_1_-methyl formate (H^13^COOCH_3_) molecule was also searched for in this interstellar cloud, using previously published spectroscopic data.
1483. Rotation measure image of the sky
ID:
ivo://CDS.VizieR/J/ApJ/702/1230
Title:
Rotation measure image of the sky
Short Name:
J/ApJ/702/1230
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have re-analyzed the NRAO VLA Sky Survey (NVSS) data to derive rotation measures (RMs) toward 37543 polarized radio sources. The resulting catalog of RM values covers the sky area north of declination -40{deg} with an average density of more than one RM per square degree. We have identified five regions of the sky where the foreground median RM is consistently less than 1rad/m^2^ over several degrees. These holes in the foreground RM will be useful for future studies of possible small-scale fluctuations in cosmic magnetic field structures. In addition to allowing measurement of RMs toward polarized sources, the new analysis of the NVSS data removes the effects of bandwidth depolarization for |RM|>~100rad/m^2^ inherent in the original NVSS source catalog.
1484. Rotation measures in A2255 at 18, 21, 25, 85cm
ID:
ivo://CDS.VizieR/J/other/JApA/32.567
Title:
Rotation measures in A2255 at 18, 21, 25, 85cm
Short Name:
J/other/JApA/32.
Date:
21 Oct 2021
Publisher:
CDS
Description:
Polarized radio emission is detected at various scales in the Universe. In this document, I will briefly review our knowledge on polarized radio sources in galaxy clusters and at their outskirts, emphasizing the crucial information provided by the polarized signal on the origin and evolution of such sources. Successively, I will focus on Abell 2255, which is known in the literature as the first cluster for which filamentary polarized emission associated with the radio halo has been detected. By using RM (plasma Rotation Measure) synthesis on our multi-wavelength WSRT observations, we studied the 3-dimensional geometry of the cluster, unveiling the nature of the polarized filaments at the borders of the central radio halo. Our analysis points out that these structures are relics lying at large distance from the cluster center.
1485. Rotation measures in radio source pairs
ID:
ivo://CDS.VizieR/J/ApJ/878/92
Title:
Rotation measures in radio source pairs
Short Name:
J/ApJ/878/92
Date:
03 Mar 2022 08:14:01
Publisher:
CDS
Description:
Faraday rotation measures (RMs) of extragalactic radio sources provide information on line-of-sight magnetic fields, including contributions from our Galaxy, source environments, and the intergalactic medium (IGM). Looking at differences in RMs, {Delta}RM, between adjacent sources on the sky can help isolate these different components. In this work, we classify adjacent polarized sources in the NRAO VLA Sky Survey (NVSS) as random or physical pairs. We recompute and correct the uncertainties in the NVSS RM catalog, since these were significantly overestimated. Our sample contains 317 physical and 5111 random pairs, all with Galactic latitudes |b|>=20{deg}, polarization fractions >=2%, and angular separations between 1.5' and 20'. We find an rms {Delta}RM of 14.9+/-0.4 and 4.6+/-1.1rad/m^2^ for the random and physical pairs, respectively. This means that polarized extragalactic sources that are close on the sky but at different redshifts have larger differences in RM than two components of one source. This difference of ~10rad/m^2^ is significant at 5{sigma} and persists in different data subsamples. While there have been other statistical studies of {Delta}RM between adjacent polarized sources, this is the first unambiguous demonstration that some of this RM difference must be extragalactic, thereby providing a firm upper limit on the RM contribution of the IGM. If the {Delta}RMs originate local to the sources, then the local magnetic field difference between random sources is a factor of 2 larger than that between components of one source. Alternatively, attributing the difference in {Delta}RMs to the intervening IGM yields an upper limit on the IGM magnetic field strength of 40nG.
1486. Rotation measures of extragalactic radio sources
ID:
ivo://CDS.VizieR/J/ApJ/755/21
Title:
Rotation measures of extragalactic radio sources
Short Name:
J/ApJ/755/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100{deg}-117{deg}, within 30{deg} of the Galactic plane. For |b|<15{deg}, we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15{deg}<|b|<30{deg}, we find median RMs of -15+/-4rad/m2 and -62+/-5rad/m2 in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2{mu}G (7{mu}G) at a height 0.8-2kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.
1487. Rotation measures of extragalactic sources in SGPS
ID:
ivo://CDS.VizieR/J/ApJ/663/258
Title:
Rotation measures of extragalactic sources in SGPS
Short Name:
J/ApJ/663/258
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253{deg}<=l<=356{deg}, |b|<=1.5{deg}), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius-Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms.
1488. Rotation measures of radio point sources
ID:
ivo://CDS.VizieR/J/other/RAA/14.942
Title:
Rotation measures of radio point sources
Short Name:
J/other/RAA/14.9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We compiled a catalog of Faraday rotation measures (RMs) for 4553 extragalactic radio point sources published in literature. These RMs were derived from multi-frequency polarization observations. The RM data are compared to those in the NRAO VLA Sky Survey (NVSS) RM catalog. We reveal a systematic uncertainty of about 10.0+/-1.5rad/m^2^ in the NVSS RM catalog. The Galactic foreground RM is calculated through a weighted averaging method by using the compiled RM catalog together with the NVSS RM catalog, with careful consideration of uncertainties in the RM data. The data from the catalog and the interface for the Galactic foreground RM calculations are publicly available on the webpage: http://zmtt.bao.ac.cn/RM/ .
1489. Rotation Measure synthesis of WSRT obs.
ID:
ivo://CDS.VizieR/J/A+A/549/A56
Title:
Rotation Measure synthesis of WSRT obs.
Short Name:
J/A+A/549/A56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rotation Measure synthesis (RM synthesis) of the Westerbork Synthesis Radio Telescope (WSRT) observations at 2m wavelength of the FAN region at l=137deg, b=+7deg shows the morphology of structures in the ionized interstellar medium.
1490. Rotation reversals in the polarization in OJ 287
ID:
ivo://CDS.VizieR/J/ApJ/862/1
Title:
Rotation reversals in the polarization in OJ 287
Short Name:
J/ApJ/862/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained a smooth time series for the electric vector position angle (EVPA) of the blazar OJ 287 at centimeter wavelengths, by making +/-n{pi} adjustments to archival values from 1974 to 2016. The data display rotation reversals in which the EVPA rotates counterclockwise for ~180{deg} and then rotates clockwise by a similar amount. The timescale of the rotations is a few weeks to a year, and the scale for a double rotation, including the reversal, is 1-3yr. We have seen four of these events in 40yr. A model consisting of two successive outbursts in polarized flux density, with EVPAs counterrotating, superposed on a steady polarized jet, can explain many of the details of the observations. Polarization images support this interpretation. The model can also help to explain similar events seen at optical wavelengths. The outbursts needed for the model can be generated by the supermagnetosonic jet model of Nakamura+ (2010ApJ...721.1783N) and Nakamura & Meier (2014ApJ...785..152N), which requires a strong helical magnetic field. This model produces forward and reverse pairs of fast and slow MHD waves, and the plasma inside the two fast/slow pairs rotates around the jet axis, but in opposite directions.