scholarly journals Revisiting the Distance to Radio Loops I and IV Using Gaia and Radio/Optical Polarization Data

2021 ◽  
Vol 922 (2) ◽  
pp. 210
Author(s):  
G. V. Panopoulou ◽  
C. Dickinson ◽  
A. C. S. Readhead ◽  
T. J. Pearson ◽  
M. W. Peel
Keyword(s):  
Magnetic Field ◽  
Galactic Center ◽  
Classical Method ◽  
Dust Emission ◽  
Galactic Latitude ◽  
Synchrotron Emission ◽  
Optical Polarization ◽  
The North ◽  
Significant Alignment ◽  
North Polar

Abstract Galactic synchrotron emission exhibits large angular scale features known as radio spurs and loops. Determining the physical size of these structures is important for understanding the local interstellar structure and for modeling the Galactic magnetic field. However, the distance to these structures is either under debate or entirely unknown. We revisit a classical method of finding the location of radio spurs by comparing optical polarization angles with those of synchrotron emission as a function of distance. We consider three tracers of the magnetic field: stellar polarization, polarized synchrotron radio emission, and polarized thermal dust emission. We employ archival measurements of optical starlight polarization and Gaia distances and construct a new map of polarized synchrotron emission from WMAP and Planck data. We confirm that synchrotron, dust emission, and stellar polarization angles all show a statistically significant alignment at high Galactic latitude. We obtain distance limits to three regions toward Loop I of 112 ± 17 pc, 135 ± 20 pc, and <105 pc. Our results strongly suggest that the polarized synchrotron emission toward the North Polar Spur at b > 30° is local. This is consistent with the conclusions of earlier work based on stellar polarization and extinction, but in stark contrast with the Galactic center origin recently revisited on the basis of X-ray data. We also obtain a distance measurement toward part of Loop IV (180 ± 15 pc) and find evidence that its synchrotron emission arises from chance overlap of structures located at different distances. Future optical polarization surveys will allow the expansion of this analysis to other radio spurs.

scholarly journals The Nature of the Galactic Center Arc

1996 ◽  
Vol 169 ◽  
pp. 263-269 ◽  
Author(s):  
E. Serabyn
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Galactic Center ◽  
Magnetic Energy ◽  
Linear Structure ◽  
High Energy ◽  
Molecular Gas ◽  
Synchrotron Emission ◽  
Interferometric Imaging ◽  
Relativistic Particles

Ever since the Galactic Center Arc was resolved into its component filaments a decade ago, it has been clear that its linear structure arises from the influence of a strong magnetic field. However, the origin and nature of the contributory phenomena have remained elusive. Since what is seen is synchrotron emission from relativistic particles, of prime interest is a knowledge of the acceleration mechanism involved. Interferometric imaging of the molecular gas in the vicinity of the Arc has now provided a tantalizing clue to the Arc's origin: molecular clumps coinciding with the endpoints of a number of the Arc's filaments point to these clumps as the source of the relativistic particles. This suggests that as dense molecular clumps course through the ambient magnetic field at the Galactic Center, magnetic energy is liberated in their leading layers via field reconnection, precipitating rapid acceleration of free charges to high energy.

scholarly journals HEAO-1 Diffuse Soft X-Ray Sky Maps

1984 ◽  
Vol 81 ◽  
pp. 219-221
Author(s):  
John A. Nousek ◽  
Gordon P. Garmire ◽  
George Weaver
Keyword(s):  
Galactic Center ◽  
Energy Interval ◽  
Background Intensity ◽  
X Ray ◽  
The North ◽  
Center Region ◽  
Local Emission ◽  
North Polar ◽  
X Ray Background

Maps of the diffuse soft X-ray background intensity are presented, spanning four energy intervals. The lowest energy interval (0.18-0.56 keV) is dominated by local emission, while the next two intervals (0.56-1.0 keV and 1.0-1.4 keV) reveal more distant and more sharply defined structures. Enlarged maps of several of these structures are presented, including the North Polar Spur, the Galactic Center region and the Eridanus Loop.

Double Stars with Common Proper Motion

1965 ◽  
Vol 5 ◽  
pp. 49-51
Author(s):  
Willem J. Luyten
Keyword(s):  
Proper Motion ◽  
Galactic Latitude ◽  
Schmidt Telescope ◽  
Polar Cap ◽  
Double Stars ◽  
The North ◽  
North Polar

The proper Motion Survey with the 48-in Schmidt telescope has now progressed far enough such that we may begin to make some meaningful statistical discussions of the results obtained. Altogether 135 regions have been blinked – one seventh of the total -and in particular all fifty plates covering the area of the North Polar Cap, north of declination +69 (1855) have been blinked and completely measured. This area covers 1360 square degrees, almost exactly one thirtieth of the entire sphere, and, since the galactic latitude of the Pole is 27°, and its distance from the ‘average’ solar apex is about 55° this region may be considered as not too unrepresentative for the whole sky.

scholarly journals Quantifying the Magnetic Alignment of Hi and Dust in the Diffuse ISM

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
S.E. Clark ◽  
J.E.G. Peek ◽  
J. Colin Hill ◽  
M.E. Putman
Keyword(s):  
Magnetic Field ◽  
Molecular Clouds ◽  
Dust Emission ◽  
Neutral Hydrogen ◽  
Magnetic Alignment ◽  
Galactic Latitude ◽  
Linear Features ◽  
Filamentary Structure ◽  
High Galactic Latitude ◽  
Vision Algorithm

AbstractSensitive, high resolution observations of Galactic neutral hydrogen (Hi) reveal an intricate network of slender linear features, much as sensitive surveys of dust in Galactic molecular clouds reveal ubiquitous filamentary structure. Across the high Galactic latitude sky, diffuse Histructures are aligned with the interstellar magnetic field, as revealed by background starlight polarization (Clark, Peek, & Putman 2014) and by Planck 353 GHz polarized dust emission (Clark et al. 2015). These discoveries were enabled by the Rolling Hough Transform, a recently developed, open source machine vision algorithm.

scholarly journals Detection of Synchrotron Emission from a Unique Herbig Haro Object in Orion

1990 ◽  
Vol 140 ◽  
pp. 329-330 ◽  
Author(s):  
F. Yusef-Zadeh ◽  
T. Cornwell ◽  
B. Reipurth ◽  
M. Roth
Keyword(s):  
Magnetic Field ◽  
Thermal Emission ◽  
Radio Continuum ◽  
Mass Star ◽  
Synchrotron Emission ◽  
Synchrotron Source ◽  
The Core ◽  
The North ◽  
Low Mass ◽  
Hh Object

We have obtained radio continuum observations of an HH object, known as the “streamer” in Orion using the VLA in a number of configurations at λ2, 6 and 20cm. This object is located several arc-minutes to the north of HH34 in L1641 cloud and exhibits a remarkably long and narrow structure with dimensions of 5′ × 10′ in optical photographs unlike the morphology of any other HH object. Based on radio continuum observations, we have detected a significant linearly polarized emission at λ6cm from the core of the streamer indicating highly uniform magnetic field geometry. This unusual result suggests that the source responsible for producing the nebulosity is a nonthermal-emitting radio source. Because of the presence of a number of newly born low-mass stars in L1641 and because of the detection of a highly reddened 2μm source coincident with the synchrotron source, it is likely that the source at the core of the streamer is a low-mass star responsible for the non-thermal emission and the HH nebulosity. Presence of synchrotron emission associated with a newly born star supports further view that the magnetic field plays a strong role in the early phase of star formation.

scholarly journals FARADAY TOMOGRAPHY OF THE NORTH POLAR SPUR: CONSTRAINTS ON THE DISTANCE TO THE SPUR AND ON THE MAGNETIC FIELD OF THE GALAXY

2015 ◽  
Vol 811 (1) ◽  
pp. 40 ◽  
Author(s):  
X. H. Sun ◽  
T. L. Landecker ◽  
B. M. Gaensler ◽  
E. Carretti ◽  
W. Reich ◽  
...  
Keyword(s):  
Magnetic Field ◽  
The North ◽  
The Galaxy ◽  
North Polar ◽  
The Magnetic Field

scholarly journals Structure of the Local Galactic Magnetic Field

1990 ◽  
Vol 140 ◽  
pp. 44-46
Author(s):  
R. J. Rand ◽  
S. R. Kulkarni
Keyword(s):  
Magnetic Field ◽  
Local Field ◽  
Galactic Magnetic Field ◽  
Concentric Ring ◽  
The North ◽  
Ring Model ◽  
North Polar ◽  
Spiral Model

We have modeled the local Galactic magnetic field using pulsar rotation measures (RMs), of which there are now about 200 available. The North Polar Spur has a significant effect on pulsar RMs. Using RMs of 116 pulsars nearer than 3 kpc, we find that the local field has a strength B0 = 1.6 ± 0.2 μG toward longitude lB =96° ± 4°, with a reversal of the field at a distance Dr = 600 ± 80 pc toward the inner Galaxy. Relaxing the 3 kpc distance restriction, we find that a concentric ring model with reversals is superior to a bisymmetric spiral model as a fit to the data.

scholarly journals A High-Resolution Polarization Survey of the North Polar Spur

1974 ◽  
Vol 60 ◽  
pp. 151-154
Author(s):  
G. Westerhout ◽  
D. Bechis
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
High Resolution ◽  
Polarization Distribution ◽  
The North ◽  
Angular Scale ◽  
North Polar ◽  
The Magnetic Field

Observations have been made at 21 cm with a resolution of 11′ to look for fine structure in the polarization distribution. In the North Polar Spur, the angular scale of the polarization parameters varies with latitude. This is attributed to an increase in the irregularity of the magnetic field in the Spur with latitude.

scholarly journals The Need for High Resolution for Polarization Studies of Galactic Background Radiation

1990 ◽  
Vol 140 ◽  
pp. 62-62
Author(s):  
G.L. Verschuur ◽  
T. A. Th. Spoelstra
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Background Radiation ◽  
Limited Data ◽  
Polarization Data ◽  
The North ◽  
Polarization Studies ◽  
North Polar ◽  
Galactic Background ◽  
Scale Length

Polarization data at 390 and 826 MHz were obtained with the 300-foot telescope in February 1987. A survey of selected regions of sky planned for December 1988 had to be postponed. However, our limited data at 390 MHz show that the 30′ beam detected polarization temperatures between four to six times larger than found in surveys with a 1.3 arcmin resolution. This was true in both the highly polarized region around 1=140 degrees and in the North Polar Spur where polarization structures appear to be unresolved (<0.9 pc at the distance of the spur). High resolution observations will be critical to our understanding of the interstellar magnetic field and the scale-length of depolarizing structures.

scholarly journals Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS Hi data

2017 ◽  
Vol 601 ◽  
pp. A71 ◽  
Author(s):  
T. Ghosh ◽  
F. Boulanger ◽  
P. G. Martin ◽  
A. Bracco ◽  
F. Vansyngel ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Column Density ◽  
Large Scale ◽  
Dust Emission ◽  
Neutral Medium ◽  
Limiting Factor ◽  
Galactic Latitude ◽  
Galactic Magnetic Field ◽  
Emission Data ◽  
Field Orientation

The Planck survey has quantified polarized Galactic foregrounds and established that they are a main limiting factor in the quest for the cosmic microwave background B-mode signal induced by primordial gravitational waves during cosmic inflation. Accurate separation of the Galactic foregrounds therefore binds this quest to our understanding of the magnetized interstellar medium. The two most relevant empirical results from analysis of Planck data are line of sight depolarization arising from fluctuations of the Galactic magnetic field orientation and alignment of filamentary dust structures with the magnetic field at high Galactic latitude. Furthermore, Planck and H I emission data in combination indicate that most of the filamentary dust structures are in the cold neutral medium. The goal of this paper is to test whether these salient observational results, taken together, can account fully for the statistical properties of the dust polarization over a selected low column density region comprising 34% of the southern Galactic cap (b ≤ −30°). To do this, we construct a dust model that incorporates H I column density maps as tracers of the dust intensity structures and a phenomenological description of the Galactic magnetic field. By adjusting the parameters of the dust model, we were able to reproduce the Planck dust observations at 353GHz in the selected region. Realistic simulations of the polarized dust emission enabled by such a dust model are useful for testing the accuracy of component separation methods, studying non-Gaussianity, and constraining the amount of decorrelation with frequency.

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