scholarly journals Unveiling the cause of hybrid morphology radio sources (HyMoRS)

2019 ◽  
Vol 491 (1) ◽  
pp. 803-822 ◽  
Author(s):  
Jeremy J Harwood ◽  
Tessa Vernstrom ◽  
Andra Stroe
Keyword(s):  
Radio Galaxies ◽  
Core Region ◽  
Line Of Sight ◽  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Array Configuration ◽  
The Core ◽  
Vlbi Observations ◽  
Rare Group

ABSTRACT Hybrid morphology radio sources (HyMoRS) are a rare group of radio galaxies in which differing Fanaroff & Riley morphologies (FR I/II) are observed for each of the two lobes. While they potentially provide insights into the formation of lobe structure, particle acceleration, and the FR dichotomy, previous work on HyMoRS has mainly been limited to low-resolution studies, searches for new candidates, and milliarcsecond-scale VLBI observations of the core region. In this paper, we use new multi-array configuration Very Large Array (VLA) observations between 1 and 8 GHz to determine the morphology of HyMoRS on arcsecond scales and perform the first well-resolved spectral study of these unusual sources. We find that while the apparent FR I lobe is centre brightened, this is the result of a compact acceleration region resembling a hotspot with a spectrum more consistent with an FR II (‘strong-flavour’) jet. We find that the spectra of the apparent FR I lobes are not similar to their classical counterparts and are likely the result of line-of-sight mixing of plasma across a range of spectral ages. We consider possible mechanisms that could lead to the formation of HyMoRS under such conditions, including environment asymmetry and restarted sources, concluding through the use of simple modelling that HyMoRS are the result of orientation effects on intrinsically FR II sources with lobes non-parallel to the inner jet.

scholarly journals OH main line masers in the M 82 starburst

2007 ◽  
Vol 3 (S242) ◽  
pp. 427-431
Author(s):  
M. K. Argo ◽  
A. Pedlar ◽  
T. W. B. Muxlow ◽  
R. J. Beswick
Keyword(s):  
Central Region ◽  
Supernova Remnants ◽  
Main Line ◽  
Line Of Sight ◽  
Starburst Galaxy ◽  
Large Array ◽  
Satellite Line ◽  
Very Large Array

AbstractA study of the distribution of OH gas in the central region of the nearby active starburst galaxy M82 has confirmed two previously known bright masers and revealed several new main line masers. Three of these are seen only at 1665 MHz, one is detected only at 1667 MHz, while the rest are detected in both lines. Observations covering both the 1665 and 1667 MHz lines, conducted with both the Very Large Array (VLA) and the Multi-Element Radio Linked Interferometer Network (MERLIN), have been used to accurately measure the positions and velocities of these features. This has allowed a comparison with catalogued continuum features in the starburst such as HII regions and supernova remnants, as well as known water and satellite line OH masers. Most of the main line masers appear to be associated with known HII regions although the two detected only at 1665 MHz are seen along the same line of sight as known supernova remnants.

Constraints on extragalactic-jet characteristics from lobe observations

1986 ◽  
Vol 64 (4) ◽  
pp. 378-380 ◽  
Author(s):  
Steven R. Spangler
Keyword(s):  
Hot Spot ◽  
Radio Galaxies ◽  
Large Array ◽  
Very Large Array ◽  
Upper Limits ◽  
Measured Speed ◽  
High Mach ◽  
Jet Characteristics ◽  
Double Radio Galaxies ◽  
Spot Motion

We discuss Very Large Array spectral and polarimetric observations of the lobes of luminous, double radio galaxies. These observations can provide information on the (typically undetected) jets responsible for the sources. Spectral steepening is usually observed in the lobes, with the radio spectral index increasing with distance from the hot spot. These data can be used to infer a "speed of separation" of the hot spot and lobe material. These speeds, typically 1.0 × 104–3.0 × 104 km/s, are in agreement with hydrocode models of jets, which interpret the measured speed of separation as a combination of hot-spot motion and backflow. Polarimetric observations indicate that in at least some sources, there is an undetectably small amount of internal Faraday rotation, indicating upper limits to the thermal-plasma density of a few times 10−5 cm−3 or less. These measurements are also in agreement with the numerical beam models, provided that the beam density is substantially less than that of the background medium. We conclude that the lobe observations indicate that these sources are powered by light, high-Mach-number beams.

scholarly journals VLBI Observations of NGC4151 at 6 cm Wavelength

1987 ◽  
Vol 121 ◽  
pp. 269-272
Author(s):  
E. Preuss ◽  
W. Alef ◽  
A. Pedlar
Keyword(s):  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Small Scale ◽  
Radio Sources ◽  
Vlbi Observations ◽  
Linear Extent ◽  
Nuclear Environment

The fraction of Seyfert galaxies containing linear radio sources is quite substantial and may be more than 50% (Ulvestad and Wilson 1984). About 20 of the well resolved Seyfert galaxies show double or triple structure on the arcsec scale. In this respect these objects are very reminiscent of the classical radio galaxies, but they are typically smaller than these by several orders of magnitude, both with regard to power ∼ 1039–1041 erg/s and linear extent kpc (Wilson, this volume). They are basically confined in the wider nuclear environment. The central small scale () radio sources in Seyfert galaxies are very weak, mJy at 6 cm wavelength, and have therefore hardly been observed with VLBI (see, e.g. Preuss 1984).

scholarly journals Outflow Angles and Bulk Lorentz Factors for Different Categories of AGN

1997 ◽  
Vol 163 ◽  
pp. 695-696 ◽  
Author(s):  
Erick. J. Guerra ◽  
Ruth A. Daly
Keyword(s):  
Lorentz Factor ◽  
Radio Galaxies ◽  
Line Of Sight ◽  
Radio Sources ◽  
Bl Lacertae Objects ◽  
Bl Lacertae ◽  
High Polarization ◽  
Inverse Compton ◽  
Doppler Factor ◽  
Bl Lacs

AbstractRelativistic outflows from AGN can be parameterized by θ, the angle subtended by the direction of the outflow and the line of sight to the observer, and γ, the bulk Lorentz factor of the outflow. The Doppler factor, δ, and the apparent speed in the plane of the sky, βapp, are combinations of θ and γ. The Doppler factor can be estimated using either the equipartition Doppler factor, δeq (Readhead 1994), or the inverse Compton Doppler factor, δIC. These Doppler factor estimates are combined with observed βapp to solve for θ and γ for different categories of AGN.Ghisellini et al. (1993) compute δIC for 105 compact radio sources, and Güijosa & Daly (1996) compute δeq for the same sample. Daly, Guerra, & Güijosa (1996) estimate θ and γ for the 43 sources that have βapp listed by Vermeulen & Cohen (1994) and δeq computed by Güijosa & Daly (1996).Solutions and errors for θ and γ are presented in Figures 1 and 2 using δeq and δIC respectively. Guerra & Daly (1996) discuss these estimates and errors in greater detail. These AGN fall into the following categories: BL Lacertae objects (BL Lacs), core-dominated high-polarization quasars (CDHPQ), core-dominated low-polarization quasars (CDLPQ), core-dominated quasars with no polarization information (CDQ(NPI)), lobe-dominated quasars (LDQ), and radio galaxies (RG).

scholarly journals VLBI Observations of Low-Redshift Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 129-130
Author(s):  
S.J. Tingay ◽  
D.L. Jauncey ◽  
R.A. Preston ◽  
D.L. Meier ◽  
J.E. Reynolds ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Vlbi Observations

Here we will describe briefly some of the VLBI observations we are making of low-redshift, compact radio sources in the southern hemisphere, using the Southern Hemisphere VLBI Experiment (SHEVE) array of telescopes (Jauncey et al., 1994).

A DEEP VERY LARGE ARRAY RADIO CONTINUUM SURVEY OF THE CORE AND OUTSKIRTS OF THE COMA CLUSTER

2009 ◽  
Vol 137 (5) ◽  
pp. 4436-4449 ◽  
Author(s):  
Neal A. Miller ◽  
Ann E. Hornschemeier ◽  
Bahram Mobasher
Keyword(s):  
Radio Continuum ◽  
Large Array ◽  
Coma Cluster ◽  
Very Large Array ◽  
The Core

scholarly journals Magnetic-Field Vector Maps of Nearby Spiral Galaxies

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 32 ◽  
Author(s):  
Hiroyuki Nakanishi ◽  
Kohei Kurahara ◽  
Kenta Anraku
Keyword(s):  
Magnetic Field ◽  
Spiral Galaxies ◽  
Transverse Magnetic ◽  
Field Vector ◽  
Line Of Sight ◽  
Large Array ◽  
Magnetic Vector ◽  
Very Large Array ◽  
Rotation Measure ◽  
The Galaxy

We present a method for determining the directions of magnetic-field vectors in a spiral galaxy using two synchrotron polarization maps, an optical image, and a velocity field. The orientation of the transverse magnetic field is determined with a synchrotron polarization map of a higher-frequency band, and the 180 ∘ -ambiguity is solved by using a sign of Rotation Measure (RM) after determining the geometrical orientation of a disk based on an assumption of trailing spiral arms. The advantage of this method is that the direction of a magnetic vector for each line of sight throughout the galaxy can inexpensively be determined, with easily available data and simple assumptions. We applied this method to three nearby spiral galaxies using archival data obtained with a Very Large Array (VLA) to demonstrate how it works. The three galaxies have both clockwise and counterclockwise magnetic fields, which implies that none of the three galaxies is classified in a simple Axis-Symmetric type, but types of higher modes, and that magnetic reversals commonly exist.

SiO maser emission as a stellar line-of-sight velocity tracer in the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 47-48
Author(s):  
Michael C. Stroh ◽  
Ylva M. Pihlström ◽  
Loránt O. Sjouwerman ◽  
Megan O. Lewis ◽  
Mark J Claussen ◽  
...  
Keyword(s):  
Gravitational Potential ◽  
Complex Structure ◽  
Dynamical Evolution ◽  
Line Of Sight ◽  
Large Array ◽  
Very Large Array ◽  
Giant Stars ◽  
Test Models ◽  
Final Sample ◽  
Red Giant

AbstractThe Bulge Asymmetries and Dynamical Evolution (BAaDE) survey aims to explore the complex structure of the inner Galaxy and Galactic Bulge, by using the 43 GHz receivers at the Karl G. Jansky Very Large Array (VLA) and the 86 GHz receivers at the Atacama Large Millimeter/submillimeter Array (ALMA) to observe SiO maser lines in red giant stars. The goal is to construct a sample of stellar point-mass probes that can be used to test models of the gravitational potential, and the final sample is expected to provide at least 20,000 line-of-sight velocities and positions. A possible bias between the VLA and the ALMA SiO maser lines is explored, and the 86 GHz SiO line-peak velocities agree using either of the four sampled lines. Additionally, the SiO maser velocities agree with the OH maser derived velocities.

Subarcminute resolution imaging of radio sources at 74 MHz with the Very Large Array

1993 ◽  
Vol 106 ◽  
pp. 2218 ◽  
Author(s):  
N. E. Kassim ◽  
R. A. Perley ◽  
W. C. Erickson ◽  
K. S. Dwarakanath
Keyword(s):  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Resolution Imaging
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