A 327 MHz VLBI study of high redshift radio galaxies 1345+245, 1809+407 and 2349+289

Cai, Z. D.; Nan, R.; Schilizzi, R. T.; Miley, G. K.; Bremer, M.; Dam, B.; Röttgering, H. J. A.; Liang, H.; Chambers, K.; Gurvits, L. I.; Zhang, H. Y.

doi:10.1051/0004-6361:20011579

Cited by 8 publications

(3 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our estimates of the magnetic field in those components are in good agreement with magnetic field estimates for other HzRGs (e.g. Cai et al 2002), and significantly higher than estimates found in typical nearby powerful radio galaxies (e.g. B ∼ 3 × 10 −4 for Cygnus A: Carilli & Barthel 1996).…”

Section: R E S U Lt S a N D Discussionsupporting

confidence: 89%

The extremely asymmetric radio structure of the z = 3.1 radio galaxy B3 J2330 + 3927

Breuck

2005

Monthly Notices of the Royal Astronomical Society: Letters

View full text Add to dashboard Cite

We report on 1.7‐ and 5.0‐GHz observations of the z= 3.087 radio galaxy B3 J2330 + 3927, using the Very Long Baseline Array (VLBA), and archival 1.4‐ and 8.4‐GHz Very Large Array (VLA) data. Our VLBA data identify a compact, flat‐spectrum (α5 GHz1.7 GHz=−0.2 ± 0.1; Sν∝να) radio component as the core. The VLA images show that the fraction of core emission is very large (fc≈ 0.5 at 8.4 GHz), and reveal a previously undetected, very faint counterjet, implying a radio lobe flux density ratio R≳ 11 and a radio lobe distance ratio Q≈ 1.9. Those values are much more common in quasars than in radio galaxies, but the optical/near‐infrared spectra show a clear type II active galactic nucleus for B3 J2330 + 3927, confirming that it is indeed a radio galaxy. Unlike all other radio galaxies, the bright Lyα‐emitting gas is located towards the furthest radio arm. We argue against environmental and relativistic beaming effects being the cause of the observed asymmetry, and suggest this source has intrinsically asymmetric radio jets. If this is the case, B3 J2330 + 3927 is the first example of such a source at high redshift, and seems to be difficult to reconcile with the unified model, which explains the differences between quasars and radio galaxies as being due to orientation effects.

show abstract

Section: R E S U Lt S a N D Discussionsupporting

confidence: 89%

The extremely asymmetric radio structure of the z = 3.1 radio galaxy B3 J2330 + 3927

Breuck

2005

Monthly Notices of the Royal Astronomical Society: Letters

View full text Add to dashboard Cite

show abstract

“…In general, the vast majority of the very long baseline interferometry (VLBI) experiments have been carried out mostly at 1.4 GHz or higher frequencies, where compact and flat‐spectrum radio sources clearly shine, and the telescope availability and performance are at their best. Some VLBI studies at 327 MHz have been published (e.g., Cai et al 2002; Lenc et al 2008). However, the poor quality of the images did not allow us to carry out accurate studies of the physics in the radio sources which were detected.…”

Section: Introductionmentioning

confidence: 99%

Parsec‐scale view of CSS/GPS sources at 327 MHz

Dallacasa

Orienti

2021

Astron Nachr

View full text Add to dashboard Cite

Global very long baseline interferometry (VLBI) observations at low frequencies are of great importance since they allow us to test the oldest part of the relativistic electron populations in young radio sources. At 327 MHz (𝜆 ∼ 92 cm), the most compact regions are self-absorbed, and the number of cores detected is very small. This could provide useful measurements of the magnetic field in the relativistic plasma, to be compared with the equipartition field derived from minimum energy arguments. Partial self-absorption takes place also in hot-spots. However, disentangling the hot-spot emission from that of the lobe turned out to be rather difficult. On the other hand, a clearer and more complete characterization of the volumes occupied by the magnetized relativistic plasma and its total energy content can be obtained at 327 MHz. In turn, an independent estimate of the source age can be inferred, on the basis of simple assumptions on the jet power. Here, we show that the ages derived in this way (between 2 ⋅ 10 3 and 5 ⋅ 10 4 year) are consistent with the radiative ages determined from the break frequency in the radio spectrum.

show abstract

“…As a result, although several hundred 90 cm VLBI observations have been made over the past two decades, images of only a few tens of sources have been published e.g. Altschuler et al (1995); Lazio & Cordes (1998); Chuprikov et al (1999); Cai et al (2002). With such a small sample it is difficult to quantify the total population and nature of these sources.…”

Section: Introductionmentioning

confidence: 99%

Studies of Radio Galaxies and Starburst Galaxies using Wide-field, High Spatial Resolution Radio Imaging

Lenc¹

2014

Preprint

View full text Add to dashboard Cite

This thesis reports on the application of new wide-field Very Long Baseline Interferometry (VLBI) imaging techniques using real data for the first time. These techniques are used to target three specific science areas: (i) a sub-parsec-scale study of compact radio sources in nearby starburst galaxies, (ii) a study of jet interactions in active radio galaxies, and (iii) an unbiased study of the sub-arcsecond, 90 cm sky.Six local southern starburst galaxies are surveyed on sub-parsec-scales using wide-field VLBI techniques. Compact radio sources are detected in two of the most prominent galaxies, NGC 253 and NGC 4945. Modelling of the compact source spectra reveal the majority have steep spectra, associated with supernova remnants, and are significantly free-free absorbed by a dense ionised screen. Limits on the supernova rate and star formation rate in these galaxies are estimated based on source fading, source population modelling, and on source counts and sizes. No or few compact radio sources are detected in the less prominent galaxies, presumably as a result of reduced star formation and/or star formation in sparse environments that result in weak and short-lived supernovae and remnants.The hot spots and interaction regions of three active radio galaxies are studied at parsec-scales, for the first time, using wide-field VLBI imaging. The resulting images have provided the most detailed views of these regions to date. In two of the target sources, PKS 0518−458 (Pictor A) and PKS 0521−365, the hot spot emission is resolved into a set of compact components. The emission mechanisms in the hot spots are discussed based on their morphology and additional multi-wavelength data.Two overlapping 28 deg 2 regions are surveyed in detail using wide-field VLBI techniques in the first systematic (and non-biased), deep, high resolution survey of the low frequency sky. This represents a field of view two orders of magnitude greater than anything previously attempted in a single pointing with VLBI. A total of 27 sources were detected as far as 2 • from the phase centre. The results of the survey suggest that new low frequency telescopes, such as LOFAR and SKA, should detect many compact radio sources and that plans to extend these arrays to baselines of several thousand kilometres are warranted.iii Having reached the conclusion of this grand and exciting adventure, I would like to sincerely thank and acknowledge those that have supported me over the past four years.Firstly, I wish to thank my wife Wendy for the great sacrifices she has endured over these years to enable me to follow my new field of research. This work would not have been possible without her love and support. I also wish to apologise to my son Arin, who came into the world half-way through my PhD thesis, for not being able to provide the amount of attention he deserved from his loving father.Special thanks go to my PhD thesis supervisor, Prof. Steven Tingay. On our first meeting he handed me a radio image from his recent research. On the face of it, the image a...

show abstract

A 327 MHz VLBI study of high redshift radio galaxies 1345+245, 1809+407 and 2349+289

Cited by 8 publications

References 32 publications

The extremely asymmetric radio structure of the z = 3.1 radio galaxy B3 J2330 + 3927

The extremely asymmetric radio structure of the z = 3.1 radio galaxy B3 J2330 + 3927

Parsec‐scale view of CSS/GPS sources at 327 MHz

Studies of Radio Galaxies and Starburst Galaxies using Wide-field, High Spatial Resolution Radio Imaging

Contact Info

Product

Resources

About