A pre-launch low frequency VLBI survey for RadioAstron

Чуприков, А. А.; Girin, I. A.; Лихачев, С. Ф.; Молотов, И. Е.; Dementiev, Alexander; Lipatov, B. N.; Snegirev, S. D.; Mantovani, F.; Trigilio, C.; Ananthakrishnan, S.; Balasubramanian, V.; Kulkarni, V. K.; Subrahmanya, C. R.

doi:10.1016/s1387-6473(99)00091-3

Cited by 8 publications

(6 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…So far only a handful of works based on VLBI images at 327 MHz are available. They mainly focus on variable extragalactic sources (Altschuler et al 1995;Chuprikov et al 1999;Rampadarath et al 2009) or on deep wide field VLBI survey (Lenc et al 2008). The data presented here are the deepest and with the highest angular resolution at 327 MHz for a sample of CSS/GPS published so far.…”

Section: Introductionmentioning

confidence: 99%

VLBI images at 327 MHz of compact steep spectrum and GHz-peaked spectrum sources from the 3C and PW samples

Dallacasa,

Orienti,

Fanti

et al. 2021

Preprint

View full text Add to dashboard Cite

We present results on global very long baseline interferometry (VLBI) observations at 327 MHz of eighteen compact steep-spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources from the 3C and the Peacock & Wall catalogues. About 80 per cent of the sources have a 'double/triple' structure. The radio emission at 327 MHz is dominated by steep-spectrum extended structures, while compact regions become predominant at higher frequencies. As a consequence, we could unambiguously detect the core region only in three sources, likely due to self-absorption affecting its emission at this low frequency. Despite their low surface brightness, lobes store the majority of the source energy budget, whose correct estimate is a key ingredient in tackling the radio source evolution. Low-frequency VLBI observations able to disentangle the lobe emission from that of other regions are therefore the best way to infer the energetics of these objects. Dynamical ages estimated from energy budget arguments provide values between 2×10 3 and 5×10 4 yr, in agreement with the radiative ages estimated from the fit of the integrated synchrotron spectrum, further supporting the youth of these objects. A discrepancy between radiative and dynamical ages is observed in a few sources where the integrated spectrum is dominated by hotspots. In this case the radiative age likely represents the time spent by the particles in these regions, rather than the source age.

show abstract

Section: Introductionmentioning

confidence: 99%

VLBI images at 327 MHz of compact steep spectrum and GHz-peaked spectrum sources from the 3C and PW samples

Dallacasa,

Orienti,

Fanti

et al. 2021

Preprint

View full text Add to dashboard Cite

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

“…Only 2 of the sources observed by altetal95 (3C 395 and 3C 454.3) are part of the sample presented in this paper. Chuprikov et al (1999) have presented a list of 61 sources, observed in two separate experiments, at 327 MHz with a global Mark II VLBI array. Of the 61 sources observed, 25 were recommended for further detailed observations and images were made of 2 of these sources.…”

Section: Introductionmentioning

confidence: 99%