VLBI observations at 2.3 GHz of the compact galaxy 1934-638

Tzioumis, A. K.; Jauncey, D. L.; Preston, R. A.; Meier, D. L.; Nicolson, G. D.; Batchelor, R.; Gates, Joe; Hamilton, P. A.; Harvey, Bruce; Haynes, R. F.; Johnson, B.; McCulloch, P. M.; Moorey, G.; Morabito, D. D.; Niell, A. E.; Robertson, J. G.; Royle, G. W. R.; Skjerve, L. J.; Slade, M. A.; Slee, O. B.; Watkinson, Anne; Wehrle, A. E.; Wright, A. E.

doi:10.1086/115124

Cited by 28 publications

(7 citation statements)

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“…The structure seen in Figure 3 agrees very well with all previous published images of PKS 1934−638 in this angular resolution regime with synthesised beams of ≈ 5-10 mas (Tzioumis et al 1989;King 1994;Tzioumis et al 1996Tzioumis et al , 2002Ojha et al 2004;Lovell et al 2010). The two components have been interpreted as the terminal hot spots from oppositely directed jets emerging from a black hole accretion disk system, a smaller and younger version of an FR-I or FR-II type radio galaxy, into which GPS radio galaxies are postulated to evolve.…”

Section: New Vlbi Observations and Resultssupporting

confidence: 89%

Evolution of the Parsec-Scale Structure of PKS 1934–638 Revisited: First Science With the Askap and New Zealand Telescopes

Tzioumis

Tingay

Stansby

et al. 2010

The Astronomical Journal

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We have studied the archetypal Gigahertz Peaked Spectrum radio galaxy, PKS 1934−638, using the Australian Long Baseline Array, augmented with two new telescopes that greatly improve the angular resolution of the array. These VLBI observations represent the first scientific results from a new antenna in NZ and the first antenna of the Australian SKA Pathfinder (ASKAP). A compact double radio source, PKS 1934−638, has been monitored over a period of 40 years, and the observation described here provides the latest datum, eight years after the previous observation, to aid in the study of the long-term evolution of the source structure. We take advantage of these new long baselines to probe PKS 1934−638 at the relatively low frequency of 1.4 GHz, in order to examine the effects of optical depth on the structure of the radio source. Optical depth effects, resulting in the observation of frequency dependent structure, may have previously been interpreted in terms of an expansion of the source as a function of time. Expansion and frequency dependent effects are important to disentangle in order to estimate the age of PKS 1934−638. We show that frequency dependent structure effects are likely to be important in PKS 1934−638 and present a simple two-dimensional synchrotron source model in which opacity effects due to synchrotron self-absorption are taken into account. Evidence for expansion of the radio source over 40 years is therefore weak, with consequences for the estimated age of the radio source.

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Section: New Vlbi Observations and Resultssupporting

confidence: 89%

Evolution of the Parsec-Scale Structure of PKS 1934–638 Revisited: First Science With the Askap and New Zealand Telescopes

Tzioumis

Tingay

Stansby

et al. 2010

The Astronomical Journal

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“…Because the signal-to-noise of each individual visibility measurement is very low, determin-ing the increase in χ 2 that indicates a significant discrepancy between models is not straightforward. Previous authors have often relied on visual inspection of images and visibility data in order to determine model goodness-of-fit 40,41 . Due to the low signal-to-noise ratio of our target image, we have taken a different approach.…”

Section: Comparison Between the Vlbi Data And Synthetic Imagesmentioning

confidence: 99%

Superluminal motion of a relativistic jet in the neutron-star merger GW170817

Mooley

Deller

Gottlieb

et al. 2018

Nature

608

667

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The binary neutron-star merger GW170817 was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of about 41 megaparsecs from Earth. The radio and X-ray afterglows of GW170817 exhibited delayed onset, a gradual increase in the emission with time (proportional to t) to a peak about 150 days after the merger event, followed by a relatively rapid decline. So far, various models have been proposed to explain the afterglow emission, including a choked-jet cocoon and a successful-jet cocoon (also called a structured jet). However, the observational data have remained inconclusive as to whether GW170817 launched a successful relativistic jet. Here we report radio observations using very long-baseline interferometry. We find that the compact radio source associated with GW170817 exhibits superluminal apparent motion between 75 days and 230 days after the merger event. This measurement breaks the degeneracy between the choked- and successful-jet cocoon models and indicates that, although the early-time radio emission was powered by a wide-angle outflow (a cocoon), the late-time emission was most probably dominated by an energetic and narrowly collimated jet (with an opening angle of less than five degrees) and observed from a viewing angle of about 20 degrees. The imaging of a collimated relativistic outflow emerging from GW170817 adds substantial weight to the evidence linking binary neutron-star mergers and short γ-ray bursts.

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“…The instrument was used in SLIT mode with 1.6×11 arcsec slit for the UVB arm, 1.5×11 arcsec slit for the VIS arm and 1.5×11 arcsec slit for the NIR arm. The selected slit position angle (PA) was set to be 104 degrees (from north to east), close to the PA of the source's radio axis (i.e., 90 degrees, Tzioumis et al 1989) and including both the PKS B1934-63 host galaxy and the fainter merging or interacting companion.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Probing multi-phase outflows and AGN feedback in compact radio galaxies: the case of PKS B1934-63

Santoro

Rose

Morganti

et al. 2018

A&A

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Young radio AGN are pivotal for our understanding of many of the still-debated aspects of AGN feedback. In this paper we present a study of the interstellar medium (ISM) in the compact, peaked-spectrum radio galaxy PKS B1934-63 using X-shooter observations. Most of the warm ionized gas resides within a circum-nuclear disk with a radius of about 200 pc that is likely to constitute the gas reservoir from which the central black hole feeds. On the other hand, we find a biconical outflow of warm ionized gas with an estimated radius of 59 ± 12 pc. This matches the radial extent of the radio source and suggests that the outflow is jet driven. Thanks to the superior wavelength coverage of the data, we can estimate the density of the warm ionized gas using the trans-auroral line technique, and we find that the outflowing gas has remarkably high density, up to log n e (cm −3 ) 5.5. The estimated mass outflow rate is low (Ṁ =10 −3 -10 −1 M yr −1 ), and the AGN feedback operates at relatively low efficiency (Ė/L bol ∼ 10 −4 -10 −3 %). In addition, optical and near-IR line ratios show that the expansion of the radio source drives fast shocks (with velocities v s 500 km s −1 ) that ionize and accelerate the outflowing gas. At odds with the properties of other compact, peaked-spectrum radio sources hosting warm ionized gas outflows, we do not find signs of kinematically disturbed or outflowing gas in phases colder than the warm ionized gas. We argue that this is due to the young age of our source and thus to the recent nature of the AGN-ISM interaction, and suggest that cold gas forms within the outflowing material and the shock-ionized outflowing gas of PKS B1934-63 did not have enough time to cool down and accumulate in a colder phase. This scenario is also supported by the multi-phase outflows of other compact and young radio sources in the literature.

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VLBI observations at 2.3 GHz of the compact galaxy 1934-638

Cited by 28 publications

References 0 publications

Evolution of the Parsec-Scale Structure of PKS 1934–638 Revisited: First Science With the Askap and New Zealand Telescopes

Evolution of the Parsec-Scale Structure of PKS 1934–638 Revisited: First Science With the Askap and New Zealand Telescopes

Superluminal motion of a relativistic jet in the neutron-star merger GW170817

Probing multi-phase outflows and AGN feedback in compact radio galaxies: the case of PKS B1934-63

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