Observational Evidence for Young Radio Galaxies Is Triggered by Accretion Disk Instability

Wu, Qingwen

doi:10.1088/0004-637x/701/2/l95

Cited by 37 publications

(36 citation statements)

References 44 publications

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“…Therefore the poloidal component of the magnetic field accelerates the particles, and at the same time it forms the relativistic jet and surrounding wind. The accretion disk of NLS1s is luminous enough to be in the radiation pressure dominated regime in which radiative instability occurs (Moderski & Sikora 1996;Ghosh & Abramowicz 1997;Czerny et al 2009;Wu 2009;Foschini 2011a). This instability might translate into a change in angle, and then in an intermittent BP contribution to the jet.…”

Section: Radio Quiet Versus Radio Loudmentioning

confidence: 99%

[O III] line properties in two samples of radio-emitting narrow-line Seyfert 1 galaxies

Berton

Foschini

Ciroi

et al. 2016

A&A

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The [O III] λλ 4959, 5007 lines are a useful proxy to test the kinematic of the narrow-line region (NLR) in active galactic nuclei (AGN). In AGN, and particularly in narrow-line Seyfert 1 galaxies (NLS1s) these lines often show few peculiar features, such as blue wings, often interpreted as outflowing component, and a shift − typically toward lower wavelengths − of the whole spectroscopic feature in some exceptional sources, the so-called blue outliers, which are often associated to strong winds. We investigated the incidence of these peculiarities in two samples of radio-emitting NLS1s, one radio-loud and one radio-quiet. We also studied a few correlations between the observational properties of the [O III] lines and those of the AGN. Our aim was to understand the difference between radio-quiet and radio-loud NLS1s, which may in turn provide useful information on the jet formation mechanism. We find that the NLR gas is much more perturbed in radio-loud than in radio-quiet NLS1s. In particular the NLR dynamics in γ-ray emitting NLS1s appears to be highly disturbed, and this might be a consequence of interaction with the relativistic jet. The less frequently perturbed NLR in radio-quiet NLS1s suggests instead that these sources likely do not harbor a fully developed relativistic jet. Nonetheless blue-outliers in radio-quiet NLS1s are observed, and we interpret them as a product of strong winds.

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Section: Radio Quiet Versus Radio Loudmentioning

confidence: 99%

[O III] line properties in two samples of radio-emitting narrow-line Seyfert 1 galaxies

Berton

Foschini

Ciroi

et al. 2016

A&A

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“…However, Altamirano et al (2011) recently reported another source, IGR J17091-3624, that seems to show variability similar to that of GRS 1915+105 at lower luminosity, which suggests that there may be other variables associated with limit-cycle behavior in X-ray binaries. Although the analogous limit cycle in active galactic nuclei (AGNs) is difficult to observe directly due to its long timescale, some intermittent activity in young radio galaxies has been ascribed to thermal instability in the disk (Czerny et al 2009;Wu 2009). …”

Section: Introductionmentioning

confidence: 99%

Thermal Stability of a Thin Disk With Magnetically Driven Winds

Begelman

2014

ApJ

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The absence of thermal instability in the high/soft state of black hole X-ray binaries, in disagreement with the standard thin disk theory, has been a long-standing riddle for theoretical astronomers. We have tried to resolve this question by studying the thermal stability of a thin disk with magnetically driven winds in theṀ-Σ plane. It is found that disk winds can greatly decrease the disk temperature and thus help the disk become more stable at a given accretion rate. The critical accretion rate,Ṁ crit , corresponding to the thermal instability threshold, is significantly increased in the presence of disk winds. For α = 0.01 and B φ = 10B p , the disk is quite stable even for a very weak initial poloidal magnetic field [β p,0 ∼ 2000, β p = (P gas + P rad )/(B 2 p /8π )]. However, when B φ = B p or B φ = 0.1B p , a somewhat stronger (but still weak) field (β p,0 ∼ 200 or β p,0 ∼ 20) is required to make the disk stable. Nevertheless, despite the great increase ofṀ crit , the luminosity threshold, corresponding to instability, remains almost constant or decreases slowly with increasingṀ crit due to decreased gas temperature. The advection and diffusion timescales of the large-scale magnetic field threading the disk are also investigated in this work. We find that the advection timescale can be smaller than the diffusion timescale in a disk with winds, because the disk winds take away most of the gravitational energy released in the disk, resulting in the decrease of the magnetic diffusivity η and the increase of the diffusion timescale.

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“…A consistent number of restarting radio sources have been found in the past 20 yr, and hypotheses about their nature have been proposed (Czerny et al 2009;Wu 2009;Marecki et al 2006). Some of them correspond to GPS sources or CSS sources, which are known to be young radio sources.…”

Section: Low-frequency Componentsmentioning

confidence: 98%

Restarting radio activity and dust emission in radio-loud broad absorption line quasars

Bruni

Mack

Montenegro‐Montes

et al. 2015

A&A

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Context. Broad absorption line quasars (BAL QSOs) are objects that show absorption from relativistic outflows that have velocities up to 0.2c. In about 15% of quasars, these manifest as absorption troughs on the blue side of UV emission lines, such as C  and Mg .The launching mechanism and duration of these outflows is not clear yet. Aims. In this work, we complement the information collected in the cm band for our previously presented sample of radio loud BAL QSOs (25 objects with redshifts 1.7 < z < 3.6) with new observations in the m and mm bands. Our aim is to verify the presence of old, extended radio components in the MHz range and probe the emission of dust (linked to star formation) in the mm domain. Methods. We observed 5 sources from our sample, which already presented hints of low-frequency emission, with the GMRT at 235 and 610 MHz. Another 17 sources (more than half the sample) were observed with bolometer cameras at IRAM-30 m (MAMBO2, 250 GHz) and APEX (LABOCA and SABOCA, 350 and 850 GHz, respectively). Results. All sources observed with the GMRT present extended emission on a scale of tens of kpc. In some cases these measurements allow us to identify a second component in the SED at frequencies below 1.4 GHz, beyond the one already studied in the GHz domain. In the mm band, only one source shows emission clearly ascribable to dust, detached from the synchrotron tail. Upper limits were obtained for the remaining targets. Conclusions. These findings confirm that BAL QSOs can also be present in old radio sources or even in restarting ones where favourable conditions for the outflow launching or acceleration are present. A suggestion that these outflows could be precursors of the jet comes from the possibility that ∼70% of our sample is in a GigaHertz Peaked Spectrum (GPS) or Compact Steep Spectrum (CSS)+GPS phase. This would confirm the idea proposed by other authors that these outflows could be recollimated to form the jet. Compared with previous works in the literature, dust emission seems to be weaker than what is expected in "normal" QSOs (both radio loud and radio quiet ones), suggesting that a feedback mechanism could inhibit star formation in radio-loud BAL QSOs.

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Observational Evidence for Young Radio Galaxies Is Triggered by Accretion Disk Instability

Cited by 37 publications

References 44 publications

[O III] line properties in two samples of radio-emitting narrow-line Seyfert 1 galaxies

[O III] line properties in two samples of radio-emitting narrow-line Seyfert 1 galaxies

Thermal Stability of a Thin Disk With Magnetically Driven Winds

Restarting radio activity and dust emission in radio-loud broad absorption line quasars

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