Testing Models of Radio Galaxy Evolution and the Cosmological Impact of FR II Radio Galaxies

Barai, Paramita; Wiita, Paul J.

doi:10.1086/511175

Cited by 25 publications

(37 citation statements)

References 71 publications

(90 reference statements)

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“…assuming more spherical sources. The question of volume filling factor of lobes is also addressed with more care in the works by Barai & Wiita (2007) and Barai (2008), with which the results of our work agree. The former paper investigates the volume filling factor by lobes using the models of Kaiser & Alexander (1997), Blundell et al (1999) and Manolakou & Kirk (2002), and also modifications by incorporating a variable hotspot size growing with the source age.…”

Section: Volume Filling Factor Of the Universe By Lobessupporting

confidence: 58%

“…The relative contribution from FR I sources during the quasar era, for example to the volume filling factor, is modest. The volume of a typical FR I will be much smaller than the volume of an FR II source, since FR I seems to have a much higher efficiency in converting jet thrust to radio flux and are also much dimmer (see Barai & Wiita 2007 and references therein). In assessing the importance of FR I objects to the CXB, the question at hand is the integrated number of γ≃ 10 3 particles that the FR I produces during its lifetime.…”

Section: Discussionmentioning

confidence: 99%

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Inverse-Compton ghosts and double-lobed radio sources in the X-ray sky

Mocz¹,

Fabian²,

Blundell³

2011

Monthly Notices of the Royal Astronomical Society

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In this study we predict the total distributions of powerful (FR II) active double-lobed radio galaxies and ghost sources, and their observable distribution in the X-ray sky. We develop an analytic model for the evolution of the lobe emission at radio and X-ray energies. During jet activity, a double radio source emits synchrotron radiation in the radio and X-ray emission due to inverse-Compton (IC) upscattering by gamma~10^3 electrons of the cosmic microwave background. After the jets switch off, the radio luminosity (due to higher gamma electrons) falls faster than the X-ray luminosity and for some time the source appears as an IC ghost of a radio galaxy before becoming completely undetectable in the X-ray. With our model, for one set of typical parameters, we predict radio lobes occupy a volume fraction of the universe of 0.01, 0.03, 0.3 at z=2 (during the quasar era) of the filamentary structures in which they are situated, for typical jet lifetimes 5*10^7 yr, 10^8 yr, 5*10^8 yr; however since the inferred abundance of sources depends on how quickly they fall below the radio flux limit the volume filling factor is found to be a strong function of radio galaxy properties such as energy index and minimum gamma factor of injected particles, the latter not well constrained by observations. We test the predicted number density of sources against the Chandra X-ray Deep Field North survey and also find the contribution to the unresolved cosmic X-ray background by the lobes of radio galaxies. 10-30 per cent of observable double-lobed structures in the X-ray are predicted to be IC ghosts. The derived X-ray luminosity function of our synthetic population shows that double-lobed sources have higher space densities than X-ray clusters at redshifts z>2 and X-ray luminosities above 10^44 erg s^-1.Comment: 14 pages, 14 figure

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Section: Volume Filling Factor Of the Universe By Lobessupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Inverse-Compton ghosts and double-lobed radio sources in the X-ray sky

Mocz¹,

Fabian²,

Blundell³

2011

Monthly Notices of the Royal Astronomical Society

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“…This is because the probability of recurring semimajor mergers, each causing a large spin-flip is quite small, in that the temporal interval between them certainly is > 1 Gyr for semi-major mergers with mass ratios > 1 : 30 and even longer for major mergers (Z. Lippai, private communication, based on the merger tree program in Lippai et al 2009). Whereas, if jets are restarted while the earlier lobes are still visible, then it is likely that they have done so within ∼ 10 8 yr of the launch of the original jets, since visible radio activity seldom lasts much longer than that (e.g., Blundell & Rawlings 1999;Gopal-Krishna & Wiita 2001;Barai & Wiita 2007;Kaiser & Best 2007). In this way, the situations where the incipient inner lobe pair is essentially aligned with the (outer) primary lobes, as shown for a few XRGs (SS09), can be explained naturally.…”

Section: Appendix A: the Expected Mass Ratio Of Merging Smbhs And Conmentioning

confidence: 99%

On the origin of X-shaped radio galaxies

Gopal-Krishna

Biermann

Gergely

et al. 2012

Res. Astron. Astrophys.

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After a brief, critical review of the leading explanations proposed for the small but important subset of radio galaxies showing an X-shaped morphology (XRGs) we propose a generalized model, based on the jet-shell interaction and spin-flip hypotheses. The most popular scenarios for this intriguing phenomenon invoke either hydrodynamical backflows and over-pressured cocoons or rapid jet reorientations, presumably from the spin-flips of central engines following the mergers of pairs of galaxies, each of which contains a supermassive black hole (SMBH). We confront these models with a number of key observations and thus argue that none of the models is capable of explaining the entire range of salient observational properties of XRGs, although some of the arguments raised in the literature against the spin-flip scenario are probably not tenable. We then propose here a new scenario which also involves galactic mergers but would allow the spin of the central engine to maintain its direction. Motivated by the detailed multi-band observations of the nearest radio galaxy, Centaurus A, this new model emphasizes the role of interactions between the jets and the shells of stars and gas that form and rotate around the merged galaxy and can cause temporary deflections of the jets, occasionally giving rise to an X-shaped radio structure. Although each of the models is likely to be relevant to a subset of XRGs, the bulk of the evidence indicates that most of them are best explained by the jet-shell interaction or spin-flip hypotheses.

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“…A lifetime of 5 × 10 8 yr has been used in theoretical modeling of radio galaxies by Blundell et al (1999) and Barai & Wiita (2007). Observations of X-ray activity in the AGN (Barger et al 2001), SDSS optical studies of active galaxies (Miller et al 2003), and BH demographics arguments (e.g., Marconi et al 2004) all support an AGN activity lifetime of ∼ 10 8 yr or more (see also McLure & Dunlop 2004).…”

Section: Agn Lifetimementioning

confidence: 99%

Anisotropic Active Galactic Nucleus Outflows and Enrichment of the Intergalactic Medium. I. Metal Distribution

Germain

Barai

Martel

2009

ApJ

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We investigate the cosmological-scale influence of outflows driven by active galactic nuclei (AGNs) on metal enrichment of the intergalactic medium (IGM). AGNs are located in dense cosmological structures which tend to be anisotropic. We designed a semianalytical model for anisotropic AGN outflows which expand away along the direction of least resistance. This model was implemented into a cosmological numerical simulation algorithm for simulating the growth of large-scale structure in the universe. Using this modified algorithm, we perform a series of nine simulations inside cosmological volumes of size (128 h −1 Mpc) 3 , in a concordance ΛCDM universe, varying the opening angle of the outflows, the lifetimes of the AGNs, their kinetic fractions, and their level of clustering. For each simulation, we compute the volume fraction of the IGM enriched in metals by the outflows. The resulting enriched volume fractions are relatively small at z 2.5, and then grow rapidly afterward up to z = 0. We find that AGN outflows enrich from 65% to 100% of the entire universe at the present epoch, for different values of the model parameters. The enriched volume fraction depends weakly on the opening angle of the outflows. However, increasingly anisotropic outflows preferentially enrich underdense regions, a trend found more prominent at higher redshifts and decreasing at lower redshifts. The enriched volume fraction increases with increasing kinetic fraction and decreasing AGN lifetime, and level of clustering.

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Testing Models of Radio Galaxy Evolution and the Cosmological Impact of FR II Radio Galaxies

Cited by 25 publications

References 71 publications

Inverse-Compton ghosts and double-lobed radio sources in the X-ray sky

Inverse-Compton ghosts and double-lobed radio sources in the X-ray sky

On the origin of X-shaped radio galaxies

Anisotropic Active Galactic Nucleus Outflows and Enrichment of the Intergalactic Medium. I. Metal Distribution

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