Looking below the floor: constraints on the AGN radio luminosity functions at low power

Capetti, A.; Raiteri, C. M.

doi:10.1093/mnrasl/slv030

Cited by 6 publications

(3 citation statements)

References 28 publications

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“…The limits also tighten in a similar manner if, for instance, our LX cut-off has underestimated a significant contribution from lower luminosity FR I RGs (e.g. Balmaverde et al 2006;Hardcastle et al 2009;Capetti & Raiteri 2015).…”

Section: The X-ray Luminosity Functionsupporting

confidence: 55%

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

Jacobsen

et al. 2015

Mon. Not. R. Astron. Soc.

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High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN) jets: their baryonic and leptonic contents, and particle production efficiency. Testing two standard neutrino production models for local source Cen A (Koers & Tinyakov 2008; Becker & Biermann 2009), we calculate the high-energy neutrino spectra of single AGN sources and derive the flux of high-energy neutrinos expected for the current epoch. Assuming that accretion determines both X-rays and particle creation, our parametric scaling relations predict neutrino yield in various AGN classes. We derive redshift-dependent number densities of each class, from Chandra and Swift/BAT X-ray luminosity functions (Silverman et al. 2008;Ajello et al. 2009). We integrate the neutrino spectrum expected from the cumulative history of AGN (correcting for cosmological and source effects, e.g. jet orientation and beaming). Both emission scenarios yield neutrino fluxes well above limits set by IceCube (by " 4-10 6ˆa t 1 PeV, depending on the assumed jet models for neutrino production). This implies that: (i) Cen A might not be a typical neutrino source as commonly assumed; (ii) both neutrino production models overestimate the efficiency; (iii) neutrino luminosity scales with accretion power differently among AGN classes and hence does not follow X-ray luminosity universally; (iv) some AGN are neutrino-quiet (e.g. below a power threshold for neutrino production); (v) neutrino and X-ray emission have different duty cycles (e.g. jets alternate between baryonic and leptonic flows); or (vi) some combination of the above.

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Section: The X-ray Luminosity Functionsupporting

confidence: 55%

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

Jacobsen

et al. 2015

Mon. Not. R. Astron. Soc.

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“…2), which is typically a giant elliptical. They are characterised by GHz radio powers 10 22 W Hz −1 (e.g., Sadler et al, 1989;Ledlow & Owen, 1996), which represents the faint end of the RG LF (e.g., Urry & Padovani, 1995;van Velzen et al, 2012;Capetti & Raiteri, 2015) and, therefore, is a natural threshold for "radioloudness" in galaxies (some papers have suggested the presence of non-thermal, jet emission in early type galaxies as faint as 10 20 W Hz −1 : e.g., Balmaverde & Capetti, 2006). Fanaroff & Riley (1974) recognized that RGs separate into two distinct luminosity classes, each with its own characteristic radio morphology.…”

Section: Radio Galaxiesmentioning

confidence: 99%

The faint radio sky: radio astronomy becomes mainstream

Padovani

2016

Astron Astrophys Rev

182

136

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Radio astronomy has changed. For years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. Now it is reaching such faint flux densities that it detects mainly star-forming galaxies and the more common radio-quiet active galactic nuclei. These sources make up the bulk of the extragalactic sky, which has been studied for decades in the infrared, optical, and Xray bands. I follow the transformation of radio astronomy by reviewing the main components of the radio sky at the bright and faint ends, the issue of their proper classification, their number counts, luminosity functions, and evolution. The overall "big picture" astrophysical implications of these results, and their relevance for a number of hot topics in extragalactic astronomy, are also discussed. The future prospects of the faint radio sky are very bright, as we will soon be flooded with survey data. This review should be useful to all extragalactic astronomers, irrespective of their favourite electromagnetic band(s), and even stellar astronomers might find it somewhat gratifying.

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“…At low luminosities, the RLF does not significantly depart from a power law, and their results suggest that any break must be located below log P r ∼ 21.6 W Hz −1 , where the limited number of observed objects makes the RLF shape uncertain. On the other hand, the number density of radio emitting AGNs cannot exceed that of their potential hosts: this argument has been used by Capetti & Raiteri (2015), requiring a minimum black hole mass of log (M BH /M ) > 7.5 for the host of RL-AGNs. With this approach they found that the break in the RLF of RL-AGNs must be located at P r > ∼ 10 20.5 W Hz −1 .…”

Section: The Bl Lac Rlf and The Agn Unified Modelmentioning

confidence: 99%

Looking for the least luminous BL Lacertae objects

Capetti

Raiteri

2015

A&A

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Among active galactic nuclei, BL Lac objects show extreme properties that have been interpreted as the effect of relativistic beaming on the emission from a plasma jet oriented close to the line of sight. The Doppler amplification of the jet emission makes them ideal targets for studying jet physics. In particular, low-power BL Lacs (LPBL) are very interesting because they probe the jet formation and emission processes at the lowest levels of accretion. However, they are difficult to identify since their emission is swamped by the radiation from the host galaxy in most observing bands. In this paper we propose a new LPBL selection method based on the mid-infrared emission, in addition to the traditional optical indices. We considered the radio-selected sample of Best & Heckman (2012, MNRAS, 421, 1569 and cross-matched it with the WISE all-sky survey. In a new diagnostic plane including the W2−W3 color and the Dn(4000) index, LPBL are located in a region scarcely populated by other sources. By filtering objects with small emission line equivalent width, we isolated 36 LPBL candidates up to redshift 0.15. Their radio luminosity at 1.4 GHz spans the range log L r = 39.2−41.5 [erg s−1 ]. Considering the completeness of our sample, we analyzed the BL Lac luminosity function (RLF), finding a dramatic paucity of LPBL with respect to the extrapolation of the RLF toward low power. This requires a break in the RLF located at log L r ∼ 40.6 [erg s−1 ]. The consequent peak in the BL Lacs number density is possibly the manifestation of a minimum power required to launch a relativistic jet.

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Looking below the floor: constraints on the AGN radio luminosity functions at low power

Cited by 6 publications

References 28 publications

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

The faint radio sky: radio astronomy becomes mainstream

Looking for the least luminous BL Lacertae objects

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