Mid-Infrared Spectra of High-Redshift (
                    <i>z</i>
                    &gt; 2) Radio Galaxies

Seymour, N.; Ogle, Patrick; Breuck, C. De; Fazio, G. G.; Galametz, A.; Haas, Mary E.; Lacy, Mark; Sajina, Anna; Stern, Daniel; Willner, S. P.; Vernet, J.

doi:10.1086/590081

Cited by 28 publications

(46 citation statements)

References 33 publications

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“…This conversion factor to the bolometric luminosity can vary from 1.4 to 15 for the IR (see Appendix C). Assuming the full unobscured AGN 10 The L IR SB and SFR from our SED decomposition are also compatible with the previous estimates based on the IRS spectra Seymour et al (2008) and Rawlings et al (2013).…”

Section: Black Hole Accretion Ratesupporting

confidence: 86%

“…It is also interesting to note that the extreme object 4C 23.56 represents the prototype of a pure AGN contribution, and is remarkably well reproduced by the built-in template. Part of our sample (seven objects) have IRS spectra (12-24 µm) available (Seymour et al 2008;Rawlings et al 2013). Overplotting the spectrum after the fitting shows a good agreement between the IRS and the results.…”

Section: Transition Regime: Hot Starburst or Cold Agn?mentioning

confidence: 61%

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Rapidly growing black holes and host galaxies in the distant Universe from theHerschelRadio Galaxy Evolution Project

Drouart

Breuck

Vernet

et al. 2014

A&A

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110

189

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We present results from a comprehensive survey of 70 radio galaxies at redshifts 1 < z < 5.2 using the PACS and SPIRE instruments on board the Herschel Space Observatory. Combined with existing mid-IR photometry from the Spitzer Space Telescope, published 870 µm photometry, and new observations obtained with LABOCA on the APEX telescope, the spectral energy distributions (SEDs) of galaxies in our sample are continuously covered across 3.6-870 µm. The total 8-1000 µm restframe infrared luminosities of these radio galaxies are such that almost all of them are either ultra-(L IR tot > 10 12 L ) or hyper-luminous (L IR tot > 10 13 L ) infrared galaxies. We fit the infrared SEDs with a set of empirical templates which represent dust heated by a variety of starbursts (SB) and by an active galactic nucleus (AGN). We find that the SEDs of radio galaxies require the dust to be heated by both AGN and SB, but the luminosities of these two components are not strongly correlated. Assuming empirical relations and simple physical assumptions, we calculate the star formation rate (SFR), the black hole mass accretion rate (Ṁ BH ), and the black hole mass (M BH ) for each radio galaxy. We find that the host galaxies and their black holes are growing extremely rapidly, having SFR ≈ 100-5000 M yr −1 anḋ M BH ≈ 1-100 M yr −1 . The mean specific SFRs (sSFR) of radio galaxies at z > 2.5 are higher than the sSFR of typical star forming galaxies over the same redshift range, but are similar or perhaps lower than the galaxy population for radio galaxies at z < 2.5. By comparing the sSFR and the specificṀ BH (sṀ BH ), we conclude that black holes in radio loud AGN are already, or soon will be, overly massive compared to their host galaxies in terms of expectations from the local M BH -M Gal relation. In order to catch up with the black hole, the galaxies require about an order of magnitude more time to grow in mass at the observed SFRs compared to the time the black hole is actively accreting. However, during the current cycle of activity, we argue that this catching up is likely to be difficult because of the short gas depletion times. Finally, we speculate on how the host galaxies might grow sufficiently in stellar mass to ultimately fall onto the local M BH -M Gal relation.

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Section: Black Hole Accretion Ratesupporting

confidence: 86%

Section: Transition Regime: Hot Starburst or Cold Agn?mentioning

confidence: 61%

Rapidly growing black holes and host galaxies in the distant Universe from theHerschelRadio Galaxy Evolution Project

Drouart

Breuck

Vernet

et al. 2014

A&A

Self Cite

110

189

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“…To keep our study as homogeneous as possible, we focus only on the part of the SED below the silicate feature (<10 μm), which is dominated by AGN heated dust emission (see below). Mid-IR spectroscopy with IRS (Seymour et al 2008;Leipski et al 2010;Rawlings et al, in prep. ) shows that PAH features are either not detected or weak relative to the AGN emission.…”

Section: Contributions To the Infrared Sedmentioning

confidence: 99%

Jet and torus orientations in high redshift radio galaxies

Drouart

Breuck

Vernet

et al. 2012

A&A

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We examine the relative orientation of radio jets and dusty tori surrounding the active galactic nucleus (AGN) in powerful radio galaxies at z > 1. The radio core dominance R = P 20 GHz core /P 500 MHz extended serves as an orientation indicator, measuring the ratio between the anisotropic Doppler-beamed core emission and the isotropic lobe emission. Assuming a fixed cylindrical geometry for the hot, dusty torus, we derive its inclination i by fitting optically-thick radiative transfer models to spectral energy distributions obtained with the Spitzer Space Telescope. We find a highly significant anti-correlation (p < 0.0001) between R and i in our sample of 35 type 2 AGN combined with a sample of 18 z ∼ 1 3CR sources containing both type 1 and 2 AGN. This analysis provides observational evidence both for the Unified scheme of AGN and for the common assumption that radio jets are in general perpendicular to the plane of the torus. The use of inclinations derived from mid-infrared photometry breaks several degeneracies which have been problematic in earlier analyses. We illustrate this by deriving the core Lorentz factor Γ from the R-i anti-correlation, finding Γ > ∼ 1.3.

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“…Hines & Wills 1993;Piconcelli et al 2007a) and 4C 23.56 8 (empty triangle, z = 2.48; e.g. Johnson et al 2006;Seymour et al 2008). Sources absorbed by a column density of Log(N H ) ≥ 24 cm −2 are marked with empty squares.…”

Section: Mir Luminosity Versus Hard X-ray Luminositymentioning

confidence: 99%

Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios

Lanzuisi

Piconcelli²,

Fiore³

et al. 2009

A&A

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Recent works have suggested that selection criteria based on mid-IR properties, i.e. extreme colors and bright flux levels, can be used to reveal a population of dust-enshrouded, extremely-luminous quasars at z ∼ 1-2. However, the X-ray spectral properties of these intriguing objects still remain largely unexplored. We have performed an X-ray study of a large sample of bright mid-IR (F 24 μm > 1.3 mJy) galaxies showing an extreme MIR/Optical flux ratio (F 24 μm /F R > 2000) in order to confirm the presence of a luminous active nucleus in these very red objects. Sampling of a large area is required to pick up objects at the highest luminosities given their low surface density. Accordingly, we have applied our selection criteria to an area of ∼6 deg 2 covered by XMM-Newton/Chandra observations within the ∼50 deg 2 SWIRE survey, resulting in a final sample of 44 objects. The vast majority of the source redshifts, both spectroscopic and photometric, are in the range 0.7 < ∼ z < ∼ 2.5. The X-ray coverage of the sample is highly inhomogeneous (from snap-shot 5 ks Chandra observations to medium-deep XMM-Newton exposures of 70 ks) and, consequently, a sizable fraction of them (≈43%) remains undetected in the 0.5-10 keV band. Using spectral or hardness information we were able to estimate the value of the absorbing column density in 23 sources. 95% of them are consistent with being obscured by neutral gas with an intrinsic column density of N H ≥ 10 22 cm −2 . Remarkably, we also find that ∼55% of these sources can be classified as type 2 quasars on the basis of their absorption properties and X-ray luminosity. Moreover, most of the X-ray undetected sources show extreme mid-IR colors, consistent with being luminous AGN-powered objects, suggesting they might host heavily obscured (possibly Compton-thick) quasars in X-rays. This demonstrates that our selection criteria applied to a wide area survey is very efficient in finding a large number of type 2 quasars at z > ∼ 1. The existence of this class of very powerful, obscured quasars at high z could have important implications in the context of the formation and cosmological evolution of accreting supermassive black holes and their host galaxies.

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Mid-Infrared Spectra of High-Redshift ( z > 2) Radio Galaxies

Cited by 28 publications

References 33 publications

Rapidly growing black holes and host galaxies in the distant Universe from theHerschelRadio Galaxy Evolution Project

Rapidly growing black holes and host galaxies in the distant Universe from theHerschelRadio Galaxy Evolution Project

Jet and torus orientations in high redshift radio galaxies

Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratios

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