Jet and torus orientations in high redshift radio galaxies

et al. 2016

A&A

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Most successful galaxy formation scenarios now postulate that the intense star formation in massive, high-redshift galaxies during their major growth period was truncated when powerful AGNs launched galaxy-wide outflows of gas that removed large parts of the interstellar medium. SINFONI imaging spectroscopy of the most powerful radio galaxies at z ∼ 2 show clear signatures of such winds, but are too rare to be good representatives of a generic phase in the evolution of all massive galaxies at high redshift. Here we present SINFONI imaging spectroscopy of the rest-frame optical emission-line gas in 12 radio galaxies at redshifts ∼2. Our sample spans a range in radio power that is intermediate between the most powerful radio galaxies with known wind signatures at these redshifts and vigorous starburst galaxies, and are about two orders of magnitude more common than the most powerful radio galaxies. Thus, if AGN feedback is a generic phase of massive galaxy evolution for reasonable values of the AGN duty cycle, these are just the sources where AGN feedback should be most important. Our sources show a diverse set of gas kinematics ranging from regular velocity gradients with amplitudes of Δv = 200−400 km s −1 consistent with rotating disks to very irregular kinematics with multiple velocity jumps of a few 100 km s −1 . Line widths are generally high, typically around FWHM = 800 km s −1 , more similar to the more powerful high-z radio galaxies than mass-selected samples of massive high-z galaxies without bright AGNs, and consistent with the velocity range expected from recent hydrodynamic models. A broad Hα line in one target implies a black hole mass of a few 10 9 M . Velocity offsets of putative satellite galaxies near a few targets suggest dynamical masses of a few 10 11 M for our sources, akin to the most powerful high-z radio galaxies. Ionized gas masses are 1−2 orders of magnitude lower than in the most powerful radio galaxies, and the extinction in the gas is relatively low, up to A V ∼ 2 mag. The ratio of line widths, σ, to bulk velocity, v, is so large that even the gas in galaxies with regular velocity fields is unlikely to be gravitationally bound. It is unclear, however, whether the large line widths are due to turbulence or unresolved, local outflows as are sometimes observed at low redshifts. We compare our sources with sets of radio galaxies at low and high redshift, finding that they may have more in common with gas-rich nearby radio galaxies with similar jet power than with the most powerful high-z radio galaxies. Comparison of the kinetic energy with the energy supply from the AGNs through jet and radiation pressure suggests that the radio source still plays a dominant role for feedback, consistent with low-redshift radio-loud quasars.

Section: Outflows or Disk Rotation?supporting

confidence: 87%

Kinematic signatures of AGN feedback in moderately powerful radio galaxies atz~ 2 observed with SINFONI

Collet

Nesvadba

et al. 2016

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“…Nonetheless, this quantity is not expected to be important, as we are dealing with Type 2 AGN, i.e. mostly oriented in the plane of the sky (Drouart et al 2012). The real size D will likely be at most 30% larger because of projection effects.…”

Section: Radio Sizesmentioning

confidence: 99%

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

Drouart

Vernet

et al. 2014

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109

189

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.

“…An edge-on view corresponds to i = 90 • , and i = 0 • , corresponds to a face-on view. The opening angle, θ, was set to θ = 40 • , as suggested by previous studies (e.g., Barthel 1989;Drouart et al 2012). In practice, all inclinations i < 50 • present a line of sight free of dust and therefore similar SEDs.…”

Section: Agn Model and Librarymentioning

confidence: 99%

Disentangling star formation and AGN activity in powerful infrared luminous radio galaxies at 1 <z< 4

Drouart

Rocca‐Volmerange

et al. 2016

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High-redshift radio galaxies present signs of both star formation and AGN activity, making them ideal candidates to investigate the connection and coevolution of AGN and star formation in the progenitors of present-day massive galaxies. We make use of a sample of 11 powerful radio galaxies spanning 1 < z < 4 which have complete coverage of their spectral energy distribution (SED) from UV to FIR wavelengths. Using Herschel data, we disentangle the relative contribution of the AGN and star formation by combining the galaxy evolution code PÉGASE.3 with an AGN torus model. We find that three components are necessary to reproduce the observed SEDs: an evolved and massive stellar component, a submm bright young starburst, and an AGN torus. We find that powerful radio galaxies form at very high-redshift, but experience episodic and important growth at 1 < z < 4 as the mass of the associated starburst varies from 5 to 50% of the total mass of the system. The properties of star formation differ from source to source, indicating no general trend of the star formation properties in the most infrared luminous high-redshift radio galaxies and no correlation with the AGN bolometric luminosity. Moreover, we find that AGN scattered light have a very limited impact on broad-band SED fitting on our sample. Finally, our analysis also suggests a wide range in origins for the observed star formation,which we partially constrain for some sources.