One of the main debated astrophysical problems is the role of the AGN feedback in galaxy formation. It is known that massive black holes have a profound effect on the formation and evolution of galaxies, but how black holes and galaxies communicate is still an unsolved problem. For Radio Galaxies, feedback studies have mainly focused on jet/cavity systems in the most massive and X-ray luminous galaxy clusters. The recent high-resolution detection of warm absorbers in some Broad Line Radio Galaxies allow us to investigate the interplay between the nuclear engine and the surrounding medium from a different perspective. We report on the detection of warm absorbers in two Broad Line Radio Galaxies, 3C 382 and 3C 390.3, and discuss the physical and energetic properties of the absorbing gas. Finally, we attempt a comparison between radio-loud and radio-quiet outflows.
In the last few years, high-resolution X-ray spectroscopy has made progress in the exploration of the circumnuclear environment of radio-loud (RL) AGNs. While the presence of X-ray emitting and absorbing gas is well established in Seyfert galaxies, for RL sources the investigation of the nuclear environment through this technique is very recent. Specifically, in Broad Line Radio Galaxies (BLRG), the RL counterpart of Seyfert 1s, the detection of warm absorbers (WA) a was expected to be more difficult because of their small number in the local Universe and because the Doppler amplification of the jet emission could mask the absorption features. However, steps forward have been recently made thanks to high-resolution X-ray spectroscopy. Here we summarize the results concerning the discovery of WAs in two BLRGs, 3C 382 and 3C 390.3.
We analyzed all the XMM-Newton/Reflection Grating Spectrometer (RGS) data available for both 3C 382 and 3C 390.3 1-2 . Two different photoionization codes (XSTAR 3 and xabs in SPEX 4 ) have been used to model the absorption features (Fig. 1) and to derive the physical parameters of the outflow, i.e. column density, ionization parameter b and outflow velocity. The absorbing gas is highly ionized in both sources with logξ >2 erg cm s -1 , column densities varying in the range N H =10 20-22 cm -2 and outflow velocities v out ∼10 2-3 km s -1 . These slow velocities constrain the location of such gas between the torus and the NLR, favoring the torus wind scenario 5-6 .
a With the term “warm absorber” we intend ionized outflowing gas in our line-of-sight that produces narrow absorption lines in the soft X-ray spectrum.
b ξ= L neR 2 , L is the 1-1000 Rydberg (Ry) source ionizing luminosity (corresponding to 13.6 eV-13.6 keV), ne is the electron density of the gas and R is the distance of the gas from the central source. The mass outflow rate ( Ṁout ) estimates the mass carried out of the AGN through the wind c , while the WA kinetic energy ( Ėout ) is the power released in the circumnuclear environment through the outflow d . P jet e is the jet kinetic power calculated according to the formula of Ref. 7. Note that considering C v =1, the mass outflow rates are implausibly higher than the mass accretion rates, implying a clumpy configuration of the gas (C v <1). Indeed, assuming for our sources that the same amount of matter is accreted and ejected in the form of wind, we can deduce a volume filling factor as small as ∼0.01. Moreover, from Table 1 it is evident that the kinetic luminosity related to these slow outflows is a negligible fraction («1%) of both bolometric luminosity and jet kinetic power.
Aware of the scarcity of RL sources with WAs, we attempt a comparison between their X-ray properties with a sample of type 1 RQ AGNs (Seyfert 1s, NLS1s, QSOs) having a good modeling of the absorption features 6 . Again, fixing C v =1 the mass outflow rates have implausibly large values in both RL and RQ objects, independently of their radio power. Also the kinetic luminosity related to the slow outflows is negligible with respect to the accretion luminosity. Finally, in order to investigate the role of the relativistic jet we explore a possible correlation between the mass outflow rate and the radio-loudness parameter (R) f . Looking at Fig. 2 a possible positive correlation between Ṁout and R can be observed. This trend could suggest a different distribution of the gas in RL and RQ sources, tending to preferentially clump when the system is less perturbed by the jet. Alternatively, if the geometry of the gas is similar in both classes, such trend could indicate that larger amount of mass escapes from the central engine when a powerful jet is present.
, the solid angle is set to Ω=2.1, while the volume filling factor (Cv) is kept equal to 1. ] as proposed by Ref. 9.
We report on the detection of WAs in two BLRGs, 3C 382 and 3C 390.3, and discuss the physical and energetic properties of the absorbing gas: (i) the outflows are highly ionized (logξ >2 erg cm s -1 ) and slow, with velocities ranging between 10 2 -10 3 km s -1 ; (ii) the mass outflow rates are higher than the mass accretion rates if a volume filling factor (C v ) equal to 1 is assumed. Therefore a gas clumpy configuration (C v <1) is expected; (iii) the kinetic luminosity associated to these slow outflows is always lower than the accretion luminosity and the jet kinetic power; (iv) although RL and RQ WA physical properties appear very similar, at least at zeroth order, the mass outflow rate and the radio-loudness parameter (R) seem to be correlated. This correlation could indicate a different gas distribution or alternatively, if the gas distribution is the same, powerful jets could favor the escape of more massive winds.
E. Torresi, P. Grandi, E. Costantini, G.G.C. Palumbo
Jets and outflows in Radio Galaxies: implications for AGN feedback 3
E. Torresi, P. Grandi, E. Costantini, G.G.C. Palumbo
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