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Register a new userMutiwavelength Observations of Radio Galaxy 3C 120 with XMM-Newton
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P. M. Ogle
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We present XMM-Newton observations of the radio galaxy 3C 120. The hard X-ray spectrum contains a marginally resolved Fe I K-alpha emission line with FWHM=9,000 km/s and an equivalent width of 57 eV. The line arises via fluorescence in a broad-line region with covering fraction of 0.4. There is no evidence of relativistically broad Fe K-alpha, contrary to some previous reports. The normal equivalent widths of the X-ray and optical emission lines exclude a strongly beamed synchrotron component to the hard X-ray and optical continua. There is an excess of 0.3-2 keV soft X-ray continuum over an extrapolation of the hard X-ray power-law, which may arise in a disk corona. Analysis of an archival Chandra image shows that extended emission from the jet and other sources contributes <3% of the total X-ray flux. A break in the X-ray spectrum below 0.6 keV indicates an excess neutral hydrogen column density of N_H=1.57 * 10^21 cm^{-2}. However, the neutral absorber must have an oxygen abundance of <1/50 of the solar value to explain the absence of an intrinsic or intervening O I edge. There is no ionized absorption in the soft X-ray spectrum, but there is a weak, narrow O VIII Ly-alpha emission line. We do not detect previously claimed O VIII absorption from the intervening intergalactic medium. Radio observations at 37 GHz show a fast, high frequency flare starting 8 days after the XMM-Newton observation. However, this has no obvious effect on the X-ray spectrum. The X-ray spectrum, including the soft excess, became harder as the X-ray flux decreased, with an estimated pivot energy of 40 keV. The UV and soft X-ray fluxes are strongly correlated over the 120 ks duration of the XMM-Newton observation. This is qualitatively consistent with Comptonization of UV photons by a hot corona. (Abridged)
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A series of nine XMM-Newton observations of the radio-loud quasar 3C 273 are presented, concentrating mainly on the soft excess. Although most of the individual observations do not show evidence for iron emission, co-adding them reveals a weak, broad line (EW ~ 56 eV). The soft excess component is found to vary, confirming previous work, and can be well fitted with multiple blackbody components, with temperatures ranging between ~40 and ~330 eV, together with a power-law. Alternatively, a Comptonisation model also provides a good fit, with a mean electron temperature of ~350 eV, although this value is higher when the soft excess is more luminous over the 0.5-10 keV energy band. In the RGS spectrum of 3C 273, a strong detection of the OVII He-alpha absorption line at zero redshift is made; this may originate in warm gas in the local intergalactic medium, consistent with the findings of both Fang et al. (2003) and Rasmussen et al. (2003).
We present the first high signal-to-noise XMM-Newton observations of the broad-line radio galaxy 3C 411. After fitting various spectral models, an absorbed double power-law continuum and a blurred relativistic disk reflection model (kdblur) are found to be equally plausible descriptions of the data. While the softer power-law component ($Gamma$=2.11) of the double power-law model is entirely consistent with that found in Seyfert galaxies (and hence likely originates from a disk corona), the additional power law component is very hard ($Gamma$=1.05); amongst the AGN zoo, only flat-spectrum radio quasars have such hard spectra. Together with the very flat radio-spectrum displayed by this source, we suggest that it should instead be classified as a FSRQ. This leads to potential discrepancies regarding the jet inclination angle, with the radio morphology suggesting a large jet inclination but the FSRQ classification suggesting small inclinations. The kdblur model predicts an inner disk radius of at most 20 r$_g$ and relativistic reflection.
We report the results of monitoring of the radio galaxy 3C 120 with the Neil Gehrels Swift Observatory, Very Long Baseline Array, and Metsahovi Radio Observatory. The UV-optical continuum spectrum and R-band polarization can be explained by a superposition of an inverted-spectrum source with a synchrotron component containing a disordered magnetic field. The UV-optical and X-ray light curves include dips and flares, while several superluminal knots appear in the parsec-scale jet. The recovery time of the second dip was longer at UV-optical wavelengths, in conflict with a model in which the inner accretion disk (AD) is disrupted during a dip and then refilled from outer to inner radii. We favor an alternative scenario in which occasional polar alignments of the magnetic field in the disk and corona cause the flux dips and formation of shocks in the jet. Similar to observations of Seyfert galaxies, intra-band time lags of flux variations are longer than predicted by the standard AD model. This suggests that scattering or some other reprocessing occurs. The 37 GHz light curve is well correlated with the optical-UV variations, with a ~20-day delay. A radio flare in the jet occurred in a superluminal knot 0.14 milliarcseconds downstream of the 43 GHz core, which places the site of the preceding X-ray/UV/optical flare within the core 0.5-1.3 pc from the black hole. The inverted UV-optical flare spectrum can be explained by a nearly mono-energetic electron distribution with energy similar to the minimum energy inferred in the TeV gamma-ray emitting regions of some BL Lacertae objects.
We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray, optical, and radio wave bands, as well as imaging with the Very Long Baseline Array (VLBA). Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries. These findings provide support for the paradigm that black hole X-ray binaries and active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central black hole. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the emitting regions from the central BH.
We present the spectral analysis of a 200~ks observation of the broad-line radio galaxy 3C~120 performed with the high energy transmission grating (HETG) spectrometer on board the emph{Chandra} X-ray Observatory. We find (i) a neutral absorption component intrinsic to the source with column density of $text{log}N_H = 20.67pm0.05$~cm$^{-2}$, (ii) no evidence for a warm absorber with an upper limit on the column density of just $text{log}N_H < 19.7$~cm$^{-2}$ assuming the typical ionization parameter log$xi$$simeq$2.5~erg~s$^{-1}$~cm, the warm absorber may instead be replaced by (iii) a hot emitting gas with temperature $kT simeq 0.7$~keV observed as soft X-ray emission from ionized Fe L-shell lines which may originate from a kpc scale shocked bubble inflated by the AGN wind or jet with a shock velocity of about 1,000~km~s$^{-1}$ determined by the emission line width, (iv) a neutral Fe K$alpha$ line and accompanying emission lines indicative of a Compton-thick cold reflector with low reflection fraction $Rsimeq0.2$, suggesting a large opening angle of the torus, (v) a highly ionized Fe~XXV emission feature indicative of photoionized gas with ionization parameter log$xi$$=$$3.75^{+0.27}_{-0.38}$~erg~s$^{-1}$~cm and a column density of $text{log}N_H > 22$~cm$^{-2}$ localized within $sim$2~pc from the X-ray source, and (vi) possible signatures for a highly ionized disk wind. Together with previous evidence for intense molecular line emission, these results indicate that 3C~120 is likely a late state merger undergoing strong AGN feedback.
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