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Register a new userThe Nature of Soft Excess in ESO 362-G18 Revealed by XMM-Newton and NuSTAR Spectroscopy
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We present a detailed spectral analysis of the joint XMM-Newton and NuSTAR observations of the active galactic nuclei (AGN) in the Seyfert 1.5 Galaxy ESO 362-G18. The broadband ($0.3mbox{--}79$ keV) spectrum shows the presence of a power-law continuum with a soft excess below $2$ keV, iron K$alpha$ emission ($sim 6.4$ keV), and a Compton hump (peaking at $sim 20$ keV). We find that the soft excess can be modeled by two different possible scenarios: a warm ($kT_mathrm{e}sim0.2$ keV) and optically thick ($tausim34$) Comptonizing corona; or with relativistically-blurred reflection off a high-density ($log{[n_mathrm{e}/mathrm{cm}^{-3}]}>18.3$) inner disk. These two models cannot be easily distinguished solely from their fit statistics. However, the low temperature ($kT_mathrm{e}sim20$ keV) and the thick optical depth ($tausim5$) of the hot corona required by the warm corona scenario are uncommon for AGNs. We also fit a hybrid model, which includes both disk reflection and a warm corona. Unsurprisingly, as this is the most complex of the models considered, this provides the best fit, and more reasonable coronal parameters. In this case, the majority of the soft excess flux arises in the warm corona component. However, based on recent simulations of warm coronae, it is not clear whether such a structure can really exist at the low accretion rates relevant for ESO 362-G18 ($dot{m}sim0.015$). This may therefore argue in favor of a scenario in which the soft excess is instead dominated by the relativistic reflection. Based on this model, we find that the data would require a compact hot corona ($hsim3,R_mathrm{Horizon}$) around a highly spinning ($a_star>0.927$) black hole.
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We present two-dimensional stellar and gaseous kinematics of the inner 0.7 $times$ 1.2 kpc$^{2}$ of the Seyfert galaxy ESO 362-G18, derived from optical spectra obtained with the GMOS/IFU on the Gemini South telescope at a spatial resolution of $approx$170 pc and spectral resolution of 36 km s$^{-1}$. ESO 362-G18 is a strongly perturbed galaxy of morphological type Sa or S0/a, with a minor merger approaching along the NE direction. Previous studies have shown that the [OIII] emission shows a fan-shaped extension of $approx$ 10arcsec to the SE. We detect the [OIII] doublet, [NII] and H${alpha}$ emission lines throughout our field of view. The stellar kinematics is dominated by circular motions in the galaxy plane, with a kinematic position angle of $approx$137$^{circ}$. The gas kinematics is also dominated by rotation, with kinematic position angles ranging from 122$^{circ}$ to 139$^{circ}$. A double-Gaussian fit to the [OIII]$lambda$5007 and H${alpha}$ lines, which have the highest signal to noise ratios of the emission lines, reveal two kinematic components: (1) a component at lower radial velocities which we interpret as gas rotating in the galactic disk; and (2) a component with line of sight velocities 100-250 km s$^{-1}$ higher than the systemic velocity, interpreted as originating in the outflowing gas within the AGN ionization cone. We estimate a mass outflow rate of 7.4 $times$ 10$^{-2}$ M$_{odot}$ yr$^{-1}$ in the SE ionization cone (this rate doubles if we assume a biconical configuration), and a mass accretion rate on the supermassive black hole (SMBH) of 2.2 $times$ 10$^{-2}$ M$_{odot}$ yr$^{-1}$. The total ionized gas mass within $sim$84 pc of the nucleus is 3.3 $times$ 10$^{5}$ M$_{odot}$; infall velocities of $sim$34 km s$^{-1}$ in this gas would be required to feed both the outflow and SMBH accretion.
XMM-Newton and NuSTAR multiple exposures allow us to disentangle the different emission components of active galactic nuclei (AGNs) and to study the evolution of their different spectral features. In this work, we present the timing and spectral properties of five simultaneous XMM-Newton and NuSTAR observations of the Narrow Line Seyfert 1 galaxy Mrk 359. We aim to provide the first broadband spectral modeling of Mrk 359 describing its emission spectrum from the UV up to the hard X-rays. To do this, we performed temporal and spectral data analysis, characterising the amplitude and spectral changes of the Mrk 359 time series and computing the 2-10 keV normalised excess variance. The spectral broadband modelling assumes the standard hot Comptonising corona and reflection component, while for the soft excess we tested two different models: a warm, optically thick Comptonising corona (the two-corona model) and a reflection model in which the soft-excess is the result of a blurred reflected continuum and line emission (the reflection model). High and low flux states were observed during the campaign. The former state has a softer spectral shape, while the latter shows a harder one. The photon index is in the 1.75-1.89 range, and only a lower limit to the hot-corona electron temperature can be found. A constant reflection component, likely associated with distant matter, is observed. Regarding the soft excess, we found that among the reflection models we tested, the one providing the better fit (reduced $chi^2$=1.14) is the high-density one. However, a significantly better fit (reduced $chi^2$=1.08) is found by modelling the soft excess with a warm Comptonisation model. The present analysis suggests the two-corona model as the best scenario for the optical-UV to X-ray emission spectrum of Mrk 359.
We have extensively studied the broadband X-ray spectra of the source ESO~141--G055 using all available xmm{} and ustar{} observations. We detect a prominent soft excess below 2 keV, a narrow Fe line and a Compton hump (>10 keV). The origin of the soft excess is still debated. We used two models to describe the soft excess: the blurred reflection from the ionized accretion disk and the intrinsic thermal Comptonisation model. We find that both of these models explain the soft excess equally well. We confirm that we do not detect any broad Fe line in the X-ray spectra of this source, although both the physical models prefer a maximally spinning black hole scenario (a$>$0.96). This may mean that either the broad Fe line is absent or blurred beyond detection. The Eddington rate of the source is estimated to be $lambda_{Edd} sim 0.31$. In the reflection model, the Compton hump has a contribution from both ionized and neutral reflection components. The neutral reflector which simultaneously describes the narrow Fe K$alpha$ and the Compton hump has a column density of $rm N_{H} geq 7times 10^{24} rm cm^{-2} $. In addition, we detect a partially covering ionized absorption with ionization parameter $log xi/rm erg cm s^{-1}$ = $0.1^{+0.1}_{-0.1}$ and column density $rm N_{H} =20.6^{+1.0}_{-1.0}times 10^{22} rm cm^{-2}$ with a covering factor of $0.21^{+0.01}_{-0.01}$.
We present simultaneous XMM-Newton and NuSTAR observations of the `bare Seyfert 1 galaxy, Ark 120, a system in which ionized absorption is absent. The NuSTAR hard X-ray spectral coverage allows us to constrain different models for the excess soft X-ray emission. Among phenomenological models, a cutoff power law best explains the soft X-ray emission. This model likely corresponds to Comptonization of the accretion disk seed UV photons by a population of warm electrons: using Comptonization models, a temperature of ~0.3 keV and an optical depth of ~13 are found. If the UV-to-X-ray optxagnf model is applied, the UV fluxes from the XMM-$Newton$ Optical Monitor suggest an intermediate black hole spin. Contrary to several other sources observed by NuSTAR, no high energy cutoff is detected, with a lower limit of 190 keV.
MCG-6-30-15, at a distance of 37 Mpc (z=0.008), is the archetypical Seyfert 1 galaxy showing very broad Fe K$alpha$ emission. We present results from a joint NuSTAR and XMM-Newton observational campaign that, for the first time, allows a sensitive, time-resolved spectral analysis from 0.35 keV up to 80 keV. The strong variability of the source is best explained in terms of intrinsic X-ray flux variations and in the context of the light bending model: the primary, variable emission is reprocessed by the accretion disk, which produces secondary, less variable, reflected emission. The broad Fe K$alpha$ profile is, as usual for this source, well explained by relativistic effects occurring in the innermost regions of the accretion disk around a rapidly rotating black hole. We also discuss the alternative model in which the broadening of the Fe K$alpha$ is due to the complex nature of the circumnuclear absorbing structure. Even if this model cannot be ruled out, it is disfavored on statistical grounds. We also detected an occultation event likely caused by BLR clouds crossing the line of sight.
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