On the Origin of the X-Ray Emission in Heavily Obscured Compact Radio Sources

X-ray continuum emission of active galactic nuclei (AGNs) may be reflected by circumnuclear dusty tori, producing prominent fluorescence iron lines at X-ray frequencies. Here, we discuss the broadband emission of three radio-loud AGNs belonging to the class of compact symmetric objects (CSOs), with detected narrow Fe Kα lines. CSOs have newly born radio jets, forming compact radio lobes with projected linear sizes of the order of a few to hundreds of parsecs. We model the radio-to-γ-ray spectra of compact lobes in J1407+2827, J1511+0518, and J2022+6137, which are among the nearest and the youngest CSOs known to date, and are characterized by an intrinsic X-ray absorbing column density of N H > 1023 cm−2. In addition to the archival data, we analyze the newly acquired Chandra X-ray Observatory and Submillimeter Array (SMA) observations, and also refine the γ-ray upper limits from Fermi Large Area Telescope monitoring. The new Chandra data exclude the presence of the extended X-ray emission components on scales larger than 1.″5. The SMA data unveil a correlation between the spectral index of the electron distribution in the lobes and N H, which can explain the γ-ray quietness of heavily obscured CSOs. Based on our modeling, we argue that the inverse-Compton emission of compact radio lobes may account for the intrinsic X-ray continuum in all these sources. Furthermore, we propose that the observed iron lines may be produced by a reflection of the lobes’ continuum from the surrounding cold dust.


INTRODUCTION
Hard X-ray emission of active galactic nuclei (AGNs) is typically associated with the presence of a corona, a hot plasma in the accretion disk vicinity, where optical/UV disk photons gain energy via the process of Comptonization (Haardt & Maraschi 1991, 1993;Svensson & Zdziarski 1994;Stern et al. 1995;Esin et al. 1997).Throughout the years, a variety of models have been discussed to describe coronas' location and structure, including a lamp post model (Esin et al. 1997;Yuan & Narayan 2004), a hot inner flow (Done & Zycki 1999;Yuan & Narayan 2014), or a jet/base of a jet (Markoff et al. 2005;Dauser et al. 2013).The X-ray continuum is often accompanied by fluorescent iron lines, which are now established as ubiquitous features in the X-ray spectra of both obscured and unobscured AGNs (e.g., Page et al. 2004;Nandra et al. 2007;Ricci et al. 2014).A narrow Fe Kα line is produced when X-ray continuum emission reflects off mater located either on the line-ofsight (e.g., in the broad line region clouds), or out of the line-of-sight, e.g., dusty torus or outer regions of an accretion disk.In the latter case, the iron line is accompanied by a Compton reflection component.(e.g., George & Fabian 1991;Matt et al. 1996;Nandra 2006;Bianchi et al. 2008;Shu et al. 2010;Gandhi et al. 2015).
In this paper, we complement the above scenarios by proposing young, compact lobes of radio galaxies and quasars as another source of AGN X-ray continuum emission.These lobes constitute a reservoir of a hot magnetized plasma back-flowing from the jet termination shock, where the jet's bulk kinetic energy is converted to the internal energy of the jet particles (e.g., Begelman & Cioffi 1989).Unlike in the case of relativistic beamed jets, the lobes' emission is isotropic in the observers' rest frame.During the earliest phases of the jet lifetime, the lobes have a size that is smaller or comparable to that of the dusty torus.Consequently, in objects where the primary X-ray continuum originates from radio lobes expanding inside or near a molecular torus, one should expect to observe X-ray reflection and fluorescence features, such as the Fe Kα line.
With this picture in mind, we model the broadband spectral energy distributions (SEDs) of three objects: J1407+2827 (also known as OQ+208 or Mrk 668), J1511+0518, and J2022+6137 (2021+614), to quantitatively explore the validity of the above expectation.These objects were selected from a sample of compact symmetric objects (CSOs, a subset of AGNs known for their compact, young radio structures, see e.g., O'Dea 1998;O'Dea & Saikia 2021;Kiehlmann et al. 2024a,b;Readhead et al. 2024) considered in Sobolewska et al. (2019a) based on their distinctive X-ray spectral features derived based on extensive observations by Chandra, XMM-Newton, and NuSTAR (see Sobolewska et al. 2019b;Sobolewska et al. 2023, further denoted as S19 and S23 respectively).Key features are a high intrinsic X-ray absorption (equivalent hydrogen column densities, N H > 10 23 cm −2 ), as well as a narrow fluorescent Fe Kα line and the broad Compton reflection component indicating a reflection from a toroidal obscurer.Such properties make the selected targets rare examples of "radio-loud/X-ray-obscured" AGNs (see Panessa et al. 2016;LaMassa et al. 2023).
The observed radio morphology of these sources, at the milliarcsecond scale, comprises a weak compact core and symmetric lobes, with the innermost projected linear sizes within the 7-25 pc range (An & Baan 2012).These sizes are comparable to the radii of dusty molecular tori in nearby Seyfert galaxies, as measured by the Atacama Large Millimeter Array (ALMA) (Combes et al. 2019;García-Burillo et al. 2021).The integrated radio spectra display spectral turnovers at GHz frequencies, suggesting excess absorption in the lobes' radio continuum emission (Wójtowicz et al. 2020;Kiehlmann et al. 2024a).Additionally, the mid-infrared colors of these sources, as measured by the Wide-field Infrared Survey Explorer (WISE), place them in the "AGN" classification meaning that their observed radiative output at the µm range is indeed dominated by the circumnuclear dust, typical for quasars and luminous Seyfert galaxies (see Kosmaczewski et al. 2020;Nascimento et al. 2022).
To investigate the potential of radio lobes as a source of X-ray continuum in the above mentioned CSOs, we constructed and then modeled the broadband SED using archival radio, infrared (IR), optical/UV, and Xray data.Additionally, we incorporated recent submillimeter data collected with the SMA.Finally, we revisit the Fermi-LAT data, which indicate that our three CSOs are γ-ray-quiet (Principe et al. 2020), and derive γ-ray upper limits based on 14 years of LAT monitoring.Our modeling approach employs a simple dy-namical description of the expanding lobes in young radio sources.The lobes' X-ray emission is produced via inverse-Compton (IC) scattering of various soft photon fields -predominantly those emitted by accretion disks and dusty tori -by ultra-relativistic electrons injected by the jets into evolving compact lobes.All relevant energy losses of the radiating elctrons are taken into account and integrated over the entire lifetime of the source (Stawarz et al. 2008, further referenced as LS08).We show that in the case of all three sources X-ray emission can be successfully modeled within this scenario.
In addition, we present the new X-ray data collected with Chandra for J1511+0518.These new data enable us to perform an image analysis of the source and investigate the presence of an extended X-ray emission on scales larger than 1.5 ′′ (∼ 2.4 kpc).Let us note that, in contrast to our heavily X-ray absorbed γ-ray quiet CSOs, the three γ-ray loud CSOs detected to date with Fermi-LAT are unobscured in X-rays.These include PKS 1718-649 (Migliori et al. 2016;Siemiginowska et al. 2016), TXS 0128+554 (Lister et al. 2020), andNGC 3894 (Principe et al. 2020;Balasubramaniam et al. 2021), with the observed (isotropic) γ-ray luminosities L 0.1−1,000 GeV ≃ 1 × 10 42 erg s −1 , 2 × 10 43 erg s −1 , and 6 × 10 41 erg s −1 , respectively (Principe et al. 2021).We also note that the X-ray emission extended beyond the innermost 1.5 ′′ nuclear region from the radio source position has been detected around two of three γ-ray-loud CSOs (PKS 1718-649 and NGC 3894, see details in Siemiginowska et al. 2016;Beuchert et al. 2018;Balasubramaniam et al. 2021, respectively).In both sources, this emission has been modeled as originating from a collisionally ionized plasma with temperatures of ∼ (0.7 − 0.8) keV, possibly with an additional photoionized plasma component in PKS 1718-649 (Beuchert et al. 2018).
To date, no extended X-ray emission has been spatially resolved around the other two heavily obscured CSOs, as discussed in S19 for J1407+2827 and in Siemiginowska et al. (2016) for J2022+6137.The low number of counts in the archival 2 ks Chandra observation of J1511+0518 did not allow for a meaningful spatial analysis.However, S23 pointed out that including a thermal plasma component with a temperature ∼ 1 keV could alleviate the residuals in the soft range of the XMM-Newton and NuSTAR joint spectrum.Since the spatial resolution of the XMM-Newton data was insufficient to determine whether this thermal emission originated within the unresolved AGN region or on scales exceeding several kpc, we reobserved J1511+0518 with Chandra to perform an image analysis of this source and investigate the presence of the extended emission.Here we show, that in the new 55 ks Chandra observation we do not detect any extended emission.
This paper is organized as follows.In Section 2, we analyze the new Chandra data for J1511+0518, and show that the X-ray emission of this source is unresolved on arcsec scales.In Section 3, we describe the multiwavelength data used to build the broadband SEDs of J1407+2827, J1511+0518, and J2022+6137.In Section 4 we briefly summarize the applied radiative model for expanding radio lobes, and delineate the modeling procedure.We present our modeling results in Section 5.The main findings derived from the analysis are discussed further in Section 6, and summarized in Section 7.

CHANDRA OBSERVATIONS OF J1511+0518
We analyzed the recent (May 2022) observations of J1511+0518 with the Chandra's Advanced CCD Imaging Spectrometer (ACIS), consisting of three separate pointings summarized in Table 1.
We used the standard procedures to reduce the data with CIAO v4.14 (Fruscione et al. 2006), starting with the reprocessing performed with the chandra repro script.The astrometry correction was carried out with respect to the longest observation, ObsID 25457, with the wavdetect, wcs match, and wcs update scripts.We modeled the Chandra spectra of J1511+0518 using Sherpa (Freeman et al. 2001), and the modeling details are described in Section 2.1.Next, we used the best fitting spectral model as an input to the point spread function (PSF) simulations of an on-axis point-like source using the ChaRT (Carter et al. 2003) and MARX (Davis et al. 2012) tools.We compared the simulated PSF with that built based on our observations to asses the presence of an extended X-ray emission on scales larger than ∼ 1.5 ′′ from the source coordinates (see Section 2.2).

Spectral Modeling
The source and background energy spectra were extracted separately for each observation of J1511+0518.We chose a circular source extraction region with the ra- dius of 5 ACIS-S pixels 1 , corresponding to ∼ 2.5 ′′ , centered at RA = 15h 11m 41.18s, Dec = +5 • 18 ′ 10 ′′ .150(J2000).For the background region, we chose a concentric ring with r in = 10 px ∼ 5 ′′ and r out = 20 px ∼ 10 ′′ , centered at the same coordinates as the source region.
The number of net source counts for each observation can be found in Table 1.We binned the spectra requiring the signal-to-noise ratio (SNR) of 3 in each bin.The maximum bin length was set to 0.2 keV.We performed a joint spectral fit of all three Chandra observations in the 0.5−7.0keV energy band in order to inform the PSF simulations performed in Section 2.2, as part of the image analysis.
Our simplified spectral model applied to the new Chandra data was based on the joint modeling of the XMM-Newton and NuSTAR data of the source by S23.In particular, our continuum model consisted of a combination of a collisionally ionized plasma, xsapec, and a non-thermal emission approximated with a simple powerlaw model.We fixed the photon index and the plasma temperature at Γ = 1.8 and kT = 1.0 keV to avoid degeneracy in the fit parameters.Additionally, our model included a Gaussian line, xszgauss, to account for the narrow Fe Kα feature reported in S23, which is also present in the new Chandra data.The rest-frame energy and the width of the line were fixed at 6.4 keV and 0.02 keV respectively.Moreover, we have included the Galactic absorption, xsphabs, with the equivalent hydrogen column density fixed at N H, Gal = 3.29 × 10 20 cm −2 (Dickey & Lockman 1990) acting on all the spectral components, and an intrinsic absorption at the redshift of the source, xszphabs, with the column density N H, z , acting exclusively on the power-law component.The final model, xsphabs × (xszphabs × powlaw1d + xsapec + xszgauss), had four free model parameters, which we linked across the three data sets (corresponding to the three separate pointings) during the fitting procedure.We obtained a satisfactory fit with the chi2gehrels2 fit statistic of 43 for 97 degrees of freedom for the source intrinsic absorbing column density N H, z = (1.28 ± 0.31) × 10 22 cm −2 , the normalization of the power-law component, N PL = (4.47 ± 0.048) × 10 −5 ph keV −1 cm −2 s −1 , the normalization of the iron line N Fe = (1.43 ± 0.69) × 10 −6 ph cm −2 s −1 , and the normalization of the thermal plasma N APEC = (4.47 ± 0.47) × 10 −19 (1 + z) 2 dV n e n H /4πD 2 L , where dV is the emission volume element, and n e and n H are the electron and hydrogen densities, respectively, all in cgs units.All the uncertainties represent 1σ confidence intervals.
The best fit model returned the 0.5 − 7.0 keV deabsorbed flux of the power-law component F 0.5−7.0keV ≃ (2.14 ± 0.14) × 10 −13 erg cm −2 s −1 , and the extrapolated 2-10 keV power-law luminosity of L 2−10 keV ∼ 2.5 × 10 42 erg s −1 ; the equivalent width of the iron line read as EW ≃ 0.72 +1.12 −0.36 keV.These values are all comparable within the errors to the corresponding parameter values obtained by S23.However, we note a difference in the complexity of the models applied therein and in our work due to a much limited energy range and pho-ton statistics of the new Chandra data when compared with the joint XMM-Newton and NuSTAR data sets.

Image Analysis
We simulated the Chandra PSF for all three pointings using the chart tool and assuming the best-fit spectral model as presented in Section 2.1 above.We repeated the simulations 50 times for each of the three observations to account for the possibility of considerable differences in each realization of the PSF due to random photon fluctuations.We used the marx software to convert the obtained rays to the pseudo-event file with default ASPECT blur 0.07.Finally, we averaged the simulation results for each observations.
We extracted all the detected counts from concentric rings defined by the difference between the outer and inner radii of ∆r int = (0.5 + n) ′′ , with n = 0, .., 4, and ∆r ext = (0.5+2n) with n = 2, ..., 7. A comparison of the resulting source brightness profile for the merged three pointings and the simulated averaged PSF is presented in Figure 1.As shown, the observed brightness profile is consistent with the emission of a point-like source within the ACIS spatial resolution, given a relatively large spread observed in various PSF realizations due to random photon fluctuations, especially at larger radii from the source coordinates (see the orange shaded area in the figure) and the additional uncertainty in the astrometry correction between the three analyzed Chandra pointings.
The lack of the extended emission component in the new Chandra data can be significantly affected by the Chandra's ACIS-S chip degradation.As the extended emission component is expected to originate from thermal hot plasma radiation, it would predominantly appear in the Chandra soft band, which is most affected by the chip degradation.In this context, it is worth noting that the Chandra observations of CSO NGC 3894, which revealed source' extended emission, were conducted during Cycle 9.The effective area of the ACIS-S chip has significantly decreased between Cycle 9 and 23, the latter being when J1511+618 was observed.Namely, in soft X-ray band has decreased by ∼ 2 orders of magnitude3 .

Sub-Millimeter Array Observations
The Submillimeter Array was utilized to observe young radio sources and flat spectrum radio quasars (FSRQs) under the SMA programs 2018A-S042 and 2018B-S037.These programs were executed multiple times to accommodate a wide range of target locations, and thus J1407+2827 was observed twice (8 August 2018 and 2 May 2019), J1511+0518 was observed twice (13 July and 8 August, 2018) and J2022+6137 was observed once (13 July 2018).For all the observations, complexvalued measurements ("visibilities") of the sources were bracketed by measurements of nearby strong radio-loud AGNs (often blazars) as amplitude and phase gain calibrators.Data reduction was performed with the SMA in-house reduction package MIR4 , including data flagging, initial system temperature calibration, removal of correlator-based amplitude spikes at specific channels, and generation of a broad-band continuum channel (8 GHz wide, in each of two sidebands).Complex gain corrections, determined from the calibrator, were applied to the target visibilities, and the flux density scale was set using a solar system standard (Callisto) and a secondary standard, MWC349a.The calibrated continuum-band visibility data were then vector averaged to determine the flux density of each source.The SMA observations and the resulting fluxes are listed in Appendix A.

Fermi-LAT Monitoring
The Large Area Telescope (LAT) is the main instrument on board the Fermi Gamma-ray Space telescope.
It is a γ-ray telescope sensitive at energies ranging from 20 MeV to more than 300 GeV (Atwood et al. 2009).
In this work, we performed a dedicated analysis of the 14 years of LAT observations (between 4 August 2008 and 4 August 2022) of the three CSOs, following the analysis technique of Principe et al. (2021).We selected P8R3 SOURCE class events (Bruel et al. 2018), in the energy range between 100 MeV and 1 TeV, from regions of interest (ROIs) of 15 • ×15 • centered at the positions of each selected source.The value of the low energy threshold is motivated by the large uncertainties in the arrival directions of the photons below 100 MeV (Principe et al. 2018), leading to a possible confusion between point-like sources and the Galactic diffuse component.
The analysis consisting of model optimization, localization, spectrum and variability study, was performed with Fermipy 5 (Wood et al. 2017), a Python package that facilitates analysis of the LAT data with the Fermi Science Tools.
We created the count maps with a pixel size of 0.1 • , and we excluded all γ-rays with zenith angle larger than 95 • in order to limit the contamination from secondary γ-rays from the Earth's limb (Abdo et al. 2009).Following the analysis technique reported in Principe et al. (2020Principe et al. ( , 2021)), we made an even harder cut at low energies (< 300 MeV) by reducing the maximum zenith angle (< 85 • ) and by excluding event types with the largest point spread function (PSF0). 6 We used the P8R3 SOURCE V3 instrument response functions (IRFs).The selected spectral model included all the point-like and extended LAT sources located at a distance < 20 • from the investigated CSOs, as listed in the Fourth Fermi-LAT Source Catalog (4FGL-DR2; Abdollahi et al. 2020), as well as the Galactic diffuse and the isotropic emission models 7 adopted to compile the 4FGL-DR2.We first optimized the model for a given ROI, then we searched for additional new sources not included in 4FGL-DR2, and finally, if the source was significantly detected (> 3σ significance), we re-localized the source.
During the model fitting, we left the normalization of the isotropic and Galactic diffuse backgrounds as well as the spectral parameters of the sources within 5 • of our 5 version 1.0.1 http://fermipy.readthedocs.io/en/latest/ 6A measure of the quality of the direction reconstruction is used to assign events to four quartiles.γ-rays in Pass 8 data can be separated into 4 PSF event types: 0, 1, 2, 3, where PSF0 has the largest point spread function and PSF3 has the best. 7https://fermi.gsfc.nasa.gov/ssc/data/access/lat/BackgroundModels.html, in particular the diffuse model gll iem v07.fits and the isotropic component iso P8R3 SOURCE V3 v1.txt .targets free to vary, while for the sources at a distance between 5 • and 10 • , only the normalization was fitted; we fixed the parameters of all the sources within the ROIs at larger angular distances from our targets to their 4FGL values.Spectral fits were performed over the energy range from 100 MeV to 1 TeV.
None of the selected targets were significantly detected (> 3σ significance) in the high-energy γ-ray range with LAT.In particular, all three sources present a source significance compatible with 0 σ.In Table A1 of Appendix A we provide the resulting upper limits.

Archival Data
The radio, infrared, and optical/UV data for J1407+2827, J1511+0518, and J2022+6137 used for SED modeling were acquired from the NASA/IPAC Extragalactic Database (NED).The relevant references are listed in Table A3 of Appendix A. For the data within the near-IR-to-UV range, de-reddening was performed using the extinction law with the coefficients a(λ) and b(λ) as given in Cardelli et al. (1989), and the B-band and V-band Galactic extinction values A B and A V as given in the NED following Schlafly & Finkbeiner (2011).Source-intrinsic reddening was not taken into account.
In addition, we also collected de-absorbed fluxes corresponding exclusively to the power-law emission components, obtained via spectral modeling of the broad-band X-ray data collected previously with Chandra, XMM-Newton, and NuSTAR by S19 (for J1407+2827) and S23 (for J1511+0518 and J2022+6137) These power-law components represent the direct intrinsic X-ray continuum emission of our sources.

The 'Expanding Lobes' Model
We conducted a modeling analysis of the broad-band SEDs for the three selected CSOs, to probe the origin of their X-ray continuum power-law emission.Based on the modeling results, we also investigated the origin of the X-ray reflection components, as well as the apparent γ-ray quietness of the sources.For this purpose, we explored the model of expanding young radio lobes in AGN, put forward by LS08.In this section, we briefly summarize the model assumptions and model parameters (see Table 2).We refer the readers to LS08 for further details (see also Ostorero et al. 2010, further referenced as LO10).
The model evolves a self-consistent set of equations that describe both the expansion of light relativistic jets and their lobes in a dense ambient medium (see Begelman & Cioffi 1989), and the evolution of ultra-relativistic electrons injected into the lobes by the jets, taking into account adiabatic energy losses and radiative cooling.In this framework, a pair of relativistic jets with total kinetic energy L j , propagates through the inner segment of the host galaxy, characterized by a constant density ρ ≃ m p n 0 .The jets' thrust is balanced by the ram pressure of the ambient medium spread over some area larger than the jet terminal cross-section (due to the effects of a jet precession), so that the jet advance velocity, v h , is at most mildly-relativistic.Moreover, the model assumes that all the bulk kinetic energy transported by the jets, is converted at the jet termination shock into the internal energy of the jet particles and the jet magnetic field, amounting together to the lobes' internal pressure p.The resulting pressure-driven expansion of the lobes in the direction perpendicular to the jet axis, is supersonic, even though sub-relativistic.
Ultra-relativistic electrons and positrons (hereafter referred to as "electrons" for simplicity) injected into the lobes, are described by the initial energy distribution Q(γ, t), which in our case is assumed to be constant in time and a broken power-law function of electron energy E e ≡ γ m e c 2 , namely Q e (γ) ∝ γ −s1 for γ min < γ < γ br , and Q e (γ) ∝ γ −s2 for γ br < γ < γ max .This distribution is evolved in expanding lobes and integrated over the entire source lifetime, taking self-consistently into account adiabatic energy losses, synchrotron emission, and the IC scattering on different photon populations.Those seed photon populations include photons originating from the lobes' synchrotron emission, IR photons originating from the obscuring torus, and UV photons associated with the radiation of the accretion disk.Here we do not consider Comptonization of the starlight emission of host galaxies, noting that this process is of a minor relevance in the case of the youngest and most compact (LS < 100 pc) CSOs (see the related discussion in LS08 and LO10).Likewise, the synchrotron self-Compton process is in all the analyzed cases negligible as well.
We assume that the IR and UV spectra of the soft photons are monochromatic, with luminosities (L IR and L UV ) and frequencies (ν IR and ν UV ) corresponding to the bolometric luminosities and characteristic frequencies of the black bodies which match the observed data points in the respective bands.We note that such an approximation does not significantly affect the calculated high-energy IC emission of the lobes, given the broad energy range of the lobes' electron energy distribution, Q e (γ).The radio continuum is modeled as synchrotron emission of the lobes, assuming that the low-frequency break in the CSO radio spectrum, around the observed peak frequencies ν peak , is due to the free-free absorption on the interstellar medium (ISM) clouds engulfed by the expanding lobes, and photoionised by the nuclear emission (Begelman 1999).
The lobes' magnetic field and electron energy densities are parameterized as U B = η B p and U e = η e p, respectively, where p is the total lobes pressure, and the proportionality factors η B , η e < 1 are assumed to be constant during the source evolution (see the discussion in LS08).The linear size of the radio structure, measured from the radio core position to the jet termination shock ("hotspot"), is denoted below as LS.

The Modeling Procedure
Among sixteen modeling parameters introduced in the previous section and summarized in Table 2, three could be measured directly from high-resolution radio monitoring data available for all the analyzed sources.These included radio linear sizes, LS, peak frequencies, ν peak , and jet advance velocities, v h , all as given in Table 3 with the corresponding references.Two other modeling parameters, namely the IR torus luminosity L IR and its characteristic frequency ν IR , could be estimated based on the integrated IR data, also as summarized in Table 3.
We have constrained ranges of the ambient medium density based on the intrinsic equivalent hydrogen column density values, N H , provided for each source based on the detailed analysis of the X-ray spectrum (see Table 4).In particular, we estimated lower limits for the ambient medium density utilizing the fact that all three CSOs appeared point-like in the Chandra images, and assuming that the X-ray absorbing matter is distributed in a circumnuclear region with a characteristic spatial scale corresponding to ℓ = 1.5 ′′ at the redshift of a source, a typical radius of a Chandra source extraction region; this gave n low ≃ N H /ℓ. Upper limits for the ambient medium density, on the other hand, were found assuming that the characteristic spatial scales of the Xray absorbers were comparable to the sources' radio linear sizes, namely n high ≃ N H /LS. Because the range spanned by the n low and n high values is relatively wide, ∼ 2.5 dex, we have in addition considered intermediate (in orders of magnitude) densities, n int , all as given in Table 4. Since the observed IR-to-UV data points were not corrected for the source-intrinsic reddening, the UV emission of an accretion disk was treated as a model free parameter, except that we fixed its comoving characteristic frequency at ν UV = 2.45 × 10 15 Hz, following LO10.Generally, broad-band quasar observations suggest that L IR ≃ η t L UV , with η t ≳ 0.5 (see in this context, e.g., Ra lowski et al. 2024), albeit with a rather wide spread.Therefore, in this work we considered a range of L UV luminosites corresponding to η t = 0.1 − 1.From this range, we chose the values of L UV that resulted in a good match of the high-energy spectra with the given X-ray and γ-ray observational constraints.
Regarding the pressure content of the lobes, in our modeling we investigated two sets of the η B and η e parameters.The first set, η B = 0.3 and η e = 3.0, corresponds to the scenario in which ultrarelativistic electrons account for the bulk of the lobes' pressure, p e ≡ U e /3 ∼ p, where p stands for the total pressure, while the electron-to-magnetic field energy density ratio is of the order of ten, U e /U B ≃ 10 (a typical value emerging from modeling relativistic jets in blazar sources; e.g., Ghisellini et al. 2010).The second set, η B = 0.75 and η e = 0.75, corresponds to the energy equipartition between lobes' ultrarelativistic electrons and magnetic field, U e /U B ≃ 1, in which case p e ∼ p/4.
For a given combination of n 0 , L UV , η e , and η B , the model synchrotron (radio) and the IC (X-ray and γray) emission continua are set by the jet bulk kinetic power, L j , and the spectral shape of the injection function, Q e (γ).The L j parameter predominantly controls the normalization of the emission continua.However, it also affects the spectral shape.For example, for a given source size, LS, and advance velocity, v h , the larger the L j parameter the higher the energy density of the lobes' magnetic field, which leads to an enhanced synchrotron cooling and therefore to softer high-energy spectra of the evolved electron population.Thus, in our modeling procedure, for each considered combination of the n 0 , L UV , η e , and η B parameters, we adjust the corresponding L j and Q e (γ) values until we obtain a satisfactory match to the radio data points and, at the same time, the X-ray power-law continua, paying attention also to the upper limits in the high-energy γ-ray frequency range.
To reduce the number of the free model parameters, we fixed the minimum and maximum electron Lorentz factors as γ min = 3.0, and γ max = 100 m p /m e , respectively.This choice does not affect the model spectra as long as s 1 < 2.0 and s 2 ≫ 2.0, which in fact is the case for all the three targets (see Table 2 for parameters description).

RESULTS OF SED MODELING
We successfully employed the expanding radio lobe emission scenario to model the broad-band SED of three CSOs: J1407+2827, J1511+0518, and J2022+6137.For the relevant parameter space of the model we employ, the X-ray emission continuum is produced through the IC scattering of both the torus (IR) and disk (UV) photons, while the γ-ray emission is generated exclusively through the IC scattering of the UV emission.Since the torus luminosity is constrained by the observed fluxes at IR wavelengths, for a given set of model parameters, a particular L IR value sets a strict lower limit on the X-ray emission of the lobes.The disk luminosity, on the other hand, is a free parameter of the model.For large enough values of L UV , the IC scattering of this photon field may dominate over the IC scattering of the torus IR photons, increasing the overall level of the lobes' X-ray continuum.Yet, since high-energy γ-rays are produced via the IC scattering of the UV photons, the Fermi-LAT upper limits set in turn an upper limit on the allowed value of L UV .The high-energy emission output is additionally moderated by the ISM density and the U B /U e ratio.Therefore, the X-ray and γ-ray emission is controlled by the interplay between L U V , n 0 and U B /U e allowing different sets of their values reproduce observed X-ray radiation and follow the γ-ray flux upper limits.
The free model parameters related to the spectral shape of the electron injection function, Q e (γ), are tightly constrained by the observed shape of the radio continua, with the data in the sub-mm range being of a particular importance.Specifically, the shapes of the radio continua require a broken power-law electron injection function with s 1 < s 2 with s 1 in the ∼ 1.3 − 1.6 range.The steep high-frequency segments of the radio continua require that the high-energy slope of the electron energy distribution, s 2 , is in the range ∼ 4.7 − 5.8, that is significantly softer than s 2 = 2, which corresponds to a standard diffusive shock acceleration.We revisit this finding in the discussion Section 6 in the context of the γ-ray quietness of the analyzed targets.
When it comes to the low-frequency segments of the observed radio continua of the discussed CSOs, we note that the applied "engulfed clouds free-free absorption" scenario performs extremely well for J1407+2827 and J1511+0518, but fails in reproducing the radio spectrum of J2022+6137.In particular, in J2022+6137 we observe an excess low-frequency radio emission over the model spectra for all combinations of the model free parameters.

J1407+2827
In the case of J1407+2827, a wide range of the free model parameters under the equipartition condition U e /U B ≃ 1 could account for the broad-band SED of the source.For sub-equipartition models with U e /U B ≃ 10 (i.e., η e = 3.0 and η B = 0.3), the X-ray emission was generally exceeded for any model with the density values below n int .The corresponding model solutions are presented in Figure 2, and summarized in Table 5.
The broad-band SED of J1407+2827 was previously discussed in the framework of the expanding radio lobe scenario by LO10.However, they explored only the subequipartition models with U e /U B ≃ 10, and with a relatively low ambient medium density of n 0 ≃ 0.1 cm −3 .Moreover, the X-ray spectrum considered in LO10, based on the analysis of the initial XMM-Newton observations (Guainazzi et al. 2004), was subject to large uncertainties (∼two orders of magnitude at ∼ 0.3 keV, one order of magnitude at ∼ 10 keV), preventing robust constraints on the model parameters.In our analysis, we utilized the X-ray continuum and X-ray absorption constraints following from the modeling of an updated broad-band X-ray dataset (S19).As a result, we probed significantly higher ISM density values, 70 − 2 × 10 4 cm −3 .Finally, we added the new sub-mm and γ-ray constraints.The main difference between our modeling and the one presented in LO10 was in the jet kinetic luminosity L j , which we found to be lower by one to two orders of magnitude, while the parameters of the electron injection function and the soft photon fields were in rough agreement.In particular the value s 2 = 5.8 is in agreement with the value reported in LO10 (s 2 = 5.6).

J1511+0518
The SED and best model are shown in Fig. 3. Models that could match the observed SED in both the radio and the X-ray domains, were the equipartition models U e /U B ≃ 1 (i.e., η e = η B = 0.75), with relatively low  The SED and the best matching models for J1511+0518 with radio lobes in equipartition.Data and model components marked the same as in Figure 2.
UV luminosities, L UV ∼ (1.0 − 3.5) × L IR , and a relatively high ISM density, within the n int − n high range, as presented in Figure 3, and summarized in Table 5. Models with lower ISM densities, n 0 < n int , or departing from the equipartition condition, U e > U B , generally over-predicted the X-ray flux, unless the disk UV luminosity was set to be very low, L UV ≪ L IR , the possibility which we deem as unlikely.

J2022+6137
J2022+6137 is characterized by an enhanced level of the intrinsic X-ray continuum emission when compared to J1407+2827 and J1511+0518.The 0.3-40 keV luminosity of the source, ∼ 10 44 erg s −1 , could not be obtained within the framework of the applied scenario for high values of the ambient density, regardless of the equipartition ratio U e /U B , without invoking an additional, phenomenological X-ray component.On the other hand, the ISM density at the level approaching n low and an equipartition parameter 1 ≲ U e /U B ≲ 10, allowed us to match the intrinsic X-ray power-law continuum with the lobes' IC emission without violating the Fermi-LAT upper limits.Interestingly, for J2022+6137, the γ-ray upper limits were more restrictive than the X-ray constraints.An increase in L U V or a decrease in n 0 violated the γ-ray limits before the X-ray limits.The results of the modeling for this source are presented in Figure 4, and summarized in Table 5.

DISCUSSION AND CONCLUSIONS
In this work, we studied the broad-band emission of three highly X-ray obscured active galaxies, with a CSO radio classification, J1407+2827, J1511+0518, and J2022+6137, each featuring young, compact radio lobes with linear sizes up to 25 pc.We demonstrated that the IC scattering of the IR and UV photons (supplied by a dusty torus and an accretion disk, respectively) within the expanding radio lobes, provides a plausible source of intrinsic X-ray continuum emission on the levels consistent with the observational constraints.
For the two analyzed CSOs, J1407+2827 and J1511+0518, certain models could be ruled out because they overestimated the intrinsic X-ray emission, while none of the probed models were found to underestimate the intrinsic X-ray emission or to violate the γ-ray upper limits.Models accounting for the comparatively high 0.3 − 40 keV luminosity of J2022+6137 (∼ 10 44 erg s −1 ), and at the same time complying with its γ-ray con- straints, were characterized by a low ambient medium density and high ultraviolet luminosity, L UV = 10L IR , in the case of lobes in the equipartition.A range of n 0 and L U V values, consistent with the lower end of the range depicted in Figure 4, was allowed for the case of the lobes in sub-equipartition.Since the high density models underestimated the X-ray emission of J2022+6137, we note that an additional, phenomenological X-ray continuum component may be present in the SED of J2022+6137.In Figure 5 we show an example of a model consisting of the emission of the expanding radio lobes with n 0 = 4 × 10 3 cm −3 , and a phenomenological cut-off power-law component with a photon index of 1.45 (the best-fit photon index of the intrinsic de-absorbed X-ray power-law in S19).The photon index of 1.45 is within the range observed in AGNs and X-ray binaries (Yang et al. 2015).This additional component, with the 2−10 keV luminosity of ∼ 10 44 erg s −1 , could originate, e.g., due to a compact lamp-post corona very close to the black hole or due to a complex structure of the jetted outflow (see Migliori et al. 2014 andSobolewska et al. 2022 in the context of young radio sources).Apart from its high X-ray luminosity, J2022+6137 stands out in our sample also because of an excess lowfrequency radio emission compared to the model spectrum, for any combination of the free model parameters.This could signal a presence of an additional, extended (on arcsec scales) radio component (see in this context Kharb et al. 2010).It is also possible that the engulfed clouds free-free absorption scenario is not applicable in the case of J2022+6137.
For all three sources, we compared the resulting L UV and L j values, to those estimated in AW20: 31 × 10 42 erg s −1 (J1407+2827), L j = 10.5 × 10 42 erg s −1 (J1511+0518), 220 × 10 42 erg s −1 (J2022+6137); and L UV = 4.3×10 45 erg s −1 (J1407+2827) 1.5×10 45 erg s −1 (J1511+0518), 1.5 × 10 45 erg s −1 (J2022+6137).Due to the high absorption of these CSOs, AW20 estimated L U V through the SED for J1511+0518, (following the Trichas et al. 2013, method), based on the 12 µm and OIII lines respectively for J1407+2827 and J2022+6137 (Kosmaczewski et al. 2020;Wu 2009).The inferred L U V values from our analysis are in agreement with those presented by AW20.The jet power resulting from our modeling is also roughly in agreement with the values estimated by AW20.The differences, which are up to a factor of a few, could result from the different assumptions about lobe geometry and the strict energy equipartition assumed in AW20.Note in this context that the emerging total jet power for J1407+2827 and J1511+0518 are ≤ 10 44 erg s −1 , below the threshold for an effective confinement of the lobes within the ISM.Therefore they are expected to be trapped for a relatively long time before they expand outside of the host galaxies (Mukherjee et al. 2016(Mukherjee et al. , 2017)), whereas the total jet power of J2022+6137 for some models is above this threshold.
Modeling the radio continua, including newly acquired SMA data, indicated that the electron energy spectrum has to be of a broken power-law form, with s 1 ≤ 2 below γ ∼ m p /m e , and s 2 ≫ 2 at higher energies.Fermi-LAT observations reinforced this conclusion because with no sharp break in the electron energy distribution, s 2 −s 1 > 2, the current LAT upper limits for the source fluxes would be exceeded.Moreover, we emphasize that this broken power-law form of the energy distribution corresponds to the electron 'injection' spectrum.Thus, it described the electron spectrum formed at the acceleration site, namely, the jet termination shock, and not the spectrum modified by the subsequent evolution within the expanding and radiatively cooling lobes.This finding aligns with the scenario proposed by Stawarz et al. (2007), where a broken power-law electron energy distribution with a critical break energy around m p /m e represents two distinct regimes of electron acceleration at mildly-relativistic, proton-dominated shocks with perpendicular magnetic field configurations.The main hypothesis is that in a proton-mediated shock, only electrons with energies exceeding those of cold protons (γ > m p /m e ) can undergo diffusive shock acceleration.This process is expected to yield steep electron spectra (energy indices ≫ 2) at mildly-relativistic perpendicular shocks.Electrons with lower energies (γ < m p /m e ) are likely accelerated by different mechanisms, possibly in the near upstream of the shock (as discussed and referenced in Stawarz et al. 2007).
In Figure 6, we compare the s 2 parameter values emerging from our modeling of the three heavily Xray obscured CSOs, with those obtained for X-ray unobscured CSOs by LOS10 (excluding J1407+2827) and Sobolewska et al. (2022, PKS 1718-649), using the same expanding radio lobe model.We plot s 2 as a function of the projected linear radio size, LS, and as a function of the source-intrinsic absorbing column density, N H .It can be seen that the s 2 index correlates with N H , and that the most compact CSOs, with LS ≲ 25 pc, have softer s 2 indices than CSOs with LS ≳ 100 pc.
In our modeling the absorbing column density guides the values of the ambient medium density into which the newly born CSO jets propagate, N H ∝ n 0 , the s 2 − N H correlation observed in our small sample agrees very well with the s 2 −n 0 trend reported in the model data for the evolved radio galaxies by Wójtowicz et al. (2021).This allows us to draw the same conclusion as Wójtowicz et al., namely that the efficiency of the electron acceleration at mildly-relativistic termination shocks of AGNs jets decreases with increasing density of the ambient medium.Moreover, very soft values of s 2 may explain the apparent quietness of compact and heavily obscured CSOs in the γ-ray range, since it is the high-energy slope of the electron energy distribution that effectively suppresses the lobes' IC emission at GeV photon energies for a given total jet kinetic power and a given disk UV luminosity (compare to the case of the γ-ray detected PKS 1718-649 discussed in Sobolewska et al. 2022).
The ISM number densities resulting from our modeling are relatively high, orders of magnitude higher than the fiducial value of n 0 = 0.1 cm −3 considered in the analogous modeling of CSOs by LO10.However, all the sources analyzed in LO10, except J1407+2827, have linear radio sizes exceeding 100 pc, and one should expect lower ambient medium densities for them when compared to the three particularly compact/young targets discussed here.Indeed, assuming a general scaling of n 0 with the square of the distance from the black hole, as appropriate for the winds from black hole accretion flows (see, e.g., Cui et al. 2020), gas number densities at the level of ∼ 10 3 cm −3 at 10 pc scale, would correspond to ∼ 0.1 cm −3 at the distance of 1 kpc.
We can also compare our estimates of the ISM density with the estimates obtained for galaxies with a radioloud tidal disruption event (TDE).Cendes et al. (2023) presented a collection of ISM density profiles in TDE hosts, constructed assuming an external shock model (see however in this context Pasham & van Velzen 2018).For the distance scale corresponding to 1 − 25 pc (linear radio size of the lobes in our sources), expressed in Schwarzschild radii (10 5 − 10 6 Schwarzschild radii for X-ray reflection continua, including the fluorescent narrow Iron Kα line at 6.4 keV, have been detected in all three CSOs (S19, S23).This raises a question regarding the origin of the X-ray reflection component in these objects.Interestingly, these galaxies fall within the Quasar/Seyfert region on the WISE color diagram and their mid-IR colors align with the dominant emission from circumnuclear dust (Kosmaczewski et al. 2020;Nascimento et al. 2022).Additionally, the linear sizes of their radio lobes are of the same order as those of dusty tori in numerous Seyfert Galaxies, as measured by ALMA (e.g., Combes et al. 2019;García-Burillo et al. 2021).Therefore, we propose that in all three cases, the reflection components may in fact be related to the isotropic IC emission from the lobes reflecting off the tori.
In Appendix B we provide the energetic considerations, concluding that the lobes' high-energy (X-ray and γ-ray) emission, may indeed dominate over the disk corona radiative output in the case of the youngest and the most powerful CSOs.We emphasize in this context that, in both cases, we are dealing with the accretion power (or, to be more precise, a combination of the accretion power and the black hole rotational energy), but, nonetheless, the mechanism for extracting a fraction of this power to produce the high-energy emission is quite distinct.In particular, the energy radiated away in the high-energy domain is either at the expense of a disk magnetic energy dissipated within disk corona to hot electrons (see, e.g., Sridhar et al. 2021), or a bulk kinetic energy of relativistic jets converted at the jet termination shock to the internal energy of the lobes' ultra-relativistic electrons.
In Figure 7, we present a sketch illustrating the proposed scenario.In the left panel of the figure, we present a schematic "standard" view of an evolved radio-loud AGN, depicting in particular how the UV disk emission is IC scattered within an ultra-compact region filled with hot electrons (e.g. a lamp-post corona above the accretion disk, a hot inner flow, or a base of a jet), giving rise to the X-ray continuum emission, which is subsequently reflected from a dusty torus to form the X-ray reflection component.The right panel of the figure illustrates a young radio source, where the X-ray continuum emission originates within the compact radio lobes, inflated by the newly-born relativistic jets propagating through the circumnuclear environment.Such a scenario predicts that the X-ray emission of CSOs whose radio lobes expanded beyond the scale corresponding to the size of a dusty torus should not show strong absorption and reflection features.So far, the existing X-ray observations of the CSO sources support this idea in that they have not identified X-ray absorbed CSOs or CSOs showing a 6.4 keV Iron fluorescence among the sources with radio sizes ≳ 40 − 50 pc (e.g., Sobolewska et al. 2019a).
Interestingly, due to the rather different geometries of the systems shown in the left and right panels of Figure 7, as well as different spatial scales and energies of the radiating electrons involved, variability patterns and polarization properties of the X-ray continuum emission produced in the framework of the "standard" model and our CSO scenario should be quite distinct.In particular, in the CSO scenario we expect a rather steady Xray continuum (power-law) emission, involving possibly only a gradual monotonic decrease on the timescale of years, as opposed to a stochastic red-noise variability expected in the case of an ultra-compact X-ray source (Uttley et al. 2014).An in-depth spectral modeling of the reflection component in the framework of our model, along with an analysis of the X-ray polarization properties, keeping in mind the capabilities of current and future X-ray polarimetry missions, will be presented in a forthcoming paper.

SUMMARY
We studied the broadband spectral energy distribution of three galaxies with CSO radio classification: J1407+2827, J1511+0518, and J2022+6137.The radio morphologies of these galaxies are characterized by small projected linear sizes (up to 25 pc).Additionally, in X-rays they are heavily absorbed, N H > 10 23 cm −2 , and display fluorescent Fe Kα lines in their spectra.The main findings from our modeling of their radio to γ-ray emission are summarized as follows: 1) The high-energy emission of these three sources can be explained within the framework of an expanding radio lobe model.Namely, the X-ray continuum originates from radio lobes that are still embedded within the dusty tori.These lobes constitute a reservoir of relativistic electrons producing high-energy emission through Comptonization.This emission is then reflected from the torus, adding fluorescent Fe Kα lines and the reflection component.
2) The proposed scenario may result in different polarization properties than the polarization from a "standard" compact corona.These properties will be considered in future work.
3) Given the energetics of the system, detailed in Appendix B, the high-energy emission of the most compact radio lobes might dominate over the diskcorona radiative output.
4) The high-energy slope of the broken power-law electrons' energy distribution at injection has to be notably soft (s 2 ≃ 4.7 − 5.8) to account for the spectral shape of the radio emission in all three sources.Relative to other CSOs, this index appears to correlate with the X-ray absorbing column density (the higher N H , the higher s 2 ) and to anti-correlate with source size (the larger the object, the smaller s 2 ).The softness of the highenergy index of the electron energy spectrum at the injection suggests that the efficiency of particle acceleration decreases with the density of an ambient medium.This anti-correlation between acceleration efficiency and n 0 might be responsible for the γ-ray quietness of these sources Additionally, it might be responsible for the γ-ray quietness of these sources.In general, the obtained ISM density values are rather high, ranging from ∼ 10 to even 10 4 cm −3 .Interestingly, the ISM densities obtained through our modeling agree with estimates obtained from the multi-epoch radio followups of tidal disruption events in several galaxies, at distances corresponding to the radio lobes size in our sources.
5) The broadband spectral properties of J2022+6137 differ from those of J1407+2827 and J1511+0518 in several aspects.The ratio of the intrinsic (deabsorbed) X-ray power-law flux to the upper limits on the γ-ray flux is significantly higher in J2022+6137 than in the case of the other two CSOs.Consequently, for some models, the data of J2021+624 require an additional X-ray emission component (as in the case of PKS 1718-649; Sobolewska et al. 2022).This additional component can be associated with e.g., a compact corona, a base of a jet, or a hot inner flow.The emerging total jet power of J1407+2827 and J1511+0518 is ≲ 10 44 erg s −1 .However, in J2022+6137 the jet power of the lowest density models reaches and even exceeds this threshold, which suggests that jet expansion beyond the host galaxy is more likely in the case of J2022+6137 than in the case of other two considered sources (Mukherjee et al. 2016(Mukherjee et al. , 2017)).Finally, our model under-predicts the radio emission of J2022+6137 below the spectral break, signaling either the presence of an additional, extended radio component or indicating that it cannot be described within the framework of enfluged clouds free-free absorption.The SMA is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica.We recognize that Maunakea is a culturally important site for the indigenous Hawaiian people; we are privileged to study the cosmos from its summit.Software: CIAO v.4.14 (Fruscione et al. 2006), Sherpa (Freeman et al. 2001) Table A3.References to the archival radio, infrared, and optical/UV data.

B. BASIC ENERGETIC CONSIDERATIONS
The accretion disk UV luminosity can be written as where η d is the disk radiative efficiency, and Ṁacc is the mass accretion rate.For standard geometricallythin/optically-thick disks, one expects η d ∼ 0.1 (depending however on the black hole spin; see, e.g., Abramowicz & Fragile 2013, and references therein).Some fraction of this emission may be reprocessed within the disk corona, and re-emitted in the X-ray range, so that the resulting corona luminosity is L X ≃ η c L UV .The efficiency factor here, η c , may obviously change from source to source, and may in particular scale with the disk luminosity.A relatively tight Xray/UV luminosity correlation established for quasars (e.g., Lusso & Risaliti 2016), indicates nevertheless average values of η c ∼ 0.1 for lower-luminosity sources (L UV ≲ 10 45 erg s −1 ), decreasing down to ∼ 0.01 for high-luminosity ones (L UV ≳ 10 47 erg s −1 ).The mid-IR luminosity of a dusty torus is also expected to constitute some fraction of a time-averaged disk emission, L IR ≃ η t L UV , where η t ≳ 0.5 as implied by the analysis of the broad-band SEDs of quasars (see, e.g., Ra lowski et al. 2024).
The energy density of the nuclear emission components, including both the torus IR and the disk UV emission, at the distances larger than the dust sublimation radius, i.e., effectively on the scales of the order of the CSO linear size LS > 1 pc (defined in this paper as half of the hotspot-hotspot distance), is The total IC luminosity of the lobes is therefore where V is the total volume of the lobes, For various electron injection spectra and other CSO parameters explored in LS08, f γ turned out typically of the order of the electron cooling energy, γ cr ∼ 10 2 − 10 3 .In spite of the electron energy distribution N e (γ) evolving with time in the expanding lobes due to the adiabatic and radiative cooling, LS08 argued that at every moment of the CSO lifetime, U e constitutes approximately the same fixed fraction of the lobes' total pressure p, namely U e ≃ η e p.In the case radiating electrons dominate the lobes' pressure, one has for example η e ≃ 3.And since the total energy of the plasma filling the lobes is deposited by a pair of jets over the source lifetime, one may further write 3pV = 2L j τ j , (B6) where L j is the jet kinetic power, and τ j = LS/v h is the source lifetime for the observed (and constant, by assumption) hotspots advance velocity, v h (defined here as half of the hotspot-hotspot separation velocity).Note that the jet total power and the mass accretion rate can be related by introducing the jet production efficiency parameter η j , namely In principle, in the most favourable conditions provided by the magnetically arrested disks around maximally spinning black holes, η j may even exceed unity, as the jet power is in this case extracted at the expense of the accretion power and the black hole rotational energy (Tchekhovskoy et al. 2011).However, for the sample of known CSOs with measured parameters of the central engine, Wójtowicz et al. (2020) observed in general values of the jet production efficiency parameter much lower than unity, with a significant spread around from η j ≳ 0.01 to η j < 0.1.Taking into account the above considerations, the ratio of the lobes' total IC luminosity and the disk corona luminosity, reads as (1 + η t ) η e η j η c η d where we introduced the Eddington ratio for the Eddington luminosity L Edd = 4πGM BH m p c/σ T corresponding to the black hole mass M BH .The luminosity ratio given in Equation B8 may be larger or smaller than unity, depending on a particular combination of the source parameters.In general, however, one may expect that the lobes' IC emission dominates over the disk corona radiative output in the case of the youngest and the most powerful CSOs, i.e. sources characterized by high accretion rates λ Edd > 0.01 and compact lobes with linear sizes LS ≲ 10 pc, preferentially located in a dense environment so that the jets' advance velocities are low, v h < 0.1c.

Figure 1 .
Figure 1.Left: Chandra The merged Chandra ACIS-S image of three J1511+0518 observations.The source and background extraction regions are denoted by a circle with the radius of r ≃ 2.5 ′′ (white), and an annulus with r ≃ (5 − 10) ′′ (green), respectively.Right: Brightness profile of the merged image (blue data points and lines), along with the simulated averaged PSF (orange curve).The orange shaded region around the average PSF indicate the range (i.e., the minimum and maximum values) observed at a given radius in 150 random PSF realizations.

Figure 2 .
Figure 2. The SED and the best matching models for J1407+2827, corresponding to the model free parameter values/ranges as summarized in Table 5 and the figure legend.The archival radio and radio-to-UV data are denoted in the figure by black circles.The new SMA data are plotted as open green squares.The orange bow-tie represents the intrinsic de-absorbed X-ray power-law constraints.Finally, the green arrows illustrate the Fermi-LAT upper limits.The model components include: the lobes' synchrotron emission (gray shaded area), the torus IR emissions (red curve), the disk UV emission (dark-blue shaded area), the IC emission off the disk UV photons (light-blue shaded area), and the IC emission off the torus IR photons (light-red shaded area).Upper panel: radio lobes in equipartition, lower panel: Ue = 10UB.
Figure 3.The SED and the best matching models for J1511+0518 with radio lobes in equipartition.Data and model components marked the same as in Figure2.

Figure 4 .
Figure 4.The SED and the best matching models for J2022+6137.Upper panel: radio lobes in equipartition, lower panel: Ue = 10UB.Data and model components marked the same as in Figure 3.

Figure 5 .
Figure 5.An example of the expanding radio lobe model solution applied to the SED of J2022+6137, which underestimates the most the intrinsic X-ray emission (see the plot label and Table 5 for model parameters).Data, intrinsic X-ray emission and Fermi-LAT upper limits are plotted the same as in Figure 4.An additional , phenomenological X-ray component with the photon index of 1.45 and the 2 − 10 keV luminosity ∼ 9.95 × 10 43 erg s −1 is required (orange line) to match the intrinsic X-ray emission, and it dominates the X-ray band.The model components include: the lobes' synchrotron emission (gray solid line), torus IR emissions (red short-dashed line), disk UV emission (blue long-dashed line), IC emission of the disk seed photons (blue solid line), IC emission of the torus seed photons (red solid line).The thick solid black line corresponds to the sum of the IC components from the lobes and the additional X-ray component.

Figure 6 .
Figure 6.Comparison of the high-energy slope of the injection electron distribution, s2, with the radio linear size LS (left panel), and the source-intrinsic absorbing column density NH, for the three obscured CSOs analyzed in this paper, J1407+2827, J1511+0518 and J2022+6137, the X-ray unobscured PKS 1718-649 modeled in Sobolewska et al. (2022), and other CSOs with low NH modeled by LO10 and depicted in the figure by the gray shaded areas.

Figure 7 .
Figure 7. Left panel: Schematic view of an evolved radio-loud AGN, depicting the UV disk emission comptonized within ultracompact disk hard X-ray emitting region, and subsequently reflected by a dusty torus to form the reflection X-ray component.Right panel: Schematic view of a young radio source, where the X-ray continuum emission is produced within compact radio lobes, formed by newly-born relativistic jets propagating through the circumnuclear environment.black hole masses ∼ 10 8 − 10 9 M ⊙ ; Wójtowicz et al. 2020), the ISM density estimates of Cendes et al. cover a density range, ∼ 10 − 10 3 cm −3 , similar to that resulting from our work.X-ray reflection continua, including the fluorescent narrow Iron Kα line at 6.4 keV, have been detected in all three CSOs (S19, S23).This raises a question regarding the origin of the X-ray reflection component in these objects.Interestingly, these galaxies fall within the Quasar/Seyfert region on the WISE color diagram and their mid-IR colors align with the dominant emission from circumnuclear dust(Kosmaczewski et al. 2020;Nascimento et al. 2022).Additionally, the linear sizes of their radio lobes are of the same order as those of dusty tori in numerous Seyfert Galaxies, as measured by ALMA (e.g.,Combes et al. 2019;García-Burillo et al. 2021).Therefore, we propose that in all three cases, the reflection components may in fact be related to the isotropic IC emission from the lobes reflecting off the tori.In Appendix B we provide the energetic considerations, concluding that the lobes' high-energy (X-ray and γ-ray) emission, may indeed dominate over the disk corona radiative output in the case of the youngest and the most powerful CSOs.We emphasize in this context that, in both cases, we are dealing with the accretion power (or, to be more precise, a combination of the accretion power and the black hole rotational energy), but, nonetheless, the mechanism for extracting a fraction of this power to produce the high-energy emission is quite distinct.In particular, the energy radiated away in the high-energy domain is either at the expense of a disk magnetic energy dissipated within disk corona to hot electrons (see, e.g.,Sridhar et al. 2021), or a bulk This paper employs a list of Chandra datasets, obtained by the Chandra X-ray Observatory, contained in DOI: https://doi.org/10.25574/cdc.213.
Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis.These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden.Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d'Etudes Spatiales in France.This work is performed in part under DOE Contract DE-AC02-76SF00515.

Table 1 .
Chandra observations of J1511+0518.Note-a ACIS-S3 exposure in seconds.b Net counts within the 5 px ≃ 2.5 ′′ circular source extraction region centered at the source coordinates.

Table 2 .
Parameters of the expanding radio lobe model.
br Break Lorentz factor of the electron energy distribution Qe(γ) Table 5 γmax Maximum Lorentz factor of the electron energy distribution Qe(γ) 100 mp/me (fixed) Note-The top part of the table contains parameters measured directly or estimated from the radio and IR data.

Table 3 .
Parameter values assumed in our modeling, based on the radio and IR data.For references to the IR data see TableA3.†Mean of ν peak for both lobes.
b See An & Baan (2012) and references therein.c

Table 4 .
Adopted range of the ambient medium density, n0.
D. L. K. and M. S. acknowledge NASA Chandra contract GO2-23110X.M. S. and A. S. was supported by NASA contract NAS8-03060 (Chandra X-ray Center).D. L. K. and L. S. were supported by the Polish National Science Center grants 2016/22/E/ST9/00061 and DEC-2019/35/O/ST9/04054. G. P. acknowledges support by ICSC -Centro Nazionale di Ricerca in High Performance Computing, Big Data and Quantum Computing, funded by European Union -NextGenerationEU.