\section{Sagittarius \texorpdfstring{A$^*$}{A*} (\textit{IXPE})}
\hspace{\parindent}The very first hard X-ray (8.5 -- 22~keV) images of the extended emission situated around the Galactic Center's supermassive black hole Sgr~A$^*$ were taken using the International Astrophysical Observatory \textit{GRANAT}. They revealed elongated emission parallel to the Galactic plane\cite{Sunyaev1993}, whereas soft X-ray emission is known to be more circularly-shaped\cite{Watson1981}. Theoretically, this asymmetry could be due to Thomson scattering of high energy photons by dense molecular gas clouds, such as the Giant Molecular Clouds (GMCs). And, indeed, X-ray observations of the GMCs have revealed fluorescent X-ray emission from cold iron atoms, a steep spectrum and a reflection continuum\cite{Koyama1996,Murakami2000,Churazov2002}, indicating that the GMCs act like reflecting mirrors. Basic scattering physics tells us that the reflected (polarized) X-ray radiation should lead to a map of the three-dimensional position of the clouds with respect to the illuminating source, together with revealing the position and luminosity history of the original source\cite{Vainshtein1980}. However, there is currently no persistent source bright enough ($\text{L}_{X} \ge 10^{39} \; \text{erg} \cdot \text{s}^{-1}$) to be the progenitor of the reflected radiation. From spectroscopic, imaging and timing arguments, numerous authors have speculated that Sgr~A$^*$ could have been much brighter in the past despite being presently dim\cite{Sunyaev1993,Churazov2002,Koyama1996,Murakami2000}. What we observe are just echoes of long-gone bright phases. If true, it means that the Galactic Center was similar to a low-luminosity Active Galactic Nucleus\cite{Ptak2001,Halderson2001} (LLAGN) in the past, with an X-ray luminosity $\sim 10^{40} \; \text{erg} \cdot \text{s}^{-1}$. Determining the activity period(s) of the bright X-ray emission is crucial to understand the duty cycle of black hole mass accretion\cite{Narayan1994,Elitzur2006}, the formation of AGN winds and torus\cite{Konigl1994,Elitzur2006}, and the spin evolution of primordial black holes \cite{Berti2008}.


\subsection*{Observation and data reduction problems}
\hspace{\parindent}The Sgr~A region nearby the central SMBH in the Galactic Center was observed with \textit{IXPE} twice in 2022: both in February and March. The total integration time amounts for about $1$Ms on the clock. As this source is expected to be faint and extended, it required the best possible seeing conditions and longest integration time. However the observation period matched with an increased solar activity period, which led to increased atmospheric noise and spurious events of geomagnetic storm. To analyse the data, an additional filtering is then required to remove noise and background events from the actual target observation.\par
The \textit{IXPE} spacecraft is on a low orbit ($\sim 600$km) at $\sim 0^\circ$ inclination to minimize the time spent above the South Atlantic Anomaly (SAA). This region produces atmospheric noise at high energy and seems to be dependent on solar activity. When passing above this region, the detectors onboard \textit{IXPE} are then turned off and the observation is resumed upon exit. As can be seen in Fig. \ref{fig:SgrAnoisy}, the light curve of the observation is heavily dominated by noise. Assuming an enlargement of the SAA due to increased solar activity, it is possible that the detector off-time does not match the time spent in the SAA and could then explain the increased background flux right before and after SAA pass-related off-times (see appendix \ref{Afig:Filtcorr}). Using \textsc{ixpeobssim} to predict the intervals corresponding to a target occulted by the Earth and the satellite trajectory above the noisy SAA, I successfully determined revised Good Time Intervals (GTIs\footnote{The GTI file contains the start and stop times of all accepted time intervals over the observation. The "good times" are periods when observing conditions were good: acceptable aspect solution and low background.}). This allowed me to perform some first-order filtering. I also had to fit the offset between the simulated observation time and the actual observation time to account for the true orbital parameters of the spacecraft (see appendix \ref{Afig:SgrAfilt}) and filter out a few geomagnetic storm events that occurred during the acquisition. The result is given in Fig. \ref{fig:SgrAnoisy}, where we can see that our assumption that the SAA has been enlarged can account for the detected noise and that our filtering effectively re-define the GTIs. After this filtering, we are left with a corrected Total GTI of $930,566$sec, which represents $96.7$\% of the original Total GTI. This filtering has been compared to other methods tried by different collaborators and yielded similar results (see appendix \ref{Afig:SgrAmultiplefilt}). My properly reduced list of events was then used for the analysis of the observation.

\begin{figure}[!ht]
    \centering
    \includegraphics[width=\textwidth]{./parts/appendix/SgrA_LC_SAA_large.png}
    \caption{Color-coded lightcurve of the observation of SgrA$^*$ by \textit{IXPE} with in \textbf{\textcolor{blue}{blue}} the corrected GTIs, in \textbf{\textcolor{green}{green}} the time in the Earth's shadow (target occulted), in \textbf{\textcolor{red}{red}} the time in the enlarged SAA and in \textbf{\textcolor{black}{black}} the events corresponding to a geomagnetic storm.}
    \label{fig:SgrAnoisy}
\end{figure}

\subsection*{Analysis of the data}
\hspace{\parindent}The previously filtered observation allowed us to analyse the underlying real flux from the Galactic Center. The target of this observation was a series of GMCs named the "Sagittarius A complex". Any detected polarization in the X-ray band would hint to the scattering of a past, long-lived X-ray outburst from the close-by SMBH Sgr~A$^*$. For this scenario to be valid, the angle of polarization must be normal to the line connecting the emission source and the scattering cloud. Then the polarization degree will inform us on the scattering angle (according to the Malus law), giving us the missing $z$-axis information of the cloud(s), allowing us to access the true distance of the scattering medium from the emission source.\par
The analysis of the \textit{IXPE} data yielded both polarization angle and degree coherent with the scattering of a past outburst of the central SMBH (see Fig. \ref{fig:SgrAanalysis}). The polarization degree exceeds $1$\% and the polarization angle is $\approx 133^\circ$, which is perpendicular to the position angle of the SMBH ($\sim 45^\circ$). The detected reflection is the record of a past active phase of the now quiescent Sgr~A$^*$. The data still need refinement to better locate the position of each GMC in the Sgr~A region, but the projected distance tells us that Sgr~A$^*$ was active in the past, around 400 years ago. The estimated X-ray luminosity necessary to produce such detectable feature in the X-ray corresponds to the activity of a low-luminosity AGN. This promising result allow us to do achieve, for the first time, Galactic archaeology and we are on the verge of characterizing its accretion-evolution history.

\begin{figure}[!ht]
    \centering
    \begin{subfigure}{0.5\textwidth}
        \centering
        \includegraphics[width=0.9\textwidth]{./parts/appendix/SgrA_avg_pol.png}
        \captionsetup{width=0.9\textwidth}
        \caption{\footnotesize Polarization components as a function of the confidence level for the emission from the targeted molecular cloud averaged on the 3 detector units of \textit{IXPE}.}
        \label{fig:SgrApol}
    \end{subfigure}%
    \begin{subfigure}{0.5\textwidth}
        \centering
        \includegraphics[width=0.9\textwidth]{./parts/appendix/SgrA_img_pol.png}
        \captionsetup{width=0.9\textwidth}
        \caption{\footnotesize Imaging of the Sagittarius A complex by \textit{IXPE} showing the detected polarization angle coherent with a reflected event.}
        \label{fig:SgrAimg}
    \end{subfigure}
    \caption{First analysis of the observation of the Sagittarius A complex with (a) the determination of the polarization components and (b) the corresponding imaging. The detected polarization is coherent with the reflection of a past X-ray outburst from SgrA$^*$ reflected on a molecular cloud.}
    \label{fig:SgrAanalysis}
\end{figure}

\section{Centaurus A (\textit{IXPE})}
\hspace{\parindent}Centaurus~A (Cen~A) is a nearby ($z = 0.00183$, $d \approx 3.84$~Mpc) radio-loud AGN that has been known for more than 175 years \cite{Herschel1847}. Its optical spectrum classifies it as a type-2 AGN, i.e. seen from the edge, where the nuclear light of the central SMBH and its accretion disk is obscured by a thick reservoir of dust and gas known as the ``torus'' \cite{Antonucci1993}. Due to its proximity, Cen~A has been observed at high spatial resolution despite its relatively low bolometric luminosity (a few $10^{43} \; \text{erg} \cdot \text{s}^{-1}$, \cite{Beckmann2011}) with respect to standard type-2 AGNs (a few $10^{44} \; \text{erg} \cdot \text{s}^{-1}$, \cite{Lusso2012}). In particular, the complex morphology of the jets and lobes detected from each side of the core has been explored in details. Only apparent in the radio and X-ray bands, those jets become sub-relativistic at a few parsec from the nucleus before expending into plumes at a projected distance of $5$kpc, ending their propagation in space in the form of huge radio lobes extending out to $250$kpc \cite{Israel1998}.\par
The core of Cen~A, however, is not only obscured by the spatially unresolved parsec-scale torus but also by a gigantic warped dust lane which effectively bisects the main body of the host galaxy, partially shrouding the nucleus and all optical structure in the inner $500$pc \cite{Schreier1996}. This dust lane is thought to be the remnant signature of a $10^7$ -- $10^8$ years old merger of Cen~A's host galaxy with a smaller spiral galaxy \cite{Baade1954,Malin1983,Israel1998} that could be responsible for the activity of the nucleus. The host galaxy of Cen~A is actually a giant, moderately triaxial, elliptical galaxy that contains large amounts of dust, atomic and molecular gas as well as luminous young stars \cite{Israel1998}. The excess of obscuring material is unfortunate as the nucleus is likely the place where the high energy photons detected by Cherenkov telescopes \cite{Grindlay1975}, EGRET \cite{Hartman1999}, HESS \cite{Aharonian2009} and Fermi \cite{Abdo2010a} are produced. Determining the mechanisms responsible for the acceleration of photons and particles to ultra high energies is fundamental for understanding the physics of cosmic $\gamma$-ray emitters and in particular the role of radio-galaxies as highly efficient relativistic electron accelerators. Because of their large number, these would collectively contribute, in a very significant way, to the redistribution of energy in the intergalactic medium \cite{Velzen2012}.

\subsection*{Observation preparation}
\hspace{\parindent} I seized the opportunity of \textit{IXPE}'s observation of Cen~A ($100$ks in February 2022) to investigate the true core polarization of this dust-enshrouded AGN. To do so, I not only used \textit{IXPE} results but also correlated the X-ray polarimetric data to other polarized information acquired in various wavelength bands. I searched the SAO/NASA Astrophysics Data System Abstract Service for all papers mentioning a past polarimetric measurement of the core of Cen~A. I discarded all radio polarization campaigns measuring the total (core plus jets plus lobes) polarization of Cen~A, since the lobes are known to strongly dominate the polarization from the core at most radio frequencies \cite{Burns1983,Goddi2021}. In total, there are only 13 papers reporting a polarization measurement from Cen~A's core, most of them in the near-infrared band. The data points cover almost the full electromagnetic spectrum, from the radio to the $\gamma$-ray band, the high energy emission coming from the base of the jets, see Fig.~\ref{fig:CenAmultiSED}.\par

\begin{figure}[!ht]
    \centering
    \includegraphics[width=\textwidth]{./parts/appendix/CenA_multi_SEDpol.png}
    \caption{Spectral Energy Distribution of the core of Cen A, color-coded in aperture size, where the solid dots are the total flux and the hollow dots are the polarized flux, all taken from the literature, except for the \textit{IXPE} point at 5 keV.}
    \label{fig:CenAmultiSED}
\end{figure}

The total flux and polarized Spectral Energy Distribution (SEDs) of Cen~A allowed me to determine the presence of the following processes:
\begin{itemize}
  \item \textbf{Radio}: synchrotron emission dominates, with a low ($< 1$\%) polarization degree due to the optically thick nature of the emission region and the associated polarization position angle may be perpendicular to the jet axis.
  \item \textbf{Millimeter}: starburst emission onsets and the coherent large-scale magnetic fields are dominated by randomly oriented fields, inducing a strong depolarization around the mm-break. 
  \item \textbf{Far-infrared}: dichroic emission from the dust lane and/or the AGN torus prevails over the core synchrotron polarization. The polarization angle is perpendicular to the jet axis.
  \item \textbf{Mid-infrared}: dichroic absorption modifies the core synchrotron polarization and imposes a polarization angle parallel to the jet axis
  \item \textbf{Near-infrared}: scattering of synchrotron seed core photons off the AGN polar outflows produces high polarization degrees associated with a polarization position angle perpendicular to the jet axis.  
  \item \textbf{Optical/near-ultraviolet}: the polarization of synchrotron seed core photons traveling through the dust lanes is altered by dichroic transmission from aligned dust grains. The polarization position angle rotates with decreasing wavelengths, marking the transition between synchrotron and inverse-Compton regimes.
  \item \textbf{X-rays\footnote{Polarization observed by \textit{IXPE} and analysed in the next subsection.}}: inverse-Compton scattering dominates. The polarization angle is parallel to the jet axis but the polarization degree is yet to be measured (constrained by our \textit{IXPE} study at values lower than 6.5\%).
  \item \textbf{$\gamma$-rays}: inverse-Compton scattering in the jets dominates. The polarization is yet to be measured.
\end{itemize}

\subsection*{Analysing the X-ray emission mechanism}
The upper limit to the degree of polarization measured by \textit{IXPE} (6.5\%, see Fig.~\ref{fig:CenAanalysis}) provides important information about the particle population responsible for generating the X-rays. Given the low polarization degrees measured for Cen~A in the radio and IR bands, however, it is not surprising that significant polarization was not measured in the \textit{IXPE} bandpass. The measured limits for the X-ray polarization degree remain consistent with expectations from synchrotron self-Compton emission, where the polarization degree of the Compton scattered X-rays is predicted to be $\sim 2-5$ times smaller than that of the synchrotron radiation acting as seed photons for Compton scattering. Thus with a significantly longer exposure with \textit{IXPE}, where MDP$_{99}$ could reach levels of $\sim 1\%$, the detection of polarization would be a strong argument in favor of synchrotron radiation as a source of seed photons for Compton scattering.   
The observed limits on X-ray polarization are in tension with a physical scenario where the X-ray emission arises from hadronic jets. Processes involving hadrons in jets have been suggested as a possible source of the higher than expected emission of Cen~A at TeV energies \cite{Abdo2010}, and such models applied to blazars predict X-ray polarization degrees as high as $\sim 50-80\%$, much higher than the observed limits allow \cite{Zhang2013}. 

\begin{figure}[!ht]
    \centering
    \begin{subfigure}{0.55\textwidth}
        \centering
        \includegraphics[width=0.9\textwidth]{./parts/appendix/CenA_Core_avg_pol.png}
        \captionsetup{width=0.9\textwidth}
        \caption{\footnotesize Analysis of the polarization components as a function of the confidence level for the emission from the core of Cen~A averaged on the 3 detector units of \textit{IXPE}.}
        \label{fig:CenApol}
    \end{subfigure}%
    \begin{subfigure}{0.45\textwidth}
        \centering
        \includegraphics[width=\textwidth]{./parts/appendix/CenA_img_pol.png}
        \captionsetup{width=0.9\textwidth}
        \caption{\footnotesize Imaging of the AGN core of Cen~A by \textit{IXPE} showing the contribution of each feature to the total detected flux.}
        \label{fig:CenAimg}
    \end{subfigure}
    \caption{Observed degree of polarization as a function of confidence level (left) and total flux map of Cen~A (right) as observed by IXPE.}
    \label{fig:CenAanalysis}
\end{figure}


\section{IC~5063 (\textit{HST/FOC})}
\hspace{\parindent}IC~5063 is a nearby\footnote{From the NASA/IPAC Extragalactic Database.} ($z = 1.011358$, $d \approx 4.27$~Gpc) elliptical, type II \cite{Inglis1993} galaxy. It is one of the most radio-loud ($P_{1.4 \text{GHz}} = 6.3 \cdot 10^{23} \; \text{W} \cdot \text{Hz}^{-1}$ \cite{Morganti1998}) Seyfert 2 galaxies in the local universe. It shows an ionizing radiation field with an “X” morphology \cite{Colina1991} and a complex system of dust lanes, likely due to merger remnants \cite{Morganti1998,Oosterloo2017}. High-resolution radio data (ATCA at 8 GHz \cite{Morganti1998}) reveal a triple radio structure ($1.3$ kpc) along the position angle (PA) of $\sim 295^\circ$ with a total flux density of $230$ mJy, consisting of a nuclear blob and two hot spots, i.e., termination points where the jets collide with the gas. Most of the flux ($195$ mJy) is emitted from the North-West radio hot spot. IC~5063 is a perfect laboratory to explore AGN interaction with the medium of its host galaxy: it is a peculiar system because the radio jets lie in the same plane as the \emph{HI} galactic disk (PA $\sim 300^\circ$ \cite{Danziger1981,Morganti1998}), allowing a full interaction between the mechanical energy released by the AGN and the host galaxy.\par
This AGN is also strongly obscured by both a dust lane in front of the galaxy and the dusty torus around its core. The latter have recently been observed thanks to the fact that the AGN is highly inclined with its host galaxy \cite{Maksym2020}.

\subsection*{IC~5063 and Cen~A: twin AGN}
\hspace{\parindent}Among the observed but not analyzed datasets in the \textit{HST/FOC} archives, IC~5063 got our attention as it shows characteristics very similar to Cen~A. Indeed, both of them are radio-loud AGNs with strong jets that are interacting with their respective host galaxy, but most importantly they are both obscured by a foreground dust lane. Their core emission is completely obscured and no one knows if the central source is dominated by thermal accretion onto a SMBH or by synchrotron emission by the jet bases. Because Cen~A was never observed by the \textit{HST/FOC} it is impossible to investigate it in the UV band, but we took the opportunity to use its twin to test the synchrotron origin predicted by \textit{IXPE} for Cen~A.

\subsection*{Total and polarized fluxes in UV}
\hspace{\parindent}On February 25$^\text{th}$ 1998, the \textit{HST/FOC} observed IC~5063 for $5261.875$ seconds through each polarizer filter ($0^\circ$, $60^\circ$ and $120^\circ$). This dataset has only one associated paper that does not make use of the polarization information that can be deduced from it \cite{Dasyra2015}. Thus, the following results consist in the first UV polarimetric analysis of IC~5063.\par
We used our pipeline to reduce and analyse this dataset comprising 3 observations. The resulting polarization map with vectors displayed at full scale to better study the pattern they form is shown in Fig. \ref{fig:IC5063UV}. The polarization vectors are displayed on-top of the intensity map for a confidence level on the polarization degree $\text{SNR}_P = \frac{\sigma_P}{P} \geq 3$ and on the flux intensity $\text{SNR}_I = \frac{\sigma_I}{I} \geq 60$, which corresponds to highly significant polarization detection only.\par
The UV intensity map allows us to reveal the morphology of the AGN and compare it to what was presented in previous papers: on the South-East, a jet and its lobe are revealed thanks to high fluxes in the UV band; in the center, the core of the AGN might be located in a heavily obscured region right to the South of the brightest total flux spot (remember that the SMBH is hidden by a torus, so we don't know it's real location); finally on the North-West part, a less intense jet and its lobe seems to be diverging in the upper part of a "X" pattern (the lower part being on the South-East of the SE lobe). When analysing the flux from these different regions we get that the SE lobe is $2.5$ times brighter than the NW lobe. This can be due to both less extinction from dust and more scattering by the medium.\par
The integrated values of polarization degree and angle on the $7$x$7$ arcseconds$^2$ of the \textit{HST/FOC} aperture of respectively $1.6$\% and $162^\circ$ can be surprising at first as we expect integrated polarization degree of $10$--$20$\% around Type 2 AGNs (see for example Fig. \ref{fig:NGC1068CapettiUs} and Fig. \ref{Afig:NGC1068analysis} for NGC~1068). This can be explained by a highly depolarized region around the center of the AGN plus the contamination by dichroic transmission through interstellar dust, which is coherent with our detected polarization components (see Fig. \ref{fig:IC5063ISP}). However, on the North-West extremity of the NW lobe we can see a centro-symmetric polarization pattern that is typical of the emission from the central core that is scattered on ionized polar winds onto our line-of-sight. This particular region has a polarization degree of $5.7$\% and a polarization angle of $11.6^\circ$, almost perpendicular to the jets direction. By taking the normal to the vectors in this region we can locate the obscured core of the AGN with great precision, even if it is hidden by an optically thick dust reservoir.

\begin{figure}[!ht]
    \centering
    \includegraphics[width=\textwidth]{./parts/appendix/IC5063_FOC_combine_FWHM020_pol.png}
    \caption{UV polarization map obtained with our new pipeline where we can see in intensity the location of both jets and lobes and the central core. The polarization vectors are all represented at full size to better study the patterns they form.}
    \label{fig:IC5063UV}
\end{figure}

\begin{figure}[!ht]
    \centering
    \includegraphics[width=0.8\textwidth]{./parts/appendix/ISP.png}
    \caption{Polarization degree and angle measurement as a function of the wavelength and color-coded by aperture size for the emission from IC~5063. The dotted line represent the expected polarization from scattering on interstellar dust.}
    \label{fig:IC5063ISP}
\end{figure}

\subsection*{Relation to radio and infrared maps}
\hspace{\parindent}To better understand the rest of the polarization patterns that does not bear the usual signature of an AGN and seem chaotic to us at first glance, we correlated to our results information from other wavelength (see Fig. \ref{fig:IC5063multiwav}). We use polarized radio flux measurements from ATCA (Fig. \ref{fig:IC5063Radio}) and near-infrared map of the AGN surroundings from HST (Fig. \ref{fig:IC5063IR}) to identify structures associated with radio emission and/or dust absorption around the core, jets, lobes and the host galaxy.\par
The radio emission identifies the approaching jet to be the North-West one. Its lobe emission is $16$ times brighter than the South-East lobe associated with the counter-jet (see Fig. \ref{fig:IC5063Radio}). This hierarchy in radio intensity is the opposite to what we see in the UV intensity maps, and can be explained by the fact that the former results from isotropic emission in the shocks at the boundaries of the lobes, while the latter results from scattering of the emission from the core on turbulent medium (less absorbed in the counter-jet associated lobe).\par
The inverted scale for the display of the near-IR map highlights the position of the dust clouds in the field-of-view (see Fig. \ref{fig:IC5063IR}). We can see that the region that is directly North of the AGN core in the UV map (see Fig. \ref{fig:IC5063UV}), where almost no UV flux is detected, correlates in IR to a foreground dust lane that absorbs the UV emission. We thus pinpoint with precision the regions of the AGN that are heavily polluted by the galaxy merger.

\begin{figure}[!ht]
    \centering
    \begin{subfigure}{0.5\textwidth}
        \centering
        \includegraphics[width=\textwidth]{./parts/appendix/IC5063_18GHz_overplot_forced.png}
        \captionsetup{width=0.9\textwidth}
        \caption{\footnotesize Superposition of our UV polarization map with radio contours at 18GHz by Morganti et al. \cite{Morganti1998}. This highlights the jet propagation through the host galaxy medium.}
        \label{fig:IC5063Radio}
    \end{subfigure}%
    \begin{subfigure}{0.5\textwidth}
        \centering
        \includegraphics[width=\textwidth]{./parts/appendix/IC5063_IR_overplot_forced.png}
        \caption{\footnotesize Superposition of a near-infrared map taken with \textit{HST/WFPC} with the polarization vectors from our UV map. This highlights the alignment of the polarization pattern along the foreground dust lane.}
        \label{fig:IC5063IR}
    \end{subfigure}
    \caption{Multiwavelength analysis of IC~5063 with (a) the UV polarization map overplotted with 18GHz radio contours, (b) a near-infrared map from the \textit{HST/WFPC} overplotted with our UV polarization vectors.}
    \label{fig:IC5063multiwav}
\end{figure}

\subsection*{Dissecting the AGN}
\hspace{\parindent}Correlating the UV polarization map to radio and infrared spatial features allowed us to emit a certain number of hypothesis to explain the different polarization patterns visible in the UV band. Beginning in the innermost regions of the AGN we can see in infrared and UV that the thermal emission from the core seems to be obscured by the putative dusty torus from the AGN model. Radiation manages to escape a few milliarcseconds North of the core by perpendicular scattering. A bit further, the path of the jets is completely depolarized in UV and this might be due to the jets pushing the surrounding material around, creating turbulences and removing the scattering medium from the jets axis. The depolarization can also be due to superposition of the perpendicular polarization angle coming from the synchrotron emission from the jets and scattering of the core emission on turbulent medium at the same location. This can also explain the centro-symmetric pattern on the North-West of the approaching lobe, where scattering on ionized winds is still possible as they have not yet been perturbed by the jet.\par
We explain the UV extinction and the aligned polarization vectors on the Northern part of the AGN by the presence of a foreground dust lane, visible in infrared, that produces polarization through forward scattering on aligned dust grains. This extinction and emission by aligned grains in the dust lane produces polarization by dichroic transmission, allowing us to characterize the mineralogy and geometry of the dust cloud.\par
Comparing the different sources of polarization to the integrated polarization (see Fig. \ref{fig:IC5063UV}) on the \textit{HST/FOC} aperture, we can say that the dominant mechanism could indeed be dichroic transmission on interstellar dust, but not necessarily from the Milky Way. It is rather due to the foreground dust lane that is located near the IC~5063 host galaxy. Its precise distance from the AGN is yet to be determined. A way to guess the proximity to the AGN would be to study the mechanism that align the dust grains in the cloud. Their alignment seems indeed to be parallel to the jets axis and this mean that there could be a mechanical alignment of the grains by kinetic pressure from the matter pushed around by the relativistic jets. Another scenario would imply a large scale magnetic field, similar to what have been observed in the infrared in the foreground dust lane of Cen~A \cite{Lopez-Rodriguez2021}.
