arXiv subjects

Daniele Tagliacozzo

Publications and source records attributed to Daniele Tagliacozzo.

4 recordsLinked to original sources

arXiv2026

X-ray polarization of the Compton-thin Seyfert galaxy NGC 5506 with IXPE

We report on the observation of the Compton-thin Seyfert galaxy NGC~5506 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation, with a net observing time of 975~ks, was partly simultaneous with \textit{NuSTAR} (52~ks) and \textit{XMM-Newton} (37~ks). Using a simple baseline model with IXPE data only, we find an upper limit on the 2--8~keV polarization fraction at the $99\%$ confidence level: $Π<3.1\%$. We then performed a spectropolarimetric analysis combining data from the three X-ray observatories. While pure spectral modeling confirms the presence of both relativistic and cold distant reflection, in addition to the primary continuum power law, their contributions lead to somewhat different constraints on the coronal $Π$, depending on the specific assumptions. We also performed Monte Carlo simulations with the radiative transfer code \texttt{MONK}, exploring various coronal geometries. Comparing these results with the IXPE data, and assuming a radially extended corona, as suggested by previous observations of similar sources, the corresponding polarization upper limits require inclination angles below 40°.

astro-ph.HE↗

arXiv2026

XPE and VLT /FORS2 polarimetry challenge the Seyfert-1.9 classification of MCG-05-23-16

We report the third observation of the Seyfert-1.9 active galactic nucleus (AGN) MCG-05-23-16 with the Imaging X-ray Polarimetry Explorer (\textit{IXPE}), together with optical spectro-polarimetry obtained at the Very Large Telescope (VLT), and combined with archival near-ultraviolet, optical and near-infrared polarimetric data. No X-ray polarization was detected in the 2-8 keV band, with a 99\% confidence upper limit of $\leq$2.9\%, further reduced to $\leq$2.5\% when combined with the two past IXPE observations of the same target. Monte Carlo simulations suggest that equatorial coronal models are disfavored if the AGN is indeed a type-1.9/2 AGN, but coronae coplanar to the accretion disk remain consistent if the source is less inclined than previously assumed. \textit{VLT}/FORS2 data reveal a typical type-2 spectrum in total flux, a broad H$α$ line in polarized flux, and strongly wavelength dependent polarization degree and angle, rotating by nearly 70$^\circ$ across the optical band. Comparison with historical measurements confirms long-term stability of the polarization spectrum and a $\sim$90$^\circ$ rotation in the near-ultraviolet. Interpreting the multi-wavelength polarization relative to the AGN ionization axis indicates that the main obscurer is not a compact circumnuclear torus, but a distant kpc-scale dust lane crossing the galaxy. This result implies that MCG-05-23-16 is in fact a type-1 AGN seen through foreground dust. The low X-ray column density becomes consistent with the absence of polarization, provided that the nuclear inclination is low.

astro-ph.HE↗

arXiv2025

First X-ray polarimetric view of a Low-Luminosity Active Galactic Nucleus: the case of NGC 2110

Low-Luminosity Active Galactic Nuclei (LLAGN) provides a unique view of Comptonization and non-thermal emission from accreting black holes in the low-accretion rate regime. However, to decipher the exact nature of the Comptonizing corona in LLAGN, its geometry and emission mechanism must be understood beyond the limits of spectro-timing techniques. Spectro-polarimetry offers the potential to break the degeneracies between different coronal emission models. Compton-thin LLAGN provide an opportunity for such spectro-polarimetric exploration in the 2-8 keV energy range using IXPE. In this work, we carry out a spectro-polarimetric analysis of the first IXPE observation, in synergy with a contemporaneous NuSTAR observation, of an LLAGN: NGC 2110. Using 554.4 ks of IXPE data from October 2024, we constrain the 99% upper limit on the Polarization Degree (PD) to be less than 8.3% assuming the corresponding Polarization Angle (PA) to be aligned with the radio jet, and less than 3.6% if in the perpendicular direction. In the absence of a significant PD detection, the PA remains formally unconstrained, yet the polarization significance contours appear to be aligned with the radio jet, tentatively supporting models in which the corona is radially extended in the plane of the disk. We also carry out detailed Monte Carlo simulations using MONK and STOKES codes to test different coronal models against our results and compare the polarization properties between NGC 2110 and brighter Seyferts.

astro-ph.HE↗

arXiv2023

A remarkably stable accretion disc in the Seyfert galaxy MCG-5-23-16

MCG-5-23-16 is a Seyfert 1.9 galaxy at redshift z=0.00849. We analyse here the X-ray spectra obtained with XMM-Newton and NuSTAR data, which are the first contemporaneous observations with these two X-ray telescopes. Two reflection features, producing a narrow core and a broad component of the Fe K$α$, are clearly detected in the data. The analysis of the broad iron line shows evidence of a truncated disc with inner radius $R_{\rm in}=40^{+23}_{-16}$ $R_g$ and an inclination of $41^{+9}_{-10}$ $^\circ$. The high quality of the NuSTAR observations allows us to measure a high energy cut-off at $E_{\rm cut}=131^{+10}_{-9}$ keV. We also analyse the RGS spectrum, finding that the soft X-ray emission is produced by two photoionised plasma emission regions, with different ionisation parameters and similar column densities. Remarkably, the source only shows moderate continuum flux variability, keeping the spectral shape roughly constant in a time scale of $\sim20$ years.

astro-ph.HE↗