arXiv subjects

Julia M. Sisk-Reynes

Publications and source records attributed to Julia M. Sisk-Reynes.

3 recordsLinked to original sources

arXiv2026

Chandra X-ray Spectral Evidence of the Dual AGN Nature of the Gravitational lens MG B2016+112 at z=3.273 with 175 pc separation

We use a new 175 ks Chandra X-ray observation of the z=3.273 radio-loud gravitational lens system MG B2016+112 to present definitive X-ray spectral evidence that it contains a dual active galactic nucleus (AGN). With a projected separation of 175 parsecs, this is the tightest separation confirmed AGN pair at high redshift. Prior multi-epoch very long baseline interferometry (VLBI) and archival Chandra data had revealed two distinct emitters, but could not rule out a single AGN with a complex, highly magnified jet. Our new Chandra observations allow a separate spectral analysis of each source. We find strong intrinsic absorption (N_H > 4 x 10^22 cm^-2, 3 sigma confidence) at the source redshift for the highly magnified source inside the caustic. This identifies it as an obscured AGN. In addition to the previously known type II AGN outside the caustic, this confirms a compact dual AGN system in MG B2016+112. On-going and future surveys using facilities such as Euclid, SKA, and the Rubin and Roman observatories will uncover more such systems, probing SMBH evolution and gravitational wave precursors.

astro-ph.HE↗

arXiv2026

Spin Demographics of Active Supermassive Black Holes: Updated Estimates from X-ray reflection and Future opportunities

Understanding the growth of supermassive black holes (SMBHs) requires observational constraints on how their angular momentum (or spin) varies with mass, since the relative importance of coherent accretion, chaotic accretion, and mergers will be reflected in SMBH spin populations. Here we present an updated compilation of reflection-based SMBH spin measurements from the literature and assemble a set of ancillary quantities of interest for each SMBH (including redshift, Eddington ratio, and X-ray luminosity). No obvious apparent correlation between the Eddington-scaled accretion rate and the black hole spin is seen, noting that formal statistical tests are beyond the scope of this review. We discuss the limitations of using this heterogeneous mass--spin sample to test predictions of SMBH growth from semi-analytic models and cosmological simulations, emphasizing the need for a more uniform sample. We then highlight the encouraging prospects enabled by the next-generation NewAthena X-ray flagship observatory. Finally, we summarize how hierarchical Bayesian population inference applied to observed SMBH mass--spin populations will constitute a powerful framework for confirming tentative mass--spin trends in future samples.

astro-ph.HE↗

arXiv2023

Current and Future constraints on Very-Light Axion-Like Particles from X-ray observations of cluster-hosted Active Galaxies

We discuss our recent constraints on the coupling of Very-Light Axion-Like Particles (of masses $<$$ 10^{-12} \ \mathrm{eV}$) to electromagnetism from $Chandra$ observations of the cluster-hosted Active Galactic Nuclei (AGN) H1821+643 and NGC1275. In both cases, the inferred high-quality AGN spectra excluded all photon-ALP couplings $g_\mathrm{aγ} > (6.3 - 8.0) \times 10^{-13} \ {\mathrm{GeV}}^{-1}$ at the $99.7\%$ level, respectively, based on the non-detection of spectral distortions attributed to photon-ALP inter-conversion along the cluster line-of-sight. Finally, we present the prospects of tightening current bounds on such ALPs by up to a factor of 10 with next-generation X-ray observatories such as $Athena$, $AXIS$ and $LEM$ given their improved spectral and spatial resolution and collecting area compared to current missions.

astro-ph.HE↗