Statistics of the projected angles between the black-hole spin and the host-galaxy rotation axes from NewHorizon

TL;DR

This study uses high-resolution cosmological simulations to analyze the projected alignment between black hole spins and host galaxy orientations, finding a significant tendency for alignment that aligns with recent observational data.

Contribution

It extends previous work by analyzing 2D projected angles using synthetic images, enabling direct comparison with observations and incorporating kinematic data for better insights.

Findings

AGN jets tend to align with host galaxy orientations

Stronger alignment observed with kinematic position angles

Results agree with recent VLBI and optical imaging observations

Abstract

Understanding the alignment between AGN jets and their host galaxies is crucial for interpreting AGN unification models, jet feedback processes, and the co-evolution of galaxies and their central black holes (BH). In this study, we use the high-resolution cosmological zoom-in simulation NewHorizon, which self-consistently evolves BH mass and spin, to statistically examine the relationship between AGN jet orientation and host galaxy structure. Building upon our previous work, we extend the analysis of projected (2-d) alignment angles to facilitate more direct comparisons with recent observational studies. In our methodology, galaxy orientations are estimated using optical position angles derived from synthetic DESI-LS and Euclid images, while BH spin vectors serve as proxies for AGN jet directions. From a carefully selected sample of 100 BH-galaxy systems at low redshift, we generate a catalog of 5,000 mock optical images using a Monte Carlo approach that samples random viewing angles and redshifts. Our results reveal a statistically significant tendency for AGN jets to align with the orientation of their host galaxies, consistent with recent observations combining Very Long Baseline Interferometry (VLBI) and optical imaging of nearby AGNs. Furthermore, we find a slightly stronger alignment when using kinematic position angles derived from synthetic MaNGA-like stellar velocity fields. These findings underscore the importance of combining morphological, kinematic, and polarimetric information to disentangle the complex interplay between black hole spin evolution, accretion mode, and the galactic environment in shaping the direction of relativistic jets.