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arXiv · 2606.30715

Hunting Wandering 3<z<8 Black Holes: Spatial Offsets in Ionization Ratio and Continuum Emission

Urvi Thakurdesai·Anthony J. Taylor·Steven L. Finkelstein·Gene C. K. Leung·Oscar A. Chavez Ortiz·Jonathan R. Trump·Bren E. Backhaus·Nikko J. Cleri·Francesco D'Eugenio·Fabio Pacucci·Anton M. Koekemoer·Pablo Arrabal Haro·Micaela Bagley·Mark Dickinson·Jeyhan Kartaltepe·Casey Papovich·Nor Pirzkal
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Abstract

The early growth and assembly of supermassive black holes (SMBHs) remain key topics of interest in galaxy evolution. One of the scenarios predicted by theoretical models is that frequent minor mergers and asymmetric gas inflows may cause SMBHs to temporarily reside off-center within their host galaxies in the early universe. To observationally test this scenario, we investigate whether spatially offset ionization signatures-which may be indicative of active galactic nuclei (AGN)-can be identified. Using JWST NIRSpec PRISM spectroscopy from the Cosmic Evolution Early Release Science (CEERS) survey, we analyze the 2D spectra of 90 high-redshift galaxies (3 < z < 8), including two known broad-line AGN. By measuring key emission lines such as H{\alpha}, H{\beta}, [OIII]{\lambda}5007, [NeIII]{\lambda}3868, and [OII]{\lambda}{\lambda}3727, 3729 we derive spatial flux ratio profiles, and focus on [OIII]/H{\beta} as a tracer of high-ionization mechanisms that may indicate AGN activity. We identify 26 galaxies (~30% of the sample) with significant localized peaks in [OIII]/H{\beta}. Out of these 26 galaxies, 12 sources (~46%) exhibit significant spatial offsets between the peak [OIII]/H{\beta} ratio and the stellar continuum center. Six of these sources show the highest amount (> 1.5) pixel spatial offsets. This spatial offset between ionization structure and stellar centers offers a promising avenue to probe early SMBH evolution and its connection to galaxy formation.

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Urvi Thakurdesai, Anthony J. Taylor, Steven L. Finkelstein, Gene C. K. Leung, Oscar A. Chavez Ortiz, Jonathan R. Trump, Bren E. Backhaus, Nikko J. Cleri, Francesco D'Eugenio, Fabio Pacucci, Anton M. Koekemoer, Pablo Arrabal Haro, Micaela Bagley, Mark Dickinson, Jeyhan Kartaltepe, Casey Papovich, Nor Pirzkal. 2026-06-29. Hunting Wandering 3<z<8 Black Holes: Spatial Offsets in Ionization Ratio and Continuum Emission. https://arxiv.org/abs/2606.30715

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