arXiv subjects

J. McKaig

Publications and source records attributed to J. McKaig.

3 recordsLinked to original sources

arXiv2026

Science of High Resolution X-ray Imaging

This report summarizes potential studies of the Hi-ReX Science Analysis Group for an Ultra-High Angular Resolution X-ray Observatory. Many potential science cases are presented, spanning a range of astrophysical topics from solar system planets and exoplanets to supermassive black holes and cosmology. These cases demonstrate the value of X-ray imaging beyond current capabilities with an aim toward milli-arcsecond and micro-arcsecond angular scales. There is an imaging gap between the current capability of the best X-ray imaging telescope, the Chandra X-ray Observatory, compared to that of instruments across the electromagnetic spectrum. Next-generation, ultra-high angular resolution X-ray imaging will close this gap and transform our understanding of the universe and fundamental physics.

astro-ph.HE↗

arXiv2026

A High Resolution Search for Dual AGN Candidates in Mergers: A Pre-Selection Strategy using Keck AO

Accreting supermassive black holes (SMBHs) in galaxy mergers with separations $<$ 1 kpc are crucial to our understanding of SMBH growth, galaxy evolution, and SMBH binary evolution. Despite their importance, few are known, and most have been discovered serendipitously. In this work, we develop and test a method to systematically pre-select candidate advanced mergers likely to contain unresolved sub-kpc nuclear substructure constituting high-priority dual-AGN candidates for follow-up spectroscopy. By exploiting the survey area and astrometric precision of the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS), we identified 46 nearby advanced mergers that have red WISE colors ($W_1-W_2>0.5$) indicative of accretion activity and significant sub-arcsecond offsets between their optical and infrared coordinates as measured by SDSS and WISE. We conducted high-resolution adaptive optics (AO) observations with the Keck NIRC2 camera in the $K_p$ band ($2.124 μm$, $Δλ= 0.351 μm$) to search for unresolved substructure suggested by the optical-to-infrared offsets. We find that 20/46 (43\%) of the sample shows substructure tracing the SDSS/WISE offset and unresolved by SDSS , representing a higher yield than previous pre-selection techniques such as double-peaked [O III] or hard X-ray selection. These results demonstrate that the SDSS/WISE offset method provides an efficient pathway for identifying late-stage mergers and dual-AGN candidates for spectroscopic confirmation. Archival optical Hubble Space Telescope (HST) imaging reveals that substructure identified with Keck is often missed in the optical or erroneously identified due to partial obscuration, underscoring the importance of infrared studies of late-stage mergers.

astro-ph.GA↗

arXiv2025

The SDSS-V Black Hole Mapper Reverberation Mapping Project: Light Echoes of the Coronal Line Region in a Luminous Quasar

We present a reverberation mapping analysis of the coronal line [Ne V]$λ$3427 emitting region of the quasar COS168 (SDSS J095910.30+020732.2). [Ne V]$λ$3427 is known as one of the "coronal lines," which are a species of emission lines present in AGN spectra with high ionization potentials ($\geq$ 100 eV) that can serve as tracers for AGN activity. The spatial extent of the coronal line region has been studied with only spatial resolving techniques that are not sensitive to the innermost regions of AGN. Through our reverberation mapping analysis of [Ne V]$λ$3427, we measure a nominal `optimal emission radius' for [Ne V]$λ$3427 of $381.1^{+16}_{-22}$ light days (observed-frame). We place the coronal line region in context with other AGN regions by comparing it with the characteristic radius of H$α$, the dust-sublimation radius, and the dusty torus. The coronal line region is located at a larger radius from the black hole than the characteristic radius of the dusty torus, measured using a torus-radius luminosity relationship. The virial product ($v^2 R/G$) of both H$α$ and [Ne V]$λ$3427 is consistent within the uncertainties, implying that the coronal line region, as probed by the [Ne V]$λ$3427 line, may be in a virialized orbit that is dominated by the gravitational potential of the black hole. This plausibly suggests that coronal lines could be an effective method for estimating black hole masses.

astro-ph.GA↗