The majority of my work focuses on finding pairs of supermassive black holes, and learning more about their preferential environments and evolution through mergers. I connect the X-ray activity of merging supermassive black holes with the optical and IR properties of their host galaxies. Below I highlight some recent results.
Investigating the Accretion Nature of Binary Supermassive Black Hole Candidate SDSS J025214.67-002813.7
SDSS J025214.67−002813.7, is a system that has been previously classified as a binary active galactic nucleus (AGN) candidate based on periodic signals detected in the optical light curves. Using available radio−X-ray observations of the system, we investigated whether it was likely a merging SMBH system. Analyzing new observations from XMM-Newton and NuSTAR, and compiling a full multiwavelength spectral energy distribution SED, we also search for signs of circumbinary accretion, such as a “notch” in the continuum due to the presence of minidisks. We found that the radio–X-ray emission agrees with the SED of a standard, radio-quiet, AGN. However, future studies of the expected hard X-ray emission associated with binary AGNs (especially in the unequal-mass regime) will allow for more rigorous analyses of the binary AGN hypothesis.
Read more here: Foord et al. 2022
AGN Triality in Triple Mergers: Faint X-ray Sources and Multi-wavelength Classifications
The overarching goal on this analysis was to identify new triple AGN, which have been theorized to play an important role in the timescales for merging supermassive black holes. However, we hoped to find a range of AGN activity (from 0 AGN, up to 3), in order to measure differences, and possible links, between SMBH triggering and environmental parameters. We found that 1 triple merger has a single AGN; we discovered, for the first time, 4 likely dual AGN; and we confirmed one triple AGN system. Combining the archival Chandra observations with existing SDSS, WISE, and VLA observations we found a trend of increasing levels of gas as a function of increasing dust, reflecting that the motions of gas and dust are coupled in merging environments, where large amounts of both can be funneled into the active central region. Additionally, the one triple AGN system in our sample has the highest levels of gas and dust, while the dual AGN candidates all have lower levels; these results are consistent with theoretical merger simulations that suggest higher levels of nuclear gas are more likely to active AGN in mergers.
Four new strong dual AGN candidates discovered in Foord et al. 2021a. I plot the unbinned Chandra data, where counts associated with the primary AGN (yellow circles), secondary AGN (purple squares), and background (triangles). The optical contours of the host galaxy are shown in pink contours.
Using avaible mid-IR observations from WISE, Foord et al. 2021b found a trend of increasing levels of dust (y-axis) as a function of increasing gas levels (as determined by fitting the X-ray spectrum via the available Chandra data, x-axis). Next to each marker I denote how many X-ray AGN were detected in each system. Interestingly, the one triple X-ray AGN system had higher levels of gas and dust than the dual AGN.