Gemini Multi-Object Spectrograph Integral Field Unit Spectroscopy of the Double-peaked Broad Emission Line of a Red Active Galactic Nucleus

TL;DR

This study uses integral field spectroscopy to analyze a red AGN with double-peaked broad emission lines, providing evidence for potential dual supermassive black holes separated by about 250 parsecs, and discusses implications for SMBH merger detection.

Contribution

First spatially resolved spectroscopy of a red AGN with double-peaked lines, exploring SMBH merger scenarios and spatial separation uncertainties.

Findings

Confirmed two kinematically separated BEL peaks at 3000 km/s.

Estimated SMBH masses of approximately 10^8.92 and 10^7.13 solar masses.

Spatial separation of BEL components is around 250 parsecs, with model-dependent uncertainties.

Abstract

Galaxy mergers are expected to produce multiple supermassive black holes (SMBHs) in close-separation, but the detection of such SMBHs has been difficult. 2MASS J165939.7$+$183436 is a red active galactic nucleus (AGN) that is a prospective merging SMBH candidate owing to its merging features in Hubble Space Telescope imaging and double-peaked broad emission lines (BELs). Herein, we report a Gemini Multi-Object Spectrograph Integral Field Unit observation of a double-peaked broad H$\alpha$ line of 2MASS J165939.7$+$183436. Furthermore, we confirm the existence of two BEL peaks that are kinematically separated by 3000\,$\rm km\,s^{-1}$, with the SMBH of each BEL component weighing at $10^{8.92\pm0.06}\,M_{\rm \odot}$ and $10^{7.13\pm0.06}\,M_{\rm \odot}$, if they arise from independent BELs near the two SMBHs. The BEL components were not separated at $>0\farcs1$; however, under several plausible assumptions regarding the fitting of each spaxel, the two components are found to be spatially separated at $0\farcs085$ ($\sim250$\,pc). Different assumptions for the fitting can lead to a null ($< 0\farcs05$) or a larger spatial separation ($\sim0\farcs15$). Given the uncertainty regarding the spatial separation, various models, such as the disk emitter and multiple SMBH models, are viable solutions to explain the double BEL components. These results will promote future research for finding more multiple SMBH systems in red AGNs, and higher-resolution imaging validates these different models.