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A close quasar pair in a disk-disk galaxy merger at z = 2.17
Yu-Ching Chen1,2, Xin Liu3,4, Adi Foord5
1Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
Nature
|April 5, 2023
Summary
Astronomers discovered the first kpc-scale dual quasar system at cosmic noon, SDSS J0749+2255, hosted by a galaxy merger. This finding provides crucial insights into supermassive black hole evolution during peak cosmic activity.
Area of Science:
- * Astronomy and Astrophysics
- * Galaxy Evolution
- * Cosmology
Background:
- * Galaxy mergers are known to produce pairs of supermassive black holes (SMBHs).
- * These SMBH pairs can be observed as dual quasars when both are actively accreting, particularly at kiloparsec (kpc)-scale separations.
- * While kpc-scale dual active galactic nuclei have been found in low-redshift mergers, no unambiguous dual quasar has been identified at cosmic noon (z ≈ 2).
Purpose of the Study:
- * To report the discovery and characterization of a kpc-scale dual-quasar system at cosmic noon.
- * To investigate the host galaxy properties and merger evidence for this system.
- * To understand the implications for supermassive black hole formation and evolution.
Main Methods:
- * Multiwavelength observations of the Sloan Digital Sky Survey (SDSS) J0749+2255.
- * Analysis of extended host galaxies and low-surface-brightness tidal features.
- * Examination of quasar nuclei separation and host galaxy morphology.
Main Results:
- * Identification of SDSS J0749+2255 as a kpc-scale (3.8 kpc separation) dual-quasar system at redshift z = 2.17.
- * Discovery of extended host galaxies and tidal features, confirming a galaxy merger.
- * Observation that the host galaxies are massive, compact, and disk-dominated, lacking prominent stellar bulges.
Conclusions:
- * This is the first unambiguous kpc-scale dual-quasar system found at cosmic noon.
- * The host galaxy properties suggest that SMBHs may form before their host stellar bulges.
- * The system is on a trajectory to potentially form a gravitationally bound binary SMBH within approximately 0.22 Gyr.
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