Astro2020 science white paper: The gravitational wave view of massive black holes

Abstract

Coalescing, massive black-hole (MBH) binaries are the most powerful sources of gravitational waves (GWs) in the Universe, which makes MBH science a prime focus for ongoing and upcoming GW observatories. The Laser Interferometer Space Antenna (LISA) -- a gigameter scale space-based GW observatory -- will grant us access to an immense cosmological volume, revealing MBHs merging when the first cosmic structures assembled in the Dark Ages. LISA will unveil the yet unknown origin of the first quasars, and detect the teeming population of MBHs of $10^4-10^7$ solar masses. forming within protogalactic halos. The Pulsar Timing Array, a galactic-scale GW survey, can access the largest MBHs the Universe, detecting the cosmic GW foreground from inspiraling MBH binaries of about 10^9 solar masses. LISA can measure MBH spins and masses with precision far exceeding that from electromagnetic (EM) probes, and together, both GW observatories will provide the first full census of binary MBHs, and their orbital dynamics, across cosmic time. Detecting the loud gravitational signal of these MBH binaries will also trigger alerts for EM counterpart searches, from decades (PTAs) to hours (LISA) prior to the final merger. By witnessing both the GW and EM signals of MBH mergers, precious information will be gathered about the rich and complex environment in the aftermath of a galaxy collision. The unique GW characterization of MBHs will shed light on the deep link between MBHs of $10^4-10^{10}$ solar masses and the grand design of galaxy assembly, as well as on the complex dynamics that drive MBHs to coalescence.

5 pages, 2 figures submitted to the Astro2020 Decadal

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Cited by in corpus (8)

• Electromagnetic Counterparts to Massive Black Hole Mergers
• Implications for the Supermassive Black Hole Binaries from the NANOGrav 15-year Data Set
• Gravitational wave sources in our Galactic backyard: Predictions for BHBH, BHNS and NSNS binaries detectable with LISA
• Unveiling early black hole growth with multi-frequency gravitational wave observations
• Chasing Super-Massive Black Hole merging events with $Athena$ and LISA
• An Enhanced Massive Black Hole Occupation Fraction Predicted in Cluster Dwarf Galaxies
• Can Einstein (rings) surf Gravitational Waves?
• Preliminary census of galaxies in the LISA localisation volume: I. Searching for LISA candidate massive black hole binary merger hosts using Sloan Digital Sky Survey photometry