Rogue worlds meet the dark side: revealing terrestrial-mass primordial black holes with the Nancy Grace Roman Space Telescope

Abstract

Gravitational microlensing is one of the strongest observational techniques to observe non-luminous astrophysical bodies. Existing microlensing observations provide tantalizing evidence of a population of low-mass objects whose origin is unknown. These events may be caused by terrestrial-mass free-floating planets or by exotic objects such as primordial black holes. However, the nature of these objects cannot be resolved on an event-by-event basis, as the induced light curve is degenerate for lensing bodies of identical mass. One must instead statistically compare \textit{distributions} of lensing events to determine the nature of the lensing population. While existing surveys lack the statistics required to identify multiple subpopulations of lenses, this will change with the launch of the Nancy Grace Roman Space Telescope. Roman's Galactic Bulge Time Domain Survey is expected to observe hundreds of low-mass microlensing events, enabling a robust statistical characterization of this population. In this paper, we show that by exploiting features in the distribution of lensing event durations, Roman will be sensitive to a subpopulation of primordial black holes hidden amongst a background of free-floating planets. Roman's reach will extend to primordial black hole dark matter fractions as low as $f_{\text{PBH}}=10^{-4}$ at peak sensitivity, and will be able to conclusively determine the origin of existing ultrashort-timescale microlensing events. A positive detection would provide evidence that a significant fraction of the cosmological dark matter consists of macroscopic, non-luminous objects.

11 pages, 6 figures

References in corpus (12)

• Constraints on Earth-mass primordial black holes from OGLE 5-year microlensing events
• Primordial black hole dark matter from single field inflation
• Microlensing and dynamical constraints on primordial black hole dark matter with an extended mass function
• Primordial Black Holes as Dark Matter Candidates
• Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey II: Free-Floating Planet Detection Rates
• Primordial black holes from scalar field evolution in the early universe
• The finite source size effect and the wave optics in gravitational lensing
• A Parametric Galactic Model toward the Galactic Bulge Based on Gaia and Microlensing Data
• The origin of free-floating planets
• Free-Floating planet Mass Function from MOA-II 9-year survey towards the Galactic Bulge
• Constraints on sub-terrestrial free-floating planets from Subaru microlensing observations
• Terrestrial and Neptune mass free-floating planet candidates from the MOA-II 9-year Galactic Bulge survey

Cited by in corpus (11)

• Limits on planetary-mass primordial black holes from the OGLE high-cadence survey of the Magellanic Clouds
• Primordial Black Holes from Axion Domain Wall Collapse
• Slaying Axion-Like Particles via Gravitational Waves and Primordial Black Holes from Supercooled Phase Transition
• Searching for Exploding Black Holes
• New Light on Dark Extended Lenses with the Roman Space Telescope
• Picolensing as a Probe of Primordial Black Hole Dark Matter
• Primordial Black Holes and Second-order Gravitational Waves in Axion-like Hybrid Inflation
• Dimming Starlight with Dark Compact Objects
• Prospects for Reconstructing the Free-floating Planet Mass Function at the Population Level with the Nancy Grace Roman Space Telescope
• Detection prospects for the GW background of Galactic (sub)solar mass primordial black holes
• Astrometric microlensing probes of the isolated neutron star population with Roman