Using LSST Microlensing to Constrain Dark Compact Objects in Spherical and Disk Configurations

Abstract

The Legacy Survey of Space and Time (LSST) with the Vera Rubin Observatory will provide strong microlensing constraints on dark compact objects (DCOs) in our Galaxy. However, most current forecasts limit their analysis to Primordial Black Holes (PBH). It is unclear how well LSST microlensing will be able to constrain alternative models of DCOs with different Galactic spatial profile distributions at a subdominant DM fraction. In this work, we investigate how well LSST microlensing will constrain spherical or disk-like Galactic spatial distributions of DCOs, taking into account extended observing times, baryonic microlensing background, and sky distribution of LSST sources. These extensions represent significant improvements over existing microlensing forecasts in terms of both accuracy and versatility. We demonstrate this power by deriving new LSST sensitivity projections for DCOs in spherical and disk-like distributions. We forecast that LSST will be able to constrain one-solar-mass PBHs to have a DM fraction under 4.1 × 10−4. One-solar-mass objects in a dark disk distribution with the same dimensions as the Galactic disk will be constrained below 3.1 × 10−4, while those with m = 105 M ⊙ will be constrained to below 3.4 × 10−5. We find that compressed dark disks can be constrained up to a factor of ∼10 better than ones with identical dimensions to the baryonic disk. We also find that dark disks become less tightly constrained when they are tilted with respect to our own disk. This forecasting software is a versatile tool, capable of constraining any model of DCOs in the Milky Way with microlensing, and is made publicly available.

Simulating Atomic Dark Matter in Milky Way Analogs

“…Gravitational signatures of the dark disk depend sensitively on its morphology. For ADM-1 and ADM-2, the thin dark disk constraints from Kramer & Randall (2016), Schutz et al (2018), Buch et al (2019), andWidmark et al (2021) do not apply given the lack of a prominent dark disk with scale height 100 pc at the solar position in our simulations (see Figures D9-D11), but microlensing searches will be highly sensitive (Winch et al 2022).…”

Electromagnetic Signatures of Mirror Stars

“…We focus on electromagnetic signals of mirror stars, but microlensing surveys will also be highly sensitive in the near future; see Winch et al (2022). Furthermore, mirror stellar relics are expected to give rise to distinctive gravitationalwave signals from merger events, including mirror white dwarfs (Ryan & Radice 2022), mirror neutron stars (Hippert et al 2022(Hippert et al , 2023, and black holes with unusual masses sourced by ADM collapse (Pollack et al 2015;Shandera et al 2018;Singh et al 2021;Gurian et al 2022b;Fernandez et al 2024).…”

Dissipative Dark Substructure: The Consequences of Atomic Dark Matter on Milky Way Analog Subhalos

“…Because these subhalos lie within the disk region of MWlike galaxies and consist primarily of ADM clumps, which are dark compact objects at our simulations' resolution level, their abundance could be constrained from gravitational microlensing events (Winch et al 2022), in addition to the microlensing produced by the individual dark stars or ADM-sourced black holes. Microlensing from extended structures has been considered and could be applied to these compact subhalos (Croon et al 2020).…”