Search Publications
Ruling Out New Physics at Low Redshift as a Solution to the H0 Tension
Shafieloo, Arman; Keeley, Ryan E.
We make the case that there can be no low-redshift solution to the H0 tension. To robustly answer this question, we use a very flexible parametrization for the dark energy equation of state such that every cosmological distance still allowed by data exists within this prior volume. To then answer whether there exists a satisfactory solu…
Weighing the Local Interstellar Medium Using Gamma Rays and Dust
Widmark, Axel; Korsmeier, Michael; Linden, Tim
Cold gas forms a significant mass fraction of the Milky Way disk, but is its most uncertain baryonic component. The density and distribution of cold gas is of critical importance for Milky Way dynamics, as well as models of stellar and galactic evolution. Previous studies have used correlations between gas and dust to obtain high-resolution measur…
No Evidence for Axions from Chandra Observation of the Magnetic White Dwarf RE J0317-853
Safdi, Benjamin R.; Dessert, Christopher; Long, Andrew J.
Axions with couplings ga γ γ∼few ×10-11 GeV-1 to electromagnetism may resolve a number of astrophysical anomalies, such as unexpected ∼TeV transparency, anomalous stellar cooling, and x-ray excesses from nearby neutron stars. We show, however, that such axions are severely constrained by the nonobservation of x ray…
Galactic Potential and Dark Matter Density from Angular Stellar Accelerations
Buschmann, Malte; Safdi, Benjamin R.; Schutz, Katelin
We present an approach to measure the Milky Way (MW) potential using the angular accelerations of stars in aggregate as measured by astrometric surveys like Gaia. Accelerations directly probe the gradient of the MW potential, as opposed to indirect methods using, e.g., stellar velocities. We show that end-of-mission Gaia stellar acceleration data …
First Results on Dark Matter Substructure from Astrometric Weak Lensing
Van Tilburg, Ken; Weiner, Neal; Taki, Anna-Maria +1 more
Low-mass structures of dark matter (DM) are expected to be entirely devoid of light-emitting regions and baryons. Precisely because of this lack of baryonic feedback, small-scale substructures of the Milky Way are a relatively pristine testing ground for discovering aspects of DM microphysics and primordial fluctuations on subgalactic scales. In t…
Hunting Axion Dark Matter with Protoplanetary Disk Polarimetry
Tazaki, Ryo; Toma, Kenji; Fujita, Tomohiro
We find that the polarimetric observations of protoplanetary disks are useful to search for ultralight axion dark matter. Axion dark matter predicts the rotation of the linear polarization plane of propagating light, and protoplanetary disks are ideal targets to observe it. We show that a recent observation puts the tightest constraint on the axio…
X-Ray Signatures of Axion Conversion in Magnetic White Dwarf Stars
Safdi, Benjamin R.; Dessert, Christopher; Long, Andrew J.
White dwarf (WD) stars may radiate keV-energy axions produced in their stellar cores. This has been extensively studied as an extra channel by which WDs may cool, with some analyses even suggesting that axions can help explain the observed WD luminosity function. We show that the radiated axions may convert into x rays in the strong magnetic field…
Constraining a Thin Dark Matter Disk with G a i a
Safdi, Benjamin R.; Schutz, Katelin; Lin, Tongyan +1 more
If a component of the dark matter has dissipative interactions, it could collapse to form a thin dark disk in our Galaxy that is coplanar with the baryonic disk. It has been suggested that dark disks could explain a variety of observed phenomena, including periodic comet impacts. Using the first data release from the Gaia space observatory, we sea…
Astrometric Search Method for Individually Resolvable Gravitational Wave Sources with Gaia
Gilmore, Gerard; Mihaylov, Deyan P.; Moore, Christopher J. +1 more
Gravitational waves (GWs) cause the apparent position of distant stars to oscillate with a characteristic pattern on the sky. Astrometric measurements (e.g., those made by Gaia) provide a new way to search for GWs. The main difficulty facing such a search is the large size of the data set; Gaia observes more than one billion stars. In this Letter …