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Widmark A, Korsmeier M, Linden T. Weighing the Local Interstellar Medium Using Gamma Rays and Dust. PHYSICAL REVIEW LETTERS 2023; 130:161002. [PMID: 37154658 DOI: 10.1103/physrevlett.130.161002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 01/24/2023] [Accepted: 03/16/2023] [Indexed: 05/10/2023]
Abstract
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 measurements of cold gas, but with large normalization uncertainties. We present a novel approach that uses Fermi-LAT γ-ray data to measure the total gas density, achieving a similar precision as previous works, but with independent systematic uncertainties. Notably, our results have sufficient precision to probe the range of results obtained by current world-leading experiments.
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Affiliation(s)
- Axel Widmark
- Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen N, Denmark
| | - Michael Korsmeier
- Stockholm University and The Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, 10691 Stockholm, Sweden
| | - Tim Linden
- Stockholm University and The Oskar Klein Centre for Cosmoparticle Physics, Alba Nova, 10691 Stockholm, Sweden
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Cyr-Racine FY, Ge F, Knox L. Symmetry of Cosmological Observables, a Mirror World Dark Sector, and the Hubble Constant. PHYSICAL REVIEW LETTERS 2022; 128:201301. [PMID: 35657861 DOI: 10.1103/physrevlett.128.201301] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 12/21/2021] [Accepted: 04/06/2022] [Indexed: 06/15/2023]
Abstract
We find that a uniform scaling of the gravitational free-fall rates and photon-electron scattering rate leaves most dimensionless cosmological observables nearly invariant. This result opens up a new approach to reconciling cosmic microwave background and large-scale structure observations with high values of the Hubble constant H_{0}: Find a cosmological model in which the scaling transformation can be realized without violating any measurements of quantities not protected by the symmetry. A "mirror world" dark sector allows for effective scaling of the gravitational free-fall rates while respecting the measured mean photon density today. Further model building might bring consistency with the two constraints not yet satisfied: the inferred primordial abundances of deuterium and helium.
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Affiliation(s)
- Francis-Yan Cyr-Racine
- Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87106, USA
| | - Fei Ge
- Department of Physics and Astronomy, University of California, Davis, California 95616, USA
| | - Lloyd Knox
- Department of Physics and Astronomy, University of California, Davis, California 95616, USA
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Buschmann M, Safdi BR, Schutz K. Galactic Potential and Dark Matter Density from Angular Stellar Accelerations. PHYSICAL REVIEW LETTERS 2021; 127:241104. [PMID: 34951772 DOI: 10.1103/physrevlett.127.241104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 06/13/2021] [Accepted: 10/28/2021] [Indexed: 06/14/2023]
Abstract
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 may be used to measure the potential of the MW disk at approximately 3σ significance and, if recent measurements of the solar acceleration are included, the local dark matter density at ∼2σ significance. Since the significance of detection scales steeply as t^{5/2} for observing time t, future surveys that include angular accelerations in the astrometric solutions may be combined with Gaia to precisely measure the local dark matter density and shape of the density profile.
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Affiliation(s)
- Malte Buschmann
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Benjamin R Safdi
- Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94720, USA
- Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Katelin Schutz
- Department of Physics & McGill Space Institute, McGill University, Montréal, QC H3A 2T8, Canada
- Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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de Salas PF, Widmark A. Dark matter local density determination: recent observations and future prospects. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2021; 84:104901. [PMID: 34496352 DOI: 10.1088/1361-6633/ac24e7] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
This report summarises progress made in estimating the local density of dark matter (ρDM,⊙), a quantity that is especially important for dark matter direct detection experiments. We outline and compare the most common methods to estimateρDM,⊙and the results from recent studies, including those that have benefited from the observations of the ESA/Gaia satellite. The result of most local analyses coincide within a range ofρDM,⊙≃0.4-0.6GeVcm-3=0.011-0.016M⊙/pc3, while a slightly lower range ofρDM,⊙≃0.3-0.5GeVcm-3=0.008-0.013M⊙/pc3is preferred by most global studies. In light of recent discoveries, we discuss the importance of going beyond the approximations of what we define as the ideal Galaxy (a steady-state Galaxy with axisymmetric shape and a mirror symmetry across the mid-plane) in order to improve the precision ofρDM,⊙measurements. In particular, we review the growing evidence for local disequilibrium and broken symmetries in the present configuration of the Milky Way, as well as uncertainties associated with the galactic distribution of baryons. Finally, we comment on new ideas that have been proposed to further constrain the value ofρDM,⊙, most of which would benefit from Gaia's final data release.
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Affiliation(s)
- Pablo F de Salas
- The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova, Stockholm SE-106 91, Sweden
| | - A Widmark
- Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Jagtvej 128, 2200 Copenhagen N, Denmark
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Foster JW, Kahn Y, Macias O, Sun Z, Eatough RP, Kondratiev VI, Peters WM, Weniger C, Safdi BR. Green Bank and Effelsberg Radio Telescope Searches for Axion Dark Matter Conversion in Neutron Star Magnetospheres. PHYSICAL REVIEW LETTERS 2020; 125:171301. [PMID: 33156637 DOI: 10.1103/physrevlett.125.171301] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/26/2020] [Accepted: 09/17/2020] [Indexed: 06/11/2023]
Abstract
Axion dark matter (DM) may convert to radio-frequency electromagnetic radiation in the strong magnetic fields around neutron stars. The radio signature of such a process would be an ultranarrow spectral peak at a frequency determined by the mass of the axion particle. We analyze data we collected from the Robert C. Byrd Green Bank Telescope in the L band and the Effelsberg 100-m Telescope in the L band and S band from a number of sources expected to produce bright signals of axion-photon conversion, including the Galactic center of the Milky Way and the nearby isolated neutron stars RX J0720.4-3125 and RX J0806.4-4123. We find no evidence for axion DM and are able to set constraints on the existence of axion DM in the highly motivated mass range between ∼5 and 11 μeV with the strongest constraints to date on axions in the ∼10-11 μeV range.
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Affiliation(s)
- Joshua W Foster
- Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Yonatan Kahn
- University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Oscar Macias
- Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, Kashiwa, Chiba 277-8583, Japan
- GRAPPA Institute, Institute of Physics, University of Amsterdam, 1098 XH Amsterdam, Netherlands
| | - Zhiquan Sun
- Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Ralph P Eatough
- National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100101, People's Republic of China
- Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany
| | - Vladislav I Kondratiev
- ASTRON, the Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, Netherlands
- Astro Space Centre, Lebedev Physical Institute, Russian Academy of Sciences, Profsoyuznaya Street 84/32, Moscow 117997, Russia
| | - Wendy M Peters
- Naval Research Laboratory, Remote Sensing Division, Code 7213, Washington, DC 20375-5320, USA
| | - Christoph Weniger
- GRAPPA Institute, Institute of Physics, University of Amsterdam, 1098 XH Amsterdam, Netherlands
| | - Benjamin R Safdi
- Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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Abstract
The cold dark-matter model successfully explains both the emergence and evolution of cosmic structures on large scales and, when we include a cosmological constant, the properties of the homogeneous and isotropic Universe. However, the cold dark-matter model faces persistent challenges on the scales of galaxies. Indeed, N-body simulations predict some galaxy properties that are at odds with the observations. These discrepancies are primarily related to the dark-matter distribution in the innermost regions of the halos of galaxies and to the dynamical properties of dwarf galaxies. They may have three different origins: (1) the baryonic physics affecting galaxy formation is still poorly understood and it is thus not properly included in the model; (2) the actual properties of dark matter differs from those of the conventional cold dark matter; (3) the theory of gravity departs from General Relativity. Solving these discrepancies is a rapidly evolving research field. We illustrate some of the solutions proposed within the cold dark-matter model, and solutions when including warm dark matter, self-interacting dark matter, axion-like particles, or fuzzy dark matter. We also illustrate some modifications of the theory of gravity: Modified Newtonian Dynamics (MOND), MOdified Gravity (MOG), and f(R) gravity.
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Ravi A, Langellier N, Phillips DF, Buschmann M, Safdi BR, Walsworth RL. Probing Dark Matter Using Precision Measurements of Stellar Accelerations. PHYSICAL REVIEW LETTERS 2019; 123:091101. [PMID: 31524456 DOI: 10.1103/physrevlett.123.091101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 06/05/2019] [Indexed: 06/10/2023]
Abstract
Dark matter comprises the bulk of the matter in the Universe, but its particle nature and cosmological origin remain mysterious. Knowledge of the dark matter density distribution in the Milky Way Galaxy is crucial both to our understanding of the standard cosmological model and for grounding direct and indirect searches for the particles comprising dark matter. Current measurements of Galactic dark matter content rely on model assumptions to infer the forces acting upon stars from the distribution of observed velocities. Here, we propose to apply the precision radial velocity method, optimized in recent years for exoplanet astronomy, to measure the change in the velocity of stars over time, thereby providing a direct probe of the local gravitational potential in the Galaxy. Using numerical simulations, we develop a realistic strategy to observe the differential accelerations of stars in our Galactic neighborhood with next-generation telescopes, at the level of 10^{-8} cm/s^{2}. Our simulations show that detecting accelerations at this level with an ensemble of 10^{3} stars requires the effect of stellar noise on radial velocity measurements to be reduced to <10 cm/s. The measured stellar accelerations may then be used to extract the local dark matter density and morphological parameters of the density profile.
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Affiliation(s)
- Aakash Ravi
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
| | - Nicholas Langellier
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
| | - David F Phillips
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
| | - Malte Buschmann
- Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Benjamin R Safdi
- Leinweber Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Ronald L Walsworth
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA
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