Astrophysical Searches and Constraints on Ultralight Bosonic Dark Matter

Abstract

Starting from the evidence that dark matter (DM) indeed exists and permeates the entire cosmos, various bounds on its properties can be estimated. Beginning with the cosmic microwave background and large scale structure, we summarize bounds on the ultralight bosonic dark matter (UBDM) mass and cosmic density. These bounds are extended to larger masses by considering galaxy formation and evolution, and the phenomenon of black hole superradiance. We then discuss the formation of different classes of UBDM compact objects including solitons/axion stars and miniclusters. Next, we consider astrophysical constraints on the couplings of UBDM to Standard Model particles, from stellar cooling (production of UBDM) and indirect searches (decays or conversion of UBDM). Throughout, there are short discussions of "hints and opportunities" in searching for UBDM in each area. Astrophysical search channelsAstrophysics and cosmology, as outlined in Chapter 1, give convincing evidence that dark matter (DM) exists in the form of new particles beyond the Standard Model of particle physics. The space of possible theories in Chapter 2, even for the subclass of ultralight bosonic DM (UBDM) models considered in this book, is vast. Beyond the basic fact of the existence of DM, astrophysics can be used to reign in this vast theoretical parameter space, with a view to direct detection and measurement of model parameters.The most basic astrophysical route to constrain UBDM is via the relic density. There are three channels for UBDM production:1. Coherent field oscillations. a. Vacuum realigment. b. Topological defect decay.2. Thermal production. 3. Non-thermal production by direct decay.

Fuzzy Dark Matter Candidates from String Theory

“…In what follows we wrap up all the results coming from the previous sections and we compare our findings with current and future experimental constraints. As already mentioned, empirical bounds coming from Lyman-α forest, black hole superradiance and ultrafaint dwarf galaxies that are DM dominated put strong constraints on the vanilla FDM model, ruling out a non-negligible area of the parameter space [11][12][13][14][15][16][17][18][19]. We sum up these bounds together with our results in Fig.…”

“…Future experimental boundaries coming from CMB (grey), Lyman-α forest detection (red), Square Kilometre Array (brown) and Pulsar Timing Arrays (orange) are identified with solid lines. The reported experimental bounds were adapted from the recent review on ultralight bosonic dark matter [19]. We refer the reader to that text and to the references therein for more details and extended bibliography.…”

“…Recent studies put severe constraints on the vanilla FDM model without self-interactions where the usual cosine axionic potential is approximated as 1 − cos(φ/f ) ∼ φ 2 2f 2 . Various analyses of Lyman-α forest, satellite galaxies formation, the Milky Way core and Black Hole superradiance leave as the only viable mass window m φ O(1) × 10 −21 eV [11][12][13][14][15][16][17][18][19] and constrain the abundance of FDM candidates at different mass scales. These experimental bounds imply that FDM cannot solve the alleged small-scale problems affecting ΛCDM as the Jeans mass (representing the lower bound on DM halos mass production) rapidly decreases at increasing ultralight boson masses [17].…”

Frequency shift of light emitted from growing and shrinking black holes

“…Among the astrophysical motivations to carry on the analysis in this paper and potential applications of the method, we have the case of ultralight bosonic dark matter, where our method could be useful to set predictions or limitations to this dark matter model through the effects on accretion onto supermassive black holes (e.g. [7][8][9][10]). Another possibility is to extend the analysis and estimate the variability in slow processes like Hawking radiation (see e.g.…”

Rotating Scalar Field and Formation of Bose Stars

“…One can find the lower bound on boson mass to be > 1.5 × 10 −33 eV by requiring clustering between bosons within the cosmological horizon for presentday [12]. As the dark matter is gravitationally coupled to baryonic matter, its mass can be constrained to > 1.6 × 10 −28 eV by baryon acoustic oscillations at matter-radiation equality [12]. The lower bounds on the mass of the bosonic dark matter can be found in Refs.…”