The Carnegie Institution of Washington (the organization's legal name), known also for public purposes as the Carnegie Institution for Science (CIS), is an organization in the United States established to fund and perform scientific research. The institution is headquartered in Washington, D.C.As of June 30, 2020[update], the Institution's endowment was valued at $926.9 million. In 2018 the expenses for scientific programs and administration were $96.6 million. As of June 22, 2022[update], Eric Isaacs is president of the institution.....C.C.C.C.C..
We investigate the evolution of density perturbations in dark matter, including the new combined effects of finite number density and non-zero velocity dispersion. Using a truncated BBGKY hierarchy, we derive analytical expressions for the dark matter power spectrum during radiation and matter domination. A component of warm white noise emerges in our analysis, which arises due to the finite number density and undergoes scale-dependent evolution because of the velocity dispersion. Although free streaming erases adiabatic initial perturbations on small scales, warm white noise persists below the free-streaming length and grows during matter domination, with growth suppressed below the dark matter Jeans length. Our calculated power spectra agree with N-body simulations in the linear regime and accurately predict halo mass functions in the nonlinear regime. Effects of warm white noise can emerge on observable quasi-linear scales for ultralight dark matter produced after inflation with a subhorizon correlation length. Our formalism is applicable to these scenarios (with de Broglie-scale quasi-particles), to cases in which dark matter includes macroscopic structures (such as primordial black holes), and to traditional warm and cold dark matter scenarios.
Galaxies at Cosmic Noon ( z ∼ 2–3) are characterized by rapid star formation that will lead to significant metal enrichment in the interstellar medium (ISM). While much observational evidence suggests that these galaxies are chemically distinct from those in the local Universe, directly measuring the ISM chemistry in large samples of high- z galaxies is only now possible with the observational capabilities of JWST. In this first key paper of the CECILIA program, we present the direct-method physical conditions and multielement abundances in 20 galaxies at Cosmic Noon. Using a combination of archival Keck/MOSFIRE and new ∼30 hr NIRSpec spectroscopy, we measure multiple electron gas densities and the temperature structure from the O ^+ and S ^2+ ions. We find that n _e [O ii ] and n _e [S ii ] are comparable but elevated with respect to n _e in local star-forming galaxies, and the simultaneous T _e [O ii ] and T _e [S iii ] generally agree with photoionization model T _e scaling relations. The O abundances in the CECILIA galaxies range from 12 + log(O/H) = 7.76 to 8.81 (12%–131% solar O/H), representing some of the highest direct-method metallicities and lowest T _e ( T _e [O ii ] ≈ 6500 K) measured with JWST to date. The CECILIA galaxies exhibit significantly subsolar S/O and Ar/O, a signature of predominant enrichment from core-collapse supernovae. The N/O–O/H trends in the CECILIA galaxies generally agree with the abundance trends in local nebulae, but the large scatter in N/O could be sensitive to the star formation history. The CECILIA observations demonstrate that exceptionally deep JWST spectroscopy can unveil the multielement ISM abundance patterns in typical high- z galaxies.
Velocity dispersion ( σ ) in stellar streams from globular clusters (GCs) is sensitive to heating by Galactic substructure, including dark matter (DM) subhalos. Recent studies have compared σ in observed and modeled streams to probe DM properties, but have relied on stream models that neglect strong encounters, black holes (BHs), and mass segregation in GCs. Such phenomena may inflate stream σ or introduce selection effects—e.g., a σ that depends on star mass ( m ). We investigate this prospect using Monte Carlo N -body simulations of GCs under static Galactic tides to generate mock streams with realistic mass and velocity distributions. We find σ correlates with m , especially after core collapse (the GC’s observable increase in central density upon ejecting its BHs), rising from 1.2 to 2.2 km s ^−1 between m = 0.3–0.8 M _⊙ , with typical kinematic cuts on stream membership. Similar in magnitude to heating by Galactic substructure, this enhancement occurs because the GC’s loss of BHs allows its most-massive stars to occupy its dense center, raising their likelihood of strong ejection via binary interactions and adding broad, exponential wings to the stream’s velocity distribution. Streams’ kinematics thus probe properties (density, BH retention) of their progenitor GCs. Our results also imply observations of streams from some GCs, especially those not subject to highly episodic mass loss, may select for higher σ than predicted by models neglecting σ ’s m dependence. This would cause observed σ in streams—already on the low side of expectations for cold DM—to further favor alternatives such as warm or ultralight DM.
We present optical and near-infrared (NIR) spectroscopic observations of the nearby Type II supernova SN 2024ggi ranging from 250 to 581 days after the explosion. Comparing the evolution of the [O i] at 6300, 6363 & Aring; doublet normalized to the continuum with spectral models from the literature, we estimate a progenitor star zero-age main-sequence mass (M-ZAMS) of approximate to 14 M-circle dot. This value is consistent with M-ZAMS reported in the literature from independent methodologies. The nebular spectra are used to study the structure of the inner ejecta. The broad H alpha line has a full width at half-maximum of similar or equal to 3900 km s(-1), with small deviations from a symmetric Gaussian profile centred at zero velocity that persist until the penultimate spectrum obtained 459 days after explosion, and the [O i] doublet is blueshifted by approximate to-940 km s(-1). In the NIR, the nebular spectra reveal double-peaked emission features of [Mg i] and [Fe ii] lines between +250 and +319 days, suggesting a bipolar distribution of intermediate-mass and iron-peak elements in the line of sight. Such a double-peaked feature in these NIR lines has not been previously reported. No corresponding asymmetries are observed in the hydrogen lines, indicating that the asymmetry is confined to intermediate-mass and iron-peak elements in the innermost ejecta. Additionally, we detect first-overtone carbon monoxide emission at 2.3 mu m between 250 and 319 days and a blueshift in the emission lines of H alpha, [O i], [Mg i], and [Fe ii] first observed in the +581 days optical spectrum, consistent with dust formation in the ejecta.
We present a general analytic framework for the evolution of cosmic structure in multi-species dark matter models that simultaneously incorporates finite velocity dispersion and Poisson fluctuations. Our approach accommodates arbitrary numbers of dark matter components with distinct mass fractions, velocity distributions, and number densities — ranging from cold particles to warm species and sparse populations such as primordial black holes or solitons. The framework is based on solving a truncated BBGKY hierarchy, whose solution is obtained by solving Volterra integral equations. We provide an efficient algorithm to solve for the total, as well as inter- and intra-species power spectra. Worked examples with two-component mixtures illustrate how isocurvature (initially Poisson) and adiabatic spectra evolve differently depending on the properties of the warm or sparse fraction. This evolution is controlled by the free-streaming and Jeans scales, and the results match analytic estimates and N-body simulations.
