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NASA NTRS1994

Some considerations on velocity vector accuracy in dust trajectory analysis

The relative contributions of comets and asteroids to the reservoir of dust in the interplanetary medium is not known. There are direct observations of dust released from comets and there is evidence to associate the IRAS dust bands with possible collisions of asteroids in the main belt. A means towards sorting out the parent sources has been proposed in the establishment of a dust collector in orbit about the Earth. The purpose of such a facility would be to collect not only cosmic dust particles intact but also the state vectors, as they arrive at the detector, the idea being that one may combine analytical laboratory analysis of the physics and chemistry of the captured particles with orbital data in order to help distinguish between bodies and identify parent bodies. The theoretical study of dust particle orbits in the solar system takes on greatly more importance if we use collected trajectory data. The orbital motion of dust when radiation and forces alone are acting is well understood. When gravitational forces due to the planets are included, the motion can become quite complex. In order to characterize the orbits of particles as they crossed the Earth's orbits, a study of the long-time dust orbital evolution was undertaken. We have considered various parameters associated with these dust orbits to see if one may in a general way discriminate between particles evolved from comets and asteroids. We proceed in this study as we have done previously. That is, we considered the dust particles as ideal black bodies, of density 1 gm/cc, spherical, with radii 10-100 microns. Particles of this size are affected by radiation forces, photon pressure, and Poynting-Robertson drag. Account was also taken of solar wind drag, which amounts to about 30 percent of the Poynting-Robertson drag negligible. The gravitational forces due to the planets are included, unlike in our previous study; the planetary orbits are those of true n-body interaction so that the possibility of secular resonance is included. Our method was to calculate explicitly by a numerical procedure the orbits of dust particles after they left their parent bodies. The motion is determined numerically with the implicit Runge-Kutta integrator using Gauss-Radau spacings.

Jackson, A. A.↗

NASA NTRS2019

Search for Eccentric Binary Black Hole Mergers with Advanced LIGO and Advanced Virgo during Their First and Second Observing Runs

When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits (e > 0.1 at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template-based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates ≳100 Gpc−3 yr−1 for e > 0.1, assuming a black hole mass spectrum with a power-law index ≲2.

B. P. Abbott↗

DOE OSTI2021

Faint galaxies and small halos : probes of galaxy formation and dark matter

This thesis addresses the intersection of dark matter and galaxy formation physics by modeling the faintest galaxies in the Universe in a cosmological context. In the first part of this work, I present an empirical model for the connection between faint galaxies and small dark matter halos. Combining this model with tailored cosmological simulations of Milky Way analogs and state-of-the-art satellite galaxy observations yields new insights into dwarf galaxy formation and hierarchical structure formation. Next, I show that these same dwarf galaxy observations place stringent constraints on microphysical dark matter properties including its warmth, self-interactions, Standard Model interactions, minimum particle mass, and formation epoch. Finally, I describe a unified framework that combines dark matter constraints from dwarf galaxies and strong gravitational lensing, paving the way for next-generation surveys of small-scale cosmic structure to deliver unprecedented insights into dark matter physics.

Nadler, Ethan Oliver↗

DOE OSTI2023

Revealing the strength of three-nucleon interactions with the proposed Einstein Telescope

Nuclear systems, ranging from atomic nuclei to dense matter probed in neutron stars, are governed by strong interactions. Three-nucleon forces have been found to be a crucial ingredient for the reliable description of these systems. Here, in this work, we explore how astrophysical data on neutron stars and their mergers from current and next-generation observatories will enable us to distinguish nuclear Hamiltonians. In particular, we investigate two different nuclear Hamiltonians that have been adjusted to reproduce two-nucleon scattering data and properties of light nuclei, but differ in the three-nucleon interactions among neutrons. We find that no significant constraints can be obtained from current data, but that the proposed Einstein Telescope could provide strong evidence to distinguish among these Hamiltonians.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2019

Gravitational wave opacity from gauge field dark energy

We show that astrophysical gravitational waves can undergo an anomalous modulation when propagating through cosmic gauge field dark energy. A sufficiently strong effect, dependent on the gauge field energy density, would appear as a redshift-dependent opacity, thereby impacting the use of gravitational wave standard sirens to constrain the expansion history of the Universe. Here, we investigate a particular model of cosmic gauge field dark energy and show that at early times it behaves like dark radiation, whereas a novel interaction causes it to drive cosmic acceleration at late times. Joint constraints on the cosmological scenario due to type 1a supernovae, baryon acoustic oscillations, and cosmic microwave background data are presented. In view of these constraints, we show that standard siren luminosity distances in the redshift range 0.5 ≲ z ≲ 1.5 would systematically dim by up to 1%, which may be distinguishable by third-generation gravitational wave detectors.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

A comparative study of hyperon equations of state in supernova simulations

A comparative study of the Λ hyperon equations of state of Banik, Hempel and Banyopadhyay (BHB), Banik et al., and Shen et al. (denoted as HShen Λ) for core-collapse supernova (CCSN) simulations is carried out in this work. The dynamical evolution of a protoneutron star (PNS) into a black hole is investigated in CCSN simulations in the general relativistic one-dimensional code using the BHBΛϕ and HShen Λ equation of state (EOS) tables and different progenitor models from Woosley and Heger. Radial profiles of the mass fractions of baryons, the density, as well as the temperature in the PNS at different moments in time, are compared for both EOS tables. The behavior of the central density of the PNS with time is demonstrated for these two Λ hyperon EOS tables and compared with their corresponding nuclear EOS tables. It is observed that the black hole formation time is higher in the BHBΛϕ case than in the HShen Λ EOS case for the entire set of progenitor models adopted here, because the repulsive Λ–Λ interaction makes the BHBΛϕ EOS stiffer. Neutrino emission with the Λ hyperon EOS ceases earlier than that of its nuclear counterpart. The long-duration evolution of the shock radius and the gravitational mass of the PNS after a successful supernova explosion with enhanced neutrino heating are studied with the BHBΛϕ EOS and s20WH07 progenitor model. The PNS is found to remain stable for 4 s and might evolve into a cold neutron star.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

TRANSIENT CHAOS AND FRACTAL STRUCTURES IN PLANETARY FEEDING ZONES

The circular restricted three-body problem is investigated in the context of accretion and scattering processes. In our model, a large number of identical non-interacting mass-less planetesimals are considered in the planar case orbiting a star-planet system. This description allows us to investigate the gravitational scattering and possible capture of the particles by the forming planetary embryo in a dynamical systems approach. Although the problem serves a large variety of complex motions, the results can be easily interpreted because of the low dimensionality of the phase space. We show that initial conditions define isolated regions of the disk, where planetesimals accrete or escape, which have, in fact, a fractal structure. The fractal geometry of these ''basins'' implies that the dynamics is very complex. Based on the calculated escape rates and escape times, it is also demonstrated that the planetary accretion rate is exponential for short times and follows a power law for longer integration. A new numerical calculation of the maximum mass that a planet can reach (described by the expression of the isolation mass) is also derived.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

Primordial Black Holes from Long-Range Scalar Forces and Scalar Radiative Cooling

We describe a new scenario for the formation of primordial black holes (PBHs). In the early Universe, the long-range forces mediated by the scalar fields can lead to formation of halos of heavy particles even during the radiation-dominated era. The same interactions result in the emission of scalar radiation from the motion and close encounters of particles in such halos. Radiative cooling due the scalar radiation allows the halos to collapse to black holes. We illustrate this scenario on a simple model with fermions interacting via the Yukawa forces. The abundance and the mass function of PBHs are suitable to account for all dark matter, or for some gravitational wave events detected by LIGO. The model relates the mass of the dark-sector particles to the masses and abundance of dark matter PBHs in a way that can explain why the dark matter and the ordinary matter have similar mass densities. The model also predicts a small contribution to the number of effective light degrees of freedom, which can help reconcile different measurements of the Hubble constant.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2019

The Enigmatic (Almost) Dark Galaxy Coma P: Distance Measurement and Stellar Populations from HST Imaging

We present Hubble Space Telescope (HST) observations of the low surface brightness (SB) galaxy Coma P. This system was first discovered in the Arecibo Legacy Fast ALFA H i survey and was cataloged as an (almost) dark galaxy because it did not exhibit any obvious optical counterpart in the available survey data (e.g., Sloan Digital Sky Survey). Subsequent WIYN pODI imaging revealed an ultra-low SB stellar component located at the center of the H i detection. We use the HST images to produce a deep color–magnitude diagram of the resolved stellar population present in Coma P. We clearly detect a red stellar sequence that we interpret to be a red giant branch and use it to infer a tip of the red giant branch distance of 5.50{sub −0.53}{sup +0.28} Mpc. The new distance is substantially lower than earlier estimates and shows that Coma P is an extreme dwarf galaxy. Our derived stellar mass is only 4.3 × 10{sup 5} M {sub ⊙}, meaning that Coma P has an extreme H i-to-stellar mass ratio of 81. We present a detailed analysis of the galaxy environment within which Coma P resides. We hypothesize that Coma P formed within a local void and has spent most of its lifetime in a low-density environment. Over time, the gravitational attraction of the galaxies located in the void wall has moved it to the edge, where it had a recent “fly-by” interaction with M64. We investigate the possibility that Coma P is at a farther distance and conclude that the available data are best fit by a distance of 5.5 Mpc.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

Multi-fluid Modeling of Magnetosonic Wave Propagation in the Solar Chromosphere: Effects of Impact Ionization and Radiative Recombination

In order to study chromospheric magnetosonic wave propagation including, for the first time, the effects of ion–neutral interactions in the partially ionized solar chromosphere, we have developed a new multi-fluid computational model accounting for ionization and recombination reactions in gravitationally stratified magnetized collisional media. The two-fluid model used in our 2D numerical simulations treats neutrals as a separate fluid and considers charged species (electrons and ions) within the resistive MHD approach with Coulomb collisions and anisotropic heat flux determined by Braginskiis transport coefficients. The electromagnetic fields are evolved according to the full Maxwell equations and the solenoidality of the magnetic field is enforced with a hyperbolic divergence-cleaning scheme. The initial density and temperature profiles are similar to VAL III chromospheric model in which dynamical, thermal, and chemical equilibrium are considered to ensure comparison to existing MHD models and avoid artificial numerical heating. In this initial setup we include simple homogeneous flux tube magnetic field configuration and an external photospheric velocity driver to simulate the propagation of MHD waves in the partially ionized reactive chromosphere. In particular, we investigate the loss of chemical equilibrium and the plasma heating related to the steepening of fast magnetosonic wave fronts in the gravitationally stratified medium.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1973

Comets and the formation of planets

Morphological study of the physical and dynamical processes of planet formation, with emphasis on the role of comet nuclei. A consistent model proposes the formation of comets and planets in preplanetary rings of the residual solar nebula, with subsequent ejection, chiefly by Jupiter, of the comets to Oort's (1950) sphere. Physically, dynamically, or statistically evaluated items include: (1) the total number and mass of comets in Oort's cloud; (2) reevaluation of the diameters and masses of comet nuclei; (3) the processes of nucleation from gravitational and 'Boltzmann' instabilities of gaseous media to agglomerations of particulate matter; and (4) the statistical-dynamical conditions and time scales of orbital interaction of comets with the planets and the consequences of disintegration.

Opik, E. J.↗

NASA NTRS1996

Kuiper Belt Dust Grains as a Source of Interplanetary Dust Particles

The recent discovery of the so-called Kuiper belt objects has prompted the idea that these objects produce dust grains that may contribute significantly to the interplanetary dust population. In this paper, the orbital evolution of dust grains, of diameters 1 to 9 microns, that originate in the region of the Kuiper belt is studied by means of direct numerical integration. Gravitational forces of the Sun and planets, solar radiation pressure, as well as Poynting-Robertson drag and solar wind drag are included. The interactions between charged dust grains and solar magnetic field are not considered in the model. Because of the effects of drag forces, small dust grains will spiral toward the Sun once they are released from their large parent bodies. This motion leads dust grains to pass by planets as well as encounter numerous mean motion resonances associated with planets. Our results show that about 80% of the Kuiper belt grains are ejected from the Solar System by the giant planets, while the remaining 20% of the grains evolve all the way to the Sun. Surprisingly, the latter dust grains have small orbital eccentricities and inclinations when they cross the orbit of the Earth. This makes them behave more like asteroidal than cometary-type dust particles. This also enhances their chances of being captured by the Earth and makes them a possible source of the collected interplanetary dust particles; in particular, they represent a possible source that brings primitive/organic materials from the outer Solar System to the Earth. When collisions with interstellar dust grains are considered, however, Kuiper belt dust grains around 9 microns appear likely to be collisionally shattered before they can evolve toward the inner part of the Solar System. The collision destruction can be applied to Kuiper belt grains up to about 50 microns. Therefore, Kuiper belt dust grains within this range may not be a significant part of the interplanetary dust complex in the inner Solar System.

Liou, Jer-Chyi↗

NASA NTRS1993

Cytoskeleton-amyloplast interactions in sweet clover

The distribution of organelles within columella cells of sweet clover was examined by transmission electron microscopy following growth under static or clinorotating conditions. A developmentally conditioned polarity was observed, with a proximal location of the nucleus and a distal accumulation of the endoplasmic reticulum. This polarity was insensitive to clinorotation. In contrast, clinorotation altered the location of amyloplasts. Application of cytoskeletal poisons (colchicine, cytochalasin D, taxol, and phalloidin), especially during clinorotation, had interesting effects on the maintenance of columella cell polarity, with a profound effect on the extent, location, and structure of the endoplasmic reticulum. The site of cytoskeletal interactions with sedimenting amyloplasts is thought to be the amyloplast envelope. An envelope fraction, having over 17 polypeptides, was isolated using immobilized antibody technology, and will provide a means of assessing the role of specific peptides in cytoskeleton/amyloplast interactions.

Non-NASA Center↗

DOE OSTI2022

Gravitational wave modes in matter

Here, a general linear gauge-invariant equation for dispersive gravitational waves (GWs) propagating in matter is derived. This equation describes, on the same footing, both the usual tensor modes and the gravitational modes strongly coupled with matter. It is shown that the effect of matter on the former is comparable to diffraction and therefore negligible within the geometrical-optics approximation. However, this approximation is applicable to modes strongly coupled with matter due to their large refractive index. GWs in ideal gas are studied using the kinetic average-Lagrangian approach and the gravitational polarizability of matter that we have introduced earlier. In particular, we show that this formulation subsumes the kinetic Jeans instability as a collective GW mode with a peculiar polarization, which is derived from the dispersion matrix rather than assumed a priori. This forms a foundation for systematically extending GW theory to GW interactions with plasmas, where symmetry considerations alone are insufficient to predict the wave polarization.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2001

An active role of the amyloplasts and nuclei of root statocytes in graviperception

Three main phases are discerned in the gravitropic reaction: perception of a gravitational stimulus, its transduction, and fixation of the reaction resulting in bending of an organ. According to the starch-statolith hypothesis of Nemec and Haberlandt, amyloplasts in the structurally and functionally specialized graviperceptive cells (statocytes) sediment in the direction of a gravitational vector in the distal part of a cell while a nucleus is in the proximal one. If amyloplasts appear to act as gravity sensors, the receptors, which interact with sedimented amyloplasts, and next signaling are still unclear. An analysis of the structural-functional organization of cells in different root cap layers of such higher plants as pea, Arabidopsis thaliana, and Brassica rapa grown under 1 g, on the clinostats, and in microgravity, allows us to support the hypothesis that amyloplasts function as statoliths in statocytes, but they may not be only the passive statolithic mass. We propose that amyloplasts fulfill a more complex function by interacting with a receptor, which is a nucleus, in transduction of some signal to it. Gravity-induced statolith movement in certain order leads to a new functional connection between gravity susceptors--amyloplasts and a receptor--a nucleus receiving some signal presumedly of a mechanical or biochemical nature from the amyloplasts. During gravitropism, sugar signaling could induce expression of genes encoding auxin transport proteins in a nucleus giving the nucleus an intermediate role in signal trunsduction following perception. c 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

short duration↗

DOE OSTI2025

JWST’s PEARLS: A z ≃ 6 quasar in a train-wreck galaxy merger system

We present JWST NIRSpec integral field spectroscopy observations of the z = 5.89 quasar NDWFS J1425+3254 from 0.6–5.3 μm, covering the rest-frame ultraviolet and optical at a spectral resolution of R ∼ 100. The quasar has a black hole mass of M BH = (1.4 +3.1 −1.0 ) × 10 9 M ⊙ and an Eddington ratio of L Bol /L Edd = 0.3 +0.6 −0.2 , as implied from the broad Balmer Hα and Hβ lines. The quasar host has significant ongoing obscured star formation, as well as a quasar-driven outflow with velocity 6050 +460 −630 km s −1 and ionised outflow rate of 1650 +130 −1230 M ⊙ yr −1 . This is possibly one of the most extreme outflows in the early Universe. The data also reveal that two companion galaxies are merging with the quasar host. The north-eastern companion galaxy is relatively old and very massive, with a luminosity-weighted stellar age of 65 +9 −4 Myr, stellar mass of (3.6 +0.6 −0.3 #x00D7; 10 11 M ⊙ , and star-formation rate (SFR) of ∼15–30 M ⊙ yr −1 . A bridge of gas connects this companion galaxy and the host, confirming their ongoing interaction. A second merger is occurring between the quasar host and a much younger companion galaxy to the south, with a stellar age of 6.7 ± 1.8 Myr, stellar mass of (1.9 ± 0.4)×10 10 M ⊙ , and SFR of ∼40–65 M ⊙ yr −1 . There is also another galaxy in the field, likely in the foreground at z = 1.135, which could be gravitationally lensing the quasar with a magnification of 1 < μ < 2 and, thus, < 0.75 mag. Overall, the system is a ‘train-wreck’ merger of three galaxies, with star formation and extreme quasar activity that were likely triggered by these ongoing interactions.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Early excitation of spin-orbit misalignments in close-in planetary systems

Continued observational characterization of transiting planets that reside in close proximity to their host stars has shown that a substantial fraction of such objects possess orbits that are inclined with respect to the spin axes of their stars. Mounting evidence for the wide-spread nature of this phenomenon has challenged the conventional notion that large-scale orbital transport occurs during the early epochs of planet formation and is accomplished via planet-disk interactions. However, recent work has shown that the excitation of spin-orbit misalignment between protoplanetary nebulae and their host stars can naturally arise from gravitational perturbations in multi-stellar systems as well as magnetic disk-star coupling. In this work, we examine these processes in tandem. We begin with a thorough exploration of the gravitationally facilitated acquisition of spin-orbit misalignment and analytically show that the entire possible range of misalignments can be trivially reproduced. Moreover, we demonstrate that the observable spin-orbit misalignment only depends on the primordial disk-binary orbit inclination. Subsequently, we augment our treatment by accounting for magnetic torques and show that more exotic dynamical evolution is possible, provided favorable conditions for magnetic tilting. Cumulatively, our results suggest that observed spin-orbit misalignments are fully consistent with disk-driven migration as a dominant mechanism for the origin of close-in planets.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Machine Learning for DUNE Supernova Trigger

One of the major scientific goals of the Deep Underground Neutrino Experiment (DUNE) is to detect and measure the neutrino flux from galactic core-collapse supernovae. These neutrinos, which exist in the low energy range of up to a few tens of MeV and are responsible for carrying away over 99% of the gravitational binding energy of the supernova, provide an opportunity to study the end of life evolution of massive stars, as well as unique properties and interactions of neutrinos. Because galactic supernovae are expected to occur only on the timespan of every few decades, it is crucial that DUNE is able to detect supernova neutrino interactions when they occur. However, detecting these supernova interactions requires sifting through a large amount of data, and DUNE detectors require a trigger to signal when supernova neutrino events occur. Machine learning provides a potential approach to creating this trigger. This project generates ADC and ground truth images of neutrino interactions in a LArTPC detector as simulated by the Model of Argon Reaction Low Energy Yields (MARLEY) to be used for machine learning. The eventual goal of this work is to facilitate DUNE s detection of supernova neutrino interactions by building a machine learning pipeline that will train the trigger algorithm.

Damish, Stephanie↗