scholarly journals Galactic 26Al traces metal loss through hot chimneys

2020 ◽  
Vol 501 (1) ◽  
pp. 210-218
Author(s):  
Martin G H Krause ◽  
Donna Rodgers-Lee ◽  
James E Dale ◽  
Roland Diehl ◽  
Chiaki Kobayashi
Keyword(s):  
Galaxy Evolution ◽  
Massive Star ◽  
Milky Way ◽  
Gamma Ray ◽  
Branching Ratio ◽  
Metal Loss ◽  
Global Flow ◽  
Model Galaxy ◽  
Simulation Results ◽  
Supernova Feedback

ABSTRACT Radioactive 26Al is an excellent tracer for metal ejection in the Milky Way, and can provide a direct constraint on the modelling of supernova feedback in galaxy evolution. Gamma-ray observations of the 26Al decay line have found high velocities and hence require a significant fraction of the Galactic 26Al in the hot component. At the same time, meteoritic data combined with simulation results suggest that a significant amount of 26Al makes its way into stars before decay. We investigated the distribution into hot and cold channels with a simulation of a Milky-Way-like galaxy with massive-star feedback in superbubbles and with ejecta traced by 26Al. About 30–40 per cent of the ejecta remain hot, with typical cooling times of the order Gyr. 26Al traces the footpoints of a chimney-fed outflow that mixes metals turbulently into the halo of the model galaxy on a scale of at least 50 kpc. The rest diffuses into cold gas ≲ 104 K, and may therefore be quickly available for star formation. We discuss the robustness of the result by comparison to a simulation with a different global flow pattern. The branching ratio into hot and cold components is comparable to that of longer term average results from chemical evolution modelling of galaxies, clusters, and the intracluster medium.

scholarly journals Initial Model Catalogue for Galaxy Evolution

2004 ◽  
Vol 21 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Naohito Nakasato
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Milky Way ◽  
High Redshift ◽  
Random Number Generator ◽  
Star Formation History ◽  
Initial Model ◽  
Model Galaxy ◽  
Formation History ◽  
Type Ia

AbstractWe have computed full hydrochemodynamical evolution for 150 initial models of protogalaxies with our chemodynamical SPH code named GENSO. Various parameters for all models are identical except for a seed for a random number generator. In other words, all models have similar global properties but have the different merging history that leads to a different evolution in each model. Results of the series of computations have two main applications. Firstly, we have an initial model catalogue for subsequent modelling of galaxy evolution. Since the resulting evolution depends strongly on the initial phase of the particle distribution, it is crucial to find a suitable initial model when we model a specific real galaxy in the Universe, notably the Milky Way in our case. We will make a precise chemical and dynamical model of the Milky Way out of 150 models in our initial model catalogue. Secondly, we can obtain a large variety of global histories of physical values such as star formation, metallicity in the ISM and stellar components, and Type II and Ia supernova rates. For example, the resulting total star formation history shows the peak at a high redshift z ∼ 6 and the peak value is ∼280 M⊙ yr–1 Mpc–3. Also, the Type Ia rate obtained has a peak at z ∼ 3.5. All of our results and model catalogue are publicly available from our website for those who wish to model galaxy evolution.

scholarly journals Comparing simulated 26Al maps to gamma-ray measurements

2019 ◽  
Vol 632 ◽  
pp. A73 ◽  
Author(s):  
Moritz M. M. Pleintinger ◽  
Thomas Siegert ◽  
Roland Diehl ◽  
Yusuke Fujimoto ◽  
Jochen Greiner ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Massive Star ◽  
Milky Way ◽  
Gamma Ray ◽  
Scale Height ◽  
Morphological Properties ◽  
Small Scale ◽  
Height Distribution ◽  
Hydrodynamic Simulation ◽  
Hydrodynamic Simulations

Context. The diffuse gamma-ray emission of 26Al at 1.8 MeV reflects ongoing nucleosynthesis in the Milky Way and traces massive-star feedback in the interstellar medium due to its 1 Myr radioactive lifetime. The morphology and dynamics of the interstellar medium are investigated in astrophysics through 3D hydrodynamic simulations in fine detail as there are few suitable astronomical probes available. Aims. We aim to compare a galactic-scale hydrodynamic simulation of the Galaxy’s interstellar medium, including feedback and nucleosynthesis, with gamma-ray data on 26Al emission in the Milky Way, extracting constraints that are only weakly dependent on the particular realisation of the simulation or Galaxy structure. Methods. Due to constraints and biases in both the simulations and the gamma-ray observations, such comparisons are not straightforward. For a direct comparison, we performed maximum likelihood fits of both simulated sky maps and observation-based maximum entropy maps to measurements using INTEGRAL/SPI. In order to study general morphological properties, we compare the scale heights of 26Al emission produced by the simulation to INTEGRAL/SPI measurements. Results. The direct comparison shows that the simulation describes the observed inner Galaxy well, however it differs significantly from the observed full-sky emission morphology. Comparing the scale height distribution, we see similarities for small-scale height features and a mismatch at larger-scale heights. We attribute this to prominent foreground emission sites which are not captured by the simulation.

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

scholarly journals The characterization of the gamma-ray signal from the central Milky Way: A case for annihilating dark matter

2016 ◽  
Vol 12 ◽  
pp. 1-23 ◽  
Author(s):  
Tansu Daylan ◽  
Douglas P. Finkbeiner ◽  
Dan Hooper ◽  
Tim Linden ◽  
Stephen K.N. Portillo ◽  
...  
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Gamma Ray

scholarly journals LIGHT SUPERCONDUCTING STRINGS IN THE GALAXY

2007 ◽  
Vol 16 (12b) ◽  
pp. 2399-2405 ◽  
Author(s):  
FRANCESC FERRER ◽  
TANMAY VACHASPATI
Keyword(s):  
Magnetic Field ◽  
Spatial Distribution ◽  
Particle Physics ◽  
Milky Way ◽  
Gamma Ray ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Magnetic Field ◽  
The Galaxy ◽  
Intense Source

Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed the presence of a strong 511 keV gamma ray line emission from the bulge, which requires an intense source of positrons in the galactic center. These observations are hard to account for by conventional astrophysical scenarios, whereas other proposals, such as light DM, face stringent constraints from the diffuse gamma ray background. Here we suggest that light superconducting strings could be the source of the observed 511 keV emission. The associated particle physics, at the ~ 1 TeV scale, is within the reach of planned accelerator experiments, while the distinguishing spatial distribution, proportional to the galactic magnetic field, could be mapped by SPI or by future, more sensitive satellite missions.

scholarly journals On the delay times of merging double neutron stars

2020 ◽  
Vol 500 (2) ◽  
pp. 1755-1771
Author(s):  
Laura Greggio ◽  
Paolo Simonetti ◽  
Francesca Matteucci
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Milky Way ◽  
Gamma Ray ◽  
Chemical Properties ◽  
Redshift Distribution ◽  
Strong Constraint ◽  
Delay Times ◽  
Best Fitting ◽  
Short Grbs

ABSTRACT The merging rate of double neutron stars (DNS) has a great impact on many astrophysical issues, including the interpretation of gravitational waves signals, of the short gamma-ray bursts (GRBs), and of the chemical properties of stars in galaxies. Such rate depends on the distribution of the delay times (DDT) of the merging events. In this paper, we derive a theoretical DDT of merging DNS following from the characteristics of the clock controlling their evolution. We show that the shape of the DDT is governed by a few key parameters, primarily the lower limit and the slope of the distribution of the separation of the DNS systems at birth. With a parametric approach, we investigate on the observational constraints on the DDT from the cosmic rate of short GRBs and the europium-to-iron ratio in Milky Way stars, taken as tracer of the products of the explosion. We find that the local rate of DNS merging requires that $\sim \! 1 {{\ \rm per\ cent}}$ of neutron stars progenitors live in binary systems which end their evolution as merging DNS within a Hubble time. The redshift distribution of short GRBs does not yet provide a strong constraint on the shape of the DDT, although the best-fitting models have a shallow DDT. The chemical pattern in Milky Way stars requires an additional source of europium besides the products from merging DNS, which weakens the related requirement on the DDT. At present both constraints can be matched with the same DDT for merging DNS.

scholarly journals Analysis of the very inner Milky Way dark matter distribution and gamma-ray signals

2016 ◽  
Vol 94 (12) ◽  
Author(s):  
V. Gammaldi ◽  
V. Avila-Reese ◽  
O. Valenzuela ◽  
A. X. Gonzalez-Morales
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Gamma Ray ◽  
Matter Distribution ◽  
Dark Matter Distribution

scholarly journals Observation of triggering in the Milky Way

2006 ◽  
Vol 2 (S237) ◽  
pp. 212-216 ◽  
Author(s):  
L. Deharveng ◽  
A. Zavagno ◽  
B. Lefloch ◽  
J. Caplan ◽  
M. Pomarès
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Milky Way ◽  
Turbulent Medium ◽  
Massive Star Formation ◽  
Collapse Process

AbstractWe show how the expansion of classical Galactic Hiiregions can trigger massive-star formation via the collect & collapse process. We give examples of this process at work. We suggest that it also works in a turbulent medium.

Study of a single line of sight gamma ray diagnostics for measurements of the absolute gamma ray emission from JET

2021 ◽  
Vol 16 (12) ◽  
pp. C12019
Author(s):  
G. Marcer ◽  
M. Nocente ◽  
L. Giacomelli ◽  
G. Gorini ◽  
E. Perelli Cippo ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Neutron Emission ◽  
Fusion Reaction ◽  
Branching Ratio ◽  
Plasma Source ◽  
Line Of Sight ◽  
Extended Plasma ◽  
Absolute Efficiency ◽  
The Absolute ◽  
Gamma Ray Emission

Abstract The fusion power produced in a DT thermonuclear reactor is currently determined by measuring the absolute 14 MeV neutron yield of the D(T, α)n fusion reaction. Measurements of 17 MeV gamma rays born from the much less probable D(T, 5He)γ reaction (branching ratio of ∼10−5) have been proposed as an alternative independent method to validate the neutron counting method and also to fulfill the requests of the nuclear regulator for licensing ITER DT operations. However, the development of absolute 17 MeV gamma ray emission measurements entails a number of requirements, such as: (i) knowledge of the 17 MeV gamma ray to 14 MeV neutron emission branching ratio; (ii) the simulation of the gamma ray transport from the extended plasma source to the gamma ray detectors; (iii) a careful determination of the absolute efficiency of previously calibrated gamma ray spectrometers. In this work, we have studied the possibility to infer the global gamma ray emission rate from measurements made with a 3″ × 6″ LaBr3 spectrometer installed at the end of a collimated tangential line of sight at the JET tokamak and using the neutron emission from deuterium plasmas of the most recent experimental campaigns. Results show that 17 MeV gamma ray fluxes at the end of this tangential line of sight have a weak dependence (less than 5%) on the plasma profile and can therefore be used to infer the total emission from the plasma.

scholarly journals Neutron-capture elements in dwarf galaxies

2020 ◽  
Vol 634 ◽  
pp. A84 ◽  
Author(s):  
Á. Skúladóttir ◽  
C. J. Hansen ◽  
A. Choplin ◽  
S. Salvadori ◽  
M. Hampel ◽  
...  
Keyword(s):  
Massive Star ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Chemical Enrichment ◽  
Theoretical Predictions ◽  
Low Metallicity ◽  
First Time ◽  
Best Fit

The slow (s) and intermediate (i) neutron (n) capture processes occur both in asymptotic giant branch (AGB) stars, and in massive stars. To study the build-up of the s- and i-products at low metallicity, we investigate the abundances of Y, Ba, La, Nd, and Eu in 98 stars, at −2.4 <  [Fe/H] <  −0.9, in the Sculptor dwarf spheroidal galaxy. The chemical enrichment from AGB stars becomes apparent at [Fe/H] ≈ −2 in Sculptor, and causes [Y/Ba], [La/Ba], [Nd/Ba] and [Eu/Ba] to decrease with metallicity, reaching subsolar values at the highest [Fe/H] ≈ −1. To investigate individual nucleosynthetic sites, we compared three n-rich Sculptor stars with theoretical yields. One carbon-enhanced metal-poor (CEMP-no) star with high [Sr, Y, Zr] >  +0.7 is best fit with a model of a rapidly-rotating massive star, the second (likely CH star) with the i-process, while the third has no satisfactory fit. For a more general understanding of the build-up of the heavy elements, we calculate for the first time the cumulative contribution of the s- and i-processes to the chemical enrichment in Sculptor, and compare with theoretical predictions. By correcting for the r-process, we derive [Y/Ba]s/i = −0.85 ± 0.16, [La/Ba]s/i = −0.49 ± 0.17, and [Nd/Ba]s/i = −0.48 ± 0.12, in the overall s- and/or i-process in Sculptor. These abundance ratios are within the range of those of CEMP stars in the Milky Way, which have either s- or i-process signatures. The low [Y/Ba]s/i and [La/Ba]s/i that we measure in Sculptor are inconsistent with them arising from the s-process only, but are more compatible with models of the i-process. Thus we conclude that both the s- and i-processes were important for the build-up of n-capture elements in the Sculptor dwarf spheroidal galaxy.

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