Hunting for Dwarf Galaxies Hosting the Formation and Coalescence of Compact Binaries

Here we introduce the latest version of the GAMESH model, capable to consistently account for the formation and evolution of compact binary systems along the cosmic assembly of a Milky Way (MW)-like galaxy, centered on a local group volume resolving a large population of dwarf satellites. After describing the galaxy assembly process and how the formation of binary systems is accounted for, we summarize some recent findings on the properties and evolution of low-metallicity dwarf galaxies hosting the birth/coalescence of stellar/compact binaries generating GW150914-like signals. Finally, we focus on the mass and orbital properties of the above compact binary candidates assessing their impact on the resulting coalescence times and on selecting suitable galaxy hosts.

Download Full-text

On particle acceleration and transport in plasmas in the Galaxy: theory and observations

Journal of Plasma Physics ◽

10.1017/s0022377821000064 ◽

2021 ◽

Vol 87 (1) ◽

Author(s):

Elena Amato ◽

Sabrina Casanova

Keyword(s):

Particle Acceleration ◽

Cosmic Rays ◽

Galactic Cosmic Rays ◽

Energetic Particles ◽

Quality Data ◽

Current Status ◽

The Earth ◽

The Galaxy ◽

Formation And Evolution ◽

Galaxy Assembly

Accelerated particles are ubiquitous in the Cosmos and play a fundamental role in many processes governing the evolution of the Universe at all scales, from the sub-AU scale relevant for the formation and evolution of stars and planets to the Mpc scale involved in Galaxy assembly. We reveal the presence of energetic particles in many classes of astrophysical sources thanks to their production of non-thermal radiation, and we detect them directly at the Earth as cosmic rays. In the last two decades both direct and indirect observations have provided us a wealth of new, high-quality data about cosmic rays and their interactions both in sources and during propagation, in the Galaxy and in the Solar System. Some of the new data have confirmed existing theories about particle acceleration and propagation and their interplay with the environment in which they occur. Some others have brought about interesting surprises, whose interpretation is not straightforward within the standard framework and may require a change of paradigm in terms of our ideas about the origin of cosmic rays of different species or in different energy ranges. In this article, we focus on cosmic rays of galactic origin, namely with energies below a few petaelectronvolts, where a steepening is observed in the spectrum of energetic particles detected at the Earth. We review the recent observational findings and the current status of the theory about the origin and propagation of galactic cosmic rays.

Download Full-text

Subaru Hyper Suprime-Cam Survey for the Local Group Dwarf Galaxies: Ursa Minor

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318006518 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 94-95

Author(s):

Yutaka Komiyama

Keyword(s):

Binary Systems ◽

Main Sequence ◽

Local Group ◽

Dwarf Galaxies ◽

Structural Parameters ◽

Deep Imaging ◽

Ursa Minor ◽

Red Giant

AbstractWe have carried out a wide and deep imaging survey for the Local Group dwarf spheroidal galaxy Ursa Minor (UMi) using Hyper Suprime-Cam (HSC). The data cover out beyond the nominal tidal radius down to ~25 mag in i band, which is ~2 mag below the main sequence turn-off point. The structural parameters of UMi are derived using red giant branch (RGB) stars and sub-giant branch (SGB) stars, and the tidal radius is suggested to be larger than those estimated by the previous studies. It is also found that the distribution of bluer RGB/SGB stars is more extended than that of redder RGB/SGB stars. The fraction of binary systems is estimated to be ~0.4 from the morphology of the main sequences.

Download Full-text

Pushing back the limits: detailed properties of dwarf galaxies in a ΛCDM universe

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832669 ◽

2018 ◽

Vol 616 ◽

pp. A96 ◽

Cited By ~ 26

Author(s):

Yves Revaz ◽

Pascale Jablonka

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Mass Scale ◽

Dwarf Spheroidal Galaxies ◽

The Galaxy ◽

Dynamical Simulations ◽

Ursa Minor ◽

Stellar Properties ◽

Star Formation Histories

We present the results of a set of high-resolution chemo-dynamical simulations of dwarf galaxies in a ΛCDM cosmology. Out of an original (3.4 Mpc/h)3 cosmological box, a sample of 27 systems are re-simulated from z = 70 to z = 0 using a zoom-in technique. Gas and stellar properties are confronted to the observations in the greatest details: in addition to the galaxy global properties, we investigated the model galaxy velocity dispersion profiles, half-light radii, star formation histories, stellar metallicity distributions, and [Mg/Fe] abundance ratios. The formation and sustainability of the metallicity gradients and kinematically distinct stellar populations are also tackled. We show how the properties of six Local Group dwarf galaxies, NGC 6622, Andromeda II, Sculptor, Sextans, Ursa Minor and Draco are reproduced, and how they pertain to three main galaxy build-up modes. Our results indicate that the interaction with a massive central galaxy could be needed for a handful of Local Group dwarf spheroidal galaxies only, the vast majority of the systems and their variety of star formation histories arising naturally from a ΛCDM framework. We find that models fitting well the local Group dwarf galaxies are embedded in dark haloes of mass between 5 × 108 to a few 109 M⊙, without any missing satellite problem. We confirm the failure of the abundance matching approach at the mass scale of dwarf galaxies. Some of the observed faint however gas-rich galaxies with residual star formation, such as Leo T and Leo P, remain challenging. They point out the need of a better understanding of the UV-background heating.

Download Full-text

Local Group Dwarf Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318005835 ◽

2018 ◽

Vol 14 (S344) ◽

pp. 29-37

Author(s):

Andrew A. Cole

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Cosmic Time ◽

Star Formation History ◽

Gas Content ◽

Cosmological Context ◽

Low Mass ◽

Formation And Evolution ◽

Star Formation Histories

AbstractLocal Group dwarf galaxies are a unique astrophysical laboratory because they are the only objects in which we can reliably and precisely characterize the star formation histories of low-mass galaxies going back to the epoch of reionization. There are of order 100 known galaxies less massive than the Small Magellanic Cloud within ~1 Megaparsec of the Milky Way, with a vide variety of star formation history, gas content, and mass to light ratios. In this overview the current understanding of the formation and evolution of low-mass galaxies across cosmic time will be presented, and the possibility of drawing links between the properties of individual systems and the broader Local Group and cosmological context will be discussed. Local Group dwarfs will remain a uniquely powerful testbed to constrain the properties of dark matter and to evaluate the performance of simulations for the foreseeable future.

Download Full-text

Deep spectroscopy of the dwarf spheroidal NGC 185

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312011477 ◽

2011 ◽

Vol 7 (S283) ◽

pp. 370-371

Author(s):

Denise R. Gonçalves ◽

Laura Magrini ◽

Lucimara P. Martins ◽

Ana M. Teodorescu ◽

Cintia Quireza ◽

...

Keyword(s):

Emission Line ◽

Chemical Evolution ◽

Dwarf Galaxies ◽

Seyfert Galaxy ◽

Ionization Mechanisms ◽

The Galaxy ◽

Nearby Galaxies ◽

Formation And Evolution ◽

Nuclear Regions ◽

Galaxy Population

AbstractDwarf galaxies are crucial to understand the formation and evolution of galaxies, since they constitute the most abundant galaxy population. Abundance ratios and their variations due to star formation and inflow/outflow of gas are key constraints to chemical evolution models. The determination of these abundances in the dwarf galaxies of the Local Universe is thus of extreme importance. NGC 185 is one of the four brightest dwarf companions of M31, but unlike the other three it has an important content of gas and dust. Interestingly enough, in an optical survey of bright nearby galaxies NGC 185 was classified as a Seyfert galaxy based on its integrated emission-line ratios in the nuclear regions. However, although its emission lines formally place it in the category of Seyfert it is probable that this galaxy does not contain a genuine active nucleus. In this contribution, we resume, firstly, our results of an empirical study of the galaxy, on which we characterise its emission-line population and obtain planetary nebulae abundance ratios (Gonçalves et al. 2012). And, secondly, we discuss our attempt to identify the possible ionization mechanisms for NGC 185 enlighting the controversial classification of this galaxy dwarf spheroidal (dSph) as well as Seyfert, via stellar population synthesis and chemical evolution modelling (Martins et al. 2011).

Download Full-text

Stars at Low Metallicity in Dwarf Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s174392130802499x ◽

2008 ◽

Vol 4 (S255) ◽

pp. 310-317

Author(s):

Eline Tolstoy ◽

Giuseppina Battaglia ◽

Andrew Cole

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Wide Field ◽

Irregular Galaxy ◽

First Stars ◽

Field Spectroscopy ◽

Low Metallicity

AbstractDwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the recent target of deep HST/ACS imaging (Cole et al. 2007) and the Sculptor dwarf spheroidal, which has been the target of significant wide field spectroscopy with VLT/FLAMES (Battaglia 2007).

Download Full-text

A Comparison between Second-Order Post-Newtonian Hamiltonian and Coherent Post-Newtonian Lagrangian in Spinning Compact Binaries

Symmetry ◽

10.3390/sym13040584 ◽

2021 ◽

Vol 13 (4) ◽

pp. 584

Author(s):

Xu-Hui Cheng ◽

Guo-Qing Huang

Keyword(s):

Binary Systems ◽

Equations Of Motion ◽

Exact Result ◽

Spin Coupling ◽

Spin Orbit Coupling ◽

Compact Binaries ◽

Numerical Investigations ◽

Compact Binary ◽

The Difference ◽

Spin Spin Coupling

In relativistic celestial mechanics, post-Newtonian (PN) Lagrangian and PN Hamiltonian formulations are not equivalent to the same PN order as our previous work in PRD (2015). Usually, an approximate Lagrangian is used to discuss the difference between a PN Hamiltonian and a PN Lagrangian. In this paper, we investigate the dynamics of compact binary systems for Hamiltonians and Lagrangians, including Newtonian, post-Newtonian (1PN and 2PN), and spin–orbit coupling and spin–spin coupling parts. Additionally, coherent equations of motion for 2PN Lagrangian are adopted here to make the comparison with Hamiltonian approaches and approximate Lagrangian approaches at the same condition and same PN order. The completely opposite nature of the dynamics shows that using an approximate PN Lagrangian is not convincing. Hence, using the coherent PN Lagrangian is necessary for obtaining an exact result in the research of dynamics of compact binary at certain PN order. Meanwhile, numerical investigations from the spinning compact binaries show that the 2PN term plays an important role in causing chaos in the PN Hamiltonian system.

Download Full-text

It has to be cool: Supergiant progenitors of binary black hole mergers from common-envelope evolution

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038707 ◽

2021 ◽

Vol 645 ◽

pp. A54

Author(s):

Jakub Klencki ◽

Gijs Nelemans ◽

Alina G. Istrate ◽

Martyna Chruslinska

Keyword(s):

Mass Transfer ◽

Binary Systems ◽

Binding Energies ◽

Convective Envelope ◽

Binary Black Holes ◽

Common Envelope ◽

Compact Binary ◽

Massive Binary Systems ◽

Binary Mergers ◽

Low Metallicity

Common-envelope (CE) evolution in massive binary systems is thought to be one of the most promising channels for the formation of compact binary mergers. In the case of merging binary black holes (BBHs), the essential CE phase takes place at a stage when the first BH is already formed and the companion star expands as a supergiant. We aim to decipher the kinds of BH binaries with supergiant companions that could potentially evolve through and survive a CE phase. To this end, we compute envelope binding energies from detailed massive stellar models at different evolutionary stages and metallicities. We make multiple physically extreme choices of assumptions that favor easier CE ejection as well as account for recent advancements in mass-transfer stability criteria. We find that even with the most optimistic assumptions, a successful CE ejection in BH binaries is only possible if the donor is a massive convective-envelope giant, namely a red supergiant (RSG). The same is true for neutron-star binaries with massive companions. In other words, pre-CE progenitors of BBH mergers are BH binaries with RSG companions. We find that because of its influence on the radial expansion of massive giants, metallicity has an indirect but a very strong effect on the chemical profile, density structure, and the binding energies of RSG envelopes. Our results suggest that merger rates from population-synthesis models could be severely overestimated, especially at low metallicity. Additionally, the lack of observed RSGs with luminosities above log(L/L⊙) ≈ 5.6 − 5.8, corresponding to stars with M ≳ 40 M⊙, puts into question the viability of the CE channel for the formation of the most massive BBH mergers. Either such RSGs elude detection due to very short lifetimes, or they do not exist and the CE channel can only produce BBH systems with total mass ≲50 M⊙. Finally, we discuss an alternative CE scenario in which a partial envelope ejection is followed by a phase of possibly long and stable mass transfer.

Download Full-text

The ACS LCID project: accurate measurements of the full star formation history in low metallicity, isolated, Local Group dwarf galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308025131 ◽

2008 ◽

Vol 4 (S255) ◽

pp. 392-396

Author(s):

Matteo Monelli ◽

Keyword(s):

Star Formation ◽

Local Group ◽

Dwarf Galaxies ◽

Stellar System ◽

Star Formation History ◽

Dominant Component ◽

Formation History ◽

Magnitude Diagram ◽

Technical Issues ◽

Low Metallicity

AbstractWe present here the latest results of the LCID project (Local Cosmology from Isolated Dwarfs), aimed at recovering the full star formation history (SFH) of six isolated dwarf galaxies of the Local Group (LG). Our method of analysis is based on the IAC-pop code, which derives the SFH of a resolved stellar system by comparing the observed and a model color-magnitude diagram (CMD). We summarize here basic technical issues and the main results concerning our sample of galaxies. We show that LeoA is the only object showing a clear delay in the onset of the major SF event, while all the other galaxies present a dominant component older than 10 Gyrs.

Download Full-text

The Pristine survey – X. A large population of low-metallicity stars permeates the Galactic disc

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa022 ◽

2020 ◽

Vol 497 (1) ◽

pp. L7-L12 ◽

Cited By ~ 3

Author(s):

Federico Sestito ◽

Nicolas F Martin ◽

Else Starkenburg ◽

Anke Arentsen ◽

Rodrigo A Ibata ◽

...

Keyword(s):

Dwarf Galaxies ◽

Large Population ◽

Building Blocks ◽

Proper Motions ◽

Galactic Disc ◽

Isotropic Pressure ◽

History Of ◽

Low Metallicity ◽

The Common ◽

Gaia Dr2

ABSTRACT The orbits of the least chemically enriched stars open a window on the formation of our Galaxy when it was still in its infancy. The common picture is that these low-metallicity stars are distributed as an isotropic, pressure-supported component since these stars were either accreted from the early building blocks of the assembling Milky Way (MW), or were later brought by the accretion of faint dwarf galaxies. Combining the metallicities and radial velocities from the Pristine and LAMOST surveys and Gaia DR2 parallaxes and proper motions for an unprecedented large and unbiased sample of 1027 very metal poor stars at [Fe/H] ≤ −2.5 dex, we show that this picture is incomplete. We find that $31{{\ \rm per\ cent}}$ of the stars that currently reside spatially in the disc ($|Z| \le 3{\rm \, kpc}$) do not venture outside of the disc plane throughout their orbit. Moreover, this sample shows strong statistical evidence (at the 5.0σ level) of asymmetry in their kinematics, favouring prograde motion. The discovery of this population implies that a significant fraction of stars with iron abundances [Fe/H] ≤ −2.5 dex merged into, formed within, or formed concurrently with the MW disc and that the history of the disc was quiet enough to allow them to retain their disc-like orbital properties, challenging theoretical and cosmological models.

Download Full-text