scholarly journals The Impact of Stellar Rotation on the Nitrogen Abundance Gradient from OB Stars in the Galactic Disk

2004 ◽  
Vol 215 ◽  
pp. 226-227
Author(s):  
Simone Daflon ◽  
Katia Cunha
Keyword(s):  
Milky Way ◽  
Galactic Disk ◽  
Young Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Ob Stars ◽  
Nitrogen Abundance ◽  
N Enrichment ◽  
The Impact

Massive young stars can be used to trace the current chemical composition of the Galactic disk and to define its metallicity gradient. However, evolutionary models of massive rotating stars predict changes of the surface abundances due to rotationally induced mixing. The abundance analysis of elements sensitive to mixing, such as CNO, can be used to test these rotating stellar models. In this study we identify those stars that show one particular signature of mixing, N-enrichment, in our sample of 70 OB stars for which we have conducted an abundance analysis. This sample is used to define radial metallicity gradients in the Milky Way and we investigate the variation of the calculated nitrogen gradient after the exclusion of these, probably mixing-induced, N-rich stars.

scholarly journals Chemical abundances of fast-rotating OB stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 94-95
Author(s):  
Constantin Cazorla ◽  
Thierry Morel ◽  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
Massive Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Single Star ◽  
Ob Stars ◽  
Detailed Surface ◽  
Normal Nitrogen ◽  
First Time ◽  
Fast Rotating

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.

A numerical study on the distribution of the debris of the Milky Way satellites

2018 ◽  
Vol 14 (S344) ◽  
pp. 105-108
Author(s):  
Matteo Mazzarini ◽  
Andreas Just
Keyword(s):  
Dark Matter ◽  
Gas Dynamics ◽  
Milky Way ◽  
Galactic Disk ◽  
Numerical Study ◽  
Major Axis ◽  
Space Distribution ◽  
Axis Ratio ◽  
Phase Space Distribution ◽  
The Impact

AbstractWe perform six N-body simulations reproducing the interaction between the Milky Way and its satellite galaxies, in order to address the deposit of satellite debris in the Galactic environment. We find that most of the baryons survive inside their host satellites and that most of the baryonic debris ends up in the inner regions of the Milky Way, in contrast to the more uniform distribution of dark matter debris. We also look at the debris Inertia tensor in the inner regions of the Milky Way and find a lower minor-to-major axis ratio for baryons than dark matter. We plan to explore the phase-space distribution of the debris ending in the Galactic disk and bulge. We also plan further simulations including gas dynamics to study the impact of gas on the process.

scholarly journals The Milky Way thin disk structure as revealed by stars and young open clusters

2013 ◽  
Vol 9 (S298) ◽  
pp. 7-16 ◽  
Author(s):  
Giovanni Carraro
Keyword(s):  
Milky Way ◽  
Spiral Structure ◽  
Galactic Center ◽  
Galactic Disk ◽  
Chemical Properties ◽  
Thin Disk ◽  
Open Clusters ◽  
Disk Structure ◽  
The Status ◽  
The Impact

AbstractIn this contribution I shall focus on the structure of the Galactic thin disk. The evolution of the thin disk and its chemical properties have been discussed in detail by T. Bensby's contribution in conjunction with the properties of the Galactic thick disk, and by L.Olivia in conjunction with the properties of the Galactic bulge. I will review and discuss the status of our understanding of three major topics, which have been the subject of intense research nowadays, after long years of silence: (1) the spiral structure of the Milky Way, (2) the size of the Galactic disk, and (3) the nature of the Local arm (Orion spur), where the Sun is immersed. The provisional conclusions of this discussion are that: (1) we still have quite a poor knowledge of the Milky Way spiral structure, and the main disagreements among various tracers are still to be settled; (2) the Galactic disk does clearly not have an obvious luminous cut-off at about 14 kpc from the Galactic center, and next generation Galactic models need to be updated in this respect, and (3) the Local arm is most probably an inter-arm structure, similar to what we see in several external spirals, like M 74. Finally, the impact of Gaia and LAMOST in this field will be briefly discussed as well.

scholarly journals Observations of Stellar Rotation and Line Strengths for Ob Stars

1970 ◽  
Vol 4 ◽  
pp. 115-115
Author(s):  
William Buscombe
Keyword(s):  
National Science Foundation ◽  
Absorption Lines ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
B Stars ◽  
Ob Stars ◽  
Luminosity Class ◽  
National Science ◽  
Balmer Lines ◽  
Hydrogen Lines

For 121 southern stars of spectral types between 05 and A3, including 35 supergiants, equivalent widths and values of ve sini have been measured for absorption lines on direct-intensity tracings of coudé spectrograms from Mount Stromlo, with original dispersion 150 microns per angstrom. For stars of a particular temperature and luminosity class, the strength of the hydrogen lines is weaker and the triplet helium lines stronger in fast rotators than in sharp-lined objects which are rotating more slowly. Full details are in print (Monthly Notices Roy. Astron. Soc. 144 (1969), 1): subsequent papers in press present detailed profiles of the Balmer lines for 23 slowly rotating stars and details of emission features shown by several fast rotators.The investigation is being continued with spectrograms of northern B stars secured at the Dominion Astrophysical Observatory, supported in part by grant GP-13544 from the National Science Foundation.

scholarly journals The evolution of CNO isotopes: the impact of massive stellar rotators

2019 ◽  
Vol 490 (2) ◽  
pp. 2838-2854 ◽  
Author(s):  
Donatella Romano ◽  
Francesca Matteucci ◽  
Zhi-Yu Zhang ◽  
Rob J Ivison ◽  
Paolo Ventura
Keyword(s):  
Chemical Evolution ◽  
High Redshift ◽  
Extreme Environments ◽  
Turbulent Medium ◽  
Initial Mass Function ◽  
High Mass ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
The Impact ◽  
The Imf

ABSTRACT Chemical abundances and abundance ratios measured in galaxies provide precious information about the mechanisms, modes, and time-scales of the assembly of cosmic structures. Yet, the nucleogenesis and chemical evolution of elements heavier than helium are dictated mostly by the physics of the stars and the shape of the stellar mass spectrum. In particular, estimates of CNO isotopic abundances in the hot, dusty media of high-redshift starburst galaxies offer a unique glimpse into the shape of the stellar initial mass function (IMF) in extreme environments that cannot be accessed with direct observations (star counts). Underlying uncertainties in stellar evolution and nucleosynthesis theory, however, may hurt our chances of getting a firm grasp of the IMF in these galaxies. In this work, we adopt new yields for massive stars, covering different initial rotational velocities. First, we implement the new yield set in a well-tested chemical evolution model for the Milky Way. The calibrated model is then adapted to the specific case of a prototype submillimetre galaxy (SMG). We show that, if the formation of fast-rotating stars is favoured in the turbulent medium of violently star-forming galaxies irrespective of metallicity, the IMF needs to be skewed towards high-mass stars in order to explain the CNO isotopic ratios observed in SMGs. If, instead, stellar rotation becomes negligible beyond a given metallicity threshold, as is the case for our own Galaxy, there is no need to invoke a top-heavy IMF in starbursts.

scholarly journals Evolution and appearance of Be stars in SMC clusters

2009 ◽  
Vol 5 (S266) ◽  
pp. 470-473
Author(s):  
C. Martayan ◽  
D. Baade ◽  
Y. Frémat ◽  
J. Zorec
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Open Cluster ◽  
Central Star ◽  
Open Clusters ◽  
Be Stars ◽  
Ob Stars ◽  
Be Star ◽  
The Impact ◽  
Key Parameter

AbstractStar clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases during which the classical Be stars occur, which—unlike HAe/Be stars—are not pre-main-sequence objects, nor supergiants. Rather, they are extremely rapidly rotating B-type stars with a circumstellar decretion disk formed by episodic ejections of matter from the central star. To study the impact of mass, metallicity, and age on the Be phase, we observed Small Magellanic Cloud (SMC) open clusters with two different techniques: (i) with the ESO–WFI in slitless mode, which allowed us to find the brighter Be and other emission-line stars in 84 SMC open clusters, and (ii) with the VLT–FLAMES multifiber spectrograph to determine accurately the evolutionary phases of Be stars in the Be-star-rich SMC open cluster NGC 330. Based on a comparison to the Milky Way, a model of Be stellar evolution, appearance as a function of metallicity and mass, and spectral type is developed, involving the fractional critical rotation rate as a key parameter.

The role of stellar rotation in Tidal Disruption Events

2018 ◽  
Vol 14 (S342) ◽  
pp. 272-274
Author(s):  
Andrea Sacchi ◽  
Giuseppe Lodato
Keyword(s):  
Black Hole ◽  
Galactic Nuclei ◽  
High Energy ◽  
Stellar Structure ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
Smoothed Particle ◽  
The Impact

AbstractTidal Disruption Events (TDEs) are highly variable high energy phenomena originating from Galactic Nuclei (Komossa & Bade 1999). TDEs are thus powerful tools to study quiescent Galactic Nuclei given their extreme brightness (several times super-Eddington) and the possibility of being seen in non-AGN galaxies. A TDE is the violent disruption of a star passing by a Super Massive Black Hole (SMBH); after the disruption, roughly half of the star mass gains enough energy to escape from the Black Hole, while the other half is bound to the Hole, falls back and eventually accretes onto it. Early works, (Rees 1988), pointed out a t−5/3 behaviour for the light curves of this event and since then such a time dependency became the signature of these events. Strong deviations are however introduced when one considers the internal stellar structure or if one considers partial disruptions. One feature that has never been taken into account is the effect of stellar rotation in the resulting fallback rate, which is the aim of the present work. Firstly, we will show analytical estimates of the impact of stellar rotation on the TDE and we will then present a set of Smoothed Particle Hydrodynamic simulations of the tidal disruption of rotating stars, performed in order to test these analytical estimates.

scholarly journals The impact of stellar rotation on the CNO abundance patterns in the Milky Way at low metallicities

2010 ◽  
Author(s):  
Cristina Chiappini ◽  
Raphael Hirschi ◽  
F. Matteucci ◽  
G. Meynet ◽  
S. Ekström ◽  
...  
Keyword(s):  
Milky Way ◽  
Stellar Rotation ◽  
Abundance Patterns ◽  
The Impact

scholarly journals The impact of inelastic self-interacting dark matter on the dark matter structure of a Milky Way halo

2020 ◽  
Author(s):  
Kun Ting Eddie Chua ◽  
Karia Dibert ◽  
Mark Vogelsberger ◽  
Jesús Zavala
Keyword(s):  
Dark Matter ◽  
High Speed ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Direct Detection ◽  
Major Axis ◽  
Inelastic Collisions ◽  
Axis Ratio ◽  
Lower Velocity ◽  
The Impact

Abstract We study the effects of inelastic dark matter self-interactions on the internal structure of a simulated Milky Way (MW)-size halo. Self-interacting dark matter (SIDM) is an alternative to collisionless cold dark matter (CDM) which offers a unique solution to the problems encountered with CDM on sub-galactic scales. Although previous SIDM simulations have mainly considered elastic collisions, theoretical considerations motivate the existence of multi-state dark matter where transitions from the excited to the ground state are exothermic. In this work, we consider a self-interacting, two-state dark matter model with inelastic collisions, implemented in the Arepo code. We find that energy injection from inelastic self-interactions reduces the central density of the MW halo in a shorter timescale relative to the elastic scale, resulting in a larger core size. Inelastic collisions also isotropize the orbits, resulting in an overall lower velocity anisotropy for the inelastic MW halo. In the inner halo, the inelastic SIDM case (minor-to-major axis ratio s ≡ c/a ≈ 0.65) is more spherical than the CDM (s ≈ 0.4), but less spherical than the elastic SIDM case (s ≈ 0.75). The speed distribution f(v) of dark matter particles at the location of the Sun in the inelastic SIDM model shows a significant departure from the CDM model, with f(v) falling more steeply at high speeds. In addition, the velocity kicks imparted during inelastic collisions produce unbound high-speed particles with velocities up to 500 km s−1 throughout the halo. This implies that inelastic SIDM can potentially leave distinct signatures in direct detection experiments, relative to elastic SIDM and CDM.

scholarly journals A mushroom-shaped structure from the impact of a cloud with the Galactic disk

2004 ◽  
Vol 423 (1) ◽  
pp. 183-188 ◽  
Author(s):  
Takahiro Kudoh ◽  
Shantanu Basu
Keyword(s):  
Galactic Disk ◽  
The Impact
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