scholarly journals Was the Milky Way a chain galaxy? Using the IGIMF theory to constrain the thin-disc star formation history and mass

2018 ◽  
Vol 483 (1) ◽  
pp. 46-56 ◽  
Author(s):  
Akram Hasani Zonoozi ◽  
Hamidreza Mahani ◽  
Pavel Kroupa
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Formation History ◽  
Thin Disc ◽  
Formation History ◽  
A Chain ◽  
Disc Star

scholarly journals High-speed stars: Galactic hitchhikers

2020 ◽  
Vol 638 ◽  
pp. A122 ◽  
Author(s):  
E. Caffau ◽  
L. Monaco ◽  
P. Bonifacio ◽  
L. Sbordone ◽  
M. Haywood ◽  
...  
Keyword(s):  
Star Formation ◽  
High Speed ◽  
Milky Way ◽  
Star Formation History ◽  
Proper Motions ◽  
Orbital Parameters ◽  
Blue Stragglers ◽  
Formation History ◽  
Cool Stars ◽  
Age Estimates

Context. The search for stars born in the very early stages of the Milky Way star formation history is of paramount importance in the study of the early Universe since their chemistry carries irreplaceable information on the conditions in which early star formation and galaxy buildup took place. The search for these objects has generally taken the form of expensive surveys for faint extremely metal-poor stars, the most obvious but not the only candidates to a very early formation. Aims. Thanks to Gaia DR2 radial velocities and proper motions, we identified 72 bright cool stars displaying heliocentric transverse velocities in excess of 500 km s−1. These objects are most likely members of extreme outer-halo populations, either formed in the early Milky Way build-up or accreted from since-destroyed self-gravitating stellar systems. Methods. We analysed low-resolution FORS spectra of the 72 stars in the sample and derived the abundances of a few elements. Despite the large uncertainties on the radial velocity determination, we derived reliable orbital parameters for these objects. Results. The stars analysed are mainly slightly metal poor, with a few very metal-poor stars. Their chemical composition is much more homogeneous than expected. All the stars have very eccentric halo orbits, some extending well beyond the expected dimension of the Milky Way. Conclusions. These stars can be the result of a disrupted small galaxy or they could have been globular cluster members. Age estimates suggest that some of them are evolved blue stragglers, now on the subgiant or asymptotic giant branches.

scholarly journals The Canada–France Imaging Survey: Reconstructing the Milky Way Star Formation History from Its White Dwarf Population

2019 ◽  
Vol 887 (2) ◽  
pp. 148 ◽  
Author(s):  
Nicholas J. Fantin ◽  
Patrick Côté ◽  
Alan W. McConnachie ◽  
Pierre Bergeron ◽  
Jean-Charles Cuillandre ◽  
...  
Keyword(s):  
Star Formation ◽  
White Dwarf ◽  
Milky Way ◽  
Star Formation History ◽  
Formation History

scholarly journals A Comparison of Chemical Evolution between the Milky Way and M31 Galaxy

2006 ◽  
Vol 2 (S235) ◽  
pp. 313-313
Author(s):  
J. Yin ◽  
J.L. Hou ◽  
R.X. Chang ◽  
S. Boissier ◽  
N. Prantzos
Keyword(s):  
Star Formation ◽  
Chemical Evolution ◽  
Milky Way ◽  
Local Group ◽  
Spiral Galaxies ◽  
Star Formation History ◽  
Milky Way Galaxy ◽  
Andromeda Galaxy ◽  
Formation History ◽  
Formation And Evolution

Andromeda galaxy (M31,NGC224) is the biggest spiral in the Local Group. By studying the star formation history(SFH) and chemical evolution of M31, and comparing with the Milky Way Galaxy, we are able to understand more about the formation and evolution of spiral galaxies.

scholarly journals The Massive stellar Population at the Galactic Center

2016 ◽  
Vol 12 (S329) ◽  
pp. 287-291
Author(s):  
Francisco Najarro ◽  
Diego de la Fuente ◽  
Tom R. Geballe ◽  
Don F. Figer ◽  
D. John Hillier
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Milky Way ◽  
Local Group ◽  
Galactic Center ◽  
Spectroscopic Studies ◽  
Star Formation History ◽  
Stellar Content ◽  
Formation History

AbstractWe present results from our ongoing infrared spectroscopic studies of the massive stellar content at the Center of the Milky Way. This region hosts a large number of apparently isolated massive stars as well as three of the most massive resolved young clusters in the Local Group. Our survey seeks to infer the presence of a possible top-heavy recent star formation history and to test massive star formation channels: clusters vs isolation.

The recurrent impact of the Sagittarius dwarf on the star formation history of the Milky Way

2020 ◽  
Vol 4 (10) ◽  
pp. 965-973 ◽  
Author(s):  
Tomás Ruiz-Lara ◽  
Carme Gallart ◽  
Edouard J. Bernard ◽  
Santi Cassisi
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Formation History ◽  
Formation History ◽  
History Of

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 On the recent star formation history of the Milky Way disk

New Astronomy ◽  
2004 ◽  
Vol 9 (6) ◽  
pp. 475-502 ◽  
Author(s):  
R. de la Fuente Marcos ◽  
C. de la Fuente Marcos
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Star Formation History ◽  
Formation History ◽  
History Of

scholarly journals The star formation history in 12 SMC fields

2008 ◽  
Vol 4 (S256) ◽  
pp. 269-274
Author(s):  
Noelia E. D. Noël ◽  
Antonio Aparicio ◽  
Carme Gallart ◽  
Sebastián L. Hidalgo ◽  
Edgardo Costa ◽  
...  
Keyword(s):  
Quantitative Analysis ◽  
Star Formation ◽  
Main Sequence ◽  
Milky Way ◽  
Stellar Populations ◽  
Star Formation History ◽  
Theoretical Studies ◽  
Formation History ◽  
Stellar Halo ◽  
Hubble Time

AbstractWe present a quantitative analysis of the star formation history (SFH) of 12 fields in the Small Magellanic Cloud (SMC) based on unprecedented deep [(B–R),R] color—magnitude diagrams (CMDs) from Noël et al. (2007). Our fields reach down to the oldest main sequence (MS) turnoff with high photometric accuracy, which is vital for obtaining accurate SFHs. We use the IAC-pop code (Aparicio & Hidalgo 2009) to obtain the SFH, using a single CMD generated using IAC-star (Aparicio & Gallart 2004). We find that there are three main periods of enhancement of star formation: a young one peaked at ~0.2–0.5 Gyr old, only present in the eastern and in the central-most fields; one at intermediate ages, peaked at ~4–5 Gyr old in all fields; and an old one, peaked at ~10 Gyr in all the fields but the western ones, in which this old enhancement splits into two, peaked at ~8 Gyr old and at ~12 Gyr old. This “two-enhancement” zone seems to be a robust feature since it is unaffected when using different stellar evolutionary libraries, implying that stars in the SMC take a Hubble time or more to mix. This indicates that there was a global enhancement in ψ(t) at ~4–5 Gyr ago in the SMC. We also find that the age of the old population is similar at all radii and at all azimuth and we constrain the age of this oldest population to be older than ~11.5 Gyr old. The intermediate-age population, in turn, presents variations with both, radii and azimuth. Theoretical studies based on results from larger spatial areas are needed to understand the origin of the young gradient. This young component is highly affected by interactions between Milky Way/LMC/SMC. We do not find yet a region dominated by an old, Milky Way-like, halo at 4.5 kpc from the SMC center, indicating either that this old stellar halo does not exist in the SMC or that its contribution to the stellar populations, at the galactocentric distances of our outermost field, is negligible.

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