scholarly journals The Disc Origin of the Milky Way Bulge

2016 ◽  
Vol 33 ◽  
Author(s):  
P. Di Matteo
Keyword(s):  
Milky Way ◽  
Complex Structure ◽  
Galactic Bulge ◽  
Galactic Disc ◽  
Major Step ◽  
Thick Disc ◽  
Global Properties ◽  
Out Of Plane ◽  
The Galaxy ◽  
Main Components

AbstractThe Galactic bulge, that is the prominent out-of-plane over-density present in the inner few kiloparsecs of the Galaxy, is a complex structure, as the morphology, kinematics, chemistry, and ages of its stars indicate. To understand the nature of its main components—those at [Fe/H] ≳ −1 dex—it is necessary to make an inventory of the stellar populations of the Galactic disc(s), and of their borders: the chemistry of the disc at the solar vicinity, well known from detailed studies of stars over many years, is not representative of the whole disc. This finding, together with the recent revisions of the mass and sizes of the thin and thick discs, constitutes a major step in understanding the bulge complexity. N-body models of a boxy-/peanut-shaped bulge formed from a thin disc through the intermediary of a bar have been successful in interpreting a number of global properties of the Galactic bulge, but they fail in reproducing the detailed chemo-kinematic relations satisfied by its components and their morphology. It is only by adding the thick disc to the picture that we can understand the nature of the Galactic bulge.

scholarly journals Reviving old controversies: is the early Galaxy flat or round?

2020 ◽  
Vol 636 ◽  
pp. A115 ◽  
Author(s):  
P. Di Matteo ◽  
M. Spite ◽  
M. Haywood ◽  
P. Bonifacio ◽  
A. Gómez ◽  
...  
Keyword(s):  
Stellar Population ◽  
Milky Way ◽  
Galactic Disc ◽  
Chemical Abundances ◽  
First Stars ◽  
Thick Disc ◽  
Large Program ◽  
The Galaxy ◽  
Early Galaxy ◽  
Two Populations

We analysed a set of very metal-poor stars, for which accurate chemical abundances have been obtained as part of the ESO Large Program “First stars” in the light of the Gaia DR2 data. The kinematics and orbital properties of the stars in the sample show they probably belong to the thick disc, partially heated to halo kinematics, and to the accreted Gaia Sausage-Enceladus satellite. The continuity of these properties with stars at both higher ([Fe/H] >  −2) and lower metallicities ([Fe/H] <  −4.) suggests that the Galaxy at [Fe/H] ≲ −0.5 and down to at least [Fe/H] ∼ −6 is dominated by these two populations. In particular, we show that the disc extends continuously from [Fe/H] ≤ −4 (where stars with disc-like kinematics have recently been discovered) up to [Fe/H] ≥ −2, the metallicity regime of the Galactic thick disc. An “ultra metal-poor thick disc” does indeed exist, constituting the extremely metal-poor tail of the canonical Galactic thick disc, and extending the latter from [Fe/H] ∼ −0.5 up to the most metal-poor stars discovered in the Galaxy to date. These results suggest that the disc may be the main, and possibly the only, stellar population that has formed in the Galaxy at these metallicities. This would mean that the dissipative collapse that led to the formation of the old Galactic disc must have been extremely fast. We also discuss these results in the light of recent simulation efforts made to reproduce the first stages of Milky Way-type galaxies.

scholarly journals Planetary nebulae in the inner Milky Way

2009 ◽  
Vol 5 (S265) ◽  
pp. 354-355
Author(s):  
Oscar Cavichia ◽  
Roberto D. D. Costa ◽  
Walter J. Maciel
Keyword(s):  
Statistical Analysis ◽  
Milky Way ◽  
Planetary Nebulae ◽  
Galactic Bulge ◽  
Intermediate Mass ◽  
Disk Interface ◽  
The Galaxy ◽  
Outer Border ◽  
Good Agreement

AbstractNew abundances of planetary nebulae located towards the bulge of the Galaxy are derived based on observations made at LNA (Brazil). We present accurate abundances of the elements He, N, S, O, Ar, and Ne for 56 PNe located towards the galactic bulge. The data shows a good agreement with other results in the literature, in the sense that the distribution of the abundances is similar to those works. From the statistical analysis performed, we can suggest a bulge-disk interface at 2.2 kpc for the intermediate mass population, marking therefore the outer border of the bulge and inner border of the disk.

scholarly journals The Evolutionary History of the Milky Way

1996 ◽  
Vol 171 ◽  
pp. 3-10
Author(s):  
K.C. Freeman
Keyword(s):  
Evolutionary History ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Galactic Disk ◽  
Small Satellite ◽  
Galactic Bulge ◽  
The Galaxy ◽  
History Of ◽  
Satellite Galaxies

The accretion of small satellite galaxies appears to have been important in the formation of the metal-poor halo of the Galaxy. The disrupting Sgr dwarf galaxy and the recent discovery of a young, metal-poor component of the halo indicate that this is a continuing process. The evolution of the galactic disk, and some consequences of the bar-like nature of the galactic bulge are briefly discussed.

scholarly journals The tale of the Milky Way globular cluster NGC 6362 – I. The orbit and its possible extended star debris features as revealed by Gaia DR2

2019 ◽  
Vol 489 (4) ◽  
pp. 4565-4573
Author(s):  
Richa Kundu ◽  
José G Fernández-Trincado ◽  
Dante Minniti ◽  
Harinder P Singh ◽  
Edmundo Moreno ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Plane ◽  
Vertical Component ◽  
Galactic Disc ◽  
Corotation Radius ◽  
Magnitude Diagram ◽  
The Galaxy ◽  
History Of ◽  
Event Based ◽  
Gaia Dr2

ABSTRACTWe report the identification of possible extended star debris candidates beyond the cluster tidal radius of NGC 6362 based on the second Gaia data release (Gaia DR2). We found 259 objects possibly associated with the cluster lying in the vicinity of the giant branch and 1–2 magnitudes fainter/brighter than the main-sequence turn-off in the cluster colour–magnitude diagram and which cover an area on the sky of ∼4.1 deg2 centred on the cluster. We traced back the orbit of NGC 6362 in a realistic Milky Way potential, using the gravpot16 package, for 3 Gyr. The orbit shows that the cluster shares similar orbital properties as the inner disc, having peri-/apogalactic distances, and maximum vertical excursion from the Galactic plane inside the corotation radius (CR), moving inwards from CR radius to visit the inner regions of the Milky Way. The dynamical history of the cluster reveals that it has crossed the Galactic disc several times in its lifetime and has recently undergone a gravitational shock, ∼15.9 Myr ago, suggesting that less than 0.1 per cent of its mass has been lost during the current disc-shocking event. Based on the cluster’s orbit and position in the Galaxy, we conclude that the possible extended star debris candidates are a combined effect of the shocks from the Galactic disc and evaporation from the cluster. Lastly, the evolution of the vertical component of the angular momentum shows that the cluster is strongly affected dynamically by the Galactic bar potential.

VVV Microlensing events in the far side of the Milky Way

2019 ◽  
Vol 14 (S353) ◽  
pp. 35-37
Author(s):  
María Gabriela Navarro ◽  
Dante Minniti ◽  
Rodrigo Contreras Ramos
Keyword(s):  
Milky Way ◽  
The Other ◽  
Line Of Sight ◽  
Galactic Bulge ◽  
Near Ir ◽  
The Galaxy ◽  
Different Populations ◽  
First Time

AbstractIn order to study the most reddened areas of the Milky Way we used near-IR data from the VVV Survey. For the first time, the VISTA telescope allows us to observe the mid-plane through the Galactic bulge and study the disk in the other side of the Milky Way. Motivated by the detection of hundreds of microlensing events in the inner regions of the Galaxy, we propose three new configurations of microlensing events, placing the sources in the far-disk and the lenses in the far-disk/bulge/near-disk. These new configurations will change the usual way to interpret the timescale distributions due to the different populations along the line of sight, that exhibit varied transverse velocities and relative distances.

Recovering the origin of the lenticular galaxy NGC3115 using multi-band photometry

2019 ◽  
Vol 15 (S359) ◽  
pp. 421-423
Author(s):  
Maria Luísa Buzzo ◽  
Arianna Cortesi ◽  
Ariel Werle ◽  
Claudia Mendes de Oliveira
Keyword(s):  
Stellar Population ◽  
Galactic Nuclei ◽  
Two Phase ◽  
Thick Disc ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Minor Mergers ◽  
Main Components ◽  
Baryonic Mass ◽  
Multi Band

AbstractWe perform simultaneous multi-band fitting, using the routine GALFITM, of the galaxy NGC3115, in order to recover the stellar populations of its main components (a bulge, a thin disc and a thick disc). We model 11 bands, from ultraviolet to infrared, in order to take into account the galaxy younger stellar population and the presence of the Active Galactic Nuclei (AGN). We find that the majority of the galaxy baryonic mass belongs to the thick disc, which is also the oldest galaxy component, consistent with results from the literature. Differently from previous works, we find that the bulge has the bluest colour and it is younger than the thick disc, either as a result of recent star formation activity, or AGN feedback, or white dwarf emission in an old stellar population. Finally, we propose that NGC3115 was formed either through a two-phase formation scenario, or via an outside-in quenching of an isolated spiral galaxy, whose thick disc had been heated-up via minor mergers with dwarf satellites.

The thick disc according to Gaia-ESO

2017 ◽  
Vol 12 (S330) ◽  
pp. 218-219 ◽  
Author(s):  
Louise M. Howes ◽  
Thomas Bensby
Keyword(s):  
Stellar Populations ◽  
Selection Function ◽  
Selection Effects ◽  
Galactic Disc ◽  
Thick Disc ◽  
Vertical Extent ◽  
Data Release ◽  
The Galaxy

AbstractIn the era of large spectroscopic surveys, it is vital that selection effects are taken into account when making conclusions about the stellar populations of the Galaxy. Here we use the Galactic disc sample of stars from the Gaia-ESO Survey internal data release 4 (GES iDR4), applying the published selection function to characterise the vertical extent of the chemically defined thick and thin discs.

scholarly journals Stellar multiplicity in the Milky Way Galaxy

2017 ◽  
Vol 13 (S334) ◽  
pp. 366-367
Author(s):  
E. Stonkutė ◽  
R. P. Church ◽  
S. Feltzing ◽  
J. A. Johnson
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Milky Way ◽  
Galactic Disc ◽  
Chemical Abundances ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
Tentative Evidence ◽  
Evolution Algorithm ◽  
Binary Evolution

AbstractWe present our models of the effect of binaries on high-resolution spectroscopic surveys. We want to determine how many binary stars will be observed, whether unresolved binaries will contaminate measurements of chemical abundances, and how we can use spectroscopic surveys to better constrain the population of binary stars in the Galaxy. Using a rapid binary-evolution algorithm that enables modelling of the most complex binary systems we generate a series of large binary populations in the Galactic disc and evaluate the results. As a first application we use our model to study the binary fraction in APOGEE giants. We find tentative evidence for a change in binary fraction with metallicity.

scholarly journals The contribution of the Galactic Bulge to the Galactic rotation curve

1993 ◽  
Vol 153 ◽  
pp. 353-354
Author(s):  
I.V. Petrovskaya ◽  
S. Ninković
Keyword(s):  
Mass Distribution ◽  
Rotation Curve ◽  
Milky Way ◽  
Galactic Rotation ◽  
Galactic Bulge ◽  
Distinct Population ◽  
Gravitation Field ◽  
The Galaxy ◽  
Galactic Rotation Curve

It is not always clear what the bulge of the Galaxy is: a region close to the centre, a subsystem formed by a distinct population, or a mixture of populations but characterised by its own mass distribution. We consider the bulge of the Milky Way as a subsystem and thus contributing to the galactic gravitation field. We want to estimate the contribution of the galactic bulge to the rotation curve.

scholarly journals Predicting the LISA white dwarf binary population in the Milky Way with cosmological simulations

2019 ◽  
Vol 490 (4) ◽  
pp. 5888-5903 ◽  
Author(s):  
Astrid Lamberts ◽  
Sarah Blunt ◽  
Tyson B Littenberg ◽  
Shea Garrison-Kimmel ◽  
Thomas Kupfer ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
White Dwarf ◽  
Milky Way ◽  
Thick Disc ◽  
Distance Distributions ◽  
The Galaxy ◽  
Stellar Halo ◽  
Galaxy Model ◽  
Orbital Periods ◽  
Binary Evolution

ABSTRACT White dwarf binaries with orbital periods below 1 h will be the most numerous sources for the space-based gravitational wave detector Laser Interferometer Space Antenna (LISA). Based on thousands of individually resolved systems, we will be able to constrain binary evolution and provide a new map of the Milky Way and its close surroundings. In this paper we predict the main properties of populations of different types of detached white dwarf binaries detected by LISA over time. For the first time, we combine a high-resolution cosmological simulation of a Milky Way-mass galaxy (taken from the FIRE project) with a binary population synthesis model for low- and intermediate-mass stars. Our Galaxy model therefore provides a cosmologically realistic star formation and metallicity history for the Galaxy and naturally produces its different components such as the thin and thick disc, the bulge, the stellar halo, and satellite galaxies and streams. Thanks to the simulation, we show how different Galactic components contribute differently to the gravitational wave signal, mostly due to their typical age and distance distributions. We find that the dominant LISA sources will be He–He double white dwarfs (DWDs) and He–CO DWDs with important contributions from the thick disc and bulge. The resulting sky map of the sources is different from previous models, with important consequences for the searches for electromagnetic counterparts and data analysis. We also emphasize that much of the science-enabling information regarding white dwarf binaries, such as the chirp mass and the sky localization, becomes increasingly rich with long observations, including an extended mission up to 8 yr.

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