scholarly journals Neutralino annihilation intoγrays in the Milky Way and in external galaxies

2004 ◽  
Vol 70 (10) ◽  
Author(s):  
N. Fornengo ◽  
L. Pieri ◽  
S. Scopel
Keyword(s):  
Milky Way ◽  
External Galaxies

scholarly journals First Gaia dynamical model of the Milky Way disc with six phase space coordinates: a test for galaxy dynamics

2020 ◽  
Vol 494 (4) ◽  
pp. 6001-6011 ◽  
Author(s):  
Maria Selina Nitschai ◽  
Michele Cappellari ◽  
Nadine Neumayer
Keyword(s):  
Phase Space ◽  
Milky Way ◽  
Dynamical Model ◽  
Total Density ◽  
Dark Halo ◽  
Stellar Kinematics ◽  
Galaxy Dynamics ◽  
Dispersion Tensor ◽  
External Galaxies ◽  
Solar Position

ABSTRACT We construct the first comprehensive dynamical model for the high-quality subset of stellar kinematics of the Milky Way disc, with full 6D phase-space coordinates, provided by the Gaia Data Release 2. We adopt an axisymmetric approximation and use an updated Jeans Anisotropic Modelling (JAM) method, which allows for a generic shape and radial orientation of the velocity ellipsoid, as indicated by the Gaia data, to fit the mean velocities and all three components of the intrinsic velocity dispersion tensor. The Milky Way is the first galaxy for which all intrinsic phase space coordinates are available, and the kinematics are superior to the best integral-field kinematics of external galaxies. This situation removes the long-standing dynamical degeneracies and makes this the first dynamical model highly overconstrained by the kinematics. For these reasons, our ability to fit the data provides a fundamental test for both galaxy dynamics and the mass distribution in the Milky Way disc. We tightly constrain the volume average total density logarithmic slope, in the radial range 3.6–12 kpc, to be αtot = −2.149 ± 0.055 and find that the dark halo slope must be significantly steeper than αDM = −1 (NFW). The dark halo shape is close to spherical and its density is ρDM(R⊙) = 0.0115 ± 0.0020 M⊙ pc−3 (0.437 ± 0.076 GeV cm−3), in agreement with previous estimates. The circular velocity at the solar position vcirc(R⊙) = 236.5 ± 3.1 km s−1 (including systematics) and its gently declining radial trends are also consistent with recent determinations.

scholarly journals Symposium summary: stellar populations in bulges

2007 ◽  
Vol 3 (S245) ◽  
pp. 459-462 ◽  
Author(s):  
Beatriz Barbuy
Keyword(s):  
Milky Way ◽  
Stellar Populations ◽  
External Galaxies

AbstractStellar populations in the Milky Way and in external galaxies are reviewed, based on the conferences and posters presented at this meeting.

scholarly journals 2D chemical evolution model: The impact of Galactic disc asymmetries on azimuthal chemical abundance variations

2019 ◽  
Vol 628 ◽  
pp. A38 ◽  
Author(s):  
E. Spitoni ◽  
G. Cescutti ◽  
I. Minchev ◽  
F. Matteucci ◽  
V. Silva Aguirre ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Density Fluctuations ◽  
Evolution Model ◽  
Galactic Disc ◽  
Chemical Abundance ◽  
Oxygen Abundance ◽  
External Galaxies ◽  
The Impact ◽  
Chemical Evolution Model

Context. Galactic disc chemical evolution models generally ignore azimuthal surface density variation that can introduce chemical abundance azimuthal gradients. Recent observations, however, have revealed chemical abundance changes with azimuth in the gas and stellar components of both the Milky Way and external galaxies. Aims. Our aim is to quantify the effects of spiral arm density fluctuations on the azimuthal variations of the oxygen and iron abundances in disc galaxies. Methods. We developed a new 2D Galactic disc chemical evolution model that is capable of following not just radial but also azimuthal inhomogeneities. Results. The density fluctuations resulting from a Milky Way-like N-body disc formation simulation produce azimuthal variations in the oxygen abundance gradients of the order of 0.1 dex. Moreover, the azimuthal variations are more evident in the outer Galactic regions, which is in agreement with the most recent observations in external galaxies. Using a simple analytical model, we show that the largest fluctuations with azimuth result near the spiral structure co-rotation resonance where the relative speed between the spiral and gaseous disc is the slowest. Conclusion. We provide a new 2D chemical evolution model capable of following azimuthal density variations. Density fluctuations extracted from a Milky Way-like dynamical model lead to a scatter in the azimuthal variations of the oxygen abundance gradient, which is in agreement with observations in external galaxies. We interpret the presence of azimuthal scatter at all radii by the presence of multiple spiral modes moving at different pattern speeds, as found in both observations and numerical simulations.

scholarly journals The Distribution of Young Stars in Nearby Galaxies

1986 ◽  
Vol 116 ◽  
pp. 61-80 ◽  
Author(s):  
W. L. Freedman
Keyword(s):  
Spatial Distribution ◽  
Milky Way ◽  
Young Stars ◽  
Panoramic View ◽  
Star Forming ◽  
Individual Stars ◽  
Star Forming Regions ◽  
The Galaxy ◽  
External Galaxies ◽  
Nearby Galaxies

Although luminous stars are relatively rare, they can potentially be studied out to large distances. In our own Milky Way, this advantage is offset by obscuration due to dust in the plane of the Galaxy. In addition, distances to these individual stars are extremely difficult to determine. The study of external galaxies allows a panoramic view of the system and its individually brightest stars which are all at a common distance. The spatial distribution of star forming regions is immediately apparent, and the effects of obscuration are minimized. Nearby resolved galaxies therefore provide a rich resource for examining the properties of the intrinsically brightest stars and their relation to other components of the galaxy.

scholarly journals Lithium and beryllium in the Gaia-Enceladus galaxy

2020 ◽  
Vol 496 (3) ◽  
pp. 2902-2909
Author(s):  
P Molaro ◽  
G Cescutti ◽  
X Fu
Keyword(s):  
Milky Way ◽  
Local Group ◽  
Galactic Halo ◽  
Dwarf Galaxy ◽  
Chemical Abundances ◽  
Dwarf Stars ◽  
Evolution Experiment ◽  
External Galaxies ◽  
Low Metallicity ◽  
Gaia Dr2

ABSTRACT Data from Gaia DR2 and The Apache Point Observatory Galactic Evolution Experiment surveys revealed a relatively new component in the inner Galactic halo, which is likely the dynamical remnant of a disrupted dwarf galaxy named Gaia-Enceladus that collided with the Milky Way about 10 Gyr ago. This merging event offers an extraordinary opportunity to study chemical abundances of elements in a dwarf galaxy, since they are generally hampered in external galaxies. Here, we focus on 7Li and 9Be in dwarf stars that are out of reach even in Local Group galaxies. Searching in GALAH, Gaia-ESO survey and in literature, we found several existing 7Li abundance determinations of stars belonging to the Gaia-Enceladus galaxy. The 7Li abundances of stars at the low metallicity end overlap with those of the Galactic halo. These are effective extragalactic 7Li measurements, which suggest that the 7Li Spite plateau is universal, as is the cosmological 7Li problem. We found a 7Li-rich giant out of 101 stars, which suggests a small percentage similar to that of the Milky Way. We also collect 9Be abundance for a subsample of 25 Gaia-Enceladus stars from literature. Their abundances share the Galactic [Be/H] values at the low metallicity end but grow slower with [Fe/H] and show a reduced dispersion. This suggests that the scatter observed in the Milky Way could reflect the different 9Be evolution patterns of different stellar components that are mixed-up in the Galactic halo.

scholarly journals Preface: Special Session SpS16 Unexplained Spectral Phenomena in the Interstellar Medium

2012 ◽  
Vol 10 (H16) ◽  
pp. 695-696
Keyword(s):  
Interstellar Medium ◽  
Near Infrared ◽  
Milky Way ◽  
Magellanic Clouds ◽  
Special Session ◽  
Milky Way Galaxy ◽  
Sn 1987A ◽  
Diffuse Interstellar Bands ◽  
External Galaxies

There are several outstanding mysteries in interstellar medium spectroscopy which have remained unsolved after decades of effort. The diffuse interstellar bands (DIBs) have been known for almost a century (Heger 1922). Although more than 400 bands from the near UV to near infrared have been detected, none of them has been identified. In the Milky Way Galaxy, DIBs have been seen towards over one hundred stars. In the Magellanic Clouds, DIBs have been seen in the spectrum of SN 1987A as well as in the spectra of reddened stars (Ehrenfreund et al. 2002). DIB carriers in the interstellar medium of external galaxies can be probed by supernovae (Sollerman et al. 2005), and DIBs have been detected in external galaxies with redshifts up to 0.5 (Sarre 2006).

scholarly journals The Milky Way nuclear star cluster beyond 1 pc

2013 ◽  
Vol 9 (S303) ◽  
pp. 223-227
Author(s):  
A. Feldmeier ◽  
N. Neumayer ◽  
A. Seth ◽  
P. T. de Zeeuw ◽  
R. Schödel ◽  
...  
Keyword(s):  
Black Hole ◽  
Milky Way ◽  
Kinematic Model ◽  
Star Clusters ◽  
Star Cluster ◽  
Stellar Disk ◽  
Reference Object ◽  
Black Hole Mass ◽  
Data Set ◽  
External Galaxies

AbstractWithin the central 10 pc of our Galaxy lies a dense cluster of stars, the nuclear star cluster, forming a distinct component of our Galaxy. Nuclear star clusters are common objects and are detected in ∼75% of nearby galaxies. It is, however, not fully understood how nuclear clusters form. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve its stellar populations and kinematics much better than in external galaxies. This makes the Milky Way nuclear star cluster a reference object for understanding the structure and assembly history of all nuclear star clusters.We have obtained an unparalleled data set using the near-infrared long-slit spectrograph ISAAC (VLT) in a novel drift-scan technique to construct an integral-field spectroscopic map of the central ∼10 × 8 pc of our Galaxy. To complement our data set we also observed fields out to a distance of ∼19 pc along the Galactic plane to disentangle the influence of the nuclear stellar disk.From this data set we extract a stellar kinematic map using the CO bandheads and an emission line kinematic map using H2 emission lines. Using the stellar kinematics, we set up a kinematic model for the Milky Way nuclear star cluster to derive its mass and constrain the central Galactic potential. Because the black hole mass in the Milky Way is precisely known, this kinematic data set will also serve as a benchmark for testing black hole mass modeling techniques used in external galaxies.

RAMSES II Raman Search for Extragalactic Symbiotic Stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 347-348
Author(s):  
Rodolfo Angeloni ◽  
Denise R. Gonçalves ◽  
Ruben J. Diaz ◽  
Keyword(s):  
Milky Way ◽  
Compact Star ◽  
Symbiotic Stars ◽  
Giant Star ◽  
Long Period ◽  
Early Results ◽  
The Galaxy ◽  
External Galaxies ◽  
Striking Contrast

AbstractSymbiotic stars (SySts) are long-period interacting binaries composed of a hot compact star, an evolved giant star, and a tangled network of gas and dust nebulae. Presently, we know 252 SySts in the Milky Way and 62 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySts in our Galaxy. In this contribution, I present the concept and the early results from RAMSES II (Raman Search for Extragalactic Symbiotic Stars), a Gemini/GMOS Upgrade Project which makes use of the Raman OVI 6830Å band as a powerful photometric tool to identify new SySts, within and beyond the Galaxy.

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