scholarly journals 591 High-velocity Stars in the Galactic Halo Selected from LAMOST DR7 and Gaia DR2

2020 ◽  
Vol 252 (1) ◽  
pp. 3
Author(s):  
Yin-Bi Li ◽  
A-Li Luo ◽  
You-Jun Lu ◽  
Xue-Sen Zhang ◽  
Jiao Li ◽  
...  
Keyword(s):  
High Velocity ◽  
Galactic Halo ◽  
Gaia Dr2

scholarly journals Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Mudumba Parthasarathy ◽  
Tadafumi Matsuno ◽  
Wako Aoki
Keyword(s):  
Effective Temperature ◽  
High Velocity ◽  
Circumstellar Dust ◽  
Evolutionary Status ◽  
Agb Stars ◽  
Horizontal Branch ◽  
Dust Shells ◽  
The Past ◽  
Gaia Dr2 ◽  
Branch Star

Abstract From Gaia DR2 data of eight high-velocity hot post-AGB candidates, LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV −12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (MV) and luminosity (log L/L⊙). All the stars except LS 5107 have an accurate effective temperature (Teff) in the literature. Some of these stars are metal poor, and some of them do not have circumstellar dust shells. In the past, the distances of some stars were estimated to be 6 kpc, which we find to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby, post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses to be in the range 1 M⊙ to 2 M⊙. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal-branch star or post-early-AGB star. LS 3593 and LS 5107 are new high-velocity hot post-AGB stars from Gaia DR2.

scholarly journals Abundances in the Gaseous Galactic Halo

1998 ◽  
Vol 11 (1) ◽  
pp. 86-89
Author(s):  
Ulysses J. Sofia
Keyword(s):  
Interstellar Medium ◽  
Gas Phase ◽  
High Velocity ◽  
Galactic Halo ◽  
Solar Neighborhood ◽  
Local Interstellar Medium ◽  
The Galaxy ◽  
Metal Abundances ◽  
High Velocity Clouds

Abstract The well measured gas-phase abundances in the low halo suggest that this region of the Galaxy has total (gas plus dust) metal abundances which are close to those in the solar neighborhood. The gas-phase abundances in the halo are generally higher than those seen in the disk, however, this affect is likely due to the destruction of dust in the halo clouds. Observations of high velocity clouds (HVCs) in the halo suggest that these clouds have metal abundances which are substantially lower than those measured for the local interstellar medium. These determinations, however, are often of lower quality than those for the low halo because of uncertainties in the hydrogen abundances along the sightlines, in the incorporation of elements into dust, and in the partial ionization of the clouds.

scholarly journals High reddening patches in Gaia DR2

2020 ◽  
Vol 634 ◽  
pp. A33
Author(s):  
Leire Beitia-Antero ◽  
Ana Inés Gómez de Castro ◽  
Raúl de la Fuente Marcos
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Spectroscopic Analysis ◽  
Galactic Halo ◽  
Spiral Galaxies ◽  
Monte Carlo Sampling ◽  
The Other ◽  
Host Galaxies ◽  
Galactic Model ◽  
Gaia Dr2

Context. Deep GALEX UV data show that the extreme outskirts of some spiral galaxies are teeming with star formation. Such young stellar populations evolving so far away from the bulk of their host galaxies challenge our overall understanding of how star formation proceeds at galactic scales. It is at present unclear whether our own Milky Way may also exhibit ongoing and recent star formation beyond the conventional edge of the disk (∼15 kpc). Aims. Using Gaia DR2 data, we aim to determine if such a population is present in the Galactic halo, beyond the nominal radius of the Milky Way disk. Methods. We studied the kinematics of Gaia DR2 sources with parallax values between 1/60 and 1/30 milliarcseconds towards two regions that show abnormally high values of extinction and reddening; the results are compared with predictions from GALAXIA Galactic model. We also plotted the color–magnitude (CM) diagrams with heliocentric distances computed inverting the parallaxes, and studied the effects of the large parallax errors by Monte Carlo sampling. Results. The kinematics point towards a Galactic origin for one of the regions, while the provenance of the stars in the other is not clear. A spectroscopic analysis of some of the sources in the first region confirms that they are located in the halo. The CM diagram of the sources suggests that some of them are young.

scholarly journals MIXING BETWEEN HIGH VELOCITY CLOUDS AND THE GALACTIC HALO

2014 ◽  
Vol 795 (1) ◽  
pp. 99 ◽  
Author(s):  
Jeffrey A. Gritton ◽  
Robin L. Shelton ◽  
Kyujin Kwak
Keyword(s):  
High Velocity ◽  
Galactic Halo ◽  
High Velocity Clouds

scholarly journals Highly Ionized Gas in the Galactic Halo and the High‐Velocity Clouds toward PG 1116+215

2005 ◽  
Vol 157 (2) ◽  
pp. 251-278 ◽  
Author(s):  
Rajib Ganguly ◽  
Kenneth R. Sembach ◽  
Todd M. Tripp ◽  
Blair D. Savage
Keyword(s):  
High Velocity ◽  
Galactic Halo ◽  
Ionized Gas ◽  
High Velocity Clouds

High-Velocity Pulsars in the Galactic Halo

Science ◽  
1992 ◽  
Vol 257 (5072) ◽  
pp. 937-942 ◽  
Author(s):  
D. Eichler ◽  
J. Silk
Keyword(s):  
High Velocity ◽  
Galactic Halo

scholarly journals Search for Stellar Streams in The Galactic Halo From Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 Data

2020 ◽  
Vol 240 ◽  
pp. 07012
Author(s):  
Ni Made Kartika Wijayanti ◽  
Mochamad Ikbal Arifyanto ◽  
Nur Annisa
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Wavelet Transformation ◽  
High Probability ◽  
Galactic Halo ◽  
Tidal Force ◽  
3D Kinematics ◽  
Halo Stars ◽  
Stellar Streams ◽  
Gaia Dr2

Stellar streams are stars which are trapped in the same potensial caused by dynamical resonance or tidal force. We aim to analyze kinematic sub- structures (streams) in the Galactic halo by V vs √ U2+ 2V 2 planes of Arifyanto & Fuchs. We crossmatched data from Gaia DR2, GALAH DR2, RAVE DR5 and LAMOST DR4 based on positions. We have 3D kinematics and metallicity data of halo stars selected from kinematics criteria from ratio of probability of thick disk (TD) over halo (H) less than 0.01. Substructures are detected by using wavelet transformation and corrected using 15 Monte Carlo simulations. We obtained four kinematic structures on V vs √U2 + 2V 2 plane which two of them are associated to BB17-1 and BB17-2 streams. All the streams had a high probability from the extragalactic origin.

scholarly journals The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

2019 ◽  
Vol 492 (3) ◽  
pp. 3241-3262 ◽  
Author(s):  
Kim A Venn ◽  
Collin L Kielty ◽  
Federico Sestito ◽  
Else Starkenburg ◽  
Nicolas Martin ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Model Atmosphere ◽  
Dynamical Analysis ◽  
Success Rates ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Detailed Model ◽  
Bayesian Inference Method ◽  
R Process ◽  
Gaia Dr2

ABSTRACT A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow-band Pristine photometric survey is presented based on CFHT high-resolution ESPaDOnS spectroscopy. We have discovered 28 new bright (V < 15) stars with [Fe/H] < −2.5 and 5 with [Fe/H] < −3.0 for success rates of 40 (28/70) and 19 per cent (5/27), respectively. A detailed model atmosphere analysis is carried out for the 28 new metal-poor stars. Stellar parameters were determined from SDSS photometric colours, Gaia DR2 parallaxes, MESA/MIST stellar isochrones, and the initial Pristine survey metallicities, following a Bayesian inference method. Chemical abundances are determined for 10 elements (Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, and Ba). Most stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo; however, we also report the discoveries of a new r-process-rich star, a new CEMP-s candidate with [Y/Ba] > 0, and a metal-poor star with very low [Mg/Fe]. The kinematics and orbits for all of the highly probable metal-poor candidates are determined by combining our precision radial velocities with Gaia DR2 proper motions. Some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge (Rperi < 0.5 kpc); also, eight stars have orbital energies and actions consistent with the Gaia-Enceladus accretion event. This paper contributes to our understanding of the complex chemo-dynamics of the metal-poor Galaxy, and increases the number of known bright metal-poor stars available for detailed nucleosynthetic studies.

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