scholarly journals Galactic warp from the kinematics of OB stars

2020 ◽  
Vol 240 ◽  
pp. 07008
Author(s):  
Rizky Maulana Nurhidayat ◽  
Mochamad Ikbal Arifyanto ◽  
Lucky Puspitarini
Keyword(s):  
Milky Way ◽  
Gravitational Interaction ◽  
Stellar Disk ◽  
Vertical Position ◽  
Maximum Deviation ◽  
Complex Structures ◽  
Ob Stars ◽  
The Galaxy ◽  
Oscillating Motion ◽  
Galactic Warp

The warp in Milky Way seen through the young stellar disk shows the complex structures. Its spatial distribution reveals the asymmetry in the vertical distance to the galactic midplane, whereas the kinematics shows the os- cillating motion. We analyze the warp using about 25,000 OB stars from Gaia Data Release 2, with Galactocentric azimuth (φ) range from 135◦ to 225◦ . We detect the warp from two distinctive regions. First region (warp down) lies on 100◦ < l < 150◦ and second regions (warp up) lies on 150◦ < l < 220◦ . The vertical position towards the Galactic midplane (Z) from all samples shows the line-of-nodes of the warp is on φ = 174◦ ± 2◦ . The maximum deviation in warp down region reachs 0.1 kpc and 0.2 kpc in warp up region. The vertical velocity (VZ) from both regions are dominated by negative VZ . From the kinematics dis- tribution, it can be concluded that there is an oscillati1ng motion. Considering with the previous study, the oscillating motion was caused by the gravitational interaction with the Galaxy satellites. From this, we can constrain the origin of the warp is developing from the tidal interaction between Milky Way and its satellites.

scholarly journals Getting a Kick out of the Stellar Disk(s) in the Galactic Center

2007 ◽  
Vol 3 (S246) ◽  
pp. 275-276 ◽  
Author(s):  
H. B. Perets ◽  
G. Kupi ◽  
T. Alexander
Keyword(s):  
High Velocity ◽  
Galactic Center ◽  
Stellar System ◽  
Young Stars ◽  
Stellar Disk ◽  
Ob Stars ◽  
The Galaxy ◽  
Young Clusters

AbstractRecent observations of the Galactic center revealed a nuclear disk of young OB stars, in addition to many similar outlying stars with higher eccentricities and/or high inclinations relative to the disk (some of them possibly belonging to a second disk). Binaries in such nuclear disks, if they exist in non-negligible fractions, could have a major role in the evolution of the disks through binary heating of this stellar system. We suggest that interactions with/in binaries may explain some (or all) of the observed outlying young stars in the Galactic center. Such stars could have been formed in a disk, and later on kicked out from it through binary related interactions, similar to ejection of high velocity runaway OB stars in young clusters throughout the galaxy.

A Star Is Born

2017 ◽  
Author(s):  
John Chambers ◽  
Jacqueline Mitton
Keyword(s):  
Milky Way ◽  
Rotating Disk ◽  
Stellar Disk ◽  
Mass Star ◽  
Fine Dust ◽  
Solar Mass ◽  
Milky Way Galaxy ◽  
Supermassive Black Hole ◽  
The Galaxy ◽  
Main Component

This chapter focuses on the nature and composition of the Milky Way galaxy. The main component of the Milky Way is a rotating disk of stars some 100,000 light-years across but only about 1,000 light-years thick. Between the stars lies an extremely tenuous mixture of gas and fine dust grains called the interstellar medium. The disk of stars is only about 1,000 light-years thick but becomes thicker near the Milky Way's center, where a bar-shaped bulge of densely packed stars surrounds a supermassive black hole at the heart of the galaxy. Enveloping the thin stellar disk is an extended disk of gas about 10 times thicker. Today, stars are forming in the Milky Way at a rate equivalent to one solar-mass star every year. Judging by the age of its oldest members, the Milky Way has been giving birth to new stars for over 13 billion years.

scholarly journals Spiral Arm Tangencies in the Milky Way

2008 ◽  
Vol 4 (S254) ◽  
pp. 319-322 ◽  
Author(s):  
Robert A. Benjamin
Keyword(s):  
Milky Way ◽  
Density Wave ◽  
The Other ◽  
Stellar Disk ◽  
Mid Infrared ◽  
Space Telescope ◽  
The Galaxy ◽  
Infrared Star ◽  
Spiral Arm ◽  
Infrared Star Counts

AbstractThe historical directions of spiral arm tangencies in the Milky Way are presented and compared to results of mid-infrared star counts using the Spitzer Space Telescope. While the Scutum and Centaurus tangency directions show a 20-30% excess of star counts, all other expected tangency directions show no similar increases. These two tangencies are probably associated with a density wave arm that comes off the near side of the bar of the Galaxy while the other arms whose tangencies are not detected may be compression in the gas, but not in the old stellar disk.

scholarly journals How does the stellar disk of the Milky Way get its gas?

2017 ◽  
Vol 13 (S334) ◽  
pp. 219-222
Author(s):  
Sebastián E. Nuza ◽  
Cristina Chiappini ◽  
Cecilia Scannapieco ◽  
Ivan Minchev ◽  
Marie Martig ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Milky Way ◽  
Thin Disk ◽  
Stellar Disk ◽  
Galactocentric Distance ◽  
Chemical Abundances ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
History Of ◽  
Inside Out

AbstractIn chemodynamical evolution models it is usually assumed that the Milky Way galaxy forms from the inside-out implying that gas inflows onto the disk decrease with galactocentric distance. Similarly, to reproduce differences between chemical abundances of the thick disk and bulge with respect to those of the thin disk, higher accretion fluxes at early times are postulated. By using a suite of Milky Way-like galaxies extracted from cosmological simulations, we investigate the accretion of gas on the simulated stellar disks during their whole evolution. In general, we find that the picture outlined above holds, although the detailed behavior depends on the assembly history of the Galaxy and the complexities inherent to the physics of galaxy formation.

The Long View of Planetary Systems

2018 ◽  
Author(s):  
Karel Schrijver
Keyword(s):  
Solar System ◽  
Milky Way ◽  
Planetary Systems ◽  
Giant Planets ◽  
Milky Way Galaxy ◽  
Population Statistics ◽  
The Past ◽  
General Terms ◽  
The Galaxy ◽  
The Universe

How many planetary systems formed before our’s did, and how many will form after? How old is the average exoplanet in the Galaxy? When did the earliest planets start forming? How different are the ages of terrestrial and giant planets? And, ultimately, what will the fate be of our Solar System, of the Milky Way Galaxy, and of the Universe around us? We cannot know the fate of individual exoplanets with great certainty, but based on population statistics this chapter sketches the past, present, and future of exoworlds and of our Earth in general terms.

scholarly journals The globular cluster system of the Auriga simulations

2020 ◽  
Vol 496 (1) ◽  
pp. 638-648 ◽  
Author(s):  
Timo L R Halbesma ◽  
Robert J J Grand ◽  
Facundo A Gómez ◽  
Federico Marinacci ◽  
Rüdiger Pakmor ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Milky Way ◽  
Cluster Formation ◽  
Solar Radius ◽  
High Mass ◽  
Formation Model ◽  
The Galaxy ◽  
High Mass Loss ◽  
Globular Cluster System ◽  
Varying Mass

ABSTRACT We investigate whether the galaxy and star formation model used for the Auriga simulations can produce a realistic globular cluster (GC) population. We compare statistics of GC candidate star particles in the Auriga haloes with catalogues of the Milky Way (MW) and Andromeda (M31) GC populations. We find that the Auriga simulations do produce sufficient stellar mass for GC candidates at radii and metallicities that are typical for the MW GC system (GCS). We also find varying mass ratios of the simulated GC candidates relative to the observed mass in the MW and M31 GCSs for different bins of galactocentric radius metallicity (rgal–[Fe/H]). Overall, the Auriga simulations produce GC candidates with higher metallicities than the MW and M31 GCS and they are found at larger radii than observed. The Auriga simulations would require bound cluster formation efficiencies higher than 10 per cent for the metal-poor GC candidates, and those within the Solar radius should experience negligible destruction rates to be consistent with observations. GC candidates in the outer halo, on the other hand, should either have low formation efficiencies, or experience high mass-loss for the Auriga simulations to produce a GCS that is consistent with that of the MW or M31. Finally, the scatter in the metallicity as well as in the radial distribution between different Auriga runs is considerably smaller than the differences between that of the MW and M31 GCSs. The Auriga model is unlikely to give rise to a GCS that can be consistent with both galaxies.

USE OF THE GALAXY AS A TOOL FOR SPATIAL AND TEMPORAL ORIENTATION DURING THE EARLY ISLAMIC PERIOD AND UP TO THE 15TH CENTURY

2021 ◽  
Vol 31 (1) ◽  
pp. 1-44
Author(s):  
Andreas Eckart
Keyword(s):  
Milky Way ◽  
The Other ◽  
Temporal Orientation ◽  
Islamic Period ◽  
Space And Time ◽  
15Th Century ◽  
Other Hand ◽  
The Galaxy ◽  
Early Islamic Period ◽  
Early Islamic

AbstractWe study to what extent the Milky Way was used as an orientation tool at the beginning of the Islamic period covering the 8th to the 15th century, with a focus on the first half of that era. We compare the texts of three authors from three different periods and give detailed comments on their astronomical and traditional content. The text of al-Marzūqī summarises the information on the Milky Way put forward by the astronomer and geographer ʾAbū Ḥanīfa al-Dīnawarī. The text makes it clear that in some areas the Milky Way could be used as a geographical guide to determine the approximate direction toward a region on Earth or the direction of prayer. In the 15th century, the famous navigator Aḥmad b. Māǧid describes the Milky Way in his nautical instructions. He frequently demonstrates that the Milky Way serves as a guidance aid to find constellations and stars that are useful for precise navigation on land and at sea. On the other hand, Ibn Qutayba quotes in his description of the Milky Way a saying from the famous Bedouin poet Ḏū al-Rumma, which is also mentioned by al-Marzūqī. In this saying the Milky Way is used to indicate the hot summer times in which travelling the desert was particularly difficult. Hence, the Milky Way was useful for orientation in space and time and was used for agricultural and navigational purposes.

scholarly journals The accreted nuclear clusters of the Milky Way

2020 ◽  
Vol 500 (2) ◽  
pp. 2514-2524
Author(s):  
Joel Pfeffer ◽  
Carmela Lardo ◽  
Nate Bastian ◽  
Sara Saracino ◽  
Sebastian Kamann
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxy ◽  
Star Clusters ◽  
Host Galaxy ◽  
The Galaxy ◽  
Nuclear Clusters ◽  
The Common ◽  
Massive Clusters ◽  
Peculiar Case

ABSTRACT A number of the massive clusters in the halo, bulge, and disc of the Galaxy are not genuine globular clusters (GCs) but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs and can be readily traced back to their host galaxy (e.g. M54 and the Sagittarius Dwarf galaxy), others have proven more elusive. Here, we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, ω Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken, and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate-mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster–cluster merger.

scholarly journals Demography of galactic technosignatures

2020 ◽  
Vol 500 (2) ◽  
pp. 2278-2288
Author(s):  
Claudio Grimaldi
Keyword(s):  
Statistical Estimation ◽  
Milky Way ◽  
Comprehensive Overview ◽  
Direct Observations ◽  
The Galaxy ◽  
Electromagnetic Emissions ◽  
Average Longevity

ABSTRACT Probabilistic arguments about the existence of technological life beyond Earth traditionally refer to the Drake equation to draw possible estimates of the number of technologically advanced civilizations releasing, either intentionally or not, electromagnetic emissions in the Milky Way. Here, we introduce other indicators than Drake’s number ND to develop a demography of artificial emissions populating the Galaxy. We focus on three main categories of statistically independent signals (isotropic, narrow beams, and rotating beacons) to calculate the average number NG of emission processes present in the Galaxy and the average number of them crossing Earth, $\bar{k}$, which is a quantity amenable to statistical estimation from direct observations. We show that $\bar{k}$ coincides with ND only for isotropic emissions, while $\bar{k}$ can be orders of magnitude smaller than ND in the case of highly directional signals. We further show that while ND gives the number of emissions being released at the present time, NG considers also the signals from no longer active emitters but whose emissions still occupy the Galaxy. We find that as long as the average longevity of the emissions is shorter than about 105 yr, NG is fully determined by the rate of emissions alone, in contrast to ND and $\bar{k}$ which depend also on the emission longevity. Finally, using analytic formulas of NG, ND, and $\bar{k}$ determined for each type of emission processes here considered, we provide a comprehensive overview of the values these quantities can possibly achieve as functions of the emission birthrates, longevities, and directionality.

scholarly journals A Statistical Estimation of the Occurrence of Extraterrestrial Intelligence in the Milky Way Galaxy

Galaxies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 5
Author(s):  
Xiang Cai ◽  
Jonathan H. Jiang ◽  
Kristen A. Fahy ◽  
Yuk L. Yung
Keyword(s):  
Statistical Estimation ◽  
Milky Way ◽  
Galactic Center ◽  
Model Simulation ◽  
Temporal Variations ◽  
Extraterrestrial Intelligence ◽  
Milky Way Galaxy ◽  
The Galaxy ◽  
Peak Location ◽  
Intelligent Life

In the field of astrobiology, the precise location, prevalence, and age of potential extraterrestrial intelligence (ETI) have not been explicitly explored. Here, we address these inquiries using an empirical galactic simulation model to analyze the spatial–temporal variations and the prevalence of potential ETI within the Galaxy. This model estimates the occurrence of ETI, providing guidance on where to look for intelligent life in the Search for ETI (SETI) with a set of criteria, including well-established astrophysical properties of the Milky Way. Further, typically overlooked factors such as the process of abiogenesis, different evolutionary timescales, and potential self-annihilation are incorporated to explore the growth propensity of ETI. We examine three major parameters: (1) the likelihood rate of abiogenesis (λA); (2) evolutionary timescales (Tevo); and (3) probability of self-annihilation of complex life (Pann). We found Pann to be the most influential parameter determining the quantity and age of galactic intelligent life. Our model simulation also identified a peak location for ETI at an annular region approximately 4 kpc from the galactic center around 8 billion years (Gyrs), with complex life decreasing temporally and spatially from the peak point, asserting a high likelihood of intelligent life in the galactic inner disk. The simulated age distributions also suggest that most of the intelligent life in our galaxy are young, thus making observation or detection difficult.

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