scholarly journals Maser Astrometry: from Galactic Structure to Local Group Cosmology

2012 ◽  
Vol 8 (S287) ◽  
pp. 359-367 ◽  
Author(s):  
Mark J. Reid
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Milky Way ◽  
Local Group ◽  
Galactic Structure ◽  
Proper Motions ◽  
Star Forming ◽  
Fundamental Parameters ◽  
3 Dimensional ◽  
Star Forming Regions

AbstractThis review summarizes current advances in astrometry of masers as they pertain to large-scale Galactic structure and dynamics and Local Group cosmology. Parallaxes and proper motions have now been measured for more than 60 massive star forming regions using the Japanese VERA array, the EVN and the VLBA. These results provide “gold standard” distances and 3-dimensional velocities for sources across the Milky Way, revealing its spiral structure. Modeling these data tightly constrains the fundamental parameters of the Milky Way: R0 and Θ0. Proper motions of Local Group galaxies have been measured, improving our understanding of the history and fate of the Group.

scholarly journals The large-scale distribution and physical properties of massive star forming regions in the Milky Way

2007 ◽  
Vol 3 (S242) ◽  
pp. 228-229
Author(s):  
Jarken Esimbek ◽  
Zhou Jianjun ◽  
Zheng Xingwu
Keyword(s):  
Physical Properties ◽  
Large Scale ◽  
Massive Star ◽  
Milky Way ◽  
Spectral Lines ◽  
Recombination Line ◽  
Star Forming ◽  
Star Forming Regions ◽  
Hydrogen Recombination ◽  
Large Survey

AbstractWe are conducting a large survey with the Urumqi 25 m radio telescope to study the distribution and physical properties of massive star forming regions in the Milky Way. We will accomplish this by observing the H110α hydrogen recombination line at 4.874 GHz and the H2CO absorption line at 4830 GHz. These lines are associated with compact HII regions and dense molecular clouds. As a test of the 6 cm spectral line receiving system, we observed the two spectral lines toward massive star forming regions. We plan to study the large scale distribution and physical properties of massive star forming regions in the Milky way.

scholarly journals TRIGONOMETRIC PARALLAXES OF MASSIVE STAR-FORMING REGIONS. VI. GALACTIC STRUCTURE, FUNDAMENTAL PARAMETERS, AND NONCIRCULAR MOTIONS

2009 ◽  
Vol 700 (1) ◽  
pp. 137-148 ◽  
Author(s):  
M. J. Reid ◽  
K. M. Menten ◽  
X. W. Zheng ◽  
A. Brunthaler ◽  
L. Moscadelli ◽  
...  
Keyword(s):  
Massive Star ◽  
Galactic Structure ◽  
Star Forming ◽  
Fundamental Parameters ◽  
Star Forming Regions ◽  
Trigonometric Parallaxes

scholarly journals Galactic structure from trigonometric parallaxes of star-forming regions

2012 ◽  
Vol 8 (S289) ◽  
pp. 188-193 ◽  
Author(s):  
Mark J. Reid
Keyword(s):  
Interstellar Dust ◽  
Milky Way ◽  
Galactic Center ◽  
Star Forming ◽  
Fundamental Parameters ◽  
Star Forming Regions ◽  
Long Baseline ◽  
The Galaxy ◽  
Trigonometric Parallaxes ◽  
3D Information

AbstractRecently, astrometric accuracy approaching ~ 10 μas has become routinely possible with Very Long Baseline Interferometry. Since, unlike at optical wavelengths, interstellar dust is transparent at radio wavelengths, parallaxes and proper motions can now be measured for massive young stars (with maser emission) across the Galaxy, enabling direct measurements of the spiral structure of the Milky Way. Fitting the full 3D position and velocity vectors to a simple model of the Galaxy yields extremely accurate values for its fundamental parameters, including the distance to the Galactic Center, R0=8.38 ± 0.18 kpc, and circular rotation at the Solar Circle, Θ0 = 243 ± 7 km s−1. The rotation curve of the Milky Way, based for the first time on ‘gold standard’ distances and complete 3D information, appears to be very flat.

scholarly journals OB stars towards NGC 6357 and NGC 6334

2017 ◽  
Vol 12 (S330) ◽  
pp. 341-342
Author(s):  
Delphine Russeil
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Stellar Population ◽  
Proper Motions ◽  
Massive Star Formation ◽  
Ob Stars ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ngc 6334

AbstractThe star forming regions NGC6334 and NGC6357 are amid the most active star-forming complexes of our Galaxy where massive star formation is occuring. Both complexes gather several HII regions but they exhibit different aspects: NGC6334 is characterised by a dense molecular ridge where recent massive star formation is obvious while NGC6357 is dominated by the action of the stellar cluster Pismis 24 which have shaped a large cavity. To understand and compare the formation of massive stars in these two regions requires to precise the distance and characterise the proper motions of the O to B3 stellar population in these regions.

scholarly journals Radial Infall onto a Massive Molecular Filament

2015 ◽  
Vol 11 (A29B) ◽  
pp. 711-713
Author(s):  
Cara Battersby ◽  
Philip C. Myers ◽  
Yancy L. Shirley ◽  
Eric Keto ◽  
Helen Kirk
Keyword(s):  
Large Scale ◽  
Massive Star ◽  
Massive Stars ◽  
Physical Structure ◽  
Line Profiles ◽  
Dark Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Current Mass ◽  
Structure Density

AbstractThe newly discovered Massive Molecular Filament (MMF) G32.02+0.05 (~ 70 pc long, 105 M⊙) has been shaped and compressed by older generations of massive stars. The similarity of this filament in physical structure (density profile, temperature) to much smaller star-forming filaments, suggests that the mechanism to form such filaments may be a universal process. The densest portion of the filament, apparent as an Infrared Dark Cloud (IRDC) shows a range of massive star formation signatures throughout. We investigate the kinematics in this filament and find widespread inverse P cygni asymmetric line profiles. These line asymmetries are interpreted as a signature of large-scale radial collapse. Using line asymmetries observed with optically thick HCO+ (1-0) and optically thin H13CO+ (1-0) across a range of massive star forming regions in the filament, we estimate the global radial infall rate of the filament to range from a few 100 to a few 1000 M⊙ Myr−1 pc−1. At its current infall rate the densest portions of the cloud will more than double their current mass within a Myr.

scholarly journals Solo dwarfs – III. Exploring the orbital origins of isolated Local Group galaxies with Gaia Data Release 2

2020 ◽  
Vol 501 (2) ◽  
pp. 2363-2377
Author(s):  
Alan W McConnachie ◽  
Clare R Higgs ◽  
Guillaume F Thomas ◽  
Kim A Venn ◽  
Patrick Côté ◽  
...  
Keyword(s):  
Milky Way ◽  
Local Group ◽  
Dwarf Galaxies ◽  
Proper Motions ◽  
Star Forming ◽  
Isolated Galaxies ◽  
Data Release ◽  
Red Giant ◽  
Ngc 6822 ◽  
Interaction History

ABSTRACT We measure systemic proper motions for distant dwarf galaxies in the Local Group and investigate if these isolated galaxies have ever had an interaction with the Milky Way or M31. We cross-match photometry of isolated, star-forming, dwarf galaxies in the Local Group, taken as part of the Solo survey, with astrometric measurements from Gaia Data Release 2. We find that NGC 6822, Leo A, IC 1613, and WLM have sufficient supergiants with reliable astrometry to derive proper motions. An additional three galaxies (Leo T, Eridanus 2, and Phoenix) are close enough that their proper motions have already been derived using red giant branch stars. Systematic errors in Gaia DR2 are significant for NGC 6822, IC 1613, and WLM. We explore the orbits for these galaxies, and conclude that Phoenix, Leo A, and WLM are unlikely to have interacted with the Milky Way or M31, unless these large galaxies are very massive (${\gtrsim}1.6 \times 10^{12}\, \mathrm{M}_\odot$). We rule out a past interaction of NGC 6822 with M31 at ${\sim}99.99{{\ \rm per\ cent}}$ confidence, and find there is a <10 per cent chance that NGC 6822 has had an interaction with the Milky Way. We examine the likely origins of NGC 6822 in the periphery of the young Local Group, and note that a future interaction of NGC 6822 with the Milky Way or M31 in the next 4 Gyr is essentially ruled out. Our measurements indicate that future Gaia data releases will provide good constraints on the interaction history for the majority of these galaxies.

scholarly journals Maser astrometry with VERA and Galactic structure

2012 ◽  
Vol 8 (S287) ◽  
pp. 386-390 ◽  
Author(s):  
Mareki Honma ◽  
Takumi Nagayama ◽  
Tomoya Hirota ◽  
Naoko Matsumoto ◽  
Nobuyuki Sakai ◽  
...  
Keyword(s):  
Rotation Curve ◽  
Galactic Structure ◽  
Proper Motions ◽  
Late Type ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Maser Sources

AbstractSince 2007 VERA (VLBI Exploration of Radio Astrometry) has been producing astrometric results (distances and/or proper motions) for Galactic maser sources. Nearly 30 parallaxes have been obtained for star-forming regions and late-type stars. By using VERA's astrometric results for star-forming regions, combined with those obtained with VLBA and EVN, fundamental Galactic parameters and Galactic structure may be derived. Our results show that R0 = 8.4 ± 0.4 kpc and Ω⊙ ≡ Ω0 + V⊙/R0=30.7±0.8 km s−1 kpc−1, and also show that the rotation curve of the Galaxy is nearly flat. The determinations of Galactic parameters and structures demonstrate that the maser astrometry can not only contribute significantly to research of individual maser sources, but also to studies of the structure of the Galaxy.

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