scholarly journals Stellar dynamics in the Galactic Centre: proper motions and anisotropy

2000 ◽  
Vol 317 (2) ◽  
pp. 348-374 ◽  
Author(s):  
R. Genzel ◽  
C. Pichon ◽  
A. Eckart ◽  
O. E. Gerhard ◽  
T. Ott
Keyword(s):  
Stellar Dynamics ◽  
Galactic Centre ◽  
Proper Motions

scholarly journals 2D kinematics of massive stars near the Galactic Centre

2020 ◽  
Vol 500 (3) ◽  
pp. 3213-3239
Author(s):  
Mattia Libralato ◽  
Daniel J Lennon ◽  
Andrea Bellini ◽  
Roeland van der Marel ◽  
Simon J Clark ◽  
...  
Keyword(s):  
Moving Objects ◽  
Hubble Space Telescope ◽  
Massive Stars ◽  
Line Of Sight ◽  
Galactic Centre ◽  
Harsh Environment ◽  
Proper Motions ◽  
Sgr A ◽  
Better Than ◽  
Rule Out

ABSTRACT The presence of massive stars (MSs) in the region close to the Galactic Centre (GC) poses several questions about their origin. The harsh environment of the GC favours specific formation scenarios, each of which should imprint characteristic kinematic features on the MSs. We present a 2D kinematic analysis of MSs in a GC region surrounding Sgr A* based on high-precision proper motions obtained with the Hubble Space Telescope. Thanks to a careful data reduction, well-measured bright stars in our proper-motion catalogues have errors better than 0.5 mas yr−1. We discuss the absolute motion of the MSs in the field and their motion relative to Sgr A*, the Arches, and the Quintuplet. For the majority of the MSs, we rule out any distance further than 3–4 kpc from Sgr A* using only kinematic arguments. If their membership to the GC is confirmed, most of the isolated MSs are likely not associated with either the Arches or Quintuplet clusters or Sgr A*. Only a few MSs have proper motions, suggesting that they are likely members of the Arches cluster, in agreement with previous spectroscopic results. Line-of-sight radial velocities and distances are required to shed further light on the origin of most of these massive objects. We also present an analysis of other fast-moving objects in the GC region, finding no clear excess of high-velocity escaping stars. We make our astro-photometric catalogues publicly available.

scholarly journals Transverse kinematics of the Galactic bar-bulge from VVV and Gaia

2019 ◽  
Vol 487 (4) ◽  
pp. 5188-5208 ◽  
Author(s):  
Jason L Sanders ◽  
Leigh Smith ◽  
N Wyn Evans ◽  
Philip Lucas
Keyword(s):  
Near Infrared ◽  
Transverse Velocity ◽  
Absolute Calibration ◽  
Galactic Centre ◽  
Proper Motions ◽  
Low Latitude ◽  
Magnitude Distribution ◽  
Double Peaks ◽  
Public Survey ◽  
Survey Results

ABSTRACT We analyse the kinematics of the Galactic bar-bulge using proper motions from the ESO public survey Vista Variables in the Via Lactea (VVV) and the second Gaia data release. Gaia has provided some of the first absolute proper motions within the bulge and the near-infrared VVV multi-epoch catalogue complements Gaia in highly extincted low-latitude regions. We discuss the relative-to-absolute calibration of the VVV proper motions using Gaia. Along lines of sight spanning $-10\lt \ell /\, \mathrm{deg}\lt 10$ and $-10\lt b/\, \mathrm{deg}\lt 5$, we probabilistically model the density and velocity distributions as a function of distance of ∼45 million stars. The transverse velocities confirm the rotation signature of the bar seen in spectroscopic surveys. The differential rotation between the double peaks of the magnitude distribution confirms the X-shaped nature of the bar-bulge. Both transverse velocity components increase smoothly along the near side of the bar towards the Galactic Centre, peak at the Galactic Centre, and decline on the far side. The anisotropy is σℓ/σb ≈ 1.1–1.3 within the bulk of the bar, reducing to 0.9–1.1 when rotational broadening is accounted for, and exhibits a clear X-shaped signature. The vertex deviation in ℓ and b is significant |ρℓb| ≲ 0.2, greater on the near side of the bar and produces a quadrupole signature across the bulge indicating approximate radial alignment. We have re-constructed the 3D kinematics from the assumption of triaxiality, finding good agreement with spectroscopic survey results. In the co-rotating frame, we find evidence of bar-supporting x1 orbits and tangential bias in the in-plane dispersion field.

scholarly journals Proper motion measurements for stars up to 100 kpc with Subaru HSC and SDSS Stripe 82

2020 ◽  
Author(s):  
Tian Qiu ◽  
Wenting Wang ◽  
Masahiro Takada ◽  
Naoki Yasuda ◽  
Željko Ivezić ◽  
...  
Keyword(s):  
Proper Motion ◽  
Tangential Velocity ◽  
Space Structures ◽  
Galactic Centre ◽  
Proper Motions ◽  
Distance Range ◽  
Common Reference ◽  
Motion Display ◽  
Motion Measurements ◽  
Set Up

Abstract We present proper motion measurements for more than 0.55 million main-sequence stars, by comparing astrometric positions of matched stars between the multi-band imaging datasets from the Hyper Suprime-Cam (HSC) Survey and the SDSS Stripe 82. In doing this we use 3 million galaxies to recalibrate the astrometry and set up a common reference frame between the two catalogues. The exquisite depth and the nearly 12 years of time baseline between HSC and SDSS enable high-precision measurements of statistical proper motions for stars down to i ≃ 24. A validation of our method is demonstrated by the agreement with the Gaia proper motions, to the precision better than 0.1 mas yr−1. To retain the precision, we make a correction of the subtle effects due to the differential chromatic refraction in the SDSS images based on the comparison with the Gaia proper motions against colour of stars, which is validated using the SDSS spectroscopic quasars. Combining with the photometric distance estimates for individual stars based on the precise HSC photometry, we show a significant detection of the net proper motions for stars in each bin of distance out to 100 kpc. The two-component tangential velocities after subtracting the apparent motions due to our own motion display rich phase-space structures including a clear signature of the Sagittarius stream in the halo region of distance range [10,35] kpc. We also measure the tangential velocity dispersion in the distance range 5–20 kpc and find that the data are consistent with a constant isotropic dispersion of 80 ± 10 km/s. More distant stars appear to have random motions with respect to the Galactic centre on average.

scholarly journals Structure and Kinematical Properties of the Galaxy at Intermediate Galactic Latitudes

1998 ◽  
Vol 179 ◽  
pp. 221-222
Author(s):  
D. K. Ojha ◽  
O. Bienaymé ◽  
A. C. Robin
Keyword(s):  
Vertical Structure ◽  
Local Density ◽  
Thick Disk ◽  
Sample Survey ◽  
Galactic Centre ◽  
Proper Motions ◽  
Perfect Agreement ◽  
The Galaxy ◽  
Centre Region ◽  
Disk Component

We have carried out a sample survey in UBVR photometry and proper motions in various directions in the Galaxy. Three fields in the direction of galactic anticentre, centre, and antirotation have been surveyed. Using our new data together with wide-area surveys in other fields available to date, we discuss the radial and vertical structure of the Galaxy. Our results confirm that the thick disk population is distinct from other populations based on their kinematical and spatial distribution. The most probable value of scale height for the thick disk component is determined to be hz≃760±50 pc and a local density of ≃7.4+2.5−1.5% relative to the thin disk. The ratio of the number of thick disk stars in our galactic centre region to that in anticentre region yield hR≃3±1 kpc for the scale length of thick disk. These values are in perfect agreement with the recent determination given by Robin et al. (1996).

scholarly journals GaiaNIR – A future all-sky astrometry mission

2017 ◽  
Vol 12 (S330) ◽  
pp. 67-70
Author(s):  
David Hobbs ◽  
Erik Høg
Keyword(s):  
Interstellar Extinction ◽  
Galactic Centre ◽  
Proper Motions ◽  
New Era ◽  
New Science ◽  
Technical Issues ◽  
Optical Wavelengths ◽  
Space Astrometry ◽  
Opening Up ◽  
Spiral Arm

AbstractWith the launch of Gaia in December 2013, Europe entered a new era of space astrometry following in the footsteps of the very successful Hipparcos mission. A weakness of Gaia is that it only operates at optical wavelengths. However, much of the Galactic centre and the spiral arm regions are obscured by interstellar extinction. An obvious improvement on Gaia is to include the Near-Infra-Red (NIR) which requires the use of new types of detectors. Additionally, to scan the entire sky and measure global absolute parallaxes the spacecraft must have a constant rotation resulting in a moving image that must be compensated for by, for example, operating the detectors in Time Delayed Integration (TDI) mode. If these technical issues can be solved a new Gaia-like mission separated by a 20 year interval would give; 1) NIR all-sky astrometry and photometry to penetrate the obscured regions and to observe intrinsically red objects with almost diffraction limited resolution; 2) improved proper motions with fourteen times smaller errors than from Gaia alone opening up new science cases, such as long period exoplanets and accurate halo measurements; 3) allow the slowly degrading accuracy of the Gaia reference frame, which will be the basis for future astronomical measurements, to be reset.

Proper Motions in the Field of the Open Cluster NGC 6475 (M 7)

1969 ◽  
Vol 1 (5) ◽  
pp. 207-208 ◽  
Author(s):  
Susan M. Constantine ◽  
B. J. Harris ◽  
I. Nikoloff
Keyword(s):  
Open Cluster ◽  
Galactic Centre ◽  
Proper Motions ◽  
Naked Eye

The naked-eye cluster, Messier 7, is situated in the constellation of Scorpius, south of the great Sagittarius star clouds, and close to the galactic centre.

scholarly journals Hubble Space Telescope Proper Motions and Stellar Dynamics in the Core of the Globular Cluster 47 Tucanae

2006 ◽  
Vol 166 (1) ◽  
pp. 249-297 ◽  
Author(s):  
Dean E. McLaughlin ◽  
Jay Anderson ◽  
Georges Meylan ◽  
Karl Gebhardt ◽  
Carlton Pryor ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Hubble Space Telescope ◽  
Stellar Dynamics ◽  
Proper Motions ◽  
Space Telescope ◽  
The Core

scholarly journals The distribution of stars around the Milky Way’s central black hole

2017 ◽  
Vol 609 ◽  
pp. A28 ◽  
Author(s):  
H. Baumgardt ◽  
P. Amaro-Seoane ◽  
R. Schödel
Keyword(s):  
Black Hole ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Stellar Dynamics ◽  
Galactic Centre ◽  
Test Case ◽  
Central Black Hole ◽  
Massive Black Hole ◽  
Giant Stars ◽  
Sgr A

Context. The distribution of stars around a massive black hole (MBH) has been addressed in stellar dynamics for the last four decades by a number of authors. Because of its proximity, the centre of the Milky Way is the only observational test case where the stellar distribution can be accurately tested. Past observational work indicated that the brightest giants in the Galactic centre (GC) may show a density deficit around the central black hole, not a cusp-like distribution, while we theoretically expect the presence of a stellar cusp. Aims. We here present a solution to this long-standing problem. Methods. We performed direct-summation N-body simulations of star clusters around massive black holes and compared the results of our simulations with new observational data of the GC’s nuclear cluster. Results. We find that after a Hubble time, the distribution of bright stars as well as the diffuse light follow power-law distributions in projection with slopes of Γ ≈ 0.3 in our simulations. This is in excellent agreement with what is seen in star counts and in the distribution of the diffuse stellar light extracted from adaptive-optics (AO) assisted near-infrared observations of the GC. Conclusions. Our simulations also confirm that there exists a missing giant star population within a projected radius of a few arcsec around Sgr A*. Such a depletion of giant stars in the innermost 0.1 pc could be explained by a previously present gaseous disc and collisions, which means that a stellar cusp would also be present at the innermost radii, but in the form of degenerate compact cores.

scholarly journals First results from a large-scale proper motion study of the Galactic centre

2019 ◽  
Vol 632 ◽  
pp. A116 ◽  
Author(s):  
B. Shahzamanian ◽  
R. Schödel ◽  
F. Nogueras-Lara ◽  
H. Dong ◽  
E. Gallego-Cano ◽  
...  
Keyword(s):  
Proper Motion ◽  
Large Scale ◽  
Interstellar Extinction ◽  
Stellar Disk ◽  
Galactic Centre ◽  
Proper Motions ◽  
Stellar Cluster ◽  
Motion Study ◽  
First Results ◽  
Moving Groups

Proper motion studies of stars in the centre of the Milky Way have typically been limited to the Arches and Quintuplet clusters, and to the central parsec. Here we present the first results of a large-scale proper motion study of stars within several tens of parsecs of Sagittarius A* based on our 0.2″ angular resolution GALACTICNUCLEUS survey (epoch 2015) combined with NICMOS/HST data from the Paschen-α survey (epoch 2008). This comprises the first extensive proper motion study of the central ∼36′×16′ of the Galaxy, which is not covered adequately by any of the existing astronomical surveys, such as Gaia, because of the extreme interstellar extinction (AV ≳ 30 mag). Proper motions can help us to disentangle the different stellar populations along the line-of-sight and interpret their properties in combination with multi-wavelength photometry from GALACTICNUCLEUS and other sources. It also allows us to infer the dynamics and interrelationships between different stellar components (Galactic bulge, nuclear stellar disk, nuclear stellar cluster) of the Galactic centre (GC). In particular, we use proper motions to detect co-moving groups of stars which are able to trace low-mass or partially-dissolved young clusters in the GC that can hardly be discovered by any other means. Our pilot study for this work is based on a field in the nuclear bulge associated with HII regions that show the presence of young stars. We have detected the first group of co-moving stars coincident with an H II region. Using colour–magnitude diagrams, we have inferred that the co-moving stars are consistent with the post-main sequence stars with ages of few Myr. Simulations show that this group of stars is a real group that can indicate the existence of a dissolving or low-to-intermediate-mass young cluster. A census of these undiscovered clusters will ultimately help us to constrain star formation at the GC in the past few ten Myr.

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