scholarly journals The Stellar Cluster

1989 ◽  
Vol 136 ◽  
pp. 477-486 ◽  
Author(s):  
K. Sellgren
Keyword(s):  
Mass Distribution ◽  
Total Mass ◽  
Galactic Center ◽  
Current Debate ◽  
Core Radius ◽  
Stellar Cluster ◽  
Mass Distributions ◽  
The Core ◽  
Gas Kinematics ◽  
The Galaxy

Observations of the stellar cluster in the central 10 pc of the Galaxy are reviewed. The stellar density law derived from the observed light distribution and the effects on this density law of variable extinction, the possibility of a varying mass-to-light ratio, and the current debate as to the core radius of the cluster are all important for establishing the true mass distribution of the stellar cluster. The presence of the supergiant IRS 7 in the Galactic Center establishes that some recent star formation has occurred, but the age and extent of a possible starburst are still being established. The kinematics of the stellar cluster show predominantly velocity dispersion, in contrast to the systematic gas motion observed, yet the total mass distributions derived from stellar and gas kinematics agree reasonably well. The core radius of the cluster is critical to establishing whether or not a central dark mass is required to explain the total mass distribution.

scholarly journals The Mass Distribution in the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 501-501
Author(s):  
M. T. McGinn ◽  
K. Sellgren ◽  
E. E. Becklin ◽  
D. N. B. Hall
Keyword(s):  
Mass Distribution ◽  
Galactic Center ◽  
Major Constituent ◽  
Galactic Rotation ◽  
Core Radius ◽  
Central Mass ◽  
Stellar Cluster ◽  
The Galaxy ◽  
Stellar Velocity ◽  
Best Fitting

We present the results of a project to map the profile of the 2.3 μm CO V = 2–0 band-head in the integrated starlight in the central 10 pc of the Galaxy. This is the first detailed determination of the kinematics of the faint stars that are the major constituent of the mass of the stellar cluster. The stars exhibit systematic rotation in the same sense as Galactic rotation, with VLSR increasing with Galactocentric radius. The stellar velocity dispersion generally dominates the rotation and shows clear evidence for a radial gradient, in the sense of σ decreasing with Galactocentric radius. The data are consistent with the dynamical center of the Galaxy being located at IRS 16 (to an accuracy of ± 10″). The mass distribution has been derived via the theory of stellar hydrodynamics and is shown in Fig. 1. For an assumed core radius of 10″ (~0.4 pc), the best fitting model is a combination of a central mass of 2.5 × 106 M⊙ and a stellar cluster with a density dependence of r-2.1 (Fig. 1). If the core radius is small (~1″) then the mass distribution could be just due to a stellar cluster; a central condensed mass is not required to model the data in that case.

scholarly journals Reconsideration of mass-distribution models

2014 ◽  
pp. 23-28
Author(s):  
S. Ninkovic
Keyword(s):  
Mass Distribution ◽  
Mass Fraction ◽  
Total Mass ◽  
Density Ratio ◽  
Distribution Model ◽  
Extended Model ◽  
Core Radius ◽  
Distribution Models ◽  
The Core ◽  
Fraction Versus

The mass-distribution model proposed by Kuzmin and Veltmann (1973) is revisited. It is subdivided into two models which have a common case. Only one of them is subject of the present study. The study is focused on the relation between the density ratio (the central one to that corresponding to the core radius) and the total-mass fraction within the core radius. The latter one is an increasing function of the former one, but it cannot exceed one quarter, which takes place when the density ratio tends to infinity. Therefore, the model is extended by representing the density as a sum of two components. The extension results into possibility of having a correspondence between the infinite density ratio and 100% total-mass fraction. The number of parameters in the extended model exceeds that of the original model. Due to this, in the extended model, the correspondence between the density ratio and total-mass fraction is no longer one-to-one; several values of the total-mass fraction can correspond to the same value for the density ratio. In this way, the extended model could explain the contingency of having two, or more, groups of real stellar systems (subsystems) in the diagram total-mass fraction versus density ratio.

scholarly journals Constraining the abundance of dark matter in the central region of the galaxy cluster MACS J1206.2−0847 with a free-form strong lensing analysis

2020 ◽  
Vol 639 ◽  
pp. A125
Author(s):  
Alberto Manjón-García ◽  
Jose M. Diego ◽  
Diego Herranz ◽  
Daniel Lam
Keyword(s):  
Dark Matter ◽  
Mass Distribution ◽  
Central Region ◽  
Total Mass ◽  
Galaxy Cluster ◽  
Free Form ◽  
Matter Distribution ◽  
Strong Lensing ◽  
The Galaxy ◽  
Dark Matter Distribution

We performed a free-form strong lensing analysis of the galaxy cluster MACS J1206.2−0847 in order to estimate and constrain its inner dark matter distribution. The free-form method estimates the cluster total mass distribution without using any prior information about the underlying mass. We used 97 multiple lensed images belonging to 27 background sources and derived several models, which are consistent with the data. Among these models, we focus on those that better reproduce the radial images that are closest to the centre of the cluster. These radial images are the best probes of the dark matter distribution in the central region and constrain the mass distribution down to distances ∼7 kpc from the centre. We find that the morphology of the innermost radial arcs is due to the elongated morphology of the dark matter halo. We estimate the stellar mass contribution of the brightest cluster galaxy and subtracted it from the total mass in order to quantify the amount of dark matter in the central region. We fitted the derived dark matter density profile with a gNFW, which is characterised by rs = 167 kpc, ρs = 6.7 × 106 M⊙ kpc−3, and γgNFW = 0.70. These results are consistent with a dynamically relaxed cluster. This inner slope is smaller than the cannonical γ = 1 predicted by standard CDM models. This slope does not favour self-interacting models for which a shallower slope would be expected.

Planetesimal Capture by an Evolving Giant Gaseous Protoplanet

2012 ◽  
Vol 8 (S293) ◽  
pp. 263-269
Author(s):  
Morris Podolak ◽  
Nader Haghighipour
Keyword(s):  
Mass Distribution ◽  
Total Mass ◽  
Size Composition ◽  
Giant Planets ◽  
The Core ◽  
Last Stage ◽  
Core Accretion ◽  
Gaseous Envelope ◽  
Gas Drag ◽  
Probability Of Capture

AbstractBoth the core-accretion and disk-instability models suggest that at the last stage of the formation of a gas-giant, the core of this object is surrounded by an extended gaseous envelope. At this stage, while the envelope is contracting, planetesimals from the protoplanetary disk may be scattered into the protoplanets atmosphere and deposit some or all of their materials as they interact with the gas. We have carried out extensive simulations of approximately 104 planetesimals interacting with a envelope of a Jupiter-mass protoplanet including effects of gas drag, heating, and the effect of the protoplanets extended mass distribution. Simulations have been carried out for different radii and compositions of planetesimals so that all three processes occur to different degrees. We present the results of our simulations and discuss their implications for the enrichment of ices in giant planets. We also present statistics for the probability of capture (i.e. total mass-deposition) of planetesimals as a function of their size, composition, and closest approach to the center of the protoplanetary body.

The Rotation Curve from A-F Supergiants

1996 ◽  
Vol 169 ◽  
pp. 703-706
Author(s):  
D. M. Peterson ◽  
D. Slowik
Keyword(s):  
Total Mass ◽  
Rotation Curve ◽  
Galactic Center ◽  
Galactic Rotation ◽  
The Sun ◽  
Critical Information ◽  
New Class ◽  
The Galaxy ◽  
Local Distance

The Galactic rotation law provides critical information for estimating the distribution of mass in the Galaxy, for tying the distance of the Sun from the Galactic center to local distance scales, and, if determined over large enough distances, for estimating the total mass of the system and the amount of nonluminous matter present. Interior to the Sun velocities are well defined by observations of the ISM, particularly HI. These techniques are not available for points exterior to the Sun and we must rely on observations of velocities of objects whose distances can be estimated. Notable among these are the Cepheids (Pont et al 1994) and the combination of CO velocities and OB cluster distances (Brand & Blitz 1993) where the two are found to coexist. Adding a new class of objects, particularly bright, relatively common objects to this effort is of importance.

scholarly journals Agricultural tractor traction efficiency by changing the mass distribution between axles and speed

2021 ◽  
Vol 25 (4) ◽  
pp. 277-281
Author(s):  
Lauro Strapasson Neto ◽  
Maíra Laskoski ◽  
Samir P. Jasper ◽  
Gabriéle S. de Campos ◽  
Leonardo L. Kmiecik ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Total Mass ◽  
Rear Axle ◽  
Block Design ◽  
Front Axle ◽  
Mass Distributions ◽  
Tukey Test ◽  
Randomized Block Design ◽  
Displacement Speed ◽  
Agricultural Tractor

ABSTRACT The traction efficiency of the agricultural tractor can be maximized by adjusting the total mass and its distribution between the axles. The experiment’s objective was to determine the configuration of mass distribution between axles and the displacement speed that provides greater traction efficiency in the harrowing operation. A randomized block design in a 2 × 3 factorial scheme with five replications was used. The first factor was two mass distributions between axles, and the second factor was three gears. The collected data were submitted to analysis of variance and the Tukey test. The condition that maximizes the tractor’s performance corresponds to 39% of the total mass on the front axle and 61% on the rear axle, with a gear that provides speed close to 10 km h-1.

scholarly journals X-ray Detection of the Nuclear Source in the Cygnus a Galaxy

1994 ◽  
Vol 159 ◽  
pp. 375-376
Author(s):  
D.E. Harris ◽  
R.A. Perley ◽  
C.L. Carilli
Keyword(s):  
Image Processing ◽  
Surface Brightness ◽  
Main Body ◽  
Core Radius ◽  
Gas Distribution ◽  
Model Surface ◽  
X Ray ◽  
The Core ◽  
Cygnus A ◽  
The Galaxy

From a ROSAT HRI observation of Cygnus A (42 ksec), we detect x-ray emission from the galaxy identified with the radio source. This was accomplished by subtracting a modified King model: (Surface brightness ∝ to [1+(r/a)2](0.5–3β)) in order to study residual features once the main body of emission from diffuse gas had been deleted. The central source was present for all acceptable values of the core radius, a, and exponent, β. Details of the image processing, an evaluation of emission from the radio hotspots, and a study of the effect of the radio lobes on the gas distribution will be presented elsewhere.

scholarly journals Dynamical interpretations of the galactic center region

1979 ◽  
Vol 84 ◽  
pp. 383-392 ◽  
Author(s):  
Robert H. Sanders
Keyword(s):  
Mass Distribution ◽  
Central Region ◽  
Galactic Center ◽  
List Type ◽  
Type Number ◽  
Center Region ◽  
The Galaxy

I will define the central region of the Galaxy as being the inner four kiloparsecs. The distinguishing characteristics of this region are: 1)The dominance of a central spheroidal component in the mass distribution – a bulge.2)An apparent deficiency of gas, at least between radii of 500 pc and 4000 pc.3)High non-circular gas velocities. Now let us consider these characteristics in some detail.

scholarly journals Mass distribution of the Galaxy with VERA

2012 ◽  
Vol 8 (S287) ◽  
pp. 421-422
Author(s):  
Nobuyuki Sakai ◽  
Mareki Honma ◽  
Hiroyuki Nakanishi ◽  
Hirofumi Sakanoue ◽  
Tomoharu Kurayama ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Rotation Curve ◽  
Galactic Center ◽  
Rotation Velocity ◽  
Galactic Rotation ◽  
Proper Motions ◽  
Systemic Velocity ◽  
The Galaxy ◽  
Peculiar Motion ◽  
Perseus Arm

AbstractWe aim to reveal the mass distribution of the Galaxy based on a precise rotation curve constructed using VERA observations. We have been observing Galactic H2O masers with VERA. We here report one of the results of VERA for IRAS 05168+3634. The parallax is 0.532 ± 0.053 mas which corresponds to a distance of 1.88+0.21−0.17 kpc, and the proper motions are (μαcosδ, μδ) = (0.23 ± 1.07, −3.14 ± 0.28) mas yr−1. The distance is significantly smaller than the previous distance estimate of 6 kpc based on a kinematic distance. This drastic change places the source in the Perseus arm rather than in the Outer arm. Combination of the distance and the proper motions with the systemic velocity provides a rotation velocity of 227+9−11 km s−1 at the source assuming Θ0 = 240 km s−1. The result is marginally slower than the rotation velocity at LSR with ~ 1−σ significance, but consistent with previous VLBI results for six sources in the Perseus arm. We also show the averaged disk peculiar motion over the seven sources in the Perseus arm as (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1. It suggests that the seven sources in the Perseus arm are systematically moving toward the Galactic center, and lag behind the Galactic rotation with more than 3-σ significance.

scholarly journals Cusp or core? Revisiting the globular cluster timing problem in Fornax

2019 ◽  
Vol 491 (3) ◽  
pp. 3336-3342 ◽  
Author(s):  
Noah Meadows ◽  
Julio F Navarro ◽  
Isabel Santos-Santos ◽  
Alejandro Benítez-Llambay ◽  
Carlos Frenk
Keyword(s):  
Spatial Distribution ◽  
Globular Cluster ◽  
Total Mass ◽  
Effective Radius ◽  
Constant Density ◽  
Core Radius ◽  
Dynamical Friction ◽  
The Core ◽  
Spatially Extended ◽  
Projected Distance

ABSTRACT We use N-body simulations to revisit the globular cluster (GC) ‘timing problem’ in the Fornax dwarf spheroidal (dSph). In agreement with earlier work, we find that, due to dynamical friction, GCs sink to the centre of dark matter haloes with a cuspy inner density profile but ‘stall’ at roughly 1/3 of the core radius (rcore) in haloes with constant-density cores. The time-scales to sink or stall depend strongly on the mass of the GC and on the initial orbital radius, but are essentially the same for either cuspy (Navarro–Frenk–White) or cored haloes normalized to have the same total mass within rcore. Arguing against a cusp on the basis that GCs have not sunk to the centre is thus no different from arguing against a core, unless all clusters are today at $\sim(1/3)\,r_{\rm core}$. This would imply a core radius exceeding ∼3 kpc, much larger than seems plausible in any core-formation scenario. (The average projected distance of Fornax GCs is 〈RGC, Fnx〉 ∼ 1 kpc and its effective radius is ∼700 pc.) A simpler explanation is that Fornax GCs have only been modestly affected by dynamical friction, as expected if clusters started orbiting at initial radii of the order of ∼1–2 kpc, just outside Fornax’s present-day half-light radius but well within the tidal radius imprinted by Galactic tides. This is not entirely unexpected. Fornax GCs are significantly older and more metal-poor than most Fornax stars, and such populations in dSphs tend to be more spatially extended than their younger and more metal-rich counterparts. Contrary to some earlier claims, our simulations further suggest that GCs do not truly ‘stall’ at $\sim 0.3\, r_{\rm core}$, but rather continue decaying towards the centre, albeit at reduced rates. We conclude that dismissing the presence of a cusp in Fornax based on the spatial distribution of its GC population is unwarranted.

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