scholarly journals The origin of mass segregation in NGC 3603

2009 ◽  
Vol 5 (S266) ◽  
pp. 24-28
Author(s):  
Xiaoying Pang ◽  
Eva K. Grebel ◽  
Martin Altmann
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Young Star ◽  
Wide Field ◽  
Imaging Data ◽  
Kinematic Data ◽  
Cluster Membership ◽  
Deep Imaging ◽  
Mass Segregation ◽  
Young Star Clusters

AbstractNGC 3603 is one of the most massive, compact young star clusters in the Milky Way. The cluster has an age of only about 1 Myr and is embedded in a giant molecular cloud with ongoing star formation. We have analyzed deep imaging data obtained with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. We have obtained two epochs separated by 10 years, from which we derived proper motions which we used to determine cluster membership. After the removal of field stars, the resulting color–magnitude diagram shows a main sequence in addition to another clear sequence of pre-main-sequence stars. The cluster shows pronounced mass segregation and appears to have a very short crossing timescale. Our photometric, astrometric and kinematic data help us to evaluate the dissolution timescale of NGC 3603 and whether the mass segregation is likely to be primordial or evolutionary.

scholarly journals Spatial Structure of Star Clusters by the 2MASS Database

2001 ◽  
Vol 183 ◽  
pp. 331-332
Author(s):  
J.W. Chen ◽  
W.P. Chen
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Young Star ◽  
Open Clusters ◽  
Main Sequence Stars ◽  
Giant Stars ◽  
Sky Survey ◽  
Mass Segregation ◽  
Young Star Clusters

AbstractWe present some results of a pilot program to study star clusters with the Two-Micron All-Sky Survey (2MASS) observations. While 2MASS cannot resolve the cores or detect much of the main sequence of globular clusters, the homogeneity and large angular coverages make the database suitable to study young star clusters. We show that member stars are centrally concentrated in open clusters, with a density distribution markedly shallower than that for globular clusters. In NGC2506 (age 3 Gyr) giant stars appear to occupy a smaller region than main sequence stars—a natural consequence of mass segregation.

HII regions and young star clusters in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 207-208
Author(s):  
Myung Gyoon Lee
Keyword(s):  
Main Sequence ◽  
Star Clusters ◽  
Hii Regions ◽  
Young Star ◽  
Magellanic Clouds ◽  
Stellar Content ◽  
Ccd Photometry ◽  
Luminosity Functions ◽  
Young Star Clusters ◽  
Mass Functions

Using U BV CCD photometry, the stellar content of HII regions and young star clusters in the Magellanic Clouds has been studied: (1) the reddenings have been determined, and ages of OB associations and young star clusters have been measured; (2) the stellar initial mass functions have been determined by using the main-sequence luminosity functions; and (3) U BV CCD surface photometry of nine young star clusters has been obtained and their structural properties investigated.

scholarly journals Constraints on the spin-pole orientation, jet morphology, and rotation of interstellar comet 2I/Borisov with deep HST imaging

2020 ◽  
Vol 497 (4) ◽  
pp. 4031-4041
Author(s):  
Bryce T Bolin ◽  
Carey M Lisse
Keyword(s):  
Light Curve ◽  
Hubble Space Telescope ◽  
Wide Field ◽  
Deep Imaging ◽  
Projected Length ◽  
Before And After ◽  
Change Position ◽  
Time Frames ◽  
Pole Orientation ◽  
Perihelion Passage

ABSTRACT We present high resolution, deep imaging of interstellar comet 2I/Borisov taken with the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) on 2019 December 8 UTC and 2020 January 27 UTC (HST GO 16040, PI: Bolin) before and after its perihelion passage in combination with HST/WFC3 images taken on 2019 October 12 UTC and 2019 November 16 UTC (HST GO/DD 16009, PI: Jewitt) before its outburst and fragmentation of 2020 March, thus observing the comet in a relatively undisrupted state. We locate 1–2 arcsec long (2000–3000 km projected length) jet-like structures near the optocentre of 2I that appear to change position angles from epoch to epoch. With the assumption that the jet is located near the rotational pole supported by its stationary appearance on ∼10–100 h time frames in HST images, we determine that 2I’s pole points near α = 322 ± 10° and δ = 37 ± 10° (λ = 341° and β  = 48°) and may be in a simple rotation state. Additionally, we find evidence for possible periodicity in the HST time-series light curve on the time-scale of ∼5.3 h with a small amplitude of ∼0.05 mag implying a lower limit on its b/a ratio of ∼1.5 unlike the large ∼2 mag light curve observed for 1I/‘Oumuamua. However, these small light-curve variations may not be the result of the rotation of 2I’s nucleus due to its dust-dominated light-scattering cross-section. Therefore, uniquely constraining the pre-Solar system encounter, pre-outburst rotation state of 2I may not be possible even with the resolution and sensitivity provided by HST observations.

scholarly journals Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud – IV. Evidence for multiple populations in Hodge 11 and NGC 2210

2019 ◽  
Vol 486 (4) ◽  
pp. 5581-5599 ◽  
Author(s):  
Christina K Gilligan ◽  
Brian Chaboyer ◽  
Jeffrey D Cummings ◽  
Dougal Mackey ◽  
Roger E Cohen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Wide Field ◽  
Horizontal Branch ◽  
Advanced Camera For Surveys

Abstract We present a multiple population search in two old Large Magellanic Cloud (LMC) Globular clusters, Hodge 11 and NGC 2210. This work uses data from the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope from programme GO-14164 in Cycle 23. Both of these clusters exhibit a broadened main sequence with the second population representing (20 ± ∼5) per cent for NGC 2210 and (30 ± ∼5) per cent for Hodge 11. In both clusters, the smaller population is redder than the primary population, suggesting CNO variations. Hodge 11 also displays a bluer second population in the horizontal branch, which is evidence for helium enhancement. However, even though NGC 2210 shows similarities to Hodge 11 in the main sequence, there does not appear to be a second population on NGC 2210’s horizontal branch. This is the first photometric evidence that ancient LMC Globular clusters exhibit multiple stellar populations.

scholarly journals Hubble Space Telescope photometry of multiple stellar populations in the inner parts of NGC 2419

2019 ◽  
Vol 624 ◽  
pp. A25 ◽  
Author(s):  
Søren S. Larsen ◽  
Holger Baumgardt ◽  
Nate Bastian ◽  
Svea Hernandez ◽  
Jean Brodie
Keyword(s):  
Hubble Space Telescope ◽  
Dynamical Evolution ◽  
Bimodal Distribution ◽  
Wide Field ◽  
Red Giants ◽  
Space Telescope ◽  
Deep Imaging ◽  
Central Regions ◽  
Average Rotation ◽  
The Difference

We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W–F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of ΔY ≃ 0.05, but the P2 stars exhibit a significant spread in He content and some may reach ΔY ≃ 0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances ([Mg/Fe] <  0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p ≃ 0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.

scholarly journals A Dynamical Origin for Early Mass Segregation in Young Star Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 41-45
Author(s):  
Steve McMillan ◽  
Enrico Vesperini ◽  
Simon Portegies Zwart
Keyword(s):  
Cluster Formation ◽  
Star Clusters ◽  
Young Star ◽  
Mass Segregation ◽  
Young Star Clusters ◽  
Dynamical Origin ◽  
Significant Mass

AbstractSome young star clusters show a degree of mass segregation that is inconsistent with the effects of standard two-body relaxation from an initially unsegregated system without substructure, in virial equilibrium, and it is unclear whether current cluster formation models can account for this degree of initial segregation in clusters of significant mass. We show that mergers of small clumps that are either initially mass segregated, or in which mass segregation can be produced by two-body relaxation before they merge, generically lead to larger systems which inherit the progenitor clumps' segregation. We conclude that clusters formed in this way are naturally mass segregated, accounting for the anomalous observations and suggesting that this process of prompt mass segregation due to initial clumping should be taken into account in models of cluster formation and dynamics.

scholarly journals The Mass Function of Young Star Clusters in our Galaxy and Nearby Galaxies: Is It Universal?

2002 ◽  
Vol 207 ◽  
pp. 515-524
Author(s):  
Ram Sagar
Keyword(s):  
Star Clusters ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Young Star ◽  
Initial Mass Function ◽  
Galactocentric Distance ◽  
Photometric Observations ◽  
Nearby Galaxies ◽  
Mass Segregation ◽  
Young Star Clusters

Mass functions (MFs) derived from photometric observations of young star clusters of our Galaxy, the Magellanic Clouds (MCs), M31 and M33 have been used to investigate the question of universality of the initial mass function and presence of mass segregation in these systems. Observational determination of the MF slope of young star clusters have an inherent uncertainty of at least ∼ 1.0 dex in the Milky Way and of ∼ 0.4 dex in the MCs. There is no obvious dependence of the MF slope on either galactocentric distance or age of the young star clusters or on the spatial concentration of the stars formed or on the galactic characteristics including metallicity. Effects of mass segregation have been observed in a good number of young stellar groups of our Galaxy and MCs. As their ages are much smaller than their dynamical evolution times, star formation processes seem to be responsible for the observed mass segregation in them.

scholarly journals Comparisons between observational color-magnitude diagrams and synthetic cluster diagrams for young star clusters in the Magellanic Clouds

1984 ◽  
Vol 105 ◽  
pp. 83-87
Author(s):  
Stephen A. Becker ◽  
Grant J. Mathews ◽  
Wendee M. Brunish
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Star Clusters ◽  
Theoretical Models ◽  
Young Star ◽  
Asymptotic Giant Branch ◽  
Current Status ◽  
Large Numbers ◽  
Young Star Clusters ◽  
Convective Overshoot

Young star clusters (<3 × 108 yr) in the Maqellanic Clouds (MC) can be used to test the current status of the theory of stellar evolution as applied to intermediate and massive stars. The color-magnitude diagram of many young clusters in the MC shows, unlike the case of clusters in our Galaxy, large numbers of stars in both the main sequence and post main sequence evolutionary phases. Usina a arid of stellar evolution models, synthetic cluster H-R diagrams are constructed and compared to observed color-magnitude diagrams to determine the age, age spread, and composition for any given cluster. In addition, for those cases where the data is of high quality, detailed comparisons between theory and observation can provide a diagnostic of the accuracy of the stellar evolution models. Initial indications of these comparisons suggest that the theoretical models should be altered to include: a larger value for the mixing length parameter (α), a larger rate of mass loss during the asymptotic giant branch (AGB) phase, and possibly convective overshoot during the core burning phases.

scholarly journals Rapid mass segregation in young star clusters without substructure?

2010 ◽  
Vol 6 (S271) ◽  
pp. 389-390
Author(s):  
C. Olczak ◽  
R. Spurzem ◽  
Th. Henning
Keyword(s):  
Initial Conditions ◽  
Star Clusters ◽  
Building Blocks ◽  
Young Star ◽  
Subsequent Formation ◽  
Multiple Systems ◽  
Mass Segregation ◽  
New Generation ◽  
The Impact ◽  
Young Star Clusters

AbstractThe young star clusters we observe today are the building blocks of a new generation of stars and planets in our Galaxy and beyond. Despite their fundamental role we still lack knowledge about the initial conditions under which star clusters form and the impact of these often harsh environments on the formation and evolution of their stellar and substellar members.We present recent results showing that mass segregation in realistic models of young star clusters occurs very quickly for subvirial spherical systems without substructure. This finding is a critical step to resolve the controversial debate on mass segregation in young star clusters and provides strong constraints on their initial conditions. The rapid concentration of massive stars is usually associated with strong gravitational interactions early on during cluster evolution and the subsequent formation of multiple systems and ejection of stars.

scholarly journals Head-to-Toe Measurement of El Gordo: Improved Analysis of the Galaxy Cluster ACT-CL J0102–4915 with New Wide-field Hubble Space Telescope Imaging Data

2021 ◽  
Vol 923 (1) ◽  
pp. 101
Author(s):  
Jinhyub Kim ◽  
M. James Jee ◽  
John P. Hughes ◽  
Mijin Yoon ◽  
Kim HyeongHan ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Galaxy Cluster ◽  
Wide Field ◽  
Mass Ratio ◽  
Imaging Data ◽  
Space Telescope ◽  
Strong Lensing ◽  
The Galaxy ◽  
The Masses ◽  
Best Fit

Abstract We present an improved weak-lensing (WL) study of the high-z (z = 0.87) merging galaxy cluster ACT-CL J0102–4915 (“El Gordo”) based on new wide-field Hubble Space Telescope imaging data. The new imaging data cover the ∼3.5 × ∼3.5 Mpc region centered on the cluster and enable us to detect WL signals beyond the virial radius, which was not possible in previous studies. We confirm the binary mass structure consisting of the northwestern (NW) and southeastern (SE) subclusters and the ∼2σ dissociation between the SE mass peak and the X-ray cool core. We obtain the mass estimates of the subclusters by simultaneously fitting two Navarro–Frenk–White (NFW) halos without employing mass–concentration relations. The masses are M 200 c NW = 9.9 − 2.2 + 2.1 × 1014 and M 200 c SE = 6.5 − 1.4 + 1.9 × 1014 M ⊙ for the NW and SE subclusters, respectively. The mass ratio is consistent with our previous WL study but significantly different from the previous strong-lensing results. This discrepancy is attributed to the use of extrapolation in strong-lensing studies because the SE component possesses a higher concentration. By superposing the two best-fit NFW halos, we determine the total mass of El Gordo to be M 200 c = 2.13 − 0.23 + 0.25 × 1015 M ⊙, which is ∼23% lower than our previous WL result [M 200c = (2.76 ± 0.51) × 1015 M ⊙]. Our updated mass is a more direct measurement, since we are not extrapolating to R 200c as in all previous studies. The new mass is compatible with the current ΛCDM cosmology.

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