scholarly journals Infrared Imaging of the Arches Cluster - Adaptive Optics in the Densest Region of the Milky Way

2002 ◽  
Vol 207 ◽  
pp. 132-134
Author(s):  
Andrea Stolte ◽  
Eva K. Grebel ◽  
Wolfgang Brandner ◽  
Donald F. Figer
Keyword(s):  
Adaptive Optics ◽  
Milky Way ◽  
Infrared Imaging ◽  
Galactic Center ◽  
Cluster Formation ◽  
Extreme Environment ◽  
Mass Function ◽  
Cluster Center ◽  
Limiting Factor ◽  
Dense Cluster

The Arches cluster - located only 11′ from the Galactic Center (GC) - is one of the densest and richest young star clusters in the Milky Way. With an age of only about 2 Myr, it is ideally suited to study massive cluster formation in an extreme environment. We find an IMF slope of Γ = −0.77 from 5 to 100 M⊙, in good agreement with the results from HST/NICMOS from Figer et al. (1999). The limiting factor in the dense cluster center is crowding. With the new AO systems, high resolution analysis of the dense cluster region combined with very deep infrared photometry is available. We have analysed deep H and K′ images of the cluster center obtained with the GEMINI/Hokupa'a adaptive optics system. Colour-magnitude diagrams and the IMF are constructed from these data. A comparison with isochrones yields the mass function.

scholarly journals Proper-motion studies of Milky Way starburst clusters – a new definition of starburst cluster templates

2009 ◽  
Vol 5 (S266) ◽  
pp. 123-128
Author(s):  
Andrea Stolte ◽  
Wolfgang Brandner
Keyword(s):  
Adaptive Optics ◽  
Proper Motion ◽  
Milky Way ◽  
Hubble Space Telescope ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Galactic Centre ◽  
Limiting Factor ◽  
Motion Studies

AbstractStarburst clusters in the Milky Way have the advantage that individual stars down to subsolar masses can be resolved. Thus far, field contamination along the line of sight towards the Galactic Centre and spiral arms was the limiting factor in deriving an unbiased census of the stellar population in Milky Way starbursts and, hence, the spatial extent and initial mass function in starburst clusters. As the next generation of telescopes with higher sensitivity and spatial resolution are being developed, these resolved clusters become increasingly important as templates for young, massive extragalactic systems, which will be resolved at the high-mass end of the stellar mass function. With the aim to obtain a uniform characterisation of starburst cluster properties in the Milky Way, we have initiated a proper-motion membership survey. This technique became feasible for clusters out to distances of 8 kpc with diffraction-limited imaging using adaptive optics from the ground and with Hubble Space Telescope from space.

scholarly journals Proper motions of thin filaments at the Galactic Center

2006 ◽  
Vol 2 (S238) ◽  
pp. 415-416
Author(s):  
K. Mužić ◽  
A. Eckart ◽  
R. Schödel ◽  
L. Meyer ◽  
A. Zensus
Keyword(s):  
Adaptive Optics ◽  
Milky Way ◽  
Galactic Center ◽  
Proper Motions ◽  
Thin Filaments ◽  
Motion Study ◽  
L Band ◽  
Central Parsec ◽  
Stellar Envelopes ◽  
Shock Fronts

AbstractWe present the proper motion study of the thin filaments observed in L'-band (3.8 μm) adaptive optics images of the central parsec of the Milky Way. Observed filaments are associated with the mini-spiral and, in some cases, with stars. They can be interpreted as shock fronts formed by the interaction of a central wind with the mini-spiral or extended dusty stellar envelopes.

scholarly journals Global survey of star clusters in the Milky Way

2018 ◽  
Vol 614 ◽  
pp. A22 ◽  
Author(s):  
A. E. Piskunov ◽  
A. Just ◽  
N. V. Kharchenko ◽  
P. Berczik ◽  
R.-D. Scholz ◽  
...  
Keyword(s):  
Milky Way ◽  
Cluster Formation ◽  
Formation Rate ◽  
Age Distribution ◽  
Star Clusters ◽  
Mass Function ◽  
Spatial Variations ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Formation History

Context. The all-sky Milky Way Star Clusters (MWSC) survey provides uniform and precise ages, along with other relevant parameters, for a wide variety of clusters in the extended solar neighbourhood. Aims. In this study we aim to construct the cluster age distribution, investigate its spatial variations, and discuss constraints on cluster formation scenarios of the Galactic disk during the last 5 Gyrs. Methods. Due to the spatial extent of the MWSC, we have considered spatial variations of the age distribution along galactocentric radius RG, and along Z-axis. For the analysis of the age distribution we used 2242 clusters, which all lie within roughly 2.5 kpc of the Sun. To connect the observed age distribution to the cluster formation history we built an analytical model based on simple assumptions on the cluster initial mass function and on the cluster mass-lifetime relation, fit it to the observations, and determined the parameters of the cluster formation law. Results. Comparison with the literature shows that earlier results strongly underestimated the number of evolved clusters with ages t ≳ 100 Myr. Recent studies based on all-sky catalogues agree better with our data, but still lack the oldest clusters with ages t ≳ 1 Gyr. We do not observe a strong variation in the age distribution along RG, though we find an enhanced fraction of older clusters (t > 1 Gyr) in the inner disk. In contrast, the distribution strongly varies along Z. The high altitude distribution practically does not contain clusters with t < 1 Gyr. With simple assumptions on the cluster formation history, the cluster initial mass function and the cluster lifetime we can reproduce the observations. The cluster formation rate and the cluster lifetime are strongly degenerate, which does not allow us to disentangle different formation scenarios. In all cases the cluster formation rate is strongly declining with time, and the cluster initial mass function is very shallow at the high mass end.

scholarly journals New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging

2020 ◽  
Vol 634 ◽  
pp. A71 ◽  
Author(s):  
E. Gallego-Cano ◽  
R. Schödel ◽  
F. Nogueras-Lara ◽  
H. Dong ◽  
B. Shahzamanian ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
3D Structure ◽  
Major Axis ◽  
Stellar Disk ◽  
Axis Ratio ◽  
Stellar Cluster ◽  
Red Clump

Context. The Milky Way nuclear star cluster (MWNSC) is a crucial laboratory for studying the galactic nuclei of other galaxies, but its properties have not been determined unambiguously until now. Aims. We aim to study the size and spatial structure of the MWNSC. Methods. This study uses data and methods that address potential shortcomings of previous studies on the topic. We use 0.2″ angular resolution Ks data to create a stellar density map in the central 86.4 pc × 21 pc at the Galactic center. We include data from selected adaptive-optics-assisted images obtained for the inner parsecs. In addition, we use Spitzer/IRAC mid-infrared (MIR) images. We model the Galactic bulge and the nuclear stellar disk in order to subtract them from the MWNSC. Finally, we fit a Sérsic model to the MWNSC and investigate its symmetry. Results. Our results are consistent with previous work. The MWNSC is flattened with an axis ratio of q = 0.71 ± 0.10, an effective radius of Re = (5.1 ± 1.0) pc, and a Sérsic index of n = 2.2 ± 0.7. Its major axis may be tilted out of the Galactic plane by up to −10°. The distribution of the giants brighter than the Red Clump (RC) is found to be significantly flatter than the distribution of the faint stars. We investigate the 3D structure of the central stellar cusp using our results on the MWNSC structure on large scales to constrain the deprojection of the measured stellar surface number density, obtaining a value of the 3D inner power law of γ = 1.38 ± 0.06sys ± 0.01stat. Conclusions. The MWNSC shares its main properties with other extragalactic NSCs found in spiral galaxies. The differences in the structure between bright giants and RC stars might be related to the existence of not completely mixed populations of different ages. This may hint at recent growth of the MWNSC through star formation or cluster accretion.

scholarly journals Constraining the Variability and Binary Fraction of Galactic Center Young Stars

2016 ◽  
Vol 11 (S322) ◽  
pp. 237-238
Author(s):  
Abhimat K. Gautam ◽  
Tuan Do ◽  
Andrea M. Ghez ◽  
Jessica R. Lu ◽  
Mark R. Morris ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Adaptive Optics ◽  
Binary Systems ◽  
Main Sequence ◽  
Milky Way ◽  
Galactic Center ◽  
Young Stars ◽  
Early Type ◽  
Eclipsing Binary ◽  
Early Type Stars

AbstractWe present constraints on the variability and binarity of young stars in the central 10 arcseconds (~ 0.4 pc) of the Milky Way Galactic Center (GC) using Keck Adaptive Optics data over a 12 year baseline. Given our experiment’s photometric uncertainties, at least 36% of our sample’s known early-type stars are variable. We identified eclipsing binary systems by searching for periodic variability. In our sample of spectroscopically confirmed and likely early-type stars, we detected the two previously discovered GC eclipsing binary systems. We derived the likely binary fraction of main sequence, early-type stars at the GC via Monte Carlo simulations of eclipsing binary systems, and find that it is at least 32% with 90% confidence.

scholarly journals Abundance patterns in stars in the bulge and Galactic center

2007 ◽  
Vol 3 (S245) ◽  
pp. 339-342 ◽  
Author(s):  
Katia Cunha ◽  
V. V. Smith ◽  
K. Sellgren ◽  
R. D. Blum ◽  
S. V. Ramírez ◽  
...  
Keyword(s):  
Milky Way ◽  
Galactic Center ◽  
Mass Function ◽  
Initial Mass Function ◽  
Red Giants ◽  
The Sun ◽  
Chemical Enrichment ◽  
Abundance Patterns ◽  
Iron Abundance ◽  
Red Giant

AbstractWe discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of α-elements relative to either the Sun or Milky Way disk at near-solar metallicities.

scholarly journals The structure of the nuclear stellar cluster of the Milky Way

2006 ◽  
Vol 2 (S238) ◽  
pp. 187-190
Author(s):  
Rainer Schödel ◽  
Andreas Eckart
Keyword(s):  
Adaptive Optics ◽  
Milky Way ◽  
Galactic Center ◽  
Interstellar Extinction ◽  
Intermediate Band ◽  
Stellar Cluster ◽  
Density Peaks ◽  
Mass Segregation ◽  
Sgr A ◽  
Number Counts

AbstractHigh-resolution adaptive optics observations of the inner 0.5 pc of the Milky Way with multiple intermediate band filters are presented. From the images, stellar number counts and a detailed map of the interstellar extinction were extracted. The extinction map is consistent with a putative southwest-northeast aligned outflow from the central arcseconds.An azimuthally averaged, crowding and extinction corrected stellar density profile presents clear evidence for the existence of a stellar cusp around Sgr A*. Several density peaks are found in the cluster that may indicate clumping of stars, possibly related to the last epoch of star formation in the Galactic Center. An analysis of stars in the brightness range 14.25 < magK < 15.75 shows possible signs of mass segregation.

Dynamical effects on the stellar mass function of multiple stellar populations in globular clusters

2019 ◽  
Vol 14 (S351) ◽  
pp. 346-349
Author(s):  
Enrico Vesperini ◽  
Jongsuk Hong ◽  
Jeremy J. Webb ◽  
Franca D’Antona ◽  
Annibale D’Ercole
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Cluster Formation ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Stellar Mass ◽  
Initial Mass Function ◽  
Cluster Center ◽  
Mixing Rate ◽  
Multiple Population

AbstractWe present a brief summary of the results of a study of the effects of dynamical evolution on the stellar mass function of multiple-population globular clusters. Theoretical studies have predicted that the process of multiple-population cluster formation results in a system in which second-generation (2G) stars are initially more centrally concentrated than first-generation (1G) stars. In the study presented here, we have explored the implications of the initial differences between the 2G and 1G structural properties for the evolution of the local (measured at different distances from a cluster center) and global mass function. We have studied both systems in which 1G and 2G stars start with the same initial mass function (IMF) and systems in which 1G and 2G stars have different IMFs. Finally we have explored the evolution of the spatial mixing and found that the multiscale nature of the clusters studied leads to a dependence of the mixing rate on the stellar mass.

scholarly journals The (quite dark) stellar cluster around the supermassive black hole Sagittarius A* at the center of the Milky Way

2007 ◽  
Vol 3 (S245) ◽  
pp. 207-210
Author(s):  
Rainer Schödel ◽  
A. Eckart
Keyword(s):  
Black Hole ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Milky Way ◽  
Infrared Imaging ◽  
Current Theory ◽  
Star Cluster ◽  
Massive Black Hole ◽  
Stellar Cluster ◽  
Sagittarius A

AbstractHigh-resolution seeing limited and adaptive optics near-infrared imaging observations of the stellar cluster within about one parsec of the massive black hole Sagittarius A* allow us to obtain a detailed picture of the structure of the nuclear star cluster of the Milky Way. We find that the stellar number counts and the diffuse light of the unresolved stellar population can be described very well by a stellar density function in the form of a broken-power law. This agrees well with theoretical predictions on the structure of a dynamically relaxed star cluster around a massive black hole. However, the cusp slope is found to be too shallow, which may be related to mixing of different stellar populations and continuous star formation, phenomena that are not taken into account by current theory. Mass densities larger than 107 solar masses per pc3 are reached within 0.1 pc of the central black hole. Intriguingly, up to several tens of percent of the total cluster mass in the central parsec may be in the form of dark stellar remnants.

scholarly journals Dynamical modeling of the Arches cluster using Fokker-Planck calculations

2014 ◽  
Vol 10 (S312) ◽  
pp. 241-242
Author(s):  
Joowon Lee ◽  
Jihye Shin
Keyword(s):  
Massive Star ◽  
Velocity Dispersion ◽  
Galactic Center ◽  
Extreme Environment ◽  
Mass Function ◽  
Initial Condition ◽  
Star Forming ◽  
Concentration Parameter ◽  
Dispersion Surface ◽  
Fokker Planck

AbstractThe Arches cluster is a young, compact, and massive star cluster located in ~30pc away from the Galactic Center in projection. The cluster is located in the extreme environment of the Galactic Center, making it an excellent target for understanding the effects of star-forming environment on the mass function of star clusters. In this study, we estimate the initial condition (mass, concentration parameter, and galactocentric radius) of the Arches cluster by comparing Fokker-Planck calculations with observed velocity dispersion, surface density and mass function data.

Sign in / Sign up

Export Citation Format

Share Document