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101.
102.
G. S. D. Babu 《Journal of Astrophysics and Astronomy》1987,8(3):219-226
Photoelectric and photographic photometry of twenty-nine stars was done in the field of the open cluster Collinder 97 ≡ OC1
506. Of these stars, a total of twenty-four have been found to be possible members. There is apparently no interstellar extinction
in the direction of this cluster which is in the constellation of Monoceros: itsE(B-V) = 0.0 mag. This cluster is situated at a distance of 0.63 ± 0.01 kpc, which is well within the local arm of our Galaxy. The
age of this cluster is in the range of 1 × 108 to 5.9 × l08 yr, which puts it in an older age group. Thus, it cannot be specifically considered as a spiral-arm tracer in the study of
our Galaxy. 相似文献
103.
We use data on open star clusters (OSCs) from the Homogeneous Catalog of OSC Parameters to determine some of the parameters of the spiral structure of our Galaxy: the pitch angle of the spiral arms \(i = 21\mathop .\limits^ \circ 5\), the pattern speed Ωp = 20.4 ± 2.5 km s?1 kpc?1, and the initial phase of the spiral θ0 = 206°. The spiral pattern of the Galaxy proves to have been virtually unchanged over the last billion years, and signatures of the concentration of objects toward the spiral arms can be traced back to this age. However, the number of spiral arms in the structure cannot be determined from OSCs. 相似文献
104.
XPer的新发射相:光谱与红外观测 总被引:1,自引:0,他引:1
XPer的新发射相:光谱与红外观测杭恒荣,夏剑萍中国科学院紫金山天文台,南京210008中国科学院光学天文联合实验室关键词Be星/X射线双星,发射线,JHK测光1引言XPer是一颗Be/X射线双星(4U0352+30)的光学对应体[1-3],中子星的... 相似文献
105.
106.
P. Firth E. A. Evstigneeva M. J. Drinkwater 《Monthly notices of the Royal Astronomical Society》2009,394(4):1801-1811
From high signal-to-noise ratio GMOS-N and AAOmega spectra, we have measured line-strength indices in the Lick/IDS system for several luminous and spatially dispersed compact stellar systems (CSSs) located in the Virgo and Fornax galaxy clusters. We estimate their [α/Fe] ratios, ages and metallicities using a simple (single-burst) stellar population model. We confirm that the Virgo core region luminous CSSs ( ) contain ancient stellar populations with subsolar total metallicities, suggesting that they comprise the bright tail of M87's GC distribution. The two Virgo intracluster globular clusters have ages and metallicities consistent with the cluster core CSSs. Two Fornax luminous CSSs also have ancient stellar populations but are at the upper end of the Virgo CSS metallicity range, while the third (UCD3) appears to be relatively young, metal-rich and with a core + halo radial profile. Our results suggest that Fornax may contain an extra population of luminous CSSs formed more recently than the ancient GC-like systems found in both clusters. 相似文献
107.
Juan C. Forte E. Irene Vega Favio Faifer 《Monthly notices of the Royal Astronomical Society》2009,397(2):1003-1020
This paper explores if, and to what an extent, the stellar populations of early-type galaxies can be traced through the colour distribution of their globular cluster (GC) systems. The analysis, based on a galaxy sample from the Virgo Advanced Camera for Surveys data, is an extension of a previous approach that has been successful in the cases of the giant ellipticals NGC 1399 and NGC 4486, and assumes that the two dominant GC populations form along diffuse stellar populations sharing the cluster chemical abundances and spatial distributions. The results show that (a) integrated galaxy colours can be matched to within the photometric uncertainties and are consistent with a narrow range of ages; (b) the inferred mass to luminosity ratios and stellar masses are within the range of values available in the literature; (c) most GC systems occupy a thick plane in the volume space defined by the cluster formation efficiency, total stellar mass and projected surface mass density. The formation efficiency parameter of the red clusters shows a dependency with projected stellar mass density that is absent for the blue globulars. In turn, the brightest galaxies appear clearly detached from that plane as a possible consequence of major past mergers; (d) the stellar mass–metallicity relation is relatively shallow but shows a slope change at M * ≈ 1010 M⊙ . Galaxies with smaller stellar masses show predominantly unimodal GC colour distributions. This result may indicate that less massive galaxies are not able to retain chemically enriched interstellar matter. 相似文献
108.
M. Gieles 《Monthly notices of the Royal Astronomical Society》2009,394(4):2113-2126
Several recent studies have shown that the star cluster initial mass function (CIMF) can be well approximated by a power law, with indications for a steepening or truncation at high masses. This contribution considers the evolution of such a mass function due to cluster disruption, with emphasis on the part of the mass function that is observable in the first ∼1 Gyr. A Schechter type function is used for the CIMF, with a power-law index of −2 at low masses and an exponential truncation at M * . Cluster disruption due to the tidal field of the host galaxy and encounters with giant molecular clouds flattens the low-mass end of the mass function, but there is always a part of the 'evolved Schechter function' that can be approximated by a power law with index −2. The mass range for which this holds depends on age, τ, and shifts to higher masses roughly as τ0.6 . Mean cluster masses derived from luminosity-limited samples increase with age very similarly due to the evolutionary fading of clusters. Empirical mass functions are, therefore, approximately power laws with index −2, or slightly steeper, at all ages. The results are illustrated by an application to the star cluster population of the interacting galaxy M51, which can be well described by a model with M * = (1.9 ± 0.5) × 105 M⊙ and a short (mass-dependent) disruption time destroying M * clusters in roughly a Gyr. 相似文献
109.
110.
M. Fellhauer M. I. Wilkinson P. Kroupa 《Monthly notices of the Royal Astronomical Society》2009,397(2):954-962
Recent observations and hydrodynamical simulations of star formation inside a giant molecular cloud have revealed that, within a star-forming region, stars do not form evenly distributed throughout this region, but rather in small subclumps. It is generally believed that these subclumps merge and form a young star cluster. The time-scale of this merging process is crucial for the evolution and the possible survival of the final star cluster. The key issue is whether this merging process happens faster than the time needed to remove the residual gas of the cloud. A merging time-scale shorter than the gas-removal time would enhance the survival chances of the resulting star cluster. In this paper, we show by means of numerical simulations that the time-scale of the merging is indeed very fast. Depending on the details of the initial subclump distribution, the merging may occur before the gas is expelled from the newly formed cluster via either supernovae or the winds from massive stars. Our simulations further show that the resulting merger objects have a higher effective star formation efficiency than the overall star-forming region and confirm the results that mass-segregated subclumps form mass-segregated merger objects. 相似文献