New radial velocity measurements for previously known and newly confirmed globular clusters (GCs) in the nearby massive galaxy NGC 5128 are presented. We have obtained spectroscopy from LDSS-2/Magellan, VIMOS/VLT, and Hydra/CTIO from which we have measured the radial velocities of 218 known, and identified 155 new, GCs. The current sample of confirmed GCs in NGC 5128 is now 605 with 564 of these having radial velocity measurements. We have performed a new kinematic analysis of the GC system that extends out to 45 arcmin in galactocentric radius. We have examined the systemic velocity, projected rotation amplitude and axis, and the projected velocity dispersion of the GCs as functions of galactocentric distance and metallicity. Our results indicate that the metal-poor GCs have a very mild rotation signature of (26 pm 15) km/s. The metal-rich GCs are rotating with a higher, though still small signature of (43 pm 15) km/s around the isophotal major axis of NGC 5128 within 15 arcmin. Their velocity dispersions are consistent within the uncertainties and the profiles appear flat or declining within 20 arcmin. We note the small sample of metal-rich GCs with ages less than 5 Gyr in the literature appear to have different kinematic properties than the old, metal-rich GC subpopulation. The mass and mass-to-light ratios have also been estimated using the GCs as tracer particles for NGC 5128. Out to a distance of 20 arcmin, we have obtained a mass of (5.9 pm 2.0) x 10^(11) M_(sun) and a mass-to-light ratio in the B-band of 16 M_(sun)/L_(B,sun). Combined with previous work on the ages and metallicities of its GCs, as well as properties of its stellar halo, our findings suggest NGC 5128 formed via hierarchical merging over other methods of formation, such as major merging at late times.
In this work a search was carried out for globular clusters belonging to the Sagittarius (Sgr) tidal stream using the analysis of spatial positions, radial velocities relative to the Galactic Standard of Rest (V_{GSR}),proper motions and ratio of "age -- metallicity" ([Fe/H]) for globular clusters and for stars in the tidal stream. As a result, three categories of globular clusters were obtained: A -- most certainly in the stream: Terzan 8, Whiting 1, Arp 2, NGC 6715, Terzan 7, Pal 12; B -- kinematic outliers: Pal 5, NGC 5904, NGC 5024, NGC 5053, NGC 5272, NGC 288; C -- lowest rank candidates:…
Even after decades of research, the origin of multiple stellar populations in globular clusters remains enigmatic. The question as to whether the galaxy environment plays a role in their formation remains unanswered. To that extent, we analysed two classical (> 10 Gyr old) Large Magellanic Cloud globular clusters namely, NGC 1786 and NGC 1898, using imaging data from Hubble Space Telescope to compare and contrast them with ancient Galactic globular clusters to assess systematic differences that might exist between their abundance variations. We calculated their Red Giant Branch width, subtract…
Globular clusters are prone to lose stars while moving around the Milky Way. These stars escape the clusters and are distributed throughout extended envelopes or tidal tails. However, such extra-tidal structures are not observed in all globular clusters, and yet there is no structural or dynamical parameters that can predict their presence or absence. NGC\,6864 is an outer halo globular cluster with reported no observed tidal tails. We used Dark Energy Camera (DECam) photometry reaching $\sim$ 4 mag underneath its main sequence turnoff to confidently detect an extra-tidal envelope, and stellar…
An intermediate-band photometric study of the "Globular Cluster" NGC 2419
NGC 2419是银河系晕中最遥远的星团之一，它的确切性质尚不清楚：虽然它具有让人想起球状星团（GC）的特征，但它的大半径和丰度分布的建议引发了关于它起源于河外环境的讨论，可能是矮星系吸积的残余物。在这里，我们提出的第一个结果，从深中间波段测光的NGC 2419，这使我们能够寻找化学（轻元素）丰度的变化，金属丰度的蔓延，从而多个恒星星族通过良好校准的Stroemgren指数。
The globular cluster system of the isolated elliptical NGC 6411: An old system in an intermediate-age galaxy?
利用Gemini/GMOS g '，r'，i'测光方法对孤立椭圆星系NGC 6411及其球状星团（GC）系统进行了测光研究。这个星系是一个SNIA的宿主。光谱研究表明，在它的内部区域有一个中等年龄和非常富含金属的恒星星族。球状星团系统的范围约为65千秒差距。它的星群包含$700\pm45$成员，这意味着一个相当差的系统，就像通常在孤立的椭圆星系中发现的那样。颜色双峰和光度分布是旧GC系统的典型特征。过多的中间颜色的明亮GC可能证明了一个中间年龄的合并，但它们的颜色表明了一个比来自星系漫射光光谱研究的年龄更老的事件。
We present the results of determination of the age, helium mass fraction (Y), metallicity ([Fe/H]), and abundances of the elements C, N, O, Na, Mg, Ca, Ti, C and Mn for the Galactic globular cluster NGC 6652. We use its medium-resolution integrated-light spectrum from the library of Schiavon and our population synthesis method to fulfill this task. We select the evolutionary isochrone and stellar mass function for our analysis, which provide the best approximation to the shapes and intensities of the observed Balmer line profiles. The determined elemental abundances, age and metallicity are ch…
We study the outer regions of the Milky Way globular cluster NGC6809 based on Dark Energy Camera (DECam) observations, which reach nearly 6 mag below the cluster main sequence (MS) turnoff. In order to unveil its fainter outermost structure, we built stellar density maps using cluster MS stars, once the contamination of field stars was removed from the cluster color-magnitude diagram. We found that only the resulting stellar density map for the lightest stars exhibits some excesses of stars at opposite sides from the cluster centre that diminish soon thereafter at ~ 0.32 deg. Studied globular …
Aims. We present a new technique to estimate the relative ages of multiple stellar populations hosted by five globular clusters: NGC 104 (47 Tuc), NGC 6121 (M4), NGC 6352, NGC 6362 and NGC 6723. Methods. We used the catalogs of the database "HST UV Globular cluster Survey (HUGS)" to create color-magnitude and two-color diagrams of the Globular Clusters. We identified the multiple populations within each globular cluster, and we divided them into two main stellar populations: POPa or first generation (1G) and POPb, composed of all the successive generations of stars. The new technique allows us…
The Peculiar Chemical Inventory of NGC 2419 -- An Extreme Outer Halo "Globular Cluster"
NGC 2419是一个巨大的外晕星系球状星团，其恒星先前已被证明具有某种特殊的丰度模式。我们用Keck/HIRES在合理的信噪比下观测到了NGC 2419的7颗亮巨星。其中一颗巨行星非常特殊，[Mg/Fe]极低，[K/Fe]极高，但大多数其他元素的丰度正常。丰度模式与任何超新星模型的核合成产率都不匹配。其他六颗恒星的丰度比是典型的内晕星系球状星团，图中以附近球状星团M30中的巨星为代表。虽然我们的测量表明NGC 2419在某些方面是不寻常的，但它的整体性质并没有提供令人信服的证据来证明内晕和外晕球状星团之间的差异。
We present metallicities for red giant stars in the globular cluster NGC 6273 based on intermediate resolution GMOS-S spectra of the calcium triplet region. For the 42 radial velocity members with reliable calcium triplet line strength measurements, we obtain metallicities, [Fe/H], using calibrations established from standard globular clusters. We confirm the presence of an intrinsic abundance dispersion identified by Johnson et al. (2015). The total range in [Fe/H] is ~1.0 dex and after taking into account the measurement errors, the intrinsic abundance dispersion is σ[Fe/H] = 0.17 dex. Among…
Kinematics of Multiple Stellar Populations in Globular Clusters with Gaia
球状星团（GC）中多个恒星星族的内部动力学对它们形成的物理过程提供了独特的约束。特别是，星团恒星的现今运动学，如自转和速度色散，似乎与系统的初始配置有关。在最近的工作中（Milone et al. 2018），我们第一次分析了NGC0104（47 Tuccino）中不同恒星星族在大视场内的运动学，利用Gaia Data Release 2自行与多波段地基测光相结合。本文基于Cordoni等人的工作。（2019），我们将这种分析扩展到六个GC，即NGC0288，NGC5904（M5），NGC6121（M4），NGC6752，NGC6838（M71），并进一步探索NGC0104。在分析的星系团中，只有NGC0104和NGC5904在天空平面上显示出明显的旋转。有趣的是，NGC5904中的多个恒星星族呈现出不同的自转曲线。
Context. Extratidal stars are stellar bodies that end up outside the tidal radius of a cluster as a result of internal processes or external forces acting upon it. The presence and spatial distribution of these stars can give us insights into the past evolution of a cluster inside our Galaxy. Aims. Previous works suggest that globular clusters, when explored in detail, show evidence of extratidal stars. We aim to search for possible extratidal stars in the Galactic globular clusters NGC 6397, NGC 2808, and NGC 6266 using the photometry and proper motion measurements from Gaia DR2 database (Gai…
Ultra-diffuse galaxies that contain a large sample of globular clusters (GCs) offer an opportunity to test the predictions of galactic dynamics theory. NGC5846-UDG1 is an excellent example, with a high-quality sample of dozens of GC candidates. We show that the observed distribution of GCs in NGC5846-UDG1 is suggestive of mass segregation induced by gravitational dynamical friction. We present simple analytic calculations, backed by a series of numerical simulations, that naturally explain the observed present-day pattern of GC masses and radial positions. Subject to some assumptions on the GC…
We analyse Gaia EDR3 and re-calibrated HST proper motion data from the core-collapsed and non core-collapsed globular clusters NGC 6397 and NGC 3201, respectively, with the Bayesian mass-orbit modelling code MAMPOSSt-PM. We use Bayesian evidence and realistic mock data sets constructed with AGAMA to select between different mass models. In both clusters, the velocities are consistent with isotropy within the extent of our data. We robustly detect a dark central mass (DCM) of roughly 1000 solar masses in both clusters. Our MAMPOSSt-PM fits strongly prefer an extended DCM in NGC 6397, while only…
FORS2/VLT survey of Milky Way globular clusters I. Description of the method for derivation of metal abundances in the optical and application to NGC 6528, NGC 6553, M 71, NGC 6558, NGC 6426 and Terzan 8
We investigate archival Hubble Space Telescope ACS/SBC F140LP observations of NGC~1399 to search for evidence of multiple stellar populations in extragalactic globular clusters. Enhanced FUV populations are thought to be indicators of He-enhanced second generation populations in globular clusters, specifically extreme/blue horizontal branch stars. Out of 149 globular clusters in the field of view, 58 have far ultraviolet (FUV) counterparts with magnitudes brighter than 28.5. Six of these FUV-deteced globular clusters are also detected in X-rays, including one ultraluminous X-ray source ($L_X >…
