Astrophysical and Structural Parameters, And Dynamical Evolution Of The Open Clusters NGC 1245 And NGC 2099
Hikmet Çakmak, Orhan Güneş, Yüksel Karataş
备注：
14 pages, 8 figures and 6 tables. Accepted and published on December 2020 in the journal of Eskişehir Technical University Journal Of Science And Technology A-Applied Sciences And Engineering
We derive astrophysical and structural parameters of open clusters NGC 1245 and NGC 2099 from 2MASS JHKs and Gaia DR2 photometric / astrometric data bases. Their likely members have been determined from Gaia DR2 proper motion data. Our E(B-V) values (2MASS) are slightly smaller than the literature values, whereas our E(B-V) values (Gaia DR2) agree with the literature within the uncertainties. Their distance moduli/distances and ages are in good coincident with the literature. NGC 1245 has steep negative core mass function slope (MFs) (χ_core=-1.24). Its halo (χ_halo=+0.78) and overall (χ_overall=-0.95) MFs mean that it presents signs of small-scale mass segregation to the outer regions from its core, due to its [τ_rlx (overall),τ_overall ]=[302 Myr,5]. The MFs of NGC 2099 is very negative steep (χ_core=-2.67) in the core, and quite positive steep (χ_halo=+1.41) in the halo. This kind of MF slope steeping from the core to the outskirts indicates that low-mass stars in the core are transferred to the cluster's outskirts, while massive stars sink in the core, because of mass segregation. NGC 2099's flat overall MFs (χ_overall=+0.91) and its τ_overall=8 presents a sign of mass segregation. These OCs with the relatively large masses 8700 Msolar (NGC 1245) and 5660 Msolar (NGC 2099), which locate at RGC > 9 kpc, expose to external perturbations such as tidal effects and shock waves, and they lose their stars in low-proportions.
We derive astrophysical and structural parameters of the poorly studied open clusters NGC 6866, NGC 7062, and NGC 2360 based on filtered 2MASS (J, J -H) diagrams, and stellar radial density profiles. The field star decontamination technique is utilised for selecting high-probability cluster members. The E(B -V) reddening values of the three clusters derived from 2MASS JHKs agree with those inferred from UBV and uvby-β photometries. We find that the core mass function slopes are flatter than the halo's for the three clusters. The large core and cluster radii of NGC 6866 and NGC 2360 indicate an…
We determined astrophysical and dynamical parameters of the open clusters (OCs) NGC 2587, Collinder 268 (Col 268), Melotte 72 (Mel 72), and Pismis 7 from Gaia DR2 photometric/astrometric data and a new technique, fitCMD. fitCMD provides (Z, Age(Gyr)) as (0.025, 0.45) for NGC 2587, (0.0025, 0.5) for Col. 268, (0.011, 1.25) for Mel 72, and (0.008, 1.00) for Pismis 7, respectively. As compared to Gaia DR2 distances, the obtained photometric distances from fitCMD provide somewhat close distances. For NGC 2587 and Mel 72, both distances are in good concordance. Except for NGC 2587, the ages of the …
We present NGC 4565 and NGC 5746 as structural analogs of our Milky Way. All three are giant, SBb - SBbc galaxies with two pseudobulges, i. e., a compact, disky, star-forming pseudobulge embedded in a vertically thick, "red and dead", boxy pseudobulge that really is a bar seen almost end-on. The stars in the boxy bulge of our Milky Way are old and enhanced in alpha elements, indicating that star formation finished within ~ 1 Gyr of when it started. Here, we present Hobby-Eberly Telescope spectroscopy of the boxy pseudobulges of NGC 4565 and NGC 5746 and show that they also are made of old and …
Astrophysical parameters (age, reddening, distance, radius, luminosity function, mass function, total mass, relaxation time and mass segregation) have been estimated for open clusters NGC 2571, NGC 6802, Koposov 53 and Be 89 by using the Two Micron All Sky Survey (2MASS) photometry. We analyse the color-magnitude diagrams and stellar radial density profiles. We have found that NGC 2571 is the youngest one having young main sequence stars while Be 89 is the oldest cluster.
We review our recent studies of the globular cluster system of NGC 5128. First, we have obtained low-resolution, high signal-to-noise spectroscopy of 72 globular clusters using Gemini-S/GMOS to obtain the ages, metallicities, and the level of alpha enrichment of the metal-poor and metal-rich globular cluster subpopulations. Second, we have explored the rotational signature and velocity dispersion of the galaxy's halo using over 560 globular clusters with radial velocity measurements. We have also compared the dependence of these properties on galactocentric distance and globular cluster age an…
VST-SMASH: VST Survey of Mass Assembly and Structural Hierarchy II. Exploring dwarf galaxies in the vicinity of NGC 5068 and of the two galaxies NGC 5084 and NGC 5087 at the edges of the Virgo Supercluster
INAF – Osservatorio Astronomico di Capodimonte（那不勒斯天文台）；INAF – Osservatorio Astrofisico di Arcetri（阿切特里天文台）；Sterrenkundig Observatorium, Universiteit Gent（根特大学天文台）；Department of Astronomy, Indiana University（印第安纳大学天文学系）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚空间科学与天文台）；Department of Physics “E. Pancini”, University of Naples Federico II（那不勒斯费德里科二世大学物理系）；School of Mechanical, Electrical and Information Engineering, Shandong University（山东大学机电与信息工程学院）；Space physics and astronomy research unit, University of Oulu（奥卢大学空间物理与天文学研究部）；INAF – Osservatorio Astronomico di Trieste（的里雅斯特天文台）
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Structure and Evolution of Multi-Cluster within Galactic Disc: Gaia DR3 Insights into Eight Open Clusters
Cairo University（开罗大学）；Northern Border University（北部边境大学）；Istanbul University（伊斯坦布尔大学）；King Abdulaziz University（阿卜杜勒阿齐兹国王大学）；National Research Institute of Astronomy and Geophysics (NRIAG)（国家天文地球物理研究所）
The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age < 20 Myr for King 12, 20--40 Myr for NGC 7788, and 60 -- 80 Myr for NGC 7790 based on the properties of stars near the main sequence turn-off (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistent …
We present the results of CCD $UBV$ photometric and spectroscopic observations of the open cluster NGC 225. In order to determine the structural parameters of NGC 225, we calculated the stellar density profile in the cluster's field. We estimated the probabilities of the stars being physical members of the cluster using the existing astrometric data. The most likely members of the cluster were used in the determination of the astrophysical parameters of the cluster. We calculated the mean radial velocity of the cluster as $V_{r}=-8.3\pm 5.0$ km s$^{-1}$ from the optical spectra of eight stars …
We present a multiple stellar population (MSP) study of the globular cluster (GC) NGC~6752. We show that our new photometric CN index accurately traces the CN and the nitrogen abundances in cool giants, finding the discrete double red giant branch (RGB) and asymptotic giant branch (AGB) sequences with number ratios between the CN-weak and the CN-strong populations of \nrgb\ = 25:75 ($\pm$3; RGB) and 79:21 ($\pm$13; AGB). The discrepancy in these number ratios suggests that a significant fraction of the low-mass \cns\ stars failed to evolve into the AGB phase. However, unlike previous studies, …
Cosmological redshift of a Schwarzschild-de Sitter black hole: Towards estimating the Hubble constant
Instituto de Física, Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学物理研究所）；Facultad de Ciencias Físico-Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo（圣尼古拉斯德伊达尔戈米乔阿坎大学理学院）
We present multichromatic isochrone fits to the colour-magnitude data of the globular cluster NGC 6366, based on Hubble Space Telescope Advanced Camera for Surveys/Wide Field Channel and Southern Astrophysical Research photometric data. We corrected the photometric data for differential reddening and calculated the mean ridge line of the colour-magnitude diagrams. We compared the isochrones of Dartmouth Stellar Evolution Database and PAdova and TRieste Stellar Evolution Code both with microscopic diffusion starting on the main sequence. Bracketing all previous determinations of this cluster, w…
We used a combination of Hubble Space Telescope and ground based data to probe the dynamical state of the low mass Galactic globular cluster NGC 6101. We have re-derived the structural parameters of the cluster by using star counts and we find that it is about three times more extended than thought before. By using three different indicators, namely the radial distribution of Blue Straggler Stars, that of Main Sequence binaries and the luminosity (mass) function, we demonstrated that NGC 6101 shows no evidence of mass segregation, even in the innermost regions. Indeed, both the BSS and the bin…
We report the discovery of four new open clusters (named as QC 1, QC 2, QC3 and QC 4) in the direction of Cygnus Cloud and select their members based on five astrometric parameters (l, b, \varpi, μ^*_α, μ_δ) of Gaia DR2. We also derive their astrophysical parameters for each new cluster. Structure parameters are generated by fitting the radial density distribution with King's profile. Using solar metallicity, we performed isochrone-fitting on their purified color-magnitude diagrams (CMDs) to achieve the age of the clusters. The known cluster NGC 7062 at adjacent area is chosen to verify our id…
As an introduction of a kinematic survey of Magellanic Cloud (MC) star clusters, we report on the dynamical masses and mass-to-light ($M/L$) ratios of NGC 419 (SMC) and NGC 1846 (LMC). We have obtained more than one hundred high-resolution stellar spectra in and around each cluster using the multi-object spectrograph M2FS on the $Magellan$/Clay Telescope. Line-of-sight velocities and positions of the stars observed in each cluster were used as input to an expectation-maximization algorithm used to estimate cluster membership probabilities, resulting in samples of 46 and 52 likely members ($P_{…
We present a comprehensive photometric study of the old open cluster, NGC 6819 using 1x1 degree field VI MOSAIC CCD imaging taken with the WIYN 0.9m telescope. The resultant color-magnitude diagram (CMD) shows a well developed main sequence (MS) extending from V~14.5 mag down to our photometric limit of V~21 mag. Fitting theoretical isochrones with adopted values of the reddening and metallicity (E(B-V)=0.14, [Fe/H]=+0.09 dex) to the observed CMD yields a distance modulus of (m-M)_{0}=11.93+/-0.10 and an age of ~2.6 Gyr for NGC 6819. Our wide-field imaging reveals that NGC 6819 is larger in ar…
We report the discovery of 25 new open clusters resulting from a search in dense low galactic latitude fields. We also provide, for the first time, structural and astrophysical parameters for the new findings and 34 other recently discovered open clusters using Gaia DR2 data. The candidates were confirmed by jointly inspecting the vector point diagrams and spatial distribution. The discoveries were validated by matching near known objects and comparing their mean astrometric parameters with the available literature. A decontamination algorithm was applied to the three-dimensional astrometric s…
