scholarly journals The disintegrating old open cluster Czernik 3

2020 ◽  
Vol 498 (2) ◽  
pp. 2309-2322
Author(s):  
Saurabh Sharma ◽  
Arpan Ghosh ◽  
D K Ojha ◽  
R Pandey ◽  
T Sinha ◽  
...  
Keyword(s):  
Proper Motion ◽  
Near Infrared ◽  
Open Cluster ◽  
Mass Range ◽  
Mass Function ◽  
Optical Telescope ◽  
Motion Data ◽  
Tidal Interactions ◽  
Mass Segregation ◽  
Gaia Dr2

ABSTRACT We have performed a detailed analysis of the Czernik 3 (Cz3) open cluster by using deep near-infrared photometry taken with TIRCAM2 on the 3.6 m Devasthal optical telescope along with the recently available high-quality proper motion data from the Gaia DR2 and deep photometric data from Pan-STARRS1. The cluster has a highly elongated morphology with fractal distribution of stars. The core and cluster radii of the cluster are estimated as 0.5 and 1.2 pc, respectively. We have identified 45 stars as cluster members using the Gaia proper motion data. The distance and age of the cluster are found to be 3.5 ± 0.9 kpc and $0.9^{+0.3}_{-0.1}$ Gyr, respectively. The slope of the mass function `Γ′ in the cluster region, in the mass range ∼0.95 <M/M⊙ < 2.2, is found to be −1.01 ± 0.43. The cluster shows the signatures of mass segregation and is dynamically relaxed (dynamical age = 10 Myr). This along with its small size, big tidal radius, low density/large separation of stars, and elongated and distorted morphology indicates that the Cz3 is a loosely bound disintegrating cluster under the influence of external tidal interactions.

scholarly journals Photometric, kinematic, and variability study in the young open cluster NGC 1960

2020 ◽  
Vol 492 (3) ◽  
pp. 3602-3621 ◽  
Author(s):  
Y C Joshi ◽  
J Maurya ◽  
A A John ◽  
A Panchal ◽  
S Joshi ◽  
...  
Keyword(s):  
Open Cluster ◽  
Mass Range ◽  
Mass Function ◽  
Variable Stars ◽  
B Stars ◽  
V Band ◽  
Short Period ◽  
Young Open Cluster ◽  
Mass Segregation ◽  
Variability Study

ABSTRACT We present a comprehensive photometric analysis of a young open cluster NGC 1960 (= M36) along with the long-term variability study of this cluster. Based on the kinematic data of Gaia DR2, the membership probabilities of 3871 stars are ascertained in the cluster field among which 262 stars are found to be cluster members. Considering the kinematic and trigonometric measurements of the cluster members, we estimate a mean cluster parallax of 0.86 ± 0.05 mas and mean proper motions of μRA = −0.143 ± 0.008 mas yr−1 and μDec. = −3.395 ± 0.008 mas yr−1. We obtain basic parameters of the cluster such as E(B − V) = 0.24 ± 0.02 mag, log(Age/yr) = 7.44 ± 0.02, and d = 1.17 ± 0.06 kpc. The mass function slope in the cluster for the stars in the mass range of 0.72–7.32 M⊙ is found to be γ = −1.26 ± 0.19. We find that mass segregation is still taking place in the cluster which is yet to be dynamically relaxed. This work also presents first high-precision variability survey in the central 13 arcmin × 13 arcmin region of the cluster. The V-band photometric data accumulated on 43 nights over a period of more than 3 yr reveals 76 variable stars among which 72 are periodic variables. Among them, 59 are short period (P < 1 d) and 13 are long period (P > 1 d). The variable stars have V magnitudes ranging between 9.1 to 19.4 mag and periods between 41 min and 10.74 d. On the basis of their locations in the H–R diagram, periods, and characteristic light curves, 20 periodic variables belong to the cluster are classified as 2 δ-Scuti, 3 γ-Dor, 2 slowly pulsating B stars, 5 rotational variables, 2 non-pulsating B stars, and 6 as miscellaneous variables.

scholarly journals A comprehensive study of open clusters Czernik 14, Haffner 14, Haffner 17 and King 10 using multicolour photometry and Gaia DR2 astrometry

2020 ◽  
Vol 494 (1) ◽  
pp. 607-623 ◽  
Author(s):  
D Bisht ◽  
Qingfeng Zhu ◽  
R K S Yadav ◽  
Alok Durgapal ◽  
Geeta Rangwal
Keyword(s):  
Interstellar Extinction ◽  
Mass Function ◽  
Open Clusters ◽  
Circular Path ◽  
Galactic Centre ◽  
Data Sets ◽  
Motion Data ◽  
Solar Metallicity ◽  
Mass Segregation ◽  
Gaia Dr2

ABSTRACT This paper presents an investigation into the four open clusters Czernik 14, Haffner 14, Haffner 17 and King 10, located near the Perseus arm of the Milky Way, using the Gaia DR2, 2MASS, WISE, APASS and Pan-STARRS1 data sets. We find normal interstellar extinction in 12 photometric bands for these clusters. Using Gaia DR2 proper motion data, the numbers of likely cluster members are found to be 225, 353, 350 and 395 for Czernik 14, Haffner 14, Haffner 17 and King 10, respectively. Radii are determined as 3.5, 3.7, 6.2 and 5.7 arcmin for Czernik 14, Haffner 14, Haffner 17 and King 10, respectively. Mean proper motions in RA and Dec. are estimated as (−0.42 ± 0.02, −0.38 ± 0.01), (−1.82 ± 0.009, 1.73 ± 0.008), (−1.17 ± 0.007, 1.88 ± 0.006) and (−2.75 ± 0.008, −2.04 ± 0.006) mas yr−1 for Czernik 14, Haffner 14, Haffner 17 and King 10, respectively. The comparison of observed colour–magnitude diagrams with solar metallicity isochrones leads to ages of 570 ± 60, 320 ± 35, 90 ± 10 and 45 ± 5 Myr for these clusters. The distances of 2.9 ± 0.1, 4.8 ± 0.4, 3.6 ± 0.1 and 3.8 ± 0.1 kpc determined using parallax are similar to the values derived by the isochrone-fitting method. Mass function slopes are found to be in good agreement with the Salpeter value. The total masses are derived as 348, 595, 763 and 1088 M⊙ for Czernik 14, Haffner 14, Haffner 17 and King 10, respectively. Evidence for the existence of a mass-segregation effect is observed in each cluster. Using the Galactic potential model, Galactic orbits are derived for the clusters. It is found that all four clusters follow a circular path around the Galactic Centre.

scholarly journals An optical observational cluster mass function at z ∼ 1 with the ORELSE survey

2021 ◽  
Vol 502 (3) ◽  
pp. 3942-3954
Author(s):  
D Hung ◽  
B C Lemaux ◽  
R R Gal ◽  
A R Tomczak ◽  
L M Lubin ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Large Scale ◽  
Near Infrared ◽  
Function Analysis ◽  
Voronoi Tessellation ◽  
Cosmological Parameters ◽  
Mass Range ◽  
Mass Function ◽  
Cluster Mass ◽  
Theoretical Mass

ABSTRACT We present a new mass function of galaxy clusters and groups using optical/near-infrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey. At z ∼ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ∼ 1 cluster mass functions are achievable without supplemental X-ray or Sunyaev-Zel’dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ∼240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M⊙) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ωm, and the amplitude of fluctuations, σ8, of $\Omega _{m} = 0.250^{+0.104}_{-0.099}$ and $\sigma _{8} = 1.150^{+0.260}_{-0.163}$. While our Ωm value is close to concordance, our σ8 value is ∼2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.

scholarly journals High-contrast and resolution near-infrared photometry of the core of R136

2021 ◽  
Vol 503 (1) ◽  
pp. 292-311
Author(s):  
Zeinab Khorrami ◽  
Maud Langlois ◽  
Paul C Clark ◽  
Farrokh Vakili ◽  
Anne S M Buckner ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Outer Region ◽  
Mass Range ◽  
Mass Function ◽  
Large Magellanic Cloud ◽  
Star Forming ◽  
The Core ◽  
Very Large Telescope ◽  
30 Doradus

ABSTRACT We present the sharpest and deepest near-infrared photometric analysis of the core of R136, a newly formed massive star cluster at the centre of the 30 Doradus star-forming region in the Large Magellanic Cloud. We used the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode for the second time with longer exposure time in the H and K filters. Our aim was to (i) increase the number of resolved sources in the core of R136, and (ii) to compare with the first epoch to classify the properties of the detected common sources between the two epochs. Within the field of view (FOV) of 10.8″ × 12.1″ ($2.7\,\text {pc}\times 3.0\, \text {pc}$), we detected 1499 sources in both H and K filters, for which 76 per cent of these sources have visual companions closer than 0.2″. The larger number of detected sources enabled us to better sample the mass function (MF). The MF slopes are estimated at ages of 1, 1.5, and 2 Myr, at different radii, and for different mass ranges. The MF slopes for the mass range of 10–300 M⊙ are about 0.3 dex steeper than the mass range of 3–300 M⊙, for the whole FOV and different radii. Comparing the JHK colours of 790 sources common in between the two epochs, 67 per cent of detected sources in the outer region (r > 3″) are not consistent with evolutionary models at 1–2 Myr and with extinctions similar to the average cluster value, suggesting an origin from ongoing star formation within 30 Doradus, unrelated to R136.

scholarly journals STUDY OF AN INTERMEDIATE AGE OPEN CLUSTER IC 1434 USING GROUND-BASED IMAGING AND GAIA DR2 ASTROMETRY

2021 ◽  
Vol 57 (2) ◽  
pp. 381-389
Author(s):  
Y. H. M. Hendy ◽  
D. Bisht
Keyword(s):  
Radial Distribution ◽  
Proper Motion ◽  
Open Cluster ◽  
Membership Probability ◽  
Kinematical Analysis ◽  
The Mean ◽  
First Time ◽  
Right Ascension ◽  
Cluster Age ◽  
Gaia Dr2

We present a detailed photometric and kinematical analysis of the poorly studied open cluster IC 1434 using CCD VRI, APASS, and Gaia DR2 database for the first time. By determining the membership probability of stars we identify the 238 most probable members with a probability higher than 60%; by using proper motion and parallax data as taken from the Gaia DR2 catalog. The mean proper motion of the cluster is obtained as μx=−3.89±0.19 and μy=−3.34±0.19 mas yr−1 in both the directions of right ascension and declination. The radial distribution of member stars provides the cluster extent as 7.6 arcmin. We estimate the interstellar reddening E(B−V) as 0.34 mag using the transformation equations from the literature. We obtain the values of cluster age and distance as 631±73 Myr and 3.2±0.1 kpc.

scholarly journals Astrometric and photometric study of NGC 6067, NGC 2506, and IC 4651 open clusters based on wide-field ground and Gaia DR2 data

2019 ◽  
Vol 490 (1) ◽  
pp. 1383-1396 ◽  
Author(s):  
Geeta Rangwal ◽  
R K S Yadav ◽  
Alok Durgapal ◽  
D Bisht ◽  
D Nardiello
Keyword(s):  
Function Analysis ◽  
Mass Range ◽  
Mass Function ◽  
Open Clusters ◽  
Wide Field ◽  
Open Star Clusters ◽  
Potential Models ◽  
Open Star ◽  
Astrometric Data ◽  
Gaia Dr2

ABSTRACT We present an analysis of three southern open star clusters NGC 6067, NGC 2506, and IC 4651 using wide-field photometric and Gaia DR2 astrometric data. They are poorly studied clusters. We took advantage of the synergy between Gaia DR2 high precision astrometric measurements and ground-based wide-field photometry to isolate cluster members and further study these clusters. We identify the cluster members using proper motions, parallax and colour–magnitude diagrams. Mean proper motion of the clusters in μαcosδ and μδ is estimated as −1.90 ± 0.01 and −2.57 ± 0.01 mas yr−1 for NGC 6067, −2.57 ± 0.01, and 3.92 ± 0.01 mas yr−1 for NGC 2506 and −2.41 ± 0.01 and −5.05 ± 0.02 mas yr−1 for IC 4651. Distances are estimated as 3.01 ± 0.87, 3.88 ± 0.42, and 1.00 ± 0.08 kpc for the clusters NGC 6067, NGC 2506, and IC 4651, respectively, using parallaxes taken from Gaia DR2 catalogue. Galactic orbits are determined for these clusters using Galactic potential models. We find that these clusters have circular orbits. Cluster radii are determined as 10 arcmin for NGC 6067, 12 arcmin for NGC 2506, and 11 arcmin for IC 4651. Ages of the clusters estimated by isochrones fitting are 66 ± 8 Myr, 2.09 ± 0.14 Gyr, and 1.59 ± 0.14 Gyr for NGC 6067, NGC 2506, and IC 4651, respectively. Mass function slope for the entire region of cluster NGC 2506 is found to be comparable with the Salpeter value in the mass range of 0.77–1.54 M⊙. The mass function analysis shows that the slope becomes flat when one goes from halo to core region in all the three clusters. A comparison of dynamical age with cluster’s age indicates that NGC 2506 and IC 4651 are dynamically relaxed clusters.

scholarly journals A census of the nearby Pisces-Eridanus stellar stream

2020 ◽  
Vol 638 ◽  
pp. A9 ◽  
Author(s):  
Siegfried Röser ◽  
Elena Schilbach
Keyword(s):  
Luminosity Function ◽  
Open Cluster ◽  
Space Velocity ◽  
Mass Function ◽  
Molecular Gas ◽  
Cylindrical Shape ◽  
The Sun ◽  
Data Set ◽  
Mass Segregation ◽  
Formation Efficiency

Aims. Within a sphere of 400 pc radius around the Sun, we aim to search for members of the Pisces-Eridanus (Psc-Eri) stellar stream in the Gaia Data Release 2 data set. We compare basic astrophysical characteristics of the stream with those of the Pleiades. Methods. We used a modified convergent-point method to identify stars with 2D velocities consistent with the space velocity of the Psc-Eri stream and the Pleiades, respectively. Results. In a G magnitude range from 5.1 mag to 19.3 mag, we found 1387 members of the Psc-Eri stream at distances between 80 and 380 pc from the Sun. The stream has a nearly cylindrical shape with a length of at least 700 pc and a thickness of 100 pc. The accumulated stellar mass of the 1387 members amounts to about 770 M⊙, and the stream is gravitationally unbound. For the stream, we found an age of about 135 Myr. In many astrophysical properties, Psc-Eri is comparable to the open cluster M45 (the Pleiades): in its age, its luminosity function, its present-day mass function, as well as in its total mass. Nonetheless, the two stellar ensembles are completely different in their physical appearance. We cautiously give two possible explanations for this disagreement: (i) the star formation efficiency in their parental molecular clouds was higher for the Pleiades than for Psc-Eri, and/or (ii) the Pleiades had a higher primordial mass segregation immediately after the expulsion of the molecular gas of the parental cloud.

scholarly journals Mass Segregation in the Young SMC Cluster NGC 330

2002 ◽  
Vol 207 ◽  
pp. 687-690
Author(s):  
Marco Sirianni ◽  
Antonella Nota ◽  
Guido De Marchi ◽  
Claus Leitherer ◽  
Mark Clampin
Keyword(s):  
Luminosity Function ◽  
Radial Distance ◽  
Mass Range ◽  
Mass Function ◽  
Young Star ◽  
Initial Mass Function ◽  
Cluster Center ◽  
Central Regions ◽  
Mass Segregation ◽  
The Imf

We present a new study of the low end of the stellar IMF of NGC 330, the richest young star cluster in the Small Magellanic Cloud (SMC). Using deep broadband images taken with the HST/WFPC2 we have derived the cluster's luminosity function and constructed the initial mass function (IMF) in the mass range 1 − 7M⊙. We have investigated the IMF as a function of the radial distance from the cluster center. We find that, after correction for background contamination, the IMF is fairly homogeneous with a slope slightly steeper than Salpeter's in the central regions of the cluster (< 40″) but becomes increasingly steeper with distance, indicating a preponderance of massive stars in the core of the cluster. NGC 330 is one of the first clusters for which evidence of mass segregation is directly found.

scholarly journals VVV-WIT-04: an extragalactic variable source caught by the VVV Survey

2019 ◽  
Vol 490 (1) ◽  
pp. 1171-1178 ◽  
Author(s):  
R K Saito ◽  
D Minniti ◽  
V D Ivanov ◽  
N Masetti ◽  
M G Navarro ◽  
...  
Keyword(s):  
Proper Motion ◽  
Near Infrared ◽  
Galactic Disc ◽  
Transient Event ◽  
Variable Source ◽  
Motion Data ◽  
Near Ir ◽  
Public Survey ◽  
Alternative Scenarios ◽  
Archive Data

ABSTRACT We report the discovery of VVV-WIT-04, a near-infrared (near-IR) variable source towards the Galactic disc located ∼0.2 arcsec apart from the position of the radio source PMN J1515−5559. The object was found serendipitously in the near-IR data of the ESO public survey VISTA Variables in the Vía Láctea (VVV). Our analysis is based on variability, multicolour, and proper motion data from VVV and VVV eXtended surveys, complemented with archive data at longer wavelengths. We suggest that VVV-WIT-04 has an extragalactic origin as the near-IR counterpart of PMN J1515−5559. The Ks-band light curve of VVV-WIT-04 is highly variable and consistent with that of an optically violent variable quasar. The variability in the near-IR can be interpreted as the redshifted optical variability. Residuals to the proper motion vary with the magnitude suggesting contamination by a blended source. Alternative scenarios, including a transient event such as a nova or supernova, or even a binary microlensing event, are not in agreement with the available data.

scholarly journals Unlocking Galactic Wolf–Rayet stars with Gaia DR2 – II. Cluster and association membership

2020 ◽  
Vol 495 (1) ◽  
pp. 1209-1226 ◽  
Author(s):  
Gemma Rate ◽  
Paul A Crowther ◽  
Richard J Parker
Keyword(s):  
Near Infrared ◽  
Galactic Centre ◽  
Low Density ◽  
Cluster Membership ◽  
Star Forming ◽  
Star Forming Regions ◽  
Centre Region ◽  
Ob Associations ◽  
Mass Segregation ◽  
Gaia Dr2

ABSTRACT Galactic Wolf–Rayet (WR) star membership of star-forming regions can be used to constrain the formation environments of massive stars. Here, we utilize Gaia DR2 parallaxes and proper motions to reconsider WR star membership of clusters and associations in the Galactic disc, supplemented by recent near-infrared studies of young massive clusters. We find that only 18–36 per cent of 553 WR stars external to the Galactic Centre region are located in clusters, OB associations or obscured star-forming regions, such that at least 64 per cent of the known disc WR population are isolated, in contrast with only 13 per cent of O stars from the Galactic O star Catalogue. The fraction located in clusters, OB associations or star-forming regions rises to 25–41 per cent from a global census of 663 WR stars including the Galactic Centre region. We use simulations to explore the formation processes of isolated WR stars. Neither runaways, nor low-mass clusters, are numerous enough to account for the low cluster membership fraction. Rapid cluster dissolution is excluded as mass segregation ensures WR stars remain in dense, well-populated environments. Only low-density environments consistently produce WR stars that appeared to be isolated during the WR phase. We therefore conclude that a significant fraction of WR progenitors originate in low-density association-like surroundings which expand over time. We provide distance estimates to clusters and associations host to WR stars, and estimate cluster ages from isochrone fitting.

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