The binary fraction and mass segregation in Alpha Persei open cluster

Abstract We have obtained membership probabilities of stars within a field of ${\sim }3\deg$ from the centre of the open cluster Alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of Alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of Alpha Persei shows a turnover at m = 0.62 M⊙ with low- and high-mass slopes of αlow = 0.50 ± 0.09 (0.1 < m/ M⊙ < 0.62) and αhigh = 2.32 ± 0.14 (0.62 ≤ m/ M⊙ < 4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 1$_{.}^{\circ}$10 to 2.63 outside 2$_{.}^{\circ}$2, whereas the mean stellar mass decreases from 0.95 to 0.57 M⊙ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour–magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin = 34 ± 12 per cent for stars with 0.70 < m/ M⊙ < 4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of αlow = 0.89 ± 0.11 and αhigh = 2.37 ± 0.09 and a total cluster mass of 352 M⊙ for Alpha Persei.

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A Search for Brown Dwarfs in the Alpha Persei Cluster

Symposium - International Astronomical Union ◽

10.1017/s0074180900210528 ◽

2003 ◽

Vol 211 ◽

pp. 179-180

Author(s):

Nicolas Lodieu ◽

Mark McCaughrean ◽

Jérôme Bouvier ◽

David Barrado y Navascués ◽

John R. Stauffer

Keyword(s):

Near Infrared ◽

Open Cluster ◽

Brown Dwarfs ◽

Wide Field ◽

Brown Dwarf ◽

Young Open Cluster ◽

Low Mass ◽

Alpha Persei ◽

Calar Alto ◽

Infrared Survey

We present preliminary results from a deep near-infrared survey of a ~ 1 square degree area in the young open cluster Alpha Persei using the wide-field Omega-Prime camera on the Calar Alto 3.5m telescope, yielding a list of new low-mass cluster members, including brown dwarf candidates.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa029 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3602-3621 ◽

Cited By ~ 4

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.

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A census of the nearby Pisces-Eridanus stellar stream

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037691 ◽

2020 ◽

Vol 638 ◽

pp. A9 ◽

Cited By ~ 3

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.

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Structure and Mass Function of Open Cluster NGC 6910

Journal of Mountain Research ◽

10.51220/jmr.v14i1.20 ◽

2019 ◽

Vol 14 (1) ◽

Author(s):

Harmeen Kaur ◽

Saurabh Sharma ◽

Alok K. Durgapal

Keyword(s):

Molecular Clouds ◽

Luminosity Function ◽

Open Cluster ◽

Mass Function ◽

Open Clusters ◽

Initial Mass Function ◽

Wide Field ◽

Evolutionary Models ◽

Star Forming ◽

Initial Results

NGC 6910 is located in a Cygnus X region, which is a ∼10◦ complex of actively star forming molecular clouds and young clusters, located at a distance of about 1.7 kpc (Reipurth & Schneider 2008). Open clusters possess many favorable characteristics for initial mass function (IMF) studies. The observed mass function of a star cluster can in principle be determined from the observed luminosity function (LF) using theoretical stellar evolutionary models. Here, we are presenting our initial results related to structure parameters, extinction, distance and mass function of open cluster NGC 6910 based on the deep and wide field mosaic images taken from 1.0m Sampurnand telescope of ARIES, India.

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Structure and Mass Function of Open Cluster NGC 6910

Journal of Mountain Research ◽

10.51220/jmr.v19i1.20 ◽

2019 ◽

Vol 14 (1) ◽

Author(s):

Harmeen Kaur ◽

Saurabh Sharma ◽

Alok K. Durgapal

Keyword(s):

Molecular Clouds ◽

Luminosity Function ◽

Open Cluster ◽

Mass Function ◽

Open Clusters ◽

Initial Mass Function ◽

Wide Field ◽

Evolutionary Models ◽

Star Forming ◽

Initial Results

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A 3D view of the Hyades stellar and sub-stellar population

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834045 ◽

2019 ◽

Vol 623 ◽

pp. A35 ◽

Cited By ~ 8

Author(s):

N. Lodieu ◽

R. L. Smart ◽

A. Pérez-Garrido ◽

R. Silvotti

Keyword(s):

Open Cluster ◽

Infrared Camera ◽

Brown Dwarfs ◽

Mass Function ◽

The Sun ◽

The Core ◽

Cluster Centre ◽

Hyades Cluster ◽

Scientific Goal ◽

Mass Segregation

Aims. Our scientific goal is to provide a 3D map of the nearest open cluster to the Sun, the Hyades, combining the recent release of Gaia astrometric data, ground-based parallaxes of sub-stellar member candidates and photometric data from surveys which cover large areas of the cluster. Methods. We combined the second Gaia release with ground-based H-band parallaxes obtained with the infrared camera on the 2 m robotic Liverpool telescope to astrometrically identify stellar and sub-stellar members of the Hyades, the nearest open cluster to the Sun. Results. We find 1764 objects within 70° radius from the cluster centre from the Gaia second data release, whose kinematic properties are consistent with the Hyades. We limit our study to 30 pc from the cluster centre (47.03 ± 0.20 pc) where we identify 710 candidate members, including 85 and 385 in the core and tidal radius, respectively. We determine proper motions and parallaxes of eight candidate brown dwarf members and confirm their membership. Using the 3D positions and a model-based mass-luminosity relation we derive a luminosity and mass function in the 0.04–2.5 M⊙ range. We confirm evidence for mass segregation in the Hyades and find a dearth of brown dwarfs in the core of the cluster. From the white dwarf members we estimate an age of 640−49+67 Myr. Conclusions. We identify a list of members in the Hyades cluster from the most massive stars down to the brown dwarfs. We produce for the first time a 3D map of the Hyades cluster in the stellar and sub-stellar regimes and make available the list of candidate members.

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The disintegrating old open cluster Czernik 3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2412 ◽

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.

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Physical properties of the star-forming clusters in NGC 6334

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935699 ◽

2020 ◽

Vol 635 ◽

pp. A2 ◽

Cited By ~ 3

Author(s):

M. Sadaghiani ◽

Á. Sánchez-Monge ◽

P. Schilke ◽

H. B. Liu ◽

S. D. Clarke ◽

...

Keyword(s):

Physical Properties ◽

Mass Function ◽

High Mass ◽

Gas Reservoir ◽

Star Forming ◽

The Core ◽

Mass Segregation ◽

Ngc 6334 ◽

Compact Sources ◽

Massive Cores

Aims. We aim to characterise certain physical properties of high-mass star-forming sites in the NGC 6334 molecular cloud, such as the core mass function (CMF), spatial distribution of cores, and mass segregation. Methods. We used the Atacama Large Millimeter/sub-millimeter Array (ALMA) to image the embedded clusters NGC 6334-I and NGC 6334-I(N) in the continuum emission at 87.6 GHz. We achieved a spatial resolution of 1300 au, enough to resolve different compact cores and fragments, and to study the properties of the clusters. Results. We detected 142 compact sources distributed over the whole surveyed area. The ALMA compact sources are clustered in different regions. We used different machine-learning algorithms to identify four main clusters: NGC 6334-I, NGC 6334-I(N), NGC 6334-I(NW), and NGC 6334-E. The typical separations between cluster members range from 4000 au to 12 000 au. These separations, together with the core masses (0.1–100 M⊙), are in agreement with the fragmentation being controlled by turbulence at scales of 0.1 pc. We find that the CMFs show an apparent excess of high-mass cores compared to the stellar initial mass function. We evaluated the effects of temperature and unresolved multiplicity on the derived slope of the CMF. Based on this, we conclude that the excess of high-mass cores might be spurious and due to inaccurate temperature determinations and/or resolution limitations. We searched for evidence of mass segregation in the clusters and we find that clusters NGC 6334-I and NGC 6334-I(N) show hints of segregation with the most massive cores located in the centre of the clusters. Conclusions. We searched for correlations between the physical properties of the four embedded clusters and their evolutionary stage (based on the presence of H II regions and infrared sources). NGC 6334-E appears as the most evolved cluster, already harbouring a well-developed H II region. NGC 6334-I is the second-most evolved cluster with an ultra-compact H II region. NGC 6334-I(N) contains the largest population of dust cores distributed in two filamentary structures and no dominant H II region. Finally, NGC 6334-I(NW) is a cluster of mainly low-mass dust cores with no clear signs of massive cores or H II regions. We find a larger separation between cluster members in the more evolved clusters favouring the role of gas expulsion and stellar ejection with evolution. The mass segregation, seen in the NGC 6334-I and NGC 6334-I(N) clusters, suggests a primordial origin for NGC 6334-I(N). In contrast, the segregation in NGC 6334-I might be due to dynamical effects. Finally, the lack of massive cores in the most evolved cluster suggests that the gas reservoir is already exhausted, while the less evolved clusters still have a large gas reservoir along with the presence of massive cores. In general, the fragmentation process of NGC 6334 at large scales (from filament to clump, i.e. at about 1 pc) is likely governed by turbulent pressure, while at smaller scales (scale of cores and sub-fragments, i.e. a few hundred au) thermal pressure starts to be more significant.

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Synergy of wide-field infrared survey explorer (WISE) and the Sloan Digital Sky Survey in Stripe 82

10.32469/10355/66177 ◽

2018 ◽

Author(s):

◽

Marat Musin

Keyword(s):

Stellar Mass ◽

Sloan Digital Sky Survey ◽

High Mass ◽

Optical Data ◽

Wide Field ◽

Resolution Image ◽

Sky Survey ◽

Template Fitting ◽

Very High ◽

Infrared Survey

In this dissertation, I aim to study the evolution of galaxies over the last 6 Gyr by measuring the growth of the global stellar mass density (GSMD) since z = 0.8. My work combines the datasets from two very large surveys, namely, the optical data from the Sloan Digital Sky Survey (SDSS) Stripe 82 and the infrared data from the Wide-field Infrared Survey Explorer (WISE), and constructs a unique catalog of galaxies that have their spectral energy distributions (SEDs) measured consistently from 0.3 to 5 [mu]m in seven bands. This catalog, the largest of its kind, contains 9 million galaxies in [about] 300 deg[2] , will have a wide range of applications beyond the scope of this thesis. Extending galaxy SED measurements to restframe near-IR has two significant advantages: (1) dust extinction can be better handled, and (2) emissions from low-mass stars, which are the major contributors to a galaxy's stellar mass, can be better measured. WISE was the only mission to date that provided all-sky IR data that are deep enough for galaxy evolution studies out to z [approximately] 1 (sampling restframe K-band). The only wide-field optical survey data that could match WISE depths are those from the SDSS Stripe 82 over [about] 300 deg2 . The synergy of the two is therefore natural. The implementation, however, is of tremendous difficulty. This is mainly because of the vastly different spatial resolutions between SDSS and WISE. To overcome this problem, we take an approach that is often referred to as "morphological template fitting", i.e., using the high-resolution image to define the morphological template of the galaxy in question, and de-convolving its light profile in the low-resolution image accordingly. In this way, we obtain the SED measurements over the entire 0.3-5[mu]m range in the most self-consistent manner. Using this SED catalog as the basis, we derive photometric redshifts and stellar masses for all the 9 million galaxies that span z = 0-0.8. This provides us an unprecedented statistics when deriving galaxy stellar mass functions (MFs) and GSMD over multiple redshift bins. Some preliminary results are discussed. As a by-product of our morphological template fitting process, an interesting population of objects called "WISE Optical Dropouts" ("WoDrops" for short) are discovered. These objects are significant detections in WISE data but are invisible in all the SDSS Stripe 82 data. Their nature remains a mystery up to this point. Among all possibilities, the only viable interpretation is that they are very high-mass galaxies with very high dust extinctions. To reveal their nature, future observations at larger facilities will be necessary.

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Photometric study of the young open clusters IC 1442, King 21, and Trumpler 7

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1370 ◽

2020 ◽

Vol 495 (2) ◽

pp. 2496-2508 ◽

Cited By ~ 1

Author(s):

Jayanand Maurya ◽

Y C Joshi ◽

A S Gour

Keyword(s):

Relaxation Time ◽

Outer Region ◽

Mass Function ◽

Open Clusters ◽

Photometric Study ◽

Proper Motions ◽

Dynamical Study ◽

Data Release ◽

Solar Metallicity ◽

Mass Segregation

ABSTRACT We carried out the UBVRcIc photometric study of three poorly studied young open clusters IC 1442, King 21, and Trumpler 7 (Tr 7). We obtained 263, 244, and 128 member stars using Gaia Data Release 2 proper motions and parallaxes in IC 1442, King 21, and Tr 7, respectively. The reddening, E(B − V), was derived to be 0.54 ± 0.04, 0.76 ± 0.06, and 0.38 ± 0.04 mag for these clusters. The comparison of observed colour–magnitude diagrams with solar metallicity isochrones yields log(age) = 7.40 ± 0.30, 7.70 ± 0.20, and 7.85 ± 0.25 yr and corresponding distances of 2847 ± 238, 2622 ± 156, and 1561 ± 74 pc for IC 1442, King 21, and Tr 7, respectively. The estimated mass function (MF) slopes are found to be −1.94 ± 0.18, −1.54 ± 0.32, and −2.31 ± 0.29 for IC 1442, King 21, and Tr 7, respectively. The study of MF slopes done separately in the inner and the outer regions of these clusters gives a steeper slope in the outer region, which suggests spatial variation in slope and mass segregation in the clusters. We found evidence of mass segregation after the dynamical study in these clusters. The obtained relaxation time, TE, is 74, 26, and 34 Myr for the clusters IC 1442, King 21, and Tr 7, respectively. The mass segregation in IC 1442 may be caused by early dynamical relaxation. The estimated TE is well below the ages of King 21 and Tr 7, which indicates that these clusters are dynamically relaxed.

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