scholarly journals Kernel Density Estimation in the Study of Star Clusters

2016 ◽  
Vol 25 (3) ◽  
Author(s):  
Anton F. Seleznev
Keyword(s):  
Luminosity Function ◽  
Open Cluster ◽  
Cluster Structure ◽  
Star Clusters ◽  
Kernel Estimator ◽  
Mass Function ◽  
Number Density ◽  
Density Profiles ◽  
Density Maps ◽  
Technical Details

AbstractThe kernel estimator method is used to evaluate the surface and spatial star number density in star clusters. Both density maps and radial density profiles are plotted. These estimates are used to derive the cluster size, the number of cluster stars and the cluster mass, and to study the cluster structure. The kernel estimator is also used to plot the luminosity function, mass function, the velocity distribution, and Hess diagrams for star clusters. The advantages of the kernel estimator method and technical details of its use are illustrated by modern results for the open cluster NGC 4337.

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 Structure and Mass Function of Open Cluster NGC 6910

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.

scholarly journals Virial Halo Mass Function in the Planck Cosmology

2021 ◽  
Vol 922 (1) ◽  
pp. 89
Author(s):  
Masato Shirasaki ◽  
Tomoaki Ishiyama ◽  
Shin’ichiro Ando
Keyword(s):  
Luminosity Function ◽  
Mass Function ◽  
Number Density ◽  
Baseline Model ◽  
Wide Range ◽  
Halo Masses ◽  
Number Counts ◽  
Mass Functions ◽  
Analytic Prediction ◽  
Fitting Parameters

Abstract We study halo mass functions with high-resolution N-body simulations under a ΛCDM cosmology. Our simulations adopt the cosmological model that is consistent with recent measurements of the cosmic microwave backgrounds with the Planck satellite. We calibrate the halo mass functions for 108.5 ≲ M vir/(h −1 M ⊙) ≲ 1015.0–0.45 z , where M vir is the virial spherical-overdensity mass and redshift z ranges from 0 to 7. The halo mass function in our simulations can be fitted by a four-parameter model over a wide range of halo masses and redshifts, while we require some redshift evolution of the fitting parameters. Our new fitting formula of the mass function has a 5%-level precision, except for the highest masses at z ≤ 7. Our model predicts that the analytic prediction in Sheth & Tormen would overestimate the halo abundance at z = 6 with M vir = 108.5–10 h −1 M ⊙ by 20%–30%. Our calibrated halo mass function provides a baseline model to constrain warm dark matter (WDM) by high-z galaxy number counts. We compare a cumulative luminosity function of galaxies at z = 6 with the total halo abundance based on our model and a recently proposed WDM correction. We find that WDM with its mass lighter than 2.71 keV is incompatible with the observed galaxy number density at a 2σ confidence level.

scholarly journals Structure and Mass Function of Open Cluster NGC 6910

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

scholarly journals Complex Stellar System ESO65SC03: Open Cluster or Remnant?

2015 ◽  
Vol 32 ◽  
Author(s):  
Gireesh C. Joshi ◽  
Y. C. Joshi ◽  
S. Joshi ◽  
S. Chowdhury ◽  
R. K. Tyagi
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Open Cluster ◽  
Stellar System ◽  
Mass Function ◽  
Distance Modulus ◽  
Number Density ◽  
Main Sequence Stars ◽  
Dynamical Study ◽  
The Mean

AbstractWe present a complete spatial and dynamical study of the poorly populated stellar system ESO65SC03. The radial distribution of the system gives a core and cluster radii of 1.10±0.63 and 5.36±0.24 arcmin, respectively. The SNDP does not show any clear enhancement of the surface stellar number density between the stars of the system and the field regions. We derive the optimum isochrone solution for a particular grid size in the CMD using the statistical cleaning procedure. Using the statistically cleaned CMDs, we find the distance modulus, (m − M)0, and reddening, E(B − V), of the system to be 11.8±0.2 and 0.45 mag, respectively. The mean proper motion of this system is − 5.37±0.81 mas yr−1 and 0.31±0.40 in RA and DEC directions, respectively. The mean proper motion of this system is found to be almost similar to the field region. The mass function for the brighter stars is found to be too high for the system to be an open cluster. These combined results place constraints on whether stellar system ESO65SC03 is a POCR or an Asterism. Our understanding is that the ESO65SC03 is in a stage of POCR by losing their main-sequence stars in the dynamic evolution processes.

scholarly journals A Physical Model for the Quasar Luminosity Function Evolution between Cosmic Dawn and High Noon

2021 ◽  
Vol 923 (1) ◽  
pp. 110
Author(s):  
Keven Ren ◽  
Michele Trenti
Keyword(s):  
Duty Cycle ◽  
Free Parameter ◽  
Luminosity Function ◽  
Mass Function ◽  
Model Parameters ◽  
Data Sets ◽  
Mass Relation ◽  
Semiempirical Model ◽  
Number Density ◽  
Model Predictions

Abstract Modeling the evolution of the number density distribution of quasars through the quasar luminosity function (QLF) is critical to improving our understanding of the connection between black holes, galaxies, and their halos. Here we present a novel semiempirical model for the evolution of the QLF that is fully defined after the specification of a free parameter, the internal duty cycle, ε DC, along with minimal other assumptions. All remaining model parameters are fixed upon calibration against the QLF at two redshifts, z = 4 and z = 5. Our modeling shows that the evolution at the bright end results from the stochasticity in the median quasar luminosity versus halo mass relation, while the faint end shape is determined by the evolution of the halo mass function (HMF) with redshift. Additionally, our model suggests the overall quasar density is determined by the evolution of the HMF, irrespective of the value of ε DC. The z ≥ 4 QLFs from our model are in excellent agreement with current observations for all ε DC, with model predictions suggesting that observations at z ≳ 7.5 are needed to discriminate between different ε DC. We further extend the model at z ≤ 4, successfully describing the QLF between 1 ≤ z ≤ 4, albeit with additional assumptions on Σ and ε DC. We use the existing measurements of quasar duty cycle from clustering to constrain ε DC, finding ε DC ∼ 0.01 or ε DC ≳ 0.1 dependent on observational data sets used for reference. Finally, we present forecasts for future wide-area surveys with promising expectations for the Nancy Grace Roman Telescope to discover N ≳ 10, bright, m UV < 26.5 quasars at z ∼ 8.

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