scholarly journals 3D Parameter Maps of Red Clump Stars in the Milky Way: Absolute Magnitudes and Intrinsic Colors

2021 ◽  
Vol 923 (2) ◽  
pp. 145
Author(s):  
Shu Wang ◽  
Xiaodian Chen
Keyword(s):  
Three Dimensional ◽  
Gaussian Process Regression ◽  
Absolute Magnitude ◽  
Accurate Estimation ◽  
Systematic Bias ◽  
Chemical Abundances ◽  
Internal Validation ◽  
Red Clump ◽  
Absolute Magnitudes ◽  
Astrometric Data

Abstract Red clump stars (RCs) are useful tracers of distances, extinction, chemical abundances, and Galactic structures and kinematics. Accurate estimation of RC parameters—absolute magnitude and intrinsic color—is the basis for obtaining high-precision RC distances. By combining astrometric data from Gaia; spectroscopic data from APOGEE and LAMOST; and multiband photometric data from Gaia, APASS, Pan-STARRS1, 2MASS, and WISE surveys, we use a Gaussian process regression to train machine learners to derive the multiband absolute magnitudes M λ and intrinsic colors ( λ 1 − λ 2 ) 0 for each spectral RC. The dependence of M λ on metallicity decreases from optical to infrared bands, while the dependence of M λ on age is relatively similar in each band. ( λ 1 − λ 2 ) 0 are more affected by metallicity than age. The RC parameters are not suitable to be represented by simple constants but are related to the Galactic stellar population structure. By analyzing the variation of M λ and ( λ 1 − λ 2 ) 0 in the spatial distribution, we construct (R, z) dependent maps of mean absolute magnitudes and mean intrinsic colors of the Galactic RCs. Through external and internal validation, we find that using three-dimensional (3D) parameter maps to determine RC parameters avoids systematic bias and reduces dispersion by about 20% compared to using constant parameters. Based on Gaia's EDR3 parallax, our 3D parameter maps, and extinction–distance profile selection, we obtain a photometric RC sample containing 11 million stars with distance and extinction measurements.

scholarly journals Gaia DR2 giants in the Galactic dust – I. Reddening across the whole dust layer and some properties of the giant clump

2020 ◽  
Vol 500 (2) ◽  
pp. 2590-2606 ◽  
Author(s):  
George A Gontcharov ◽  
Aleksandr V Mosenkov
Keyword(s):  
Absolute Magnitude ◽  
Wide Field ◽  
The Sun ◽  
Theoretical Predictions ◽  
Red Giant Clump ◽  
Red Clump ◽  
Red Giant ◽  
Absolute Magnitudes ◽  
Gaia Dr2 ◽  
Vertical Gradients

ABSTRACT We consider a complete sample of 101 810 giants with Gaia Data Realease 2 (DR2) parallaxes ϖ within the red clump domain of the Hertzsprung–Russell diagram in the space cylinder with a radius of 700 pc around the Sun and a height of |Z| = 1800 pc. We use the Gaia DR2 GBP, GRP, and Wide-field Infrared Survey Explorer W3 photometry. We describe the spatial variations of the modes of the observables GBP − GRP, GRP − W3, $G_\mathrm{BP}+5+5\, \log _{10}\varpi$, $G_\mathrm{RP}+5+5\, \log _{10}\varpi$, and $W3+5+5\, \log _{10}\varpi$ by extinction and reddening in combination with linear vertical gradients of the intrinsic colours and absolute magnitudes of the red giant clump. The derived clump median absolute magnitude in W3 agrees with its recent literature estimates. The clump median intrinsic colours and absolute magnitudes in GBP and GRP are derived for the first time at a precision level of 0.01 mag. We confirm the reliability of the derived clump absolute magnitudes, intrinsic colours, and their vertical gradients by comparing them with the theoretical predictions from the PAdova and TRieste Stellar Evolution Code, MESA Isochrones and Stellar Tracks, and Bag of Stellar Tracks and Isochrones. This leads us to the median age and [Fe/H] of the clump within |Z| < 1.7 kpc from the Galactic mid-plane as $(2.3\pm 0.5)+(3.2\pm 1.6)\, |Z|$ Gyr and $(-0.08\pm 0.08)-(0.16\pm 0.07)\, |Z|$ dex, respectively, where Z is expressed in kpc. These results agree with recent empirical and theoretical estimates. Moreover, all the models give similar age–metallicity relations by use of our results in the optical range. The derived extinctions and reddenings across the whole dust half-layer below or above the Sun converge to the reddening E(B − V) = 0.06 mag by use of the most reliable extinction laws.

scholarly journals Empirical photometric calibration of the Gaia red clump: Colours, effective temperature, and absolute magnitude

2018 ◽  
Vol 609 ◽  
pp. A116 ◽  
Author(s):  
L. Ruiz-Dern ◽  
C. Babusiaux ◽  
F. Arenou ◽  
C. Turon ◽  
R. Lallement
Keyword(s):  
Effective Temperature ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Red Giants ◽  
Photometric Calibration ◽  
Empirical Calibration ◽  
Data Release ◽  
Red Clump ◽  
Red Giant ◽  
Absolute Magnitudes

Context. Gaia Data Release 1 allows the recalibration of standard candles such as the red clump stars. To use those stars, they first need to be accurately characterised. In particular, colours are needed to derive interstellar extinction. As no filter is available for the first Gaia data release and to avoid the atmosphere model mismatch, an empirical calibration is unavoidable. Aims. The purpose of this work is to provide the first complete and robust photometric empirical calibration of the Gaia red clump stars of the solar neighbourhood through colour–colour, effective temperature–colour, and absolute magnitude–colour relations from the Gaia, Johnson, 2MASS, Hipparcos, Tycho-2, APASS-SLOAN, and WISE photometric systems, and the APOGEE DR13 spectroscopic temperatures. Methods. We used a 3D extinction map to select low reddening red giants. To calibrate the colour–colour and the effective temperature–colour relations, we developed a MCMC method that accounts for all variable uncertainties and selects the best model for each photometric relation. We estimated the red clump absolute magnitude through the mode of a kernel-based distribution function. Results. We provide 20 colour versus G−Ks relations and the first Teff versus G−Ks calibration. We obtained the red clump absolute magnitudes for 15 photometric bands with, in particular, MKs = (−1.606 ± 0.009) and MG = (0.495 ± 0.009) + (1.121 ± 0.128)(G−Ks−2.1). We present a dereddened Gaia-TGAS HR diagram and use the calibrations to compare its red clump and its red giant branch bump with Padova isochrones.

scholarly journals The Absolute Magnitude of the Early-Type MK Standards From Hipparcos Parallaxes

1998 ◽  
Vol 11 (1) ◽  
pp. 566-566
Author(s):  
C. Jaschek ◽  
A.E. Gómez
Keyword(s):  
Main Sequence ◽  
Rotational Velocity ◽  
Wide Band ◽  
Absolute Magnitude ◽  
Interstellar Extinction ◽  
Early Type ◽  
Class V ◽  
Luminosity Class ◽  
The Absolute ◽  
Absolute Magnitudes

We have analysed the standards of the MK system in the B0-F5 spectral region with the help of Hipparcos parallaxes, using only stars for which the error on the absolute magnitude is ≤ 0.3 mag. The sample stars (about one hundred) were scrutinized for companions and for interstellar extinction. We find that the main sequence is a wide band and that, although in general giants and dwarfs have different absolute magnitudes, the separation between luminosity class V and III is not clear. We conclude that there is no strict relation between luminosity class and absolute magnitude. The relation is only a statistical one and has a large intrinsic dispersion. We have analysed similarly the system of standards defined by Garrison and Gray (1994) separating low and high rotational velocity standards. We find similar effects as in the original MK system.

Automatic weaving method for three-dimensional composite preforms using vision system

2021 ◽  
pp. 004051752098238
Author(s):  
Siyuan Li ◽  
Zhongde Shan ◽  
Dong Du ◽  
Li Zhan ◽  
Zhikun Li ◽  
...  
Keyword(s):  
Relative Position ◽  
Vision System ◽  
Estimation Error ◽  
Three Dimensional ◽  
Fiber Reinforced Composites ◽  
Accurate Estimation ◽  
Digital Manufacturing ◽  
Relative Rotation ◽  
Reinforced Composites ◽  
Main Structure

Three-dimensional composite preform is the main structure of fiber-reinforced composites. During the weaving process of large-sized three-dimensional composite preform, relative rotation or translation between the fiber feeder and guided array occurs before feeding. Besides, the weaving needles can be at different heights after moving out from the guided array. These problems are mostly detected and adjusted manually. To make the weaving process more precise and efficient, we propose machine vision-based methods which could realize accurate estimation and adjustment of the relative position-pose between the fiber feeder and guided array, and make the needles pressing process automatic by recognizing the position of the weaving needles. The results show that the estimation error of relative position-pose is within 5%, and the rate of unrecognized weaving needles is 2%. Our proposed methods improve the automation level of weaving, and are conducive to the development of preform forming toward digital manufacturing.

scholarly journals Structure and dynamics of the Milky Way disk as revealed from the radial velocity distributions of APOGEE red clump stars

2016 ◽  
Vol 11 (S321) ◽  
pp. 50-50
Author(s):  
Daisuke Toyouchi ◽  
Masashi Chiba
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Radial Velocities ◽  
Galactocentric Distance ◽  
Chemical Abundances ◽  
Structure And Dynamics ◽  
Evolution Experiment ◽  
Dynamical Properties ◽  
Red Clump ◽  
Independent Work

AbstractWe investigate the structure and dynamics of the Milky Way (MW) disk stars based on the analysis of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) data, to infer the past evolution histories of the MW disk component(s) possibly affected by radial migration and/or satellite accretions. APOGEE is the first near-infrared spectroscopic survey for a large number of the MW disk stars, providing their radial velocities and chemical abundances without significant dust extinction effects. We here adopt red-clump (RC) stars (Bovy et al. 2014), for which the distances from the Sun are determined precisely, and analyze their radial velocities and chemical abundances in the MW disk regions covering from the Galactocentric distance, R, of 5 kpc to 14 kpc. We investigate their dynamical properties, such as mean rotational velocities, 〈Vφ〉 and velocity dispersions, as a function of R, based on the MCMC Bayesian method. We find that at all radii, the dynamics of alpha-poor stars, which are candidates of young disk stars, is much different from that of alpha-rich stars, which are candidates of old disk stars. We find that our Jeans analysis for our sample stars reveals characteristic spatial and dynamical properties of the MW disk, which are generally in agreement with the recent independent work by Bovy et al. (2015) but with a different method from ours.

Automated Pancreas Segmentation And Volumetry Using Deep Neural Network On Computed Tomography

2021 ◽  
Author(s):  
Sang-Heon Lim ◽  
Young Jae Kim ◽  
Yeon-Ho Park ◽  
Doojin Kim ◽  
Kwang Gi Kim ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Deep Learning ◽  
Automatic Segmentation ◽  
External Validation ◽  
Three Dimensional ◽  
Semantic Segmentation ◽  
Quantitative Information ◽  
Similarity Coefficients ◽  
Internal Validation ◽  
Pancreas Segmentation

Abstract Pancreas segmentation is necessary for observing lesions, analyzing anatomical structures, and predicting patient prognosis. Therefore, various studies have designed segmentation models based on convolutional neural networks for pancreas segmentation. However, the deep learning approach is limited by a lack of data, and studies conducted on a large computed tomography dataset are scarce. Therefore, this study aims to perform deep-learning-based semantic segmentation on 1,006 participants and evaluate the automatic segmentation performance of the pancreas via four individual three-dimensional segmentation networks. In this study, we performed internal validation with 1,006 patients and external validation using the Cancer Imaging Archive (TCIA) pancreas dataset. We obtained mean precision, recall, and dice similarity coefficients of 0.869, 0.842, and 0.842, respectively, for internal validation via a relevant approach among the four deep learning networks. Using the external dataset, the deep learning network achieved mean precision, recall, and dice similarity coefficients of 0.779, 0.749, and 0.735, respectively. We expect that generalized deep-learning-based systems can assist clinical decisions by providing accurate pancreatic segmentation and quantitative information of the pancreas for abdominal computed tomography.

scholarly journals The Luminosity Determination

1995 ◽  
Vol 10 ◽  
pp. 399-402
Author(s):  
A.E. Gómez ◽  
C. Turon
Keyword(s):  
Main Sequence ◽  
Small Volume ◽  
Absolute Magnitude ◽  
Fitting Procedure ◽  
Trigonometric Parallaxes ◽  
The Mean ◽  
The Absolute ◽  
Absolute Magnitudes ◽  
Kinematical Data ◽  
Magnitude Determination

The Hertzprung-Russel (HR) diagram luminosity calibration relies basically on three kinds of data: trigonometric parallaxes, kinematical data (proper motions and radial velocities) and cluster distances obtained by the zero-age main sequence fitting procedure. The most fundamental method to calculate the absolute magnitude is the use of trigonometric parallaxes, but up to now, accurate data only exist for stars contained in a small volume around the sun. Individual absolute magnitudes are obtained using trigonometric parallaxes or photometric and spectroscopic calibrations. In these calibrations the accuracy on the absolute magnitude determination ranges from ±0.m2 in the main sequence to ±0m5 in the giant branch. On the other hand, trigonometric parallaxes, kinematical data or cluster distances have been used to make statistical calibrations of the absolute magnitude. The standard error on the mean absolute magnitude calibrations ranges from ±0m3 to ±0m6 on the mean sequence, from ±0m5 to ±0m7 on thegiant branch and is of about 1mfor supergiants.Future improvements in the absolute magnitude determination will depend on the improvement of the basic data from the ground and space. A brief overview of the new available data is presented. In particular, the analysis of the first 30 months data of the Hipparcos mission (H30) (from the 37 months data of the whole mission) allows to perform a statistical evaluation of the improvements expected in the luminosity determination.

scholarly journals Local Stellar Kinematics from RAVE data—VII. Metallicity Gradients from Red Clump Stars

2016 ◽  
Vol 33 ◽  
Author(s):  
Ö. Önal Taş ◽  
S. Bilir ◽  
G. M. Seabroke ◽  
S. Karaali ◽  
S. Ak ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Milky Way ◽  
Absolute Magnitude ◽  
Selection Effects ◽  
Stellar Kinematics ◽  
Experiment Data ◽  
Radial Gradient ◽  
Data Release ◽  
The Difference ◽  
Red Clump

AbstractWe investigate the Milky Way Galaxy’s radial and vertical metallicity gradients using a sample of 47 406 red clump stars from the RAdial Velocity Experiment Data Release 4. Distances are calculated by adopting Ks-band absolute magnitude as −1.54±0.04 mag for the sample. The metallicity gradients are calculated with their current orbital positions (Rgc and Z) and with their orbital properties (Rm and zmax): d[Fe/H]/dRgc = −0.047±0.003 dex kpc−1 for |Z| ≤ 0.5 kpc and d[Fe/H]/dRm = −0.025±0.002 dex kpc−1 for zmax ≤ 0.5 kpc. This reaffirms the radial metallicity gradient in the thin disc but highlights that gradients are sensitive to the selection effects caused by the difference between Rgc and Rm. The radial gradient is flat in the distance interval 0.5-1 kpc from the plane and then becomes positive greater than 1 kpc from the plane. The radial metallicity gradients are also eccentricity dependent. We showed that d[Fe/H]/dRm = −0.089±0.010, −0.073±0.007, −0.053±0.004 and −0.044±0.002 dex kpc−1 for ep ≤ 0.05, ep ≤ 0.07, ep ≤ 0.10 and ep ≤ 0.20 sub-samples, respectively, in the distance interval zmax ≤ 0.5 kpc. Similar trend is found for vertical metallicity gradients. Both the radial and vertical metallicity gradients are found to become shallower as the eccentricity of the sample increases. These findings can be used to constrain different formation scenarios of the thick and thin discs.

“A NOVEL ATTEMPT IN ESTIMATION OF FETAL WEIGHT USING NEW SOFT TISSUE MEASUREMENTS”

2021 ◽  
pp. 1-3
Author(s):  
Sathyan Gnanasigamani ◽  
Sudhakar Vadivel ◽  
Bala Subramaniam ◽  
Sakthivel Raja Ganesan ◽  
Pradeebaa Thiyagarajan ◽  
...  
Keyword(s):  
Birth Weight ◽  
Soft Tissue ◽  
Strong Predictor ◽  
Three Dimensional ◽  
Fetal Weight ◽  
Ultrasound Measurement ◽  
Accurate Estimation ◽  
Tissue Thickness ◽  
Third Trimester ◽  
Soft Tissue Thickness

Background: The Accurate estimation of fetal weight is important in modern obstetrics. Currently, Hadlock's formula is used widely for fetal weight estimation, which includes BPD, AC, FL and HC. The correct plane of measurement of various standard parameters is difcult to obtain especially in third trimester. Hence soft tissue thicknesses of the fetus are tested for correlation with birth weight in this study. Materials & Methods: A prospective observational study conducted among 90 pregnant females referred for Ultrasound examination in the third trimester with an interval from the ultrasound scan to delivery of ≤7 days from 2019 to 2020. Results: The measurements of abdominal, fetal mid-thigh and mid-arm soft tissue thicknesses correlated well with birth weight in a high statistically signicant positive linear relationship. A new regression model developed out of the soft tissue thicknesses(FASTT, FMASTT, FTSTT) correlates better than the Hadlock's model and Sujitkumar Hiwale et al model (For Indian population) based on BPD, HC, AC and FL Conclusion: Ultrasound measurement of soft tissue thickness may prove to be a strong predictor of fetal weight essential for sonographic assessment of pregnancy. They are easy and simple hence fetal soft tissue thickness measurements, both two- and three-dimensional, may prove to be a diagnostic parameter that has as small an error rate as possible, is quick to use and reproducible by different examiners

scholarly journals Hipparcos Positions of B/Be Stars on the HR Diagram

2000 ◽  
Vol 175 ◽  
pp. 117-128 ◽  
Author(s):  
Danielle Briot ◽  
Noel Robichon
Keyword(s):  
Spectral Type ◽  
Rotational Velocity ◽  
Absolute Magnitude ◽  
Be Stars ◽  
Class V ◽  
B Stars ◽  
Luminosity Class ◽  
The Mean ◽  
Absolute Magnitudes ◽  
Hipparcos Parallax

AbstractAbsolute magnitudes of Be and B stars are computed for each spectral type and luminosity class V and IV, using the Hipparcos parallax measurements. Some simulations have been carried out in order to estimate the effects which could bias the mean absolute magnitude calculations. As a result, only stars with σπ/π < 15% have been used. A first result is that B stars are fainter than previous estimations by about 0.5 magnitude on average. We then observe that on average Be stars are brighter than B stars of the same spectral type and this over-luminosity increases with the spectral type. A possible interpretation is proposed based on the fact that the rotational velocity of the late Be stars is near the critical rotational velocity.

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