Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3

view Abstract Citations (46) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Integrated magnItudes and mean colors of DDO dwarf galaxies in the UBV system. II. Distances, luminosities, and HI properties. de Vaucouleurs, G. ; de Vaucouleurs, A. ; Buta, R. Abstract An analysis of the properties of the DDO magellanic irregular "dwarf" galaxies for which U, B, V photometry was reported in Paper I leads to the following conclusions: (1) The mean effective surface brightness (m'e)0 varies with zenith distance as expected from the dependence on sec z of atmospheric extinction and sky brightness. (2) The mean surface brightness is independent of distance modulus (25 < μ0 < 33). (3) The mean absolute magnitude M0T is brighter than average (and the mean effective linear diameter larger) south of +10° declination (dwarfs fainter than -15 are missing) and fainter near the zenith at Palomar. There is a curious near absence of DDO objects in the zone +20° < δ < + 30°. The range of absolute magnitudes (-19 < M0T < -12) is largest north of +60° declination. (4) The mean corrected effective color index (U - V )0e is independent of absolute magnitude at M 0T < -15, but fainter systems tend to be bluer. (5) The mean absolute magnitude M0T is correlated with distance modulus at μ0 > 28; we confirm that the DDO sample is not restricted to dwarf systems and includes galaxies as bright as M0T <∼ -18 at μ0 > 30.(6) We confirm also that the luminosity class L and luminosity index Λ are not valid indicators of absolute magnitude for late-type systems beyond μ0 ≃ (Δ = 4 Mpc). (7) Effective linear diameter and absolute magnitude are highly correlated (i.e., mean surface brightness is not a distance indicator). (8) Apparent magnitude and 21-cm line flux are loosely correlated, but there is a large range of HI index (hydrogen/luminosity ratio) among the DDO objects at a given Hubble type (Sd to Im). (9) The relative excess or deficiency in hydrogen/luminosity ratio is uncorrelated with mean effective surface brightness (except for selection effects). (10) The hydrogen/luminosity ratio residuals (at a given type) are loosely correlated with color residuals: DDO objects richer than average in neutral hydrogen tend to be bluer in (U - V )0e (11) The necessity of correcting H I linewidths for velocity dispersion is once again demonstrated by the conspicuous departure from linearity of the Tully-Fisher relation based on raw linewidths. Correction for turbulent motions restores the linearity of the relation. For want of reliable inclination estimates for individual objects a statistical correction depending on the log axis ratio log R is applied. (12) The derived T - F relation for the DDO sample of late-type systems is in near perfect agreement in slope and zero point with the relation adopted by Bottinelli et al. for normal spiral galaxies of earlier types. The distance moduli derived from the 21-cm linewidths are in good statistical agreement with moduli derived from group membership and redshift but with a larger scatter. (13) The supergalactic anisotropy of the velocity-distance relation is in evidence in the DDO sample, confirming the departures from the ideal Hubble law indicated by earlier studies of brighter spiral galaxies. Publication: The Astronomical Journal Pub Date: June 1983 DOI: 10.1086/113365 Bibcode: 1983AJ.....88..764D Keywords: Dwarf Galaxies; H Lines; Magellanic Clouds; Ubv Spectra; Brightness Distribution; Centimeter Waves; Color; Distance; Hubble Diagram; Luminosity; Magnitude; Radial Velocity; Spectral Line Width; Spiral Galaxies; Astrophysics full text sources ADS | data products SIMBAD (243) NED (236)

The luminosity distance in the standard cosmology as given by ΛCDM and, consequently, the distance modulus for supernovae can be defined by the Padé approximant. A comparison with a known analytical solution shows that the Padé approximant for the luminosity distance has an error of 4 % at redshift = 10 . A similar procedure for the Taylor expansion of the luminosity distance gives an error of 4 % at redshift = 0 . 7 ; this means that for the luminosity distance, the Padé approximation is superior to the Taylor series. The availability of an analytical expression for the distance modulus allows applying the Levenberg–Marquardt method to derive the fundamental parameters from the available compilations for supernovae. A new luminosity function for galaxies derived from the truncated gamma probability density function models the observed luminosity function for galaxies when the observed range in absolute magnitude is modeled by the Padé approximant. A comparison of ΛCDM with other cosmologies is done adopting a statistical point of view.

Context. The Tycho-Gaia Astrometric Solution (TGAS) subset of the first Gaia catalogue contains an unprecedented sample of proper motions and parallaxes for two million stars brighter than G ~ 12 mag. Aims. We take advantage of the full astrometric solution available for those stars to identify the members of known open clusters and compute mean cluster parameters using either TGAS or the fourth U.S. Naval Observatory CCD Astrograph Catalog (UCAC4) proper motions, and TGAS parallaxes. Methods. We apply an unsupervised membership assignment procedure to select high probability cluster members, we use a Bayesian/Markov Chain Monte Carlo technique to fit stellar isochrones to the observed 2MASS JHKS magnitudes of the member stars and derive cluster parameters (age, metallicity, extinction, distance modulus), and we combine TGAS data with spectroscopic radial velocities to compute full Galactic orbits. Results. We obtain mean astrometric parameters (proper motions and parallaxes) for 128 clusters closer than about 2 kpc, and cluster parameters from isochrone fitting for 26 of them located within a distance of 1 kpc from the Sun. We show the orbital parameters obtained from integrating 36 orbits in a Galactic potential.

The Schmidt method for constructing the luminosity function of galaxies is generalized to include the dependence of the density of galaxies on distance in the near universe. The logarithmic luminosity function (LLF) of the field galaxies as a function of morphological type is constructed. It is found that the LLF for all the galaxies, as well as separately for elliptical and lenticular galaxies, can be represented as a Schechter function within a narrow range of absolute magnitudes. The LLF for spiral galaxies is a Schechter function over a rather wide range of absolute magnitudes, −21.0 ≤ M ≤ −14 . The parameter M* varies little over the spiral galaxies. The parameter α in the Schechter function decreases on going from early to later spirals. On going from elliptical to lenticular galaxies, from early spiral galaxies and onward to later spiral galaxies, a decrease in the average luminosity of the galaxies is observed in the bright end, −23 ≤ M ≤ −17.8 . The completeness and average density of the samples are estimated for galaxies of different morphological types. The average number density of all the galaxies within the range −23 ≤ M ≤ −13 is 0.126 Mpc-3.

view Abstract Citations (18) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Hyades Distance Modulus from Trigonometric Parallaxes From Northern and Southern Hemisphere Observatories Patterson, Richard J. ; Ianna, Philip A. Abstract New trigonometric parallaxes of high precision are presented for 10 members of the Hyades. Independent measurements of the parallax of each star were made at Leander McCormick and Mount Stromlo Observatories. No evidence for a statistically significant difference between the parallaxes obtained at the two observatories is found. The eighteen parallaxes (ten stars) with the greatest precision yield a weighted distance modulus of 3m.l8±0m.09. Publication: The Astronomical Journal Pub Date: September 1991 DOI: 10.1086/115935 Bibcode: 1991AJ....102.1091P Keywords: Astronomical Observatories; Northern Hemisphere; Southern Hemisphere; Stellar Parallax; Trigonometric Functions; Hubble Constant; Open Clusters; Astronomy; ASTROMETRY full text sources ADS | data products SIMBAD (14)

Spectroscopic and photometric data for 23 faint-compact UV-excess galaxy candidates, found by Haro's three-color technique (1956), are presented. Eighteen were found to be emission-line galaxies (magnitudes between 14.4 and 17.9) with redshifts in the range of 1670 to 39,450 km/s; the remaining five appear to be stars. The apparent compactness of the galaxy images is a result of the finite resolution of the Survey plates. Faint Haro galaxies are not distinguishable from the original Haro galaxies in surface brightness or in their range of color and absolute magnitude. The Haro galaxies correspond to roughly two-thirds of Huchra's non-Seyfert Markarian galaxies (1977 a) which have the most negative (U-B) index; the new Haro galaxies have the same V magnitude growth with aperture, the same (B-V) aperture relation, and the same mean surface brightness as the Markarian galaxies.

Cartesian galactic coordinates have been calculated for those Mira type variable stars whose visual (mean) maxima magnitudes were available, down to distance moduli 11 m· 0 inclusively. The latter are determined from the period-luminosity relations for long and short period Miras, respectively, as derived by Ferrari (1973, 1976, 1977) from Clayton & Feast’s statistical parallaxes (1969), with the additional assumption that short period Miras are subject to overtone pulsations: formulas (1) and (2).In the more recent analysis by Foy et alii (1975) we do not find any reason to abandon the outlines of our concept, since his results for the overwhelming majority of Mira-stars sufficiently agree with C l a y t on & Feast’s, last but not least in the confirmation of the uniqueness of the visual luminosity-period relation for M-type Miras regardless of the intensity of OH-features in their spectra. As to the rather poor group of stars with periods from 150 to 200 days, we prefer Clayton & Feast’s mean value, since it is based on a considerably greater sample than Foy’s. But, in our opinion, the natural demarcation line between both branches of the period-luminosity relation must be drawn at about 160 days (instead of 150 days), including the possibility that they overlap in a small realm between 160 and 170 days.The X, Y, Z coordinates (in pc) of the present catalogue are calculated with the assumption that interstellar absorption depends only on distance and galactic latitude according to formula (3). Under the headings I, II, III logarithmical reductions Δlog10R to three other models of absorption are added. Cases I and II: superimposed density waves of absorbing material parallel to our neighbouring spiral arms are assumed. Case I: maxima of absorption being centered amidst the bright spiral arms with amplitude ± 55 percent of the mean value. Case II: maxima of absorption at the inner edges of the spiral arms with amplitude ± 50 percent of the mean value (Cf.: Ferrari & Jenkner, 1973, but with slightly different coefficients of absorption). Case III: Van Herk’s absorption formula (4). The remarks in the last column of this catalogue are concerned with the occurrence of rare spectral types: C (including the obsolete types R and N), K-M, or S. For the latter ones, distance corrections according to Foy’s result that they are overluminous by 0 m· 3 are given in Table 4. With “E ? ” we have denoted a few stars with periods from 160 to 170 days, tentatively treated according to formula (2), while the same, if treated according to formula (1) in most cases would fall beyond the limiting distance modulus 11 m· 0.In order to complete the basic material for the statistics of periods in a clearly defined volume of space, we formed an additional list of those photographically observed Miras which have, most probably, distance moduli smaller than 11 m· 0. Since the latter, individually, sometimes might be rather uncertain, instead the apparent photographic magnitudes of maxima and, for statistical purposes only, rough (Z)-coordinates in fractions of kiloparsec from our unpublished working catalogue are given.Period frequencies have been counted in ten-day intervals, and smoothed out according to formula (5) for Miras of spectral type M,inside and outside the arbitrarily chosen planes of demarcation |Z| = 250 pc (Table 5). The most remarkable feature there is the fact that several more or less pronounced maxima of frequency are located, as far as one can see it, around precisely the same period values in both populations, notwithstanding great differences in the relative heights of corresponding maxima here and there. This observation is opposite to the assumption that the often stressed difference of the mean periods of “disc” and “halo” populations be the result of a general evolutionary trend of periods growing gradually shorter in individual stars when leaving the regions of their origin in the galactic disc.The problem of the physical meaning of distinct groups of Miras according to period could not be cleared up by the selection of such close pairs of Miras which, according to the rules of probability, might be considered as physically connected. Even in these rare cases, ratios of periods as low as 0.78 are found.

view Abstract Citations (720) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Main-sequence photometry, color-magnitude diagrams, and ages for the globular clusters M3, M13, M15 and M92. Sandage, A. Abstract New photoelectric photometry is reported for four globular clusters. Distance moduli were found by using nearby field subdwarfs with trigonometric parallaxes for calibration, with account taken of the ultraviolet excess. If one excludes M13, whose RR Lyrae stars may be related to the asymptotic branch rather than the horizontal branch, the RR Lyrae stars in M3, MiS, and M92 have (4iv) +0.6 + 0.2 by this method. The mean is close to values obtained by Woolley et at. and van Herk from statistical parallaxes, and by Christy from pulsation theory. Christy's calculations of absolute magnitudes are consistent with the Oosterhoff-Sawyer effect, and are adopted as a more precise method to obtain luminosities at the termination of the main sequence. Final adopted moduli are (ni - )o,Mi = 14.83, (m - AI)Av,M13 = 14.42, (m - I) = 14.93, and (m - I)Av,M6i = 14.63, where the subscripts zero and A V mean true and apparent visual moduli, respectively. The adopted turnoff luminosities and the helium and metal abundances used for age dating are listed in a table. Ages calculated from Iben and Rood's models average 11.5 X l0 years and have a very small spread. Ages from models by Demarque et at. are about 20 percent smaller. These ages show no major conflict with limits for the Friedmann time of the expanding Universe when the present uncertainties in the Hubble constant and the deceleration parameter are considered. The wel known correlation of the Oosterhoff-Sawyer period-groups with metal ahundance is shown to be a natural consequence of the prediction of Simoda and Iben that for clusters of equal age, those with lower metal abundance have brighter luminosities at main-sequence turnoff. The observations and theory are combined to show that the most probable age spread among the four clusters is A%/ 0.014 or AT 1.5 X 108 years as required in the rapid-collapse picture of the Galaxy discussed by Eggen, Lynden-Bell, and Sandage. But the limiting error of the result is high, and permits limits of about AT l0 years for the age spread. Representative points of the C-M diagrams for the four clusters are tabulated in the Appendix. Publication: The Astrophysical Journal Pub Date: December 1970 DOI: 10.1086/150715 Bibcode: 1970ApJ...162..841S full text sources ADS | data products SIMBAD (108) GCPD (1)

Validating and improving the correction of ocular artifacts in electro-encephalography

This study compares the performance of K-Nearest Neighbors (KNN) using different distance metrics—Euclidean, Manhattan, and Minkowski—as well as the standalone Euclidean distance metric in facial recognition tasks. Our objective was to compare these methods in terms of accuracy and computational efficiency across diverse datasets, including Celebrity Faces, Color FERET, Family Faces with and without occlusions, and Yale Faces. Utilizing Dlib’s face detection tools, we performed a thorough analysis of each metric’s effectiveness. The evaluation involved multiple iterations to ensure robust results. Our results reveal that the Manhattan distance metric generally offers superior computational efficiency, with the lowest average computation time of 0.588 milliseconds, compared to Euclidean and Minkowski metrics. While the Euclidean metric provides high accuracy, particularly in controlled Environments like the Yale Faces dataset the Manhattan metric offers a more balanced tradeoff between accuracy and computational time. The Minkowski distance metric, while versatile, generally falls between the Euclidean and Manhattan metrics in terms of efficiency and accuracy. In scenarios with occlusions, such as those found in the Family Faces dataset, the Manhattan distance metric maintains a competitive edge in both accuracy and efficiency compared to other metrics. For applications that demand both high accuracy and minimal computational overhead, especially in real-world environments with potential occlusions, the Manhattan distance metric is particularly recommended. Conversely, when computational efficiency is less of a concern, the Euclidean metric remains a reliable choice. These insights provide valuable guidance for optimizing facial recognition systems to meet diverse application requirements and computational constraints.

Context. The third Gaia Data Release (DR3) provided photometric time series of more than 2 million long-period variable (LPV) candidates. Anticipating the publication of full radial-velocity data planned with Data Release 4, this Focused Product Release (FPR) provides radial-velocity time series for a selection of LPV candidates with high-quality observations. Aims. We describe the production and content of the Gaia catalog of LPV radial-velocity time series, and the methods used to compute the variability parameters published as part of the Gaia FPR. Methods. Starting from the DR3 catalog of LPV candidates, we applied several filters to construct a sample of sources with high-quality radial-velocity measurements. We modeled their radial-velocity and photometric time series to derive their periods and amplitudes, and further refined the sample by requiring compatibility between the radial-velocity period and at least one of the G, GBP, or GRP photometric periods. Results. The catalog includes radial-velocity time series and variability parameters for 9614 sources in the magnitude range 6 ≲ G/mag ≲ 14, including a flagged top-quality subsample of 6093 stars whose radial-velocity periods are fully compatible with the values derived from the G, GBP, and GRP photometric time series. The radial-velocity time series contain a mean of 24 measurements per source taken unevenly over a duration of about three years. We identify the great majority of the sources (88%) as genuine LPV candidates, with about half of them showing a pulsation period and the other half displaying a long secondary period. The remaining 12% of the catalog consists of candidate ellipsoidal binaries. Quality checks against radial velocities available in the literature show excellent agreement. We provide some illustrative examples and cautionary remarks. Conclusions. The publication of radial-velocity time series for almost ten thousand LPV candidates constitutes, by far, the largest such database available to date in the literature. The availability of simultaneous photometric measurements gives a unique added value to the Gaia catalog.

In this paper, we present design and implementation features and validation of KOMPSAT-2 simulator (SIM). The SIM is implemented on PC server to minimize costs and troubles on embedding onboard flight software into simulator. Object oriented design methodology is employed to maximized S/W reusability, and XML is used for S/C characteristics data, TC, TM and Simulation data instead of expensive commercial DB. Consequently, we can reduce costs for the system development, efforts on embedding flight software. A simulation for science fine mode operation is presented to demonstrate the overall validation of SIM. SIM has been verified officially by various tests such as SIM subsystem test, MCE system integration test, interface test, site installation test, and acceptance test. They were performed successfully.KeywordsClass DiagramAcceptance TestLogical ViewFlight SoftwareMission AnalysisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

While it is generally recognised that subgroup analyses can produce spurious results, the extent of the problem is almost certainly under-estimated. This is particularly true when subgroup-specific analyses are used. In addition, the increase in sample size required to identify differential subgroup effects may be substantial and the commonly used 'rule of four' may not always be sufficient, especially when interactions are relatively subtle, as is often the case. CONCLUSIONS--RECOMMENDATIONS FOR SUBGROUP ANALYSES AND THEIR INTERPRETATION: (1) Subgroup analyses should, as far as possible, be restricted to those proposed before data collection. Any subgroups chosen after this time should be clearly identified. (2) Trials should ideally be powered with subgroup analyses in mind. However, for modest interactions, this may not be feasible. (3) Subgroup-specific analyses are particularly unreliable and are affected by many factors. Subgroup analyses should always be based on formal tests of interaction although even these should be interpreted with caution. (4) The results from any subgroup analyses should not be over-interpreted. Unless there is strong supporting evidence, they are best viewed as a hypothesis-generation exercise. In particular, one should be wary of evidence suggesting that treatment is effective in one subgroup only. (5) Any apparent lack of differential effect should be regarded with caution unless the study was specifically powered with interactions in mind. CONCLUSIONS--RECOMMENDATIONS FOR RESEARCH: (1) The implications of considering confidence intervals rather than p-values could be considered. (2) The same approach as in this study could be applied to contexts other than RCTs, such as observational studies and meta-analyses. (3) The scenarios used in this study could be examined more comprehensively using other statistical methods, incorporating clustering effects, considering other types of outcome variable and using other approaches, such as Bootstrapping or Bayesian methods.

One of the many applications of X-ray computed tomography (CT) in industry is the detection of pores, cavities and other flaws in cast metal parts. Because of its improvement on part safety and saving of expenses, CT inspection is moving from a random sample inspection towards a full in-line inspection. With the increasing amount of produced data, however, comes the need for an automated processing. Due to tight time constraints the resulting CT scans are very artifact afflicted, which impedes automated inspection. In recent years, deep learning methods—convolutional neural networks in particular—have been used with great success to tackle even complex segmentation tasks in cluttered scenes. As we show, these methods are also applicable to the domain of industrial CT data: they are able to cope with noise, beam hardening, scatter and other artifacts which we encounter here. However, these methods need a vast amount of precisely labeled training data to work properly. Gathering the necessary data is not only cumbersome due to the need of annotating three-dimensional data but also expensive as it requires the knowledge of domain experts. Therefore, we present a new approach: We train our models on realistically simulated CT data only. Here, a precise per-voxel ground truth can simply be computed. In order to show that the simulated data is sufficient to train a segmentation network, we turn to its prediction performance on real CT data. We compare the prediction performance of traditional algorithms as well as the trained segmentation network on simulated and real validation data and demonstrate that they behave similarly. The ground truth for the real validation data is hand-labeled using high-quality CT scans, while the actual validation set consists of CT scans of lower quality of the exact same parts. For a comprehensive evaluation, we evaluate the probability of detection as well as the intersection over union. The first tells us how likely a flaw of given size can be found with a given confidence, which is of special interest to domain experts. The latter gives us a per-voxel information of how precise the overall segmentation is. Moreover, our synthetic data enables us to examine the influence of different artifact types on the detection rate. Besides these quantitative analyses we show some qualitative results of real-world applications. To the best of our knowledge, we describe the first approach for defect detection in three-dimensional CT data, which is solely trained with simulated data.

view Abstract Citations (288) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Spectroscopic Survey of Compact and Peculiar Galaxies Sargent, Wallace L. W. Abstract Low-dispersion spectrograms have been obtained for 141 objects in Zwicky's first five lists of compact galaxies. These 141 objects were largely but not completely selected for their blue appearance on the Sky Survey prints. Direct photographs were obtained at the 200-inch prime focus of a representative sample of thirty objects. Photoelectric observations were made for forty4our galaxies. The spectra show ten objects to have Seyfert-like emission lines; thirty-three to have sharp emission lines; twenty to have both absorption lines and sharp emission lines; sixty to have absorption lines; and three to have continuous spectra. The remaining objects were galactic stars and one planetary nebula. The UBV colors of the galaxies are correlated with the spectra. Individual descriptions of the 126 galaxies, including their redshifts and absolute magnitudes, are given. The mean redshift is 9994 km , and the mean absolute magnitude is Mp = -20.2. The galaxies are a very heterogeneous collection with a range in absolute magnitude -14.9> Mp> -23.2. The galaxies with sharp emission lines are probably excited by hot stars. Many new interesting objects are described, including field galaxies with high intrinsic luminosities, four new Seyfert galaxies, a new "ring" galaxy, and several dwarf galaxies with very strong, sharp emission lines. We show that the galaxies for which 200-inch photographs were obtained are indeed compact in the sense of having an abnormally high luminosity per square parsec. Publication: The Astrophysical Journal Pub Date: May 1970 DOI: 10.1086/150443 Bibcode: 1970ApJ...160..405S full text sources ADS | data products NED (140) SIMBAD (2)