scholarly journals Validation of PSF models for HST and other space-based observations

2020 ◽  
Vol 496 (4) ◽  
pp. 5017-5038
Author(s):  
Bryan R Gillis ◽  
Tim Schrabback ◽  
Ole Marggraf ◽  
Rachel Mandelbaum ◽  
Richard Massey ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
Practical Significance ◽  
Wide Field ◽  
Polynomial Coefficients ◽  
Standard Tool ◽  
The Difference ◽  
Telescope Optics ◽  
Advanced Camera For Surveys

ABSTRACT Forthcoming space-based observations will require high-quality point spread function (PSF) models for weak gravitational lensing measurements. One approach to generating these models is using a wavefront model based on the known telescope optics. We present an empirical framework for validating such models to confirm that they match the actual PSF to within requirements by comparing the models to the observed light distributions of isolated stars. We apply this framework to Tiny Tim, the standard tool for generating model PSFs for the Hubble Space Telescope (HST), testing its models against images taken by HST’s Advanced Camera for Surveys in the Wide Field Channel. We show that Tiny Tim’s models, in the default configuration, differ significantly from the observed PSFs, most notably in their sizes. We find that the quality of Tiny Tim PSFs can be improved through fitting the full set of Zernike polynomial coefficients that characterize the optics, to the point where the practical significance of the difference between model and observed PSFs is negligible for most use cases, resulting in additive and multiplicative biases both of order ∼4 × 10−4. We also show that most of this improvement can be retained through using an updated set of Zernike coefficients, which we provide.

scholarly journals Near-infrared surface brightness fluctuation measurements with the Hubble Space Telescope's WFC3/IR channel

2012 ◽  
Vol 8 (S289) ◽  
pp. 371-374
Author(s):  
Hyejeon Cho ◽  
Joseph B. Jensen ◽  
John P. Blakeslee ◽  
Brigham S. French ◽  
Hyun-chul Lee ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Wide Field ◽  
Population Synthesis ◽  
Early Type ◽  
Distance Method ◽  
Brightness Fluctuation ◽  
Advanced Camera For Surveys ◽  
Fornax Cluster

AbstractThe surface brightness fluctuation (SBF) method at near-infrared (NIR) wavelengths is a powerful tool for estimating distances to unresolved stellar systems with high precision. The IR channel of the Wide Field Camera 3 (WFC3), installed on board the Hubble Space Telescope (HST) in 2009, has a greater sensitivity and a wider field of view than the previous generation of HST IR instruments, making it much more efficient for measuring distances to early-type galaxies in the Local Volume. To take full advantage of its capabilities, we need to empirically calibrate the SBF distance method for WFC3's NIR passbands. We present the SBF measurements for the WFC3/IR F160W bandpass filter using observations of 16 early-type galaxies in the Fornax and Virgo Clusters. These have been combined with existing (g475–z850) color measurements from the Advanced Camera for Surveys Virgo and Fornax Cluster Surveys to derive a space-based H160-band SBF relation as a function of color. We have also compared the absolute SBF magnitudes to those predicted by evolutionary population synthesis models in order to study stellar population properties in the target galaxies.

scholarly journals Shapes and alignments of dark matter haloes and their brightest cluster galaxies in 39 strong lensing clusters

2020 ◽  
Vol 496 (3) ◽  
pp. 2591-2604 ◽  
Author(s):  
Taizo Okabe ◽  
Masamune Oguri ◽  
Sébastien Peirani ◽  
Yasushi Suto ◽  
Yohan Dubois ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
Mean Value ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Strong Lensing ◽  
The Mean ◽  
The Difference ◽  
Massive Clusters

ABSTRACT We study shapes and alignments of 45 dark matter (DM) haloes and their brightest cluster galaxies (BCGs) using a sample of 39 massive clusters from Hubble Frontier Field (HFF), Cluster Lensing And Supernova survey with Hubble (CLASH), and Reionization Lensing Cluster Survey (RELICS). We measure shapes of the DM haloes by strong gravitational lensing, whereas BCG shapes are derived from their light profiles in Hubble Space Telescope images. Our measurements from a large sample of massive clusters presented here provide new constraints on DM and cluster astrophysics. We find that DM haloes are on average highly elongated with the mean ellipticity of 0.482 ± 0.028, and position angles of major axes of DM haloes and their BCGs tend to be aligned well with the mean value of alignment angles of 22.2 ± 3.9 deg. We find that DM haloes in our sample are on average more elongated than their BCGs with the mean difference of their ellipticities of 0.11 ± 0.03. In contrast, the Horizon-AGN cosmological hydrodynamical simulation predicts on average similar ellipticities between DM haloes and their central galaxies. While such a difference between the observations and the simulation may well be explained by the difference of their halo mass scales, other possibilities include the bias inherent to strong lensing measurements, limited knowledge of baryon physics, or a limitation of cold DM.

scholarly journals Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud – IV. Evidence for multiple populations in Hodge 11 and NGC 2210

2019 ◽  
Vol 486 (4) ◽  
pp. 5581-5599 ◽  
Author(s):  
Christina K Gilligan ◽  
Brian Chaboyer ◽  
Jeffrey D Cummings ◽  
Dougal Mackey ◽  
Roger E Cohen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Cluster Formation ◽  
Stellar Populations ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Wide Field ◽  
Horizontal Branch ◽  
Advanced Camera For Surveys

Abstract We present a multiple population search in two old Large Magellanic Cloud (LMC) Globular clusters, Hodge 11 and NGC 2210. This work uses data from the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope from programme GO-14164 in Cycle 23. Both of these clusters exhibit a broadened main sequence with the second population representing (20 ± ∼5) per cent for NGC 2210 and (30 ± ∼5) per cent for Hodge 11. In both clusters, the smaller population is redder than the primary population, suggesting CNO variations. Hodge 11 also displays a bluer second population in the horizontal branch, which is evidence for helium enhancement. However, even though NGC 2210 shows similarities to Hodge 11 in the main sequence, there does not appear to be a second population on NGC 2210’s horizontal branch. This is the first photometric evidence that ancient LMC Globular clusters exhibit multiple stellar populations.

scholarly journals Hubble Space Telescope photometry of multiple stellar populations in the inner parts of NGC 2419

2019 ◽  
Vol 624 ◽  
pp. A25 ◽  
Author(s):  
Søren S. Larsen ◽  
Holger Baumgardt ◽  
Nate Bastian ◽  
Svea Hernandez ◽  
Jean Brodie
Keyword(s):  
Hubble Space Telescope ◽  
Dynamical Evolution ◽  
Bimodal Distribution ◽  
Wide Field ◽  
Red Giants ◽  
Space Telescope ◽  
Deep Imaging ◽  
Central Regions ◽  
Average Rotation ◽  
The Difference

We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W–F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of ΔY ≃ 0.05, but the P2 stars exhibit a significant spread in He content and some may reach ΔY ≃ 0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances ([Mg/Fe] <  0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p ≃ 0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.

Public interaction with judicial and law enforcement agencies: aspect of legal education

2020 ◽  
pp. 125-132
Author(s):  
Oleksandr Ostrohliad
Keyword(s):  
Legal Education ◽  
Point Of View ◽  
Practical Significance ◽  
Educational Services ◽  
Market Regulation ◽  
Law Enforcement Agencies ◽  
Legal Professions ◽  
The Difference ◽  
The Impact

Purpose. The aim of the work is to consider promising directions for reforming legal education in Ukraine, providing for the development of the corresponding conceptual framework. An indication of the gaps in the current legislation on the staffing of the main areas of legal activity. Focusing on the difference between the concepts of “right to education” and “access to a profession”, as well as the need for market regulation of the provision of educational services with the help of independent institutions. The methodology. The methodology includes a comprehensive analysis and generalization of the available scientific and theoretical material and the formulation of appropriate conclusions and recommendations. During the research, the following methods of scientific knowledge were used: terminological, logical-semantic, system-structural, logical-normative, comparative-historical. Results In the course of the study, it was determined that despite the fact that a draft Concept for the Development of Legal Education has been developed, its perfection from the point of view of the prospects for influencing the improvement of the quality of lawyers' training raises many objections. On the basis of a comparative study, it was determined that promising areas for improving the training of lawyers in Ukraine are: the activities of independent agencies to confirm the quality of the services provided, as well as the improvement of regulatory regulation, which implies access to the profession. Originality. In the course of the study, it was established that the improvement of the quality of training of lawyers in Ukraine should occur through natural development: a specially authorized body should establish only compliance with accreditation requirements; the institution of higher education must, taking into account the principle of autonomy, ensure an appropriate level of quality in the provision of educational services; access to certain legal professions requires significant procedural improvements. The draft Concept for the development of legal education at the moment needs substantial revision, as well as to provide an understanding of the impact of previous reform steps in the field of education, cannot be adopted in the near future. Practical significance. The results of the study can be used in law-making activities to improve the norms of the current legislation providing for access to legal professions, as well as for further scientific research of the problems of legal education in Ukraine.

scholarly journals The Hubble Source Catalog

2016 ◽  
Vol 12 (S325) ◽  
pp. 114-117
Author(s):  
Stephen H. Lubow
Keyword(s):  
Hubble Space Telescope ◽  
Wide Field ◽  
Positional Accuracy ◽  
Space Telescope ◽  
Multiple Wavelengths ◽  
Advanced Camera For Surveys ◽  
Cross Matching

AbstractThe Hubble Source Catalog (HSC) is designed to enhance the science obtained from the Hubble Space Telescope by combining the tens of thousands of visit-based source lists in the Hubble Legacy Archive (HLA) across filters and detectors into a single master catalog. The catalog contains data from the major Hubble imaging instruments: Wide Field Planetary Camera 2 (WFPC2), Advanced Camera for Surveys (ACS), and Wide Field Camera 3 (WFC3). It is based on cross matching and astrometry algorithms developed by Budavari & Lubow (2012). We recently released Version 2 that is three times the size of Version 1 and includes some new features. The catalog can be accessed through a variety of interfaces (see http://archive.stsci.edu/hst/hsc/). The HSC provides descriptions of astronomical objects involving multiple wavelengths and epochs. High relative positional accuracy of objects is achieved across the Hubble images, often with sub-pixel precision of a few milliarcseconds.

scholarly journals The grey extinction curve in NGC 3603

2014 ◽  
Vol 10 (S312) ◽  
pp. 243-244
Author(s):  
Xiaoying Pang ◽  
Anna Pasquali ◽  
Eva K. Grebel
Keyword(s):  
Standard Deviation ◽  
High Resolution ◽  
Hubble Space Telescope ◽  
Starburst Galaxies ◽  
Extinction Curve ◽  
Wide Field ◽  
Space Telescope ◽  
Advanced Camera For Surveys

AbstractWe use photometry in the F220W, F250W, F330W, F435W filters from the High Resolution Channel of the Advanced Camera for Surveys and photometry in the F555W, F675W, and F814W filters from the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope to derive individual stellar reddenings and extinctions for member stars in the HD 97950 cluster in the giant H ii region NGC 3603. Within the standard deviation associated with E(λ−F555W)/E(F435W−F555W) in each filter, the cluster extinction curve at ultraviolet wavelengths tends to be greyer than the average Galactic extinction laws from Cardelli et al. (1989) and Fitzpatrick et al. (1999). It is closer to the extinction law derived by Calzetti et al. (2000) for starburst galaxies, where the 0.2175 μm bump is absent.

scholarly journals Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud – V. Multiple populations in ancient globular clusters

2020 ◽  
Vol 494 (2) ◽  
pp. 1946-1955
Author(s):  
Christina K Gilligan ◽  
Brian Chaboyer ◽  
Jeffrey D Cummings ◽  
Dougal Mackey ◽  
Roger E Cohen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Hubble Space Telescope ◽  
Cluster Formation ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Wide Field ◽  
Multiple Populations ◽  
Show Evidence ◽  
Advanced Camera For Surveys

ABSTRACT We examine four ancient Large Magellanic Cloud (LMC) globular clusters (GCs) for evidence of multiple stellar populations using the Advanced Camera for Surveys and Wide Field Camera 3 on the Hubble Space Telescope Programme GO-14164. NGC 1466, NGC 1841, and NGC 2257 all show evidence for a redder, secondary population along the main sequence. Reticulum does not show evidence for the presence of a redder population, but this GC has the least number of stars and Monte Carlo simulations indicate that the sample of main-sequence stars is too small to robustly infer whether a redder population exists in this cluster. The second, redder, population of the other three clusters constitutes $\sim 30-40{{\ \rm per\ cent}}$ of the total population along the main sequence. This brings the total number of ancient LMC GCs with known split or broadened main sequences to five. However, unlike for Hodge 11 and NGC 2210 (see Gilligan et al. (2019)), none of the clusters shows evidence for multiple populations in the horizontal branch. We also do not find evidence of a second population along the red giant branch.

A method for the use of ellipticities and spot diameters for the measurement of aberrations in wide-field telescopes

2014 ◽  
Vol 3 (3) ◽  
Author(s):  
Lothar Noethe ◽  
Pietro Schipani ◽  
Ronald Holzlöhner ◽  
Andrew Rakich
Keyword(s):  
Field Dependence ◽  
Gravitational Lensing ◽  
Closed Loop ◽  
Field Survey ◽  
Closed Loop Control ◽  
Zernike Polynomials ◽  
Wide Field ◽  
Loop Control ◽  
Wavefront Aberrations ◽  
Telescope Optics

AbstractIn wide-field survey telescopes, the patterns of spot sizes and ellipticities can be used to determine wavefront aberrations generated by the telescope. The calculation of spot sizes and ellipticities generated by telescope aberrations is most conveniently done if the aberrations are expressed in terms of Zernike-type polynomials whose derivatives are orthonormal. The field dependence of the spot sizes and ellipticities generated by the telescope can conveniently be expressed by low-order Zernike polynomials. Because the exposure times in astronomical survey work are typically rather short, this information may be used for a quasi-closed loop control of the telescope optics. The ability to accurately subtract ellipticities generated by telescope errors could also be useful for observations such as gravitational lensing surveys.

scholarly journals Cosmic distances from surface brightness fluctuations

2012 ◽  
Vol 8 (S289) ◽  
pp. 304-311 ◽  
Author(s):  
John P. Blakeslee
Keyword(s):  
Surface Brightness ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Stellar System ◽  
Distance Scale ◽  
Wide Field ◽  
Coma Cluster ◽  
Infrared Wavelength ◽  
Surface Brightness Fluctuations ◽  
Advanced Camera For Surveys

AbstractHigh spatial-resolution measurements of surface brightness fluctuations (SBFs) with the Hubble Space Telescope (HST) provide the most precise distances available to early-type galaxies beyond the Local Group. The observable SBF magnitude in a given bandpass is a basic property of any stellar system, corresponding to a ratio of the first and second moments of the stellar luminosity function. Calibration of the method has presented challenges, but we now have an excellent empirical determination of how the SBF observable varies with galaxy color in broad bandpasses at the red end of the optical spectrum, and we are working towards a similar calibration for HST's Wide-Field Camera 3 in the near-infrared wavelength range, where the SBF magnitudes are considerably brighter. From HST Advanced Camera for Surveys data, we have determined the relative distances of the Virgo and Fornax clusters to within a precision of 2%, and resolved their internal structures. More recent measurements allow us to tie the Coma cluster, the standard of comparison for distant cluster studies, to the same precise distance scale. The SBF method can be calibrated in an absolute sense either empirically using Cepheids or theoretically based on stellar population models. The agreement between model and empirical zero points provides an independent confirmation of the Cepheid distance scale.

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