scholarly journals Hubble Space Telescope Observations of Extragalactic Jets

1996 ◽  
Vol 175 ◽  
pp. 195-200 ◽  
Author(s):  
F. Duccio Macchetto
Keyword(s):  
Hubble Space Telescope ◽  
Space Telescope ◽  
Central Source ◽  
Radio Jets ◽  
Extended Radio ◽  
Extragalactic Jets ◽  
The Subject ◽  
Radio Band ◽  
Better Than

The study of the optical counterparts to the radio jets has been the subject of a number of observing programs with the Hubble Space Telescope (HST). We know that these jets play a fundamental role in transporting energy from the central source to the extended radio lobes. Observations at optical and ultraviolet wavelengths with the HST are essential to obtain spatial resolutions similar to, or better than, those achieved in the radio band and, thus, provide the possibility of directly comparing the sites and mechanisms responsible for the emission at these different wavelengths.

scholarly journals Interpretation of Extragalactic Jets

1986 ◽  
Vol 89 ◽  
pp. 425-437
Author(s):  
Michael L. Norman
Keyword(s):  
High Resolution ◽  
Visual Inspection ◽  
Physical Parameters ◽  
Model Calculations ◽  
Radio Jets ◽  
Extragalactic Jets ◽  
Self Consistent ◽  
Interferometric Observation ◽  
The Subject

The subject of this paper is the interpretation of extragalactic radio jets. In this paper I will focus on what we have learned about the nature of extragalactic jets on the basis of model calculations. By model I mean any set of calculations, whether analytic, semi-analytic or numerical, which, when carried through from their respective assumptions to their internally self-consistent conclusions, help place constraints on the physical parameters and processes in the jets and their associated radio lobes. In this field, a visual inspection of a modern high-resolution radio interferometric observation (see review by PERLEY in these proceedings) often leads to statements like “that looks just like such and such in Landau and Lifschitz; I betcha that’s what’s going on!” This I call a speculation, or, at best, a hypothesis. I am addressing here the step beyond hypothesis, namely modeling, which is necessary to confront not only the object in question, but more importantly, the hypothesis itself. In the end, we will remember only the hypotheses.

scholarly journals The contribution of quasar absorption outflows to AGN feedback

2020 ◽  
Vol 499 (1) ◽  
pp. 1522-1529
Author(s):  
Timothy R Miller ◽  
Nahum Arav ◽  
Xinfeng Xu ◽  
Gerard A Kriss
Keyword(s):  
Absorption Line ◽  
Active Galactic Nucleus ◽  
Hubble Space Telescope ◽  
Broad Absorption ◽  
Feedback Effects ◽  
Space Telescope ◽  
Central Source ◽  
Broad Absorption Line

ABSTRACT Determining the distance of quasar absorption outflows from the central source (R) and their kinetic luminosity ($\dot{E}_\mathrm{\scriptstyle k}$) is crucial for understanding their contribution to active galactic nucleus (AGN) feedback. Here, we summarize the results for a sample of nine luminous quasars that were observed with the Hubble Space Telescope. We find that the outflows in more than half of the objects are powerful enough to be the main agents for AGN feedback, and that most outflows are found at R > 100 pc. The sample is representative of the quasar absorption outflow population as a whole and is unbiased towards specific ranges of R and $\dot{E}_\mathrm{\scriptstyle k}$. Therefore, the analysis results can be extended to the majority of such objects, including broad absorption line quasars. We find that these results are consistent with those of another sample (seven quasars) that is also unbiased towards specific ranges of R and $\dot{E}_\mathrm{\scriptstyle k}$. Assuming that all quasars have absorption outflows, we conclude that most luminous quasars produce outflows that can contribute significantly to AGN feedback. We also discuss the criterion for whether an outflow is energetic enough to cause AGN feedback effects.

scholarly journals The Use of the Hubble Space Telescope for Global Reference Frame Work

1986 ◽  
Vol 7 ◽  
pp. 87-88
Author(s):  
P. D. Hemenway
Keyword(s):  
Transfer Functions ◽  
Hubble Space Telescope ◽  
Field Of View ◽  
Optimum Conditions ◽  
Small Aperture ◽  
Space Telescope ◽  
Frame Work ◽  
Global Reference Frame ◽  
Better Than ◽  
Small Field Of View

The Hubble Space Telescope (HST) will have the capability of making relative astrometric measurements with an accuracy of four to ten times better than similar ground based measurements. The instruments of choice will be the Fine Guidance Sensors (FGS’s). Details of the instrumentation have been given elsewhere (c.f. Jefferys, 1980). Each FGS consists of two interferometer detectors which look at a small aperture located within a larger field of view (FOV). The raw data consist of encoder readings, from “star selectors”, and error signals derived from the interferometer transfer functions. The star selector positions determine the position of the small aperture within the pickles. The precision is always less than 0.001 arcsec, with an expected accuracy of 0.002 to 0.003 arcsec per observation. Under optimum conditions, the best expected accuracy is 0.0016 arcsec per observation. An observation will consist of the relative positions of several objects in one pickle. Thus the highest accuracy observations will be relative observations within a relatively small field of view.

scholarly journals A Survey of Extended Radio Jets in Active Galactic Nuclei withChandraand theHubble Space Telescope: First Results

2002 ◽  
Vol 571 (1) ◽  
pp. 206-217 ◽  
Author(s):  
Rita M. Sambruna ◽  
L. Maraschi ◽  
F. Tavecchio ◽  
C. Megan Urry ◽  
C. C. Cheung ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Space Telescope ◽  
Radio Jets ◽  
Extended Radio ◽  
First Results

A Survey of Extended Radio Jets withChandraand theHubble Space Telescope

2004 ◽  
Vol 608 (2) ◽  
pp. 698-720 ◽  
Author(s):  
Rita M. Sambruna ◽  
Jessica K. Gambill ◽  
L. Maraschi ◽  
F. Tavecchio ◽  
R. Cerutti ◽  
...  
Keyword(s):  
Space Telescope ◽  
Radio Jets ◽  
Extended Radio

scholarly journals HST Observations of Jets and Radio Lobes

1996 ◽  
Vol 175 ◽  
pp. 201-202
Author(s):  
Philippe Crane
Keyword(s):  
Hubble Space Telescope ◽  
Major Contributor ◽  
Space Telescope ◽  
Radio Jets

The Hubble Space Telescope has proved to be remarkably useful for discovering and for studying the optical counterparts of radio lobes and radio jets. Since much of the structure seen in the radio is found on subarcsecond scales, it is not surprising that HST, with it's improved resolution relative to ground based observations, would be a major contributor to this field of research. This paper reports briefly on some of these successes, and refers to more detailed descriptions in the literature.

scholarly journals The Gaia spectrophotometric standard stars survey – V. Preliminary flux tables for the calibration of Gaia DR2 and (E)DR3

2021 ◽  
Vol 503 (3) ◽  
pp. 3660-3676
Author(s):  
E Pancino ◽  
N Sanna ◽  
G Altavilla ◽  
S Marinoni ◽  
M Rainer ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Brown Dwarfs ◽  
Space Telescope ◽  
B Stars ◽  
Reference Scale ◽  
Systematic Effects ◽  
M Stars ◽  
Gaia Dr2 ◽  
Stars Survey ◽  
Better Than

ABSTRACT We present the flux tables of the spectrophotometric standard stars (SPSS) used to calibrate in flux the Gaia DR2 and (E)DR3 data releases. The latest SPSS grid version contains 112 stars, whose flux tables agree to better than 1 per cent with the CALSPEC spectra of 11 flux standards for the calibration of the Hubble Space Telescope. The synthetic magnitudes computed on the SPSS spectra also agree to better than 1 per cent with the Landolt magnitudes of 37 stars in common. The typical spreads in both comparisons are of the order of 1 per cent. These uncertainties already meet the initial requirements for the Gaia SPSS project, but further improvements are expected in the next SPSS versions, that will be used to calibrate future Gaia releases. We complement the SPSS flux tables with literature spectra of 60 additional stars that did not pass all the criteria to be SPSS, the Passband Validation Library (PVL). The PVL contains stars of extreme spectral types, such as bright O and B stars and late M stars and brown dwarfs, and was useful to investigate systematic effects in the previous Gaia DR2 release and to minimize them in the EDR3 one. The PVL literature spectra are recalibrated as accurately as possible on to the SPSS reference scale, so that the two sets together can be used in a variety of validation and comparison studies.

Handwriting Analysis and Personality Assessment

2000 ◽  
Vol 5 (1) ◽  
pp. 44-51 ◽  
Author(s):  
Peter Greasley
Keyword(s):  
Personality Traits ◽  
Personality Assessment ◽  
Personnel Selection ◽  
Empirical Studies ◽  
Handwriting Analysis ◽  
Recruitment Process ◽  
Academic Literature ◽  
Personnel Recruitment ◽  
The Subject ◽  
Better Than

It has been estimated that graphology is used by over 80% of European companies as part of their personnel recruitment process. And yet, after over three decades of research into the validity of graphology as a means of assessing personality, we are left with a legacy of equivocal results. For every experiment that has provided evidence to show that graphologists are able to identify personality traits from features of handwriting, there are just as many to show that, under rigorously controlled conditions, graphologists perform no better than chance expectations. In light of this confusion, this paper takes a different approach to the subject by focusing on the rationale and modus operandi of graphology. When we take a closer look at the academic literature, we note that there is no discussion of the actual rules by which graphologists make their assessments of personality from handwriting samples. Examination of these rules reveals a practice founded upon analogy, symbolism, and metaphor in the absence of empirical studies that have established the associations between particular features of handwriting and personality traits proposed by graphologists. These rules guide both popular graphology and that practiced by professional graphologists in personnel selection.

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