scholarly journals Hubble Space Telescope Observations of AGN

1994 ◽  
Vol 159 ◽  
pp. 83-104 ◽  
Author(s):  
F. Macchetto
Keyword(s):  
Dynamic Range ◽  
Hubble Space Telescope ◽  
Active Galaxies ◽  
Broad Line ◽  
Galaxy Mergers ◽  
Space Telescope ◽  
Extended Dynamic

Only little more than three years have passed since the launch of the Hubble Space Telescope (HST) and the wealth of results produced by astronomers using it, have already made fundamental contributions to our understanding of a variety of astrophysical processes. A considerable number of investigations have been, and are being, devoted to the study of the whole gamut of problems associated with activity in galaxies. These range from the very largest scales, namely those applicable to the study of the optical jets and galaxy mergers (10–100 kpc) to the smallest scales (1–10 pc) relevant to investigate the broad-line regions and the very center of the active galaxies. In all cases, the high-spatial resolutions, extended dynamic range and ultraviolet response, has made possible the study of a number of objects with a detail impossible without the HST.

scholarly journals Synthetic Photometry and the Calibration of the Hubble Space Telescope

1986 ◽  
Vol 7 ◽  
pp. 833-843 ◽  
Author(s):  
J. Koornneef ◽  
R. Bohlin ◽  
R. Buser ◽  
K. Horne ◽  
D. Turnshek
Keyword(s):  
Full Advantage ◽  
Dynamic Range ◽  
Hubble Space Telescope ◽  
Scientific Instruments ◽  
Space Telescope ◽  
Sensitivity Functions

AbstractThe combined Scientific Instruments (SIs) on the Hubble Space Telescope (HST) feature an extensive wavelength coverage in both photometric and spectrophotometric modes with an overall dynamic range of more than twenty-five magnitudes. We demonstrate how synthetic photometry techniques are to be used to establish and maintain their calibration. This approach makes efficient use of limited HST observing time by taking full advantage of pre-launch knowledge on the SI sensitivity functions and calibration targets.

scholarly journals Hubble Space Telescope observations of BALQSO Ton 34 reveal a connection between the broad-line region and the BAL outflow

2017 ◽  
Vol 468 (3) ◽  
pp. 3607-3614 ◽  
Author(s):  
Y. Krongold ◽  
L. Binette ◽  
R. Bohlin ◽  
L. Bianchi ◽  
A. L. Longinotti ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Broad Line ◽  
Space Telescope ◽  
Broad Line Region ◽  
Line Region

scholarly journals Hubble Space Telescope: A Generator of Sub-Milliarcsecond Precision Parallaxes

1995 ◽  
Vol 166 ◽  
pp. 89-94
Author(s):  
G. Benedict ◽  
W. Jefferys ◽  
B. McArthur ◽  
E. Nelan ◽  
A. Whipple ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Hubble Space Telescope ◽  
Space Telescope ◽  
To Come

Hubble Space Telescope Fine Guidance Sensor 3 can generate sub-milliarcsecond precision parallaxes in eighteen months. We discuss the internal precision and external accuracy of our observations of Proxima Centauri and Barnard's Star. For some classes of targets Hubble Space Telescope will remain the parallax tool of choice for years to come. It can offer 0.5 mas precision. It will remain useful by satisfying urgent needs for quick results, by offering a 13 magnitude dynamic range, and by providing an unparalleled binary dissection capability.

scholarly journals Space Telescope and Optical Reverberation Mapping Project: A Leap Forward in Reverberation Mapping

2016 ◽  
Vol 12 (S324) ◽  
pp. 215-218 ◽  
Author(s):  
Bradley M. Peterson
Keyword(s):  
World Wide ◽  
Hubble Space Telescope ◽  
Line Emission ◽  
Broad Line ◽  
Space Telescope ◽  
Reverberation Mapping ◽  
Significant Challenge ◽  
Past Behavior ◽  
Line Region ◽  
Mapping Program

AbstractIn 2014, a 179-orbit allocation of Hubble Space Telescope time anchored a massive reverberation-mapping program on the well-studied Seyfert 1 galaxy NGC 5548. Supporting imaging and spectrophotometric observations were provided by Swift, Chandra, Spitzer, and a world-wide network of ground-based telescopes. Understanding the data remains a significant challenge, partly because the level of detail is far beyond what has been seen before and partly because the behavior of the AGN was not typical of its past behavior. Based on analysis to date, the following conclusions can be reached: (1) the AGN accretion disk has a temperature profile that is consistent with that predicted by the Shakura–Sunyaev model, but is about three times larger than expected; (2) at least part of the broad-line region appears to be a Keplerian disk seen at intermediate inclination, and (3) the broad-line emission response from the far side of the disk is weaker than expected.

Time-series photometry of a new set of candidate faint spectrophotometric standard DA white dwarfs

2018 ◽  
Vol 14 (A30) ◽  
pp. 493-493
Author(s):  
Annalisa Calamida
Keyword(s):  
Time Series ◽  
Conference Proceedings ◽  
First Principles ◽  
White Dwarfs ◽  
Dynamic Range ◽  
Hubble Space Telescope ◽  
Pure Hydrogen ◽  
Space Telescope ◽  
Large Aperture ◽  
Northern Latitudes

Future facilities and deep surveys such as LSST, JWST and WFIRST, will require a network of standards faint enough to avoid saturation and homogenously distributed in both hemispheres. DA white dwarfs have almost pure hydrogen atmospheres and they are the simplest stars to model. The opacities are known from first principles, and for temperatures higher than ∼ 20,000 K, their photospheres are purely radiative and should be photometrically stable. DA white dwarfs are then the best candidates to establish a network of faint spectrophotometric standards. In order to provide standards in the dynamic range of large aperture (d > 4m) telescopes, we collected Hubble Space Telescope WFC3 images and ground-based spectroscopy for 23 DA white dwarfs fainter than r ∼ 16.5 mag, distributed at equatorial and northern latitudes (see Saha et al. in these conference proceedings).

scholarly journals Automated distant galaxy merger classifications from Space Telescope images using the Illustris simulation

2019 ◽  
Vol 486 (3) ◽  
pp. 3702-3720 ◽  
Author(s):  
Gregory F Snyder ◽  
Vicente Rodriguez-Gomez ◽  
Jennifer M Lotz ◽  
Paul Torrey ◽  
Amanda C N Quirk ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Hubble Space Telescope ◽  
Machine Learning Techniques ◽  
Galaxy Mergers ◽  
Distant Galaxy ◽  
Space Telescope ◽  
James Webb Space Telescope ◽  
Learning Techniques ◽  
Merger Rate ◽  
Do So

ABSTRACT We present image-based evolution of galaxy mergers from the Illustris cosmological simulation at 12 time-steps over 0.5 < z < 5. To do so, we created approximately one million synthetic deep Hubble Space Telescope and James Webb Space Telescope images and measured common morphological indicators. Using the merger tree, we assess methods to observationally select mergers with stellar mass ratios as low as 10:1 completing within ±250 Myr of the mock observation. We confirm that common one- or two-dimensional statistics select mergers so defined with low purity and completeness, leading to high statistical errors. As an alternative, we train redshift-dependent random forests (RFs) based on 5–10 inputs. Cross-validation shows the RFs yield superior, yet still imperfect, measurements of the late-stage merger fraction, and they select more mergers in bulge-dominated galaxies. When applied to CANDELS morphology catalogues, the RFs estimate a merger rate increasing to at least z = 3, albeit two times higher than expected by theory. This suggests possible mismatches in the feedback-determined morphologies, but affirms the basic understanding of galaxy merger evolution. The RFs achieve completeness of roughly $70{{\ \rm per\ cent}}$ at 0.5 < z < 3, and purity increasing from $10{{\ \rm per\ cent}}$ at z = 0.5–60 per cent at z = 3. At earlier times, the training sets are insufficient, motivating larger simulations and smaller time sampling. By blending large surveys and large simulations, such machine learning techniques offer a promising opportunity to teach us the strengths and weaknesses of inferences about galaxy evolution.

scholarly journals A Hubble Space Telescope Imaging Survey of Low-redshift Swift-BAT Active Galaxies*

2021 ◽  
Vol 256 (2) ◽  
pp. 40
Author(s):  
Minjin Kim ◽  
Aaron J. Barth ◽  
Luis C. Ho ◽  
Suyeon Son
Keyword(s):  
Hubble Space Telescope ◽  
Active Galaxies ◽  
Space Telescope

scholarly journals Galaxies with Binary Nuclei

2013 ◽  
Vol 9 (S304) ◽  
pp. 363-370
Author(s):  
Yervant Terzian ◽  
Edward Khachikian
Keyword(s):  
Hubble Space Telescope ◽  
Radio Galaxies ◽  
Active Galaxies ◽  
Emission Lines ◽  
Special Astrophysical Observatory ◽  
Host Galaxies ◽  
Strong Emission ◽  
Space Telescope ◽  
Byurakan Astrophysical Observatory ◽  
The Common

AbstractIt is known that among active galaxies (AG) with strong emission lines (UV-galaxies, Sy1 and Sy2, Markarian and Kazarian galaxies, radio-galaxies, QSOs host galaxies and so on) there is a large percentage of objects with double and multiple (or complex) nuclei. The common sizes of these nuclei are of the order of a few hundred parsecs or kiloparsecs. We shall discuss the results of morphological and spectroscopic observations of a number of “active galaxies” carried out with the 5m Palomar telescope, 2.6m telescope of Ambartsumian Byurakan Astrophysical Observatory, 6m telescope of Special Astrophysical Observatory in Russia, and newer Hubble Space Telescope data.

scholarly journals The dynamics of the broad-line region in NGC 3227

2020 ◽  
Vol 500 (1) ◽  
pp. 786-794
Author(s):  
Nick Devereux
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
Outer Radius ◽  
Short Time Scale ◽  
Broad Line ◽  
Fall Velocity ◽  
Space Telescope ◽  
X Ray ◽  
Broad Line Region ◽  
Line Region

ABSTRACT Archival Hubble Space Telescope (HST) observations of the Seyfert 1 nucleus of NGC 3227 obtained with the Space Telescope Imaging Spectrograph (STIS) are re-examined in order to constrain a viable photoionization model for the broad-line region (BLR). The results imply that the BLR is a partially ionized, dust-free, spherical shell that is collapsing, supersonically, at the free-fall velocity due to its proximity to a supermassive black hole. The BLR is ionization bounded at the outer radius, coincident with the dust reverberation radius, and transforms into an X-ray emitting plasma inside the Balmer reverberation radius as the central UV–X-ray source is approached. Only 40 M⊙ of Hydrogen are required to explain the Balmer emission-line luminosity, but it is compressed by gravity into a column measuring 5.5 × 1024 atoms cm−2. Assuming radiatively inefficient accretion, the X-ray luminosity requires ∼10−2 M⊙ yr−1. However, the mass inflow rate required to explain the luminosity of the broad H α emission line is ∼1 M⊙ yr−1. The very large disparity between these two estimates indicates that 99 per cent of the inflowing gas must be re-directed into an outflow, and on a very short time-scale corresponding to ∼40 yr. Alternatively, the radiative efficiency of the inflow has been overestimated, or the X-ray luminosity has been underestimated, a distinct possibility if the BLR is indeed Compton-thick.

scholarly journals Excitation Mechanism of Extended Emission-Line Regions in Active Galaxies

1997 ◽  
Vol 159 ◽  
pp. 386-389
Author(s):  
Ian Evans ◽  
Anuradha Koratkar ◽  
Mark Allen ◽  
Zlatan Tsvetanov ◽  
Michael Dopita
Keyword(s):  
Emission Line ◽  
Hubble Space Telescope ◽  
Optical Emission ◽  
Active Galaxies ◽  
Emission Lines ◽  
Uv Spectrophotometry ◽  
Excitation Mechanism ◽  
Space Telescope ◽  
Shock Models ◽  
Extended Emission

AbstractPhotoionization and shock models of the extended emissionline regions (EELRs) in active galaxies demonstrate that the optical emission lines alone are a poor discriminant of the excitation mechanism. Combining optical and UV data provides a discriminant between nuclear photoionization and autoionizing shock models. Hubble Space Telescope UV spectrophotometry of two Seyferts suggests that the EELRs in these objects are probably photoionized by the nucleus.

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