The European Space Agency's LISA mission study: status and present results

Johann, Ulrich; Ayre, Mark; Gath, Peter; Holota, Wolfgang; Marenaci, Pierangelo; Schulte, Hans Reiner; Weimer, Peter; Weise, Dennis

doi:10.1088/1742-6596/122/1/012005

Cited by 8 publications

(5 citation statements)

References 2 publications

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“…Looking further to the future, the LISA survey (Johann et al 2008) along with new high‐resolution X‐ray spectroscopy, will provide unequivocal information on the typical spins of the BH population and the orientations of jets. This will be complemented with detailed kinematic studies of the gas in large samples of galaxies (revealing the gas inflows) that the Square Kilometer Array (SKA; Schilizzi, Dewdney & Lazio 2008) will achieve, helping to solve these still open questions.…”

Section: Discussionmentioning

confidence: 99%

Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7

Lagos

Padilla

Strauss

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We determine the intrinsic shapes and orientations of 27 450 types I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 7 by studying the distribution of projected axial ratios of AGN hosts. Our aim is to study possible alignments between the AGN and host galaxy systems (e.g. the accretion disc and the galaxy angular momentum) and the effect of dust obscuration geometry on the AGN type. We define control samples of non‐AGN galaxies that mimic the morphology, colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. Assuming that AGN galaxies have the same underlying 3D shape distribution as their corresponding control samples, we find that the spiral and elliptical type I AGN populations are strongly skewed towards face‐on galaxies, while elliptical and spiral type II AGN populations are skewed towards edge‐on orientations. These findings rule out random orientations for AGN hosts at high confidence for type I spirals (δχ2≈ 230) and type II ellipticals (δχ2≈ 15), while the signal for type I ellipticals and type II spirals is weaker (δχ2≈ 3 and ≈6, respectively). We obtain a much stronger tendency for the type II spirals to be edge‐on when just high [O iii] equivalent width (EW) AGN are considered, suggesting that >20 per cent of low [O iii] EW edge‐on type II AGN may be missing from the optical sample. Galactic dust absorption of the broad‐line region alone cannot explain the observed inclination angle and projected axial ratio distributions of types I and II Seyfert galaxies, implying that obscuration by a small‐scale circumnuclear torus is necessary. These results favour a scenario in which the angular momentum of the material which feeds the black hole retains a memory of its original gas source at least to some small, non‐negligible degree.

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Section: Discussionmentioning

confidence: 99%

Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7

Lagos

Padilla

Strauss

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…Perdigues, private communication). Lessons could also be learned from the technological preparation of the LISA mission (Johann et al 2008; and references therein). The European Space Agency is currently undertaking a study into the precise relative positioning of MEO satellites.…”

Section: Martinmentioning

confidence: 99%

Simulations of imaging the event horizon of Sagittarius A* from space

Roelofs

Falcke

Brinkerink

et al. 2019

A&A

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Context. It has been proposed that Very Long Baseline Interferometry (VLBI) at sub-millimeter waves will allow us to image the shadow of the black hole in the center of our Milky Way, Sagittarius A* (Sgr A*), and thereby test basic predictions of the theory of general relativity. Aims. This paper presents imaging simulations of a new Space VLBI (SVLBI) mission concept. An initial design study of the concept has been presented in the form of the Event Horizon Imager (EHI). The EHI may be suitable for imaging Sgr A* at high frequencies (up to ∼ 690 GHz), which has significant advantages over performing ground-based VLBI at 230 GHz. The concept EHI design consists of two or three satellites in polar or equatorial circular Medium-Earth Orbits (MEOs) with slightly different radii. Due to the relative drift of the satellites along the individual orbits over the course of several weeks, this setup will result in a dense spiral-shaped uv-coverage with long baselines (up to ∼ 60 Gλ), allowing for extremely high-resolution and high-fidelity imaging of radio sources. Methods. We simulate observations of general relativistic magnetohydrodynamics (GRMHD) models of Sgr A* for the proposed configuration and calculate the expected noise based on preliminary system parameters. On long baselines, where the signal-to-noise ratio may be low, fringes could be detected if the system is sufficiently phase stable and the satellite orbits can be reconstructed with sufficient accuracy. Averaging visibilities accumulated over multiple epochs of observations could then help improving the image quality. With three satellites instead of two, closure phases could be used for imaging. Results. Our simulations show that the EHI could be capable of imaging the black hole shadow of Sgr A* with a resolution of 4 µas (about 8 % of the shadow diameter) within several months of observing time. Conclusions. Our preliminary study of the EHI concept shows that it is potentially of high scientific value, as it could be used to measure black hole shadows much more precisely than with ground-based VLBI, allowing for stronger tests of General Relativity and accretion models.

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“…Looking further to the future, the LISA survey (Johann et al 2008) along with new high-resolution X-ray spectroscopy, will provide unequivocal information on the typical spins of the BH population and the orientations of jets. This will be complemented with detailed kinematic studies of the gas in large samples of galaxies (revealing the gas inflows) that the Square Kilometer Array (SKA; Schilizzi et al 2008) will achieve, helping to solve these still open questions.…”

Section: Discussionmentioning

confidence: 99%

Host galaxy-active galactic nucleus alignments in the SDSS-DR7

Lagos,

Padilla,

Strauss

et al. 2010

Preprint

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We determine the intrinsic shapes and orientations of 27, 450 type I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 7, by studying the distribution of projected axis ratios of AGN hosts. Our aim is to study possible alignments between the AGN and host galaxy systems (e.g. the accretion disc and the galaxy angular momentum) and the effect of dust obscuration geometry on the AGN type. We define control samples of non-AGN galaxies that mimic the morphology, colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. Assuming that AGN galaxies have the same underlying three-dimensional shape distribution as their corresponding control samples, we find that the spiral and elliptical type I AGN populations are strongly skewed toward face-on galaxies, while ellipticals and spirals type II AGN are skewed toward edge-on orientations. These findings rule out random orientations for AGN hosts at high confidence for type I spirals (δχ 2 ≈ 230) and type II ellipticals (δχ 2 ≈ 15), while the signal for type I ellipticals and type II spirals is weaker (δχ 2 ≈ 3 and δχ 2 ≈ 6, respectively). We obtain a much stronger tendency for the type II spirals to be edge-on when just high [OIII] equivalent width (EW) AGN are considered, suggesting that > 20% of low [OIII] EW edge-on type II AGN may be missing from the optical sample. Galactic dust absorption of the broad-line region alone cannot explain the observed inclination angle and projected axis ratio distributions of type I and II Seyfert types, implying that obscuration by a small-scale circumnuclear torus is necessary. These results favour a scenario in which the angular momentum of the material which feeds the black hole retains a memory of its original gas source at least to some small, non-negligible degree.

show abstract

The European Space Agency's LISA mission study: status and present results

Cited by 8 publications

References 2 publications

Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7

Host galaxy-active galactic nucleus alignments in the Sloan Digital Sky Survey Data Release 7

Simulations of imaging the event horizon of Sagittarius A* from space

Host galaxy-active galactic nucleus alignments in the SDSS-DR7

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