Multimessenger astronomy with the Einstein Telescope

Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope. Minor corrections include

Data Analysis Challenges for the Einstein Telescope

The Einstein Telescope is a proposed third generation gravitational wave detector that will operate in the region of 1 Hz to a few kHz. As well as the inspiral of compact binaries composed of neutron stars or black holes, the lower frequency cut-off of the detector will open the window to a number of new sources. These will include the end stage of inspirals, plus merger and ringdown of intermediate mass black holes, where the masses of the component bodies are on the order of a few hundred solar masses. There is also the possibility of observing intermediate mass ratio inspirals, where a stellar mass compact object inspirals into a black hole which is a few hundred to a few thousand times more massive. In this article, we investigate some of the data analysis challenges for the Einstein Telescope such as the effects of increased source number, the need for more accurate waveform models and the some of the computational issues that a data analysis strategy might face.Comment: 18 pages, Invited review for Einstein Telescope special edition of GR

Sensitivity Studies for Third-Generation Gravitational Wave Observatories

Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope, a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this article we describe sensitivity models for the Einstein Telescope and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.Comment: 13 pages, 7 picture

Effect of metallicity on the gravitational-wave signal from the cosmological population of compact binary coalescences

Recent studies on stellar evolution have shown that the properties of compact objects strongly depend on the metallicity of the environment in which they were formed. Using some very simple assumptions on the metallicity of the stellar populations, we explore how this property affects the unresolved gravitational-wave background from extragalactic compact binaries. We obtained a suit of models using population synthesis code, estimated the gravitational-wave background they produce, and discuss its detectability with second- (advanced LIGO, advanced Virgo) and third- (Einstein Telescope) generation detectors. Our results show that the background is dominated by binary black holes for all considered models in the frequency range of terrestrial detectors, and that it could be detected in most cases by advanced LIGO/Virgo, and with Einstein Telescope with a very high signal-to-noise ratio. The observed peak in a gravitational wave spectrum depends on the metallicity of the stellar population.Comment: 9 pages, 5 figures, accepted to A&

Discovery of Multiply Imaged Galaxies behind the Cluster and Lensed Quasar SDSS J1004+4112

We have identified three multiply imaged galaxies in Hubble Space Telescope images of the redshift z=0.68 cluster responsible for the large-separation quadruply lensed quasar, SDSS J1004+4112. Spectroscopic redshifts have been secured for two of these systems using the Keck I 10m telescope. The most distant lensed galaxy, at z=3.332, forms at least four images, and an Einstein ring encompassing 3.1 times more area than the Einstein ring of the lensed QSO images at z=1.74, due to the greater source distance. For a second multiply imaged galaxy, we identify Ly_alpha emission at a redshift of z=2.74. The cluster mass profile can be constrained from near the center of the brightest cluster galaxy, where we observe both a radial arc and the fifth image of the lensed quasar, to the Einstein radius of the highest redshift galaxy, ~110 kpc. Our preliminary modeling indicates that the mass approximates an elliptical body, with an average projected logarithmic gradient of ~-0.5. The system is potentially useful for a direct measurement of world models in a previously untested redshift range.Comment: 5 pages, 3 figures. Accepted by ApJL. High resolution version of the paper can be found at: http://wise-obs.tau.ac.il/~kerens/papers.htm