Search

We present deep 450 and $850 \mu$m SCUBA images of the nearby spiral galaxy NGC 7331. Using the submillimeter emissivity inferred from COBE observations of Milky Way dust, we convert our SCUBA images into maps of optical depth. The opacity derived in this way is quite low at the visible limit of NGC 7331 ($\tau_{B}\leq 0.22$at the R25radius for the disk seen face-on). In a similar fashion, we exploit SCUBA and ISOPHOT images of a further 10 galaxies and, collectively, these data indicate $\tau_{B}=0.1$-0.2 at the R25radius. Our constraints on disk opacity are fed into a simulation of how light emanating from high redshifts is attenuated by foreground spirals. In making this calculation, we consider the possibility that galactic disks may have also contained different dust masses in the past. We estimate that less than 10% of the light emitted by Hubble Deep Field galaxies fails to reach the B-band observer due to intervening spirals.

Gravitational waves from coalescing compact binaries are searched for using the matched filtering technique. As the model waveform depends on a number of parameters, it is necessary to filter the data through a template bank covering the astrophysically interesting region of the parameter space. The choice of templates is defined by the maximum allowed drop in signal-to-noise ratio due to the discreteness of the template bank. In this paper we describe the template-bank algorithm that was used in the analysis of data from the Laser Interferometer Gravitational Wave Observatory (LIGO) and GEO 600 detectors to search for signals from binaries consisting of non-spinning compact objects. Using Monte Carlo simulations, we study the efficiency of the bank and show that its performance is satisfactory for the design sensitivity curves of ground-based interferometric gravitational wave detectors GEO 600, initial LIGO, advanced LIGO and Virgo. The bank is efficient in searching for various compact binaries such as binary primordial black holes, binary neutron stars, binary black holes, as well as a mixed binary consisting of a non-spinning black hole and a neutron star.

Of all the large interferometric gravitational-wave detectors, the German/British project GEO600 is the only one which uses dual recycling. During the four weeks of the international S4 data-taking run it reached an instrumental duty cycle of 97% with a peak sensitivity of 7 × 10?22Hz?1/2at 1 kHz. This paper describes the status during S4 and improvements thereafter.

The GEO 600 gravitational wave detector uses advanced technologies including signal recycling and monolithic fused-silica suspensions to achieve a sensitivity close to the kilometre scale LIGO and VIRGO detectors. As soon as the design sensitivity of GEO 600 is reached, the detector will be operated as part of the worldwide network to acquire data of scientific interest. The limited infrastructure at the GEO site does not allow for a major upgrade of the detector. Hence the GEO collaboration decided to improve the sensitivity of the GEO detector by small sequential upgrades some of which will be tested in prototypes first. The development, test and installation of these upgrades are named 'The GEO-HF Project.' This paper describes the upgrades considered in the GEO-HF project as well as their scientific reasons. We will describe the changes in the GEO 600 infrastructure and the prototype work that is planned to support these upgrades. Finally, we will point to some laboratory research that identifies new technologies or optical configurations that might undergo a transition into detector subsystems within the GEO-HF project.

Since December 2003, the gravitational-wave detector GEO 600 has routinely operated in the dual recycled mode, using a lock acquisition scheme based on the detection of optical sideband power at the dark port. With the detector locking very robustly, the current commissioning work is entirely dedicated to sensitivity improvements. We give a brief overview of the GEO 600 detector, the implementation of dual recycling, and summarize recent work regarding the increase in the detector sensitivity.

A world-wide network of interferometric gravitational wave detectors is currently operational. The detectors in the network are still in their commissioning phase and are expected to achieve their design sensitivity over the next year or so. Each detector is a complex instrument involving many optical, mechanical and electronic subsystems and each subsystem is a source of noise at the output of the detector. Therefore, in addition to recording the main gravitational wave data channel at the output of the interferometer, the state of each detector subsystem is monitored and recorded. The analysis of these subsidiary data serves a dual purpose: first, it helps us to identify the primary sources of noise which could then be either removed altogether or reduced substantially and second, it helps us in vetoing spurious signals at the output of the interferometer. However, since these subsidiary data are both large in volume (1 MB s?1) as well as complex in nature, it is not possible to look at all these data manually. We require an online monitoring and analysis tool which can process all the data channels for various noise artefacts such as transients, drifting of narrowband noise sources, noise couplings between data channels etc, and summarize the results of the analysis in a manner that can be accessed and interpreted conveniently. In this paper we describe the GEO 600 online detector characterization system (GODCS), which is the tool that is being used to monitor the output of the GEO 600 gravitational wave detector situated near Hanover in Germany. We describe the various algorithms that we use and how the results of several algorithms can be combined to make meaningful statements about the state of the detector. We also give implementation details such as the software architecture and the storage and retrieval of the output of GODCS. This paper will be useful to researchers in the area of gravitational wave astronomy as a record of the various analyses and checks carried out to ensure the quality and reliability of the data before searching the data for the presence of gravitational waves.