Ground-based variability surveys towards Centaurus A: worthwhile or not?

Details Ground-based variability surveys towards Centaurus A: worthwhile or not? Ground-based variability surveys towards Centaurus A: worthwhile or not?

2007-12-07

arxiv.org/abs/0712.1052v1

A&A 478, 755-762 (2008)

Astronomy and Astrophysics

Astrophysics

8 pages, 7 figures, accepted for publication in Astronomy and Astrophysics

Scientific paper

10.1051/0004-6361:20078378

Context: Difference imaging has proven to be a powerful technique for detecting and monitoring the variability of unresolved stellar sources in M 31. Using this technique in surveys of galaxies outside the Local Group could have many interesting applications. Aims: The goal of this paper is to test difference imaging photometry on Centaurus A, the nearest giant elliptical galaxy, at a distance of 4 Mpc. Methods: We obtained deep photometric data with the Wide Field Imager at the ESO/MPG 2.2m at La Silla spread over almost two months. Applying the difference imaging photometry package DIFIMPHOT, we produced high-quality difference images and detected variable sources. The sensitivity of the current observational setup was determined through artificial residual tests. Results: In the resulting high-quality difference images, we detect 271 variable stars. We find a difference flux detection limit corresponding to m_R~24.5. Based on a simple model of the halo of Centaurus A, we estimate that a ground-based microlensing survey would detect in the order of 4 microlensing events per year due to lenses in the halo. Conclusions: Difference imaging photometry works very well at the distance of Centaurus A and promises to be a useful tool for detecting and studying variable stars in galaxies outside the local group. For microlensing surveys, a higher sensitivity is needed than achieved here, which would be possible with a large ground-based telescope or space observatory with wide-field imaging capabilities.

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