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

Abstract

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.

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

References in corpus (17)

• A method for optimal image subtraction
• The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
• The MACHO Project: Microlensing Results from 5.7 Years of LMC Observations
• Limits on the Macho Content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds
• Expanding the Realm of Microlensing Surveys with Difference Image Photometry
• The Planetary Nebula System and Dynamics in the Outer Halo of NGC 5128
• The Discovery of Cepheids and a Distance to NGC 5128
• Theory of Pixel Lensing
• POINT-AGAPE Pixel Lensing Survey of M31 : Evidence for a MACHO contribution to Galactic Halos
• The Wendelstein Calar Alto Pixellensing Project(WeCAPP): First MACHO Candidates
• MACHOs in M31? Absence of evidence but not evidence of absence
• Microlensing Candidates in M87 and the Virgo Cluster with the Hubble Space Telescope
• Microlensing toward crowded fields: Theory and applications to M31
• Optical depth evaluation in pixel microlensing
• Long Period Variables in NGC 5128: I. Catalogue
• Event rates and timescale distributions from realistic microlensing models of M31
• Microlensing Surveys of M31 in the Wide Field Imaging Era

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