A search for gravitational microlensing towards M31

Details A search for gravitational microlensing towards M31 A search for gravitational microlensing towards M31

Oct 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002phdt.........3u&link_type=abstract

Thesis (PhD). COLUMBIA UNIVERSITY, Source DAI-B 63/04, p. 1891, Oct 2002, 113 pages.

Astronomy and Astrophysics

Astrophysics

1

Scientific paper

Determining the composition of the dark matter which constitutes the majority of the mass of the universe is amongst the greatest challenges in astrophysics. In this thesis, we present the results from four years (1996 1999) of data collected during the Columbia/VATT survey for gravitational microlensing by massive compact halo objects (MACHOS) towards the Andromeda Galaxy (M31). Applying a novel image processing technique, difference image photometry (DIP), developed to detect flux variability in unresolved stellar fields we have discovered 27 microlensing events (five of which cannot be excluded as possible Mira variables) with timescales of 5 ≤ tfwhm < 150 days (t¯fwhm ˜ 31.7 days). The spatial distribution of events is compared to models of expected event rates and is found to rule out a microlensing signal due solely to known stellar populations (self-lensing) at a high significance level (>5-σ). A maximum-likelihood analysis suggests the presence of a dark matter halo with 10% ≲ fb ≲ 29%.

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