Related papers: Recent developments in the search for baryonic dar…
By means of extensive galactic modeling we study the implications of the more than eighty microlensing events that have now been observed for the composition of the dark halo of the Galaxy, as well as for other properties of the Galaxy. We…
Results are presented from the MACHO collaboration gravitational microlensing search. The experiment and the nearly 50 microlensing events that have been detected are described. Limits on the baryonic content of the halo are given, as are…
It has been argued in a number of recent papers that dark matter is in the form of Jupiter mass primordial black holes which betray their presence by microlensing quasars. This lensing accounts for a number of characteristic properties of…
The dark matter in Galactic halos, or some fraction of it, may be in the form of dark clusters which consist of small mass objects. Carr & Lacey (1987) have derived the permissible properties of such systems, and proposed the existence of…
We propose a novel class of compact dark matter objects in theories where the dark matter consists of multiple sectors. We call these objects $N$-MACHOs. In such theories neither the existence of dark matter species nor their extremely weak…
We study the formation and properties of dark neutron stars in a scenario where dark matter is made up of (heavy) dark baryons in a sequestered copy of the MSSM. This scenario naturally explains the coincidence of baryonic and dark matter…
Recent HST and ISO observations provide very severe limits on any compact baryonic contributions to galactic (dark) halos. When combined with Milky Way Galaxy microlensing results, almost the entire plausible range of massive compact…
Fifteen years or so ago, it was commonly argued; ``If we want to believe the observations rather than our prejudice, we should take as our best bet that dark haloes are baryonic.'' Such a viewpoint is not often heard today. This…
Microlensing is the tool of choice for the search and the analysis of compact halo objects ("MACHOs"), a still viable class of dark matter candidates at the galactic scale. Different analyses point towards an agreement in excluding dark…
The MACHO collaboration lensing event statistics suggest that a significant fraction of the dark galactic halo can be comprised of baryonic matter in the form of white dwarf stars with masses between 0.1 and 1.0 \Msun . Such a halo white…
The MACHO Project monitors millions of stars in the Large Magellanic Cloud, the Small Magellanic Cloud and the bulge of the Milky Way searching for the gravitational microlensing signature of baryonic dark matter. This Project has yielded…
We review some recent determinations of the amount of dark matter on galactic, cluster, and large scales, noting some puzzles and their possible resolutions. We discuss the interpretation of big bang nucleosynthesis for dark matter, and…
Massive Compact objects in the halo, known as MACHOs, have been postulated as the origin of a substantial fraction of `dark matter' known to exist in the haloes of galaxies$^{1,2}$. Paczy\'nski$^3$ has suggested that it might possible to…
We consider the contribution of neutron stars and black holes to the dynamical mass of galactic halos. In particular, we show that if these compact objects were produced by an early generation of stars with initial metallicity less than…
Dark matter is a vital component of the current best model of our universe, $\Lambda$CDM. There are leading candidates for what the dark matter could be (e.g. weakly-interacting massive particles, or axions), but no compelling observational…
Deep optical/near-IR surface photometry of galaxies outside the Local Group have revealed faint and very red halos around objects as diverse as disk galaxies and starbursting dwarf galaxies. The colours of these structures are too extreme…
The idea that dark matter in the form of small compact bodies (most plausibly planetary mass primordial black holes) betrays its presence by the microlensing of quasars, has been stimulated by statistical studies of quasar light curves and…
We discuss the tight interconnection between microlensing optical depths, flattening of dark haloes and low-to-intermediate redshift baryonic census. By analysing plots of the microlensing optical depth as a function of galactic coordinates…
The evidence for the existence of dark matter in the universe is reviewed. A general picture emerges, where both baryonic and non-baryonic dark matter is needed to explain current observations. In particular, a wealth of observational…
Recent results from gravitational microlensing experiments, such as MACHO, indicate that a substantial fraction of the Galactic dark matter (DM) is in compact form, with a typical mass in the range ~0.05 - 1 Mo. This mass range favours the…