Related papers: Hydrogen Clouds and the MACHO/EROS Events
Recently the Polish-American collaboration OGLE has reported the observation of four possible microlensing events by monitoring, over several months, the brightness of millions of stars in the region of the galactic bulge. If these events…
While recent detections of gravitational waves from the mergers of binary black holes match well with the predictions of General Relativity (GR), they cannot directly confirm the existence of event horizons. Exotic compact objects (ECOs)…
A significant fraction of non-baryonic or baryonic dark matter in galactic halos may consist of MASsive Compact Objects (MASCOs) with mass M=10^{1-4}M_{sun}. Possible candidates for such compact objects include primordial black holes or…
The EROS and MACHO collaborations have each published upper limits on the amount of planetary mass dark matter in the Galactic Halo obtained from gravitational microlensing searches. In this paper the two limits are combined to give a much…
We present a new analysis of the results of the EROS-2, OGLE-II, and OGLE-III microlensing campaigns towards the Small Magellanic Cloud (SMC). Through a statistical analysis we address the issue of the \emph{nature} of the reported…
A new type of gravitational microlensing experiment toward a field where stars are not resolved is being developed observationally and theoretically: pixel lensing. When the experiment is carried out toward the M31 bulge area, events may be…
The POINT-AGAPE collaboration is carrying out a search for gravitational microlensing toward M31 to reveal galactic dark matter in the form of MACHOs (Massive Astrophysical Compact Halo Objects) in the halos of the Milky Way and M31. A…
It has been suggested ``that DM particles are strongly interacting composite macroscopically large objects ... made of well known light quarks (or ... antiquarks)." In doing so it is argued that these compact composite objects (CCOs) are…
The standard treatment of cooling in Cold Dark Matter halos assumes that all of the gas within a ``cooling radius'' cools and contracts monolithically to fuel galaxy formation. Here we take into account the expectation that the hot gas in…
The light curves of the two images of the double quasar Q0957+561 as obtained by Kundic et al. (1997) are almost identical, except for an overall time delay and scaling factor. This allows us to put limits on the amount of microlensing that…
We discuss the implications of the recent upward revision of the LMC microlensing rate by the MACHO Collaboration. We conclude: (i) A good case for the existence of baryonic dark matter in the halo has been made; (ii) The case for the…
We present the results from the OGLE-II survey (1996-2000) towards the Large Magellanic Cloud (LMC), which has the aim of detecting the microlensing phenomena caused by dark matter compact objects in the Galactic Halo (Machos). We use high…
This short report is concerned with the well known and not yet satisfactorily answered problem of the existence of two well distinct typical mass scales of primordial halo objects: solar size objects (halo field stars) and globular cluster…
Reasons supporting the idea that most of the dark matter in galaxies and clusters of galaxies is baryonic is discussed. Moreover it is argued that most of the dark matter in galactic halo should be in the form of MACHOs and cold molecular…
The EROS-2 collaboration has conducted a survey of the Magellanic Clouds between July 1996 and February 2003 (6.7 years), in order to search for microlensing phenomena due to putative machos (massive astronomical compact halo objects).…
As a cold dark matter candidate, the QCD axion may form Bose-Einstein condensates, called axion stars, with masses around $10^{-11}\,M_{\odot}$. In this paper, we point out that a brand new astrophysical object, a Hydrogen Axion Star (HAS),…
Many of the baryons in our Galaxy probably lie outside the well known disk and bulge components. Despite a wealth of evidence for the presence of some gas in galactic halos, including absorption line systems in the spectra of quasars, high…
In the third part of the series presenting the Optical Gravitational Lensing Experiment (OGLE) microlensing studies of the dark matter halo compact objects (MACHOs) we describe results of the OGLE-III monitoring of the Large Magellanic…
Modelling of Extreme Scattering Events suggests that the Galaxy's dark matter is an undetected population of cold, AU-sized, planetary-mass gas clouds. None of the direct observational constraints on this picture -- thermal/non-thermal…
Potential condensed clouds of gas in the Galactic halo are examined in the context of the recent models of cooling, fragmenting clouds building up the baryonic mass of the Galaxy. 582 high-velocity clouds (HVCs) are defined as the potential…