The MACHO Project: Microlensing Results from 5.7 Years of Large Magellanic Cloud Observations

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Dalal, Neal; Drake, A. J.; Freeman, K. C.; Geha, Marla; Griest, K.; Lehner, M. J.; Marshall, S.; Minniti, D.; Nelson, C A; Peterson, Bruce A.; Popowski, Piotr; Pratt, M. R.; Quinn, Peter J.; Stubbs, C. W.; Sutherland, William J.; Tomaney, A.; Vandehei, T.; Welch, D. L.

doi:10.1086/309512

Cited by 917 publications

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“…The original published data from the MACHO project are used to reanalyze the presence of MACHOs in the galactic halo (Alcock et al 2000a). All mathematical calculations follow strict standard algebraic and standard mathematical rules.…”

Section: Mathematical Methodsmentioning

confidence: 99%

“…In the 2000 paper of the MACHO project, microlensing detection was quite correctly based upon the detection of single lensing objects only. That is because these events can definitively be labelled as microlesning objects (Alcock et al 2000a). However, the detection efficiency was not adjusted for the possibility that the galactic halo could contain many binary systems.…”

Section: Optical Depth and Detection Efficiencymentioning

confidence: 99%

“…In that review, a wide range of experimental evidence from quasar brightness, spectral variations, and multiply lensed quasar systems, and the MACHO project itself, support the presence of primordial black holes in galactic halos (Hawkins 2011). Indeed, results from the MACHO project indicate that the mass of halo objects predominantly range form 0.5-1 solar masses (Alcock et al 2000a). This would of course exclude ordinary black holes, whose mass ranges are above 3 solar masses.…”

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confidence: 99%

“…They also technically agree exactly with binary pulsar data (Worsley 2009). Perhaps the most important advantage is that they do not produce infinite density singularities at the centre of black holes.To establish whether these advanced black hole gravitational mechanisms apply to primordial black holes and can help explain the presence and characteristics of galactic halos, the original data from the MACHO project are used (Alcock et al 2000a). Here this data from the MACHO project are reanalyzed in the light of these new findings, and with the use of the advances in black hole gravitational physics.…”

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confidence: 99%

“…In the light of new findings of the likely presence of primordial black holes in the galactic halo (Hawkins 2011), and advances in black hole physics (Worsley 2008(Worsley , 2009(Worsley , 2011a, a re-examination of this issue is both timely and important. The data from the MACHO project (Alcock et al 2000a), will principally be used and reanalyzed in the context of the advances in knowledge of primordial black holes and black hole physics.The modelling of CDM in the galactic halo is complex, not least as there is little observational data to deduce results from. Beginning with the halo core radius, this is currently estimated at 5 kpc.…”

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confidence: 99%

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Advances in Black Hole Physics and Dark Matter Modelling of the Galactic Halo

Worsley¹

2012

APR

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One of the most important unresolved issues of modern physics is the presence of cold dark matter (CDM). Such dark matter appears to be essential in explaining the observed galactic rotation curves and the missing Cosmological dark matter. Recent attention has focused on galactic halos as an explanation of the galactic rotation curves, and on the possibility that galactic halos may consist of massive compact halo objects (MACHOs). Indeed results of experiment by the MACHO collaboration group have confirmed the presence of MACHOs in the galactic halo at statistically significant levels. What remains unclear is, what percentage of the galactic halo can be explained by such MACHOs, and what these MACHOs are likely to be composed of. Recent research shows the "most plausible" candidates for such MACHOs are being identified as primordial black holes. Such primordial black holes can also explain quasar brightness, spectral variations, and multiply lensed quasar systems. The presence of these primordial black holes in the galactic halo can be further modelled using advances in black hole gravitational physics. Indeed it has previously been shown that advances in black hole physics can be used to accurately model both CDM associated with the supermassive black hole at the centre of the galaxy, and Cosmological cold dark matter. To establish whether the same mechanism applies to primordial black holes in galactic halos, the original data from the MACHO project are reanalyzed using these advances in black hole physics. It is concluded that the majority of the CDM mass of the galactic halo can be accounted for by MACHOs by using a reanalysis of the data, and by applying advances in black hole gravitational physics. Importantly these advances in black hole physics offer further readily testable gravitational predictions.Keywords: Primordial black hole, Gravitation, Black hole physics, Galactic halo, Cold dark matter, Cosmology IntroductionThe presence of CDM remains to date one of the most important unsolved mysteries of modern Cosmology. It is particularly important not only to the understanding of the large scale structure of the Universe, but also in explaining the formation of galaxies. To date the search has concentrated on two main forms of CDM; weakly interactive massive particles (WIMPs), and massive compact halo objects (MACHOs) (Cline 2003). While the presence of WIMPs or some other form of exotic particle is still the favoured model, there has been a recent increase in the interest in MACHOs. Indeed research indicates that the statistical likely hood of MACHOs being present in the galactic halo is high (Alcock et al. 2000a).The question however, remains as to how prevalent these MACHOs are in the galactic halo, and what form do these MACHOs take? Interestingly, a recent comprehensive review suggests that the most "plausible" form these MACHO's take is that of primordial black holes (Hawkins 2011). In that review, a wide range of experimental evidence from quasar brightness, spectral variations, and multip...

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Section: Mathematical Methodsmentioning

confidence: 99%

Section: Optical Depth and Detection Efficiencymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Advances in Black Hole Physics and Dark Matter Modelling of the Galactic Halo

Worsley¹

2012

APR

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Gravitational lensing as a powerful astrophysical tool: Multiple quasars, giant arcs and extrasolar planets

Wambsganß

2006

Ann. Phys.

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In the 25 years since the discovery of the first double quasar Q0957+561, gravitational lensing has established itself as a valuable tool in many branches of astronomy. Fields as different as galactic structure, cosmology, or extrasolar planets benefit from the gravitational lensing effect. This article starts with a brief historic reflection, then the basics of light deflection are reviewed. Observable lensing effects and a few examples of strong lensing phenomena are shown. In the main part four applications of "strong" lensing will be presented and discussed:• The determination of the Hubble constant from time delay measurements in multiple quasars; it is argued that this method of determining H0 is competitive with other methods by now. The lensing-derived values of H0 are on the low side.• Microlensing of quasars -the effects of compact stellar-mass objects on the apparent brightness -allows us to constrain the quasar size and the occurrence of dark matter objects.• The frequency of giant luminous arcs strongly depends on the high mass end of the galaxy cluster distribution. Recent investigations show that arc statistics is in agreement with the concordance cosmological model.• Searching for extrasolar planets is one of the most recent applications of gravitational lensing. The first detection shows that the method works well. This planet-search method is complementary to other programs and has the potential to detect exo-planets with lower masses than other ground-based techniques. An outlook is provided on the prospects of gravitational lensing in the next few years. In particular the magnification effect on faint high-redshift sources will be used for the investigation of the early universe, and the detection of low-mass extrasolar planets will provide a valuable sample for statistical evaluations of the frequency of exoplanets.

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Gravitational lensing as a powerful astrophysical tool: Multiple quasars, giant arcs and extrasolar planets

Wambsganß

2005

Annalen der Physik

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In the 25 years since the discovery of the first double quasar Q0957+561, gravitational lensing has established itself as a valuable tool in many branches of astronomy. Fields as different as galactic structure, cosmology, or extrasolar planets benefit from the gravitational lensing effect. This article starts with a brief historic reflection, then the basics of light deflection are reviewed. Observable lensing effects and a few examples of strong lensing phenomena are shown. In the main part four applications of ''strong'' lensing will be presented and discussed: The determination of the Hubble constant from time delay measurements in multiple quasars; it is argued that this method of determining H0 is competitive with other methods by now. The lensing‐derived values of H0 are on the low side. Microlensing of quasars– the effects of compact stellar‐mass objects on the apparent brightness – allows us to constrain the quasar size and the occurrence of dark matter objects.The frequency of giant luminous arcs strongly depends on the high mass end of the galaxy cluster distribution. Recent investigations show that arc statistics is in agreement with the concordance cosmological model. Searching for extrasolar planets is one of the most recent applications of gravitational lensing. The first detection shows that the method works well. This planet‐search method is complementary to other programs and has the potential to detect exo‐planets with lower masses than other ground‐based techniques.An outlook is provided on the prospects of gravitational lensing in the next few years. In particular the magnification effect on faint high‐redshift sources will be used for the investigation of the early universe, and the detection of low‐mass extrasolar planets will provide a valuable sample for statistical evaluations of the frequency of exoplanets.

show abstract

The MACHO Project: Microlensing Results from 5.7 Years of Large Magellanic Cloud Observations

Cited by 917 publications

References 47 publications

Advances in Black Hole Physics and Dark Matter Modelling of the Galactic Halo

Advances in Black Hole Physics and Dark Matter Modelling of the Galactic Halo

Gravitational lensing as a powerful astrophysical tool: Multiple quasars, giant arcs and extrasolar planets

Gravitational lensing as a powerful astrophysical tool: Multiple quasars, giant arcs and extrasolar planets

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