Galactic Bulge microlensing optical depth from EROS-2

Hamadache, C.; Guillou, L. Le; Tisserand, Patrick; Afonso, C.; Albert, J.; Andersen, J.; Ansari, R.; Aubourg, É.; Bareyre, P.; Beaulieu, J. P.; Charlot, X.; Coutures, C.; Ferlet, R.; Fouqué, P.; Glicenstein, J. F.; Goldman, B.; Gould, Andrew; Graff, D.; Gros, M.; Haïssinski, J.; Kat, J. de; Lesquoy, É.; Loup, C.; Magneville, C.; Marquette, J. B.; Maurice, É.; Maury, A.; Milsztajn, A.; Moniez, M.; Palanque-Delabrouille, N.; Perdereau, O.; Rahal, Y. R.; Rich, Jeffrey A.; Spiro, M.; Vidal‐Madjar, A.; Vigroux, L.; Zylberajch, S.

doi:10.1051/0004-6361:20064893

Cited by 95 publications

(185 citation statements)

References 37 publications

(75 reference statements)

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“…To explain this discrepancy, Kiraga & Paczynski (1994) suggested that the Galactic bulge could give a substantial contribution to the optical depth and thus they included this contribution in their calculations. Theoretical estimates with these new models agree well with the more recent measurements of the optical depth, τ = 2.17 × 10 −6 (Popowski et al 2005, the MACHO group), τ = 2.55 × 10 −6 (Sumi et al 2006, the OGLE-2 group) and τ = 1.62 × 10 −6 (Hamadache et al 2006, the EROS-2 group).…”

Section: Introductionsupporting

confidence: 83%

Probing isolated compact remnants with microlensing

Sartore

Treves

2010

A&A

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Aims. We consider isolated compact remnants (ICoRs), i.e. neutrons stars and black holes that do not reside in binary systems and therefore cannot be detected as X-ray binaries. ICoRs may represent ∼5 percent of the stellar mass budget of the Galaxy, but they are very hard to detect. Here we explore the possibility of using microlensing to identify ICoRs. Methods. In a previous paper we described a simulation of neutron star evolution in phase space in the Galaxy, taking into account the distribution of the progenitors and the kick at formation. Here we first reconsider the evolution and distribution of neutron stars and black holes with an added a bulge component. From the new distributions we calculate the microlensing optical depth, event rate and distribution of event time scales, comparing and contrasting the case of ICoRs and "normal stars". Results. We find that the contribution of remnants to optical depth is slightly lower than without kinematics, owing to the evaporation from the Galaxy. On the other hand, the relative contribution to the rate of events is a factor ∼5 higher. In all, ∼6−7 percent of the events are likely related to ICoRs. In particular, ∼30−40 percent of the events with duration >100 days are possibly related to black holes. Conclusions. It seems therefore that microlensing observations are a suitable tool to probe the population of Galactic ICoRs.

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Section: Introductionsupporting

confidence: 83%

Probing isolated compact remnants with microlensing

Sartore

Treves

2010

A&A

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“…Besides the Magellanic results presented here, EROS-2 has also published measurements of the optical depth toward the Galactic Bulge (Afonso et al 2003b;Hamadache et al 2006). The measured optical depth is in agreement with that measured by MACHO (Popowski et al 2005), and OGLE-2 (Sumi et al 2006) and with the predictions of Galactic models (Evans & Belokurov 2002;Bissantz & Gerhard 2002;Han & Gould 2003;Wood & Mao 2005).…”

Section: Introductionmentioning

confidence: 86%

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Tisserand

Guillou

Afonso

et al. 2007

A&A

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Aims. The EROS-2 project was designed to test the hypothesis that massive compact halo objects (the so-called "machos") could be a major component of the dark matter halo of the Milky Way galaxy. To this end, EROS-2 monitored over 6.7 years 33 × 10 6 stars in the Magellanic clouds for microlensing events caused by such objects. Methods. In this work, we use only a subsample of 7 × 10 6 bright stars spread over 84 deg 2 of the LMC and 9 deg 2 of the SMC. The strategy of using only bright stars helps to discriminate against background events due to variable stars and allows a simple determination of the effects of source confusion (blending). The use of a large solid angle makes the survey relatively insensitive to effects that could make the optical depth strongly direction dependent. Results. Using this sample of bright stars, only one candidate event was found, whereas ∼39 events would have been expected if the Halo were entirely populated by objects of mass M ∼ 0.4 M . Combined with the results of EROS-1, this implies that the optical depth toward the Large Magellanic Cloud (LMC) due to such lenses is τ < 0.36 × 10 −7 (95% CL), corresponding to a fraction of the halo mass of less than 8%. This optical depth is considerably less than that measured by the MACHO collaboration in the central region of the LMC. More generally, machos in the mass range 0.6 × 10 −7 M < M < 15 M are ruled out as the primary occupants of the Milky Way Halo.

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“…(7), must be compared with the observations. For that purpose, we used data collected by several leading collaborations, in particular MACHO (Popowski et al 2005), EROS (Hamadache et al 2006), OGLE (Sumi et al 2006), and MOA (Sumi & et al 2003). These data were collected and analysed in detail in a review (Moniez 2010).…”

Section: Datamentioning

confidence: 99%

Constraining the vertical structure of the Milky Way rotation by microlensing in a finite-width global disk model

Jałocha

Sikora²,

Bratek

et al. 2014

A&A

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We model the vertical structure of mass distribution of the Milky Way galaxy in the framework of a finite-width global disk model. Assuming only the Galactic rotation curve, we tested the predictions of the model inside the solar orbit for two measurable processes that are unrelated to each other: the gravitational microlensing that allows one to fix the disk width-scale by the best fit to measurements, and the vertical gradient of rotation modeled in the quasi-circular orbits approximation. The former is sensitive to the gravitating mass in compact objects, the latter to all kinds of gravitating matter. The analysis points to a small width-scale of the considered disks and an at-most insignificant contribution of non-baryonic dark matter in the solar circle. The predicted high vertical gradient values in the rotation are consistent with the gradient measurements.

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Galactic Bulge microlensing optical depth from EROS-2

Cited by 95 publications

References 37 publications

Probing isolated compact remnants with microlensing

Probing isolated compact remnants with microlensing

Limits on the Macho content of the Galactic Halo from the EROS-2 Survey of the Magellanic Clouds

Constraining the vertical structure of the Milky Way rotation by microlensing in a finite-width global disk model

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