The Microlensing Event Rate and Optical Depth Toward the Galactic Bulge From Moa-Ii

Sumi, T.; Bennett, D. P.; Bond, I. A.; Abe, F.; Botzler, C. S.; Fukui, A.; Furusawa, K.; Itow, Y.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Ohnishi, Kouhei; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Wada, K.; Yock, P. C. M.

doi:10.1088/0004-637x/778/2/150

Cited by 99 publications

(165 citation statements)

References 56 publications

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“…The present microlensing search covers the three most central VVV tiles, and can, in principle, be extended to adjacent areas that have not yet been studied due to heavy extinction. Such extended search would produce a complete timescale distribution map of the inner Milky Way bulge and show the dependencies with Galactic latitude and longitude, to complement previous bulge microlensing studies (e.g., Popowski et al 2005;Sumi et al 2013;Wyrzykowski et al 2015).…”

Section: Discussionmentioning

confidence: 77%

“…For the latter, the distribution of timescales can be useful to test the different possible scenarios for the structure and evolution of the inner part of the Galaxy (Calchi Novati et al 2008;Sumi et al 2013). We note that as the timescale is a degenerate combination of lens mass, and lens-source relative parallax and proper motion, it is necessary to include Galactic models related to specific populations.…”

Section: Introductionmentioning

confidence: 99%

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VVV Survey Microlensing Events in the Galactic Center Region

Navarro

Minniti

Ramos

2017

ApJL

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We search for microlensing events in the highly reddened areas surrounding the Galactic center using the near-IR observations with the VISTA Variables in the Vía Láctea Survey (VVV). We report the discovery of 182 new microlensing events, based on observations acquired between 2010 and 2015. We present the color-magnitude diagrams of the microlensing sources for the VVV tiles b332, b333, and b334, which were independently analyzed, and show good qualitative agreement among themselves. We detect an excess of microlensing events in the central tile b333 in comparison with the other two tiles, suggesting that the microlensing optical depth keeps rising all the way to the Galactic center. We derive the Einstein radius crossing time for all of the observed events. The observed event timescales range from t E = 5 to 200 days. The resulting timescale distribution shows a mean timescale of t 30.91 E á ñ = days for the complete sample (N = 182 events), and t 29.93 E á ñ = days if restricted only for the red clump (RC) giant sources (N = 96 RC events). There are 20 long timescale events (t 100 E  days) that suggest the presence of massive lenses (black holes) or disk-disk event. This work demonstrates that the VVV Survey is a powerful tool to detect intermediate/long timescale microlensing events in highly reddened areas, and it enables a number of future applications, from analyzing individual events to computing the statistics for the inner Galactic mass and kinematic distributions, in aid of future ground-and space-based experiments.

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Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

VVV Survey Microlensing Events in the Galactic Center Region

Navarro

Minniti

Ramos

2017

ApJL

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“…The Bulge mass has to satisfy microlensing constraints (see e.g Sumi et al 2013) and ought to affect the Dark Matter density distribution as the halo reacts to the presence of baryons in the inner Galaxy (see e.g. Cole & Binney 2016).…”

Section: Discussionmentioning

confidence: 99%

A parametric description of the 3D structure of the Galactic bar/bulge using the VVV survey

Simion

Belokurov

Irwin

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We study the structure of the inner Milky Way (MW) using the latest data release of the Vista Variables in Via Lactea (VVV) survey. The VVV is a deep near-infrared, multi-colour photometric survey with a coverage of 300 square degrees towards the Bulge/Bar. We use Red Clump (RC) stars to produce a high-resolution dust map of the VVV's field of view. From de-reddened colour-magnitude diagrams we select Red Giant Branch stars to investigate their 3D density distribution within the central 4 kpc. We demonstrate that our best-fit parametric model of the Bulge density provides a good description of the VVV data, with a median percentage residual of 5 % over the fitted region. The strongest of the otherwise low-level residuals are overdensities associated with a low-latitude structure as well as the so-called X-shape previously identified using the split RC. These additional components contribute only ∼ 5% and ∼ 7% respectively to the Bulge mass budget. The best-fit Bulge is "boxy" with an axis ratio of [1:0.44:0.31] and is rotated with respect to the Sun-Galactic Centre line by at least ∼ 20• . We provide an estimate of the total, full sky, mass of the Bulge of M Chabrier Bulge = 2.36 × 10 10 M for a Chabrier initial mass function. We show there exists a strong degeneracy between the viewing angle and the dispersion of the Red Clump (RC) absolute magnitude distribution. The value of the latter is strongly dependent on the assumptions made about the intrinsic luminosity function of the Bulge.

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“…Additionally, the event rate gives us information about the structure of the bulge (e.g., Kiraga & Paczyński 1994). The connection between statistics of observed events and the structure of the bulge is an area of active research (Kerins et al 2009;Sumi et al 2013; ⋆ E-mail: poleski.1@osu.edu Wyrzykowski et al 2015), but a full understanding of microlensing event rate has not yet been achieved.…”

Section: Introductionmentioning

confidence: 99%

Empirical microlensing event rates predicted by a phenomenological model

Poleski

2015

Mon. Not. R. Astron. Soc.

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Estimating the number of microlensing events observed in different parts of the Galactic bulge is a crucial point in planning microlensing experiments.Reliable estimates are especially important if observing resources are scarce, as is the case for space missions: K2, WFIRST, and Euclid. Here we show that the number of detected events can be reliably estimated based on statistics of stars observed in targeted fields. The statistics can be estimated relatively easily, which makes presented method suitable for planning future microlensing experiments.

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The Microlensing Event Rate and Optical Depth Toward the Galactic Bulge From Moa-Ii

Cited by 99 publications

References 56 publications

VVV Survey Microlensing Events in the Galactic Center Region

VVV Survey Microlensing Events in the Galactic Center Region

A parametric description of the 3D structure of the Galactic bar/bulge using the VVV survey

Empirical microlensing event rates predicted by a phenomenological model

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