Open AccessMicrolensing in the Small Magellanic Cloud: lessons from an N ‐body simulation
Author(s) -
Graff David S.,
Gardiner Lance T.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02665.x
Subject(s) - gravitational microlensing , physics , small magellanic cloud , large magellanic cloud , astrophysics , stars , optical depth , gravitational lens , line of sight , mass distribution , astronomy , galaxy , aerosol , redshift , meteorology
We analyse an N ‐body simulation of the Small Magellanic Cloud (SMC), that of Gardiner & Noguchi, to determine its microlensing statistics. We find that the optical depth owing to self‐lensing in the simulation is low, 0.4×10 −7 , but still consistent (at the 90 per cent level) with that observed by the EROS and MACHO collaborations. This low optical depth is due to the relatively small line‐of‐sight thickness of the SMC produced in the simulation. The proper motions and time‐scales of the simulation are consistent with those observed assuming a standard mass function for stars in the SMC. The time‐scale distribution from the standard mass function generates a significant fraction of short time‐scale events: future self‐lensing events towards the SMC may have the same time‐scales as events observed towards the Large Magellanic Cloud (LMC). Although some debris was stripped from the SMC during its collision with the LMC about 2×10 8 yr ago, the optical depth of the LMC owing to this debris is low, a few ×10 −9 , and thus cannot explain the measured optical depth towards the LMC.