Self-Lensing by a Stellar Disk
Abstract
I derive a general expression for the optical depth τ for gravitational lensing of stars in a disk by massive compact objects (MACHOS) in the same disk. For the more restricted case where the disk is self-gravitating and the stars and MACHOS have the same distribution function, I find τ = 2(ν^2^)/c^2^ sec^2^ i, where <ν^2^> is the mass-weighted vertical velocity dispersion and i is the angle of inclination. This result does not depend on any assumptions about the velocity distribution. As an example, if stars within the bar of the Large Magellanic Cloud (LMC) account for the observed optical depth τ ~ 8 x 10^-8^ as has recently been suggested, then ν ~> 60 km s^-1^. This is substantially larger than the measured dispersions of known LMC populations.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1995
- DOI:
- 10.1086/175337
- arXiv:
- arXiv:astro-ph/9408004
- Bibcode:
- 1995ApJ...441...77G
- Keywords:
-
- Disk Galaxies;
- Gravitational Lenses;
- Magellanic Clouds;
- Optical Thickness;
- Brown Dwarf Stars;
- Mass Distribution;
- Velocity Distribution;
- Astronomy;
- COSMOLOGY: DARK MATTER;
- COSMOLOGY: GRAVITATIONAL LENSING;
- STARS: LOW-MASS;
- BROWN DWARFS;
- Astrophysics
- E-Print:
- 6 pages, no figures, phyzzx macro package, or request PostScript file to gould@payne.mps.ohio-state.edu, OSU-TA-13/94