Observational limits on Omega in stars, brown dwarfs, and stellar remnants from gravitational microlensing

Details Observational limits on Omega in stars, brown dwarfs, and stellar remnants from gravitational microlensing Observational limits on Omega in stars, brown dwarfs, and stellar remnants from gravitational microlensing

Apr 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...424..550d&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 424, no. 2, p. 550-568

Astronomy and Astrophysics

Astronomy

52

Astronomical Models, Brown Dwarf Stars, Cosmology, Emission Spectra, Gravitational Lenses, Mass Distribution, Quasars, Statistical Analysis, Subdwarf Stars, X Ray Astronomy, Density (Mass/Volume), Heao 2, Radio Astronomy, Red Shift, Size (Dimensions), Sky Surveys (Astronomy), Stellar Mass, Ultraviolet Astronomy, Universe

Scientific paper

Microlensing by compact objects with masses between approximately 0.001 solar masses and approximately 300 solar masses will amplify the continuum emission of a quasar, without significantly changing its line emission. Thus, compact objects with masses associated with stars, subdwarfs, and stellar remnants will reduce the apparent equivalent widths of quasar emission lines. It is possible to detect this population of lenses by searching for an increase in the number of small equivalent width quasars with redshift. This increase was looked for, but not found, in quasar samples taken from the Einstein Medium Sensitivity Survey and the Steidel & Sargent absorption-line studies. Thus, Omegac, the cosmological density of compact objects relative to the critical density, is less than or approximately equal to 0.1 in the mass range 0.01 solar masses-20 solar masses (for Omega less than 0.6). For any value of Omega, Omegac less than or approximately equal to 0.2 in the larger mass range 0.001 solar masses-60 solar masses, and Omegac less than 1 for 0.001 solar masses-300 solar masses. Subdwarfs, stellar objects, or their remnants (e.g., MACHOS) cannot close the universe.

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