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

Abstract

view Abstract Citations (72) References (125) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observational Limits on Omega in Stars, Brown Dwarfs, and Stellar Remnants from Gravitational Microlensing Dalcanton, Julianne J. ; Canizares, Claude R. ; Granados, Arno ; Steidel, Charles C. ; Stocke, John T. Abstract Microlensing by compact objects with masses between ~0.001 M_sun_ and 300 M_sun_ 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, {OMEGA}_c_, the cosmological density of compact objects relative to the critical density, is <~0.1 in the mass range 0.01 M_sun_- 20 M_sun_ (for {OMEGA} < 0.6). For any value of {OMEGA}, {OMEGA}_c_ <~0.2 in the larger mass range 0.001 M_sun_-60 M_sun_, and {OMEGA}_c_ < 1 for 0.001 M_sun_-300 M_sun_. Subdwarfs, stellar objects, or their remnants (e.g., MACHOS) cannot close the universe. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/173914 Bibcode: 1994ApJ...424..550D Keywords: 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; Astrophysics; COSMOLOGY: OBSERVATIONS; COSMOLOGY: GRAVITATIONAL LENSING; GALAXIES: QUASARS: GENERAL; STARS: LOW-MASS; BROWN DWARFS full text sources ADS | data products SIMBAD (2)