Angular sizes of faint radio sources and their implications for cosmology
Thesis/Dissertation
·
OSTI ID:6988668
The angular sizes of extragalactic radio sources were studied with the VLA as functions of redshift and flux density in hopes of obtaining information on cosmological parameters and source size evolution. The angular size-redshift test was extended by the discovery of two large-angular-size quasars. One of them effectively eliminates the need for linear size evolution to account for the paucity of large angular size sources at high redshift. The angular size-flux density test was extended to very low flux densities (S/sub 1400/ greater than or equal to 84 ..mu..Jy) by high-resolution observations of an extremely radio-quiet field. The median angular size of extragalactic radio sources drops rapidly from approx. =8 arcsec to <3 arcsec below S approx. = 1 mJy. This falloff cannot be due to size evolution alone because (1) most sources have 0.3 approximately less than or equal to z < 3 and angular size nearly independent of linear size in this redshift range, and (2) is almost independent of S in this flux range. Thus a drop in linear size is implied, which confirms the prediction that a change in the dominant component of the radio source population occurs at about 1 mJy. This observed dropoff in angular size is consistent with most stronger sources being produced by elliptical galaxies, while the fainter sources reside in spiral or Seyfert galaxies.
- Research Organization:
- Pittsburgh Univ., PA (USA)
- OSTI ID:
- 6988668
- Country of Publication:
- United States
- Language:
- English
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