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20 April 2024 |
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A Connection Between Apparent VLBA Jet Speeds and Initial AGN Detections Made by the Fermi Gamma-ray Observatory | | M. L. Lister
; D. C. Homan
; M. Kadler
; K. I. Kellermann
; Y. Y. Kovalev
; E. Ros
; T. Savolainen
; J. A. Zensus
; | | Date: |
12 Feb 2009 | | Abstract: | In its first three months of operations, the Fermi Gamma-ray Observatory has
detected approximately one quarter of the radio-flux limited MOJAVE sample of
bright flat-spectrum AGN at energies above 100 MeV. We have investigated the
apparent parsec-scale jet speeds of 26 MOJAVE AGN measured by the VLBA that are
in the LAT Bright AGN Sample (LBAS). We find that the gamma-ray bright quasars
have faster jets on average than the non-LBAS quasars, with a median of 15 c,
and values ranging up to 34 c. The LBAS AGN in which the LAT has detected
significant gamma-ray flux variability generally have faster jets than the
non-variable ones. These findings are in overall agreement with earlier results
based on non-uniform EGRET data which suggested that gamma-ray bright AGN have
preferentially higher Doppler boosting factors than other blazar jets. However,
the relatively low LAT detection rates for the full MOJAVE sample (24%) and
previously-known MOJAVE EGRET-detected blazars (43%) imply that Doppler
boosting is not the sole factor that determines whether a particular AGN is
bright at gamma-ray energies. The slower apparent jet speeds of LBAS BL Lac
objects and their higher overall LAT detection rate as compared to quasars
suggest that the former are being detected by Fermi because of their higher
intrinsic (unbeamed) gamma-ray to radio luminosity ratios. | | Source: | arXiv, 0902.2087 | | Services: | Forum | Review | PDF | Favorites | |
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