Abstrakti
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 active galactic nuclei (AGNs) at energies
above 100 MeV. We have investigated the apparent parsec-scale jet speeds
of 26 MOJAVE AGNs measured by the Very Long Baseline Array (VLBA) that
are in the LAT bright AGN sample (LBAS). We find that the γ-ray
bright quasars have faster jets on average than the non-LBAS quasars,
with a median of 15c, and values ranging up to 34c. The LBAS AGNs in
which the LAT has detected significant γ-ray flux variability
generally have faster jets than the nonvariable ones. These findings are
in overall agreement with earlier results based on nonuniform EGRET data
which suggested that γ-ray bright AGNs 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 γ-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) γ-ray to radio luminosity
ratios.
Alkuperäiskieli | Englanti |
---|---|
Sivut | L22-L26 |
Julkaisu | Astrophysical Journal Letters |
Vuosikerta | 696 |
Numero | 1 |
DOI - pysyväislinkit | |
Tila | Julkaistu - 2009 |
OKM-julkaisutyyppi | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä |