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Bidirectional motion observed in the compact symmetric object 1946+708
G B Taylor1, R C Vermeulen, T J Pearson
1California Institute of Technology, Pasadena, CA 91125, USA.
Summary
Astronomers measured bidirectional motions in an extragalactic radio jet, revealing component velocities up to 1.09 times the speed of light. This study provides a new lower limit for the Hubble constant (H0).
Area of Science:
- Astronomy
- Astrophysics
- Cosmology
Background:
- Extragalactic radio jets are powerful outflows from active galactic nuclei.
- Compact Symmetric Objects (CSOs) are a class of radio sources with jets that are small and symmetric.
- Understanding jet dynamics is crucial for galaxy evolution and cosmology.
Purpose of the Study:
- To present the first direct measurements of bidirectional motions in an extragalactic radio jet.
- To determine the velocities of components within the radio jet of 1946+708.
- To derive a lower limit on the Hubble constant (H0) using these measurements.
Main Methods:
- Observations of the radio source 1946+708 were conducted two years apart.
- Velocities of four compact components in the jet were determined.
- Component pairing assumed simultaneous ejection in opposite directions to constrain H0.
Main Results:
- The radio source 1946+708, a CSO with S-symmetry, was identified with a galaxy at redshift z=0.101.
- The fastest component in the jet exhibited an apparent velocity of 1.09 h-1c.
- A lower limit of H0 > 42 km.s-1.Mpc-1 was derived.
Conclusions:
- Direct measurements of bidirectional jet motions are feasible and provide valuable data.
- The derived H0 lower limit contributes to ongoing cosmological parameter estimations.
- CSOs can serve as important probes for understanding extragalactic jets and the universe's expansion.