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On the Redshift of the Very High Energy Blazar 3C 66A

Furniss, A.; Fumagalli, M.; Danforth, C.; Williams, D.A.; Prochaska, J.X.

On the Redshift of the Very High Energy Blazar 3C 66A Thumbnail


Authors

A. Furniss

C. Danforth

D.A. Williams

J.X. Prochaska



Abstract

As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due to a lack of intrinsic emission and absorption features in optical spectra. We present new far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 3C 66A covering the wavelength range 1132-1800 Å. The data show a smooth continuum with intergalactic medium absorption features which can be used to place a firm lower limit on the blazar redshift of z ≥ 0.3347. An upper limit is set by statistically treating the non-detection of additional absorbers beyond z = 0.3347, indicating a redshift of less than 0.41 at 99% confidence and ruling out z ≥ 0.444 at 99.9% confidence. We conclude by showing how the redshift limits derived from the COS spectra remove the potential for this gamma-ray emitting blazar to place an upper limit on the flux of the EBL using high energy data from a flare in 2009 October.

Citation

Furniss, A., Fumagalli, M., Danforth, C., Williams, D., & Prochaska, J. (2013). On the Redshift of the Very High Energy Blazar 3C 66A. Astrophysical Journal, 766(1), Article 35. https://doi.org/10.1088/0004-637x/766/1/35

Journal Article Type Article
Publication Date Mar 20, 2013
Deposit Date Apr 6, 2014
Publicly Available Date Mar 29, 2024
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 766
Issue 1
Article Number 35
DOI https://doi.org/10.1088/0004-637x/766/1/35
Keywords BL Lacertae objects: individual (3C 66A), Diffuse radiation, Intergalactic medium, Ultraviolet: general.

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Copyright Statement
© 2013. The American Astronomical Society. All rights reserved.





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