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Determination of K4000 of potential blazar candidates among EGRET unidentified gamma-ray sources

Published online by Cambridge University Press:  29 January 2021

Emmanuel Uwitonze ,
Pheneas Nkundabakura  and
Tom Mutabazi
Emmanuel Uwitonze
Affiliation:
Physics Department, Mbarara University of Science and Technology, P.O. Box 1410, Mbarara, Uganda email: uwitonze_emmanuel@yahoo.com
Pheneas Nkundabakura
Affiliation:
Department of Mathematics, Sciences and Physical Education, University of Rwanda-College of Education, P.O. Box 5039, Kigali, Rwanda
Tom Mutabazi
Affiliation:
Physics Department, Mbarara University of Science and Technology, P.O. Box 1410, Mbarara, Uganda email: uwitonze_emmanuel@yahoo.com
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Abstract

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Blazars are radio-loud Active Galactic Nuclei (AGN) with relativistic jets oriented towards the observer’s line-of-sight. Based on their optical spectra, blazars may be classified as flat-spectrum radio quasars (FSRQs) or BL Lacs. FSRQs are more luminous blazars with both narrow and broad emission and absorption lines, while BL Lacs are less luminous and featureless. Recent studies show that blazars dominate (˜93%) the already-identified EGRET sources (142), suggesting that among the unidentified sources (129) there could still be faint blazars. Due to the presence of a strong non-thermal component inside their jets, blazars are found to display a weaker depression at ˜4000 Å (K 4000 ≤ 0.4). In this study, we aimed at determining the K 4000 break for a selected sample among the potential blazar candidates from unidentified EGRET sources to confirm their blazar nature. We used two blazar candidates, 3EG J1800-0146 and 3EG J1709-0817 associated with radio counterparts, J1802-0207 and J1713-0817, respectively. Their optical counterparts were obtained through spectroscopic observations using Robert Stobie spectrograph (RSS) at the Southern African Large Telescope (SALT) in South Africa. The observed Ca II H & K lines depression at ˜4000 Å in spectra of these sources show a shallow depression, K 4000 = 0.35 ± 0.02 and 0.24 ± 0.01, respectively, suggesting that these sources are blazar candidates. Moreover, the redshifts z = 0.165 and 0.26 measured in their spectra confirm the extragalactic nature of these sources.

Keywords

line: identificationradiation mechanisms: non-thermaltechniques: spectroscopicgalaxies: activegalaxies: jetsgalaxies: BL Lacertae objects
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 15 , Symposium S356: Nuclear Activity in Galaxies Across Cosmic Time , October 2019 , pp. 355 - 357
Copyright
© The Author(s), 2021. Published by Cambridge University Press on behalf of International Astronomical Union

References

Caccianiga, A., Maccacaro, T., Wolter, et al., 1999, ApJ, 513, 51 10.1086/306822CrossRefGoogle Scholar
Hartman, C., Bertsch, L., Bloom, et al., 1999, ApJS, 123, 79 10.1086/313231CrossRefGoogle Scholar
Landt, H., Padovani, P., Giommi, et al., 2002, MNRAS, 336, 945 10.1046/j.1365-8711.2002.05832.xCrossRefGoogle Scholar
Marcha, M., Browne, A., Impey, et al., 1996, MNRAS, 281, 425 10.1093/mnras/281.2.425CrossRefGoogle Scholar
Nkundabakura &, P., Meintjes., 2012, MNRAS, 427, 859 10.1111/j.1365-2966.2012.21953.xCrossRefGoogle Scholar
Sowards-Emmerd, D., Romani, R. W., Michelson, et al., 2003, ApJ, 590, 109 10.1086/374981CrossRefGoogle Scholar