TY - JOUR
T1 - Revealing High-z Fermi-LAT BL Lacs Using Swift and SARA Data with Photometric Analysis
AU - Sheng, Y.
AU - Rajagopal, M.
AU - Kaur, A.
AU - Ajello, M.
AU - Domínguez, A.
AU - Rau, A.
AU - Cenko, S. B.
AU - Greiner, J.
AU - Hartmann, D. H.
AU - Cox, I.
AU - Joffre, S.
AU - Karwin, C.
AU - McDaniel, A.
AU - Silver, R.
AU - Torres-Albà, N.
N1 - Publisher Copyright:
© 2024. The Author(s). Published by the American Astronomical Society.
PY - 2024/3/1
Y1 - 2024/3/1
N2 - BL Lacertae (BL Lac) objects are a subclass of blazar, distinguished by their featureless optical spectrum. The featureless spectrum presents a challenge in measuring the redshift of the BL Lacs. In this paper, we measure the redshift of BL Lacs using the photometric dropout technique. The space-based telescope Swift and the ground-based SARA telescopes are employed to provide magnitudes in the uvw 2 , uvm 2 , uvw 1 , u , b , v , g ′ , r ′ , i ′ , and z ′ filters. We observe 60 BL Lacs and report reliable redshift upper limits for 41 of them. We discover three new high-z BL Lacs (z > 1.3) at redshifts of 1.74 − 0.08 + 0.05 , 1.88 − 0.03 + 0.07 , and 2.10 − 0.04 + 0.03 , bringing the number of high-z BL Lacs found by this method up to 19. Discussions are made on the implications for the blazar sequence, the Fermi blazar divide, and the gamma-ray horizon based on an analysis of the 4LAC catalog and all high-z BL Lacs found with the photo-z technique.
AB - BL Lacertae (BL Lac) objects are a subclass of blazar, distinguished by their featureless optical spectrum. The featureless spectrum presents a challenge in measuring the redshift of the BL Lacs. In this paper, we measure the redshift of BL Lacs using the photometric dropout technique. The space-based telescope Swift and the ground-based SARA telescopes are employed to provide magnitudes in the uvw 2 , uvm 2 , uvw 1 , u , b , v , g ′ , r ′ , i ′ , and z ′ filters. We observe 60 BL Lacs and report reliable redshift upper limits for 41 of them. We discover three new high-z BL Lacs (z > 1.3) at redshifts of 1.74 − 0.08 + 0.05 , 1.88 − 0.03 + 0.07 , and 2.10 − 0.04 + 0.03 , bringing the number of high-z BL Lacs found by this method up to 19. Discussions are made on the implications for the blazar sequence, the Fermi blazar divide, and the gamma-ray horizon based on an analysis of the 4LAC catalog and all high-z BL Lacs found with the photo-z technique.
UR - https://www.scopus.com/pages/publications/85188000454
UR - https://www.scopus.com/inward/citedby.url?scp=85188000454&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ad21e7
DO - 10.3847/1538-4357/ad21e7
M3 - Article
AN - SCOPUS:85188000454
SN - 0004-637X
VL - 964
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 63
ER -