Redshift determination of BL Lac objects as from detection of their host groups

TORRES ZAFRA, J.; BUZZONI, A.; CELLONE, S. A.,; ANDRUCHOW, I.; PORTILLA BARBOSA, J. G.

Cartagena de Indias

Congreso; XV Latin American Regional IAU Meeting (LARIM); 2016

IAU

BL Lac objects are a subclass of blazars showing strong, non-thermal variable emission from radio to TeV energies. Their properties are usually attributed to beamed emission from a relativistic jet which is close to the line of sight. The lack of emission and/or absorption features in the optical spectra of these objects, makes the accurate determination of their redshifts very uncertain or even impossible.Since these sources are typically hosted by elliptical galaxies that are associated with groups or poor clusters, the detection of one of these structures in their close environment, serves as an estimator of their possible redshift. For this reason we perform a spectrophotometric study of the close environments of a sample of three BL Lac objects with unknown redshift: 3C 66A, PG 1553+113 and PKS 0332-403.