Ativhakas are mentioned in Adhyaya 4 -Pada 3 of Vedanta-Sutras.
अतिवहिकास्तल्लिंगात् || BS 4.3.4||
( These are ) deities conducting the soul ( on the path of gods) , on
the account of indicatory marks to the effect. This sutra gives us
hints about who are they its said that these ativahakas are are more
or less human. - Hindi And here is English -Page
The next sutra gives the clear idea about who these Ativakas are. Its said that it is the job of respective gods of various lokas to carry forward the soul upto Brahmaloka. And thus the deties are to be considered as the Ativahakas. And the differnt lokas through which the soul takes the journey according to vedanta sutras are Archi (fire , flame) , Sunrays , Suryaloka , Chandra loka , Vidyut loka , Agni loka , Vayu loka ,Varun loka , Indra loka , Prajapati loka.
(That deities ment in those texts) is established , because both
(i.e. traveller and the pah ) are benumbered (i.e. unconscious)
So the respective central deities of these lokas are the Ativahakas of the soul from earth to either Pitru loka , Swarga loka or beyond that in Brahma loka. And they are Agni , Surya , Chandra, Vidyut , Vayu , Varuna , Indra ,Prajapati.
Brahma Sutras Adhaya 3 -Pada 1 -Sutra 22 gives us the idea about the return journey of the soul from either Pitruloka or Swarga loka. Its said that the soul takes exactly same path in his return journey as he takes up while asendeing to these lokas.
तत्साभाव्यापत्तिः, उपपत्तेः ॥ २२ ॥
tatsābhāvyāpattiḥ, upapatteḥ || BS 3.1 22 ||
(The soul when decending from chandra loka ) attains silmilarity of
nature with them (i.e with ether ,air etc).
Explanation - its said in Brahma Sutras that after the death the soul departs from from this world either from Dhuma Marga or Archiradi Marga i.e. path of sun or path of prities ( Dev yana , Pitru yana) during which he has to go through various lokas in order to reach either Pitru loka or Dev loka aor finally to Brahma loka. But during this course he has to go through different lokas like Agni loka , vayu loka etc. which are in its path of journey. So the central deities of the respected lokas carry the soul to the next loka OR gives him the way. And just because these deities carry the soul forward to next loka and they are both similar to humans in nature as well as super human they are called as " Ativahakas" or Superconductors. Brahma sutras tells us that its the job of the respective deities of lokas in between to carry the soul to next loka. So the names of Ativahakas are confirmed from Brahma Sutras.