I got a question for you: A Pirali Brahmin from Calcutta with ancestral gentry roots in Jessore, Tagore wrote poetry as an eight-year-old. At the age of sixteen, he released his first substantial poems under the pseudonym Bhanusimha ("Sun Lion"), which were seized upon by literary authorities as long-lost classics. By 1877 he graduated to his first short stories and dramas, published under his real name. As a humanist, universalist internationalist, and ardent anti-nationalist, he denounced the British Raj and advocated independence from Britain. As an exponent of the Bengal Renaissance, he advanced a vast canon that comprised paintings, sketches and doodles, hundreds of texts, and some two thousand songs; his legacy also endures in the institution he founded, Visva-Bharati University.

Based on this passage, by which pseudonym rabindranath tagore first published his poems?
Let's think first:
The relevant sentence in the passage is: At the age of sixteen, he released his first substantial poems under the pseudonym Bhanusimha ("Sun Lion"), which were seized upon by literary authorities as long-lost classics.
Therefore, the answer is the pseudonym Bhanusimha ( '' Sun Lion '' ).