New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates

TL;DR

This study identifies and spectroscopically confirms 37 new quasars behind the Magellanic Clouds using near-infrared selection, enhancing the reference system for astrometric studies and providing a basis for future surveys.

Contribution

It presents the first spectroscopic confirmation of near-infrared selected quasar candidates behind the Magellanic Clouds, expanding the known quasar sample in this region.

Findings

Confirmed 37 quasars, 34 of which are new identifications.

Quasars span redshifts from approximately 0.5 to 4.1.

Expected to find about 1500 quasars upon survey completion.

Abstract

Quasi--stellar objects (quasars) located behind nearby galaxies provide an excellent absolute reference system for astrometric studies, but they are difficult to identify because of fore- and background contamination. Deep wide--field, high angular resolution surveys spanning the entire area of nearby galaxies are needed to obtain a complete census of such quasars. We embarked on a program to expand the quasar reference system behind the Large and the Small Magellanic Clouds, the Magellanic Bridge, and the Magellanic Stream, connecting the Clouds with the Milky Way. Hundreds of quasar candidates were selected based on their near--infrared colors and variability properties from the ongoing public ESO VISTA Magellanic Clouds survey. A subset of 49 objects was followed up with optical spectroscopy. We confirmed the quasar nature of 37 objects (34 new identifications), four are low redshift objects, three are probably stars, and the remaining three lack prominent spectral features for a secure classification; bona fide quasars, judging from their broad absorption lines are located, as follows: 10 behind the LMC, 13 behind the SMC, and 14 behind the Bridge. The quasars span a redshift range from z~0.5 to z~4.1. Upon completion the VMC survey is expected to yield a total of ~1500 quasars with Y<19.32 mag, J<19.09 mag, and Ks<18.04 mag.