GRAVITY+ Wide: Towards hundreds of z $\sim$ 2 AGN

TL;DR

The paper discusses upgrades to the GRAVITY+ instrument that significantly enhance its ability to observe hundreds of high-redshift AGN by expanding sky coverage and improving performance.

Contribution

It introduces instrumental upgrades enabling GRAVITY+ to observe a much larger sky area, allowing for the study of numerous AGN at redshift two and above.

Findings

Successful demonstration of increased sky coverage up to 30 arcsec.

Enhanced capability to observe broad line regions of high-redshift AGN.

Transformational improvements in instrument performance.

Abstract

As part of the GRAVITY$^{+}$ project, the near-infrared beam combiner GRAVITY and the VLTI are currently undergoing a series of significant upgrades to further improve the performance and sky coverage. The instrumental changes will be transformational, and for instance uniquely position GRAVITY to observe the broad line region of hundreds of Active Galactic Nuclei (AGN) at a redshift of two and higher. The increased sky coverage is achieved by enlarging the maximum angular separation between the celestial science object (SC) and the off-axis fringe tracking (FT) star from currently 2 arcseconds (arcsec) up to unprecedented 30 arcsec, limited by the atmospheric conditions. This was successfully demonstrated at the VLTI for the first time.