The Pristine Inner Galaxy Survey (PIGS) VI: Different vertical distributions between two DIBs at 442.8 nm and 862.1 nm

TL;DR

This study analyzes the correlation and distribution differences of two diffuse interstellar bands at 442.8 nm and 862.1 nm across various Galactic latitudes, revealing they likely have different carriers and distribution patterns.

Contribution

It provides new insights into the distinct distributions of two DIBs over a large latitude range, suggesting different carriers and behaviors in the interstellar medium.

Findings

Tight linear correlations between DIBs and dust grains at low latitudes.

Different relative strengths of DIBs at high latitudes.

Evidence that the two DIBs have different carriers.

Abstract

Although diffuse interstellar bands (DIBs) were discovered over 100 years ago, for most of them, their origins are still unknown. Investigation on the correlations between different DIBs is an important way to study the behavior and distributions of their carriers. Based on stacking thousands of spectra from the Pristine Inner Galaxy Survey, we study the correlations between two DIBs at 442.8 nm ($\lambda$442.8) and 862.1 nm ($\lambda$862.1), as well as the dust grains, in a range of latitude spanning ${\sim}22^{\circ}$ ($4^{\circ}\,{<}\,|b|\,{<}\,15^{\circ}$) toward the Galactic center ($|\ell|\,{<}\,11^{\circ}$). Tight linear intensity correlations can be found between $\lambda$442.8, $\lambda$862.1, and dust grains for $|b|\,{<}\,12^{\circ}$ or $E(B-V)\,{>}\,0.3$ mag. For $|b|\,{>}\,12^{\circ}$, $\lambda$442.8 and $\lambda$862.1 present larger relative strength with respect to the dust grains. A systematic variation of the relative strength between $\lambda$442.8 and $\lambda$862.1 with $|b|$ and $E(B-V)$ concludes that the two DIBs do not share a common carrier. Furthermore, the carrier of $\lambda$862.1 is more abundant at high latitudes than that of $\lambda$442.8. This work can be treated as an example showing the significance and potentials to the DIB research covering a large latitude range.