A southern hemisphere survey of the 5780 and 6284 {\AA} diffuse interstellar bands: correlation with the extinction

TL;DR

This study provides a new database of diffuse interstellar band measurements in the southern hemisphere, examining their correlation with extinction and revealing the influence of stellar temperature on DIB strength.

Contribution

It presents the first comprehensive southern hemisphere DIB survey and compares its findings with northern data, highlighting the impact of stellar temperature on DIB-extinction correlation.

Findings

DIBs show a linear relationship with reddening similar to northern hemisphere results.

Lower stellar temperatures lead to a higher correlation between DIBs and extinction.

Radiation field effects significantly influence DIB strength and outlier prevalence.

Abstract

We present a new database of 5780.5 and 6283.8 {\AA} DIB measurements and also study their correlation with the reddening. The database is based on high-resolution, high-quality spectra of early-type nearby stars located in the southern hemisphere at an average distance of 300 pc. Equivalent widths of the two DIBs were determined by means of a realistic continuum fitting and synthetic atmospheric transmissions. For all stars that possess a precise measurement of their color excess, we compare the DIBs and the extinction. We find average linear relationships of the DIBS and the color excess that agree well with those of a previous survey of northern hemisphere stars closer than 550 pc. This similarity shows that there is no significant spatial dependence of the average relationship in the solar neighborhood within $\simeq$ 600 pc. A noticeably different result is our higher degree of correlation of the two DIBs with the extinction. We demonstrate that it is simply due to the lower temperature and intrinsic luminosity of our targets. Using cooler target stars reduces the number of outliers, especially for nearby stars, confirming that the radiation field of UV bright stars has a significant influence on the DIB strength. We have used the cleanest data to compute updated DIB shapes.