A STIS Atlas of CaII Triplet Absorption Line Kinematics in Galactic Nuclei

TL;DR

This paper presents an atlas of CaII triplet absorption line kinematics in galactic nuclei using STIS data, aiming to improve supermassive black hole mass measurements by identifying suitable spectra.

Contribution

It compiles and analyzes STIS archival data for galactic bulges to identify potential new black hole mass estimates and assesses data quality and limitations.

Findings

19 out of 42 galaxies may yield useful black hole mass estimates.

No correlation between signal-to-noise ratio and mass uncertainty.

Limited stellar template data available for accurate modeling.

Abstract

The relations observed between supermassive black holes and their host galaxies suggest a fundamental link in the processes that cause these two objects to evolve. A more comprehensive understanding of these relations could be gained by increasing the number of supermassive black hole mass (M) measurements. This can be achieved, in part, by continuing to model the stellar dynamics at the centers of galactic bulges using data of the highest possible spatial resolution. Consequently, we present here an atlas of galaxies in the Space Telescope Imaging Spectrograph (STIS) data archive that may have spectra suitable for new M estimates. Archived STIS G750M data for all non-barred galactic bulges are co-aligned and combined, where appropriate, and the radial signal-to-noise ratios calculated. The line-of-sight velocity distributions from the CaII triplet are then determined using a maximum penalized likelihood method. We find 19 out of 42 galaxies may provide useful new M estimates since they are found to have data that is comparable in quality with data that has been used in the past to estimate M. However, we find no relation between the signal-to-noise ratio in the previously analyzed spectra and the uncertainties of the black hole masses derived from the spectra. We also find that there is a very limited number of appropriately observed stellar templates in the archive from which to estimate the effects of template mismatching.