Velocity Dispersion $\sigma_{\rm aper}$ Aperture Corrections as a Function of Galaxy Properties from Integral-field Stellar Kinematics of 10,000 MaNGA Galaxies

TL;DR

This study derives an empirical formula for correcting stellar velocity dispersion measurements from fixed aperture observations, accounting for galaxy properties, based on analysis of 10,000 MaNGA galaxies.

Contribution

It introduces a new aperture correction formula for stellar velocity dispersion that depends on galaxy luminosity, color, and Sersic index, improving upon previous models.

Findings

A strong dependence of correction factor on galaxy brightness, color, and structure.

Previous literature corrections are not applicable to galaxies with intermediate Sersic indices.

A lookup table and Python tool are provided for practical application.

Abstract

The second moment of the stellar velocity within the effective radius, denoted by $\sigma_{\rm e}^2$, is a crucial quantity in galaxy studies as it provides insight into galaxy properties and their mass distributions. However, large spectroscopic surveys typically do not measure $\sigma_{\rm e}$ directly, instead providing $\sigma_{\rm aper}$, the second moment of the stellar velocity within a fixed fiber aperture. In this paper, we derive an empirical aperture correction formula, given by $\sigma_{\rm aper}/\sigma_{\rm e}=(R_{\rm aper}/R_{\rm e})^{\alpha}$, using spatially resolved stellar kinematics extracted from approximately 10,000 Sloan Digital Sky Survey-Mapping Nearby Galaxies at Apache Point Observatory (SDSS-MaNGA) integral field unit observations. Our analysis reveals a strong dependence of $\alpha$ on the $r$-band absolute magnitude $M_{\rm r}$, $g-i$ color, and Sersic index $n_{\rm Ser}$, where $\alpha$ values are lower for brighter, redder galaxies with higher Sersic indices. Our results demonstrate that the aperture correction derived from previous literature on early-type galaxies cannot be applied to predict the aperture corrections for galaxies with intermediate Sersic indices. We provide a lookup table of $\alpha$ values for different galaxy types, with parameters in the ranges of $-18>M_{\rm r}>-24$, $0.4<g-i<1.6$, and $0<n_{\rm Ser}<8$. A Python script is provided to obtain the correction factors from the lookup table.