Morphological Dependence of MIR Properties of SDSS Galaxies in the Spitzer SWIRE Survey

TL;DR

This study investigates how galaxy morphology influences mid-infrared properties, revealing significant correlations and proposing MIR dust-to-star ratios as a classification tool, with implications for understanding galaxy evolution.

Contribution

It provides a detailed analysis of MIR properties across different galaxy morphologies using SDSS and Spitzer data, introducing MIR dust-to-star ratios as an effective classification metric.

Findings

MIR dust-to-star ratios differ significantly between early and late-type galaxies.

A formula to estimate stellar mass from 3.6um luminosity is derived.

Edge-on and barred galaxies show similar MIR properties to other types.

Abstract

We explore the correlation between morphological types and mid-infrared (MIR) properties of an optically flux-limited sample of 154 galaxies from the Forth Data Release (DR4) of Sloan Digital Sky Survey (SDSS), cross-correlated with Spitzer SWIRE (Spitzer Wide-Area InfraRed Extragalactic Survey) fields of ELAIS-N1, ELAIS-N2 and Lockman Hole. Aperture photometry is performed on the SDSS and Spitzer images to obtain optical and MIR properties. The morphological classifications are given based on both visual inspection and bulge-disk decomposition on SDSS g- and r-band images. The average bulge-to-total ratio (B/T) is a smooth function over different morphological types. Both the 8um(dust) and 24um(dust) luminosities and their relative luminosity ratios to 3.6um (MIR dust-to-star ratios) present obvious correlations with both the Hubble T-type and B/T. The early-type galaxies notably differ from the late-types in the MIR properties, especially in the MIR dust-to-star ratios. It is suggested that the MIR dust-to-star ratio is an effective way to separate the early-type galaxies from the late-type ones. Based on the tight correlation between the stellar mass and the 3.6um luminosity, we have derived a formula to calculate the stellar mass from the latter. We have also investigated the MIR properties of both edge-on galaxies and barred galaxies in our sample. Since they present similar MIR properties to the other sample galaxies, they do not influence the MIR properties obtained for the entire sample.