Herschel Observations of Major Merger Pairs at z=0: Dust Mass and Star Formation

TL;DR

This study uses Herschel FIR and sub-mm data to analyze dust mass and star formation in 88 major-merger galaxy pairs at z=0, revealing interaction-dependent star formation enhancements and the role of disc collisions.

Contribution

It provides the first large sample analysis of dust and star formation in galaxy mergers, highlighting the impact of pair type on star formation efficiency and gas content.

Findings

SFGs in S+S pairs show increased sSFR and SFE.

SFGs in S+E pairs do not show significant sSFR enhancement.

Paired galaxies without interaction signs have similar sSFR and SFE.

Abstract

We present Herschel PACS $\&$ SPIRE far-infrared (FIR) and sub-mm imaging observations for a large K-band selected sample of 88 close major-merger pairs of galaxies (H-KPAIRs) in 6 photometric bands (70, 100, 160, 250, 350, and 500 $\mu m$). Among 132 spiral galaxies in the 44 spiral-spiral (S$+$S) pairs and 44 spiral-elliptical (S$+$E) pairs, 113 are detected in at least one Herschel band. Star formation rate (SFR) and dust mass ($M_{\rm dust}$) are derived from the IR SED fitting. Mass of total gas ($M_{\rm gas}$) is estimated by assuming a constant dust-to-gas mass ratio of 0.01. Star forming spiral galaxies (SFGs) in S$+$S pairs show significant enhancements in both specific star formation rate (sSFR) and star formation efficiency (SFE), while having nearly the same gas mass, compared to control galaxies. On the other hand, for SFGs in S$+$E pairs, there is no significant sSFR enhancement and the mean SFE enhancement is significantly lower than that of SFGs in S$+$S pairs. This suggests an important role for the disc-disc collision in the interaction induced star formation. The $M_{\rm gas}$ of SFGs in S$+$E pairs is marginally lower than that of their counterparts in both S$+$S pairs and the control sample. Paired galaxies with and without interaction signs do not differ significantly in their mean sSFR and SFE. As found in previous works, this much larger sample confirms the primary and secondary spirals in S+S pairs follow a Holmberg effect correlation on sSFR.