Metallicity and Age of the Stellar Stream Around the Disk Galaxy NGC 5907

TL;DR

This study combines optical and infrared observations to analyze the stellar population of a galaxy's stream, estimating its metallicity and age to infer its formation history, favoring a minor merger scenario.

Contribution

It introduces a method using combined optical and infrared data to determine the metallicity and age of stellar streams, aiding in understanding their origins.

Findings

The stellar stream has a metallicity of approximately -0.3.

A minor merger with a stellar mass ratio of at least 1:8 best explains the stream's properties.

The combined SED fitting supports a minor merger formation model.

Abstract

Stellar streams have become central to studies of the interaction histories of nearby galaxies. To characterize the most prominent parts of the stellar stream around the well-known nearby (d = 17 Mpc) edge-on disk galaxy NGC 5907, we have obtained and analyzed new, deep gri Subaru/Suprime-Cam and 3.6 micron Spitzer/Infrared Array Camera (IRAC) observations. Combining the near-infrared 3.6 micron data with visible-light images allows us to use a long wavelength baseline to estimate the metallicity and age of the stellar population along a ~60 kpc long segment of the stream. We have fitted the stellar spectral energy distribution (SED) with a single-burst stellar population synthesis model and we use it to distinguish between the proposed satellite accretion and minor/major merger formation models of the stellar stream around this galaxy. We conclude that a massive minor merger (stellar mass ratio of at least 1:8) can best account for the metallicity of -0.3 inferred along the brightest parts of the stream.