Near-infrared spectroscopy of stellar populations in nearby spiral galaxies

TL;DR

This study provides high-resolution near-infrared spectra of 29 nearby spiral galaxies, revealing that evolved red stars dominate their stellar populations, with minimal contribution from hot young stars, and offers new NIR spectral templates for galaxy analysis.

Contribution

First high spatial resolution NIR spectral templates for low-redshift spiral galaxies along the Hubble sequence are presented, aiding future galaxy population studies.

Findings

Evolved red stars dominate NIR spectra of spiral galaxies.

Hot young star contribution in NIR is virtually nonexistent.

Produced the first high-resolution NIR template spectra for spiral galaxies.

Abstract

We present high spatial resolution, medium spectral resolution near-infrared (NIR) H- and K-band long-slit spectroscopy for a sample of 29 nearby (z < 0.01) inactive spiral galaxies, to study the composition of their NIR stellar populations. These spectra contain a wealth of diagnostic stellar absorption lines, e.g. MgI 1.575 micron, SiI 1.588 micron, CO (6-3) 1.619 micron, MgI 1.711 micron, NaI 2.207 micron, CaI 2.263 micron and the 12CO and 13CO bandheads longward of 2.29 micron. We use NIR absorption features to study the stellar population and star formation properties of the spiral galaxies along the Hubble sequence, and we produce the first high spatial resolution NIR HK-band template spectra for low redshift spiral galaxies along the Hubble sequence. These templates will find applications in a variety of galaxy studies. The strength of the absorption lines depends on the luminosity and/or temperature of stars and, therefore, spectral indices can be used to trace the stellar population of galaxies. The entire sample testifies that the evolved red stars completely dominate the NIR spectra, and that the hot young star contribution is virtually nonexistent.