A multi-wavelength study of nearby starburst galaxy M 82

TL;DR

This study combines multi-wavelength data to analyze star formation, metal enrichment, and outflows in the nearby starburst galaxy M 82, revealing heavily obscured star formation and supernova-driven chemical enrichment.

Contribution

It provides a spatially-resolved multi-wavelength analysis of M 82, highlighting the importance of combining UV, optical, IR, and X-ray data to understand starburst galaxy evolution.

Findings

Star formation rates vary significantly across wavelengths.

Heavy dust obscuration affects IR-based SFR estimates.

X-ray spectra show enhanced alpha-element abundances.

Abstract

We present a multi-wavelength study of the nearby starburst galaxy M 82 by combining high-resolution Far-ultraviolet (FUV) imaging from the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat and archival Chandra X-ray observations. Using FUV flux measurements, we estimate a spatially-resolved star formation rate (SFR) across several star-forming clumps within a radius of $\sim$3.6 kpc, finding a total SFR of 0.022 M$_{\odot}$ yr$^{-1}$. The H$_{\alpha}$ recombination line flux yields an SFR of $\sim$0.010 M$_{\odot}$ yr$^{-1}$, while the infrared-based SFR derived from 24 $\mu\mathrm{m}$ emission is significantly higher at 16 - 18 M$_{\odot}$ yr$^{-1}$, suggesting that a substantial fraction of star formation in M 82 is heavily dust-obscured. Morphological comparison of FUV, H$_{\alpha}$, mid-infrared, and soft X-ray emission reveals a strong spatial correlation, tracing multi-phase outflows along the galaxy's minor axis. X-ray spectral analysis using a three-temperature $\texttt{VAPEC}$ model shows enhanced abundances of Ne, Mg, Si, and S, consistent with enrichment from Type-II supernovae. These results demonstrate the importance of combining UV, optical, IR, and X-ray observations to probe both obscured and unobscured star formation, the metal enrichment, and the outflow-driven evolution of starburst galaxies.