Spatially Resolved Star Formation History Along the Disk of M82 Using Multi-Band Photometric Data

TL;DR

This study maps the star formation history and extinction across M82's disk using multi-band photometry, revealing age gradients and the dominance of field stars over clusters in the galaxy's stellar populations.

Contribution

It provides spatially resolved star formation history and extinction data for M82's disk, utilizing synthetic spectral energy distribution fitting on multi-band data, which is a novel detailed analysis.

Findings

Outer disk stars are marginally older (~450 Myr) than inner disk stars (~100 Myr).

Most stellar mass formed in a starburst starting 450 Myr ago, lasting 350 Myr.

Field stars dominate the flux, with minimal contribution from stellar clusters.

Abstract

We present the results on the star formation history and extinction in the disk of M82 over spatial scales of 10" (~180 pc). Multi-band photometric data covering from the far ultraviolet to the near infrared bands were fitted to a grid of synthetic spectral energy distributions. We obtained distribution functions of age and extinction for each of the 117 apertures analyzed, taking into account observational errors through Monte-Carlo simulations. These distribution functions were fitted with gaussian functions to obtain the mean ages and extinctions along with errors on them. The analyzed zones include the high surface brightness complexes defined by O'Connell & Mangano (1978). We found that these complexes share the same star formation history and extinction as the field stellar populations in the disk. There is an indication that the stellar populations are marginally older at the outer disk (450 Myr at ~3 kpc) as compared to the inner disk (100 Myr at 0.5 kpc). For the nuclear regions (radius less than 500 pc), we obtained an age of less than 10 Myr. The results obtained in this work are consistent with the idea that the 0.5-3 kpc part of the disk of M82 formed around 90% of the stellar mass in a star-forming episode that started around 450 Myr ago lasting for about 350 Myr. We found that field stars are the major contributors to the flux over the spatial scales analyzed in this study, with stellar cluster contribution being 7% in the nucleus and 0.7% in the disk.