The Initial Mass Function of Low-mass Stars and Brown Dwarfs in the W3 Complex

TL;DR

This study uses Hubble Space Telescope infrared data to analyze the initial mass function of low-mass stars and brown dwarfs in the W3 star-forming region, finding it similar to smaller, nearby regions and suggesting a universal IMF.

Contribution

First detailed IMF measurement of low-mass stars and brown dwarfs in the distant W3 region using HST infrared imaging.

Findings

IMF in W3 resembles that of nearby star-forming regions

No significant variation in low-mass IMF across different star-forming environments

Supports universality of the initial mass function

Abstract

We have used archival infrared images obtained with the Wide Field Camera 3 on board the Hubble Space Telescope to constrain the initial mass function of low-mass stars and brown dwarfs in the W3 star-forming region. The images cover 438 arcmin$^2$, which encompasses the entire complex, and were taken in the filters F110W, F139M, and F160W. We have estimated extinctions for individual sources in these data from their colors and have dereddened their photometry accordingly. By comparing an area of the images that contains the richest concentration of previously identified W3 members to an area that has few members and is dominated by background stars, we have estimated the luminosity function for members of W3 with masses of 0.03-0.4 $M_\odot$. That luminosity function closely resembles data in typical nearby star-forming regions that have much smaller stellar populations than W3 ($\lesssim$500 vs. several thousand objects). Thus, we do not find evidence of significant variations in the initial mass function of low-mass stars and brown dwarfs with star forming conditions, which is consistent with recent studies of other distant massive star-forming regions.