HST FUV Spectroscopy of Super Star Cluster A in the Green Pea Analog Mrk 71: Revealing the Presence of Very Massive Stars

Understand

Mrk 71 is a low metallicity (Z = 0.16 Z_sun) starburst region in the local dwarf galaxy NGC 2366, hosting two super star clusters (SSCs A and B), and is recognized as a Green Pea (GP) analog with SSC A responsible for the GP properties.

• We present STIS and FOS far-ultraviolet (FUV) spectra of the embedded SSC Mrk 71-A obtained with the Hubble Space Telescope (HST).
• The STIS FUV spectrum shows the characteristic features of very massive stars (VMS, masses > 100 M_sun) and we derive an age of 1+/-1 Myr by comparison with the Charlot & Bruzual suite of spectral population synthesis models with upper mass limits of 300 and 600 M_sun.
• We compare the STIS spectrum with all known SSC spectra exhibiting VMS signatures: NGC 5253-5, R136a, NGC 3125-A1 and the z = 2.37 Sunburst cluster.