IC 10: More evidence that it is a blue compact dwarf

¹ Observatorio Astronómico Nacional, Instituto de Astronomía, UNAM, PO Box 439027, San Diego, CA 92143-9027, USA e-mail: richer@astrosen.unam.mx
² Instituto de Astrofísica de Canarias, Vía Láctea, 38200 La Laguna, Tenerife, Spain e-mail: almudena@astroscu.unam.mx
³ Instituto de Astronomía, UNAM, Apartado Postal 70-264, Ciudad Universitaria, 04510 México, D. F., México e-mail: georgiev@astroscu.unam.mx; margarit@astroscu.unam.mx
⁴ Institute of Astronomy, Bulgarian Academy of Sciences and Isaac Newton Institute of Chile, Bulgarian Branch, 72 Tsarigradsko chaussèe, 1784 Sofia, Bulgaria e-mail: jura@haemimont.bg
⁵ Dept. of Physics & Astronomy, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3 e-mail: mccall@aries.phys.yorku.ca; lee@aries.phys.yorku.ca; robin@aries.phys.yorku.ca
⁶ Department of Astronomy and Isaac Newton Institute of Chile, Bulgarian Branch, Sofia University, 1164 Sofia, Bulgaria e-mail: kurtev@phys.uni-sofia.bg

Corresponding author: M. G. Richer, richer@astrosen.unam.mx

Received: 22 August 2000
Accepted: 31 January 2001

Abstract

We present optical spectroscopy of Hii regions in the Local Group galaxy IC 10 and UBVR photometry of foreground stars in three fields towards this galaxy. From these data, we find that the foreground reddening due to the Milky Way is . We find that IC 10 contains considerable internal dust, which qualitatively explains the variety of reddening values found by studies of its different stellar populations. Based upon our foreground reddening, IC 10 has intrinsic photometric properties like those of a blue compact dwarf galaxy, and not those of a dwarf irregular. This result is consistent with much evidence that IC 10 is in the throes of a starburst that began at least ago. We also report the discovery of a new WR star in the Hii region HL111c.