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Published July 20, 2011 | Published
Journal Article Open

WISE Discovery of Low-metallicity Blue Compact Dwarf Galaxies


We report two new low-metallicity blue compact dwarf galaxies (BCDs), WISEP J080103.93+264053.9 (hereafter W0801+26) and WISEP J170233.53+180306.4 (hereafter W1702+18), discovered using the Wide-field Infrared Survey Explorer (WISE). We identified these two BCDs from their extremely red colors at mid-infrared wavelengths and obtained follow-up optical spectroscopy using the Low Resolution Imaging Spectrometer on Keck I. The mid-infrared properties of these two sources are similar to the well-studied, extremely low metallicity galaxy SBS 0335-052E. We determine metallicities of 12 + log (O/H) = 7.75 and 7.63 for W0801+26 and W1702+18, respectively, placing them among a very small group of very metal deficient galaxies (Z ≤ 1/10 Z_☉). Their >300 Å Hβ equivalent widths, similar to SBS 0335-052E, imply the existence of young (<5 Myr) star-forming regions. We measure star formation rates of 2.6 and 10.9 M_☉ yr^(–1) for W0801+26 and W1702+18, respectively. These BCDs, showing recent star formation activity in extremely low metallicity environments, provide new laboratories for studying star formation in extreme conditions and are low-redshift analogs of the first generation of galaxies to form in the universe. Using the all-sky WISE survey, we discuss a new method to identify similar star-forming, low-metallicity BCDs.

Additional Information

© 2011 American Astronomical Society. Received 2011 April 12; accepted 2011 June 15; published 2011 July 1. The authors thank the anonymous referee for timely and beneficial comments that have improved the manuscript. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory, California Institute of Technology, funded by the National Aeronautics and Space Administration. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors also recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community; we are most fortunate to have the opportunity to conduct observations from this mountain.

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Published - Griffith2011p15505Astrophys_J_Lett.pdf


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