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Published August 2014 | Submitted + Published
Journal Article Open

Discovering extremely compact and metal-poor, star-forming dwarf galaxies out to z ∼ 0.9 in the VIMOS Ultra-Deep Survey


We report the discovery of 31 low-luminosity (−14.5 ≳ M_(AB)(B) ≳ −18.8), extreme emission line galaxies (EELGs) at 0.2 ≲ z ≲ 0.9 identified by their unusually high rest-frame equivalent widths (100 ≤ EW[O iii] ≤ 1700 Å) as part of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented sensitivity (I_(AB) ~ 25 mag) along with multiwavelength photometry and HST imaging are used to investigate spectrophotometric properties of this unique sample and to explore, for the first time, the very low stellar mass end (M* ≲ 10^8M_⊙) of the luminosity-metallicity (LZR) and mass-metallicity (MZR) relations at z < 1. Characterized by their extreme compactness (R_50 < 1 kpc), low stellar mass and enhanced specific star formation rates (sSFR = SFR/M_* ~ 10^(-9)−10^(-7) yr^(-1)), the VUDS EELGs are blue dwarf galaxies likely experiencing the first stages of a vigorous galaxy-wide starburst. Using T_e-sensitive direct and strong-line methods, we find that VUDS EELGs are low-metallicity (7.5 ≲ 12 + log  (O/H) ≲ 8.3) galaxies with high ionization conditions (log (q_(ion)) ≳ 8 cm s^(-1)), including at least three EELGs showing Heiiλ 4686 Å emission and four extremely metal-poor (≲10% solar) galaxies. The LZR and MZR followed by VUDS EELGs show relatively large scatter, being broadly consistent with the extrapolation toward low luminosity and mass from previous studies at similar redshift. However, we find evidence that galaxies with younger and more vigorous star formation – as characterized by their larger EWs, ionization and sSFR – tend to be more metal poor at a given stellar mass.

Additional Information

© 2014 ESO. Received 15 March 2014. Accepted 2 July 2014. Published online 19 August 2014. We thank the anonymous referee for helpful comments that helped to improve this manuscript. We thank the ESO staff for their continuous support for the VUDS survey, particularly the Paranal staff conducting the observations and Marina Rejkuba and the ESO user support group in Garching. This work is supported by funding from the European Research Council Advanced Grant ERC-2010-AdG-268107-EARLY and by INAF Grants PRIN 2010, PRIN 2012 and PICS 2013. RA and AF acknowledge the FP7 SPACE project ASTRODEEP (Ref. No: 312725), supported by the European Commission. A.C., O.C., M.T. and V.S. acknowledge the grant MIUR PRIN 2010–2011. D.M. gratefully acknowledges LAM hospitality during the initial phases of the project. This work is based on data products made available at the CESAM data center, Laboratoire d'Astrophysique de Marseille. This work partly uses observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

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Published - aa23816-14.pdf

Submitted - 1403.3692v1.pdf


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