Census of H ii regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale

¹ Instituto de Astronomía, Universidad Nacional Autonóma de México, A.P. 70-264, 04510 México, D.F., Mexico
e-mail: sfsanchez@astro.unam.mx
² Millennium Institute of Astrophysics, Universidad de Chile, Casilla 36-D, Santiago, Chile
³ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
⁴ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, Aptdo. 3004, 18080 Granada, Spain
⁵ Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid, Spain
⁶ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
⁷ Depto. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
⁸ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis E. Erro 1, 72840 Tonantzintla, Puebla, Mexico
⁹ Dpto. de Física Teórica y del Cosmos, University of Granada, Facultad de Ciencias (Edificio Mecenas), 18071 Granada, Spain
¹⁰ CEI Campus Moncloa, UCM-UPM, Departamento de Astrofísica y CC. de la Atmósfera, Facultad de CC. Físicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain
¹¹ European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago, Chile

Received: 10 September 2014
Accepted: 18 November 2014

Abstract

We present a study of the H ii regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197 637 individual spectra, using integral field spectroscopy recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ~2 effective radii (r_e), sampling its morphological structures with unprecedented spatial resolution for a wide-field Integral Field Unit. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogues of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allows us to estimate the typical mixing scale length (r_mix ~ 0.4r_e), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms. We found evidence of an azimuthal variation in the oxygen abundance that may be connected with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.