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Spiral-like star-forming patterns in CALIFA early-type galaxies

J. M. Gomes, P. Papaderos, J. M. Vílchez, C. Kehrig, J. Iglesias-Páramo, I. P. Breda, M. D. Lehnert, S. F. Sánchez, B. Ziegler, S. N. Reis, J. Bland-Hawthorn, L. Galbany, D. J. Bomans, F. F. Rosales-Ortega, C. J. Walcher, R. García-Benito, I. Márquez, G. J. Olmo, M. Mollá, R. A. Marino, C. Catalán-Torrecilla, R. M. González Delgado, Á. R. López-Sánchez, and the CALIFA collaboration

Abstract

Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 <μr mag/□″< 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(Hα) ≃ 1 Å) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3 Å <EW(Hα)≲ 20 Å) Hii-region characteristics. This spatial segregation of nebular emission in two physically distinct concentric zones calls for an examination of aperture effects in studies of type i+ ETGs with single-fiber spectroscopic data.

Keywords
galaxies: elliptical and lenticular, cD, galaxies: nuclei, galaxies: ISM, galaxies: kinematics and dynamics, galaxies: star formation

Notes
Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie (MPIA) and the Instituto de Astrofísica de Andalucía (CSIC).

Astronomy and Astrophysics
Volume 585, Article Number A92, Number of pages 6
2016 January

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia