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Galaxy populations in the Antlia cluster – III. Properties of faint early-type galaxies

Authors

  • Analía V. Smith Castelli,

    Corresponding author
    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Sergio A. Cellone,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Favio R. Faifer,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Lilia P. Bassino,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Tom Richtler,

    1. Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
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  • Gisela A. Romero,

    1. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
    2. Departamento de Física y Astronomía, Universidad de Valparaíso, Avenida Gran Bretaña 1111, Valparaíso, Chile
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  • Juan Pablo Calderón,

    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Juan Pablo Caso

    1. Consejo Nacional de Investigaciones Científicas y Técnicas, Rivadavia 1917, C1033AAJ Buenos Aires, Argentina
    2. Instituto de Astrofísica de La Plata (CCT La Plata, CONICET, UNLP), Paseo del Bosque, B1900FWA La Plata, Argentina
    3. Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
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  • Based on observations carried out at the Cerro Tololo Inter-American Observatory (Chile), at Las Campanas Observatory (Chile) and at the European Southern Observatory, Paranal (Chile). Also based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ciencia e Tecnologia (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

E-mail: asmith@fcaglp.unlp.edu.ar

ABSTRACT

We present a new analysis of the early-type galaxy population in the central region of the Antlia cluster, focusing on the faint systems such as dwarf ellipticals (dEs) and dwarf spheroidals (dSphs). The colour–magnitude relation (CMR) and the relation between luminosity and mean effective surface brightness for galaxies in the central region of Antlia have been previously studied in Paper I of the present series. Now we confirm 22 early-type galaxies as Antlia members, using Gemini-GMOS and Magellan-MIKE spectra. Among them, 15 are dEs from the FS90 Antlia Group catalogue, two belong to the rare type of compact ellipticals (cEs) and five are new faint dwarfs that had never been catalogued before. In addition, we present 16 newly identified low-surface-brightness galaxy candidates, almost half of them displaying morphologies consistent with being Antlia’s counterparts of Local Group dSphs, which extend the faint luminosity limit of our study down to MB=−10.1(BT= 22.6) mag. With these new data, we built an improved CMR in the Washington photometric system, i.e. integrated T1 magnitudes versus (CT1) colours, which extends ∼4 mag faintwards the limit of spectroscopically confirmed Antlia members. When only confirmed early-type members are considered, this relation extends over 10 mag in luminosity with no apparent change in slope or increase in colour dispersion towards its faint end. The intrinsic colour scatter of the relation is compared with those reported for other clusters of galaxies; we argue that it is likely that the large scatter of the CMR, usually reported at faint magnitudes, is mostly due to photometric errors along with an improper membership/morphological classification. The distinct behaviour of the luminosity versus mean effective surface brightness relation at the bright and faint ends is analysed, while it is confirmed that dE galaxies on the same relation present a very similar effective radius, regardless of their colour. The projected spatial distribution of the member sample confirms the existence of two groups in Antlia, each one dominated by a giant elliptical galaxy and with one cE located close to each giant. Size and position, with respect to massive galaxies, of the dSph candidates are estimated and compared to Local Group counterparts.

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