Deep spectroscopy of the emission-line populations in NGC 185†

  1. Denise R. Gonçalves1,2,*,
  2. Laura Magrini3,
  3. Lucimara P. Martins4,
  4. Ana M. Teodorescu5,
  5. Cintia Quireza1

Article first published online: 2 NOV 2011

DOI: 10.1111/j.1365-2966.2011.19749.x

Issue

Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society

Volume 419, Issue 1, pages 854–865, January 2012

Additional Information

How to Cite

Gonçalves, D. R., Magrini, L., Martins, L. P., Teodorescu, A. M. and Quireza, C. (2012), Deep spectroscopy of the emission-line populations in NGC 185. Monthly Notices of the Royal Astronomical Society, 419: 854–865. doi: 10.1111/j.1365-2966.2011.19749.x

Author Information

  1. 1

    UFRJ - Observatório do Valongo, Ladeira Pedro Antonio 43, 20080-090 Rio de Janeiro, Brazil

  2. 2

    Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT

  3. 3

    INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

  4. 4

    NAT - Universidade Cruzeiro do Sul, Rua Galvão Bueno 868, 01506-000 São Paulo, Brazil

  5. 5

    Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

* E-mail: denise@astro.ufrj.br

  1. †

    This work is 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 National Science Foundation on behalf of the Gemini partnership.

Publication History

  1. Issue published online: 13 DEC 2011
  2. Article first published online: 2 NOV 2011
  3. Accepted 2011 September 1. Received 2011 August 29; in original form 2011 July 1

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Keywords:

  • binaries: symbiotic;
  • planetary nebulae: general;
  • ISM: supernova remnants;
  • galaxies: abundances;
  • galaxies: individual: NGC 185;
  • Local Group

ABSTRACT

Because dwarf galaxies are the most abundant type of galaxy, they are crucial for our understanding of the formation and evolution of galaxies. Abundance ratios and their variations as a result of star formation are key constraints in chemical evolution models. Thus, the determination of these abundances in the dwarf galaxies of the Local Universe is extremely important. However, these objects are intrinsically faint, and observational constraints to their evolution can be obtained only for very nearby galaxies. NGC 185 is one of the four brightest dwarf companions of M31. However, unlike the other three – NGC 147, 205 and 221 (M32) – it has an important content of gas and dust. We have obtained deep spectroscopic observations of the Hα emitting population of NGC 185 using the Gemini multi-object spectrograph at the Gemini North telescope. As a result, in addition to the bright planetary nebulae (PNe) previously found in the galaxy and reported in the literature, we have found other, much fainter, PNe. We have then recalculated the electron temperatures and chemical abundances of the brightest PNe and, for the first time, we have derived their electron densities. Our characterization of the population properties of the PNe is interpreted in terms of the chemical evolution of NGC 185, which suggests that it has suffered a significant chemical enrichment within the last ∼8 Gyr. We have also discovered the first symbiotic star in the galaxy and we have determined the properties of a known supernova remnant located close to the centre of NGC 185.

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