A census of Ha emitters in the intergalactic medium of the NGC 2865 system

Autor(es)

Urrutia-Viscarra, F. ^{[1, 2]} ; Arnaboldi, M. ^[1] ; Mendes de Oliveira, C. ^[2] ; Gerhard, O. ^[3] ; Torres-Flores, S. ^[4] ; Carrasco, E. R. ^[5] ; de Mello, D. ^{[6, 7]}

Afiliação do(s) autor(es)

^[1] European So Observ, D-85748 Garching - Germany

^[2] Univ Sao Paulo, Inst Astron Geofins Ciencias & Atmosfer, BR-05508900 Sao Paulo - Brazil

^[3] Max Planck Inst Extraterr Phys, D-85741 Garching - Germany

^[4] Univ La Serena, Dept Fis, La Serena - Chile

^[5] Gemini Observ AURA, Southern Operat Ctr, La Serena - Chile

^[6] Catholic Univ Amer, Dept Phys, Washington, DC 20064 - USA

^[7] NASA, Goddard Space Flight Ctr, Observat Cosmol Lab, Greenbelt, MD 20771 - USA

• Tipo de documento: Artigo Científico
• Fonte: Astronomy & Astrophysics; v. 569, SEP 2014.
• Citações Web of Science: 2

Resumo

Tidal debris, which are rich in HI gas and formed in interacting and merging systems, are suitable laboratories to study star formation outside galaxies. Recently, several such systems were observed, which contained many young star forming regions outside the galaxies. In previous works, we have studied young star forming regions outside galaxies in different systems with optical and/or gaseous tidal debris, in order to understand how often they occur and in which type of environments. In this paper, we searched for star forming regions around the galaxy NGC 2865, a shell galaxy that is circled by a ring of HI with a total mass of 1.2x10(9) M-circle dot. Using the multi-slit imaging spectroscopy technique with the Gemini telescope, we detected all H alpha emitting sources in the surroundings of the galaxy NGC 2865, down to a flux limit of 10(-18) erg cm(-2) s(-1) angstrom(-1). With the spectra information and the near and far-ultraviolet flux, we characterize the star formation rates, masses, ages, and metallicities for these HII regions. In total, we found 26 emission-line sources in a 60 x 60 Kpc field centered over the southeastern tail of the HI gas present around the galaxy NGC 2865. Out of the 26 Ha emitters, 19 are in the satellite galaxy FGCE 0745, and seven are intergalactic HII regions scattered over the south tail of the HI gas around NGC 2865. We found that the intergalactic HII regions are young (<200 Myr) with stellar masses in the range 4 x 10(3) M-circle dot to 17 x 10(6) M-circle dot. These are found in a region of low HI gas density, where the probability of forming stars is expected to be low. For one of the intergalactic HII regions, we estimated a solar oxygen abundance of 12 + log(O/H) similar to 8.7. We also were able to estimate the metallicity for the satellite galaxy FGCE 0745 to be 12 + log(O/H) similar to 8.0. Given these physical parameters, the intergalactic HII regions are consistent with young star forming regions (or clusters), which are born in situ outside the NGC 2865 galaxy from a pre-enriched gas removed from the host galaxies in a merger event. The relevance of these observations is discussed. (AU)

• Processo FAPESP: 06/56213-9 - Nova física no espaço: formação e evolução de estruturas no universo
• Beneficiário: Claudia Lucia Mendes de Oliveira
• Modalidade de apoio: Auxílio à Pesquisa - Temático