The stellar spectral features of nearby galaxies in the near infrared: tracers of thermally pulsing asymptotic giant branch stars?
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Riffel, Rogerio
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The stellar spectral features of nearby galaxies in the near infrared: tracers of thermally pulsing asymptotic giant branch stars?
Author
- Riffel, Rogerio;
- Mason, Rachel;
- Martins, Lucimara;
- Rodríguez Ardila, Alberto;
- Ho, Luis C.;
- Riffel, Rogemar A.;
- Lira Teillery, Paulina;
- González Martín, Omaira;
- Ruschel Dutra, Daniel;
- Alonso Herrero, Almudena;
- Helene, Flohic;
- McDermid, Richard;
- Ramos Almeida, Cristina;
- Thanjavur, Karun;
- Winge, Claudia;
Abstract
We analyse the stellar absorption features in high signal-to-noise ratio (S/N) near-infrared
(NIR) spectra of the nuclear region of 12 nearby galaxies, mostly spirals. The features detected
in some or all of the galaxies in this sample are the TiO (0.843 and 0.886 µm), VO (1.048 µm),
CN (1.1 and 1.4 µm), H2O (1.4 and 1.9 µm) and CO (1.6 and 2.3 µm) bands. The C2 (1.17
and 1.76 µm) bands are generally weak or absent, although C2 (1.76 µm) may be weakly
present in the mean galaxy spectrum. A deep feature near 0.93 µm, likely caused by CN,
TiO and/or ZrO, is also detected in all objects. Fitting a combination of stellar spectra to the
mean spectrum shows that the absorption features are produced by evolved stars: cool giants
and supergiant stars in the early- or thermally pulsing asymptotic giant branch (E-AGB or
TP-AGB) phases. The high luminosity of TP-AGB stars, and the appearance of VO and ZrO
features in the data, suggest that TP-AGB stars dominate these spectral features. However, a
contribution from other evolved stars is also likely. Comparison with evolutionary population
synthesis models shows that models based on empirical libraries that predict relatively strong
NIR features provide a more accurate description of the data. However, none of the models
tested accurately reproduces all of the features observed in the spectra. To do so, the models
will need to not only improve the treatment of TP-AGB stars, but also include good quality
spectra of red giant and E-AGB stars. The uninterrupted wavelength coverage, high S/N and
quantity of features we present here will provide a benchmark for the next generation of
models aiming to explain and predict the NIR properties of galaxies.
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Artículo de publicación ISI
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MNRAS 450, 3069–3079 (2015)
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