Photometric studies of composite stellar systems. V - Infrared photometry of star clusters in the Magellanic clouds

Persson, S. E.; Aaronson, M.; Cohen, Judith G.; Frogel, J. A.; Matthews, K.

doi:10.1086/160763

Cited by 140 publications

(210 citation statements)

References 5 publications

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“…The predicted contributions of C-stars to the near-IR light of intermediate age populations are consistent with those observed in the Magellanic Clouds (e.g. [18]). One of us (M.M.)…”

Section: Model Construction and Predictionssupporting

confidence: 85%

Post-Starburst Populations Near and Far — The Potential of Near-IR Spectroscopy

Lançon

Mouhcine

2001

Starburst Galaxies: Near and Far

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Abstract. The efficient use of near-IR data in studies of external stellar populations depends on our ability to recognize the nature of the predominant sources of light, and to interprete these findings in terms of age and metallicity. Here we focus on elderly post-starburst populations, with ages of 10 8 − 10 9 yrs. New models confirm that they are indeed expected to display specific spectral signatures in the near-IR, due to variable M stars of the asymptotic giant branch and to carbon stars. The signatures depend on age and metallicity. We summarize the status of current quantitative predictions and emphasize the importance of an empirical calibration of the spectral synthesis models. OverviewNear-IR data has been used very often to confirm the presence of an "evolved stellar component" in starburst galaxies. The need to study stellar populations deeply embedded in dust is also frequently invoked to justify near-IR observations. But what exactly are these cool stellar populations seen between 1 and 3 µm? Population synthesis models tell us that red supergiants are the main sources 10 7 − 10 8 yrs after a star formation episode; during the following 10 9 yrs, stars of the upper, thermally pulsing asymptotic giant branch (TP-AGB) become predominant; and finally giants of the early AGB (E-AGB) and of the first red giant branch (RGB) outweigh other populations. The efficient use of near-IR data depends on our ability to distinguish these categories from each other and to interprete them in terms of age and metallicity.Very strong CO absorption (2.3 µm) is a clear signature of a red supergiant population ([1] initiated the systematic exploration of CO in cool stars; [19] analysed early observations in starbursts; [9] discussed the diagnostic power of the feature and its limitations). But the dependence of the red supergiant population on metallicity is strong [14] and not reproduced by stellar evolution models unless ad hoc corrections are invoked ([12], [17]). Therefore the threshold above which the CO absorption becomes an unambiguous signature of a supergiant population is uncertain. On the other hand, it has recently been claimed that high quality, high spectral resolution near-IR observations allow for relative age-dating of young post-starburst populations to within 2 − 3 Myr, at least at solar metallicity (Gilbert, this workshop).

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“…The predicted contributions of C-stars to the near-IR light of intermediate age populations are consistent with those observed in the Magellanic Clouds (e.g. [18]). One of us (M.M.)…”

Section: Model Construction and Predictionssupporting

confidence: 85%

Post-Starburst Populations Near and Far — The Potential of Near-IR Spectroscopy

Lançon

Mouhcine

2001

Starburst Galaxies: Near and Far

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“…The empirical photometric calibration of the models has been done with the near-IR photometric data of LMC globular clusters and AGB stars of Persson et al (1983) and Frogel et al (1990). Spectra of carbon-rich stars are also included.…”

Section: Different Carbon Stars In Lmc and Milky Way?mentioning

confidence: 99%

IntegratedK-band spectra of old and intermediate-age globular clusters in the Large Magellanic Cloud

Lyubenova

Küntschner²,

Rejkuba

et al. 2010

A&A

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Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project whose aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for future ones. Our pilot study presents spatially integrated K-band spectra of three old (≥10 Gyr) and metal poor ([Fe/H] ∼ −1.4), and three intermediate age (1-2 Gyr) and more metal rich ([Fe/H] ∼ −0.4) globular clusters in the LMC. We measured the line strengths of the Na i, Ca i and 12 CO (2-0) absorption features. The Na i index decreases with increasing age and decreasing metallicity of the clusters. The D CO index, used to measure the 12 CO (2-0) line strength, is significantly reduced by the presence of carbon-rich TP-AGB stars in the globular clusters with age ∼1 Gyr. This is in contradiction to the predictions of the stellar population models of Maraston (2005, MNRAS, 362, 799). We find that this disagreement is due to the different CO absorption strength of carbon-rich Milky Way TP-AGB stars used in the models and the LMC carbon stars in our sample. For globular clusters with age ≥2 Gyr we find D CO index measurements consistent with the model predictions.

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“…In each diagram we display the data of Persson et al (1983) for LMC (open circles) and SMC (filled circles) clusters, the LMC clusters calculated by Pretto (2002) (open squares), the SSPs by , the old SSPs by Tantalo (1998), and the new ones of this study. The SSPs of and Tantalo (1998) extend toward bluer colors than the other SSPs.…”

Section: Broad-band Colors In the Infraredmentioning

confidence: 99%

Shells of dust around AGB stars: Effects on the integrated spectrum of Single Stellar Populations

Piovan¹,

Tantalo²,

Chiosi³

2003

A&A

172

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Abstract. In this paper we present models for Single Stellar Populations (SSPs) of intermediate and old ages where dust enshrouded Asymptotic Giant Branch (AGB) stars are introduced. As long known AGB stars are surrounded by dust-rich shells of matter caused by their own stellar wind, which absorb the radiation coming from the central object and re-emit it in the far infrared (IR). To this aim, particular care is devoted to follow the evolution of the AGB stars throughout the quiet and thermally pulsing regimes, to evaluate the effect of self contamination in the outermost layers by the third dredge-up mechanism, to follow the transition from oxygen-rich to carbon-rich objects (as appropriate to their initial mass and chemical composition), and finally to estimate the efficiency of mass-loss by stellar winds, all aspects that concur to the formation and properties of the dusty shells around. In addition to this, accurate physical models of the dusty shells are presented in which the re-processing of radiation from the central stars is calculated by solving the radiative transfer equations in presence of dust particles of different chemical composition. The resulting spectral energy distribution (SED) is examined to show how important features, like the 10 µm Si−O stretching mode feature and the 11 µm SiC feature, evolve with time. The SEDs are then convolved with the IRAS filters to obtain the flux in various pass-bands, i.e. 12, 25 and 60 µm, for individual AGB stars of different mass, chemical composition, and age. The comparison is made by means of SSPs along which AGB stars of the same age but different initial masses are located. This allows us to explore the whole range of masses and ages spanned by AGB stars. The theoretical results are compared to the observational data for selected groups of stars. The same is made for the J, H, K, L pass-bands of the Johnson system. Finally, from the integrated SEDs of the SSPs, we derive the integrated Johnson J, H, K, L magnitudes and colors to be compared to infrared data for star clusters of the Magellanic Clouds. In general good agreement with the data is possible if the effects of the circumstellar shells of dust are taken into account.

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Photometric studies of composite stellar systems. V - Infrared photometry of star clusters in the Magellanic clouds

Cited by 140 publications

References 5 publications

Post-Starburst Populations Near and Far — The Potential of Near-IR Spectroscopy

Post-Starburst Populations Near and Far — The Potential of Near-IR Spectroscopy

IntegratedK-band spectra of old and intermediate-age globular clusters in the Large Magellanic Cloud

Shells of dust around AGB stars: Effects on the integrated spectrum of Single Stellar Populations

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