The Magellanic Zoo: Mid‐Infrared<i>Spitzer</i>Spectroscopy of Evolved Stars and Circumstellar Dust in the Magellanic Clouds

Sloan, G. C.; Kraemer, K. E.; Wood, P. R.; Zijlstra, A. A.; Bernard─Salas, J.; Devost, D.; Houck, J. R.

doi:10.1086/591437

Cited by 102 publications

(176 citation statements)

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“…The theoretical work of Mattsson et al (2008) and Wachter et al (2008) showed that the mass-loss rates of carbon stars may not be sensitive to metallicity. Numerous recent studies using Spitzer spectra of AGB stars in low-metallicity Local Group galaxies (e.g., Sloan et al 2006;Zijlstra et al 2006;Lagadec et al 2007;Matsuura et al 2007;Sloan et al 2008) seem to support this claim. Similar results were obtained by Groenewegen et al (2007), who found in their modeling of the IRS spectra of 60 carbon stars in the Magellanic Clouds that the trend of mass-loss rates with period of luminosity was comparable to that of Galactic sources.…”

Section: Introductionmentioning

confidence: 91%

The mass-loss return from evolved stars to the Large Magellanic Cloud

Srinivasan

Sargent

Matsuura

et al. 2010

A&A

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We present a radiative transfer model for the circumstellar dust shell around a Large Magellanic Cloud (LMC) long-period variable (LPV) previously studied as part of the Optical Gravitational Lensing Experiment (OGLE) survey of the LMC. OGLE LMC LPV 28579 (SAGE J051306.40-690946.3) is a carbon-rich asymptotic giant branch (AGB) star for which we have Spitzer broadband photometry and spectra from the SAGE and SAGE-Spec programs along with broadband UBVIJHK s photometry. By modeling this source, we obtain a baseline set of dust properties to be used in the construction of a grid of models for carbon stars. We reproduce the spectral energy distribution of the source using a mixture of amorphous carbon and silicon carbide with 15% SiC by mass. The grain sizes are distributed according to the KMH model, with γ = 3.5, a min = 0.01 μm and a 0 = 1.0 μm. The best-fit model produces an optical depth of 0.28 for the dust shell at the peak of the SiC feature (11.3 μm), with an inner radius of about 1430 R or 4.4 times the stellar radius. The temperature at this inner radius is 1310 K. Assuming an expansion velocity of 10 km s −1 , we obtain a dust mass-loss rate of 2.5 × 10 −9 M yr −1 . We calculate a 15% variation in this mass-loss rate by testing the sensitivity of the fit to variation in the input parameters. We also present a simple model for the molecular gas in the extended atmosphere that could give rise to the 13.7 μm feature seen in the spectrum. We find that a combination of CO and C 2 H 2 gas at an excitation temperature of about 1000 K and column densities of 3 × 10 21 cm −2 and 10 19 cm −2 respectively are able to reproduce the observations. Given that the excitation temperature is close to the temperature of the dust at the inner radius, most of the molecular contribution probably arises from this region. The luminosity corresponding to the first epoch of SAGE observations is 6580 L . For an effective temperature of about 3000 K, this implies a stellar mass of 1.5−2 M and an age of 1−2.5 Gyr for OGLE LMC LPV 28579. We calculate a gas mass-loss rate of 5.0 × 10 −7 M yr −1 assuming a gas:dust ratio of 200. This number is comparable to the gas mass-loss rates estimated from the period, color and 8 μm flux of the source.

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Section: Introductionmentioning

confidence: 91%

The mass-loss return from evolved stars to the Large Magellanic Cloud

Srinivasan

Sargent

Matsuura

et al. 2010

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“…The lack of a UV bump could also be caused by efficient grain destruction Sloan et al 2008) favoured by lower dust column densities and harder radiation fields due to the low metallicity. If carbonaceous carriers of the UV bump are more sensitive to harsh environments than silicate ones, then the UV bump strength may be lower in carbon-dust dominated low-metallicity environments than in high-metallicity galaxies, where the dominant population of silicates may also act as carriers of the UV bump.…”

Section: The Carriers Of the Uv Bump And Other Small-size Dust Componmentioning

confidence: 99%

GMASS ultradeep spectroscopy of galaxies at z ~ 2

Noll

Pierini

Cimatti

et al. 2009

A&A

112

175

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Aims. The properties of dust attenuation at rest-frame UV wavelengths are inferred from very high-quality FORS 2 spectra of 78 galaxies from the GMASS survey at redshift 1 < z < 2.5. These objects complement a previously investigated sample of 108 UV-luminous, intermediate-mass (i.e., with stellar masses ∼10 10 −10 11 M ) galaxies at similar redshifts, selected from the FDF spectroscopic survey, the K20 survey, and the GDDS. Detection of the broad absorption feature centred on about 2175 Å ("UV bump") implies that the average UV extinction curve of a galaxy more closely resembles that of the Milky Way (MW) or the Large Magellanic Cloud (LMC), and differs from that of the Small Magellanic Cloud (SMC). Methods. The shape of the UV extinction curve is constrained by a parametric description of the rest-frame UV continuum with the support of a suite of models combining radiative transfer and stellar population synthesis. The UV bump is further characterised by fitting Lorentzian-like profiles. Results. Spectra exhibit a significant 2175 Å feature in at least 30% of the cases, especially those suffering from substantial reddening. If attenuation is dominated by dust ejected from the galaxy main body via galactic winds or more localised superwinds, UV extinction curves in-between those of the SMC and LMC characterise UV-luminous, intermediate-mass galaxies at 1 < z < 2.5. The fraction of galaxies with extinction curves differing from the SMC one increases, if more dust resides in the galactic plane or dust attenuation depends on stellar age. On average, the width of the manifested UV bumps is about 60% of the values typically measured along sightlines in the LMC and MW. This suggests the presence of dust similar to that found in the "supergiant" shell of ionised filaments LMC 2, close to 30 Dor. The presence of the carriers of the UV bump (probably organic carbon and amorphous silicates) at 1 < z < 2.5 argues for outflows from asymptotic giant branch (AGB) stars being copious then. Consistent with their higher star-formation rates, the GMASS galaxies with a manifested UV bump are more luminous at rest-frame 8 μm, where the emission is dominated by polycyclic aromatic hydrocarbons (also products of AGB stars). In addition, they exhibit larger equivalent widths for prominent UV (metal) absorption features, mostly of interstellar origin, which indicates overall more evolved stellar populations. Conclusions. We conclude that diversification of the small-size dust component (responsible for the differential extinction at UV wavelengths and the emission at mid-IR wavelengths) has already started in the most evolved star-forming systems at 1 < z < 2.5.

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“…The mass-loss efficiency in O-rich stars depends more on metallicity than in C-rich stars, because O-rich dust depends on metallicity-limited elements (Si, Al), while amorphous carbon depends on self-produced C (e.g., Sloan et al 2008Sloan et al , 2012.…”

Section: Mass-loss Ratesmentioning

confidence: 99%

Oxygen-rich dust production in IC 10

Lebouteiller¹,

Sloan²,

Groenewegen³

et al. 2012

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Context. We report the detection of oxygen-rich circumstellar envelopes in stars of the nearby (700 kpc) starburst galaxy IC 10. The star-formation history and the chemical environment of this galaxy make it an ideal target to observe dust production by massive stars in a metal-poor environment. Aims. The goal of this study is to identify oxygen-rich stars in IC 10 and to constrain their nature between asymptotic giant branch stars (AGBs), red supergiants (RSGs), and other bright infrared sources. We examine the mass-loss rates of the stars and compare to results obtained for the Magellanic Clouds. Our objectives are to (1) assess whether RSGs can be significant dust producers in IC 10, and (2), solve the discrepancy between the star-formation history of IC 10 and the relatively low number of RSGs detected in the optical. Methods. We search for silicate dust in emission by using the spectral map observed with the Infrared Spectrograph on board the Spitzer Space Telescope. The optical (UBVRI) and infrared (JHK, Spitzer/IRAC and Spitzer/MIPS) photometry are used to assert the membership of the stars to IC 10 and distinguish between AGBs and RSGs. Radiative models are used to infer mass-loss rates and stellar luminosities. Results. The luminosity and colors of at least 9 silicate emission sources are consistent with stars within IC 10. Furthermore, the photometry of 2 of these sources is consistent with RSGs. We derive dust mass-loss rates similar to the values found in the Magellanic Clouds. Accounting for the sample completeness, RSGs are not important contributors to the dust mass budget in IC 10.

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The Magellanic Zoo: Mid‐InfraredSpitzerSpectroscopy of Evolved Stars and Circumstellar Dust in the Magellanic Clouds

Cited by 102 publications

References 98 publications

The mass-loss return from evolved stars to the Large Magellanic Cloud

The mass-loss return from evolved stars to the Large Magellanic Cloud

GMASS ultradeep spectroscopy of galaxies at z ~ 2

Oxygen-rich dust production in IC 10

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