Infrared spectra of protostars - Composition of the dust shells

Willner, S. P.; Gillett, F. C.; Herter, T.; Jones, B.; Krassner, J.; Merrill, K. M.; Pipher, J. L.; Puetter, R. C.; Rudy, R. J.; Russell, R. W.; Soifer, B. T.

doi:10.1086/159622

Cited by 169 publications

(88 citation statements)

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“…These objects are all well clustered in the two-color diagram and after taking into account the %30 mag of visual extinction toward the GC, these objects fall close to the location of hot and massive stars near the main sequence. The Joyce & Simon (1982) and Willner et al (1982). Their photometric data are taken from the infrared catalog by Gezari et al (1993).…”

Section: The New Ir-excess Sourcesmentioning

confidence: 99%

Young Stars at the Center of the Milky Way?

Eckart

Moultaka

Viehmann

et al. 2004

ApJ

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We present results from the first diffraction-limited images of the Galactic center (GC) at 1.6, 2.1, and 3.8 m with the new adaptive optics (AO) camera NAOS/CONICA at the ESO Very Large Telescope, as well as 3-4 m low-resolution spectroscopy. We have discovered a small (0.13 lt-yr diameter) cluster of compact sources about 0B5 north of IRS 13 with strong IR excesses due to T > 500 K dust. The nature of the sources is unclear. They may be a cluster of highly extincted stars that heat the local environment of the minispiral. We also consider an explanation that involves the presence of young stars at evolutionary stages between young stellar objects and Herbig Ae/Be objects with ages of about 0.1 to 1 million yr. This scenario would imply more recent star formation in the GC than previously suspected. The AO observations also resolve the central IRS 13 complex. In addition to the previously known bright stars E1 and E2, the K-and L 0 -band images for the first time resolve object E3 into two components, E3N and E3c. The latter one is closest to the 7 mm Very Large Array radio continuum source found at the location of the IRS 13 complex. E3c may be associated with a strong stellar wind or a dusty Wolf-Rayet-like star at that location.

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Section: The New Ir-excess Sourcesmentioning

confidence: 99%

Young Stars at the Center of the Milky Way?

Eckart

Moultaka

Viehmann

et al. 2004

ApJ

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“…Superimposed on the IR continua of many sources are absorption bands (Merrill et al 1976;Willner et al 1982) which, because of their widths, have been attributed to vibrational transitions of molecules in ices (Whittet 1993). Among the (simple) molecules that have been identified in interstellar grains are: H 2 O, CO 2 , CH 3 OH, CO and CH 4 , which are believed to be frozen onto the grain mantles .…”

Section: Introductionmentioning

confidence: 99%

“…Broad 6.0 µm and 6.85 µm absorption features dominate the 5-8 µm region and were previously investigated with the aid of low resolution airborne spectroscopy (Willner et al 1982;Tielens et al 1984;Tielens & Allamandola 1987;d'Hendecourt et al 1996;Schutte et al 1996). These results seemed to indicate that both features were nearly always constant in position and width.…”

Section: Introductionmentioning

confidence: 99%

Ice absorption features in the 5-8μm region toward embedded protostars

Keane¹,

Tielens

Boogert

et al. 2001

A&A

234

295

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Abstract.We have obtained 5-8 µm spectra towards 10 embedded protostars using the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS) with the aim of studying the composition of interstellar ices. The spectra are dominated by absorption bands at 6.0 µm and 6.85 µm. The observed peak positions, widths and relative intensities of these bands vary dramatically along the different lines of sight. On the basis of comparison with laboratory spectra, the bulk of the 6.0 µm absorption band is assigned to amorphous H2O ice. Additional absorption, in this band, is seen toward 5 sources on the short wavelength wing, near 5.8 µm, and the long wavelength side near 6.2 µm. We attribute the short wavelength absorption to a combination of formic acid (HCOOH) and formaldehyde (H2CO), while the long wavelength absorption has been assigned to the C-C stretching mode of aromatic structures. From an analysis of the 6.85 µm band, we conclude that this band is composed of two components: a volatile component centered near 6.75 µm and a more refractory component at 6.95 µm. From a comparison with various temperature tracers of the thermal history of interstellar ices, we conclude that the two 6.85 µm components are related through thermal processing. We explore several possible carriers of the 6.85 µm absorption band, but no satisfactory identification can be made at present. Finally, we discuss the possible implications for the origin and evolution of interstellar ices that arise from these new results.

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“…Such upper limits are of major importance as a criterion to test any model proposed for this reduction. A direct integration of the optical depth of the 3.4 µm band towards embedded protostars is difficult, due to the presence of broad absorption features in this region, such as the 3.05 µm H 2 O band, the "diamond" feature at 3.47 µm (Allamandola et al 1992;Chiar et al 1996;Brooke et al 1999), the 3.25 µm band with frozen PAHs as possible carrier (Sellgren et al , 1995, the CH stretch modes of solid CH 3 OH at 3.48 µm and 3.54 µm (Grim et al 1991;Allamandola et al 1992;Schutte et al 1996;d'Hendecourt et al 1996;Dartois et al 1999) and the "long wavelength shoulder" of the 3.05 µm feature centered around 3.4 µm (Willner et al 1982;Smith et al 1988). Instead, we obtained upper limits of the 3.4 µm feature in the dense medium by sequential addition of the 3.4 µm feature as observed towards a diffuse interstellar medium source, GC IRS6E (adopted from Pendleton et al 1994), to the spectra of four YSOs, namely GL 2136, MonR2/IRS2, W33A (Brooke et al 1999), NGC 7538/IRS9 (Allamandola et al 1992), as well as the background field star Elias 16 (Chiar et al 1996).…”

Section: Quantification Of the 34 µM Feature In Dense Cloudsmentioning

confidence: 99%

UV photodestruction of CH bonds and the evolution of the 3.4 μm feature carrier

Muñoz

Ruiterkamp

Schütte

et al. 2001

A&A

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Abstract. Experiments simulating the processing of various hydrocarbon species under diffuse and dense cloud conditions by UV irradiation were performed. The results indicate that such molecules will be efficiently dehydrogenated in interstellar space. It is argued that the presence of hydrogen in the aliphatic grain material in diffuse clouds results from an equilibrium between dehydrogenation by UV processing and re-hydrogenation by the impinging atomic gas. In dense clouds, the presence of the ice layer will prevent the re-hydrogenation process, causing the carbonaceous grain material to be gradually de-hydrogenated if UV photons are able to penetrate into the dense medium. The implications of this study for the evolution of the carbonaceous component of dust in the interstellar medium are discussed.

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Infrared spectra of protostars - Composition of the dust shells

Cited by 169 publications

References 0 publications

Young Stars at the Center of the Milky Way?

Young Stars at the Center of the Milky Way?

Ice absorption features in the 5-8μm region toward embedded protostars

UV photodestruction of CH bonds and the evolution of the 3.4 μm feature carrier

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