Hydrocarbons, Ices, and “XCN” in the Line of Sight toward the Galactic Center

Chiar, J. E.; Adamson, A. J.; Pendleton, Y. J.; Whittet, D. C. B.; Caldwell, Douglas A.; Gibb, E. L.

doi:10.1086/339570

Cited by 76 publications

(127 citation statements)

References 74 publications

Supporting

Mentioning

113

Contrasting

Order By: Relevance

“…The 3.4 m feature and an associated subfeature at 3.48 m have been seen toward many GC sources. They are most likely due to aliphatic hydrocarbons that are characterized by their CH 2 (methylene) and CH 3 (methyl) stretching modes (Sandford et al 1991;Pendleton et al 1994;Duley & Williams 1983;Chiar et al 2002). They are known to arise in the diffuse interstellar medium.…”

Section: A Cluster Of Young Starsmentioning

confidence: 99%

Young Stars at the Center of the Milky Way?

Eckart

Moultaka

Viehmann

et al. 2004

ApJ

View full text Add to dashboard Cite

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.

show abstract

Section: A Cluster Of Young Starsmentioning

confidence: 99%

Young Stars at the Center of the Milky Way?

Eckart

Moultaka

Viehmann

et al. 2004

ApJ

View full text Add to dashboard Cite

show abstract

“…The features contributing to this absorption band A&A 569, A119 (2014) were early associated to sp 3 CH 3 and CH 2 stretching modes, as stated for example in Duley & Williams (1983). Since then, numerous experiments, observations and models have been employed to constrain its origin (e.g., Jones et al 1983Jones et al , 2013Butchart et al 1986;Mc Fadzean et al 1989;Ehrenfreund et al 1991;Sandford et al 1991Sandford et al , 1995Pendleton et al 1994;Tielens et al 1996;Geballe et al 1998;Muñoz Caro et al 2001;Chiar et al 2002;Mennella et al 2002;Pendleton & Allamandola 2002;Dartois et al 2005;Godard et al 2012). The a-C:H Galactic abundance has been estimated from the observed CH stretching modes.…”

Section: Introductionmentioning

confidence: 99%

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Alata

Cruz-Díaz

Muñoz

et al. 2014

A&A

119

View full text Add to dashboard Cite

Context. The interstellar hydrogenated amorphous carbons (HAC or a-C:H) observed in the diffuse medium are expected to disappear in a few million years, according to the destruction time scale from laboratory measurements. The existence of a-C:H results from the equilibrium between photodesorption, radiolysis, hydrogenation and resilience of the carbonaceous network. During this processing, many species are therefore injected into the gas phase, in particular H 2 , but also small organic molecules, radicals or fragments. Aims. We perform experiments on interstellar a-C:H analogs to quantify the release of these species in the interstellar medium. Methods. The vacuum ultraviolet (VUV) photolysis of interstellar hydrogenated amorphous carbon analogs was performed at low (10 K) to ambient temperature, coupled to mass-spectrometry detection and temperature-programed desorption. Using deuterium isotopic substitution, the species produced were unambiguously separated from background contributions. Results. The VUV photolysis of hydrogenated amorphous carbons leads to the efficient production of H 2 molecules, but also to small hydrocarbons. Conclusions. These species are formed predominantly in the bulk of the a-C:H analog carbonaceous network, in addition to the surface formation. Compared with species made by the recombination of H atoms and physisorbed on surfaces, they diffuse out at higher temperatures. In addition to the efficient production rate, it provides a significant formation route in environments where the short residence time scale for H atoms inhibits H 2 formation on the surface, such as PDRs. The photolytic bulk production of H 2 with carbonaceous hydrogenated amorphous carbon dust grains can provide a very large portion of the contribution to the H 2 molecule formation. These dust grains also release small hydrocarbons (such as CH 4 ) into the diffuse interstellar medium, which contribute to the formation of small carbonaceous radicals after being dissociated by the UV photons in the considered environment. This extends the interstellar media environments where H 2 and small hydrocarbons can be produced.

show abstract

“…The water ice band interferes with absorption bands of additional materials that are dissolved in water ice or form a complex compound with the water molecule: ammonia hydrate H 2 O.NH 3 (minimum at 3.47 μm: Merrill et al 1976;Mukai et al 1986;Dartois & d'Hendecourt 2001), ammonia NH 3 (2.96 μm: d 'Hendecourt et al 1985;Dartois & d'Hendecourt 1985), methanol CH 3 OH (3.54 μm: Dartois et al 2001), hydrocarbons with the vibrational excitations of the CH, CH 2 , and CH 3 bond (3.38 μm, 3.42 μm, and 3.48 μm: Duley & Williams 1984;Chiar et al 2002), and other chemical compounds (Ehrenfreund et al 1996). The absorption bands of these molecules are narrow and interfere predominantly with the water ice band at longer wavelengths around 3.6 μm.…”

Section: Introductionmentioning

confidence: 99%

Spatially resolved detection of crystallized water ice in a T Tauri object

Schegerer

Wolf

2010

A&A

View full text Add to dashboard Cite

Aims. We search for frozen water and its processing around young stellar objects (YSOs of class I/II). We try to detect potential, regional differences in water ice evolution within YSOs, which is relevant to understanding the chemical structure of the progenitors of protoplanetary systems and the evolution of solid materials. Water plays an important role as a reaction bed for rich chemistry and is an indispensable requirement for life as known on Earth.Methods. We present our analysis of NAOS-CONICA/VLT spectroscopy of water ice at 3 μm for the T Tauri star YLW 16 A in the ρ Ophiuchi molecular cloud. We obtained spectra for different regions of the circumstellar environment. The observed absorption profiles are deconvolved with the mass extinction profiles of amorphous and crystallized ice measured in laboratory. We take into account both absorption and scattering by ice grains. Results. Water ice in YLW16A is detected with optical depths of between τ = 1.8 and τ = 2.5. The profiles that are measured can be fitted predominantly by the extinction profiles of small grains (0.1 μm-0.3 μm) with a small contribution from large grains (<10%). However, an unambiguous trace of grain growth cannot be found. We detected crystallized water ice spectra that have their origin in different regions of the circumstellar environment of the T Tauri star YLW 16 A. The crystallinity increases in the upper layers of the circumstellar disk, while only amorphous grains exist in the bipolar envelope. As in studies of silicate grains in T Tauri objects, the higher crystallinity in the upper layers of the outer disk regions implies that water ice crystallizes and remains crystallized close to the disk atmosphere where water ice is shielded against hard irradiation.

show abstract

Hydrocarbons, Ices, and “XCN” in the Line of Sight toward the Galactic Center

Cited by 76 publications

References 74 publications

Young Stars at the Center of the Milky Way?

Young Stars at the Center of the Milky Way?

Vacuum ultraviolet photolysis of hydrogenated amorphous carbons

Spatially resolved detection of crystallized water ice in a T Tauri object

Contact Info

Product

Resources

About