W. G. Sebald

Schütte, Uwe

doi:10.36198/9783838535388

Cited by 27 publications

(45 citation statements)

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“…These targets are also part of the JWST/MIRI guaranteed time observations (GTO) program (project ID 1290). The JWST/MIRI will, for instance, observe the 7.2 and 7.4 µm features for which CH 3 CH 2 OH and CH 3 CHO, respectively, are strong candidates based on laboratory spectroscopy (e.g., Schutte et al 1999;Terwisscha van Scheltinga et al 2018). Ultimately, this will allow gaseous and icy COMs to be directly compared.…”

Section: Introductionmentioning

confidence: 99%

Complex organic molecules in low-mass protostars on Solar System scales

Gelder

Tabone

Tychoniec

et al. 2020

A&A

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Context. Complex organic molecules (COMs) are thought to form on icy dust grains in the earliest phase of star formation. The evolution of these COMs from the youngest Class 0/I protostellar phases toward the more evolved Class II phase is still not fully understood. Since planet formation seems to start early, and mature disks are too cold for characteristic COM emission lines, studying the inventory of COMs on Solar- System scales in the Class 0/I stage is relevant. Aims. Our aim is to determine the abundance ratios of oxygen-bearing COMs in Class 0 protostellar systems on scales of ~100 AU radius. We aim to compare these abundances with one another, and to the abundances of other low-mass protostars such as IRAS 16293-2422B and HH 212. Additionally, using both cold and hot COM lines, the gas-phase abundances can be tracked from a cold to a hot component, and ultimately be compared with those in ices to be measured with the James Webb Space Telescope (JWST). The abundance of deuterated methanol allows us to probe the ambient temperature during the formation of this species. Methods. ALMA Band 3 (3 mm) and Band 6 (1 mm) observations are obtained for seven Class 0 protostars in the Perseus and Serpens star-forming regions. By modeling the inner protostellar region using local thermodynamic equilibrium models, the excitation temperature and column densities are determined for several O-bearing COMs including methanol (CH3OH), acetaldehyde (CH3CHO), methyl formate (CH3OCHO), and dimethyl ether (CH3OCH3). Abundance ratios are taken with respect to CH3OH. Results. Three out of the seven of the observed sources, B1-c, B1-bS (both Perseus), and Serpens S68N (Serpens), show COM emission. No clear correlation seems to exist between the occurrence of COMs and source luminosity. The abundances of several COMs such as CH3OCHO, CH3OCH3, acetone (CH3COCH3), and ethylene glycol ((CH2OH)2) are remarkably similar for the three COM-rich sources; this similarity also extends to IRAS 16293-2422B and HH 212, even though collectively these sources originate from four different star-forming regions (i.e., Perseus, Serpens, Ophiuchus, and Orion). For other COMs like CH3CHO, ethanol (CH3CH2OH), and glycolaldehyde (CH2OHCHO), the abundances differ by up to an order of magnitude, indicating that local source conditions become important. B1-c hosts a cold (Tex ≈ 60 K), more extended component of COM emission with a column density of typically a few percent of the warm/hot (Tex ~ 200 K) central component. A D/H ratio of 1–3% is derived for B1-c, S68N, and B1-bS based on the CH2DOH/CH3OH ratio (taking into account statistical weighting) suggesting a temperature of ~15 K during the formation of methanol. This ratio is consistent with other low-mass protostars, but is lower than for high-mass star-forming regions. Conclusions. The abundance ratios of most O-bearing COMs are roughly fixed between different star-forming regions, and are presumably set at an earlier cold prestellar phase. For several COMs, local source properties become important. Future mid-infrared facilities such as JWST/MIRI will be essential for the direct observation of COM ices. Combining this with a larger sample of COM-rich sources with ALMA will allow ice and gas-phase abundances to be directly linked in order to constrain the routes that produce and maintain chemical complexity during the star formation process.

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Section: Introductionmentioning

confidence: 99%

Complex organic molecules in low-mass protostars on Solar System scales

Gelder

Tabone

Tychoniec

et al. 2020

A&A

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“…This is interesting as methanol is a stepping stone towards larger COMs, such as acetaldehyde (CH 3 CHO), ethanol (CH 3 CH 2 OH), dimethyl ether (CH 3 OCH 3 ), methyl formate (HCOOCH 3 ), and glycolaldehyde (HOCH 2 CHO) as shown by laboratory studies (e.g., Bennett & Kaiser 2007;Öberg et al 2009b;Modica et al 2012;Muñoz Caro et al 2014;Chuang et al 2016;Fedoseev et al 2017). Of these larger COMs two, acetaldehyde and ethanol ice, have been tentatively detected in the massive embedded protostar W33A (Schutte et al 1999;Öberg et al 2011). COMs are, however, frequently observed in the gas Wavelength ( m) Fig.…”

Section: Introductionmentioning

confidence: 92%

“…Previous observations with ISO and Spitzer have observed such sources and their spectral resolution and sensitivity allowed for the detection of some smaller solid-state species, including methanol (e.g., Boogert et al 2015). A few COMs have been tentatively identified in the massive embedded protostar W33A, namely acetaldehyde, ethanol, and formic acid (Schutte et al 1999;Öberg et al 2011). The reanalysis of the ISO W33A spectrum with laboratory spectra in Terwisscha van Scheltinga et al ( 2018) shows that it is likely possible to determine with JWST in which astronomically relevant ice matrix these COMs reside.…”

Section: Infrared Observationsmentioning

confidence: 99%

“…Infrared absorption features around 7 µm towards protostars show potential for COM identification with JWST, e.g., in W33A the absorption features at 7.25 and 7.41 µm are tentatively identified as ethanol and acetaldehyde, respectively (Schutte et al 1999;Öberg et al 2011;Terwisscha van Scheltinga et al 2018). Another such potential regions is the 11 µm region, since some protostars have an additional feature on the 10 µm silicate feature.…”

Section: The 11 µM Featurementioning

confidence: 99%

“…In this way a spectral feature is not assigned to a specific molecule but to a specific class of molecules that generally are chemically related as well. This average apparent band strength is approximated by averaging the apparent band strengths of the molecules mentioned in Section 3.5 in a one-to-one ratio (Schutte et al 1999;Modica & Palumbo 2010;Bouilloud et al 2015;Hudson et al 2018). For the HH 46 spectrum we have fitted a Gaussian at 5.831 µm with a FWHM of 0.0544 µm, see Fig.…”

Section: The C=o Functional Groupmentioning

confidence: 99%

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Infrared spectra of complex organic molecules in astronomically relevant ice matrices. III. Methyl formate and its tentative solid-state detection

van Scheltinga,

Marcandalli,

McClure

et al. 2021

Preprint

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Context. Infrared spectroscopy of star and planet forming regions is at the dawn of a new age with the upcoming James Webb Space Telescope (JWST). Its high resolution and unprecedented sensitivity allows us to probe the chemical complexity of planet forming regions, such as dense clouds, embedded protostars, and protoplanetary disks, both in the solid state and gas phase. In support of these observations, laboratory spectra are required to identify complex organic molecules in the ices that cover the dust grains in these regions.Aims. This study aims to provide the necessary reference spectra to firmly detect methyl formate (HCOOCH 3 ) in the different evolutionary stages of star and planet forming regions. Methyl formate is mixed in astronomically relevant matrices, and the peak positions, full width at half maximum, and relative band intensities are characterized for different temperatures to provide an analytical tool for astronomers. Methods. Methyl formate is deposited at 15 Kelvin on a cryogenically cooled infrared transmissive window under high-vacuum conditions. Specifically, methyl formate is deposited pure and mixed with CO, H 2 CO, CH 3 OH, H 2 O, and CO:H 2 CO:CH 3 OH combined. The sample is linearly heated until all solid-state constituents have desorbed. Throughout the experiment infrared spectra are acquired with a Fourier Transform Infrared spectrometer in the range from 4000-500 cm −1 (2.5-20 µm) at a spectral resolution of 0.5 cm −1 . Results. We present the characterization of five solid-state methyl formate vibrational modes in pure and astronomically relevant ice matrices. The five selected vibrational modes, namely the C=O stretch (5.804 µm), the C−O stretch (8.256 µm), CH 3 rocking (8.582 µm), O−CH 3 stretching (10.98 µm), and OCO deformation (13.02 µm), are best suited for a JWST identification of methyl formate. For each of these vibrational modes, and each of the mixtures the temperature versus spectra heatmaps, peak position versus full width at half maximum and relative band intensities are given. All spectra are publicly available on the Leiden Ice Database. Additionally, the acquired reference spectra of methyl formate are compared with archival Spitzer observations of HH 46. A tentative detection of methyl formate provides an upper limit to the column density of 1.7 × 10 17 cm −2 , corresponding to an upper limit relative to water of ≤ 2.2% and ≤ 40% with respect to methanol.

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Herring Fisheries, Fish-Eating and Natural History in W. G. Sebald’s The Rings of Saturn

O’Key

2019

Literature and Meat Since 1900

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W. G. Sebald

Cited by 27 publications

References 0 publications

Complex organic molecules in low-mass protostars on Solar System scales

Complex organic molecules in low-mass protostars on Solar System scales

Infrared spectra of complex organic molecules in astronomically relevant ice matrices. III. Methyl formate and its tentative solid-state detection

Herring Fisheries, Fish-Eating and Natural History in W. G. Sebald’s The Rings of Saturn

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