Infrared spectra of complex organic molecules in astronomically relevant ice matrices. III. Methyl formate and its tentative solid-state detection. (arXiv:2105.02226v1 [astro-ph.SR])

Infrared spectra of complex organic molecules in astronomically relevant ice matrices. III. Methyl formate and its tentative solid-state detection. (arXiv:2105.02226v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Scheltinga_J/0/1/0/all/0/1">Jeroen Terwisscha van Scheltinga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marcandalli_G/0/1/0/all/0/1">Giulia Marcandalli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McClure_M/0/1/0/all/0/1">Melissa K. McClure</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hogerheijde_M/0/1/0/all/0/1">Michiel R. Hogerheijde</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Linnartz_H/0/1/0/all/0/1">Harold Linnartz</a>

Context. Infrared spectroscopy of star and planet forming regions is at the
dawn of a new age with the upcoming James Webb Space Telescope. 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 reference spectra to firmly detect icy
methyl formate in the different stages of star and planet forming regions.
Methyl formate is mixed in astronomically relevant matrices, and the peak
positions, FWHMs, and relative band intensities are characterized for different
temperatures to provide an analytical tool for astronomers.

Methods. Methyl formate is deposited at 15 K 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. Throughout the experiment
infrared spectra are acquired with a FTIR spectrometer in the range from
4000-500 cm$^{-1}$ (2.5-20 $mu$m) 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, C$-$O stretch, CH$_3$
rocking, O$-$CH$_3$ stretching, and OCO deformation, are best suited for a JWST
identification of methyl formate. For each of these vibrational modes, and each
of the mixtures the TvS heatmaps, peak position versus FWHM, and relative band
intensities are given. Additionally, the acquired reference spectra of methyl
formate are compared with Spitzer observations of HH 46. A tentative detection
of methyl formate provides an upper limit to the column density of
$1.7times10^{17}$ cm$^{-2}$, corresponding to an upper limit relative to water
of $leq 2.2%$ and $leq 40%$ with respect to methanol.

Context. Infrared spectroscopy of star and planet forming regions is at the
dawn of a new age with the upcoming James Webb Space Telescope. 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 reference spectra to firmly detect icy
methyl formate in the different stages of star and planet forming regions.
Methyl formate is mixed in astronomically relevant matrices, and the peak
positions, FWHMs, and relative band intensities are characterized for different
temperatures to provide an analytical tool for astronomers.

Methods. Methyl formate is deposited at 15 K 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. Throughout the experiment
infrared spectra are acquired with a FTIR spectrometer in the range from
4000-500 cm$^{-1}$ (2.5-20 $mu$m) 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, C$-$O stretch, CH$_3$
rocking, O$-$CH$_3$ stretching, and OCO deformation, are best suited for a JWST
identification of methyl formate. For each of these vibrational modes, and each
of the mixtures the TvS heatmaps, peak position versus FWHM, and relative band
intensities are given. Additionally, the acquired reference spectra of methyl
formate are compared with Spitzer observations of HH 46. A tentative detection
of methyl formate provides an upper limit to the column density of
$1.7times10^{17}$ cm$^{-2}$, corresponding to an upper limit relative to water
of $leq 2.2%$ and $leq 40%$ with respect to methanol.

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