J/MNRAS/493/1109 Aliphatic hydrocarbon within interstellar dust (Gunay+, 2020)
A method for mapping the aliphatic hydrocarbon content of interstellar dust
towards the Galactic Centre.
Gunay B., Burton M.G., Afsar M., Schmidt T.W.
<Mon. Not. R. Astron. Soc., 493, 1109-1119 (2020)>
=2020MNRAS.493.1109G 2020MNRAS.493.1109G (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Milky Way ; Photometry, infrared ;
Positional data
Keywords: methods: observational - techniques: photometric - infrared: ISM -
ISM: dust, extinction - ISM: abundances - astrochemistry
Abstract:
In the interstellar medium, the cosmic elemental carbon abundance
includes the total carbon in both gas and solid phases. The aim of the
study was to trial a new method for measuring the amount and
distribution of aliphatic carbon within interstellar dust over wide
fields of view of our Galaxy. This method is based on the measurement
of the 3.4-µm absorption feature from aliphatic carbonaceous
matter. This can readily be achieved for single sources using infrared
(IR) spectrometers. However, making such measurements over wide fields
requires an imaging IR camera, equipped with narrow-band filters that
are able to sample the spectrum. While this cannot produce as good a
determination of the spectra, the technique can be applied to
potentially tens to hundreds of sources simultaneously, over the field
of view of the camera. We examined this method for a field in the
centre of the Galaxy, and produced a map showing the variation of
3.4-µm optical depth across it.
Description:
Observations were carried out with the UIST instrument on the 3.8-m
United Kingdom Infrared Telescope (UKIRT).
Spectrophotometric measurements were obtained using narrow-band
filters to build low-resolution spectra of stars towards the Galactic
Centre. We aimed at determining how well the optical depth of the
3.4-µm absorption feature could be measured by taking images using
a suite of narrow-band filters spread across the 3.4-µm Lband: 3.05
ice MK, 3.29 PAH MK, 3.4 nbL, 3.5 mbL, 3.6 nbL', 3.99 (cont).
The observing strategy was to image the Galactic Centre with a 3x3
jitter pattern with a 20-arcsec grid. We applied 1-min integration per
jitter position. The pixel scale was 0.12arcsec.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 20 200 Calibrated fluxes of the Galactic Centre sources
used for optical depth calculations
table8.dat 26 200 Celestial coordinates and the optical depths
from the 3.4-µm absorption feature along the
line of sight of the Galactic Centre sources
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/200] Internal source identifier (G1)
5- 9 F5.1 10-18W/cm2/um S3.3 3.3µm calibrated flux
11- 14 F4.1 10-18W/cm2/um S3.4 3.4µm calibrated flux
16- 20 F5.1 10-18W/cm2/um S3.6 3.6µm calibrated flux
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID [1/200] Internal source identifier (G1)
5- 12 F8.4 deg GLON Galactic longitude
14- 21 F8.4 deg GLAT Galactic latitude
23- 26 F4.2 --- tau3.4 Optical depth from the 3.4µm absorption
feature
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Global Notes:
Note (G1): The source numbers of the calibration sources and the test group
stars: 1 - GCIRS 7, 2 - GCIRS 1W, 3 - GCIRS 3, 4 - GCIRS 13,
6 - GCIRS 21, 13 - GCIRS 29, 14 - GCIRS 6E, 21 - GCIRS 9,
31 - GCIRS 16 NE, and 96 - GCIRS 16C
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 11-Apr-2023