J/A+A/636/A67 ALMA maps of 6 sources of star forming regions (Allen+, 2020)
Exploring the formation pathways of formamide. Near young O-type stars.
Allen V., van der Tak F.F.S., Lopez-Sepulcre A., Sanchez-Monge A.,
Rivilla V.M., Cesaroni R.
<Astron. Astrophys. 636, A67 (2020)>
=2020A&A...636A..67A 2020A&A...636A..67A (SIMBAD/NED BibCode)
ADC_Keywords: Star Forming Region ; Stars, O ; Interstellar medium ;
Interferometry ; Spectroscopy ; Models ; Abundances
Keywords: stars: massive - astrochemistry - submillimeter: ISM -
ISM: general - ISM: molecules
Abstract:
As a building block for amino acids, formamide (NH2CHO) is an
important molecule in astrobiology and astrochemistry,
but its formation path in the interstellar medium is not understood
well.
We aim to find empirical evidence to support the chemical
relationships of formamide to HNCO and H2CO.
We examine high angular resolution (∼0.2") Atacama Large
Millimeter/submillimeter Array (ALMA) maps of six sources in three
high-mass star-forming regions and compare the spatial extent,
integrated emission peak position, and velocity structure of HNCO and
H2CO line emission with that of NH2CHO by using moment maps.
Through spectral modeling, we compare the abundances of these three
species.
In these sources, the emission peak separation and velocity dispersion
of formamide emission is most often similar to HNCO emission, while
the velocity structure is generally just as similar to H2CO and HNCO
(within errors). From the spectral modeling, we see that the
abundances between all three of our focus species are correlated, and
the relationship between NH2CHO and HNCO reproduces the previously
demonstrated abundance relationship.
In this first interferometric study, which compares two potential
parent species to NH2CHO, we find that all moment maps for HNCO are
more similar to NH2CHO than H2CO in one of our six sources (G24
A1). For the other five sources, the relationship between NH2CHO,
HNCO, and H2CO is unclear as the different moment maps for each
source are not consistently more similar to one species as opposed to
the other.
Description:
The sources, G17.64+0.16 (hereafter G17), G24.78+0.08 (hereafter G24)
and G345.49+1.47 (hereafter G345) were observed with ALMA in Cycle 2
in July and September 2015 (2013.1.00489.S) in Band 6 with baselines
from 40 to 1500m. The observed frequency range was between 216.9GHz
to 236.5GHz divided into 13 spectral windows. The flux calibrators
were Titan and Ceres and the phase calibrators were J1733-1304 (for
G17 and G24) and J1709-3525 (for G345). The rms noise of the continuum
maps ranges between 0.2 and 1.0mJy/beam.
XCLASS LTE spectral modeler was used.
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------------
18 22 26.87 -13 30 17.2 G17.64+0.16 = IRAS 18196-1331
18 36 12. -07 12 11. G24.78+0.08 = GAL 024.78+00.08
16 59 42.26 -40 03 45.2 G345.49+1.47 = IRAS 16562-3959
------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 148 62 List of fits files
fits/* . 62 Individual fits files
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 32 I3 --- Nz ? Number of pixels along Z-axis
34- 59 A26 "datime" Obs.date Observation date
61- 67 F7.3 GHz Freq ? Observed frequency or lower value of
observed frequency for the datacubes
69- 75 F7.3 GHz BFreq ? Upper value of observed frequency for
the datacubes
77- 83 I7 Hz dFreq ? Frequency resolution for the datacubes
85- 91 I7 Kibyte size Size of FITS file
93-112 A20 --- FileName Name of FITS file, in subdirectory fits
114-148 A35 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Veronica Allen, veronica.a.allen(at)nasa.gov
(End) Patricia Vannier [CDS] 28-Jan-2020