J/ApJ/724/994 Cyano- to methanol and ammonia observations (Braakman+, 2010)
Search for interstellar methoxyacetonitrile and cyanoethanol: insights into
coupling of cyano- to methanol and ammonia chemistry.
Braakman R., Belloche A., Blake G.A., Menten K.M.
<Astrophys. J., 724, 994-1005 (2010)>
=2010ApJ...724..994B 2010ApJ...724..994B
ADC_Keywords: Interstellar medium ; Molecular clouds ; Atomic physics ;
Spectra, millimetric/submm ; Radio lines
Keywords: astrochemistry - evolution - ISM: molecules; stars: protostars
Abstract:
As part of an effort to study gas-grain chemical models in
star-forming regions as they relate to molecules containing cyanide
(-C≡N) groups, we present here a search for the molecules
2-cyanoethanol (OHCH2CH2CN) and methoxyacetonitrile
(CH3OCH2CN) in the galactic center region SgrB2. These species are
structural isomers of each other and are targeted to investigate the
cross-coupling of pathways emanating from the photolysis products of
methanol and ammonia with pathways involving cyano-containing
molecules. Methanol and ammonia ices are two of the main repositories
of the elements C, O, and N in cold clouds and understanding their
link to cyanide chemistry could give important insights into prebiotic
molecular evolution. Neither species was positively detected, but the
upper limits we determined allow comparison to the general patterns
gleaned from chemical models. Our results indicate the need for an
expansion of the model networks to better deal with cyano-chemistry,
in particular with respect to pathways including products of methanol
photolysis. In addition to these results, the two main observational
routes for detecting new interstellar molecules are discussed.
Description:
The two hot core regions Sgr B2(N) and Sgr B2(M) were observed with
the IRAM 30m telescope on Pico Valeta, Spain, over the course of a
year, in 2004 January, 2004 September, and 2005 January. A complete
spectral survey of the 3mm atmospheric window from 80 to 116GHz was
carried out, along with associated surveys in the 1.3mm window between
201.8 and 204.6GHz and between 205.0 and 217.7GHz. Selected spectra in
the 2mm window and 1mm window between 219 and 268GHz were also
obtained. The coordinates of the observed position for Sgr B2(N) are
(J2000)=17:47:20.0-28:22:19.0 with a systemic velocity Vlsr=64km/s
and (J2000)=17:47:20.4-28:23:07.0 with a systemic velocity
Vlsr=62km/s for Sgr B2(M). Additional details about the
observational setup and data reduction can be found in Belloche et al.
(2008, Cat. J/A+A/482/179).
Objects:
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RA (2000) DE Designation(s)
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17 47 20.0 -28 22 19 Sgr B2(N) = NAME SGR B2 (NORTH)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table6.dat 149 554 Transitions of the gauche-conformer of
methoxyacetonitrile [CH3OCH2CN] observed with
the IRAM 30m telescope toward Sgr B2(N)
table7.dat 137 746 Transitions of the gauche-conformer of
2-cyanoethanol [OHCH2CH2CN] observed with
the IRAM 30m telescope toward Sgr B2(N)
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See also:
B/iram : IRAM Observation Logs 1991-2010 (IRAM 1991-2012)
V/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002)
J/A+A/482/179 : Interferometric study of SgrB2(N) (Belloche+, 2008)
J/ApJS/158/188 : Detection of glycolaldehyde toward Sgr B2 (Widicus+, 2005)
J/ApJS/155/577 : H2O masers in W49 North and Sagittarius B2 (McGrath+, 2004)
J/ApJS/117/427 : Sgr B2 spectral survey (Nummelin+, 1998)
J/AZh/71/37 : Thermal Methanol from 33 Clouds at 48 GHz (Slysh+, 1994)
Byte-by-byte Description of file: table[67].dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq Observed transition number (1)
6- 28 A23 --- Trans Transition (2)
30- 39 F10.3 MHz Freq Observed frequency
41- 44 I4 kHz e_Freq Uncertainty in Freq
46- 49 I4 K Elow Lower energy level in temperature units (El/kB)
51- 55 F5.1 D2 Smu2 The Sµ2 coefficient
57- 59 I3 mK sigma Calculated rms noise level in TMB scale
61-149 A89 --- Comm Additional comments (3)
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Note (1): Associated with a modeled line stronger than 20mK.
Note (2): Transitions marked with a * are double with a frequency difference
less than 0.1MHz. The quantum numbers of the second one are not shown.
Note (3): Comments in all CAPS indicate features that suffer less from blending.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Aug-2012