J/ApJ/770/L13 Detection of CH_3_COOCH_3_ in Orion (Tercero+, 2013) ================================================================================ Discovery of methyl acetate and gauche ethyl formate in Orion. Tercero B., Kleiner I., Cernicharo J., Nguyen H.V.L., Lopez A., Munoz Caro G.M. =2013ApJ...770L..13T ================================================================================ ADC_Keywords: Atomic physics ; Molecular clouds ; Radio lines Keywords: ISM: abundances; ISM: individual: Orion KL; ISM: molecules; line: identification; molecular data Abstract: We report on the discovery of methyl acetate, CH_3_COOCH_3_, through the detection of a large number of rotational lines from each one of the spin states of the molecule: AA species (A_1_ or A_2_), EA species (E_1_), AE species (E_2_), and EE species (E_3_ or E_4_). We also report, for the first time in space, the detection of the gauche conformer of ethyl formate, CH_3_CH_2_OCOH, in the same source. The trans conformer is also detected for the first time outside the Galactic center source SgrB2. From the derived velocity of the emission of methyl acetate, we conclude that it arises mainly from the compact ridge region with a total column density of (4.2+/-0.5)x10^15^/cm2. The derived rotational temperature is 150K. The column density for each conformer of ethyl formate, trans and gauche, is (4.5+/-1.0)x10^14^/cm2. Their abundance ratio indicates a kinetic temperature of 135K for the emitting gas and suggests that gas-phase reactions could participate efficiently in the formation of both conformers in addition to cold ice mantle reactions on the surface of dust grains. Description: The observations were carried out using the IRAM 30m radiotelescope, covering the following frequency ranges: 80-115.5GHz, 130-178GHz, and 197-281GHz, during several periods (see Tercero et al. 2010A&A...517A..96T). System temperatures were in the range 200-800K for the 1.3mm receivers, 200-500K for the 2mm receivers, and 100-350K for the 3mm receivers, depending on the particular frequency, weather conditions, and source elevation. The observations were carried out during September 2004 (3mm and 1.3mm windows), March 2005 (full 2mm window), April 2005 (completion of 3mm and 1.3mm windows), and January 2007 (maps and pointed observations at particular positions). We pointed the observations toward IRc2 at RAJ2000=5:35:14.5, DEJ2000=-5:22:30.0. Objects: ------------------------------------------------- RA (ICRS) DE Designation(s) ------------------------------------------------- 05 35 14.5 -05 22 30 IRc2 = NAME KL IRC2 ------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 129 730 Detected lines of CH_3_COOCH_3_ at IRAM (30m) -------------------------------------------------------------------------------- See also: J/A+A/572/A44 : Vibrationally excited vinyl cyanide in Orion-KL (Lopez+, 2014) J/ApJ/768/81 : Ethyl cyanide, CH_3_CH_2_CN, vibrational states (Daly+, 2013) J/A+A/559/A51 : HC_3_N in Orion KL (Esplugues+, 2013) J/A+A/548/A71 : Spectroscopy and ISM detection of formamide (Motiyenko+, 2012) J/A+A/538/A119 : ^18^O-methyl formate (HCO^18^OCH_3_) spectrum (Tercero+ 2012) J/A+A/532/A32 : HCOOCH3 map of Orion-KL (Favre+, 2011) J/ApJ/714/1120 : Rotational spectrum and DCOOCH_3_ in Orion (Margules+, 2010) J/A+A/500/1109 : Rotational spectrum of HCOO^13^CH_3_ (Carvajal+, 2009) J/A+A/493/565 : Deuterated and ^15^N ethyl cyanides (Margules+, 2009) J/A+A/473/177 : A search for pre-biotic molecules (Wirstrom+, 2007) J/A+A/466/255 : Isotopic ethyl cyanide (Demyk+, 2007) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- J [6/30] J quantum number of upper level 4- 6 I3 --- Ka [-17/18] K_a_ quantum number of upper level 8- 9 I2 --- Kc [0/28] K_c_ quantum number of upper level 11- 12 I2 --- p [-1/1]? Parity of upper level 14- 15 I2 --- J' [5/30] J' quantum number of lower level 17- 19 I3 --- K'a [-16/17] K'_a_ quantum number of lower level 21- 22 I2 --- K'c [0/29] K'_c_ quantum number of lower level 24- 25 I2 --- p' [-1/1]? Parity of lower level 27- 28 A2 --- State Molecule symmetry state: AA (A_1_/A_2_), EA (E_1_), AE (E_2_), E3 or E4 30- 39 F10.3 MHz Flab [82779/277629] Predicted lab frequency 41- 45 F5.3 MHz e_Flab [0.006/3.4] Error in Flab 47- 51 F5.1 K Eu [15.5/217.4] Upper level energy 53- 57 F5.2 D2 Sijmu2 [3.2/71.8] Line strength S_ij_{mu}^2^ 59- 66 F8.1 MHz Fobs [82780/277629] Observed frequency assuming a v_LSR_ of 8km/s 68 A1 --- f_Fobs [d] d = blended with previous line 70- 73 F4.2 K Tmb [0.02/0.7]? Mean beam temperature 75-129 A55 --- Blend Blended line identifier (U=unknown) -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 13-Jan-2015