J/ApJ/871/251 ALMA obs. of ethyl formate toward Orion KL (Peng+, 2019) ================================================================================ ALMA observations of ethyl formate toward Orion KL. Peng Y., Rivilla V.M., Zhang Li, Ge J.X., Zhou B. =2019ApJ...871..251P ================================================================================ ADC_Keywords: Interstellar medium; Molecular data; Radio lines Keywords: ISM: abundances; ISM: individual objects (Orion KL); ISM: molecules; radio lines: ISM; stars: formation Abstract: Orion KL is one of the prime templates of astrochemical and prebiotic chemical studies. We wish to explore more organic molecules with increasing complexity in this region. In particular, we have searched for one of the most complex organic molecules detected in space so far, ethyl formate (C_2_H_5_OCHO). This species is the next step in chemical complexity after the simplest member of esters (methyl formate, CH_3_OCHO). The mechanisms leading to its formation are still poorly known. We have used high angular resolution (~1.5") ALMA observations covering a large bandwidth from 214 to 247GHz. We have detected 82 unblended lines of C_2_H_5_OCHO (49 and 33 of the trans- and gauche- conformers, respectively). The line images showed that C2H5OCHO arises mainly from the compact ridge and the hot core-southwest regions. The derived rotational temperatures and column densities are 122+/-34K, (0.9+/-0.3)x10^16^cm^-2^ for the hot core-SW, and 103+/-13K, (0.6+/-0.3)x10^16^cm^-2^ for the compact ridge. The comparison of spatial distribution and abundance ratios with chemically related molecules (methyl formate, ethanol, and formic acid) indicates that C_2_H_5_OCHO is likely formed on the surface of dust grains by addition of CH_3_ to functional-group radicals (CH_2_OCHO) derived from methyl formate (CH_3_OCHO). Description: We used data from the ALMA science verification program. The observations were carried out with 16 antennas of 12m in 2012 January. The baseline lengths range from 17 to 265m. A total of 20 spectral windows of 1.875GHz completely cover a frequency range from 214 to 247GHz. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 05 35 14.35 -05 22 35.0 Orion-KL = NAME Orion-KL ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 118 80 Selected unblended transitions of the Trans and Gauche conformers of ethyl formate (C_2_H_5_OCHO) observed with the ALMA table2.dat 45 470 Selected unblended transitions of methyl formate (CH_3_OCHO) observed with the ALMA table3.dat 56 205 Transitions of the Trans and Gauche conformers of ethanol (C_2_H_5_OH) observed with the ALMA -------------------------------------------------------------------------------- See also: J/ApJS/156/127 : 350{mu}m molecular line survey of Orion KL (Comito+, 2005) J/ApJS/181/433 : Spectrum of ethyl formate (Medvedev+, 2009) J/A+A/532/A32 : HCOOCH3 map of Orion-KL (Favre+, 2011) J/ApJ/770/L13 : Detection of CH_3_COOCH_3_ in Orion (Tercero+, 2013) J/ApJ/779/119 : HCOOCH_2_D detection in Orion KL (Coudert+, 2013) J/ApJ/784/L7 : CH_3_CH_2_SH detection in Orion KL (Kolesnikova+, 2014) J/ApJS/215/25 : Methyl formate (HCOOCH_3_) observations (Favre+, 2014) J/A+A/581/A71 : Orion-KL substructure at 1.3mm (Feng+, 2015) J/A+A/581/A48 : 1.3cm line survey toward Orion KL (Gong+, 2015) J/ApJ/803/97 : Transitions of methyl formate toward Orion KL (Sakai+, 2015) J/AJ/154/152 : CARMA 1 cm spectral line survey of Orion-KL (Friedel+, 2017) J/A+A/604/A32 : Orion BN-KL ALMA view (Pagani+, 2017) J/A+A/598/A59 : G31.41+0.31 SMA spectra (Rivilla+, 2017) J/A+A/605/A76 : Spectrum of Orion KL between 41.5 and 50GHz (Rizzo+, 2017) J/A+A/620/A80 : An incipient hot corino in B1b-S (Marcelino+, 2018) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 1 A1 --- C [GT] Corresponding conformer (G=gauche or T=trans) 3- 13 F11.7 GHz Freq [213.8/246.2] Rest Frequency 15- 33 A19 --- Quant Transition quantum numbers 35- 40 F6.2 D2 Sij [0.3/157.2] Strength, S_ij_{mu}^2^; in Debye^2^ units 42- 44 I3 K Eu [152/411] Upper energy 46- 47 A2 --- flag1 Detection flag, hot core-SW (G1) 49- 51 F3.1 km/s vLSR1 [3.8/8.1]? Radial velocity, hot core-SW, relative to LSR 53- 55 F3.1 km/s e_vLSR1 [0.1/0.4]? Uncertainty in vLSR1 57- 59 F3.1 km/s dV1 [1.5/4.2]? Linewidth, hot core-SW 61- 63 F3.1 km/s e_dV1 [0.1/0.8]? Uncertainty in dV1 65- 68 F4.2 K Ip1 [0.16/1.76]? Line temperature, hot core-SW 70- 73 F4.2 K e_Ip1 [0.03/0.6]? Uncertainty in Ip1 75- 76 A2 --- l_sig1 [<= ] Limit flag on {sigma}1 77- 78 I2 --- sig1 [3/37]? Detection level, hot core-SW; in units of {sigma}0 80- 81 A2 --- flag2 Detection flag, compact ridge (G1) 83- 85 F3.1 km/s vLSR2 [6.2/8.2]? Radial velocity, compact ridge, relative to LSR 87- 89 F3.1 km/s e_vLSR2 [0.1/1.3]? Uncertainty in vLSR2 91- 93 F3.1 km/s dV2 [1.3/2.8]? Linewidth, compact ridge 95- 97 F3.1 km/s e_dV2 [0.1/0.9]? Uncertainty in dV2 99-103 F5.3 K Ip2 [0.128/1.73]? Line temperature, compact ridge 105-109 F5.3 K e_Ip2 [0.006/0.11]? Uncertainty in Ip2 111-112 I2 --- sig2 [4/24]? Detection level, compact ridge; in units of {sigma}0 114-118 F5.3 K sig0 [0.007/0.09] 1{sigma} spectrum uncertainty -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 F9.5 GHz Freq [214.2/246.7] Rest Frequency 11- 30 A20 --- Quant Transition quantum numbers 32- 36 F5.2 D2 Sij [0.02/58.17] Strength, S_ij_{mu}^2^ in Debye^2^ 38- 40 I3 K Eu [23/797] Upper energy, K 42- 43 A2 --- hotcore Detection, hot core-SW (G1) 45- 45 A1 --- ridge Detection, ridge (G1) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 1 A1 --- C [GT] Corresponding conformer (G=gauche or T=trans) 3- 11 F9.5 GHz Freq [213.7/246.5] Rest Frequency 13- 41 A29 --- Quant Transition quantum numbers 43- 47 F5.2 D2 Sij [0.32/50.23] Strength, S_ij_{mu}^2^ in Debye^2^ 49- 51 I3 K Eu [24/672] Upper energy 53- 53 A1 --- hotcore Detection, hot core-SW (G1) 55- 56 A2 --- ridge Detection, ridge (G1) -------------------------------------------------------------------------------- Global notes: Note (G1): Detection flags as follows: Y = Yes, detected B = Yes, blended; PB = Yes, partial blend; ND = Not detected. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 30-Jul-2020