J/ApJ/783/77 Line lists of transitions for interstellar urea (Remijan+, 2014) ================================================================================ Observational results of a multi-telescope campaign in search of interstellar urea [(NH_2_)_2_CO]. Remijan A.J., Snyder L.E., McGuire B.A., Kuo H.-L., Looney L.W., Friedel D.N., Golubiatnikov G.Y., Lovas F.J., Ilyushin V.V., Alekseev E.A., Dyubko S.F., McCall B.J., Hollis J.M. =2014ApJ...783...77R (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Interstellar medium ; Atomic physics Keywords: astrochemistry - ISM: clouds - ISM: individual (Sagittarius B2(N)) - ISM: molecules Abstract: In this paper, we present the results of an observational search for gas phase urea [(NH_2_)_2_CO] observed toward the Sgr B2(N-LMH) region. We show data covering urea transitions from ~100GHz to 250GHz from five different observational facilities: the Berkeley-Illinois-Maryland-Association (BIMA) Array, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the NRAO 12m telescope, the IRAM 30m telescope, and the Swedish-ESO Submillimeter Telescope (SEST). The results show that the features ascribed to urea can be reproduced across the entire observed bandwidth and all facilities by best-fit column density, temperature, and source size parameters which vary by less than a factor of two between observations merely by adjusting for telescope-specific parameters. Interferometric observations show that the emission arising from these transitions is cospatial and compact, consistent with the derived source sizes and emission from a single species. Despite this evidence, the spectral complexity of both (NH_2_)_2_ CO and of Sgr B2(N) makes the definitive identification of this molecule challenging. We present observational spectra, laboratory data, and models, and discuss our results in the context of a possible molecular detection of urea. Description: The first measurements of the microwave spectra of urea were made from 5GHz to 50GHz using a heated waveguide cell (Brown et al., 1975JMoSp..58..445B). Further measurements were reported by Kasten & Dreizler (1986ZNatA..41.1173K) and Kretschmer et al. (1996MolPh..87.1159K). New spectroscopic measurements were made at NIST over the frequency range from 59GHz to 114GHz. A total of 38 rotational transitions was measured. Later, the Kharkov group carried out higher frequency measurements. Using a heated quartz absorption cell utilizing an automated synthesizer-based spectrometer (Ilyushin et al., 2005JMoSp.231...15I), the Kharkov group provided 75 new measurements between 78GHz and 240GHz. The urea lines for which we searched were calculated using the millimeter-wave data discussed above, as well as the hyperfine-free data from the existing literature cited earlier. As an aid to further interstellar searches for urea transitions, we provide a complete list of predicted rotational lines of urea available in Table6 covering the frequency range of 1GHz to 600GHz. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table6.dat 72 4120 Measured and calculated frequencies and associated spectroscopic constants of urea [(NH_2_)_2_CO] -------------------------------------------------------------------------------- See also: http://www.cv.nrao.edu/php/splat/ : Splatalogue database for astronomical spectroscopy Byte-by-byte Description of file: table6.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 F10.3 MHz Freq1 [1111.6/599859.1] Calculated Frequency 12- 15 I4 MHz e_Freq1 [0/4255] The 2{sigma} uncertainty in Freq (1) 17- 26 F10.3 MHz Freq2 [5816.6/232837]? Measured Frequency 28- 30 I3 MHz e_Freq2 [1/500]? The 2{sigma} uncertainty in MFreq (1) 32- 38 F7.3 cm-1 Elow [0/604.771] Lower state energy level 40- 42 I3 --- J1 [1/40] J quantum number of the upper state (J') 44- 45 I2 --- Ka1 [0/40] K_a_ quantum number of the upper state (K'_a_) 47- 48 I2 --- Kc1 [0/40] K_c_ quantum number of the upper state (K'_c_) 50- 52 I3 --- J0 [0/40] J quantum number of the lower state (J'') 54- 55 I2 --- Ka0 [0/39] K_a_ quantum number of the lower state (K''_a_) 57- 58 I2 --- Kc0 [0/40] K_c_ quantum number of the lower state (K''_c_) 60- 66 F7.4 --- Sij [0/39.5] Transition line strength 68- 72 A5 --- Ref Reference (2) -------------------------------------------------------------------------------- Note (1): In units of the last digit and are of type A (coverage factor k=2) (Taylor & Kuyatt 1994, Guidelines for Evaluation and Expressing the Uncertainty of NIST Measurement Results (NIST Tech. Note 1297) (Washington, DC: GPO)). Note (2): Reference codes are defined as follows: Bro75 = Brown et al. (1975JMoSp..58..445B); Gol01 = NIST spectroscopic measurement; Ily05 = Ilyushin et al. (2005JMoSp.231...15I). This flag was "Ily03" in the MRT original table of the paper and was corrected in Ily05 at CDS. Kas86 = Kasten & Dreizler (1986ZNatA..41.1173K); Kre96 = Kretschmer et al. (1996MolPh..87.1159K). -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 15-Apr-2016