J/ApJS/268/56 Obs. of Gal. interstellar ratio ^18^O/^17^O. II. (Zou+, 2023) ================================================================================ A systematic observational study on Galactic interstellar ratio 18O/17O. II. C^18^O and C^17^O J=2-1 data analysis. Zou Y.P., Zhang J.S., Henkel C., Romano D., Liu W., Zheng Y.H., Yan Y.T., Chen J.L., Wang Y.X., Zhao J.Y. =2023ApJS..268...56Z ================================================================================ ADC_Keywords: Carbon monoxide; Molecular clouds; Milky Way; Interstellar medium Keywords: Interstellar molecules ; Radio source counts ; Isotopic abundances ; Galaxy chemical evolution Abstract: To investigate the relative amount of ejecta from high-mass versus intermediate-mass stars and to trace the chemical evolution of the Galaxy, we have performed a systematic study of Galactic interstellar ^18^O/^17^O ratios toward a sample of 421 molecular clouds with IRAM-30m and the 10m Submillimeter Telescope, covering a galactocentric distance range of ~1-22kpc. The results presented in this paper are based on the J=2-1 transition and encompass 364 sources showing both C^18^O and C^17^O detections. The previously suggested ^18^O/^17^O gradient is confirmed. For the 41 sources detected with both facilities, good agreement is obtained. A correlation of the ^18^O/^17^O ratios with heliocentric distance is not found, indicating that beam dilution and linear beam sizes are not relevant. For the subsample of IRAM 30m high-mass star-forming regions with accurate parallax distances, an unweighted fit gives ^18^O/^17^O=(0.12+/-0.02)RGC+(2.38+/-0.13) with a correlation coefficient of R=0.67. While the slope is consistent with our J=1-0 measurement, the ratios are systematically lower. This should be caused by larger optical depths of C^18^O 2-1 lines with respect to the corresponding 1-0 transitions, which is supported by RADEX calculations and the fact that C18O/C17O is positively correlated with ^13^CO/C^18^O. When we consider that optical depth effects with C^18^O(J=2-1) typically reach an optical depth of ~0.5, the corrected ^18^O/^17^O ratios from the J=1-0 and J=2-1 lines are consistent. A good numerical fit to the data is provided by the MWG-12 model, which includes both rotating stars and novae. Description: Our observations of the C^18^O and C^17^O J=2-1 lines were carried out from 2017 January 11 until January 17, using the IRAM 30m at the Pico Veleta Observatory (Granada, Spain). The center frequencies were set at 219.560354 and 224.714187GHz for the C^18^O and C^17^O lines, respectively. With the IRAM 30m, we observed 103 sources of our sample. The observational parameters are summarized in Table 1. Our Submillimeter Telescope (SMT) 10m (on Mount Graham, Arizona, USA) observations of J=2-1 lines were performed remotely in 2016 May and June, 2018 January and November, 2019 December, 2020 June, July, and November, and in 2021 January and February with a beam size of ~29". Table 1 presents the observational parameters of the SMT 10m results for the sample of 380 sources, including the 62 sources that were observed by both the IRAM 30m and the SMT 10m telescopes. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 125 966 Observational parameters and ^18^O/^17^O isotope ratios toward 420 molecular clouds table2.dat 122 164 A comparison of IRAM 30m and SMT 10m results for the 41 common sources with C18O and C17O detections -------------------------------------------------------------------------------- See also: J/A+AS/80/149 : IRAS Sources behind the Solar circle (Wouterloot+ 1989) J/A+A/430/549 : C^18^O/C^17^O near rho Oph (Wouterloot+, 2005) J/ApJ/724/748 : Galactic anticenter PNe and oxygen abundance (Henry+, 2010) J/ApJ/741/110 : The BGPS. VII. Massive star-forming regions (Dunham+, 2011) J/MNRAS/418/1689 : Red MSX water maser and ammonia emissions (Urquhart+, 2011) J/A+A/544/A146 : ATLASGAL cold high-mass clumps with NH_3_ (Wienen+, 2012) J/ApJ/764/61 : H2O maser & NH_3_ survey of GLIMPSE EGOs (Cyganowski+, 2013) J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014) J/ApJS/219/28 : C^18^O/C^17^O ratios in the Galactic center (Zhang+, 2015) J/ApJ/822/59 : BGPS. XIV. Molecular cloud clumps GBT obs. (Svoboda+, 2016) J/ApJS/237/13 : Models & yields of massive stars (Limongi+, 2018) J/MNRAS/490/2779 : Dust clumps assoc. with methanol masers (Billington+, 2019) J/ApJ/885/131 : High-mass SFR plx & proper motion with VLBI (Reid+, 2019) J/ApJ/877/154 : H_2_CO TMRT obs. of Galactic molecular clouds (Yan+, 2019) J/A+A/642/A222 : CS isotopes towards Galactic centre clouds (Humire+, 2020) J/ApJ/899/145 : Sulfur isotopes in SFR with 12m ARO and 30m IRAM (Yu+, 2020) J/ApJS/249/6 : Galactic interstellar ratio ^18^O/^17^O. I. (Zhang+, 2020) J/ApJS/257/39 : NH3 isotope ratios of Galactic disk sources (Chen+, 2021) J/A+A/649/A21 : ATLASGAL deuteration of ammonia (Wienen+, 2021) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 13 A13 --- Name Source Name (GBBB.bb+LL.ll or WB89 NNNA) 14 A1 --- m_Name Component on source name for G123.06-06.30 16- 17 I2 h RAh Hour of Right Ascension (J2000) 19- 20 I2 min RAm Minute of Right Ascension (J2000) 22- 25 F4.1 s RAs Second of Right Ascension (J2000) 27- 27 A1 --- DE- Sign of the Declination (J2000) 28- 29 I2 deg DEd Degree of Declination (J2000) 31- 32 I2 arcmin DEm Arcminute of Declination (J2000) 34- 38 F5.2 arcsec DEs Arcsecond of Declination (J2000) 40- 44 F5.2 kpc RGC [0.3/22.6]? Galactocentric distance 46- 50 F5.2 kpc Dist [0.1/20.5]? Heliocentric distance 52- 55 A4 --- Tel Telescope used ("IRAM" or "SMT") 57- 60 A4 --- Line Line ("C18O" or "C17O") 62- 64 I3 mK rms [9/750]? Root-mean-square value; in units of Tmb 66- 73 F8.3 km/s Vpeak [-102/121]? Velocity of the peak Tmb 75- 79 F5.3 km/s e_Vpeak [0/0.5]? Uncertainty in Vpeak 81- 86 F6.3 km/s FWHM [0.6/18.8]? FWHM 88- 92 F5.3 km/s e_FWHM [0.001/1.1]? Uncertainty in FWHM 94-100 F7.3 K.km/s Tmbdv [0.06/181]? Integrated line intensity 102-106 F5.3 K.km/s e_Tmbdv [0.008/2.7]? Uncertainty in Tmbdv 108-113 F6.3 K Tpeak [0.03/21.7]? Antenna temperature at Tmb peak 115-119 F5.3 --- Rcorr [1.2/9.6]? Frequency-corrected abundance ratio 121-125 F5.3 --- e_Rcorr [0.008/2]? Uncertainty in Rcorr -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 13 A13 --- Name Source Name (GBBB.bb+LL.ll or WB89 NNN) 14 A1 --- m_Name Component on source name for G123.06-06.30 16- 17 I2 h RAh Hour of Right Ascension (J2000) 19- 20 I2 min RAm Minute of Right Ascension (J2000) 22- 25 F4.1 s RAs Second of Right Ascension (J2000) 27- 28 I2 deg DEd Degree of Declination (J2000) 30- 31 I2 arcmin DEm Arcminute of Declination (J2000) 33- 37 F5.2 arcsec DEs Arcsecond of Declination (J2000) 39- 43 F5.2 kpc RGC [6.3/13.7] Galactocentric distance 45- 49 F5.2 kpc Dist [0.6/10.8] Heliocentric distance 51- 54 A4 --- Tel Telescope used ("IRAM" or "SMT") 56- 59 A4 --- Line Line ("C18O" or "C17O") 61- 63 I3 mK rms [22/186]? Root-mean-square value; in units of Tmb 65- 71 F7.3 km/s Vpeak [-73/67.1]? Velocity of the peak Tmb 73- 77 F5.3 km/s e_Vpeak [0/0.5]? Uncertainty in Vpeak 79- 83 F5.3 km/s FWHM [0.9/9.3]? FWHM 85- 89 F5.3 km/s e_FWHM [0.001/0.8]? Uncertainty in FWHM 91- 97 F7.3 K.km/s Tmbdv [0.8/161.1]? Integrated line intensity 99-103 F5.3 K.km/s e_Tmbdv [0.008/1.3]? Uncertainty in Tmbdv 105-110 F6.3 K Tpeak [0.15/20.4]? Antenna temperature at Tmb peak 112-116 F5.3 --- Rcorr [2.6/4.4]? Frequency-corrected abundance ratio 118-122 F5.3 --- e_Rcorr [0.018/1]? Uncertainty in Rcorr -------------------------------------------------------------------------------- History: From electronic version of the journal References: Zhang et al. Paper I. 2020ApJS..249....6Z Cat. J/ApJS/249/6 ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Jan-2024