J/ApJ/899/145 Sulfur isotopes in SFR with 12m ARO and 30m IRAM (Yu+, 2020)
Galactic Interstellar Sulfur Isotopes: A Radial 32S/34S gradient ?
Yu H.Z., Zhang J.S., Henkel C., Yan Y.T., Liu W., Tang X.D., Langer N.,
Luan T.C., Chen J.L., Wang Y.X., Deng G.G., Zou Y.P.
<Astrophys. J., 899, 145 (2020)>
=2020ApJ...899..145Y 2020ApJ...899..145Y
ADC_Keywords: Interstellar medium; Star Forming Region; Abundances;
Molecular data; Photometry, millimetric/submm
Keywords: Interstellar medium ; Stellar nucleosynthesis ; Abundance ratios ;
Radio astronomy ; Stellar abundances ; Galaxy chemical evolution ;
Interstellar molecules ; Milky Way Galaxy
Abstract:
We present observations of 12C32S, 12C34S, 13C32S, and 12C33S J=2-1
lines toward a large sample of massive star-forming regions by using
the Arizona Radio Observatory 12m telescope and the IRAM 30m. Taking
new measurements of the carbon 12C/13C ratio, the 32S/34S isotope
ratio was determined from the integrated 13C32S/12C34S line intensity
ratios for our sample. Our analysis shows a 32S/34S gradient from the
inner Galaxy out to a galactocentric distance of 12kpc. An unweighted
least-squares fit to our data yields
32S/34S=(1.56±0.17)DGC+(6.75±1.22) with a correlation
coefficient of 0.77. Errors represent 1σ standard deviations.
Testing this result by (a) excluding the Galactic center region, (b)
excluding all sources with C34S opacities >0.25, (c) combining our
data and old data from previous study, and (d) using different sets of
carbon isotope ratios leads to the conclusion that the observed
32S/34S gradient is not an artifact but persists irrespective of the
choice of sample and carbon isotope data. A gradient with rising
32S/34S values as a function of galactocentric radius implies that the
solar system ratio should be larger than that of the local
interstellar medium. With the new carbon isotope ratios, we indeed
obtain a local 32S/34S isotope ratio about 10% below the solar system
one, as expected in the case of decreasing 32S/34S ratios with time
and increased amounts of stellar processing. However, taking older
carbon isotope ratios based on a lesser amount of data, such a
decrease is not seen. No systematic variation of 34S/33S ratios along
galactocentric distance was found. The average value is 5.9±1.5,
the error denoting the standard deviation of an individual
measurement.
Description:
The observations were performed in 2018 November and December using
the Arizona Radio Observatory (ARO) 12m telescope toward 95 massive
star-forming regions. A 3mm sideband separating (SBS) receiver was
employed covering Atacama Large Millimeter/submillimeter Array (ALMA)
band 3 (84-116GHz). The center frequencies were set at 97.980986,
96.412982, 92.494299, and 97.172086GHz for the CS, C34S, 13CS, and
C33S lines, respectively; the beam size was ∼63".
Six sources among our sample were also observed by the Institut de
radioastronomie millimetrique (IRAM) 30m with the Eight MIxer Receive
(EMIR) heterodyne receiver during June 2016. We applied the
{lmabda}∼3mm E090 band to observe the J=2-1 lines of the CS, C34S,
13CS, and C33S isotopologs. A fast Fourier transform spectrometer
(FTS) backend in the wideband mode was employed in our observations,
with a spectral resolution of 400kHz (∼0.6km/s at 96GHz).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 96 252 Observational parameters of CS and three of its
rare isotopologues measured by the ARO 12m
telescope
table2.dat 95 24 Observational parameters of CS and three of its
rare isotopologues measured by the IRAM 30m
telescope
table3.dat 71 67 Sulfur isotope ratios and CS, C34S and 13CS optical
depths
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See also:
J/A+A/305/960 : Interstellar S isotopes (Chin+, 1996)
J/A+A/308/573 : Ammonia on YSOs IRAS sources (Molinari+ 1996)
J/A+A/451/1125 : Rotational excitation of CS (Lique+, 2006)
J/ApJ/699/1153 : Kinematic distances GRS molecular clouds (Roman-Duval+, 2009)
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 NH3 (Wienen+, 2012)
J/ApJ/783/130 : Parallaxes of high mass star forming regions (Reid+, 2014)
J/ApJ/822/59 : BGPS. XIV. Molecular cloud clumps GBT obs. (Svoboda+, 2016)
J/A+A/606/A74 : IRC +10216 13.3GHz-18.5GHz spectrum (Zhang+, 2017)
J/ApJ/885/131 : ∼200 high-mass SFR plx & proper motion with VLBI (Reid+, 2019)
J/ApJ/877/154 : H2CO TMRT obs. of Galactic molecular clouds (Yan+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- ID Source identifier
15- 16 I2 h RAh [0/23] Hour of Right Ascension (J2000)
18- 19 I2 min RAm Minute of Right Ascension (J2000)
21- 25 F5.2 s RAs Second of Right Ascension (J2000)
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)
41- 46 A6 --- Species Molecular species identifier
48- 49 I2 min Time [8/88]? Integration time
51- 52 I2 mK RMS [3/43]? Root Mean Square noise value
54- 57 F4.2 km/s DelV [0.48/0.96]? Channel width
59- 63 F5.1 km/s VLSR [-72.9/110] Local Standard of Rest velocity
65- 68 F4.2 km/s e_VLSR [0/0.78] Uncertainty in LSR
70- 73 F4.1 km/s DelV0.5 [1.6/58.6] Linewidth; Full-Width at Half-Maximum
75- 78 F4.2 km/s e_DelV0.5 [0.0/1.39] Uncertainty in DelV0.5
80- 85 F6.2 K.km/s Int [0.07/107.25] Integrated line intensity
87- 90 F4.2 K.km/s e_Int [0.01/0.65] Uncertainty in Int
92- 96 F5.2 K Tmb [0.03/10.64] Peak beam brightness temperature
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- ID Source identifier
15- 16 I2 h RAh [2/19] Hour of Right Ascension (J2000)
18- 19 I2 min RAm Minute of Right Ascension (J2000)
21- 25 F5.2 s RAs Second of Right Ascension (J2000)
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- 45 A6 --- Species Molecular species identifier
47- 48 I2 min Time [9/38] Integration time
50- 51 I2 mK RMS [13/72] Root Mean Square noise value
53- 56 F4.2 km/s DelV [0.6/0.6] Channel width
58- 62 F5.1 km/s VLSR [-47.4/110] Local Standard of Rest velocity
64- 67 F4.2 km/s e_VLSR [0/0.84] Uncertainty in LSR
69- 73 F5.2 km/s DelV0.5 [2.06/10.7] Linewidth Full-Width at Half-Maximum
75- 78 F4.2 km/s e_DelV0.5 [0.0/2.21] Uncertainty in DelV0.5
80- 84 F5.2 K.km/s Int [0.48/96.13] Integrated line intensity
86- 89 F4.2 K.km/s e_Int [0.03/0.33] Uncertainty in Int
91- 95 F5.2 K Tmb [0.04/12.76] Peak beam brightness temperature
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- ID Source identifier
15- 19 F5.2 kpc DSun [0.42/11.1]? Distance from the Sun
21- 24 F4.1 kpc DGC [0/11.7]? Distance from the galactic center
26- 27 I2 --- 12C/13C [12/71]? The 12C/13C isotope ratio (1)
29- 30 I2 --- e_12C/13C [7/14]? Uncertainty in 12C/13C
32- 35 F4.1 --- tau12CS [0.3/11.5]? Estimated peak optical depth of
12CS (2)
37- 41 F5.3 --- tau13CS [0.004/0.271]? Estimated peak optical depth of
13CS (2)
43- 47 F5.3 --- tauC34S [0.009/0.627]? Estimated peak optical depth of
C34S (2)
49- 52 F4.1 --- 32S/34S [7.1/33.8] The 32S/34S isotope ratio (3)
54- 57 F4.1 --- e_32S/34S [3.4/11.3] Uncertainty in 32S/34S (3)
59- 62 F4.1 --- 34S/33S [1.7/10.5] The 34S/33S isotope ratio (3)
64- 66 F3.1 --- e_34S/33S [0.1/2.3] Uncertainty in 34S/33S (3)
68- 71 F4.1 K Tk [18.0/98]? Gas kinetic temperature
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Note (1): Calculated using equations (1) and (3), based on the recent
measurements by Yan+, 2019, J/ApJ/877/154; the applied
propagated error is σ=(1.12DGC(kpc)2+6.62)1/2.
Note (2): See Eqs. 6, 7 and 8.
Note (3): In cases where there are two rows of the same source the second
set is from the IRAM 30-m telescope and is intended for comparison
with the ARO 12-m data.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 22-Oct-2021