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J/ApJ/806/199 RRL and continuum data of 21 Galactic H II regions (Balser+, 2015)

Azimuthal metallicity structure in the Milky Way disk. Balser D.S., Wenger T.V., Anderson L.D., Bania T.M. <Astrophys. J., 806, 199 (2015)> =2015ApJ...806..199B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; H II regions ; Radio lines ; Radio continuum Keywords: Galaxy: abundances - H II regions - radio lines: ISM Abstract: Elemental abundance patterns in the Galactic disk constrain theories of the formation and evolution of the Milky Way. H II region abundances are the result of billions of years of chemical evolution. We made radio recombination line and continuum measurements of 21 H II regions located between Galactic azimuth Az=90°-130°, a previously unexplored region. We derive the plasma electron temperatures using the line-to-continuum ratios and use them as proxies for the nebular [O/H] abundances, because in thermal equilibrium the abundance of the coolants (O, N, and other heavy elements) in the ionized gas sets the electron temperature, with high abundances producing low temperatures. Combining these data with our previous work produces a sample of 90 H II regions with high-quality electron temperature determinations. We derive kinematic distances in a self-consistent way for the entire sample. The radial gradient in [O/H] is -0.082±0.014 dex/kpc for Az=90°-130°, about a factor of 2 higher than the average value between Az=0°-60°. Monte Carlo simulations show that the azimuthal structure we reported for Az=0°-60° is not significant because kinematic distance uncertainties can be as high as 50% in this region. Nonetheless, the flatter radial gradients between Az=0°-60° compared with Az=90°-130° are significant within the uncertainty. We suggest that this may be due to radial mixing from the Galactic Bar whose major axis is aligned toward Az∼30°. Description: We select 21 of the best continuum sources based on the following criteria. (1) Sources having a continuum intensity signal-to-noise ratio greater than 10. (2) Since we are probing trans-Galactic paths, source confusion can be a significant problem. We chose sources where the H II region was either isolated or where any blending of components could be well-fit by Gaussian profiles. (3) We select sources with either flat radio recombination line (RRL) spectral baselines or with baseline structure that could be well-fit by a low order polynomial function. (4) Since we seek to explore metallicity structure, we chose sources that span a wide range of Galactic radii over the specified azimuth range. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 64 28 Radio Recombination Line Parameters of Galactic H II Regions table2.dat 86 21 Radio Continuum Parameters of Galactic H II Regions table3.dat 131 221 H II Region Properties
See also: J/ApJ/653/1226 : Physical properties of galactic HII regions (Quireza+, 2006) J/ApJ/738/27 : Galactic HII regions RRL and continuum data (Balser+, 2011) J/ApJS/194/32 : The HII Region Discovery Survey (HRDS). II. (Anderson+, 2011) J/ApJ/754/62 : HRDS III. HII region kinematic distances (Anderson+, 2012) J/ApJS/212/1 : The WISE catalog of Galactic HII regions (Anderson+, 2014) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name Source name 16- 17 A2 --- El [H C He] Element name 19- 24 F6.2 mK TL H (or He) radio recombination line (RRL) intensity 26- 29 F4.2 mK e_TL Uncertainty in TL 31- 35 F5.2 km/s DelV H (or He) RRL FWHM line width 37- 40 F4.2 km/s e_DelV Uncertainty in DelV 42- 47 F6.2 km/s VLSR Local Standard of Rest velocity 49- 52 F4.2 km/s e_VLSR Uncertainty in VLSR 54- 57 F4.1 h Tint ? Total integration time 59- 62 F4.2 mK rms ? rms spectral noise 64 A1 --- QF [BCD-] Quality factor (G1)
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name Source name 16- 21 F6.1 mK TC-RA Continuum peak intensity along Right Ascension 23- 26 F4.2 mK e_TC-RA Uncertainty in TC-RA 28- 31 F4.2 arcmin Theta-RA FWHM angular width (Θ) along Right Ascension 33- 37 F5.3 arcmin e_Theta-RA Uncertainty in Theta-RA 39- 44 F6.1 mK TC-DE Continuum peak intensity along Declination 46- 50 F5.2 mK e_TC-DE Uncertainty in TC-DE 52- 55 F4.2 arcmin Theta-DE FWHM angular width (Θ) along Declination 57- 61 F5.3 arcmin e_Theta-DE Uncertainty in Theta-DE 63- 68 F6.1 mK TC Average continuum peak intensity 70- 73 F4.2 mK e_TC Uncertainty in TC 75- 78 F4.2 arcmin Theta Average FWHM angular width (Θ) 80- 84 F5.3 arcmin e_Theta Uncertainty in Theta 86 A1 --- QF [ABC] Quality factor (G1)
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Name Source name 16 A1 --- n_Name [b] Note on Name (1) 18- 24 F7.3 deg GLON Galactic longitude 26- 32 F7.3 deg GLAT Galactic latitude 34- 37 F4.1 kpc Dsun1 ? Distance from the Sun (Kinematic-IAU) (3) 39- 43 F5.2 kpc e_Dsun1 ? Uncertainty in Dsun1 (Kinematic-IAU) (3) 45- 49 F5.1 deg Az1 ? Galactic azimuth (Kinematic-IAU) (3) 51- 54 F4.1 kpc Rgal1 ? Galactic radius (Kinematic-IAU) (3) 56- 59 F4.1 kpc Dsun2 ? Distance from the Sun (Kinematic-Reid) (4) 61- 65 F5.2 kpc e_Dsun2 ? Uncertainty in Dsun2 (Kinematic-Reid) (4) 67- 71 F5.1 deg Az2 ? Galactic azimuth (Kinematic-Reid) (4) 73- 76 F4.1 kpc Rgal2 ? Galactic radius (Kinematic-Reid) (4) 78- 81 F4.1 kpc Dsun3 ? Distance from the Sun (Best) 83- 87 F5.2 kpc e_Dsun3 ? Uncertainty in Dsun3 (Best) 89- 93 F5.1 deg Az3 ? Galactic azimuth (Best) 95- 98 F4.1 kpc Rgal3 ? Galactic radius (Best) 100-104 F5.3 --- y Helium abundance by number (2) 106-110 F5.3 --- e_y Uncertainty in y 112-116 I5 K Te Local thermodynamic equilibrium (LTE) electron temperature 118-122 I5 K e_Te Uncertainty in Te 124-131 A8 --- Tel Telescope used for the RRL and continuum observations (140 Foot, GBT)
Note (1): Note as follows: b = Distances for these sources are unrealistic because they are located toward the Galactic Center. Our Galactic rotation curve model assumes a maximum Rgal value of 25 kpc. Note (2): For sources with no helium RRL detected, we assume y=0.080±0.000. Note (3): IAU parameters : Distance to the Galactic Center of Ro=8.5 kpc and a Solar circular rotation speed of Θo=220 km/s. Note (4): Reid et al. (2014, J/ApJ/783/130) where Ro=8.3 kpc and Θo=240 km/s.
Global notes: Note (G1): The QF is a qualitative assessment of the line and continuum measurement where "A" is excellent and "D" is poor.
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 14-Sep-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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