J/ApJ/690/706 Distances of Galactic HII regions (Anderson+, 2009)
Resolution of the distance ambiguity for Galactic H II regions. Anderson L.D., Bania T.M. <Astrophys. J., 690, 706-719 (2009)> =2009ApJ...690..706A
ADC_Keywords: H II regions ; Radio lines ; H I data Keywords: H II regions - ISM: molecules - radio lines: ISM - stars: formation Abstract: We resolve the kinematic distance ambiguity for 266 inner Galaxy HII regions out of a sample of 291 using existing HI and 13CO sky surveys. Our sample contains all HII regions with measured radio recombination line emission over the extent of the 13CO Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey (18<l<55° and |b|<1) and contains ultra compact (UC), compact, and diffuse HII regions. We use two methods for resolving the distance ambiguity for each HII region: HI emission/absorption (HI E/A) and HI self-absorption (HI SA). Description: Our sample of 291 HII regions is that of Paper I (Anderson et al. 2009ApJS..181..255A). For the HI SA analysis we use both the HI surveys and the Boston University-Five College Radio Astronomy Observatory (BU-FCRAO) 13CO Galactic Ring Survey data (GRS; Jackson et al. 2006ApJS..163..145J available at http://www.bu.edu/galacticring). For the HI E/A analysis we use data from the VLA 21cm HI Galactic Plane Survey (VGPS; Stil et al. 2006AJ....132.1158S) and the Southern Galactic Plane Survey (SGPS; McClure-Griffiths et al. 2005ApJS..158..178M). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 47 291 HII region kinematic parameters table2.dat 40 291 HII region kinematic distances
See also: V/112 : Catalog of Star-Forming Regions in the Galaxy (Avedisova, 2002) VIII/58 : A Survey of Radio H II Regions in the Northern Sky (Lockman+ 1989) VII/50 : CO Radial Velocities Toward Galactic H II Regions (Blitz+ 1982) J/ApJS/181/255 : CO in galactic HII regions (Anderson+, 2009) J/ApJ/626/887 : HI clouds in Southern Galactic Plane Survey (Kavars+, 2005) J/A+A/397/133 : Star-forming complexes in the Galaxy (Russeil+, 2003) J/ApJS/140/331 : High-velocity HI observations at 21cm (Lockman+, 2002) http://www.bu.edu/galacticring : Galactic Ring Survey (GRS) home page Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 12 A12 --- Name Source name, based on galactic position (1) 14- 18 F5.2 deg GLON Galactic longitude 20- 24 F5.2 deg GLAT Galactic latitude 26- 30 F5.1 km/s VLSR Radio recombination line LSR velocity (2) 32- 34 F3.1 kpc Rgal Galactrocentric radius (3) 36- 38 F3.1 kpc Dnear The near distance 40- 43 F4.1 kpc Dfar The far distance 45- 47 F3.1 kpc Dtp The tangent point distance
Note (1): There are 25 lines of sight with multiple radio recombination line velocities. The source names for these HII regions are denoted with an extra "a" or "b". Note (2): Typical measurement errors are 2km/s (see data compiled in Anderson et al. 2009ApJS..181..255A). This error is insignificant compared to uncertainties in the rotation curve model, which may be 10km/s. Note (3): All kinematic distances calculated using the rotation curve of McClure-Griffiths & Dickey (2007ApJ...671..427M).
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 12 A12 --- Name Source name 14- 16 I3 km/s Vabs ? Maximum velocity of HI absorption 18 A1 --- Abs? [N/Y] HI absorption detected within 10km/s of radio recombination line velocity 20 A1 --- KDA1 [NFT] Near/Far kinematics distance ambiguity (KDA) resolution for Emission/Absorption method 21 A1 --- f_KDA1 [*] Ambiguity on KDA1 (4) 23 A1 --- q_KDA1 [A/B] Confidence parameter for KDA1 (A for high confidence or B for low) (5) 25 A1 --- KDA2 [NF] Near/Far KDA resolution for Self-Absorption method 26 A1 --- f_KDA2 [*] Ambiguity on KDA2 (4) 28 A1 --- q_KDA2 [A/B] Confidence parameter for KDA2 (A for high confidence or B for low) (5) 30- 33 F4.1 kpc Dist ? Distance from the sun (6) 35- 40 F6.1 pc Z ? Height above the Galactic plane
Note (4): For sources whose HIE/A and HISA kinematics distance ambiguity (KDA) resolutions disagree, the KDA resolution that we adopt is marked with an asterisk. Note (5): We assign to each source a confidence parameter in order to indicate the likelihood that the HI SA feature is an artifact of noise or of background fluctuations. This qualitative parameter indicates our confidence that the HI SA kinematics distance ambiguity (KDA) resolution is correct. For "A" sources at the near distance, the HI absorption signal is strong, unambiguous, and at the same velocity as the 13CO emission line. For "A" sources at the far distance, the HI at the velocity of the 13CO emission line is smooth and shows no fluctuations that could be interpreted as weak absorption. The reliability of the KDA resolution for "B" quality sources is less certain due to a fluctuating HI spectrum or weak 13CO emission. Note (6): Kinematic distances calculated using the rotation curve of McClure-Griffiths & Dickey (2007ApJ...671..427M).
History: From electronic version of the journal References: Anderson et al. Paper I. 2009ApJS..181..255A Cat. J/ApJS/181/255
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 16-Feb-2011
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