J/ApJ/753/62 Kinematic distance ambiguity in HII regions (Jones+, 2012) ================================================================================ Kinematic distance assignments with H I absorption. Jones C., Dickey J.M. =2012ApJ...753...62J ================================================================================ ADC_Keywords: H II regions ; H I data ; Infrared sources ; Radio sources Keywords: Galaxy: structure; H II regions Abstract: Using H I absorption spectra from the International Galactic Plane Survey, a new method is implemented to resolve the kinematic distance ambiguity for 75 H II regions with known systemic velocities from radio recombination lines. A further 40 kinematic distance determinations are made for H II region candidates without known systemic velocities through an investigation of the presence of H I absorption around the terminal velocity. New kinematic distance determinations can be used to further constrain spiral arm parameters and the location and extent of other structures in the Milky Way disk. H I absorption toward continuum sources beyond the solar circle is also investigated. Follow-up studies of H I at higher resolution than the 1' to 2' of existing Galactic Plane Surveys will provide kinematic distances to many more H II regions on the far side of the Galactic center. On the basis of the velocity channel summation technique developed in this paper, a much larger sample of H II regions will be analyzed in a future paper to remove the near-far distance ambiguity. Description: This paper makes use of radio and infrared archival data. Radio continuum and emission/absorption spectra are extracted from the VLA Galactic Plane Survey (VGPS; Stil et al. 2006AJ....132.1158S) and Southern Galactic Plane Survey (SGPS; McClure-Griffiths et al. 2005ApJS..158..178M), two components of the International Galactic Plane Survey (IGPS). While the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010AJ....140.1868W) and Spitzer Galactic Legacy Infrared Mid-Plane Survey Extradinordinarie (GLIMPSE; Benjamin et al. 2003PASP..115..953B) provide infrared image cutouts used in Section 7. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 131 185 Kinematic distance ambiguity resolutions (KDARs) from velocity channel summations {Sigma}S_ch_ -------------------------------------------------------------------------------- See also: II/311 : WISE All-Sky Data Release (Cutri+ 2012) II/293 : GLIMPSE Source Catalog (I + II + 3D) (IPAC 2008) VIII/58 : A Survey of Radio H II Regions in the Northern Sky (Lockman+ 1989) J/ApJS/194/32 : The HII Region Discovery Survey (HRDS). II. (Anderson+, 2011) J/ApJ/626/887 : HI clouds in Southern Galactic Plane Survey (Kavars+, 2005) J/ApJS/154/553 : Inner galaxy massive star formation regions (Sewilo+, 2004) J/ApJ/582/756 : Velocities of HII regions (Kolpak+, 2003) J/A+A/171/261 : RRLs of Southern HII Regions (Caswell+ 1987) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.3 deg GLON Galactic longitude of the source (1) 9- 14 F6.3 deg GLAT Galactic latitude of the source (1) 16- 19 F4.2 --- Bnoise [0.07/0.5]? Baseline noise of the absorption spectrum ({sigma}(e^-{tau}^)) 21- 23 I3 K Tcont [8/503]? Continuum temperature of the "on" source pixel 25- 31 F7.2 km/s Vterm [-141/126.1]? Terminal velocity (V_T_) 33 A1 --- f_Vrrl [DT] Double or Triple sources (2) 35- 40 F6.1 km/s Vrrl [-122/115]? Velocity from radio recombination lines (V_RRL_) (3) 42- 46 A5 --- Ref Reference for velocities (4) 48- 52 F5.2 --- Svel [-9/50]? Summation of velocity interval S(V_RRL_) to V_T_ for Case III HII regions (5) 54- 57 F4.2 --- e_Svel [0.5/4.1]? Svel uncertainty 59- 64 F6.2 --- Sin [4.6/144.3]? S_ch_ for the whole inner Galaxy 66- 69 F4.2 --- e_Sin [0.6/4.6]? Sin uncertainty 71- 75 F5.2 --- Stp [-5.5/55.1]? S_ch_ for the tangent point interval 77- 80 F4.2 --- e_Stp [0.3/2.4]? Stp uncertainty 82- 86 F5.2 --- Sout [-9.2/24.9]? S_ch_ for the outer Galaxy 88- 91 F4.2 --- e_Sout [0.6/4]? Sout uncertainty 93- 96 A4 --- KDAR KDAR determination (6) 98-102 F5.2 kpc dGR [2.8/12.3]? Galactic radius distance (d_GR_) 104-107 F4.2 kpc E_dGR [0.2/2.7]? Positive error on dGR 109-112 F4.2 kpc e_dGR [0.3/2.1]? Negative error on dGR 114-118 F5.2 kpc dlos [2/19.5]? Kinematic distance (d_los_) (7) 120-123 F4.2 kpc E_dlos [0.5/2.6]? Positive error on dlos (7) 125-128 F4.2 kpc e_dlos [0.02/2.3]? Negative error on dlos (7) 130-131 A2 --- n_dlos [*f ] Remarks on dlos (8) -------------------------------------------------------------------------------- Note (1): Galactic coordinates of the source - corresponding to the location of the highest continuum temperature (see Section 3). Note (2): Sources with (multiple) double or triple RRL velocity component profiles are denoted by "D" and "T," respectively. Note (3): Velocities from "Urq11" (Urquhart et al. 2012MNRAS.420.1656U) are derived from ^13^CO emission. Note (4): Reference as follows: Ar02 = Araya et al. 2002ApJS..138...63A ARM00 = Argon et al. 2000ApJS..129..159A CH87 = Caswell & Haynes 1987, Cat. J/A+A/171/261 GG76 = Georgelin & Georgelin 1976A&A....49...57G GBT11 = Anderson et al. 2011, Cat. J/ApJS/194/32 (GBTRS) L81 = Lockman 1981ApJ...245..459L L89 = Lockman 1989, Cat. VIII/58 LPH96 = Lockman et al. 1996ApJ...472..173L Sw04 = Sewilo et al. 2004, Cat. J/ApJS/154/553 Urq11 = Urquhart et al. 2012MNRAS.420.1656U W70 = Wilson et al. 1970A&A.....6..364W Note (5): note S(V_RRL_) to V_T_ is not measured for regions located at the tangent point. Note (6): KDAR (Kinematic Distance Ambiguity Resolution) as follows: N = near side; N-TP = located before the tangent point; TP = tangent point; TP-F = located at least as far as the tangent point; F = far side; O = outer Galaxy; EG = extragalactic; ? = uncertain. Note (7): Errors are consistent with uncertainties of 15km/s in velocity for HII regions located in the inner Galaxy, and 20km/s for the outer Galaxy. See Figure 7 for kinematic locations. Note (8): Remarks on the dlos computation (see section 8): * = Distances marked with an asterisk (*) are based on the last velocity which shows absorption in the outer Galaxy; except in the case of G26.610-0.210 (f) f = the GBTHRDS (Green Bank Telescope HII Region Discovery Survey, Anderson et al. 2011, Cat. J/ApJS/194/32) has three RRL velocities listed, one of which is negative (-35.7km/s). ** = Distances marked with a double asterisk (**) are based on poor quality KDARs. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Emmanuelle Perret [CDS] 12-Feb-2014