Access to Astronomical Catalogues

← Click to display the menu
J/A+A/486/191     Distances towards 6.7GHz methanol masers      (Pandian+, 2008)

Resolving distance ambiguities towards 6.7 GHz methanol masers. Pandian J.D., Momjian E., Goldsmith P.F. <Astron. Astrophys., 486, 191-208 (2008)> =2008A&A...486..191P
ADC_Keywords: Masers ; Radial velocities ; Stars, distances Keywords: Galaxy: kinematics and dynamics - Galaxy: structure - H II regions Abstract: Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7GHz methanol masers, which are signposts of the early stages of massive star formation. We measured 21cm HI absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of HI absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity. Description: The observations were made in June 2005 using the C-Band receiver of Green Bank Telescope. The GBT spectrometer was used in 16 intermediate frequency (IF) mode to cover 8 frequencies in two polarizations. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 76 41 6.7 GHz methanol maser properties
See also: VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998) J/A+AS/134/115 : Medicina 6.7GHz methanol masers survey (Slysh+ 1999) J/A+AS/143/269 : 6.7GHz methanol maser emission survey (Szymczak+, 2000) J/A+A/403/1095 : 6.7GHz methanol masers survey of low-mass YSO (Minier+, 2003) J/other/ChJAA/3.49 : Velocity and distance of methanol maser sources (Xu+ 2003) J/A+A/432/737 : General Cat. of 6.7GHz Methanol Masers (Pestalozzi+, 2005) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Source Methanol maser source name (LL.ll+D.dd) 11 A1 --- m_Source [AB] Multiplicity index for sources which have two recombination line velocities in the same line of sight 12 A1 --- n_Source [abcde] Note on Source (1) 14- 26 A13 --- NVSS NVSS source (HHMMSS+DDMMSS) associated with the methanol maser 27 A1 --- u_NVSS [?] Uncertainty flag on NVSS 29- 31 I3 km/s Vmin ? LSR Velocity extent of the maser emission, lower limit 33- 35 I3 km/s Vmax ? LSR Velocity extent of the maser emission, upper limit 37- 41 F5.1 km/s Vsys Systemic velocity, derived from the radio recombination line 43- 44 A2 --- KDA [NFT? ] KDA resolution (2) 46- 49 F4.1 kpc d ?=- Distance (3) 51- 53 F3.1 kpc E_d ? Error on d, upper limit (5) 55- 57 F3.1 kpc e_d ? Error on d, lower limit (5) 59- 62 F4.1 kpc d' ?=- Modified kinematic distance (4) 64- 66 F3.1 kpc E_d' ? Error on d', upper limit (5) 68- 70 F3.1 kpc e_d' ? Error on d', lower limit (5) 72 A1 --- q_KDA [AB ] Quality grade of the KDA resolution 74- 76 F3.1 mJy sigma rms noise in the 21cm continuum image (in mJy/beam)
Note (1): Note as follows: a = Distance from Blum et al. (2001AJ....121.3149B) b = Source has ambiguity between two recombination lines c = The continuum source associated with the A and B sources may be reversed d = Distance from Genzel et al. (1981ApJ...247.1039G) e = d' for this source is the distance to the tangent point Note (2): kinematic distance ambiguity (KDA) resolution specifying whether the source is as follows: N = at the near distance F = at the far distance T = at the tangent point ? = KDA is unresolved Note (3): calculated from the conventional method using the C85 rotation curve. Note (4): calculated using the methodology described in Sect. 4. Note (5): Errors for distance are not listed when vsys+10 exceeds the tangent point velocity, vt, since such velocities are forbidden, and cannot be converted to a meaningful distance.
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 30-Sep-2008
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

catalogue service