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J/ApJ/688/290      GASS HI survey of the lower halo         (Ford+, 2008)

H I clouds in the lower halo. I. The Galactic All-Sky Survey pilot region. Ford H.A., McClure-Griffiths N.M., Lockman F.J., Bailin J., Calabretta M.R., Kalberla P.M.W., Murphy T., Pisano D.J. <Astrophys. J., 688, 290-305 (2008)> =2008ApJ...688..290F
ADC_Keywords: Molecular clouds ; H I data ; Radio lines ; Surveys ; Interstellar medium Keywords: galaxies: structure - Galaxy: halo - ISM: clouds - ISM: structure - radio lines: ISM Abstract: We have detected over 400 HI clouds in the lower halo of the Galaxy within the pilot region of the Galactic All-Sky Survey (GASS), a region of the fourth quadrant that spans 18° in longitude, 40° in latitude, and is centered on the Galactic equator. These clouds have a median peak brightness temperature of 0.6K, a median velocity width of 12.8km/s, and angular sizes ≲1°. The motion of these clouds is dominated by Galactic rotation with a random cloud-to-cloud velocity dispersion of 18km/s. A sample of clouds likely to be near tangent points was analyzed in detail. These clouds have radii on the order of 30pc and a median HI mass of 630M. The population has a vertical scale height of 400pc and is concentrated in Galactocentric radius, peaking at R=3.8kpc. This confined structure suggests that the clouds are linked to spiral features, while morphological evidence that many clouds are aligned with loops and filaments is suggestive of a relationship with star formation. The clouds might result from supernovae and stellar winds in the form of fragmenting shells and gas that has been pushed into the halo rather than from a galactic fountain. Description: The data presented in this paper are from the Galactic All-Sky Survey (GASS), a fully sampled Galactic HI survey that covers the entire sky south of declination δ=0°. GASS observations, with the 21cm multibeam receiver at the Parkes Radio Telescope, began in 2005 January and were completed by the end of 2006. The spectral resolution of the data is 0.8km/s. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 66 403 HI clouds - Observed properties table2.dat 80 81 Tangent point HI clouds - Derived properties
See also: VIII/75 : HI survey of the sky DE<+25deg (Bajaja+, 2005) VIII/73 : HI Parkes All Sky Survey Catalogue (HIPASS) (Meyer+, 2004) VIII/54 : Atlas of Galactic Neutral Hydrogen (Hartmann+, 1997) J/ApJ/626/887 : HI clouds in Southern Galactic Plane Survey (Kavars+, 2005) J/ApJS/146/125 : O VI in the galactic halo (Savage+, 2003) J/AJ/123/873 : HIPASS high-velocity clouds (Putman+, 2002) J/ApJS/140/331 : High-velocity HI observations at 21cm (Lockman+, 2002) J/A+AS/142/25 : High velocity HI Southern Survey (Morras+, 2000) J/MNRAS/201/495 : HI Survey of Southern Galactic Plane (Strong+ 1982) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 F6.2 deg GLON Galactic longitude (1) 8- 13 F6.2 deg GLAT Galactic latitude (1) 15- 20 F6.1 km/s VLSR Local Standard of Rest velocity (2) 22- 25 F4.1 km/s e_VLSR Uncertainty in VLSR 27- 30 F4.2 K Tpk Peak brightness temperature (3) 32- 35 F4.1 km/s DelV Velocity profile FWHM (4) 37- 40 F4.1 km/s e_DelV Uncertainty in DelV 42- 46 F5.2 10+19/cm2 NHI HI column density (5) 48- 51 F4.2 10+19/cm2 e_NHI Uncertainty in NHI 53- 54 I2 arcmin amin Minor axis (6) 55 A1 --- --- [x] 56- 58 I3 arcmin amaj Major axis (6) 60- 64 F5.1 Msun/kpc2 MHI/D2 HI surface density (mass divided by squared distance) (7) 66 A1 --- Note Details of prior detections in literature (8)
Note (1): Of the cloud at the position of peak brightness temperature. Note (2): Measured as the velocity of the cloud's peak brightness temperature after background subtraction. Note (3): After background subtraction. Uncertainties are 0.07K. Note (4): Determined by inspection after background subtraction. Note (5): NHI, at the cloud center is 1.94x1018TpkΔνcm-2 in the optically thin limit, an assumption that is reasonable because the emission is faint. An integrated intensity map was not used to subtract a background when determining NHI, and was only used when determining Θmaj, Θmin, and MHId-2. The background subtraction from the line profile in the determination of Tpk was inherently included in the calculation of NHI. Note (6): Maximum and minimum extents of the cloud were determined by inspection from the integrated intensity map of the cloud and are in units of arcminutes. Uncertainties are dominated by background levels surrounding the cloud and are assumed to be 25% of the estimated values. Note (7): HI mass of cloud where "D" is distance to the cloud. Uncertainties are dominated by the interactive process used in mass determination and are assumed to be 40% of the estimated values. Note (8): Clouds that have been cataloged elsewhere in the literature are noted by the following labels: 1 = detected by Putman et al. (2002, Cat. J/AJ/123/873) and 2 = detected by Wakker & van Woerden (1991A&A...250..509W). Although the clouds detected elsewhere do not necessarily have the exact Galactic coordinates and VLSR as listed here, it is likely that they are the same cloud and that the differences are a result of observational constraints. Also, we note that Morras et al. (2000, Cat. J/A+AS/142/25) detected HI in some areas of these clouds but such detections were not identifed as individual objects.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 6 F6.2 deg GLON Galactic longitude (1) 8- 13 F6.2 deg GLAT Galactic latitude (1) 15- 20 F6.1 km/s VLSR Local Standard of Rest velocity (2) 22- 25 F4.1 km/s e_VLSR Uncertainty in VLSR 27- 31 F5.1 km/s Vdev Deviation velocity (3) 33- 36 F4.1 km/s e_Vdev Uncertainty in Vdev 38- 40 F3.1 kpc Dist Heliocentric distance (4) 42- 44 F3.1 kpc e_Dist Uncertainty in Dist 46- 48 F3.1 kpc R Galactocentric distance (5) 50- 52 F3.1 kpc e_R Uncertainty in R 54- 58 F5.2 kpc z Height from Galactic plane (6) 60- 63 F4.2 kpc e_z Uncertainty in z 65- 66 I2 pc Rad Radius of HI cloud (7) 68- 69 I2 pc e_Rad Uncertainty in Rad 71- 75 I5 solMass MHI Physical HI mass (8) 77- 80 I4 solMass e_MHI Uncertainty in MHI
Note (1): Of the cloud at the position of peak brightness temperature. Note (2): Measured as the velocity of the cloud's peak brightness temperature after background subtraction. Note (3): Where Vdev=VLSR-Vt (Wakker, B.P., 1991A&A...250..499W), where Vt is the most negative velocity expected from Galactic rotation in the fourth quadrant and was determined by McClure-Griffiths & Dickey (2007ApJ...671..427M) from H I observations for GLON≤339.695 and by Luna et al. (2006ApJ...641..938L) from CO observations for all remaining longitudes. Note (4): Along the line-of-sight from the Sun to the cloud determined by assuming the cloud is at the tangent point: Dist=R0*cos(GLON)/cos(GLAT) Note (5): Where R=R0|sin(GLON)|, of the tangent point at the cloud's location. Along a given line of sight, the smallest Galactocentric radius possible is at the tangent point. If the cloud is not located at the tangent point it must be further away from the center and the error on R must be positive. Note (6): Determined geometrically to be z=Dist*sin(GLAT). Note (7): Determined by sqrt{rmaj*rmin}. Note (8): Determined as in MHI/D2 in Table 1 but with the tangent point distance assumed.
Nomenclature notes: HI clouds are <[FML2008] LLL.ll+BB.bb> in Simbad. History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 14-Jan-2011
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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