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J/ApJ/722/395     Compact H I clouds from the GALFA-H I survey    (Begum+, 2010)

Compact H I clouds from the GALFA-H I survey. Begum A., Stanimirovic S.Z., Peek J.E., Ballering N.P., Heiles C., Douglas K.A., Putman M., Gibson S.J., Grcevich J., Korpela E.J., Lee M.-Y., Saul D., Gallagher III J.S. <Astrophys. J., 722, 395-411 (2010)> =2010ApJ...722..395B (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Molecular clouds ; Interstellar medium ; H I data Keywords: Galaxy: evolution - Galaxy: halo - ISM: clouds - ISM: kinematics and dynamics - ISM: structure - radio lines: ISM Abstract: The Galactic Arecibo L-band Feed Array H I (GALFA-H I) survey is mapping the entire Arecibo sky at 21 cm, over a velocity range of -700 to +700 km/s (LSR), at a velocity resolution of 0.18 km/s, and a spatial resolution of 3.5 arcmin. The unprecedented resolution and sensitivity of the GALFA-H I survey have resulted in the detection of numerous isolated, very compact H I clouds at low Galactic velocities, which are distinctly separated from the H I disk emission. In the limited area of ∼4600 deg2 surveyed so far, we have detected 96 such compact clouds. The detected clouds are cold with a median Tk,max (the kinetic temperature in the case in which there is no non-thermal broadening) of 300 K. Moreover, these clouds are quite compact and faint, with median values of 5 arcmin in angular size, 0.75 K in peak brightness temperature, and 5x1018/cm2 in H I column density. Most of the clouds deviate from Galactic rotation at the 20-30 km/s level, and a significant fraction show evidence for a multiphase medium and velocity gradients. No counterparts for these clouds were found in other wave bands. From the modeling of spatial and velocity distributions of the whole compact cloud population, we find that the bulk of the compact clouds are related to the Galactic disk, and their distances are likely to be in the range of 0.1 to a few kpc. We discuss various possible scenarios for the formation and maintenance of this cloud population and its significance for Galactic interstellar medium studies. Description: The GALFA-H I survey consists of many individual projects, being observed in both solo modes and commensally with the Arecibo Legacy Fast ALFA Survey (ALFALFA; Giovanelli et al. 2005AJ....130.2598G), Arecibo Galaxy Environment Survey (AGES; Auld et al. 2006MNRAS.371.1617A), and the Galactic ALFA Continuum Transit Survey (GALFACTS; Guram & Taylor 2009ASPC..407..282G) as the Turn-On GALFA Spectrometer (TOGS) and TOGS2 projects. Data cubes used for this study have been made by the core GALFA-H I group and are based on the first data release (released separately as "Spring" and "Fall" data cubes), which uses data from TOGS and several smaller, targeted GALFA-H I projects. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 82 96 The Compact Cloud Sample with Derived Gaussian Parameters
See also: VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005) J/ApJ/688/290 : GASS HI survey of the lower halo (Ford+, 2008) J/AJ/142/170 : ALFALFA survey: α.40 HI source (Haynes+, 2011) J/ApJ/758/44 : The GALFA-HI compact cloud catalog (Saul+, 2012) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Cloud [1/96] Cloud catalog number 4- 5 I2 h RAh Hour of Right Ascension (J2000) 7- 8 I2 min RAm Minute of Right Ascension (J2000) 10- 11 I2 s RAs Second of Right Ascension (J2000) 12 A1 --- DE- Sign of the Declination (J2000) 13- 14 I2 deg DEd Degree of Declination (J2000) 16- 17 I2 arcmin DEm Arcminute of Declination (J2000) 19- 20 I2 arcsec DEs Arcsecond of Declination (J2000) 22- 27 F6.2 deg GLON Galactic longitude 29- 34 F6.2 deg GLAT Galactic latitude 36- 39 F4.2 arcmin theta Size estimated as the geometrical mean of the measured angular extent along the major and minor axes (1) 41- 47 F7.2 km/s VLSR1 Central LSR velocity of the fitted Gaussian components (2) 49- 54 F6.2 km/s VLSR2 ? Central LSR velocity of the fitted Gaussian components (2) 56- 60 F5.2 km/s DeltaV1 Velocity FWHM line width of the fitted Gaussian components (2) 62- 66 F5.2 km/s DeltaV2 ? Velocity FWHM line width of the fitted Gaussian components (2) 68- 71 F4.2 K Tpk1 Peak brightness temperature of the fitted Gaussian components (2) 73- 76 F4.2 K Tpk2 ? Peak brightness temperature of the fitted Gaussian components (2) 78- 82 F5.2 10+18/cm2 NHI H I column density (3)
Note (1): θ=sqrt(θmaxmin). Note (2): Only one value is given if the velocity profile can be well fit with a single Gaussian function. Note (3): NHI is derived under the assumption that the gas is optically thin.
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 17-Aug-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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