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J/AJ/122/3155       Peculiar HI cloud near galactic plane         (Higgs+, 2001)

A peculiar intermediate-velocity hydrogen cloud near the galactic plane. Higgs L.A., Kerton C.R., Knee L.B.G. <Astron. J. 122, 3155 (2001)> =2001AJ....122.3155H
ADC_Keywords: Molecular clouds ; Galactic plane ; H I data ; Radial velocities Keywords: Galaxy: kinematics and dynamics - ISM: H I - radio continuum - radio emission lines Abstract: An H I cloud with a double-lobed structure and a radial velocity of +50km/s has been found near l=92°, b=-4° in a low-resolution H I survey carried out at the Dominion Radio Astrophysical Observatory (DRAO). This velocity is forbidden for circular Galactic rotation. Because of its unusual morphology and small variation in radial velocity over the cloud, further observations of the area were made with the DRAO Synthesis Telescope, both in the H I line and in the radio continuum. The cloud has dimensions of about 3.3°x0.5°, and has a morphology somewhat similar to high-velocity H I clouds (HVCs). Several possible associations with other objects are examined in this paper. A variable inverted-spectrum radio continuum source exists near the morphological center of the H I cloud. It is probably a rare example of a gigahertz peaked spectrum (GPS) extragalactic source having a peak above 5GHz. A luminous B star is found close to the peculiar H I cloud, and the cloud is also located near the center of an H I supershell, supposedly located at a distance of about 9kpc. Energetic and other considerations lead to the conclusion that the cloud is probably not related to the HVC phenomenon nor to any of the above objects but is a relic of a nearby (D∼1kpc) supernova event, all other evidence of which has now dissipated. Maps of continuum radio emission (at 1420 and 408MHz) in the area around the cloud are presented, as well as lists of continuum radio sources. A few isolated high-velocity knots of H I emission have also been detected in the vicinity of the cloud. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 63 10 Parameters of H I knots table4.dat 76 106 Point Sources Observed at 1420 MHz table5.dat 76 56 Point Sources Observed at 408 MHz
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 2 I2 --- [HKK2001] Knot number ([HKK2001] Knot NN) 4- 9 F6.3 deg GLON Galactic longitude 11- 16 F6.3 deg GLAT Galactic latitude 18- 21 F4.1 km/s RV LSR radial velocity 23- 25 F3.1 km/s e_RV rms uncertainty on RV 27- 29 F3.1 km/s DV Observed widths (1) 31- 33 F3.1 km/s e_DV rms uncertainty on DV 35- 37 F3.1 K Tb Peak brightness 39- 41 F3.1 arcmin theta1 Size of the knot 42 A1 --- --- [x] 43- 45 F3.1 arcmin theta2 Size of the knot 47- 57 A11 --- n_theta1 Note on the size 60- 63 F4.2 solMass/kpc2 Mass HI mass in D^2^ solMass (2)
Note (1): The 1.3km/s spectrometer resolution has not been removed. Note (2): The H I masses of the knots are determined from the relation for a Gaussian brightness distribution with peak brightness Tb (K) and half-power widths theta1 x theta2 (arcmin2) and a Gaussian velocity profile with half-power with DV (km/s), at a distance D (kpc): M = 1.49*10-3*Tb*theta1*theta2*DV*D2
Byte-by-byte Description of file: table4.dat table5.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Seq Designation number (1) 8- 13 F6.3 deg GLON Galactic longitude 15- 20 F6.3 deg GLAT Galactic latitude 22- 23 I2 h RAh Hour of Right Ascension (J2000) 25- 26 I2 min RAm Minute of Right Ascension (J2000) 28- 31 F4.1 s RAs Second of Right Ascension (J2000) 33- 35 F3.1 s e_RAs Error in RAs 37- 38 I2 deg DEd Degree of the Declination (J2000) 40- 41 I2 arcmin DEm Arcminute of the Declination (J2000) 43- 44 I2 arcsec DEs Arcsecond of the Declination (J2000) 46 I1 arcsec e_DEs Error in DEs 48- 53 F6.1 mJy FluxDen Integrated flux density (1420MHz for table4, 408MHz for table5) 55- 58 F4.1 mJy e_FluxDen Error in FluxDen 60- 75 A16 --- Comm Comments (2)
Note (1): Follows designation system for DRAO source lists (Higgs, 1986JRASC..80...51H). 71PNNN in table4, 72PNN in table5 Note (2): Comments: a = Parameters of this source were derived from integration of image intensity, not by Gaussian fitting b = This source is not visible in the 408-MHz image, so spectrum may be ``inverted''. c = Position given here differs by 19" from that in NVSS (Condon et al., 1998AJ....115.1693C). E = The source may be slightly resolved (one of the deconvolved dimensions exceeds 15" in 1420MHz images). V = The source may be variable. F = The 408/1420 MHz spectral index is flat (0.25>α>-0.25) where Sint ∝ να I = The spectral index is ``inverted'' (α>0.25) + = 1420-MHz sources weaker than 10mJy contribute to the 408-MHz source ? = A discrepancy of more than 45'' exists between the 1420-MHz and 408-MHz positions.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 07-Mar-2002
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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