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Radio survey for new compact HII regions [ CATS home ] [ Back to CATS list ] [ ftp ]

1982A&A...108...227Wink

Results of a radio survey for new compact HII regions

Wink J.W., Altenhoff W.J., Mezger P.G.

Summary

This paper containes an investigation of 91 sources which appear to be point sources when observed with the angular resolution of the 100-m telescope at 4.9 GHz, teta_a = 2.6', and which we expected to be HII regions. The basic search list was prepared from the 4.9 GHz survey of the galactic plane by Altenhoff et al. (1978). These sources (or subsamples of these sources, respectively) were observed in the continuum at 5, 15, and 86 GHz with single dish telescope, and at 2.7 and 8.1 GHz with a three-element interferometer. Another subsample was searched for its H90alpha and H76alpha recombination line emission. For varios reasons a number of previosly known compact HII regions was included in some of the single-dish and interferometer observations.

Five out the 91 sources of the basic list were found to be non-thermal sources and another was indentified with a known planetary nebula.
...

I.Single dish continuum observations

To determime the spectral index of a source we made cross scans through its peak in galactic coordinates, using the 100-m telescope at 4.9 and 14.8 GHz, where the telescope HPBW is 2.6' and 1.0' respectively. The observing mode was beam switching in the primary focus with beams alighed in galactic latitude. 
 GHz    HPBW'   Telescope   Fluxes NGC7027
4.875    2.6     100m        5.50
8.875    1.5     100m        6.15
 14.8    1.0     100m        6.05
 86      1.3     11m         5.02
Column 1-4 give gal. and equatorial(1950) coordinates derived from 14.8 GHz observations. The positional accuracy is typically: ~5". Columns 5-8 give the peak flux densities at 4.9, 8.9, 14.8 and 86 GHz, respectively. The 4.9 GHz observations were already incorporated in Altenhoff et al.(1978). In the present paper we list 4.9 GHz flux densities only for sources for sources for which we present new observations. The errors are typically less than 5 % or 0.05 Jy at 4.9, 8.9, 14.8 GHz and about 15 % or 0.2 Jy at 86 GHz.
Column 9 gives the deconvolved half power width of the source (HPW) obtained from 14.8 GHz observations. Column 10 and 11 give, for extended sources, the intergrated flux densities at 4.9 and 14.8 GHz, respectively, assuming gaussian source and beam shape. These were calculated using the ralation integral{B_v D_Omega} = S_peak(1+ (teta_s/teta_A)^2), with S_peak and teta_s from table 2 and teta_A from Table 1, respectively. For those cases where the HPW's derived at 4.9 and 14.8 GHz are not too different Column 12 gives the spectral index alpha (S~v^+alpha) derived from the integrated flux densities.

Symbols in the last column have the following meaning:
* source structure indicated
a source size obtained from 4.875 GHz data 

Symbols in the last column have the following meaning:
 * source structure indicated
 a source size obtained from 4.875 GHz data
-------------------------------------------------------------------------------------------------
   name           RA 1950  DEC 1950    S_peak (Jy) at GHz      TETA   S_tot at GHz  Sp.
   l        b    hh mm ss    dd mm ss  4.875 8.875 14.8  86    '15GHz 4.875   14.8  index Remarks
-------------------------------------------------------------------------------------------------
 359.277  -0.264 17 41 43.6 -29 40 14  1.41  0.88  0.52         1.5   1.89    1.69  -0.1
 359.281  -0.826 17 43 56.5 -29 57 44  1.28  0.77  0.39         1.75  1.8     1.58  -0.1