J/AJ/104/704 A VLA Search for Young Galactic Supernova Remnants (Sramek+, 1992)
A VLA Search for Young Galactic Supernova Remnants
Sramek R.A., Cowen J.J., Roberts D.A., Goss W.M., Ekers R.D.
<Astron. J. 104, 704 (1992)>
=1992AJ....104..704S 1992AJ....104..704S
ADC_Keywords: Supernova remnants; Surveys; Radio sources
Description:
This catalog contains the results of a galactic plane radio survey of
possible very young supernova remnants. Of the 290 sources studied,
only one possible SNR under 100 years old was identified. Table 1
summarizes the survey data. Table 2 is a compilation of the follow-up
6cm observations of 14 candidate shell sources.
The search list was compiled from three surveys:
Clark and Crawford (1974) at 408 MHz;
Haynes et al (1979) at 5 GHz;
Altenhoff et al (1978) at 4.9 GHz.
The H110alpha radio recombination line survey of Downes et al.
(1980A&AS...40..379D 1980A&AS...40..379D) was used to remove H II regions from the search
list. A list of 500 SNR candidates was produced in this way. Limited
observing time meant that only the brightest 290 of these sources were
observed in late 1984. The authors conclude that only one of these is
a possible very young SNR.
Abstract:
In the attempt to identify very young galactic supernova remnants
(SNRs), 290 known compact (<2') galactic plane radio sources were
observed at 20cm using the VLA in its 36 km configuration. The VLA
observations described could detect supernovae with diameters between
5 and 20"; these would have an age of between 25 and 100 yr. Compact
structure was detected in 168 (58%) of the 290 different sources
observed; 73 sources (25%) were unresolved or slightly resolved point
sources, 21 (7%) were single-well resolved, 56 (19%) were double, 18
(6%) were triple or complex. The large scale structure was completely
resolved out for 122 (42%) of sources. Additional observations at 6cm
with the VLA in the 11 km configuration were made of 14 sources with
apparent shell structures that might have been characteristic of young
SNRs. Low resolution observations were made at 20cm of 62 fields
where the source was completely resolved out in the high resolution
images. Only one source, G25.5+0.2, is a possible very young SNR. New
H66_alpha recombination line observations place severe constrains on
any thermal interpretation for this object.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 52 291 High resolution galactic plane radio SNR survey
table2.dat 65 14 6cm observations of apparent shell structures
table3.dat 41 62 Low resolution galactic plane radio SNR survey
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.2 deg GLON Galactic Longitude (l2)
7- 11 F5.2 deg GLAT Galactic Latitude (b2)
13- 14 I2 h RAh *Right Ascension hours (1950)
15- 16 I2 min RAm *Right Ascension minutes (1950)
17- 20 F4.1 s RAs *Right Ascension seconds (1950)
21 A1 --- DE- *[± ]Declination sign (1950)
22- 23 I2 deg DEd *Declination degrees (1950)
24- 25 I2 arcmin DEm *Declination minutes (1950)
26- 27 I2 arcsec DEs *Declination seconds (1950)
29 A1 --- l_s20cm *[ <]Limit flag for 20cm flux
30- 34 F5.3 Jy s20cm *Peak 20cm flux density in 3'x3' box
36 A1 --- struct *[PSDCE]Radio structure of dominant source
38- 39 A2 --- obs *Epoch of observation
41 A1 --- ref *Reference of original survey
44- 45 A2 s newRAs *?New Right Ascension (seconds only)
47- 50 F4.1 arcmin newDEm *?New Declination (minutes only)
52 A1 --- note *?Notes
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Note on RAh,RAm,RAs,DE-,DEd,DEm,DEs:
Right Ascension and Declination (1950.0) as listed in the original survey
catalog (see Ref column for survey reference)
Note on l_s20cm:
< indicates s20cm is approximate 5 sigma upper limit for fields in which the
source is resolved out.
Note on s20cm:
Peak 20cm flux density on VLA image in a 3.0x3.0 arcmin box centered on the
catalogued position. For double and complex sources the peak flux density
refers only to the brightest component. No attempt was made to integrate
flux densities. See the notes for related information.
Note on struct:
The radio structure of the dominant high brightness compact source. The
symbols' meanings are as follows
P = point sources or slightly resolved
S = single extended source
D = double source
C = complex structure with several knots and/or filaments
E = empty field - the catalog source is probably resolved out
Note on obs:
"A" observations were toward the galactic anticenter;
"B" observations were toward the galactic center
A1 = 29 Nov. 1984
A2 = 30 Nov. 1984
B1 = 7 Dec. 1984
B2 = 24 Dec. 1984
B3 = 28 Dec. 1984
Note on ref:
1 = Clark & Crawford 1974
2 = Haynes+ (1979)
3 = Altenhoff+ (1978)
Note on newRAs:
Improved right ascension seconds of time, if the peak of the compact
structure is more than 0.5 arcmin from the catalogued position
Note on newDEm:
Improved declination arcminutes, if the peak of the compact structure
is more than 0.5 arcmin from the catalogued position
Note on note:
A = improved positions and 6cm flux densities are given in Table 2
B = low resolution, wide field images were made at 20cm; see Table 3
1 = diameter about 45 arcsec
2 = other components about 30 arcsec to SE; 7 and 5 mJy peak
3 = other components about 30 arcsec to S; 5 mJy
4 = listed source is same as listed at l=21.05
5 = extended source 4 mJy; peak 45 arcsec to N; another 90 arcsec to NE
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.2 deg GLON *Galactic Longitude (l2)
7- 11 F5.2 deg GLAT *Galactic Latitude (b2)
13- 14 I2 h RAh *?Right Ascension hours (1950)
15- 16 I2 min RAm *?Right Ascension minutes (1950)
17- 20 F4.1 s RAs *?Right Ascension seconds (1950)
21 A1 --- DE- *[± ]Declination sign (1950)
22- 23 I2 deg DEd *?Declination degrees (1950)
24- 25 I2 arcmin DEm *?Declination minutes (1950)
26- 27 I2 arcsec DEs *?Declination seconds (1950)
30- 34 F5.3 Jy s6cm Peak 6cm flux density
37- 41 F5.2 --- SpIndex *Spectral index between 6 and 20cm
44- 65 A22 --- MType *?Description of morphology of source
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Note on GLON,GLAT:
Galactic longitude and galactic latitude as derived from the original survey
catalog
Note on RAh,RAm,RAs,DE-,DEd,DEm,DEs:
Right Ascension and Declination (1950.0) of the peak brightness of the source
as determined by the 6cm observations
Note on SpIndex:
Spectral index between 6 and 20 cm wavelength using peak flux densities
given in Table 1 and Table 2.
Note on MType:
Description of the source morphology, e.g. Shell, Point Source
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 6 F6.2 deg GLON *Galactic Longitude (l2)
7- 11 F5.2 deg GLAT *Galactic Latitude (b2)
13- 14 I2 h RAh *?Right Ascension hours (1950)
15- 16 I2 min RAm *?Right Ascension minutes (1950)
17- 20 F4.1 s RAs *?Right Ascension seconds (1950)
21 A1 --- DE- *[± ]Declination sign (1950)
22- 23 I2 deg DEd *?Declination degrees (1950)
24- 25 I2 arcmin DEm *?Declination minutes (1950)
26- 27 I2 arcsec DEs *?Declination seconds (1950)
29 A1 --- l_s20cm *[ <]Limit flag for 20cm flux
30- 34 F5.3 Jy s20cm *Peak 20cm flux density in 3'x3' box
36 A1 --- struct *[PSDCE]Radio structure of dominant source
38 A1 --- note1 *?Notes on general structure
40- 41 I2 --- note2 *?Notes on individual sources; "listed
source described in the table; other
comments refer to additional sources in
the image. Positions and flux densities
are for the brightness maxima.
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Note on GLON,GLAT:
Galactic longitude and galactic latitude as derived from the original survey
catalog
Note on RAh,RAm,RAs,DE-,DEd,DEm,DEs:
Right Ascension and Declination (1950.0) of the peak brightness of the source
as determined by the low resolution VLA 20cm observations
Note on l_s20cm:
< indicates s20cm is approximate 5 sigma upper limit for fields that remain
completely resolved.
Note on s20cm:
Peak 20cm flux density. For double and complex sources the peak flux density
refers only to the brightest component. No attempt was made to integrate
flux densities. See the notes for related information.
Note on struct:
Classification of the radio structure of the dominant high brightness
compact source. The symbols' meanings are as follows:
P = point sources or slightly resolved
S = single extended source
D = double source
C = complex structure with several knots and/or filaments
E = empty field - the catalog source is probably resolved out
Note on note1:
A = Extended low brightness emission in addition to the compact
structure indicated by the classification.
B = Possible shell structure
Note on note2:
1 = compact source, 1.40 Jy peak, at RA=18h00m37s, DE=24d22.9'
2 = double source, 0.25 Jy peak, at RA=18h03m19s, DE=-21d38'
3 = single, 0.162 Jy, at RA=18h06m46s, DE=-19d27.0'
4 = other weak knots nearby
5 = point source, 0.58 Jy, at RA=18h31m41s, DE=-07d57.1'
6 = point source, 0.15 Jy, at RA=18h37m57s
7 = another point source. 0.12 Jy, at RA=18h40m19s, DE=-04d17'
8 = listed double 30" separation, well resolved components.
9 = correction applied, FWZI about 1.1 arcmin.
10 = G29.7-0.3 is 15 arcmin to NW
11 = point source, 1.17 Jy, at RA=18h47m23s, DE=-01d36.4'
12 = point source, 0.43 Jy, at RA=18h44m59s, DE=-01d16.0'
13 = double source, 0.17 Jy, at RA=18h49m34s, DE=-00d04.5'
14 = point source, 0.53 Jy, at RA=18h49m14s, DE=-00d31.9'
15 = extended emission region 3' FWZI, offset 4'S of point source
16 = point source, 0.32 Jy, at RA=18h57m47s, DE=-03d59.0'
tailed (shell?) source, .26 Jy peak, at RA 18h58m33s, DE=04d07.7'
17 = extended emission region 4' FWZI, offset 8' N of catalogued position
18 = listed double source has 0.5' separation
19 = listed double source has 0.6' separation
20 = listed double source has 1.5' separation
21 = point source, 0.23 Jy, at RA=07h18m27s, DE=-15d13.9'
listed double source has 20" separation
22 = listed source has extended, 2.3' FWZI
23 = listed source has diameter 45" FWZI
24 = listed double source has 30" separation
25 = listed double source has 45" separation
26 = listed double source has 20" separation
27 = extended, partial shell source, 1.04 Jy peak, at RA=17h16m04s,
DE=-37d07.8'
28 = extended, complex source, 1.1 Jy peak, centered on RA=17h17m30s,
DE=-35d43'
29 = extended, complex source, 2.4 Jy peak, centered on RA=17h21m27s,
DE=-34d08'
30 = broad structure with many knots and filaments seen on image;
heavily resolved
31 = partial shell source, 0.15 Jy peak, at RA=17h28m11s, DE=-33d31.5',
2.5' diameter FWZI
32 = very extended diffuse emission over 8' diameter area
33 = heavily confused by SGR A * about 20' to north
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Acknowledgements:
These tables were originally prepared via OCR and proofread by Heinz
Andernach in October 1998. Further checks of the files were made
by him in July 2000, some minor errors were found in Table 1 and
corrected.
References:
Altenhoff W.J., et al., 1978, A&AS, 35, 23 =1978A&AS...35...23A 1978A&AS...35...23A
Clark D.H., Crawford D.F., 1974, AuJP, 27, 713 =1974AuJP...27..713C 1974AuJP...27..713C
Downes D., et al., 1980, A&AS, 40, 379 =1980A&AS...40..379D 1980A&AS...40..379D
Haynes R.F., et al., 1979, AuJPS, 48,1 =1979AuJPS..48....1H 1979AuJPS..48....1H
(End) James E. Gass [SSDOO/ADC] 18-Aug-2000