J/AZh/91/503 Compact radio sources near Galactic center (Pynzar'+, 2014)
Compact radio sources and interstellar scattering near the Galactic center.
Pynzar' A.V., Shishov V.I.
<Astron. Zh. 91, 503 (2014)>
=2014AZh....91..503P 2014AZh....91..503P
=2014ARep...58..427P 2014ARep...58..427P
ADC_Keywords: Radio sources
Abstract:
Using literature data on approximately 400 compact radio sources
detected with the Very Large Array and located in the direction of the
Galactic center within 2° of the compact source Sgr A*, 69 sources
whose angular sizes are determined by scattering on electron density
inhomogeneities were distinguished. Fifty-five of these are
extragalactic, two are supercompact HII regions, ten are sources of
maser emission, and two are variable Galactic sources. The excess of
the apparent angular sizes of maser sources within 2° of the
Galactic center above the mean size of objects of this class in other
parts of the Galaxy found in many studies cannot be explained purely
by the effect of scattering of their radio emission on interstellar
plasma inhomogeneities. The angular sizes of these objects are
increased due to scattering only within Galactic longitudes of about
0.4° and Galactic latitudes less than 0.1°. The turbulent
medium responsible for scattering of radio emission of compact sources
in the immediate vicinity of the Galactic center is strongly
concentrated toward the compact source Sgr A* at the Galactic center.
No extragalactic sources are observed within 0.4° in longitude and
0.2° in latitude of the Galactic center, because of their low
brightness due to the superstrong scattering in this region. Data on
scatter broadening can be used to study the distribution of turbulent
plasma near the Galactic center.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 78 111 Parameters of the sources and the line-of-sight
interstellar medium
table2.dat 77 26 Parameters of the Galactic sources and the
line-of-sight interstellar medium
refs.dat 108 13 References
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See also:
J/ApJS/118/201 : Galactic Center 6 and 20cm survey (Lazio+, 1998)
J/AJ/128/1646 : The Galactic Center region at 330MHz (Nord+, 2004)
J/ApJS/174/481 : 2LC Compact Radio Sources in Galactic center (Lazio+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/119] Sequential number
5- 11 F7.3 deg GLON Galactic longitude
12- 17 F6.3 deg GLAT Galactic latitude
20- 23 F4.1 arcsec theta1 ? 0.33GHz observed angular size (FWHM)
25 A1 --- l_theta2 Limit flag on theta2 (2)
26- 30 F5.2 arcsec theta2 ? 1.4GHz observed angular size (FWHM)
31 A1 --- l_theta3 Limit flag on theta2 (2)
32- 36 F5.2 arcsec theta3 1GHz observed angular size (FWHM) (1)
38- 43 I6 pc/cm3 EM Background emission measure
45- 49 F5.2 --- alpha ? Spectral index α
(Snu∝nuα)
51 A1 --- --- [(]
52- 55 F4.2 --- e_alpha ? rms uncertainty on alpha
56 A1 --- --- [)]
58- 69 A12 --- IR.ref Reference to studies in which infrared sources
were detected toward the radio source,
in refs.dat file
71- 76 A6 --- Type Nature of the source (3)
78 A1 --- n_Seq [*] Note on individual sources (4)
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Note (1): Recalculated from 0.33GHz (Nord et al., 2004AJ....128.1646N 2004AJ....128.1646N,
Cat. J/AJ/128/1646) and 1.4GHz (Lazio and Zoedes, 2008ApJS..174..481L 2008ApJS..174..481L,
Cat. J/ApJS/174/481) assuming that this size is proportional to the square of
the wavelength and that the angular size is completely determined by
scattering.
Note (2): The table lists upper limits for the angular sizes of sources that
were unresolved at 1400MHz (Lazio and Zoedes, 2008ApJS..174..481L 2008ApJS..174..481L,
Cat. J/ApJS/174/481), equal to the half-power beamwidth of the
VLA A configuration at 1400MHz (0.9").
Note (3): Nature of the source as follows:
EXG = extragalactic
EXG(?) = possibly extragalactic
PSR = pulsar
PSR(?) = possibly a pulsar
G = Galactic source of unknown nature
HII = Galactic HII region
Note (4): the notes concern:
* Source No. 23 was not detected at 1400 MHz (Nord et al. 2004AJ....128.1646N 2004AJ....128.1646N,
Cat. J/AJ/128/1646, Lazio and Zoedes, 2008ApJS..174..481L 2008ApJS..174..481L,
Cat. J/ApJS/174/481), testifying to ist spectrum.
* Source No. 31 was not resolved at 1400 MHz (Lazio and Zoedes,
2008ApJS..174..481L 2008ApJS..174..481L, Cat. J/ApJS/174/481), indicating it has a small
angular size.
* Sources No. 10, No. 38 (Lazio and Zoedes, 1998ApJS..118..201L 1998ApJS..118..201L,
Cat. J/ApJS/118/201), and No. 15, No. 1, No. 73 (Bower et al.,
2001ApJ...558..127B 2001ApJ...558..127B) were previously known (Lazio and Zoedes,
1998ApJS..118..201L 1998ApJS..118..201L, Cat. J/ApJS/118/201), Bower et al., 2001ApJ...558..127B 2001ApJ...558..127B)
as sources whose angular sizes were determined by scattering.
* Sources No. 4, No. 8, and No. 10 are classified as extragalactic in
Larosa et al. (2000AJ....119..207L 2000AJ....119..207L), but it is not indicated in that
paper that their angular sizes are determined by scattering.
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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- 2 I2 --- Seq [1/26] Sequential number
4- 24 A21 --- Name Name
26- 32 F7.3 deg GLON Galactic longitude
33- 38 F6.3 deg GLAT Galactic latitude
40- 45 F6.4 arcsec theta ?=- Observed angular size at frequency Freq (FWHM)
46 A1 --- --- [x]
47- 50 F4.2 arcsec theta2 ? Observed angular size at frequency Freq (FWHM)
52- 55 I4 MHz Freq [1612/1720]? Observing frequency
57- 61 F5.3 arcsec theta3 ? Observed angular size reduced to 1GHz (1)
62 A1 --- --- [x]
63- 66 F4.2 arcsec theta4 ? Observed angular size reduced to 1GHz (1)
68- 74 I7 pc/cm3 EM Background emission measure
76- 77 I2 --- Ref Reference to the source data, in refs.dat file
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Note (1): assuming proportionality to the square of the wavelength, with the
angular size being completely determined by scattering.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 --- BibCode BibCode
24- 49 A26 --- Aut Author's name
51-108 A58 --- Com Comments
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Jul-2014