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. =2014AZh....91..503P =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{deg} 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{deg} 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{deg} and Galactic latitudes less than 0.1{deg}. 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{deg} in longitude and 0.2{deg} 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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 {alpha} (S_nu_{prop.to}nu^{alpha}^) 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) -------------------------------------------------------------------------------- Note (1): Recalculated from 0.33GHz (Nord et al., 2004AJ....128.1646N, Cat. J/AJ/128/1646) and 1.4GHz (Lazio and Zoedes, 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, 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, Cat. J/AJ/128/1646, Lazio and Zoedes, 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, Cat. J/ApJS/174/481), indicating it has a small angular size. * Sources No. 10, No. 38 (Lazio and Zoedes, 1998ApJS..118..201L, Cat. J/ApJS/118/201), and No. 15, No. 1, No. 73 (Bower et al., 2001ApJ...558..127B) were previously known (Lazio and Zoedes, 1998ApJS..118..201L, Cat. J/ApJS/118/201), Bower et al., 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), but it is not indicated in that paper that their angular sizes are determined by scattering. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Note (1): assuming proportionality to the square of the wavelength, with the angular size being completely determined by scattering. -------------------------------------------------------------------------------- Byte-by-byte Description of file: refs.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- Ref Reference code 4- 22 A19 --- BibCode BibCode 24- 49 A26 --- Aut Author's name 51-108 A58 --- Com Comments -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 23-Jul-2014