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Astronomy Letters, Vol. 29, No. 9, 2003, pp. 579­586. Translated from Pis'ma v Astronomicheski Zhurnal, Vol. 29, No. 9, 2003, pp. 656­663. i Original Russian Text Copyright c 2003 by Afanasiev, Dodonov, Moiseev, Chavushyan, Mujica, Juarez, Gorshkov, Konnikova, Mingaliev.

Optical and Radio Studies of Radio Sources
V. L. Afanasiev1 , S. N. Dodonov1 , A. V. Moiseev1 , V. Chavushyan2, R. Mujica2 , J. Juarez2 , A. G. Gorshkov3* , V. K. Konnikova3 , and M. G. Mingaliev1
Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz, Karachai-Cherkessian Republic, 357147 Russia 2 National Institute of Astrophysics, Optics, and Electronics, Puebla, Mexico Sternberg Astronomical Institute, Moscow University, Universitetskii pr. 13, Moscow, 119992 Russia
Received January 15, 2003
1

3

Abstract--We present the classification of optical identifications and radio spectra of six radio sources from a complete (in flux density) sample in the declination range 10 to 12 30 (J2000.0). The observations were carried out with the 6-m Special Astrophysical Observatory telescope (Russia) in the wavelength range ° ° 3600­10000 A, the 2.1-m Cananea telescope (Mexico) in the range 4200­9000 A, and the RATAN-600 radio telescope in the frequency range 0.97­21.7 GHz. Three of the six objects under study are classified as quasars, one is a BL Lac object, one is an absorption-line radio galaxy, and one is an emission-line radio galaxy.Five objects have flat radio spectra, and one object has a power-law radio spectrum.All of the radio sources identified as quasars or BL Lac objects show variable flux densities. The spectra of three objects were separated into extended and compact components. c 2003MAIK "Nauka/Interperiodica". Key words: nactive galactic nuclei, quasars and radio galaxies, spectra.

INTRODUCTION In this paper, we classify the optical objects that were identified with radio sources from a complete (in flux density) sample. The sample contains 154 sources with flux densities from the GB6 catalog (Gregory et al. 1996) S4.85 > 200 mJy in the ranges of declinations 10 to 12 30 (J2000.0) and right ascensions 0 to 24h and |b| > 15 ; it has been observed with the RATAN-600 radio telescope since 2000 (Gorshkov et al. 2000). One of the goals of studying this sample is to detect the cosmological evolution of quasars. For this purpose, it is necessary to determine the redshifts for most of the objects identified with the radio sources under study. We identified 86% of the sample sources with flat spectra and 60% of the sample sources with normal spectra with optical objects. A large number of identified objects were classified previously; the remaining objects are classified by using the 2.1-m G. Haro Observatory (GHAO) telescope of the National Institute of Astrophysics, Optics, and Electronics (INAOE) in Cananea (Mexico) (Chavushyan et al. 2000, 2001, 2002) and the 6-m (BTA) Special Astrophysical Observatory (SAO) telescope of the Russian Academy of Sciences in Nizhnii Arkhyz (Russia) (Afanasiev et al. 2003). The redshifts (for some of the BL Lac objects,
*

only the classification is available) of 64 objects with flat spectra and 32 objects with normal spectra are known to date. OPTICAL AND RADIO OBSERVATIONS We obtained the spectra of the objects with the 6m BTA telescope on February 6­8, 2002. We used the SCORPIO spectrograph (http://www.sao.ru/ moisav/scorpio/scorpio.html) in a long-slit mode and a 1024 â 1024 pixel TK1024 CCD detector with a readout noise of 3e-. The covered spectral range was ° ° 3600­10000 A with a dispersion of 6 A pre pixel.The ° effective instrumental resolution was about 20 A. We reduced the spectra in a standard way by using the software developed at the Laboratory of Spectroscopy and Photometry of the SAO. We obtained the spectra of the objects with the 2.1-m GHAO telescope on March 8, 2002. In our observations, we used the LFOSC spectrophotometer equipped with a 600 â 400-pixel CCD array (Zickgraf et al. 1997); the detector readout noise was 8e-, ° and the covered spectral range was 4200­9000 A ° per pixel. The effective with a dispersion of 8.2 A ° instrumental spectral resolution was about 16 A.The reduction of our observations was performed with the IRAF package and included cosmic-ray hit removal,

E-mail: algor@sai.msu.ru

1063-7737/03/2909-0579$24.00 c 2003 MAIK "Nauka/Interperiodica"


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Table 1. Coordinates and magnitudes of the objects Object name 0946 + 1017 1015 + 1227 1103 + 1158 1207 + 1211 1306 + 1113 1315 + 1220
h

Radio coordinates, J2000.0 09 46 35
m s069 .

Optical­radio 0
s011 .

Magnitude R 18.7 18.2 18.4 18.9 13.0 17.8 B 18.7 19.2 18.9 19.0 15.4 18.7

+10 17 06 . 13 +12 27 07.07 +11 58 16.61 +12 11 45.88 +11 13 39.79 +12 20 52.63

-0 . 15 0.19 -0.10 0.05 -0.01 0.10

10 15 44.024 11 03 03.530 12 07 12.625 13 06 19.248 13 15 01.853

-0.001 0.005 0.008 0.015 0.062

flat fielding, wavelength linearization, and flux calibration. The radio observations of the sources were carried out with the Northern Sector of RATAN-600 in 2000­2002 at frequencies of 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz in a fixed-focus mode (Soboleva et al. 1986). The observing and reduction techniques were described by Botashev et al. (1999). The parameters of the RATAN-600 detectors used for the Northern Sector are presented in Berlin et al. (1997). The beam width changed from 11 to 235 in right ascension and from 1.4 to 30 in declination at frequencies from 21.7 GHz to 0.97 GHz. To calibrate the flux densities of the sources, we used the radio source 1347+1217 with a constant flux density, which is a point source for our beams at all frequencies.The adopted flux densities of the calibration source at frequencies 0.97­21.7 GHz are 6.25, 4.12, 3.23, 2.36, 2.00, and 1.46 Jy. The procedure for separating the radio spectra of the sources into extended and compact components was described by Gorshkov et al. (2000). RADIO AND OPTICAL COORDINATES OF THE OBJECTS Table 1 gives the radio coordinates of the program objects for the equinox J2000.0, the differences between their optical and radio coordinates in right ascension and declination, and their R and B magnitudes. The source names are composed of hours and minutes of right ascension and degrees and arcminutes of declination.For our identifications of the radio sources with optical objects, we used the coordinates from the JVAS catalog1 at a frequency of 8.4 GHz (Wrobel et al. 1998); the rms error of the coordinates in right ascension and declination is 0.014 arcseconds. The optical coordinates and magnitudes were taken from the USNO Astrometric Survey (Monet et al. 1996).
1

RESULTS The spectra of the objects taken with the 2.1-m telescope in Mexico and the 6-m BTA telescope are shown in Figs. 1 and 2, respectively. Figure 3 shows the radio spectra of the sources. Table 2 presents the optical observations. Table 3 contains the flux densities of the radio sources and their rms errors in the frequency range 0.97­21.7 GHz. The last column gives the epochs of our observations. Below we give remarks on each of the program objects. In all of the formulas that fit the spectra, the frequencies are in GHz and the flux densities are in mJy. The source 0946+1017. The optical spectrum taken with the 2.1-m telescope (Fig. 1a) exhibits one ° strong line identified with the MgII 2798 A line at the ° redshift z = 0.999. Two lines, MgII 2798 A and CIII ° 1909 A were identified in the spectrum taken with the 6-m telescope (Fig.2a). The redshift determined from these lines is z = 1.007. This object is a quasar with the mean redshift z = 1.004. The source was observed with RATAN-600 twice, in 2000 and 2001. Using the Texas Survey data at a frequency of 0.365 GHz (Douglas et al. 1996), we can separate a power-law component from the spectra with S = 200 -0.85 mJy. After the subtraction of the power-law component, the spectrum of the compact component for the epoch 09.2000 can be fitted by the logarithmic parabola log S = 2.202 + 0.765 log - 0.497 log 2 . The spectrum has a peak at a frequency of 5.9 GHz, with the peak flux density being 313 mJy. In Fig. 3a, the original spectrum and the spectra of the compact and power-law components are indicated by crosses and solid and dashed lines, respectively.The spectrum of the compact component after the subtraction of the power-law component from the data for the epoch 07.2001 can be fitted by the logarithmic parabola log S = 2.237 + 0.616 log - 0.483 log 2 ; the peak in the spectrum
ASTRONOMY LETTERS Vol.29 No.9 2003

JVAS is the Jodrell Bank­VLA Astrometric Survey.


OPTICAL AND RADIO STUDIES OF RADIO SOURCES

581

MgII 1.5

0946+1017 z = 0.999 ()

0.5

1.5 1.0 0.5

1015+12277

(b)

MgII 2 Flux, 10­16 erg ðî­2 s­1 å­1

1103+1158 z = 0.911 (c)

1

0 MgII 1.5 1207+1211 z = 0.890 (d)

0.5

1306+1113 z = 0.084 1.0

H

FeII MgI

NaI (e) [OIII] H H [SII]

0.5

1.0

1315+1220 z = 0.259

(f)

0.5

0

5000

6000

, å

7000

8000

9000

Fig. 1. The optical spectra of the objects taken with the 2.1-m telescope (Mexico). ASTRONOMY LETTERS Vol.29 No. 9 2003


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ÊIII] MgII 0.3

0946+1007 z = 1.007 ()

0.1 3 1015+1227 2 1 Flux, 10­17 erg ðî­2 s­1 å­1 (b)

0.6 ÊIII] 0.2

MgII

1103+1158 z = 0.917 (c)

MgII 0.3 [NeV] [OII]

1207+1211 z = 0.896 H [OIII] (d)

H 0.1 H H [OIII] H

[OII] 1.5

[SII]

0.5 4000 6000

1315+1220 z = 0.261 , å 8000

(e) 10 000

Fig. 2. The optical spectra of the objects taken with the 6-m BTA telescope (Russia).

shifted to a frequency of 4.3 GHz. In this source, we are most likely observing the development of an outburst. The source 1015+1227. Since both optical spectra (Figs. 1b and 2b) contain no lines, we classified this source as a BL Lac object. We observed the source with RATAN-600 three times, in 2000­2002. All of the spectra obtained

rise toward higher frequencies. Figure 3b shows the spectra for the epochs 09.2000 (upper spectrum) and 06.2002 after the subtraction of a small power-law component with S = 45 -0.8 mJy from the original spectra. The spectrum taken at the epoch 07.2001 (Gorshkov et al. 2002) is located between the shown spectra. The flux densities at frequencies of 0.97­ 2.3 GHz were constant within the limits of the meaASTRONOMY LETTERS Vol.29 No.9 2003


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700 ()

1000 (b)

300 300

100 0946+1017 1 700 (c) 3 10 100 700 (d) 1 3 1015+1227 10

300 Flux density, mJy

300

100

1103+1158 1 3 10 (e)

100

1207+1211 1 3 10 (f)

1000

500

300 200

100 1

1306+1113 3 10 100 GHz 1 3

1315+1220 10

Fig. 3. The radio spectra of the sources. The spectra of the sources 0946+1017 and 1103+1158 (a, b) were separated into components: the original spectra are indicated by crosses, the spectra of the extended components are indicated by dashed lines, and the spectra of the compact components are indicated by solid lines. The spectrum of the source 1207+1211 (d) is indicated by pluses, crosses, and asterisks for the epochs 09.2000, 07.2001, and 06.2002, respectively. ASTRONOMY LETTERS Vol.29 No. 9 2003


584 Table 2. Optical observations Object name 0946+1017 Spectral lines CIII MgII MgII 1015+1227 1103+1158 CIII] MgII MgII 1207+1211 MgII [NeV] [OII] H H [OIII] MgII 1306+1113 H MgI FeII NaI 1315+1220 [OII] H H [OIII] H [SII] H [OIII] [OIII] H [SII] 1909/3660 2798/5364 2798/5346 2798/5300 3426/6495 3727/7065 4340/8230 4861/9220 5007/9490 2798/5288 4861/5269 5175/5610 5270/5706 5896/6396 3727/4700 4340/5473 4861/6130 5007/6310 6563/8280 6724/8480 4861/6120 4959/6249 5007/6306 6563/8272 6724/8455 Wavelengths, in rest frame and observed, ° A 1909/3830 2798/5615 2798/5592

AFANASIEV et al.

z 1.007 0.999

Object type QSO QSO

Date of Exposure time, min Telescope observation Feb.07, 2002 Mar.08, 2002 Feb.07, 2002 Mar.08, 2002 10 90 20 60 20 60 20 BTA

z ¯

1.004 GHAO BTA GHAO BTA 0.915 0.911 0.896 QSO QSO Mar.08, 2002 Feb.08, 2002 GHAO BTA 0.895

0.917

QSO

Feb.08, 2002

0.890 0.084

QSO

Mar.08, 2002

30 30

GHAO GHAO 0.084

Abs.G Mar.08, 2002

0.261

Em.G

Feb.06, 2002

20

BTA 0.260

0.259

Em.G

Mar.08, 2002

90

GHAO

surement errors; the largest change in flux density, from 490 ± 44 to 605 ± 25 mJy, was recorded at a frequency of 21.7 GHz. The spectra of the compact components shown in Fig. 3b were fitted by the logarithmic parabolas log S = 2.110 + 0.670 log - 0.120 log 2 (09.2000)

and log S = 2.103 + 0.573 log - 0.098 log 2 (06.2002). We see all of the spectra in an optically thick region; the flux density peaks at frequencies much higher than the range under study. The Source 1103+1158. The optical spectra shown in Figs.1c and 2c exhibit a broad line identified
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OPTICAL AND RADIO STUDIES OF RADIO SOURCES Table 3. Radio observations Object name 0946+1017 1015+1227 1103+1158 Flux densities and errors, mJy 0.97 GHz 353 18 358 20 185 20 310 21 305 20 1207+1211 112 19 112 20 1306+1113 1315+1220 498 35 298 20 2.3 GHz 355 10 352 10 231 11 230 26 305 15 293 07 312 19 215 10 224 10 207 21 290 13 245 18 3.9 GHz 367 05 338 04 302 03 263 07 312 05 320 04 343 04 303 09 260 09 220 05 210 06 219 08 7.7 GHz 340 04 280 03 420 04 354 15 350 04 345 06 386 06 338 07 265 09 238 07 142 04 205 10 11.1 GHz 311 04 250 03 483 05 406 21 396 07 388 05 434 09 381 05 281 05 320 07 112 10 210 07 215 20 21.7 GHz 235 12 181 16 605 25 490 44 490 17 474 20 496 35 420 16 318 18 458 42 Epoch

585

09.2000 07.2001 09.2000 06.2002 09.2000 07.2001 06.2002 09.2000 07.2001 06.2002 11.2001 06.2001

° ° with MgII 2798 A.The line width is FWHM 90 A. ° line was additionally identified in the The CII 1909 A BTA spectrum. We measured the redshift from these lines, z = 0.915. The object is a quasar. We observed the object with RATAN-600 three times, in 09.2000, 07.2001, and 06.2002. A powerlaw component of the source's extended part with S = 180 -0.78 mJy was separated from the original spectra. After the subtraction of the power-law component, the spectrum of the compact component in the frequency range 0.97­21.7 GHz can be fitted by the parabolas log S = 2.151 + 0.433 log - 0.035 log 2 (09.2000), log S = 2.128 + 0.509 log - 0.092 log 2 (07.2001), and log S = 2.135 + 0.618 log - 0.161 log 2 (06.2002). The peak in these spectra successively shifted toward lower frequencies; the development of an outburst is observed. We observed all of the spectra of the compact components in an optically thick region. Figure 3c shows the original spectrum of the source for the epoch 06.2002 (crosses), the spectrum of the extended component (dashed line), and the spectrum of the compact component (solid line). The source 1207+1211. One strong emission ° line that was interpreted as MgII 2798 A at the redshift z = 0.890 can be identified in the object's optical spectrum taken with the 2.1-m telescope (Fig. 1d). ° The line width is FWHM 55 A. In addition to the magnesium line, five more weaker lines can be iden° tified in the BTA spectrum (Fig. 2d): [NeV] 3426 A, ° ° ° [OII] 3727 A, H 4340 A, H 4861 A, and [OIII]
ASTRONOMY LETTERS Vol.29 No. 9 2003

° 5007 A. The object's redshift was estimated from all of these lines to be z = 0.896. We classify the object as a quasar with the mean redshift z = 0.895. We observed the source with RATAN-600 in 09.2000, 07.2001, and 06.2002. Figure 3d shows the source's spectra for these epochs. The source has a variable flux density. All of the spectra are complex and are poorly fitted by logarithmic parabolas. Simultaneously several outbursts probably occur in this source. The extended component is weak in the frequency range under consideration. The largest change in flux density, from 318 ± 18 to 458 ± 42 mJy, was observed at a frequency of 21.7 GHz. The source 1306+1113. We identified the H ° ° ° ° 4861 A, MgI 5175 A, FeII 5270 A, and NaI 5896 A absorption lines in the source's optical spectrum taken with the 2.1-m telescope (Fig. 1e). The redshift was estimated from all of these lines to be z = 0.084. The object is an absorption-line elliptical galaxy. The radio source has a power-law spectrum in the frequency range 0.97­11.2 GHz: S= 484 -0.606 mJy (Fig.3e). The source 1315+1220. Five emission lines ° classified as two hydrogen lines (H 6563 A and ° H 4861 A), two forbidden oxygen lines ([OIII] ° and 5007 A), and one forbidden silicon line ° 4959 A ° ([SII] 6717 A) can be identified in the object's optical spectrum obtained with the 2.1-m telescope (Fig. 1f). ° In addition to these lines, a strong [OII] 3727 A ° line and the H 4340 A line can be identified in the BTA spectrum (Fig. 2e). We classify this object as


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AFANASIEV et al.

an emission-line galaxy. The object's redshift was estimated from all of these lines to be z = 0.260. The source was observed with RATAN-600 in 09.2000 and 06.2001. Within the limits of the measurement errors, the flux density was constant at all frequencies. The spectrum is shown in Fig. 3f. The flattening of the spectrum toward higher frequencies is probably caused by the compact component, but we cannot separate the components in terms of the model under consideration. CONCLUSIONS Three of the six objects under study were classified as quasars with similar redshift, 0.895, 0.915, and 1.004; one object exhibits no lines in its optical spectra, and we classified it as a BL Lac object.All of these objects show variable radio flux densities. The spectra of the objects 0946+1017, 1015+1227, and 1103+1158 were separated into two components: an extended component with a power-law spectrum and a compact component fitted by a logarithmic parabola. In the source 1207+1211, the extended component is weak in the frequency range under consideration. We classified one object as an absorption-line galaxy with a redshift of 0.084 and a power-law radio spectrum and one object as an emission-line galaxy with the redshift z = 0.260 whose radio spectrum flattens toward higher frequencies. 1. ACKNOWLEDGMENTS We wish to thank the administration of the Guillermo Haro Observatory for support and attention to this study. This study was supported in part by the Russian Foundation for Basic Research (project no. 01-02-16333), the "Universities of Russia" Program (project UR.02.03.005), the State Science and Technology Program "Astronomy" (project

1.2.5.1), and the CONACYT (grants nos. 28499-E and O32178-E). REFERENCES
1. V. L. Afanasiev, S. N. Dodonov, A. V. Moiseev, et al., Astron.Zh.(2003, in press). 2. A. B. Berlin, A. A. Maksyasheva, N. A. Nizhel'skii et al., Proceedings of the XXVII Radioastronomical Conference, St.-Petersburg 3, 115 (1997). 3. A. M. Botashov, A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev, Astron. Zh. 76, 723 (1999) [Astron.Rep. 43, 631 (1999)]. 4. V. Chavushyan, R. Mukhika, A. G. Gorshkov, et al., Pis'ma Astron. Zh. 26, 403 (2000) [Astron. Lett. 26, 339 (2000)]. 5. V. Chavushyan, R. Mukhika, A. G. Gorshkov, et al., Astron. Zh. 78, 99 (2001) [Astron. Rep. 45, 79 (2001)]. 6. V. Chavushyan, R. Mukhika, Kh. R. Valdes, et al., Astron. Zh. 79, 771 (2002) [Astron. Rep. 46, 771 (2002)]. 7. D J.Douglas, F.N. Bash, F.Bozyan, et al.,Astron.J. 111, 1945 (1996). 8. A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev, Astron. Zh. 77, 407 (2000) [Astron. Rep. 44, 353 (2000)]. 9. A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev, Preprint no. 111, Spec. Astrophys. Obs. (Nizhnii Arkhyz, 2002). 10. P.C.Gregory, W. K.Scott, K.Douglas, and J.J.Condon), Astrophys.J., Suppl. Ser. 103, 427 (1996). 11. D. Monet, A. Bird, B. Canzian, et al., USNO-SA1.0 (U.S.Naval Obs., Washington, 1996). 12. N. S. Soboleva, A. V. Temirova, T. V. Pyatunina, Preprint 32, Spec. Astrophys. Obs. (Nizhnii Arkhyz, 1986). 13. J. M. Wrobel, A. R. Patnaik, I. W.A. Browne, and P.N.Wilkinson, Astron.Astrophys., Suppl.Ser. 193, 4004 (1998). 14. F. J. Zickgraf, I. Thiering, J. Krautter, et al., Astron. Astrophys., Suppl. Ser. 123, 103 (1997).

Translated by N. Samus'

ASTRONOMY LETTERS

Vol.29

No.9

2003