Fifteen years monitoring of extragalactic radio sources at 22, 37 and 87 GHz

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1 ASTRONOMY & ASTROPHYSICS NOVEMBER I 99, PAGE SUPPLEMENT SERIES Astron. Astrophys. Suppl. Ser., (99) Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz H. Teräsranta, M. Tornikoski, A. Mujunen,K.Karlamaa,T.Valtonen,N.Henelius,S.Urpo,M.Lainela, T. Pursimo, K. Nilsson,S.iren,A.Lähteenmäki, M. Korpi,R.Rekola,P.Heinämäki,M.Hanski, P. Nurmi,K.Kokkonen,P.Keinänen,O.Joutsamo,J.Oksanen,H.Pietilä, E. Valtaoja,M.Valtonen,and P. Könönen Metsähovi Radio Research Station, Helsinki University of Technology, FIN- Kylmälä, Finland Tuorla Observatory, FIN- Piikkiö, Finland Observatory, PO Box, University of Helsinki, FIN- Helsinki, Finland Received February ; accepted April 7, 99 Abstract. Over continuum observations of extragalactic sources are presented. These observations of 7 sources at, 7 and 7 GHz more than doubles the millimeter observations of these sources. The data are between 99. and 99., and combined with our earlier published data they form a year database. Key words: galaxies: active BL Lacertae objects: general quasars: general radio continuum: galaxies radio continuum: general. Introduction Observing extragalactic radio sources, generally speaking quasars has, been increasingly popular during the last years due to the numerous space borne instruments dedicating a large share of their observing time to this field. Instruments like EGRET onboard the Compton GRO (gamma rays), IUE (ultraviolet), GINGA, ASCA, XTE and ROSAT (X-rays), ISO (infrared) and many others have prompted coordinated groundbased observations. Two observing windows can be covered from the ground: the radio window (below GHz) and the optical window. Monitoring of extragalactic radio sources has been continued with the Send offprint requests to: H.Teräsranta Correspondence to: hte@alpha.hut.fi The data (Table ) are only available in electronic form at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (.79..) or via Metsähovi radio telescope since 9, most of the observations being at and 7 GHz. Our sample mostly consists of Northern flat spectrum sources which have at least once reached Jy at GHz (Valtaoja et al. 99). At lower frequencies (, and GHz) the Michigan group has been monitoring a larger sample, which also includes most of our sources, since 9 (Aller et al. 9). At still higher radio frequencies there are three monitoring efforts: our 9, and GHz monitoring of southern sources with the SEST-telescope (Tornikoski et al. 99), the Ian Robson team working with the JCMT-telescope at,, 7 and 7 GHz (Stevens et al. 99), as well as the IRAM-team at 9, and GHz (Reuter et al. 997) and in references therein. At optical wavelengths there are several monitoring efforts concentrating on AGN, like the ones at Tuorla Observatory (Sillanpää et al. 99), at Rosemary Hill Observatory (ebb et al. 9), at Foggy Bottom Observatory, at Calar Alto Observatory by the Hamburg Quasar Monitoring Program (Schramm et al. 99) and the Heidelberg group, at Asiago Observatory (Barbieri et al. 977), at Perugia University Observatory (Fiorucci & Tosti 99), at Torino Observatory (Villata et al. 997), at Dodaira Station (Kikuchi 9) and at the Yunnan Observatory (Xie et al. 99). The estern Kentucky University has a new automated AGN monitoring program with two optical telescopes (Hackney et al. 99). Typically the variations in AGN are slower at radio frequencies than at higher frequency bands and thus the sampling density does not have to be so high. A monthly sampling will usually be adequate for cm-observations. Below mm you should have weekly observations to get most of the variations covered. At optical frequencies even faster sampling would be desired.

2 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz Table. Receiver parameters Frequency HPB Beam B(IF) T sys GHz separation MHz K DSB... a... b a Before June 99. b After June 99. Table. Parameters K and K with the old and new antenna Frequency K (old) K (new) K (old) K (new) GHz GHz GHz Observations The observations presented here were done with the Metsähovi Radio Telescope during at, 7 and 7 GHz. The Metsähovi.7 m diameter ESSCO design antenna is placed inside a radome. In August 99 the original radome was replaced with a new one. Also the reflector panels and the back structure of the antenna were replaced with more accurate ones during the summer of 99. The receiving system parameters are listed in Table. The flux density scale is calibrated against DR, our primary calibration source. Its fluxes at, 7 and 7 GHz are 9., 7.9 and 7. Jy, respectively, according to Baars et al. (977) and Ulich (9). As secondary calibration sources we have used C 7 and planets like Jupiter. The receivers at and 7 GHz are of a dual beam type with a ferrite swich operating at Hz. At 7 GHz the beam switching at a rate of Hz is performed with a rotating chopper-wheel. The old GHz mixer front end receiver was replaced with a more sensitive one with a low noise HEMT amplifier as a first stage in June 99. The 7 GHz receiver is a mixer front end receiver operating at room temperature. The 7 GHz receiver is a Schottky mixer front end receiver cooled to K.. Data reduction The data reduction is similar to the one described in Teräsranta et al. (99), although the upgrading of the antenna lead to changes in some parameters. The fluxcalculating procedure is done with Eqs. () to (). The error estimate for the flux is from Eq. (), where the relative errors of the optical depth, noise tube calibration and flux integreation have been quadratically added. U τ S = K K K e sin(el) () U cal K = ( K (P P opt ) ) () P opt = P K sin(el) K T () K =+(θ/hpb), for Gaussian sources () K =(θ/./hp B ) /( e (θ/./hp B )), () for planets δs = S (δu/u) +(δτ/ sin(el)) +(δcal/ucal) ). () In the formulae, S the flux density in Jy U the observed voltage from the A/D converter U cal the exess voltage coming from the noise tube calibration K the factor for converting receiver voltages to Janskys τ the optical depth of the atmosphere el the elevation angle during the observation K the correction for the antenna focusing K the correction factor for source size K the frequency dependent focus sharpness factor K the elevation dependent factor of the focus K the temperature dependent factor of the focus P the position of the subreflector during the observation(milli-inch) P opt the optimal position of the subreflector during the observation(milli-inch) P the position of the receiver focus in respect to the antenna focus (milli-inch) T the physical temperature of the antenna ( C) θ the source diameter HPB the antenna half power beam width δs the error estimate for the observation δu the rms error of the integration δτ the error of the estimation of the optical depth δcal the error of the noise tube calibration. The optimal position of the antenna focus is a function of the elevation angle and temperature according to Eq. (). Two fixed positions for the focus were used, one for the summer and one for the winter. This kept the correction factor K still quite small at the used elevation range from to 7 degrees. As the corrections for the focus-offset are larger at higher frequencies, the results at 7 GHz are more severely affected. In Table. the values of the parameters K and K are tabulated at each observing frequency with the old (before summer 99) and new antenna (after summer 99). The parameter K was the same. with both antennas.. Results The list of sources with classification and number of observations at each frequency is shown in Table. In the

3 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 7 source classification HPQ states that the source has been recorded at least once an optical polarization level equal or above.%, for the LPQ type sources the polarization level has allways been below.%. BL Lac type object are identified with BLO and galaxies with GAL. Sources with no classification have no optical polarization observation from the literature or have simply no optical counterpart like NRAO. Due to the large number of data points (over ), the numerical tables are available only in electronic form at the CDS via anonymous ftp. The data in Table consists of date (year, month, day and hour(ut)) and the flux (Jy) and sigma error estimate (Jy). There are 7 sources in Table, from which about belong to our main sample. Some additional sources have also been observed during many multifrequency campaigns, but that data will be published elsewhere. The flux curves for the best observed sources are given in Fig.. The numerical values for some sources during 9 and 99 in Fig. are found in iren et al. (99). The flux curves in the figures contain the whole year span of our observations. The numerical values for the observations prior 99. can be found in Salonen et al. (97), Teräsranta et al. (97) and Teräsranta et al. (99). The flux densities in Fig. are weekly mean values to allow an easier examination of the flux development. For many sources there are long periods of daily observations, which can be found in Table. Generally the sources seem to vary on these frequencies on a monthly basis, the shorter variations are usually within the error bars. In some cases, like in +9, there was one considerably higher flux point. hen combined with another observation within a week for the figure it produced a giant error bar. Another example is in OL 9 where we also had an anomalous high value. These have been carefully checked and as no fault was found they remain in the database. At our highest observing frequency (7 GHz), the poor antenna surface accuracy prior to summer 99 limited the observations to only a few sessions. Acknowledgements. This work has been supported by the Academy of Finland. References Aller H.D., Aller M.F., Latimer G.E., Hodge P.E., 9, ApJS 9, Baars J..M., Gentzel R., Pauline-Toth I.I.K., itzel A., 977, A&A, 99 Barbieri C., Romano G., Di Serego A., et al., 977, A&A 9, 9 Fiorucci M., Tosti G., 99, A&AS 7, 7 Hackney R., Hackney K., Scott R., et al., 99, at Blazar Continuum Variability conference, PASPC, p. Kikuchi S., 9, Tokyo Astron. Bull., No., p. 7 Reuter H.-P., Kramer C., Sievers A., et al., 997, A&AS, 7 Salonen E., Teräsranta H., Urpo S., et al., 97, A&AS 7, 9 Schramm K.J., Borgeest U., Kühl D., et al., 99, A&AS, 9 Sillanpää A., Mikkola S., Valtaoja L., 99, A&AS, Stevens J.A., Litchfield S.J., Robson E.I., et al., 99, ApJ 7, 9 Teräsranta H., Valtaoja E., Haarala S., et al., 97, A&AS 7, Teräsranta H., Tornikoski M., Valtaoja E., et al., 99, A&AS 9, Tornikoski M., Valtaoja E., Teräsranta H., et al., 99, A&AS, 7 Ulich B., 9, AJ, 9 Valtaoja E., Lähteenmäki A., Teräsranta H., 99, A&AS 9, 7 Villata M., Raiteri C.M., Chisellinei G., et al., 997, A&AS, 9 iren S., Valtaoja E., Teräsranta H., Kotilainen J., 99, AJ, 9 ebb J.R., Smith A.G., Leacock R.J., et al., 9, AJ 9, 7 Xie G.Z., Li K.H., Zhang Y.H., et al., 99, A&AS,

4 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz Table. Source list with classification and number of observations at each frequency Designation other name classification n n7 n7 BLO 7+ III Z LPQ +7 LPQ 97 BLO + OC HPQ 9 9+ BLO 9 LPQ +7 DA HPQ LPQ 9 +9 HPQ BLO 7 + BLO C A BLO LPQ 7 9+ HPQ + HPQ + BLO 9 GAL + LPQ 9 +7 BLO 7 + BLO + C GAL 9 + BLO + NRAO LPQ 9 CTA BLO + NRAO C OA 9 HPQ + BLO + C GAL NRAO 9 HPQ 9 + GAL + BLO +9 LPQ 9 HPQ 7 + LPQ +9 DA 9 LPQ 7 HPQ +9 OH 7 LPQ 77+7 LPQ 7+7 BLO LPQ 7+7 BLO HPQ 7+ LPQ BLO 7 7+ LPQ 7+ OI 9. BLO HPQ 9 Table. continued Designation other name classification n n7 n7 + BLO 7 + BLO 9 + HPQ 7+ LPQ 7 +9 BLO 9 9+ BLO +7 LPQ + BLO + LPQ + OJ 7 BLO 9+7 LPQ 7 9+ C HPQ 9+97 HPQ 9+9 C 9. LPQ LPQ 7 9+ LPQ 9+ HPQ 9+ BLO 97+7 BLO + HPQ 9+ + LPQ 9+ LPQ + OL 9 HPQ 7+ BLO + Mark BLO 9 +7 BLO 7+ LPQ 7 LPQ 9 7+ BLO HPQ +9 C 9. HPQ BLO + BLO 9+ ON BLO C 7 LPQ 9 LPQ C 79 HPQ 99 LPQ + BLO BLO + OQ BLO 9 + OR HPQ 9 HPQ + HPQ +9 C. BLO 7 +7 HPQ + HPQ + BLO + LPQ + LPQ + C. LPQ OS LPQ

5 Table. continued H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 9 Designation other name classification n n7 n7 +99 C HPQ HPQ 7 +9 Mark BLO 7 + HPQ NRAO 79+ HPQ 7 HPQ 79+9 OT BLO BLO +7 BLO 7+9 C 7 BLO 7 + BLO 9 +7 C LPQ +797 C 9. GAL LPQ LPQ BLO + O 7 LPQ CYG X HPQ 7 BLO + OX 7 LPQ + OX LPQ +7 OX 9 LPQ +9 OX LPQ + BL Lac BLO 7 + LPQ 7 LPQ 9 C HPQ HPQ 7 HPQ + CTA HPQ HPQ 7 + C. HPQ 9 +7 BLO LPQ 9

6 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz OC Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. eekly mean flux density of observed sources at and 7 GHz

7 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz DA Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

8 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz + Metsahovi GHz 7 7 Metsahovi 7 GHz AO + Metsahovi GHz Metsahovi 7 GHz Fig.. continued

9 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz C Metsahovi GHz Metsahovi 7 GHz NRAO Metsahovi GHz Metsahovi 7 GHz Fig.. continued

10 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz NRAO Metsahovi GHz Metsahovi 7 GHz OA 9 Metsahovi 7 GHz Metsahovi GHz Fig.. continued

11 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz C Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

12 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz + Metsahovi GHz Metsahovi 7 GHz DA 9 Metsahovi GHz Metsahovi 7 GHz Fig.. continued

13 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 7 OH 7 Metsahovi GHz Metsahovi 7 GHz PKS 7+7 Metsahovi GHz Metsahovi 7 GHz Fig.. continued

14 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 7+7 Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

15 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 9 OJ 7 Metsahovi GHz Metsahovi 7 GHz C 9. Metsahovi GHz Metsahovi 7 GHz Fig.. continued

16 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz OL 9 Metsahovi GHz Metsahovi 7 GHz C 9. Metsahovi GHz Metsahovi 7 GHz Fig.. continued

17 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz ON Metsahovi GHz Metsahovi 7 GHz C 7 Metsahovi GHz Metsahovi 7 GHz Fig.. continued

18 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz C 79 Metsahovi GHz 9 Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

19 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz + Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

20 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz C. Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

21 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz C. Metsahovi GHz Metsahovi 7 GHz C Metsahovi GHz 9 Metsahovi 7 GHz Fig.. continued

22 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz +9 Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

23 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 7 7- Metsahovi GHz Metsahovi 7 GHz Metsahovi GHz Metsahovi 7 GHz Fig.. continued

24 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz + Metsahovi GHz Metsahovi 7 GHz OX 7 Metsahovi GHz Metsahovi 7 GHz Fig.. continued

25 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz 9 +7 Metsahovi GHz Metsahovi 7 GHz BL Lac Metsahovi GHz Metsahovi 7 GHz Fig.. continued

26 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz + Metsahovi GHz Metsahovi 7 GHz C Metsahovi GHz Metsahovi 7 GHz Fig.. continued

27 H. Teräsranta et al.: Fifteen years monitoring of extragalactic radio sources at, 7 and 7 GHz CTA Metsahovi GHz Metsahovi 7 GHz C. Metsahovi GHz Metsahovi 7 GHz Fig.. continued