EVN observations of low-luminosity flat-spectrum active galactic nuclei

被引：11
作者：
Caccianiga, A
Marcha, MJM
Thean, A
Dennett-Thorpe, J
机构：
[1] Observ Astron Lisboa, CAAUL, P-1349018 Lisbon, Portugal
[2] CNR, Ist Radioastron, I-40129 Bologna, Italy
[3] Univ Groningen, Kapteyn Inst, NL-9700 AV Groningen, Netherlands
来源：
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | 2001年 / 328卷 / 03期
关键词：
galaxies : active; galaxies : Seyfert; radio continuum : galaxies;
D O I：
10.1046/j.1365-8711.2001.04928.x
中图分类号：
P1 [天文学];
学科分类号：
0704 ;
摘要：
We present and discuss the results of very-long baseline interferometry (VLBI, EVN) observations of three low-luminosity (P-5GHz < 10(25) W Hz(-1)) broad emission line active galactic nuclei (AGNs) carefully selected from a sample of flat-spectrum radio sources (CLASS). Based on the total and the extended radio power at 5 and at 1.4 GHz respectively, these objects should be technically classified as radio-quiet AGN and thus the origin of their radio emission is not clearly understood. The VLBI observations presented in this paper have revealed compact radio cores which imply a lower limit on the brightness temperature of about 3 x 10(8) K. This result rules out a thermal origin for the radio emission and strongly suggests an emission mechanism similar to that observed in more powerful radio-loud AGNs. Since, by definition, the three objects show a flat (or inverted) radio spectrum between 1.4 and 8.4 GHz, the observed radio emission could be relativistically beamed. Multi-epoch VLBI observations can confirm this possibility in two years' time.
引用
收藏
页码：867 / 872
页数：6
相关论文
共 29 条
[1]   THE FIRST SURVEY - FAINT IMAGES OF THE RADIO SKY AT 20 CENTIMETERS [J].
BECKER, RH ;
WHITE, RL ;
HELFAND, DJ .
ASTROPHYSICAL JOURNAL, 1995, 450 (02) :559-577
[2]  
Biermann P., 1981, APJ, V250, P49
[3]   The central engines of radio-quiet quasars [J].
Blundell, KM ;
Beasley, AJ .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1998, 299 (01) :165-170
[4]  
Brunthaler A, 2000, ASTRON ASTROPHYS, V357, pL45
[5]   The REX survey: A search for radio-emitting X-ray sources [J].
Caccianiga, A ;
Maccacaro, T ;
Wolter, A ;
Della Ceca, R ;
Gioia, IM .
ASTROPHYSICAL JOURNAL, 1999, 513 (01) :51-68
[6]  
CACCIANIGA A, 2001, UNPUB MNRAS
[7]   The origin of the narrow-line region of Markarian 3: An overpressured jet cocoon [J].
Capetti, A ;
Axon, DJ ;
Macchetto, FD ;
Marconi, A ;
Winge, C .
ASTROPHYSICAL JOURNAL, 1999, 516 (01) :187-194
[8]   OPTICAL SPECTROSCOPY OF THE ROSAT X-RAY BRIGHTEST CLUSTERS .2. [J].
CRAWFORD, CS ;
EDGE, AC ;
FABIAN, AC ;
ALLEN, SW ;
BOHRINGER, H ;
EBELING, H ;
MCMAHON, RG ;
VOGES, W .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1995, 274 (01) :75-84
[9]   Hubble Space Telescope and VLA observations of Seyfert 2 galaxies:: The relationship between radio ejecta and the narrow-line region [J].
Falcke, H ;
Wilson, AS ;
Simpson, C .
ASTROPHYSICAL JOURNAL, 1998, 502 (01) :199-217
[10]   The nature of radio-intermediate quasars: What is radio-loud and what is radio-quiet? [J].
Falcke, H ;
Sherwood, W ;
Patnaik, AR .
ASTROPHYSICAL JOURNAL, 1996, 471 (01) :106-114
123