- ID:
- ivo://CDS.VizieR/J/A+A/619/A48
- Title:
- GOODS-N AGN VLBI detect. & radio properties
- Short Name:
- J/A+A/619/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Conventional radio surveys of deep fields ordinarily have arc-second scale resolutions often insufficient to reliably separate radio emission in distant galaxies originating from star-formation and AGN-related activity. Very long baseline interferometry (VLBI) can offer a solution by identifying only the most compact radio emitting regions in galaxies at cosmological distances where the high brightness temperatures (in excess of 10^5^K) can only be reliably attributed to AGN activity.The newest VLBI techniques are used to completely cover an entire 7.5' radius area to milliarcsecond resolutions, while bright radio sources (S>0.1mJy) are targeted up to 25-arcmin from the pointing centre. Multi-source self-calibration, and a primary beam model for the EVN array are used to correct for residual phase errors and primary beam attenuation respectively. This paper presents the largest catalogue of VLBI detected sources in GOODS-N comprising of 31 compact radio sources across a redshift range of 0.11-3.44, almost three times more than previous VLBI surveys in this field.
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Search Results
- ID:
- ivo://jvo/isas/darts/halca/halca_vsop_correlated_data
- Title:
- HALCA VSOP (the VLBI Space Observatory Programme) Correlated Data
- Short Name:
- HALCA
- Date:
- 19 Oct 2021 07:12:04
- Publisher:
- JVO
- Description:
- The VSOP (VLBI Space Observatory Programme) mission was led by the Institute of Space and Astronautical Science, in collaboration with the National Astronomical Observatory of Japan with international collaboration with NSAS, CSA, JIVE and the world radio telescopes in 14 countries. This mission provided a dedicated space radio telescope "HALCA" launched in February 1997, and carried out high-resolution observations at 1.6, 5.0, and 22 GHz with ground radio observatories to perform Very Long Baseline Interferometry (VLBI) on baselines of up to 2.6 Earth diameters. The observations are continued till 2003, and HALCA finished its operation in 2005.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A88
- Title:
- High cadence polarization monitoring of OJ287
- Short Name:
- J/A+A/619/A88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multifrequency, dense radio monitoring program of the blazar OJ287 using the 100-m Effelsberg radio telescope. The program aims to test different binary supermassive black hole (SMBH) scenarios and studying the physical conditions in the central region of this bright blazar. Between December 2015 and January 2017 (MJD 57370-57785), the radio electric vector position angle (EVPA) showed a large clockwise (CW) rotation by about 340{deg} with a mean rate of -1.04{deg}/day. Based on concurrent polarized Very Long Baseline Array (VLBA) data, the rotation seems to originate within the jet core at 43GHz. Optical polarization data show a similar monotonic CW EVPA rotation of about -1.1{deg}/day, superposed by shorter and faster rotations of about 7.8{deg}/day, mainly in the CW sense. When combined, the single dish, VLBI and optical polarization data are consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length (0.26pc) and radius (about 0.04pc) and the projected jet bending arc length (about 1.9-7.6pc). The helical trajectory covers only a part of the jet width, possibly its spine. In addition, we found a stable polarized component with EVPA (-10{deg}) perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component.
- ID:
- ivo://CDS.VizieR/J/ApJ/615/702
- Title:
- IC 133 water vapor maser
- Short Name:
- J/ApJ/615/702
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the results of a 14yr long VLBI study of proper motions in the IC 133 H_2_O maser source in the galaxy M33.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/845
- Title:
- Implications of the Galactic aberration for CRF
- Short Name:
- J/MNRAS/445/845
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During the last few years, much attention has been paid to the astrometric implications of the galactic aberration in proper motions (GA). This effect causes systematic errors in astrometric measurements at a {mu}as level. Some authors consider it so serious that it requires redefinition of the Celestial Reference Frame (CRF). We argue that such attention to the GA is exaggerated too much. It is just a small astrometric correction that must be taken into account during highly accurate astrometric and geodetic data processing. The accuracy of this correction depends on the accuracy of the Galactic rotation parameters and, for most applications, on the accuracy of the rotation matrix between Galactic and equatorial systems. Our analysis has shown that our current knowledge of these two factors is sufficient to compute the correction of the GA with an accuracy better than 10 per cent. The remaining effect at the level of a few tenths {mu}as/yr is negligible nowadays. Another consequence of introducing the GA correction is the necessity to return to classical astrometric modelling of the extragalactic radio source position - derived by very-long-baseline interferometry (VLBI) - by the linear trend model. Changing the current paradigm of the VLBI-derived CRF, based on the assumption of zero motion of radio sources, to classical one leads to bias in the radio source positions of up to several tens of {mu}as for a catalogue at epoch J2000.0.
- ID:
- ivo://CDS.VizieR/I/323
- Title:
- International Celestial Reference Frame 2, ICRF2
- Short Name:
- I/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Technical Note describes the generation by an international team of the second realization of the International Celestial Reference Frame (ICRF2) at radio wavelengths using nearly 30 years of Very Long Baseline Interferometry (VLBI) observations. ICRF2 contains precise positions of 3414 compact radio astronomical sources, more than five times the number as in the first ICRF, hereafter ICRF1. Further, the ICRF2 is found to have a noise floor of only 40{mu}as, some 5-6 times better than ICRF1, and an axis stability of 10{mu}as, nearly twice as stable as ICRF1. Alignment of ICRF2 with the International Celestial Reference System (ICRS) was made using 138 stable sources common to both ICRF2 and ICRF1-Ext2. Future maintenance of ICRF2 will be made using a set of 295 new "defining" sources selected on the basis of positional stability and the lack of extensive intrinsic source structure. The stability of these 295 defining sources, and their more uniform sky distribution eliminates the two largest weaknesses of ICRF1.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A119
- Title:
- Jet collimation in NGC 1052
- Short Name:
- J/A+A/658/A119
- Date:
- 22 Feb 2022 14:52:38
- Publisher:
- CDS
- Description:
- With the increased sensitivity and resolution of radio interferometry the study of the collimation and acceleration region of jets in Active Galactic Nuclei(AGN) has come into focus within the last years. Whereas a large fraction of AGN jets reveal a change from parabolic to conical collimation around the Bondi radius, a small number of sources deviate from this standard picture, including the radio galaxy NGC1052. We study the jet width profile, which provides valuable information about the interplay between the central engine and accretion disk system and the collimation and acceleration zone of the jets. We observed the double-sided active galaxy NGC1052 at six frequencies with the VLBA in 2017 and at 22GHz with RadioAstron in 2016. These data are combined with archival 15, 22, and 43GHz multi-epoch VLBA observations. From ridge-line fitting we obtained width measurements along the jet and counter-jet which were fitted with broken power-laws. We find a break in the jet collimation profile at ~10^4^R_s_ (Schwarzschild radii). Downstream of the break the collimation is conical with a power-law index of 1.0-1.2 (cylindrical 0; parabolic 0.5; conical 1). The upstream power-law index of 0.36 for the approaching jet is neither cylindrical nor parabolic and for the receding jet with 0.16 close-to cylindrical. Both jets have an opening angle of ~30 degree at a distance of ~10^3R_S_ and are well collimated with an opening angle of <10 degrees downstream of the break. There are significant differences in the upstream collimation profile between approaching (Eastern) and receding (Western) jet. Absorption or scattering in the surrounding torus as well as an accretion wind may mimic a cylindrical profile. We need to increase the observing frequencies, which do not suffer from absorption to find the true jet collimation profile upstream of 10^4^R_s_.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A67
- Title:
- Jet collimation in NGC 315
- Short Name:
- J/A+A/647/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The collimation of relativistic jets in galaxies is a poorly understood process. Detailed radio studies of the jet collimation region have been performed so far in a few individual objects, providing important constraints for jet formation models. However, the extent of the collimation zone as well as the nature of the external medium possibly confining the jet are still debated. In this article, we present a multifrequency and multiscale analysis of the radio galaxy NGC 315, including the use of mm-VLBI data up to 86GHz, aimed at revealing the evolution of the jet collimation profile. We then consider results from the literature to compare the jet expansion profile in a sample of 27 low-redshift sources, mainly comprising radio galaxies and BL Lacs, which were classified based on the accretion properties as low-excitation (LEG) and high-excitation (HEG) galaxies. We propose that the jet collimation in NGC 315 is completed on sub-parsec scales. A transition from a parabolic to conical jet shape is detected at z_t_=0.58+/-0.28-parsecs or ~5x10^3& Schwarzschild radii (Rs) from the central engine, a distance which is much smaller than the Bondi radius, rB~92pc, estimated based on X-ray data. The jet in this and in a few other LEG in our sample may be initially confined by a thick disk extending out to ~10^3^-10^4^R_{sun}_. A comparison between the mass-scaled jet expansion profiles of all sources indicates that jets in HEG are surrounded by thicker disk-launched sheaths and collimate on larger scales with respect to jets in LEG. These results suggest that disk winds play an important role in the jet collimation mechanism, particularly in high-luminosity sources. The impact of winds on the origin of the FRI and FRII dichotomy in radio galaxies is also discussed.
- ID:
- ivo://jive.eu
- Title:
- JIVE Naming Authority
- Date:
- 10 Jan 2022 19:46:31
- Publisher:
- Joint Institute for VLBI ERIC
- Description:
- JIVE hosts the European VLBI Network (EVN) Data Archive will provide VO services related to that archive
- ID:
- ivo://CDS.VizieR/J/AJ/143/35
- Title:
- KCAL VERA 22 GHz calibrator survey
- Short Name:
- J/AJ/143/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed at 22GHz with the VLBI array VERA a sample of 1536 sources with correlated flux densities brighter than 200mJy at 8GHz. One half of target sources has been detected. The detection limit was around 200mJy. We derived the correlated flux densities of 877 detected sources in three ranges of projected baseline lengths. The objective of these observations was to determine the suitability of given sources as phase calibrators for dual-beam and phase-referencing observations at high frequencies. Preliminary results indicate that the number of compact extragalactic sources at 22GHz brighter than a given correlated flux density level is twice less than at 8GHz.
