- ID:
- ivo://CDS.VizieR/J/A+A/630/A108
- Title:
- MG B2016+112 radio images
- Short Name:
- J/A+A/630/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6mas in the lensed images by comparing two very long baseline interferometric (VLBI) radio observations at 1.7GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of as. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components, separated by 175 pc, with proper motion of the order of tens {mu}as/yr for the two components at highest magnification ({mu}~350) and of the order of a few mas/yr for the two components at lower magnification ({mu}~2). We propose single Active Galactic Nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (~10^-5^) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/754/38
- Title:
- MgII absorption systems for Flat-Spectrum Radio QSOs
- Short Name:
- J/ApJ/754/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The conventional wisdom that the rate of incidence of MgII absorption systems, dN/dz (excluding "associated systems" having a velocity {beta}c relative to the active galactic nucleus (AGN) of less than ~5000km/s), is totally independent of the background AGNs has been challenged by a recent finding that dN/dz for strong MgII absorption systems toward distant blazars is 2.2+/-^0.8^_0.6_ times the value known for normal optically selected quasars (QSOs). This has led to the suggestion that a significant fraction of even the absorption systems with {beta} as high as ~0.1 may have been ejected by the relativistic jets in the blazars, which are expected to be pointed close to our direction. Here, we investigate this scenario using a large sample of 115 flat-spectrum radio-loud quasars (FSRQs) that also possess powerful jets, but are only weakly polarized. We show, for the first time, that dN/dz toward FSRQs is, on the whole, quite similar to that known for QSOs and that the comparative excess of strong MgII absorption systems seen toward blazars is mainly confined to {beta}<0.15. The excess relative to FSRQs probably results from a likely closer alignment of blazar jets with our direction; hence, any gas clouds accelerated by them are more likely to be on the line of sight to the active quasar nucleus.
- ID:
- ivo://CDS.VizieR/J/A+A/636/A16
- Title:
- M43, Horsehead, MonR2, M17SW [CII]158um spectra
- Short Name:
- J/A+A/636/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The [CII] 158um FIR fine-structure line is one of the most important cooling lines of the star-forming ISM. It is used as a tracer of star formation efficiency in external galaxies and to study feedback effects in parental clouds. High spectral resolution observations have shown complex structures in the line profiles of the [CII] emission. To determine whether the complex profiles observed in [^12^CII] are due to individual velocity components along the line-of-sight or due to self-absorption, one has to compare the [^12^CII] and isotopic [^13^CII] line profiles. Deep integrations with the SOFIA/upGREAT 7-pixel array receiver in the sources M43, Horsehead PDR, Monoceros R2 and M17 SW allow to detect with high S/N the optically thin [^13^CII] and simultaneously the [^12^CII] emission lines. We first derive the [^12^CII] optical depth and the [CII] column density from a single component model. However, the complex line profiles observed require a double layer model with an emitting background and an absorbing foreground. A multi-component velocity fit allows to derive the physical conditions of the [CII] gas: column density and excitation temperature. We find moderate to high [^12^CII] optical depths in all four sources, and self-absorption of [^12^CII] in Mon R2 and M17 SW. The high column density of the warm background emission corresponds to an equivalent Av of up to 41mag. The foreground absorption requires substantial column densities of cold and dense [CII] gas, with an equivalent Av ranging up to about 13mag. The column density of the warm background material requires multiple PDR surfaces stacked along the line of sight and in velocity. The substantial column density of dense and cold foreground [CII] gas detected in absorption cannot be explained with any known scenario and we can only speculate about its origin.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2792
- Title:
- 1388MHz ATLBS Low-Brightness Survey
- Short Name:
- J/MNRAS/402/2792
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a radio survey carried out with the Australia Telescope Compact Array. A motivation for the survey was to make a complete inventory of the diffuse emission components as a step towards a study of the cosmic evolution in radio source structure and the contribution from radio-mode feedback on galaxy evolution. The Australia Telescope Low-Brightness Survey (ATLBS) at 1388MHz covers 8.42deg^2^ of the sky in an observing mode designed to yield images with exceptional surface brightness sensitivity and low confusion. The survey was carried out in two adjacent regions on the sky centred at 00:35:00-67:00:00 and 00:59:17=-67:00:00 (J2000.0). The ATLBS radio images, made with 0.08mJy/beam rms noise and 50arcsec beam, detect a total of 1094 sources with peak flux exceeding 0.4mJy/beam. The ATLBS source counts were corrected for blending, noise bias, resolution and primary beam attenuation; the normalized differential source counts are consistent with no upturn down to 0.6mJy.
- ID:
- ivo://CDS.VizieR/J/A+AS/58/1
- Title:
- 1412 MHz catalogue of Westerbork survey. I.
- Short Name:
- J/A+AS/58/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A radio survey has been conducted with the Westerbork Synthesis Radio Telescope for nine fields in four high latitude areas for which deep, multicolor Kitt Peak 4-m plates are available. A total of 471 sources are tabulated; 306 of these form a well defined, complete sample. The influence of the selection criteria on sample completeness is discussed. Angular size distribution has been precisely derived, in virtue of the 3 km resolution obtainable with the present instrument, and a smaller fraction of sources larger than about 20arcsec is noted for the 1-10mJy range than for the 10-100mJy. The 1412MHz source counts are consistent at different cutoff levels, showing that the statistical corrections for population and resolution bias are reliable. The present counts are consistent with previous 1.4GHz counts, which are here given for the 1-100000mJy flux range.
- ID:
- ivo://CDS.VizieR/J/A+AS/58/39
- Title:
- 1412 MHz catalogue of Westerbork survey. II
- Short Name:
- J/A+AS/58/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep multicolor optical identification program is presented for a complete sample of 302 radio sources that were observed with the Westerbork Synthesis Radio Telescope within 5.52{deg}^2^ down to S_1.4GHz_>~0.6mJy (5{sigma}). Optical identifications are made from multicolor prime focus plates taken with the Kitt Peak 4 meter telescope in the passbands U,J,F and N with approximate respective limiting magnitudes of ~23.3, 23.7, 22.7 and 21.1. The astrometry has systematic errors smaller than 0.2"-0.3", while the random errors are of order 0.4". The agreement between the radio and optical coordinate frames is on average better than 0.25". Identifications are based on positional coincidence using the likelihood ratio method. For 171 out of the 302 radio sources likely identifications are proposed with an a posteriori identification percentage of 53%, 14 expected spurious objects (or 5% of all radio sources), while not more than 4 identifications have been missed. The sample reliability is 92% and its completeness 98%. About 20% of the identifications are stellar objects, the remaining have extended images or are too faint to be classified. About 15% of the identifications appear in possible clusters. The identification statistics are roughly constant from field to field, except for the Hercules 2 field which has an unusually high identification fraction (74%). The identification fraction is presented as a function of 21 cm flux density and limiting magnitude, and amounts to 15% for 1<~S_1.4GHz_<~100mJy down to the Palomar Sky Survey limit and 29% down to the effective 48" Schmidt limit. For S_1.4_<~100mJy the identification fraction remains roughly constant with flux density, contrary to the prediction of higher fractions by some models for cosmological evolution. The magnitude distributions for galaxies plus objects of unknown type generally increase towards fainter magnitudes; the quasar magnitude distributions are also increasing but not as steeply as for the radio galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/251/330
- Title:
- 8400MHz flux densities for Southern sources
- Short Name:
- J/MNRAS/251/330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+AS/65/485
- Title:
- 22MHz flux densities of radio sources
- Short Name:
- J/A+AS/65/485
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- table1 is a compilation of the flux densities at 22.25MHz for 395 sources, derived from three or more observations of each source. The source were measured over a period of several years with the T-shaped radiotelescope at the Dominion Astrophysical Observatory. The Note: This catalogue supersedes Cat. <J/AJ/74/366>
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/775
- Title:
- 330MHz flux of 4 SNR near Galactic Centre
- Short Name:
- J/MNRAS/329/775
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed two fields - Field I (l=3.2{deg}, b=1.0{deg}) and Field II (l=356.8{deg}, b=-0.1{deg}) - with the Giant Metrewave Radio Telescope (GMRT) at 330MHz. In the first field, we have studied the candidate supernova remnant (SNR) G3.1-0.6 and, based on its observed morphology, spectral index and polarization, confirmed it to be an SNR. We find this supernova to have a double ring appearance with a strip of emission on its western side passing through its centre. We have discovered two extended curved objects in the second field, which appears to be part of a large shell-like structure. It is possibly the remains of an old supernova in the region. Three suspected SNRs, G356.3-0.3, G356.6+0.1 and G357.1-0.2, detected in the MOST 843-MHz survey of the GC region appear to be located on this shell-like structure. While both G356.3-0.3 and G356.6+0.1 seem to be parts of this shell, G357.1-0.2, which has a steeper spectrum above 1GHz, could be a background SNR seen through the region. Our Hi absorption observation towards the candidate SNR G357.1-0.2 indicates that it is at a distance of more than 6kpc from us.
- ID:
- ivo://CDS.VizieR/J/other/AuJPA/14.77
- Title:
- 408MHz galactic radio sources
- Short Name:
- J/other/AuJPA/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Contour maps of 58 regions are presented showing 408 MHz radioisophotes for over 200 galactic radio sources. Positions and integrated flux densities are listed for all the sources.