Search

Start Over Subject radio astronomy
71. ALMA third image of lensed quasar PKS 1830-211
ID:
ivo://CDS.VizieR/J/A+A/641/L2
Title:
ALMA third image of lensed quasar PKS 1830-211
Short Name:
J/A+A/641/L2
Date:
21 Oct 2021
Publisher:
CDS
Description:
Strong gravitational lensing distorts our view of sources at cosmological distances but brings invaluable constraints on the mass content of foreground objects and on the geometry and properties of the Universe. We report the detection of a third continuum source toward the strongly lensed quasar PKS 1830-211 in ALMA multi-frequency observations of high dynamic range and high angular resolution. This third source is point-like and located slightly to the north of the diagonal joining the two main lensed images, A and B, 0.3" away from image B. It has a flux density that is 140 times weaker than images A and B and a similar spectral index, compatible with synchrotron emission. We conclude that this source is most likely the expected highly de-magnified third lensed image of the quasar. In addition, we detect, for the first time at millimeter wavelengths, weak and asymmetrical extensions departing from images A and B that correspond to the brightest regions of the Einstein ring seen at centimeter wavelengths. Their spectral index is steeper than that of compact images A, B, and C, which suggests that they arise from a different component of the quasar. Using the GravLens code, we explore the implications of our findings on the lensing model and propose a simple model that accurately reproduces our ALMA data and previous VLA observations. With a more precise and accurate measurement of the time delay between images A and B, the system PKS 1830-211 could help to constrain the Hubble constant to a precision of a few percent.
72. 2A0335+096 LOFAR images
ID:
ivo://CDS.VizieR/J/A+A/659/A20
Title:
2A0335+096 LOFAR images
Short Name:
J/A+A/659/A20
Date:
04 Mar 2022 06:16:07
Publisher:
CDS
Description:
Radio observations represent a powerful probe of the physics occurring in the intracluster medium (ICM) because they trace the relativistic cosmic rays in the cluster magnetic fields, or within galaxies themselves. By probing the low-energy cosmic rays, low-frequency radio observations are especially interesting because they unveil emission powered by low-efficiency particle acceleration processes, which are believed to play a crucial role in the origin of diffuse radio emission. We investigate the origin of the radio mini-halo at the center of the galaxy cluster 2A0335+096 and its connection to the central galaxy and the sloshing cool core. We also study the properties of the head-tail galaxy GB6 B0335+096 hosted in the cluster to explore the lifecycle of the relativistic electrons in its radio tails. We use new LOw Frequency ARray (LOFAR) observations from the LOFAR Two-meter Sky Survey at 144MHz to map the low-frequency emission with a high level of detail. The new data were combined with archival Giant Metrewave Radio Telescope and Chandra observations to carry out a multi-wavelength study. We have made the first measurement of the spectral index of the mini-halo ({alpha}=-1.2+/-0.1 between 144MHz and 1.4GHz) and the lobes of the central source ({alpha}=~-1.5+/-0.1 between 144 and 610MHz). Based on the low-frequency radio emission morphology with respect to the thermal ICM, we propose that the origin of the diffuse radio emission is linked to the sloshing of the cool core. The new data revealed the presence of a Mpc-long radio tail associated with GB6 B0335+096. The observed projected length is a factor 3 longer than the expected cooling length, with evidence of flattening in the spectral index trend along the tail. Therefore, we suggest that the electrons toward the end of the tail are kept alive by the ICM gentle re-acceleration.
73. AMI 1.8cm observations in c2d small clouds
ID:
ivo://CDS.VizieR/J/MNRAS/410/2662
Title:
AMI 1.8cm observations in c2d small clouds
Short Name:
J/MNRAS/410/2662
Date:
21 Oct 2021
Publisher:
CDS
Description:
We perform deep 1.8-cm radio continuum imaging towards 13 protostellar regions selected from the Spitzer c2d small clouds and cores programme at high resolution (25-arcsec) in order to detect and quantify the cm-wave emission from deeply embedded young protostars. Within these regions we detect 15 compact radio sources which we identify as radio protostars including two probable new detections. The sample is in general of low bolometric luminosity and contains several of the newly detected VeLLO sources. We determine the 1.8cm radio luminosity to bolometric luminosity correlation, L_rad_-L_bol_, for the sample and discuss the nature of the radio emission in terms of the available sources of ionized gas. We also investigate the Lrad-LIR correlation and suggest that radio flux density may be used as a proxy for the internal luminosity of low-luminosity protostars.
74. AMI Galactic Plane Survey at 16GHz. I.
ID:
ivo://CDS.VizieR/J/MNRAS/429/3330
Title:
AMI Galactic Plane Survey at 16GHz. I.
Short Name:
J/MNRAS/429/3330
Date:
21 Oct 2021
Publisher:
CDS
Description:
The AMI Galactic Plane survey is being made with the Arcminute Microkelvin Imager (AMI) Small Array at 15.7GHz and with resolution of approximately 3arcmin. This is the first data release, covering ~868deg^2^ of the Northern Galactic plane between |b|~+/-5{deg} and above {delta}=40{deg} with a noise level of ~3mJy/beam away from bright sources. The source catalogue contains a total of 3503 sources.
75. AMI Galactic Plane Survey at 16GHz. II.
ID:
ivo://CDS.VizieR/J/MNRAS/453/1396
Title:
AMI Galactic Plane Survey at 16GHz. II.
Short Name:
J/MNRAS/453/1396
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Arcminute Microkelvin Imager Galactic Plane Survey (AMIGPS) provides mJy-sensitivity, arcminute-resolution interferometric images of the northern Galactic plane at ~16GHz. The first data release covered 76{deg}<=l<=170{deg} between latitudes of |b|<=5{deg}; here we present a second data release, extending the coverage to 53{deg}<=l<=193{deg} and including high-latitude extensions to cover the Taurus and California giant molecular cloud regions, and the recently discovered large supernova remnant G159.6+7.3. The total coverage is now 1777{deg}^2^ and the catalogue contains 6509 sources. We also describe the improvements to the data processing pipeline which improves the positional and flux density accuracies of the survey.
76. AMIGA XIII. HI properties
ID:
ivo://CDS.VizieR/J/A+A/609/A17
Title:
AMIGA XIII. HI properties
Short Name:
J/A+A/609/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the largest catalogue of HI single dish observations of isolated galaxies to date, as part of the multi-wavelength compilation being performed by the AMIGA project (Analysis of the interstellar Medium in Isolated GAlaxies). Despite numerous studies of the HI content of galaxies, no revision has been made for the most isolated L* galaxies since Haynes & Giovanelli (1984AJ.....89..758H). The AMIGA sample has been demonstrated to be almost "nurture free", therefore, by creating scaling relations for the HI content of these galaxies we will define a metric of HI normalcy in the absence of interactions. The catalogue comprises of our own HI observations with Arecibo, Effelsberg, Nancay and GBT, and spectra collected from the literature. In total we have measurements or constraints on the HI masses of 844 galaxies from the Catalogue of Isolated Galaxies (CIG). The multi-wavelength AMIGA dataset includes a revision of the B-band luminosities, optical diameters, morphologies, and isolation. Due to the large size of the catalogue, these revisions permit cuts to be made to ensure isolation and a high level of completeness, which was not previously possible. With this refined dataset we fit HI scaling relations based on luminosity, optical diameter and morphology. Our regression model incorporates all the data, including upper limits, and accounts for uncertainties in both variables, as well as distance uncertainties. The HI scaling relations of the AMIGA sample define an up-to-date metric of the HI content of almost "nurture free" galaxies. These relations allow the expected HI mass, in the absence of interactions, of an individual galaxy to be predicted to within 0.25dex (for typical measurement uncertainties). These relations are thus suitable for use as statistical measures of the impact of interactions on the neutral gas content of galaxies.
77. AMI 15.7GHz GRB catalogue
ID:
ivo://CDS.VizieR/J/MNRAS/473/1512
Title:
AMI 15.7GHz GRB catalogue
Short Name:
J/MNRAS/473/1512
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the Arcminute Microkelvin Imager (AMI) Large Array catalogue of 139 gamma-ray bursts (GRBs). AMI observes at a central frequency of 15.7GHz and is equipped with a fully automated rapid-response mode, which enables the telescope to respond to high-energy transients detected by Swift. On receiving a transient alert, AMI can be on-target within 2-min, scheduling later start times if the source is below the horizon. Further AMI observations are manually scheduled for several days following the trigger. The AMI GRB programme probes the early-time (<1d) radio properties of GRBs, and has obtained some of the earliest radio detections (GRB 130427A at 0.36 and GRB 130907A at 0.51d post-burst). As all Swift GRBs visible to AMI are observed, this catalogue provides the first representative sample of GRB radio properties, unbiased by multiwavelength selection criteria. We report the detection of six GRB radio afterglows that were not previously detected by other radio telescopes, increasing the rate of radio detections by 50 per cent over an 18-month period. The AMI catalogue implies a Swift GRB radio detection rate of >~15 per cent, down to ~0.2mJy/beam. However, scaling this by the fraction of GRBs AMI would have detected in the Chandra & Frail (2012, Cat. J/ApJ/746/156) sample (all radio-observed GRBs between 1997 and 2011), it is possible ~44-56 per cent of Swift GRBs are radio bright, down to ~0.1-0.15mJy/beam. This increase from the Chandra & Frail (2012, Cat. J/ApJ/746/156) rate (~30 per cent) is likely due to the AMI rapid-response mode, which allows observations to begin while the reverse-shock is contributing to the radio afterglow.
78. AMI-LA 16 GHz sources in Perseus region
ID:
ivo://CDS.VizieR/J/MNRAS/415/893
Title:
AMI-LA 16 GHz sources in Perseus region
Short Name:
J/MNRAS/415/893
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep radio continuum observations of the cores identified as deeply embedded young stellar objects in the Perseus molecular cloud by the Spitzer c2d programme at a wavelength of 1.8cm with the Arcminute Microkelvin Imager Large Array (AMI-LA). We detect 72% of Class 0 objects from this sample and 31% of Class I objects. No starless cores are detected. We use the flux densities measured from these data to improve constraints on the correlations between radio luminosity and bolometric luminosity, infrared luminosity and, where measured, outflow force. We discuss the differing behaviour of these objects as a function of protostellar class and investigate the differences in radio emission as a function of core mass. Two of four possible very low luminosity objects (VeLLOs) are detected at 1.8cm.
79. Ammonia and CO outflow around 6.7GHz methanol masers
ID:
ivo://CDS.VizieR/J/AJ/152/92
Title:
Ammonia and CO outflow around 6.7GHz methanol masers
Short Name:
J/AJ/152/92
Date:
21 Oct 2021
Publisher:
CDS
Description:
Single point observations are presented in NH_3_ (1, 1) and (2, 2) inversion transitions using the Effelsberg 100m telescope for a sample of 100 6.7GHz methanol masers and mapping observations in the ^12^CO and ^13^CO (1-0) transitions using the Purple Mountain Observatory Delingha 13.7m telescope for 82 sample sources with detected ammonia. A further 62 sources were selected for either ^12^CO or ^13^CO line outflow identification, producing 45 outflow candidates, 29 using ^12^CO and 16 using ^13^CO data. Twenty-two of the outflow candidates were newly identified, and 23 had trigonometric parallax distances. Physical properties were derived from ammonia lines and CO outflow parameters were calculated. Histograms and statistical correlations for ammonia, CO outflow parameters, and 6.7GHz methanol maser luminosities are also presented. No significant correlation was found between ammonia and maser luminosity. However, weak correlations were found between outflow properties and maser luminosities, which may indicate that outflows are physically associated with 6.7GHz masers.
80. Ammonia observations in G79.29+0.46
ID:
ivo://CDS.VizieR/J/A+A/564/A21
Title:
Ammonia observations in G79.29+0.46
Short Name:
J/A+A/564/A21
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of observations of the ammonia (1,1) and (2,2) lines in a field of 7'x7' centered in the LBV ring nebula G79.29+0.46. The survey also includes a significant part of the IRDC G79.3+0.3. Data have been gathered with the 100m radio telescope at Effelsberg. Both lines have been observed simultaneously with excellent spectral resolution. A clump of the IRDC, referred in the paper as the SW region, is sampled every 20"; sampling is 40" elsewhere.