- ID:
- ivo://CDS.VizieR/J/AJ/123/1784
- Title:
- 1.4 GHz imaging of the Bootes field
- Short Name:
- J/AJ/123/1784
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from our deep (16x12hr) Westerbork Synthesis Radio Telescope (WSRT) observations of the approximately 7{deg}^2^ Bootes Deep Field, centered at 14h 32min 05.75s, 34{deg} 16' 47.5" (J2000.0). Our survey consists of 42 discrete pointings, with enough overlap to ensure a uniform sensitivity across the entire field, with a limiting sensitivity of 28{mu}Jy (1{sigma}_rms_). The catalog contains 3172 distinct sources, of which 316 are resolved by the 13"x27" beam. The Bootes field is part of the optical/near-infrared imaging and spectroscopy survey effort conducted at various institutions. The combination of these data sets and the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the K-z relation, the clustering environment of radio galaxies, the radio/far-infrared correlation for distant starbursts, and the nature of obscured radio-loud active galactic nuclei. The observations were carried out by the WSRT operating at 1.380GHz. The WSRT consists of 14 25m-telescopes arranged in a 2.7km east-west configuration. As the back end, we used the digital continuum back end with eight subbands of 10MHz bandwidth each. The smallest baseline (9-A) was set to 54m to limit shadowing at the expense of a reduction in large spatial structure sensitivity (~800" for this minimum baseline and frequency).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/143/269
- Title:
- 6.7GHz methanol maser emission survey
- Short Name:
- J/A+AS/143/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results of a search for 6.7GHz methanol masers in the direction of 1399 IRAS objects north of declination -20{deg} with the flux densities greater than 100 Jy at 60 {mu}m and the flux density ratio F_60_/F_25_>1. Observations were made with the sensitivity of 1.7 Jy and the velocity resolution of 0.04km/s using the 32-m Torun radio telescope. Maser emission was found in 182 sources, including 70 new detections. 32 new sources were identified with objects of radio emission associated with star-forming regions. Comparison of the present data set with other observations suggests that about 65% of methanol masers exhibit moderate or strong variations on time-scales of about 4 and 8 years.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/219
- Title:
- 6.7 GHz methanol masers observations
- Short Name:
- J/MNRAS/474/219
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results of 6.7GHz methanol maser monitoring of 139 star-forming sites with the Torun 32-m radio telescope from 2009 June to 2013 February. The targets were observed at least once a month, with higher cadences of two to four measurements per week for circumpolar objects. Nearly 80 per cent of the sources display variability greater than 10 per cent on a time-scale between a week and a few years, but about three quarters of the sample have only one to three spectral features that vary significantly. Irregular intensity fluctuation is the dominant type of variability and only nine objects show evidence for cyclic variations with periods of 120 to 416d. Synchronized and anticorrelated variations of maser features are detected in four sources with a disc-like morphology. Rapid and high-amplitude bursts of individual features are seen on three to five occasions in five sources. Long (>50d to 20 months) lasting bursts are observed mostly for individual or groups of features in 19 sources and only one source experienced a remarkable global flare. A few flaring features display a strong anticorrelation between intensity and line-width that is expected for unsaturated amplification. There is a weak anticorrelation between the maser feature luminosity and variability measure, i.e. maser features with low luminosity tend to be more variable than those with high luminosity. The analysis of the spectral energy distribution and continuum radio emission reveals that the variability of the maser features increases when the bolometric luminosity and Lyman flux of the exciting object decreases. Our results support the concept of a major role for infrared pumping photons in triggering outburst activity of maser emission.
- ID:
- ivo://CDS.VizieR/J/A+A/403/1095
- Title:
- 6.7GHz methanol masers survey of low-mass YSO
- Short Name:
- J/A+A/403/1095
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a search for 6.7-GHz methanol masers toward low-mass young stellar objects (YSOs) and (pre)protostellar condensations with the Australia Telescope Compact Array (ATCA). Our sample consisted of 13 class 0 protostars and 44 class I YSOs as well as 66 (pre)protostellar condensations. A single detection was obtained toward NGC 2024: FIR4 in the Orion B region. This is the first detection of a 6.7-GHz methanol maser in Orion. The nature of FIR4 has been a subject of debate with some evidence suggesting that it is a very cold high-mass (pre)protostellar condensation and others arguing that it is a low-mass YSO. The discovery of a methanol maser associated with this source is inconsistent with both of these hypotheses and we suggest that FIR4 probably harbours an intermediate- or high-mass YSO.
- ID:
- ivo://CDS.VizieR/VIII/96
- Title:
- 6-GHz methanol multibeam maser catalogue
- Short Name:
- VIII/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a Galactic plane survey of methanol masers at 6668 MHz using a seven-beam receiver on the Parkes telescope, refered to as MX observations. Paper I provides sensitive unbiased coverage of a large region around the Galactic Centre. Details are given for 183 methanol maser sites in the longitude range 345{deg} through the Galactic Centre to 6{deg}. Within 6{deg} of the Galactic Centre, we found 88 maser sites, of which more than half (48) are new discoveries. The masers are confined to a narrow Galactic latitude range, indicative of many sources at the Galactic Centre distance and beyond, and confined to a thin disc population; there is no high-latitude population that might be ascribed to the Galactic bulge. Paper II spans the longitude range 6{deg} to 20{deg}. We report the detection of 119 maser sources, of which 42 are new discoveries. Paper III covers the longitude range 330{deg}-345{deg}, yielding 198 masers, of which more than 40 per cent are new discoveries. Paper IV span the longitude range 186{deg}-330{deg}. We report 207 maser detections, 89 new to the survey. This completes the southern sky part of the methanol multibeam survey and includes a large proportion of new sources, 43 per cent. We also include results from blind observations of the Orion-Monoceros star-forming region, formally outside the latitude range of the methanol multibeam survey; only the four previously known methanol emitting sites were detected, of which we present new positions and spectra for masers at Orion A (south) and Orion B, obtained with the Multi-Element Radio Linked Interferometer Network (MERLIN) array.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3718
- Title:
- 15GHz monitoring of AGN jets with VLBA
- Short Name:
- J/AJ/137/3718
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present images from a long-term program (MOJAVE: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments) to survey the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky. The observations consist of 2424 15GHz Very Long Baseline Array (VLBA) images of a complete flux-density-limited sample of 135 AGNs above declination -20{deg}, spanning the period 1994 August to 2007 September. These data were acquired as part of the MOJAVE and 2cm Survey programs, and from the VLBA archive. The sample-selection criteria are based on multi-epoch parsec-scale (VLBA) flux density, and heavily favor highly variable and compact blazars. The sample includes nearly all the most prominent blazars in the northern sky, and is well suited for statistical analysis and comparison with studies at other wavelengths. Our multi-epoch and stacked-epoch images show 94% of the sample to have apparent one-sided jet morphologies, most likely due to the effects of relativistic beaming. Of the remaining sources, five have two-sided parsec-scale jets, and three are effectively unresolved by the VLBA at 15GHz, with essentially all of the flux density contained within a few tenths of a milliarcsecond.
- ID:
- ivo://CDS.VizieR/VIII/65
- Title:
- 1.4GHz NRAO VLA Sky Survey (NVSS)
- Short Name:
- VIII/65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The NRAO VLA Sky Survey (NVSS) is a radio continuum survey covering the sky north of -40{deg} declination at 1.4GHz. The principal data products of the NVSS are a set of 2326 4x4{deg} continuum "cubes" with three planes containing Stokes I, Q, and U images, plus a catalog of almost 2 million discrete sources stronger than a flux density of about 2.5mJy. The images all have 45 arcsecond FWHM angular resolution and nearly uniform sensitivity. Their rms brightness fluctuations are approximately 0.45mJy/beam=0.14K (Stokes I) and 0.29mJy/beam=0.09K (Stokes Q and U). The rms uncertainties in right ascension and declination vary from <= ~1arcsecond for the 400,000 sources stronger than 15mJy to 7arcseconds at the survey limit. A more detailed description is provided in the printed paper and at the NVSS website at http://www.cv.nrao.edu/nvss/ where all data products, user software, and updates were released as soon as they were produced and verified.
- ID:
- ivo://CDS.VizieR/J/A+A/559/A75
- Title:
- 43GHz observation of the blazar Mrk 421
- Short Name:
- J/A+A/559/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results obtained for the AGN Markarian 421 by model-fitting the data in the visibility plane, studing the proper motion of jet components, the light curve, and the spectral index of the jet features. We compare the radio data with optical light curves obtained at the Steward Observatory, considering also the optical polarization information. Mrk 421 has a bright nucleus and a one-sided jet extending towards the north-west for a few parsecs. The model-fits show that brightness distribution is well described using 6-7 circular Gaussian components, four of which are reliably identified at all epochs; all components are effectively stationary except for component D, at ~0.4mas from the core, whose motion is however subluminal. The analysis of the light curve shows two different states, with the source being brighter and more variable in the first half of 2011 than in the second half. The highest flux density is reached in February. A comparison with the optical data reveals an increase of the V magnitude and of the fractional polarization simultaneous with the enhancement of the radio activity.
- ID:
- ivo://CDS.VizieR/J/ApJ/655/958
- Title:
- 90-GHz observations in NGC 1333
- Short Name:
- J/ApJ/655/958
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the clustered star forming complex NGC 1333 with the BIMA and FCRAO telescopes in the transitions HCO+(1-0) and N_2_H+(1-0) over an area with resolution ~10" (0.015pc). The N_2_H+ emission follows very closely the submillimeter dust continuum emission, while HCO+ emission appears more spatially extended and also traces outflows. We have identified 93 N_2_H+ cores using the CLUMPFIND algorithm, and we derive N_2_H+ core masses between 0.05 and 2.5M_{sun}_ , with uncertainties of a factor of a few, dominated by the adopted N_2_H+ abundance.
- ID:
- ivo://CDS.VizieR/J/ApJS/51/67
- Title:
- 5 GHz Observations of Arecibo 611 MHz Sources
- Short Name:
- J/ApJS/51/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Arecibo 611 MHz survey of Durdin et al. (1975) listed 3118 radio sources stronger than 0.35 Jy in the region -3d to +19d and 22h to 13h. Of these sources, 2911 have been observed using the NRAO 300 foot transit telescope at 4755 MHz. Positions, fluxes, and spectral indices are given for the 2661 detected sources. The beamwidth of the 300 foot telescope is nominally 2.8 arcmin FWHM at 6 cm, compared to the 12 arcmin beamwidth of the Arecibo survey, allowing a significant improvement in source positions.
