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681. 4.85 GHz fluxes of H II regions
ID:
ivo://CDS.VizieR/J/ApJ/488/224
Title:
4.85 GHz fluxes of H II regions
Short Name:
J/ApJ/488/224
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an all-sky flux catalog of 760 H II regions with angular sizes ranging up to 10' at 4.85GHz. The data were compiled in a self-consistent manner from existing images of the Green Bank and Parkes-MIT-NRAO 4.85GHz radio continuum surveys. Nearly 35% of these H II regions have fluxes measured from these surveys for the first time. We compared our results to the previously published source catalogs which fit the same data. The new flux measurements agree within 5%-7% of these values and fall well within the formal errors. The diameters fall within 16% of the previously published fits to the same data, within the formal uncertainties of these values.
682. 1.4 GHz imaging of the Bootes field
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).
683. 6.7GHz methanol maser emission survey
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.
684. 6-GHz methanol multibeam maser catalogue
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.
685. 1.4GHz NRAO VLA Sky Survey (NVSS)
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.
686. 1.4GHz observations of Stripe 82
ID:
ivo://CDS.VizieR/J/AJ/142/3
Title:
1.4GHz observations of Stripe 82
Short Name:
J/AJ/142/3
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a high-resolution radio survey of the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a.k.a. Stripe 82. This 1.4GHz survey was conducted with the Very Large Array primarily in the A-configuration, with supplemental B-configuration data to increase sensitivity to extended structure. The survey has an angular resolution of 1.8" and achieves a median rms noise of 52{mu}Jy/beam over 92deg^2^. This is the deepest 1.4GHz survey to achieve this large of an area, filling a gap in the phase space between small, deep and large, shallow surveys. It also serves as a pilot project for a larger high-resolution survey with the Expanded Very Large Array. We discuss the technical design of the survey and details of the observations, and we outline our method for data reduction. We present a catalog of 17969 isolated radio components, for an overall source density of ~195sources/deg^2^. The astrometric accuracy of the data is excellent, with an internal check utilizing multiply observed sources yielding an rms scatter of 0.19" in both right ascension and declination. A comparison to the SDSS-DR7 Quasar Catalog further confirms that the astrometry is well tied to the optical reference frame, with mean offsets of 0.02+/-0.01" in right ascension, and 0.01+/-0.02" in declination. A check of our photometry reveals a small, negative CLEAN-like bias on the level of 35{mu}Jy. We report on the catalog completeness, finding that 97% of FIRST-detected quasars are recovered in the new Stripe 82 radio catalog, while faint, extended sources are more likely to be resolved out by the resolution bias. We conclude with a discussion of the optical counterparts to the catalog sources, including 76 newly detected radio quasars.
687. 90GHz obs. of high-mass star-forming regions
ID:
ivo://CDS.VizieR/J/ApJ/777/157
Title:
90GHz obs. of high-mass star-forming regions
Short Name:
J/ApJ/777/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
The chemical changes of high-mass star-forming regions provide a potential method for classifying their evolutionary stages and, ultimately, ages. In this study, we search for correlations between molecular abundances and the evolutionary stages of dense molecular clumps associated with high-mass star formation. We use the molecular line maps from Year 1 of the Millimetre Astronomy Legacy Team 90GHz (MALT90) Survey. The survey mapped several hundred individual star-forming clumps chosen from the ATLASGAL survey to span the complete range of evolution, from prestellar to protostellar to H II regions. The evolutionary stage of each clump is classified using the Spitzer GLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dust temperatures and H_2_ column densities for each clump from Herschel/Hi-GAL continuum data. From MALT90 data, we measure the integrated intensities of the N_2_H^+^, HCO^+^, HCN and HNC(1-0) lines, and derive the column densities and abundances of N_2_H^+^ and HCO^+^. The Herschel dust temperatures increase as a function of the IR-based Spitzer evolutionary classification scheme, with the youngest clumps being the coldest, which gives confidence that this classification method provides a reliable way to assign evolutionary stages to clumps. Both N_2_H^+^ and HCO^+^ abundances increase as a function of evolutionary stage, whereas the N_2_H^+^(1-0) to HCO^+^(1-0) integrated intensity ratios show no discernable trend. The HCN(1-0) to HNC(1-0) integrated intensity ratios show marginal evidence of an increase as the clumps evolve.
688. 1.4GHz radio variability in FIRST & SDSS Stripe 82
ID:
ivo://CDS.VizieR/J/ApJ/769/125
Title:
1.4GHz radio variability in FIRST & SDSS Stripe 82
Short Name:
J/ApJ/769/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on a blind survey for extragalactic radio variability that was carried out by comparing two epochs of data from the Faint Images of the Radio Sky at Twenty centimeters survey with a third epoch from a new 1.4GHz survey of SDSS Stripe 82. The three epochs are spaced seven years apart and have an overlapping area of 60deg^2^. We uncover 89 variable sources down to the millijansky level, 75 of which are newly identified, and we find no evidence for transient phenomena. This new sample of variable sources allows us to infer an upper limit to the mean characteristic timescale of active galactic nucleus radio variability of 14yr. We find that only 1% of extragalactic sources have fractional variability f_var_>3, while 44% of Galactic sources vary by this much. The variable sample contains a larger fraction of quasars than a comparable non-variable control sample, though the majority of the variable sources appear to be extended galaxies in the optical. This implies that either quasars are not the dominant contributor to the variability of the sample, or that the deep optical data allow us to detect the host galaxies of some low-z quasars. We use the new, higher resolution data to report on the morphology of the variable sources. Finally, we show that the fraction of sources that are variable remains constant or increases at low flux densities. This may imply that next generation radio surveys with telescopes like Australian Square Kilometer Array Pathfinder and MeerKAT will see a constant or even increasing fraction of variable sources down into the sub-millijansky regime.
689. 1.1-1.9GHz SETI survey of KOIs. I.
ID:
ivo://CDS.VizieR/J/ApJ/767/94
Title:
1.1-1.9GHz SETI survey of KOIs. I.
Short Name:
J/ApJ/767/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a targeted search for narrow-band (<5Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380K>T_eq_>230K, stars with five or more detected candidates or stars with a super-Earth (R_p_<3R_{earth}_) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2GHz at an equivalent isotropically radiated power (EIRP) of ~1.5x10^21^erg/s, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10^-6^/M_{sun}_. Here we describe our observations, data reduction procedures and results.
690. 31GHz sky survey with the SZA
ID:
ivo://CDS.VizieR/J/ApJ/716/521
Title:
31GHz sky survey with the SZA
Short Name:
J/ApJ/716/521
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first sample of 31GHz selected sources to flux levels of 1mJy. From late 2005 to mid-2007, the Sunyaev-Zel'dovich Array observed 7.7deg^2^ of the sky at 31GHz to a median rms of 0.18mJy/beam. We identify 209 sources at greater than 5{sigma} significance in the 31GHz maps, ranging in flux from 0.7mJy to ~200mJy. Archival NVSS data at 1.4GHz and observations at 5GHz with the Very Large Array are used to characterize the sources. We determine the maximum-likelihood integrated source count to be N(>S)=(27.2+/-2.5)deg^-2^x(S_mJy_)^-1.18+/-0.12^ over the flux range 0.7-15mJy. This result is significantly higher than predictions based on 1.4GHz selected samples, a discrepancy which can be explained by a small shift in the spectral index distribution for faint 1.4GHz sources. From comparison with previous measurements of sources within the central arcminute of massive clusters, we derive an overdensity of 6.8+/-4.4, relative to field sources.