- ID:
- ivo://CDS.VizieR/J/ApJ/869/66
- Title:
- Search for extraterrestrial intelligence with ATA
- Short Name:
- J/ApJ/869/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a novel radio autocorrelation search for extraterrestrial intelligence. For selected frequencies across the terrestrial microwave window (1-10GHz), observations were conducted at the Allen Telescope Array to identify artificial non-sinusoidal periodic signals with radio bandwidths greater than 4Hz, which are capable of carrying substantial messages with symbol rates from 4 to 10^6^Hz. Out of 243 observations, about half (101) were directed toward sources with known continuum flux >~1Jy over the sampled bandwidth (quasars, pulsars, supernova remnants, and masers), based on the hypothesis that they might harbor heretofore undiscovered natural or artificial repetitive, phase or frequency modulation. The rest of the observations were directed mostly toward exoplanet stars with no previously discovered continuum flux. No signals attributable to extraterrestrial technology were found in this study. We conclude that the maximum probability that future observations like the ones described here will reveal repetitively modulated emissions is less than 5% for continuum sources and exoplanets alike. The paper concludes by describing a new approach to expanding this survey to many more targets and much greater sensitivity using archived data from interferometers all over the world.
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- ID:
- ivo://CDS.VizieR/J/ApJ/695/276
- Title:
- Search for megamasers in type-2 AGNs
- Short Name:
- J/ApJ/695/276
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a search for H_2_O megamasers in 274 SDSS type-2 active galactic nuclei (AGNs; 0.3<z<0.83), half of which can be classified as type-2 quasi-stellar objects (QSOs) from their [OIII]5007 luminosity, using the Robert C. Byrd Green Bank Telescope (GBT) and the Effelsberg 100m radio telescope. Apart from the detection of the extremely luminous water vapor megamaser SDSS J080430.99+360718.1, already reported by Barvainis & Antonucci (2005ApJ...628...89B), we do not find any additional line emission. This high rate of nondetections is compared to the water maser luminosity function created from the 78 water maser galaxies known to date and its extrapolation toward the higher luminosities of "gigamasers" that we would have been able to detect given the sensitivity of our survey. The properties of the known water masers are summarized and discussed with respect to the nature of high-z type-2 AGNs and megamasers in general. In the Appendix (tables 4 and 5), we list 173 additional objects (mainly radio galaxies, but also QSOs and galaxies) that were observed with the GBT, the Effelsberg 100m radio telescope, or Arecibo Observatory without leading to the detection of water maser emission.
- ID:
- ivo://CDS.VizieR/VI/151
- Title:
- Search for radio emission from giant exoplanets
- Short Name:
- VI/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The intensity of Jupiter's auroral radio emission quickly gave rise to the question whether a comparable coherent emission from the magnetosphere of an exoplanet could be detectable. An exoplanetary radio emission would have to be at least 1000 times more intense than Jupiter's emission to be detectable with current radio telescopes. Theoretical models suggest that, at least in certain cases, the radio emission of giant exoplanets may indeed reach the required intensity. At the same time, in order to generate such an emission, an exoplanet would have to have a sufficiently strong intrinsic planetary magnetic field. Extrasolar planets are indeed expected to have a planetary magnetic field, but to date, their magnetic field has never been detected. We will show that the most promising technique to observe exoplanetary magnetic fields is indeed to search for the planetary auroral radio emission. The detection of such an emission would thus constitute the first unambiguous detection of an exoplanetary magnetic field. We will review recent theoretical studies and discuss their results for the two main parameters, namely the maximum emission frequency and the intensity of the radio emission. The predicted values should allow the detection using modern low-frequency radio telescopes. We will present an ongoing observation program with the Low Frequency Array (LOFAR), which has the potential to detect exoplanetary radio emission.
- ID:
- ivo://CDS.VizieR/J/ApJS/95/345
- Title:
- Second Caltech-Jodrell Bank VLBI Survey. I.
- Short Name:
- J/ApJS/95/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We define the sample for the second Caltech-Jodrell Bank VLBI survey. This is a sample of 193 flat- or gigahertz-peaked-spectrum sources selected at 4850 MHz. This paper presents images of 91 sources with a resolution of ~1 mas, obtained using VLBI observations at 4992 MHz with a global array. The remaining images and the integrated radio spectra will be presented in a forthcoming paper by Henstock et al.
- ID:
- ivo://CDS.VizieR/J/AJ/151/154
- Title:
- Second epoch VLBA Calibrator Survey (VCS-II)
- Short Name:
- J/AJ/151/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Six very successful Very Long Baseline Array (VLBA) calibrator survey campaigns were run between 1994 and 2007 to build up a large list of compact radio sources with positions precise enough for use as very long baseline interferometry (VLBI) phase reference calibrators. We report on the results of a second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS sources were re-observed in the X and S bands in order to improve the upcoming third realization of the International Celestial Reference Frame (ICRF3) as well as to improve their usefulness as VLBI phase reference calibrators. In this survey, some 2062 previously detected sources and 324 previously undetected sources were detected and revised positions are presented. Average position uncertainties for the re-observed sources were reduced from 1.14 and 1.98mas to 0.24 and 0.41mas in R.A. and decl., respectively, or by nearly a factor of 5. Minimum detected flux values were approximately 15 and 28mJy in the X and S bands, respectively, and median total fluxes are approximately 230 and 280mJy. The vast majority of these sources are flat-spectrum sources, with ~82% having spectral indices greater than -0.5.
- ID:
- ivo://CDS.VizieR/J/A+AS/147/187
- Title:
- Second list of the Karachentsev catalog
- Short Name:
- J/A+AS/147/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 presents the results of HI observations of 78 'nearby dwarf galaxies' from Karachentseva et al. (1999A&AS..135..221K) obtained with the 100-m radio telescope at Effelsberg. This survey covers an area limited by R.A.[14h,23h30] and Dec[-20d,+60d] including the nearest cosmic void : R.A.[18h38m], Dec[+18d], V_0_<1500km/s.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2562
- Title:
- Second VLBA calibrator survey: VCS2
- Short Name:
- J/AJ/126/2562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents an extension of the Very Long Baseline Array Calibrator Survey, called VCS2, containing 276 sources. This survey fills in regions of the sky that were not completely covered by the previous VCS1 calibrator survey. The VCS2 survey includes calibrator sources near the Galactic plane, -30{deg}<DE<-45{deg}, and VLA calibrators. The positions have been derived from astrometric analysis of the group delays measured at 2.3 and 8.4 GHz using the Goddard Space Flight Center CALC/SOLVE package. From the VLBA snapshot observations, images of the calibrators are available, and each source is given a quality code for anticipated use. The VCS2 catalog is available from the NRAO Web site.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A160
- Title:
- SEDIGISM survey, search for molecular outflows
- Short Name:
- J/A+A/658/A160
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The formation processes of massive stars are still unclear but a picture is emerging involving accretion disks and molecular outflows in what appears to be a scaled-up version of lower-mass star formation. A census of outflow activity towards high-mass star-forming clumps in various evolutionary stages has the potential to shed light on high-mass star formation. We conduct an outflow survey toward ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) clumps, using SEDIGISM (structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) data and aim to obtain a large sample of clumps exhibiting outflow activity in different evolutionary stages. We identify the high-velocity wings of the ^13^CO lines, indicating outflow activity, toward ATLASGAL clumps by (1) extracting the simultaneously observed ^13^CO(2-1) and C^18^O(2-1) spectra from SEDIGISM, and (2) subtracting the scaled C^18^O (cores emission) from the ^13^CO, after considering opacity broadening. We have detected high-velocity gas towards 1192 clumps out of a total sample of 2052 corresponding to an overall detection rate of 58%. Outflow activity has been detected from the earliest (apparently) quiescent clumps (i.e., 70 microns weak), to the most evolved HII region stages (i.e., 8 micron bright with tracers of massive star formation). The detection rate increases as a function of evolution (quiescent = 51%, protostellar = 47%, YSO = 57%, UCHII regions = 76%). Our sample is the largest outflow sample identified so far. The high detection rate from this large sample is consistent with the results of similar studies reported in the literature and supports the scenario that outflows are a ubiquitous feature of high-mass star formation. The lower detection rate in early evolutionary stages could be due to the fact that outflows in the early stages are weak and difficult to detect. We obtain a statistically significant number of outflow clumps for every evolutionary stage, especially for outflow clumps in the earliest stages (i.e., 70 microns dark cloud or massive starless core).
- ID:
- ivo://CDS.VizieR/J/ApJ/694/992
- Title:
- SED of cluster radio galaxies
- Short Name:
- J/ApJ/694/992
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To explore the high-frequency radio spectra of galaxies in clusters, we used NRAO's Very Large Array at four frequencies, 4.9-43GHz, to observe 139 galaxies in low redshift (z<0.25), X-ray detected, clusters. The clusters were selected from the survey conducted by Ledlow and Owen (1997ApJS..108...41O), who provided redshifts and 1.4GHz flux densities for all the radio sources. We find that more than half of the observed sources have steep microwave spectra as generally expected ({alpha}<-0.5, in the convention S{proto}{nu}^{alpha}^). However, 60%-70% of the unresolved or barely resolved sources have flat or inverted spectra. Most of these show an upward turn in flux at {nu}>22GHz, implying a higher flux than would be expected from an extrapolation of the lower-frequency flux measurements. Our results quantify the need for careful source subtraction in increasingly sensitive measurements of the Sunyaev-Zel'dovich effect in clusters of galaxies (as currently being conducted by, for instance, the Atacama Cosmology Telescope and South Pole Telescope groups).
- ID:
- ivo://CDS.VizieR/J/ApJ/716/30
- Title:
- SED of Fermi bright blazars
- Short Name:
- J/ApJ/716/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a detailed investigation of the broadband spectral properties of the {gamma}-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS, Cat. J/ApJ/700/597). By combining our accurately estimated Fermi {gamma}-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/{gamma}-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, {alpha}_ro_, and optical to X-ray, {alpha}_ox_, spectral slopes) and from the {gamma}-ray spectral index. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright broad-lined flat spectrum radio quasars (FSRQs) and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter {gamma}-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple synchrotron self-Compton (SSC) models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study.