- ID:
- ivo://CDS.VizieR/J/A+A/621/A19
- Title:
- ATESP 5 GHz radio survey. IV.
- Short Name:
- J/A+A/621/A19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is now established that the faint radio population is a mixture of star-forming galaxies and faint active galactic nuclei (AGNs), with the former dominating below S_1.4GHz_~100uJy and the latter at larger flux densities. The faint radio AGN component can itself be separated into two main classes, mainly based on the host-galaxy properties: sources associated with red/early-type galaxies (like radio galaxies) are the dominant class down to ~100uJy; quasar/Seyfert-like sources contribute an additional 10-20%. One of the major open questions regarding faint radio AGNs is the physical process responsible for their radio emission. This work aims at investigating this issue, with particular respect to the AGN component associated with red/early-type galaxies. Such AGNs show, on average, flatter radio spectra than radio galaxies and are mostly compact (<=30kpc in size). Various scenarios have been proposed to explain their radio emission. For instance they could be core/core-jet dominated radio galaxies, low-power BL LACs, or advection dominated accretion flow (ADAF) systems. We used the Australia Telescope Compact Array (ATCA) to extend a previous follow-up multi-frequency campaign to 38 and 94GHz. This campaign focuses on a sample of 28 faint radio sources associated with early-type galaxies extracted from the ATESP 5GHz survey. Such data, together with those already at hand, are used to perform radio spectral and variability analyses. Both analyses can help us to disentangle between core- and jet-dominated sources, as well as to verify the presence of ADAF/ADAF+jet systems. Additional high-resolution observations at 38GHz were carried out to characterise the radio morphology of these sources on kiloparsec scales. Most of the sources (25/28) were detected at 38GHz, while only one (ATESP5J224547-400324) of the twelve sources observed at 94 GHz was detected. From the analysis of the radio spectra we confirmed our previous findings that pure ADAF models can be ruled out. Only eight out of the 28 sources were detected in the 38-GHz high-resolution (0.6 arcsec) radio images and of those eight only one showed a tentative core-jet structure. Putting together spectral, variability, luminosity, and linear size information we conclude that different kinds of sources compose our AGN sample: (a) luminous and large (>=100kpc) classical radio galaxies (~18% of the sample); (b) compact (confined within their host galaxies), low-luminosity, power-law (jet-dominated) sources (~46% of the sample); and (c) compact, flat (or peaked) spectrum, presumably core-dominated, radio sources (~36% of the sample). Variability is indeed preferentially associated with the latter.
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1322. ATESP radio survey. II.
- ID:
- ivo://CDS.VizieR/VIII/63
- Title:
- ATESP radio survey. II.
- Short Name:
- VIII/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ATESP survey is a radio survey accomplished with the Australia Telescope Compact Array (ATCA) at 1.4 GHz over a region of 26 square degrees centered at -40 and ranging in RA from 22h30m to 01h15m. The survey consists of 16 radio mosaics with 8x14 arcsec resolution and uniform sensitivity (1 sigma noise = 79 microJy). The final 6 sigmas catalogue contains 2960 sources down to a detection limit of 0.5 mJy. This region is superposed to the redshift survey ESO Slice Project (ESP) and is partly covered by the EIS survey (Patch A; see Cat. J/A+AS/130/323). Table 3 summarizes the main parameters for the final 16 mosaics: for each mosaic are listed the number of fields composing it (columns x rows), the tangent point (sky position used for geometry calculations) and the synthesized beam (size and position angle). The spatial resolution can vary from mosaic to mosaic depending on the particular array (6A, 6C or 6D) used in the observations. The mean value for the synthesized beam is 8"x14". The last three columns of Table 3 show the results of the noise analysis. For each mosaic we report the minimum (negative) flux (S_min) recorded on the image (typically |S_min| is of the order of 0.5 mJy, corresponding to the value at which we have stopped the cleaning) and the noise level. This has been evaluated either as the FWHM of the Gaussian fit to the flux distribution of the pixels (in the range +/-S_min), in order to check for correlated noise (sigma_fit), or as the standard deviation of the average flux in several source-free sub-regions of the mosaics, in order to verify uniformity (<sigma>).
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/956
- Title:
- AT20G high-angular-resolution catalogue
- Short Name:
- J/MNRAS/434/956
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the high-angular-resolution catalogue for the Australia Telescope 20GHz (AT20G, Cat. J/MNRAS/402/2403) survey, using the high-angular-resolution 6-km antenna data at the baselines of ~4500m of the Australia Telescope Compact Array. We have used the data to produce the visibility catalogue that separates the compact active galactic nuclei (AGNs) from the extended radio sources at the 0.15arcsec angular scale, corresponding to the linear size scale of 1kpc at redshifts higher than 0.7. We find the radio population at 20GHz to be dominated by compact AGNs constituting 77% of the total sources in the AT20G. We introduce the visibility-spectra diagnostic plot, produced using the AT20G cross-matches with lower frequency radio surveys at 1GHz [the NRAO VLA Sky Survey (NVSS, Cat. VIII/65) and the Sydney University Molonglo Sky Survey (SUMSS, Cat. VIII/81)], that separates the 20GHz population into distinct sub-populations of the compact AGNs, the compact steep-spectrum (CSS) sources, the extended AGN-powered sources and extended flat-spectrum sources. The extended flat-spectrum sources include a local thermal emitting population of high-latitude planetary nebulae and also gravitational lens and binary black hole candidates among the AGNs. We find a smooth transition in properties between the CSS sources and the AGN populations. The visibility catalogue, together with the main AT20G survey, provides an estimate of angular size scales for sources in the AT20G and an estimate of the flux arising from central cores of extended radio sources. The identification of the compact AGNs in the AT20G survey provides high-quality calibrators for high-frequency radio telescope arrays and very large baseline interferometry observations.
1324. AT20G-MWACS catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/2717
- Title:
- AT20G-MWACS catalogue
- Short Name:
- J/MNRAS/476/2717
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new broad-band radio frequency catalogue across 0.12GHz<={nu}<=20GHz created by combining data from the Murchison Widefield Array Commissioning Survey, the Australia Telescope 20GHz survey, and the literature. Our catalogue consists of 1285 sources limited by S_20GHz_>40mJy at 5{sigma}, and contains flux density measurements (or estimates) and uncertainties at 0.074, 0.080, 0.119, 0.150, 0.180, 0.408, 0.843, 1.4, 4.8, 8.6, and 20GHz. We fit a second-order polynomial in log-log space to the spectral energy distributions of all these sources in order to characterize their broad-band emission. For the 994 sources that are well described by a linear or quadratic model we present a new diagnostic plot arranging sources by the linear and curvature terms. We demonstrate the advantages of such a plot over the traditional radio colour-colour diagram. We also present astrophysical descriptions of the sources found in each segment of this new parameter space and discuss the utility of these plots in the upcoming era of large area, deep, broad-band radio surveys.
1325. AT20G-optical catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/417/2651
- Title:
- AT20G-optical catalogue
- Short Name:
- J/MNRAS/417/2651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our current understanding of radio-loud active galactic nuclei (AGN) comes predominantly from studies at frequencies of 5GHz and below. With the recent completion of the Australia Telescope 20GHz (AT20G) survey, we can now gain insight into the high-frequency radio properties of AGN. This paper presents supplementary information on the AT20G sources in the form of optical counterparts and redshifts. Optical counterparts were identified using the SuperCOSMOS data base and redshifts were found from either the 6dF Galaxy Survey or the literature. We also report 144 new redshifts. For AT20G sources outside the Galactic plane, 78.5% have optical identifications and 30.9% have redshift information. The optical identification rate also increases with increasing flux density. Targets which had optical spectra available were examined to obtain a spectral classification.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A93
- Title:
- AT 2020hat and AT 2020kog light curves
- Short Name:
- J/A+A/647/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at ~7x10^40^erg/s, while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type IIn supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km/s, along with an Halpha emission with a full-width at half-maximum velocity of 250km/s. For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the Hubble Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of M_F606W=-3.33+/-0.09mag and a colour of F606W-F814W=1.14+/-0.05mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A134
- Title:
- ATHOS. Flux ratio based stellar parameterization
- Short Name:
- J/A+A/619/A134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapidly increasing number of stellar spectra obtained by existing and future large-scale spectroscopic surveys feeds a demand for fast and efficient tools for the spectroscopic determination of fundamental stellar parameters. Such tools should not only comprise customized solutions for one particular survey or instrument, but, in order to enable cross-survey comparability, they should also be capable of dealing with spectra from a variety of spectrographs, resolutions, and wavelength coverages. To meet these ambitious specifications, we developed ATHOS (A Tool for HOmogenizing Stellar parameters), a fundamentally new analysis tool that adopts easy-to-use, computationally inexpensive analytical relations tying flux ratios (FRs) of designated wavelength regions in optical spectra to the stellar parameters effective temperature (Teff), iron abundance ([Fe/H]), and surface gravity (logg). Our Teff estimator is based on FRs from nine pairs of wavelength ranges around the Balmer lines H{beta} and H{alpha}, while for [Fe/H] and logg we provide 31 and 11 FRs, respectively, which are spread between ~4800{AA} and ~6500{AA}; a region covered by most optical surveys. The analytical relations employing these FRs were trained on N=124 real spectra of a stellar benchmark sample that covers a large parameter space of Teff~=4000 to 6500K (spectral types F to K), [Fe/H]~=-4.5 to 0.3dex, and logg~=1 to 5dex, which at the same time reflects ATHOS' range of applicability. We find accuracies of 97K for Teff, 0.16dex for [Fe/H], and 0.26dex for logg, which are merely bounded by finite uncertainties in the training sample parameters. ATHOS' internal precisions can be better by up to 70%. We tested ATHOS on six independent large surveys spanning a wide range of resolutions (R~=2000 to 52000), amongst which are the Gaia-ESO and the SDSS/SEGUE surveys. The exceptionally low execution time (<30ms per spectrum per CPU core) together with a comparison to the literature parameters showed that ATHOS can successfully achieve its main objectives, in other words fast stellar parametrization with cross-survey validity, high accuracy, and high precision. These are key to homogenize the output from future surveys, such as 4MOST or WEAVE.
- ID:
- ivo://CDS.VizieR/J/A+A/632/L6
- Title:
- AT 2018hso light curves and spectra
- Short Name:
- J/A+A/632/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The absolute magnitudes of luminous red novae (LRNe) are intermediate between those of novae and supernovae (SNe), and show a relatively homogeneous spectro-photometric evolution. Although they were thought to derive from core instabilities in single stars, there is growing support for the idea that they are triggered by binary interaction that possibly ends with the merging of the two stars. AT 2018hso is a new transient showing transitional properties between those of LRNe and the class of intermediate-luminosity red transients (ILRTs) similar to SN 2008S. Through the detailed analysis of the observed parameters, our study support that it actually belongs to the LRN class and was likely produced by the coalescence of two massive stars. We obtained ten months of optical and near-infrared photometric monitoring, and 11 epochs of low-resolution optical spectroscopy of AT 2018hso. We compared its observed properties with those of other ILRTs and LRNe. We also inspected the archival Hubble Space Telescope (HST) images obtained about 15 years ago to constrain the progenitor properties. The light curves of AT 2018hso show a first sharp peak (reddening-corrected M_r_=13.93mag), followed by a broader and shallower second peak that resembles a plateau in the optical bands. The spectra dramatically change with time. Early-time spectra show prominent Balmer emission lines and a weak [CaII] doublet, which is usually observed in ILRTs. However, the strong decrease in the continuum temperature, the appearance of narrow metal absorption lines, the great change in the H{alpha} strength and profile, and the emergence of molecular bands support an LRN classification. The possible detection of a M_I_~8mag source at the position of AT 2018hso in HST archive images is consistent with expectations for a pre-merger massive binary, similar to the precursor of the 2015 LRN in M101. We provide reasonable arguments to support an LRN classification for AT 2018hso. This study reveals growing heterogeneity in the observables of LRNe than has been thought previously, which is a challenge for distinguishing between LRNe and ILRTs. This suggests that the entire evolution of gap transients needs to be monitored to avoid misclassifications.
- ID:
- ivo://CDS.VizieR/J/ApJ/867/105
- Title:
- ATLAS all-sky stellar ref. catalog, ATLAS-REFCAT2
- Short Name:
- J/ApJ/867/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Asteroid Terrestrial-impact Last Alert System (ATLAS) observes most of the sky every night in search of dangerous asteroids. Its data are also used to search for photometric variability, where sensitivity to variability is limited by photometric accuracy. Since each exposure spans 7.6{deg} corner to corner, variations in atmospheric transparency in excess of 0.01mag are common, and 0.01mag photometry cannot be achieved by using a constant flat-field calibration image. We therefore have assembled an all-sky reference catalog of approximately one billion stars to m~19 from a variety of sources to calibrate each exposure's astrometry and photometry. Gaia DR2 is the source of astrometry for this ATLAS Refcat2. The sources of g, r, i, and z photometry include Pan-STARRS DR1, the ATLAS Pathfinder photometry project, ATLAS reflattened APASS data, SkyMapper DR1, APASS DR9, the Tycho-2 catalog, and the Yale Bright Star Catalog. We have attempted to make this catalog at least 99% complete to m<19, including the brightest stars in the sky. We believe that the systematic errors are no larger than 5mmag rms, although errors are as large as 20mmag in small patches near the Galactic plane.
- ID:
- ivo://CDS.VizieR/VII/244A
- Title:
- Atlas and Catalog of Dark Clouds
- Short Name:
- VII/244A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Here we release the first version of the atlas and catalog of dark clouds derived by using the optical database Digitized Sky Survey I (DSS). Applying a traditional star-count technique to 1043 plates contained in DSS, we have produced an Av map covering the entire region in the galactic latitude range |b|=<40{deg}. The map was drawn at two different angular resolutions of 6' and 18', and is released in FITS format. Based on the Av map, we identified 2448 dark clouds and 2841 clumps located inside them. Physical parameters, such as the position, extent, and optical extinction, were measured for each of the clouds and clumps. We also searched for counterparts among already known dark clouds in the literature. The catalog of dark clouds presented here lists the cloud parameters as well as the counterparts. Printed version of the atlas and catalog was published in a special issue of Publications of the Astronomical Society of Japan (PASJ) in February 2005 (Dobashi et al., 2005, PASJ, 57, pp.S1-S386).
