- ID:
- ivo://CDS.VizieR/J/MNRAS/452/3969
- Title:
- ATCA Survey of Sagittarius B2 at 7mm
- Short Name:
- J/MNRAS/452/3969
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 30-50GHz survey of Sagittarius B2(N) conducted with the Australia Telescope Compact Array (ATCA) with 5 - 10 arcsec resolution. We analyze the spectra towards three HII regions that have foreground molecular gas in Sgr B2. Towards the most line-dense region, we detect >500 spectral line components, >90% of which are assigned to H and He recombination lines and 53 firmly identified molecular species (not including isotopologues). The data reveal extremely subthermally excited molecular gas in Sgr B2 absorbing against the continuum background, as well as molecular line emission from two hot cores in Sgr B2(N). They also also contain line-of-sight absorption by ~15 molecules observed in translucent gas in the Galactic Center, bar, and intervening spiral arm clouds, revealing the complex chemistry and clumpy structure of this gas. Formamide (NH_2_CHO) is detected for the first time in a translucent cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/124/509
- Title:
- ATCA/VLA OH 1612 MHz survey. II.
- Short Name:
- J/A+AS/124/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the region between -45{deg}<=l<=-10{deg} and |b|<=3{deg} in the OH 1612.231MHz line, taken in 1994 January with the Australia Telescope Compact Array (ATCA). These observations are part of a larger survey, covering |l|<=45{deg} and |b|<=3{deg}, with the ATCA and the Very Large Array. In a previous article we have discussed the observational strategy in detail. In this paper we present only the objects found in this part of the survey. The region was systematically searched for OH-maser emission and was covered completely with 910 pointing centres separated by 30'. We found 202 OH-masing objects, 112 of which are new detections. Out of the 202 objects, 166 have a standard double-peaked spectral profile, 32 a single-peaked profile and 4 objects have non-standard or irregular profiles. In this article we analyse the data statistically and give classifications and identifications with known sources where possible. The astrophysical, kinematical, morphological and dynamical properties of subsets of the data will be addressed in future articles.
- ID:
- ivo://CDS.VizieR/J/A+A/366/481
- Title:
- ATCA/VLA OH 1612 MHz survey. III.
- Short Name:
- J/A+A/366/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observations of the region between 5{deg}<=l<=45{deg} and |b|<=3{deg}, in the OH 1612.231MHz line, taken from 1993 to 1995 with NRAO's Very Large Array (VLA). These observations are the last part of a larger survey, covering |l|<=45{deg} and |b|<=3{deg}, with the Australia Telescope Compact Array (ATCA) and the VLA. The region was systematically observed on a 30'x30' grid in (l,b) and the resulting coverage was 92%, with 965 pointings. We found 286 OH-masing objects, 161 of which are new detections and 207 have reliable IRAS point-source identifications. The outflow velocity was determined for 276 sources. A total of 766 sources were detected in the combined ATCA/VLA survey, of which 29 were detected in two regions of the survey.
- ID:
- ivo://CDS.VizieR/J/A+A/457/517
- Title:
- ATESP 5 GHz radio survey. I.
- Short Name:
- J/A+A/457/517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature and evolutionary properties of the faint radio population, responsible for the steepening observed in the 1.4GHz source counts below 1mJy, are not yet entirely clear. Radio spectral indices may help to constrain the origin of the radio emission in such faint radio sources and may be fundamental in understanding eventual links to the optical light. We study the spectral index behaviour of sources that were found in the 1.4GHz ATESP survey (Prandoni et al., 2000A&AS..146...31P & 2000, Cat. <VIII/63>), considering that the ATESP is one of the most extensive sub-mJy surveys existing at present. Using the Australia Telescope Compact Array we observed at 5GHz part of the region covered by the sub-mJy ATESP survey. In particular we imaged a one square degree area for which deep optical imaging in UBVRIJK is available. In this paper we present the 5GHz survey and source catalogue, we derive the 5GHz source counts and we discuss the 1.4-5GHz spectral index properties of the ATESP sources. The analysis of the optical properties of the sample will be the subject of a following paper.
- 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.
1316. 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.
1318. 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.
1319. 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.
