- ID:
- ivo://CDS.VizieR/J/A+A/628/A56
- Title:
- Extragalactic MHz Peaked Sources at mas scales
- Short Name:
- J/A+A/628/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extragalactic peaked-spectrum radio sources are thought to be the progenitors of larger, radio-loud active galactic nuclei (AGN). Synchrotron self-absorption (SSA) has often been identified as the cause of their spectral peak. The identification of new megahertz-peaked spectrum sources from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey provides an opportunity to test how radio sources with spectral peaks below 1GHz fit within this evolutionary picture. We observed six peaked-spectrum sources selected from the GLEAM survey, three that have spectral characteristics which violate SSA and three that have spectral peaks below 230MHz, with the Very Long Baseline Array at 1.55 and 4.96 GHz. We present milliarcsecond resolution images of each source and constrain their morphology, linear size, luminosity, and magnetic field strength. Of the sources that are resolved by our study, the sources that violate SSA appear to be compact doubles, while the sources with peak frequencies below 230MHz have core-jet features. We find that all of our sources are smaller than expected from SSA by factors of >~20. We also find that component magnetic field strengths calculated from SSA are likely inaccurate, differing by factors of >~5 from equipartition estimates. The calculated equipartition magnetic field strengths more closely resemble estimates from previously studied gigahertz-peaked spectrum sources. Exploring a model of the interaction between jets and the interstellar medium, we demonstrate that free-free absorption (FFA) can accurately describe the linear sizes and peak frequencies of our sources. Our findings support the theory that there is a fraction of peaked-spectrum sources whose spectral peaks are best modelled by FFA, implying our understanding of the early stages of radio AGN is incomplete.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/836/174
- Title:
- Extragalactic peaked-spectrum radio sources
- Short Name:
- J/ApJ/836/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 1483 sources that display spectral peaks between 72MHz and 1.4GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift (z>2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1GHz.
- ID:
- ivo://CDS.VizieR/J/ApJ/694/222
- Title:
- Extragalactic point sources in WMAP 5-yr maps
- Short Name:
- J/ApJ/694/222
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an extragalactic point source search using the five-year Wilkinson Microwave Anisotropy Probe (WMAP) 41, 61, and 94GHz (Q, V, and W bands) temperature maps. This work is an extension of our designing and applying a cosmic microwave background (CMB)-free technique to extract point sources in the WMAP maps. Specifically, we have formed an internal linear combination map of the three-band maps, with the weights chosen to remove the CMB anisotropy signal as well as to favor the selection of flat-spectrum sources. We have also constructed a filter to recover the true point source flux distribution on the sky. A total of 381 sources are found in our study at the >5{sigma} level outside the WMAP point source detection mask, among which 89 are "new" (i.e., not present in the WMAP catalogs). Source fluxes have been calculated and corrected for the Eddington bias. We have solidly identified 367 (96.3%) of our sources, the 1{sigma} positional uncertainty of which is 2'. The 14 unidentified sources could be either extended radio structure or obscured by Galactic emission. We have also applied the same detection approach to simulated maps, which yielded 364+/-21 detections on average. The recovered source distribution N(>S) agrees well with the simulation input, which proves the reliability of this method.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/747
- Title:
- Extragalactic point-source WMAP catalog
- Short Name:
- J/ApJ/681/747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of an extragalactic point-source search using the 61 and 94GHz (V- and W-band) temperature maps from the Wilkinson Microwave Anisotropy Probe (WMAP). Applying a method that cancels the "noise" due to the CMB anisotropy signal, we find in the |b|>10{deg} region 31 sources in the first-year maps and 64 sources in the three-year co-added maps at a 5{sigma} level. The 1{sigma} position uncertainties are 1.6' and 1.4', respectively. The increased detections and improved positional accuracy are expected from the higher signal-to-noise ratio of the WMAP three-year data. All sources detected in the first-year maps are repeatedly detected in the three-year maps, which is a strong indication of the consistency of this method. Of all the sources, 97% are identified with either the WMAP three-year source catalog or plausible extrapolations of lower frequency data, which indicates that our method is also reliable. The two unidentified sources have been recently confirmed to be false detections, using the WMAP five-year data. We derive the source count distribution at the WMAP V band by combining our verified detections with sources from the WMAP three-year catalog. If we assume that the effect of source clustering is negligible, the contribution to the power spectrum from faint sources below 0.75Jy is estimated to be (2.4+/-0.8)x10^-3^uK^2^sr for the V band, which implies a source correction amplitude of A=0.012+/-0.004uK^2^sr.
- ID:
- ivo://CDS.VizieR/VII/54
- Title:
- Extragalactic Radio Source Identifications
- Short Name:
- VII/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is a compilation of all published optical identifications of extragalactic radio sources. This machine-readable version is an updated and greatly expanded edition of the original published one; this version contains 14585 identifications and citations to 917 papers. The data file contains most commonly used source name, number in the 4C catalog Gower et al. (1967), and Pilkington and Scott (1965) if applicable, right ascension and declination (equinox B1950.0), magnitude estimate for the identification type of optical object, identification reference, alternate name for identified object (if known), confirmation or invalidation code and associated reference, finding chart existence (or nonexistence), redshift, and reference for the spectrum. A reference file contains the references ordered by number cited in the catalog and alphabetically by author. Completeness has been attempted for all papers published through the end of 1982. The present version contains fewer references than the 1974 version (which had 935) because certain numbers were unused in the previous edition and because certain references are no longer used in the 1983 version and were removed. The authors have prepared this final version and have discontinued future updates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/1656
- Title:
- Extragalactic radio-sources at 95GHz
- Short Name:
- J/MNRAS/385/1656
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Australia Telescope Compact Array (ATCA) at 95GHz to carry out continuum observations of 130 extragalactic radio sources selected from the Australia Telescope 20GHz (AT20G) survey. We use a triple-correlation method to measure simultaneous 20- and 95-GHz flux densities for these objects, and over 90 per cent of our target sources are detected at 95GHz. We demonstrate that the ATCA can robustly measure 95-GHz flux densities with an accuracy of ~10 per cent in a few minutes for sources stronger than about 50mJy. We measure the distribution of radio spectral indices in a flux-limited sample of extragalactic sources, and show that the median 20-95GHz spectral index does not vary significantly with flux density for S_20_>150mJy . This finding allows us to estimate the extragalactic radio source counts at 95GHz by combining our observed 20-95GHz spectral-index distribution with the accurate 20-GHz source counts measured in the AT20G survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/898
- Title:
- Extragalactic radio sources selected at 20GHz
- Short Name:
- J/MNRAS/371/898
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present some first results on the variability, polarization and general properties of radio sources selected at 20GHz, the highest frequency at which a sensitive radio survey has been carried out over a large area of sky. Sources with flux densities above 100mJy in the Australia Telescope Compact Array 20GHz pilot survey at declination 60{deg} to 70{deg} were observed at up to three epochs during 2002-04, including near-simultaneous measurements at 5, 8 and 18GHz in 2003. Of the 173 sources detected, 65 per cent are candidate QSOs or BL Lac objects, 20 per cent galaxies and 15 per cent faint (bJ>22mag) optical objects or blank fields.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/3806
- Title:
- Extragalactic radio sources with recurrent jet
- Short Name:
- J/MNRAS/471/3806
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 74 radio sources with recurrent jet activity. The sample consists of 67 galaxies, 2 quasars and 5 unidentified sources, selected from the published data or are newly recognized. The sample's redshift range is 0.002<z<0.7 and the size of inner and outer structures varies from 0.02 to 4248kpc. We analyse the optical and radio properties of the sample and compare them with the characteristics of ordinary one-off FRII radio sources. With the help of stellar population modelling, we derive black hole masses and stellar masses of host galaxies of 35 restarting radio sources, finding that the black hole masses in restarting radio sources are comparable to those of typical single-cycle FRII radio sources. The obtained median values of log M_BH_ are 8.58 and 8.62M_{sun}_. Unlike the black hole masses, the stellar masses in restarting radio sources tend to be smaller than in the FRII sources. Although the stellar populations of the hosts of recurrent activity sources are dominated by old stars, a significant fraction of young stars can be observed as well. Based on the Sloan Digital Sky Survey photometric observations, we also analyse the morphology of the host galaxies and obtained significantly smaller concentration indices for the restarting radio sources when compared to the classical FRII hosts. This effect can be interpreted as a result of frequent merger events in the history of host galaxies of restarting radio sources.
- ID:
- ivo://CDS.VizieR/J/A+A/440/409
- Title:
- Extragalactic sources at 22 and 37GHz
- Short Name:
- J/A+A/440/409
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long term monitoring results from 2001 to mid 2004 of quasar observations at 22 and 37GHz done at the Metsahovi radio observatory are presented. Approximately 10000 observations are published here.
- ID:
- ivo://CDS.VizieR/J/A+A/427/769
- Title:
- Extragalactic sources at 22, 37 and 87GHz
- Short Name:
- J/A+A/427/769
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Long term monitoring results from mid 1995 to the end of 2000 of quasar observations at 22, 37 and 87GHz done at the Metsahovi radio observatory are presented. Approximately 15700 observations are published here.
