Extragalactic radio sources with sharply inverted spectrum at metre wavelengths

Krishna, Gopal; Sirothia, S. K.; Mhaskey, Mukul; Ranadive, Pritesh; Wiita, Paul J.; Goyal, A.; Kantharia, N. G.; Ishwara‐Chandra, C. H.

doi:10.1093/mnras/stu1364

Cited by 14 publications

(11 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This method however cannot constrain all lower limits and the cumulative function does not converge to 0, yielding a total of 6% unconstrained sources. To constrain these (as needed to derive the probability density function, PDF, for spectral indices; see below) we employed a physical argument that a radio source exhibiting standard synchrotron self-absorption cannot have a spectral index higher than α max = 2.5 (Rees 1967; unless it is extremely rare and exotic; for example see Krishna et al 2014). Our data can also constrain the distribution of spectral indices only up to value of α = 0.8, since this interval contains 99.5% of sources detected at both 1.4 and 3 GHz.…”

Section: 4-3 Ghz Spectral Indicesmentioning

confidence: 99%

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

Smolčić

Novak

Bondì

et al. 2017

A&A

300

365

View full text Add to dashboard Cite

We present the VLA-COSMOS 3 GHz Large Project based on 384 h of observations with the Karl G. Jansky Very Large Array (VLA) at 3 GHz (10 cm) toward the two square degree Cosmic Evolution Survey (COSMOS) field. The final mosaic reaches a median rms of 2.3 µJy beam −1 over the two square degrees at an angular resolution of 0.75 . To fully account for the spectral shape and resolution variations across the broad (2 GHz) band, we image all data with a multiscale, multifrequency synthesis algorithm. We present a catalog of 10 830 radio sources down to 5σ, out of which 67 are combined from multiple components. Comparing the positions of our 3 GHz sources with those from the Very Long Baseline Array (VLBA)-COSMOS survey, we estimate that the astrometry is accurate to 0.01 at the bright end (signal-to-noise ratio, S /N 3 GHz > 20). Survival analysis on our data combined with the VLA-COSMOS 1.4 GHz Joint Project catalog yields an expected median radio spectral index of α = −0.7. We compute completeness corrections via Monte Carlo simulations to derive the corrected 3 GHz source counts. Our counts are in agreement with previously derived 3 GHz counts based on single-pointing (0.087 square degrees) VLA data. In summary, the VLA-COSMOS 3 GHz Large Project simultaneously provides the largest and deepest radio continuum survey at high (0.75 ) angular resolution to date, bridging the gap between last-generation and next-generation surveys.

show abstract

Section: 4-3 Ghz Spectral Indicesmentioning

confidence: 99%

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

Smolčić

Novak

Bondì

et al. 2017

A&A

300

365

View full text Add to dashboard Cite

show abstract

“…As of this writing, there have been five data releases, with only about ten percent of the survey images having been processed and released through the TGSS project website 1 . A small number of publications have been published using data from this initial release including Bagchi et al (2011), Gopal-Krishna et al (2012), Sirothia et al (2014), and Krishna et al (2014).…”

Section: Introductionmentioning

confidence: 99%

The GMRT 150 MHz all-sky radio survey

Intema

Jagannathan

Mooley

et al. 2017

A&A

831

767

View full text Add to dashboard Cite

We present the first full release of a survey of the 150 MHz radio sky, observed with the Giant Metrewave Radio Telescope (GMRT) between April 2010 and March 2012 as part of the TIFR GMRT Sky Survey (TGSS) project. Aimed at producing a reliable compact source survey, our automated data reduction pipeline efficiently processed more than 2000 h of observations with minimal human interaction. Through application of innovative techniques such as image-based flagging, direction-dependent calibration of ionospheric phase errors, correcting for systematic offsets in antenna pointing, and improving the primary beam model, we created good quality images for over 95 percent of the 5336 pointings. Our data release covers 36 900 deg 2 (or 3.6 π steradians) of the sky between −53• and +90• declination (Dec), which is 90 percent of the total sky. The majority of pointing images have a noise level below 5 mJy beamwith an approximate resolution of 25 × 25 (or 25 × 25 /cos (Dec − 19 • ) for pointings south of 19 • declination). We have produced a catalog of 0.62 Million radio sources derived from an initial, high reliability source extraction at the seven sigma level. For the bulk of the survey, the measured overall astrometric accuracy is better than two arcseconds in right ascension and declination, while the flux density accuracy is estimated at approximately ten percent. Within the scope of the TGSS alternative data release (TGSS ADR) project, the source catalog, as well as 5336 mosaic images (5• × 5 • ) and an image cutout service, are made publicly available at the CDS as a service to the astronomical community. Next to enabling a wide range of different scientific investigations, we anticipate that these survey products will provide a solid reference for various new low-frequency radio aperture array telescopes (LOFAR, LWA, MWA, SKA-low), and can play an important role in characterizing the epoch-of-reionisation (EoR) foreground. The TGSS ADR project aims at continuously improving the quality of the survey data products. Near-future improvements include replacement of bright source snapshot images with archival targeted observations, using new observations to fill the holes in sky coverage and replace very poor quality observational data, and an improved flux calibration strategy for less severely affected observational data.

show abstract

“…Simple alignment of pulsed emission peaks in a wide range of frequency would cause an overestimated DM. In fact, any Galactic pulsars (Kijak et al 2011;Basu et al 2018) or extragalactic radio sources with such an inverted spectrum at lower frequencies (Guerra et al 2002;Gopal-Krishna et al 2014;Mhaskey et al 2019a,b) can be so explained by the scattering effect caused by very cloudy ionized gas in front of or in the environment of a strong emission source. The flux densities and polarization properties may vary if the source and the intervening clouds are moving relatively in any transverse direction.…”

Section: Improved Parameters For Known Pulsarsmentioning

confidence: 99%

The FAST Galactic Plane Pulsar Snapshot survey: I. Project design and pulsar discoveries^⋆

Han

Wang

et al. 2021

Res. Astron. Astrophys.

127

104

View full text Add to dashboard Cite

Discovery of pulsars is one of the main goals for large radio telescopes. The Five-hundred-meter Aperture Spherical radio Telescope (FAST), that incorporates an L-band 19-beam receiver with a system temperature of about 20 K, is the most sensitive radio telescope utilized for discovering pulsars. We designed the snapshot observation mode for a FAST key science project, the Galactic Plane Pulsar Snapshot (GPPS) survey, in which every four nearby pointings can observe a cover of a sky patch of 0.1575 square degrees through beam-switching of the L-band 19-beam receiver. The integration time for each pointing is 300 seconds so that the GPPS observations for a cover can be made in 21 minutes. The goal of the GPPS survey is to discover pulsars within the Galactic latitude of ± 10° from the Galactic plane, and the highest priority is given to the inner Galaxy within ± 5°. Up to now, the GPPS survey has discovered 201 pulsars, including currently the faintest pulsars which cannot be detected by other telescopes, pulsars with extremely high dispersion measures (DMs) which challenge the currently widely used models for the Galactic electron density distribution, pulsars coincident with supernova remnants, 40 millisecond pulsars, 16 binary pulsars, some nulling and mode-changing pulsars and rotating radio transients (RRATs). The follow-up observations for confirmation of new pulsars have polarization-signals recorded for polarization profiles of the pulsars. Re-detection of previously known pulsars in the survey data also leads to significant improvements in parameters for 64 pulsars. The GPPS survey discoveries are published and will be updated at http://zmtt.bao.ac.cn/GPPS/.

show abstract

Extragalactic radio sources with sharply inverted spectrum at metre wavelengths

Cited by 14 publications

References 36 publications

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

The GMRT 150 MHz all-sky radio survey

The FAST Galactic Plane Pulsar Snapshot survey: I. Project design and pulsar discoveries^⋆

Contact Info

Product

Resources

About

Extragalactic radio sources with sharply inverted spectrum at metre wavelengths

Cited by 14 publications

References 36 publications

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release

The GMRT 150 MHz all-sky radio survey

The FAST Galactic Plane Pulsar Snapshot survey: I. Project design and pulsar discoveries ⋆

Contact Info

Product

Resources

About

The FAST Galactic Plane Pulsar Snapshot survey: I. Project design and pulsar discoveries^⋆