The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic

Prandoni, I.; Guglielmino, G.; Morganti, Raffaella; Vaccari, M.; Maini, Alessandro; Röttgering, H. J. A.; Jarvis, Matthew; Garrett, M. A.

doi:10.1093/mnras/sty2521

Cited by 70 publications

(123 citation statements)

References 114 publications

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“…More recent deep radio continuum surveys at 1.4 GHz find results consistent with the above relation (e.g. Bondi et al 2003;Prandoni et al 2018). Thus the incident flux density on the Hi source from a background source with flux density S is f c S , where…”

Section: Covering Fraction For Background Sourcessupporting

confidence: 75%

A first quantification of the effects of absorption for H I intensity mapping experiments

Roychowdhury

Dickinson

Browne

2019

A&A

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Context. Hi Intensity Mapping (IM) will be used to do precision cosmology, using many existing and upcoming radio observatories. It will measure the integrated Hi 21 cm emission signal from 'voxels' of the sky at different redshifts. The signal will be contaminated due to absorption, the largest component of which will be the flux absorbed by the Hi emitting sources themselves from the potentially bright flux incident on them from background radio continuum sources. Aims. We, for the first time, provide a quantitative estimate of the magnitude of the absorbed flux compared to the emitted Hi flux. The ratio of the two fluxes was calculated for various voxels placed at redshifts between 0.1 and 2.5. Methods. We used a cosmological sky simulation of the atomic Hi emission line, and summed over the emitted and absorbed fluxes for all sources within voxels at different redshift. In order to determine the absorbed flux, for each Hi source the flux incident from background radio continuum sources was estimated by determining the numbers, sizes, and redshift distribution of radio continuum sources that lie behind it, based on existing observations and simulations. The amount of this incident flux that is absorbed by each Hi source was calculated using a relation between integrated optical depth with Hi column density determined using observations of damped Lyman-α systems (DLAs) and sub-DLAs. Results. We find that for the same co-moving volume of sky, the Hi emission decreases quickly with increasing redshift, while the absorption varies much less with redshift and follows the redshift distribution of faint sources that dominate the number counts of radio continuum sources. This results in the fraction of absorption compared to emission to be negligible in the nearby Universe (up to a redshift of ∼0.5), increases to about 10% at a redshift of one, and continues to increase to about 30% up to a redshift of 2.5. These numbers can vary significantly due to the uncertainty on the exact form of the following relations: firstly, the number counts of radio continuum sources at sub-mJy flux densities; secondly, the relation between integrated optical depth and Hi column density of Hi sources; and thirdly, the redshift distribution of radio continuum sources up to the highest redshifts. Conclusions. Absorption of the flux incident from background radio continuum sources might become an important contaminant to Hi IM signals beyond redshifts of 0.5. The impact of absorption needs to be quantified more accurately using inputs from upcoming deep surveys of radio continuum sources, Hi absorption, and Hi emission with the Square Kilometre Array and its precursors.

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Section: Covering Fraction For Background Sourcessupporting

confidence: 75%

A first quantification of the effects of absorption for H I intensity mapping experiments

Roychowdhury

Dickinson

Browne

2019

A&A

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“…Along with simulated radio catalogues we have also compared differential source counts with observed source populations at lowfrequency as well as high-frequency in the right panel of Fig. 1 (Prandoni et al 2018), the 1.4 GHz source counts based on observation with VLA by Condon (1984), the Phoenix Deep Survey at 1.4 GHz with ATCA (Hopkins et al 2003), COSMOS field at 3 GHz with VLA (Smolčić et al 2017). In all cases we have scaled the source counts to 1.4 GHz using a spectral index, α = −0.8.…”

Section: Differential Source Countsmentioning

confidence: 99%

Characterization of unresolved and unclassified sources detected in radio continuum surveys of the Galactic plane

Chakraborty

Roy

Wang

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The continuum emission from 1 to 2 GHz of The H i/OH/Recombination line survey of the inner Milky Way (THOR) at ≲18 arcsec resolution covers ∼132 deg2 of the Galactic plane and detects 10 387 sources. Similarly, the first data release of the Global View of Star Formation in the Milky Way (GLOSTAR) survey covers ∼16 deg2 of the Galactic plane from 4 to 8 GHz at 18 arcsec resolution and detects 1575 sources. However, a large fraction of the unresolved discrete sources detected in these radio continuum surveys of the Galactic plane remain unclassified. Here, we study the Euclidean-normalized differential source counts of unclassified and unresolved sources detected in these surveys and compare them with simulated extragalactic radio source populations and previously established source counts. We find that the differential source counts for THOR and GLOSTAR surveys are in excellent agreement with both simulation and previous observations. We also estimate the angular two-point correlation function of unclassified and unresolved sources detected in THOR survey. We find a higher clustering amplitude in comparison with the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey up to the angular separation of 5°. The decrease in angular correlation with increasing flux cut and the excellent agreement of clustering pattern of sources above 1 mJy with high-z samples (z > 0.5) of the FIRST survey indicates that these sources might be high-z extragalactic compact objects. The similar pattern of one-point and two-point statistics of unclassified and compact sources with extragalactic surveys and simulations confirms the extragalactic origin of these sources.

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“…Unfortunately, considerable scatter is seen in the differential source counts at the lowest flux levels. For example, the 1.4 GHz normalized differential source counts vary by a factor of ≈ 6 at a level of 100 µJy (De Zotti et al 2010;Prandoni et al 2018), underscoring the need for good deep surveys.…”

Section: Background Sourcesmentioning

confidence: 99%

CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

Irwin

Wiegert

Merritt

et al. 2019

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The CHANG-ES galaxy sample consists of 35 nearby edge-on galaxies that have been observed using the VLA at 1.6 GHz and 6.0 GHz. Here we present the 3rd data release of our sample, namely the B-configuration 1.6 GHz sample. In addition, we make available the band-to-band spectral index maps between 1.6 GHz and 6.0 GHz, the latter taken in the matching resolution C-configuration. The images can be downloaded from https://www.queensu.ca/changes. These are our highest resolution images (≈ 3 arcsec) and we examine the possible presence of low luminosity active galactic nuclei in the sample as well as some in-disk structure. New features can be seen in the spectral index maps that are masked in the total intensity emission, including hidden spiral arms in NGC 3448 and two previously unknown radio lobes on either side of the nucleus of NGC 3628. Our AGN detection rate, using only radio criteria, is 55% which we take as a lower limit because some weaker embedded AGNs are likely present which could be revealed at higher resolution. Archival XMM-Newton data were used to search for further fingerprints of the AGNs in the studied sample. In galaxy disks, discrete regions of flat spectral index are seen, likely due to a thermal emission fraction that is higher than the global average.

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The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic

Cited by 70 publications

References 114 publications

A first quantification of the effects of absorption for H I intensity mapping experiments

A first quantification of the effects of absorption for H I intensity mapping experiments

Characterization of unresolved and unclassified sources detected in radio continuum surveys of the Galactic plane

CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

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The Lockman Hole Project: new constraints on the sub-mJy source counts from a wide-area 1.4 GHz mosaic

Cited by 70 publications

References 114 publications

A first quantification of the effects of absorption for H I intensity mapping experiments

A first quantification of the effects of absorption for H I intensity mapping experiments

Characterization of unresolved and unclassified sources detected in radio continuum surveys of the Galactic plane

CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

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A first quantification of the effects of absorption for H I intensity mapping experiments

A first quantification of the effects of absorption for H I intensity mapping experiments