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

Abstract

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.

The CO Luminosity Density at High-z (COLDz) Survey: A Sensitive, Large-area Blind Search for Low-J CO Emission from Cold Gas in the Early Universe with the Karl G. Jansky Very Large Array

“…Of the 18 sources from the Smolčić et al (2017) catalog located within the boundaries of our mosaic, our secure sources represent the only ones with a redshift estimate (photometric or spectroscopic, when available) falling within our survey volume. All remaining sources from the Smolčić et al (2017) catalog within our survey area lie in the range z=0.1-1.6.…”

“…Of the 18 sources from the Smolčić et al (2017) catalog located within the boundaries of our mosaic, our secure sources represent the only ones with a redshift estimate (photometric or spectroscopic, when available) falling within our survey volume. All remaining sources from the Smolčić et al (2017) catalog within our survey area lie in the range z=0.1-1.6. We performed an equivalent search in the catalog from the eMERGE 5.5 GHz survey of the GOODS-N field (Guidetti et al 2017), finding a single association for GN19 by using a 3″ search radius.…”

“…The deep radio catalogs by Smolčić et al (2017) in COSMOS and by Morrison et al (2010) in GOODS-N have a 5σ sensitivity limit of ∼11 μJy at 3 GHz and 20 μJy at 1.4 GHz, respectively, which can be converted to upper limits on the L FIR for radio counterparts to our line candidates through the radio-IR correlation. By adopting the relationship from…”

Radio Selection of the Most Distant Galaxy Clusters

“…in a z=2.5 Cluster Deep VLA observations of the COSMOS field at 3 GHz have been obtained, fully reduced, analyzed, and publicly released by Smolčić et al (2017). We have used the pointspread function (PSF) fitting technique and cataloging method of Liu et al (2017) to obtain radio flux density measurements at 3 GHz for all Ks-selected galaxies in the COSMOS2015 catalog of Laigle et al (2016), supplemented with sources from Muzzin et al (2013).…”

“…We concentrate here on the radio properties of galaxies in the surroundings of the W16 cluster, as compared to those in the full COSMOS 2 deg 2 field. Thanks to our PSF fitting technique we can push to deeper radio flux levels compared to blindly extracted signal-to-noise ratio (S/N) > 5 catalogs in Smolčić et al (2017), with high fidelity and completeness and with a very low expected spurious detection rate. Our simulations return typical rms sensitivities of 2.5-2.7 μJy with well-behaved Gaussian-like uncertainties, close to the expected 2.3 μJy noise, allowing for reliable S/N > 3 detections at 3 GHz down to about 8 μJy.…”