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

## TL;DR

This paper presents the deepest and largest 3 GHz radio continuum survey of the COSMOS field, providing a detailed catalog of over 10,800 sources with high positional accuracy and spectral information, advancing radio astronomical studies.

## Contribution

The study delivers the first large-scale, high-resolution 3 GHz radio source catalog for the COSMOS field, combining extensive observations with advanced imaging and analysis techniques.

## Key findings

- Catalog of 10,830 sources down to 5 sigma detection threshold
- Median spectral index of -0.7 derived from combined data
- Astrometry accurate to 0.01 arcseconds for bright sources

## Abstract

We present the VLA-COSMOS 3 GHz Large Project based on 384 hours 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 uJy/beam 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 5 sigma, 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_3GHz > 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 alpha=-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.