Mosaiced wide-field VLBI observations of the Lockman Hole/XMM

Abstract

Active Galactic Nuclei (AGN) play a decisive role in galaxy evolution, particularly so when operating in a radiatively inefficient mode, where they launch powerful jets that reshape their surroundings. However, identifying them is difficult, since radio observations commonly have resolutions of between 1 arcsec and 10 arcsec, which is equally sensitive to radio emission from star-forming activity and from AGN. Very Long Baseline Interferometry (VLBI) observations allow one to filter out all but the most compact non-thermal emission from radio survey data. The observational and computational demands to do this in large surveys have been, until recently, too high to make such undertakings feasible. Only the recent advent of wide-field observing techniques have facilitated such observations, and we here present the results from a survey of 217 radio sources in the Lockman Hole/XMM field. We describe in detail some new aspects of the calibration, including primary beam correction, multi-source self-calibration, and mosaicing. As a result, we detected 65 out of the 217 radio sources and were able to construct, for the first time, the source counts of VLBI-detected AGN. They indicate that at least 15%-25% of the sub-mJy radio sources are AGN-driven, consistent with recent findings using other AGN selection techniques. We have used ancillary data to investigate the AGN hosts. We find that among the sources nearby enough to be resolved in the optical images, 88% (23/26) could be classified as early-type or bulge-dominated galaxies. While 50% of these sources are correctly represented by the SED of an early-type galaxy, for the rest the best fit was obtained with a heavily extinct starburst template, an effect we ascribe to a degeneracy in the fit. Overall, the typical hosts of VLBI-detected sources are in good agreement with being early-type or bulge-dominated galaxies.

41 pages, accepted for publication in A&A

References in corpus (19)

• COSMOS Photometric Redshifts with 30-bands for 2-deg2
• Hot and cold gas accretion and feedback in radio-loud active galaxies
• Photometric redshift and classification for the XMM-COSMOS sources
• DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments
• The VLA-COSMOS Survey: II. Source Catalog of the Large Project
• The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
• The suppression of star formation by powerful active galactic nuclei
• Radio imaging of the Subaru/XMM-Newton Deep Field - I. The 100-microJy catalogue, optical identifications, and the nature of the faint radio source population
• Deep ATLAS radio observations of the CDFS-SWIRE field
• The Spitzer Extragalactic Representative Volume Survey (SERVS): survey definition and goals
• Deep near-infrared spectroscopy of passively evolving galaxies at z>1.4
• A new method to separate star forming from AGN galaxies at intermediate redshift: The submillijansky radio population in the VLA-COSMOS survey
• The Deep SWIRE Field I. 20cm Continuum Radio Observations: A Crowded Sky
• BLOBCAT: Software to Catalogue Flood-Filled Blobs in Radio Images of Total Intensity and Linear Polarization
• GOODS-Herschel: Ultra-deep XMM-Newton observations reveal AGN/star-formation connection
• XMM-Newton observations of the Lockman Hole: X-ray source catalogue and number counts
• A deep, high resolution survey of the low frequency radio sky
• VLBI imaging throughout the primary beam using accurate UV shifting
• Beam squint and Stokes V with off-axis feeds

Cited by in corpus (32)

• The Quest for Dual and Binary Supermassive Black Holes: A Multi-Messenger View
• Microarcsecond VLBI pulsar astrometry with PSR$\pi$ II. parallax distances for 57 pulsars
• mJIVE-20: a survey for compact mJy radio objects with the Very Long Baseline Array
• The wide-field VLBA calibrator survey -- WFCS
• The faint radio sky: VLBA observations of the COSMOS field
• Deep sub-arcsecond widefield imaging of the Lockman Hole field at 144 MHz
• Identifying active galactic nuclei via brightness temperature with sub-arcsecond International LOFAR Telescope observations
• Fundamental Reference AGN Monitoring Experiment (FRAMEx) I: Jumping Out of the Plane with the VLBA
• Nowhere to Hide: Radio-faint AGN in the GOODS-N field. I. Initial catalogue and radio properties
• VLBI observations of the radio quasar J2228+0110 at z=5.95 and other field sources in multiple-phase-centre mode
• Evidence from the Very Long Baseline Array that J1502SE/SW are Double Hotspots, not a Supermassive Binary Black Hole
• An ALMA Survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS Field: The Far-infrared/Radio correlation for High-redshift Dusty Star-forming Galaxies
• The faint source population at 15.7 GHz - III. A high-frequency study of HERGs and LERGs
• Multi-source self-calibration: Unveiling the microJy population of compact radio sources
• Astrometry of OH/IR stars using 1612 MHz hydroxyl masers. I. Annual parallaxes of WX Psc and OH138.0+7.2
• Nowhere to Hide: Radio-faint AGN in the GOODS-N field. II. Multi-wavelength AGN selection techniques and host galaxy properties
• A VLBA Survey of radio stars in the Orion Nebula Cluster: I. The nonthermal radio population
• Widefield VLBI observations of M31: A Unique Probe of the Ionized ISM of a nearby galaxy
• MeqSilhouette v2: Spectrally-resolved polarimetric synthetic data generation for the Event Horizon Telescope
• Four hot DOGs in the microwave
• VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz
• Constraints on Two Active Galactic Nuclei in the Merger Remnant COSMOS J100043.15+020637.2
• SPARCS-North Wide-field VLBI Survey: Exploring the resolved MicroJy extra-galactic radio source population with EVN+e-MERLIN
• Active galactic nuclei cores in infrared-faint radio sources: Very long baseline interferometry observations using the Very Long Baseline Array
• SYMBA: An end-to-end VLBI synthetic data generation pipeline
• Radio emission from dust-obscured galaxies
• A Large Scale Structure at Redshift 1.71 in the Lockman Hole
• Searching for obscured AGN in z $\sim$ 2 submillimetre galaxies
• Are the hosts of VLBI selected radio-AGN different to those of radio-loud AGN?
• Dynamical masses of YSOs with the VLBA: DYNAMO VLBA: Trigonometric parallaxes and proper motions of YSOs in Orion
• Milli-arcsecond properties of 10C sources in the Lockman Hole
• Four hot DOGs eaten up with the EVN