The European Large Area ISO Survey (ELAIS): Optical Identifications of 15 micron and 1.4 GHz sources in N1 and N2

Abstract

We present the optical identification of mid-IR and radio sources detected in the European Large Area ISO Survey (ELAIS) areas N1 and N2. Using the r' band optical data from the Wide Field Survey we apply a likelihood ratio method to search for the counterparts of the 1056 and 691 sources detected at 15 micron and 1.4 GHz respectively, down to flux limits of S_{15}=0.5 mJy and S_{1.4 GHz}=0.135 mJy. We find that ~92% of the 15 micron ELAIS sources have an optical counterpart down to the magnitude limit of the optical data, r'=24. All mid-IR sources with fluxes S_{15} >= 3 mJy have an optical counterpart. The magnitude distribution of the sources shows a well defined peak at relatively bright magnitudes r'~18. About 20% of the identified sources show a point-like morphology; its magnitude distribution has a peak at fainter magnitudes than those of galaxies. The mid-IR-to-optical and radio-to-optical flux diagrams are presented and discussed in terms of actual galaxy models. Objects with mid-IR-to-optical fluxes larger than 1000 are found that can only be explained as highly obscured star forming galaxies or AGNs. Blank fields being 8% of the 15 micron sample have even larger ratios suggesting that they may be associated with higher redshift and higher obscured objects.

arXiv comment10 pages, 13 figures, submitted to MNRAS. Catalogues, postage stamps and full quality figures in: http://www.ast.cam.ac.uk/~eglez/eid/

References in corpus (18)

• The Sloan Digital Sky Survey: Technical Summary
• The Dust Content and Opacity of Actively Star-Forming Galaxies
• The First Data Release of the Sloan Digital Sky Survey
• Extragalactic Results from the Infrared Space Observatory
• The European Large Area ISO Survey I: Goals, Definition and Observation
• Representations of world coordinates in FITS
• The European Large Area ISO Survey (ELAIS): The Final Band-merged Catalogue
• The AGN contribution to mid-infrared surveys
• A Deep VLA survey at 20cm of the ISO ELAIS survey regions
• New Method for ISOCAM Data Reduction - II. Mid-Infrared Extragalactic Source Counts in the Southern ELAIS Field
• The INT Wide Field Imaging Survey(WFS)
• The nature of the mid-infrared population from optical identifications of the ELAIS-S1 sample
• A New Method for ISOCAM Data Reduction - I. Application to the European Large Area ISO Survey Southern Field: Method and Results
• Observations of the Hubble Deep Field South with the Infrared Space Observatory - I. Observations, data reduction and mid-infrared source counts
• Observations of the Hubble Deep Field with the Infrared Space Observatory. IV. Association of sources with Hubble Deep Field Galaxies
• Obscured AGN from the ELAIS Deep X-ray Survey
• On the nature of the ISO-selected sources in the ELAIS S2 region
• Models for the IR and submm SEDs of normal, starburst and active galaxies

Cited by in corpus (9)

• Obscuration in extremely luminous quasars
• Mid-infrared spectroscopy of infrared-luminous galaxies at z~0.5-3
• High-Redshift QSOs in the SWIRE Survey and the z~3 QSO Luminosity Function
• Galaxy and Mass Assembly (GAMA): The evolution of bias in the radio source population to z ~ 1.5
• Properties of FIRBACK-ELAIS 175 um sources in the ELAIS N2 region
• Clustering of galaxies at 3.6 microns in the Spitzer Wide-area Infrared Extragalactic legacy survey
• Parametric modelling of the 3.6um to 8um colour distributions of galaxies in the SWIRE Survey
• Identifications of FIRST radio sources in the NOAO Deep-Wide Field Survey
• Simulations and Observations of the Microwave Universe