The Radio-to-Submillimeter Flux Density Ratio of Galaxies as a Measure of Redshift

Abstract

We re-examine the technique of determining the redshifts of galaxies from the ratio of the submillimeter-to-radio continuum flux densities based on a recently published catalog of 850~$\mu$m sources. We derived the expected variation of this ratio as a function of redshift incorporating the expected average luminosity and the spectral energy distribution (SED) of dust emission and the radio continuum. We find that the existing data for most of the high redshift ($z \gtsim 1$) sources correspond to our new calculation. Amongst the well-identified sources, there is none with an index significantly higher than predicted. Sources which have an index lower than predicted are either within the error zone or much lower, the latter presumably having AGN-dominated radio-continuum emission. We find the median redshift to be $\sim 2$, which is consistent with that deduced by previous work ($\sim 3$) within the error. We also discuss the various systematic effects that can affect the accuracy of the redshift estimate. We examine other methods of redshift estimation, like photometric ratio in the submillimeter and locating the peak of the SED in the rest system of the objects. We conclude that while the various methods are helpful in identifying high-redshift objects and making a crude estimate of the redshift, they are not, at present, accurate enough for a detailed study of redshift distribution of the submillimeter galaxies.

6 pages LaTeX, PASJ in press

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Cited by in corpus (13)

• Deep radio imaging of the SCUBA 8-mJy survey fields: sub-mm source identifications and redshift distribution
• The SCUBA HAlf Degree Extragalactic Survey (SHADES) - III. Identification of radio and mid-infrared counterparts to submillimetre galaxies
• The Chandra Deep Field-North Survey. XIV. X-ray detected Obscured AGNs and Starburst Galaxies in the Bright Submm Source Population
• AzTEC millimeter survey of the COSMOS field - III. Source catalog over 0.72 sq. deg. and plausible boosting by large-scale structure
• The FIR/Radio correlation of high redshift galaxies in the HDF-N
• The SCUBA HAlf Degree Extragalactic Survey (SHADES) - IV: Radio-mm-FIR photometric redshifts
• The SCUBA HAlf Degree Extragalactic Survey (SHADES) -- I. Survey motivation, design and data processing
• A Vigorous Starburst in the SCUBA Galaxy N2 850.4
• SCUBA Observations of MAMBO Sources
• Improving the identification of high-z Herschel sources with position priors and optical/NIR and FIR/mm photometric redshifts
• Confirmation of the effectiveness of sub-mm source redshift estimation based on rest-frame radio to FIR photometry
• The Canada-UK Deep Submillimetre Survey VIII: Source Identifications in the 3-hour field
• A broadband spectroscopic search for CO line emission in HDF850.1: the brightest submillimetre object in the Hubble Deep Field North