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Estimating Calibrator Counts at 250 GHz Using MAMBO... Abstract

by Dong-Chan Kim last modified Apr 25, 2011 by Pat Murphy

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ALMA Memo # 543

Estimating Calibrator Counts at 250 GHz Using MAMBO Observations of Flat Spectrum Quasars

M.A. Holdaway, Chris Carilli, Axel Weiss, Frank Bertoldi


We analyze the 250 GHz MAMBO fluxes of cm-selected bright, compact, flat spectrum quasars, match them with 8.4 GHz CLASS flux measurements, and derive a distribution for the spectral index between 8 GHz and 250 GHz. This spectral index distribution, when combined with Condon's 5 GHz flat spectrum source counts and the distribution of core fraction taken from the flat spectrum members of the 3CR2 sample, provides us with an estimate of the source counts of bright, compact, flat spectrum quasars which will be available to ALMA at 250 GHz for various calibrations. Over the entire sky at 250 GHz, we find there should be about 28,000 quasars brighter than 10 mJy, 2230 quasars brighter than 100 mJy, and 70 quasars brighter than 1 Jy. The source count estimates in the current memo exceed the estimates of Holdaway and Owen (2005) at 250 GHz by 14% at 10 mJy, 33% at 100 mJy, and 55% at 1 Jy. The higher estimated counts as derived in this current work are a direct result of sources observed to have a very flat or even inverted spectral index between 8 and 250 GHz which were largely missing in Holdaway and Owen's spectral index distribution.

View a pdf version of ALMA Memo #543.