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Register a new userThe 1.28 GHz MeerKAT DEEP2 Image
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T. Mauch
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We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $approx 68$ FWHM primary beam area with $7.6$ FWHM resolution and $0.55 pm 0.01$ $mu$Jy/beam rms noise. Its J2000 center position $alpha=04^h 13^m 26.4^s$, $delta=-80^circ 00 00$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $mu$Jy with counts of individual DEEP2 sources between $10$ $mu$Jy and $2.5$ mJy. Most sources fainter than $S sim 100$ $mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $mu$Jy account for $sim93%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 lesssim log[S(mathrm{Jy})] lesssim -4$.
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The IRAS Revised Bright Galaxy Sample (RBGS) comprises galaxies and unresolved mergers stronger than $S = 5.24$ Jy at $lambda = 60~mumathrm{m}$ with galactic latitudes $vert b vert > 5^circ$. Nearly all are dusty star-forming galaxies whose radio continuum and far-infrared luminosities are proportional to their current rates of star formation. We used the MeerKAT array of 64 dishes to make $5 times 3$ min snapshot observations at $ u = 1.28$ GHz covering all 298 southern (J2000 $delta < 0^circ$) RBGS sources identified with external galaxies. The resulting images have $theta approx 7.5$ arcsec FHWM resolution and rms fluctuations $sigma approx 20~mumathrm{Jy~beam}^{-1} approx 0.26$ K, low enough to reveal even faint disk emission. The rms position uncertainties are $sigma_alpha approx sigma_delta approx 1$ arcsec relative to accurate near-infrared positions, and the image dynamic ranges are DR $gtrsim 10^4:1$.
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