Signatures of first galaxies at FIR/sub-mm wavelengths

Abstract

We explore the possibility of detecting first galaxies with a generic far-infrared/sub-millimeter telescope by applying an analytical model of primordial dust emission. As shown in previous works, galaxies at redshifts $z>7$ experience a strong negative K-correction in such a way that systems of similar masses are brighter at higher $z$. In addition, at a given mass and $z$, our model predicts that luminosity fluxes increase proportionally to the dust-to-metal ratios ($D/M$) of primeval sources. We evaluate the observability of model sources at different $z>7$ as a function of the observed survey area ($\Delta \Omega$) and sensitivity ($S$) of a generic instrument. Assuming $\Delta \Omega \sim 10{\mathrm{deg}}^2$ and a plausible $S\sim 1\mu \mathrm{Jy}$ for a near future survey, we could assure the detection of at least one typical source with $D/M\sim 5\times 10^{-3}$ at $z>7$. For $S\gtrsim 1\mu \mathrm{Jy}$ and $\Delta \Omega \lesssim 10{\mathrm{deg}}^2$, higher than typical $D/M$ are required to detect at least one individual source at $z>7$. The observability of model galaxies is also affected by the size distribution of dust grains, specially towards higher $z$.

arXiv comment3 pages, 2 figures. Accepted for publication in BAAA, Vol. 61B, 2020