Redshift Estimation from Low‐Resolution Prism Spectral Energy Distributions with aNext Generation Space TelescopeMultiobject Spectrograph

We discuss the utility of a low‐resolution prism as a component of a multiobject spectrometer for NASA’s proposedNext Generation Space Telescope(NGST). Low‐resolution prism spectroscopy permits simultaneous observation of the 0.6–5 μm wavelength regime at \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $R\lesssim 50$ \end{document} . Such data can take advantage of modern techniques in spectral energy distribution (SED) fitting to determine source redshifts, sometimes called “photometric redshifts.” We compare simulated prism observations with filter imaging for this purpose withNGST. Low‐resolution prism observations of galaxy SEDs provide a significant advantage over multifilter observations for any realistic observing strategy. For an ideal prism in sky background–limited observing, the prism has a signal‐to‐noise ratio advantage of the square root of the resolution over serial observations by filters with similar spatial and spectral resolution in equal integration time. For a realistic case the advantage is slightly less, and we have performed extensive simulations to quantify it. We define strict criteria for the recovery of input redshifts, such that to be considered a success, redshift residuals must be \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\delta _{z}< 0.03+0.1\mathrm{log}\,z$ \end{document} . The simulations suggest that in \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryr