Tracing the Cosmological Evolution of Stars and Cold Gas with CMB Spectral Surveys

• Published in: The Astrophysical journal Vol. 838; no. 2; pp. 82 - 92
• Main Author: Switzer, Eric R.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 01-04-2017; American Astronomical Society; IOP Publishing
• Subjects: ANISOTROPY; Astronomy; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Bias; BRIGHTNESS; CALIBRATION; CARBON MONOXIDE; CHARGES; Cold gas; Contamination; Correlation; cosmic background radiation; COSMOLOGY; ELEMENT ABUNDANCE; EMISSION; FINE STRUCTURE; GALACTIC EVOLUTION; GALAXIES; galaxies: evolution; Instrument calibration; Ionization; LUMINOSITY; Mapping; Polls & surveys; RED SHIFT; RELICT RADIATION; STAR EVOLUTION; Star formation; STARS; Stellar evolution; Surface brightness
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa6576

A full account of galaxy evolution in the context of ΛCDM cosmology requires measurements of the average star-formation rate (SFR) and cold gas abundance across cosmic time. Emission from the CO ladder traces cold gas, and [C ii] fine structure emission at traces the SFR. Intensity mapping surveys the cumulative surface brightness of emitting lines as a function of redshift, rather than individual galaxies. CMB spectral distortion instruments are sensitive to both the mean and anisotropy of the intensity of redshifted CO and [C ii] emission. Large-scale anisotropy is proportional to the product of the mean surface brightness and the line luminosity-weighted bias. The bias provides a connection between galaxy evolution and its cosmological context, and is a unique asset of intensity mapping. Cross-correlation with galaxy redshift surveys allows unambiguous measurements of redshifted line brightness despite residual continuum contamination and interlopers. Measurement of line brightness through cross-correlation also evades cosmic variance and suggests new observation strategies. Galactic foreground emission is times larger than the expected signals, and this places stringent requirements on instrument calibration and stability. Under a range of assumptions, a linear combination of bands cleans continuum contamination sufficiently that residuals produce a modest penalty over the instrumental noise. For PIXIE, the sensitivity to CO and [C ii] emission scales from at low redshift to by reionization.