Tracing the Cosmological Evolution of Stars and Cold Gas with CMB Spectral Surveys
Abstract
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 158 μ {{m}} 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 ≈ {10}3 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 2σ sensitivity to CO and [C II] emission scales from ≈ 5× {10}-2 {kJy} {sr}}-1 at low redshift to ≈ 2 {kJy} {sr}}-1 by reionization.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2017
- DOI:
- 10.3847/1538-4357/aa6576
- arXiv:
- arXiv:1703.07832
- Bibcode:
- 2017ApJ...838...82S
- Keywords:
-
- cosmic background radiation;
- galaxies: evolution;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 11 pages, 9 figures, accepted in ApJ