Search for C ii emission on cosmological scales at redshift Z ∼ 2.6

Abstract

We present a search for C ii emission over cosmological scales at high-redshifts. The C ii line is a prime candidate to be a tracer of star formation over large-scale structure since it is one of the brightest emission lines from galaxies. Redshifted C ii emission appears in the submillimeter regime, meaning it could potentially be present in the higher frequency intensity data from the Planck satellite used to measure the cosmic infrared background (CIB). We search for C ii emission over redshifts z = 2 − 3.2 in the Planck 545 GHz intensity map by cross-correlating the 3 highest frequency Planck maps with spectroscopic quasars and CMASS galaxies from the Sloan Digital Sky Survey III (SDSS-III), which we then use to jointly fit for C ii intensity, CIB parameters, and thermal Sunyaev-Zeldovich (SZ) emission. We report a measurement of an anomalous emission I ν = 6.6 +5.0 −4.8 × 10 4 Jy/sr at 95% confidence, which could be explained by C ii emission, favoring collisional excitation models of C ii emission that tend to be more optimistic than models based on C ii luminosity scaling relations from local measurements; however, a comparison of Bayesian information criteria reveal that this model and the CIB & SZ only model are equally plausible. Thus, more sensitive measurements will be needed to confirm the existence of large-scale C ii emission at high redshifts. Finally, we forecast that intensity maps from Planck cross-correlated with quasars from the Dark Energy Spectroscopic Instrument (DESI) would increase our sensitivity to C ii emission by a factor of 5, while the proposed Primordial Inflation Explorer (PIXIE) could increase the sensitivity further.

Constraining the evolution of [C ii] intensity through the end stages of reionization

“…Table 2. As indicated in Pullen et al (2018), a confirmation of this initial [CII] intensity mapping measurement would provide exciting insights for galaxy evolution and the metallicity of the ISM. From the results of the present work, we find that it can also be used to investigate how the [CII] -SFRD relation evolves with redshift during and after the peak of star formation in the universe.…”

“…We use the technique of abundance matching to derive constraints on the local [CII] luminosity -halo mass relation from the observations of the z ∼ 0 [CII] luminosity function (Hemmati et al 2017). We combine this information with the recent high-redshift constraints on the [CII] intensity (Pullen et al 2018, assuming the CII detection) at z ∼ 2.6 to model the evolution of this relation at higher redshifts, and find the predictions to be to consistent with the currently available observational limits from galaxy data at z ∼ 4 − 6 ( Matsuda et al 2015;Swinbank et al 2012;Aravena et al 2016). We use the [CII] luminosity -halo mass relation thus derived to calculate the power spectrum of intensity fluctuations across z ∼ 0 − 6, and forecast its measurement sensitivity by future intensity mapping experiments.…”

User’s guide to extracting cosmological information from line-intensity maps

“…In this case, Eqs. (22), (23), and (24) are still correct, but both the data vector and the covariance matrix need to be changed. The former will include both auto-and cross-power spectra, hence Θ would be the concatenation of Θ XX , Θ XY and Θ Y Y .…”

Evidence for C ii diffuse line emission at redshift z ∼ 2.6

“…C intensity measurement in this work at 95% and 99% c.l. and the theoretical predictions fromGong et al (2012);Silva et al (2015);Pullen et al (2018) .…”

“…IM was originally developed to study 21 cm radiation from reionization but has been applied to mapping other bright lines (Hogan & Rees 1979;Scott & Rees 1990;Madau et al 1997;Suginohara et al 1999;Wyithe et al 2008;Kovetz et al 2017;Chang et al 2008). Pullen et al (2018), hereafter AP2018, sought to measure the intensity of C cumulative emission through cross-correlating intensity maps with other tracers of large-scale structure (LSS). Although AP2018 reported a C intensity brightness at redshift z ∼ 2.6, Bayesian analysis did not show a strong preference for an emission model that requires C versus one without C .…”