Title: Evaluating the QSO contribution to the 21-cm signal from the Cosmic Dawn

Abstract

The upcoming radio interferometer Square Kilometre Array (SKA) is expected to directly detect the redshifted 21-cm signal from the neutral hydrogen present during the Cosmic Dawn. Temperature fluctuations from X-ray heating of the neutral intergalactic medium can dominate the fluctuations in the 21-cm signal from this time. This heating depends on the abundance, clustering, and properties of the X-ray sources present, which remain highly uncertain. We present a suite of three new large-volume, 349\,Mpc a side, fully numerical radiative transfer simulations including QSO-like sources, extending the work previously presented in Ross et al. (2017). The results show that our QSOs have a modest contribution to the heating budget, yet significantly impact the 21-cm signal. Initially, the power spectrum is boosted on large scales by heating from the biased QSO-like sources, before decreasing on all scales. Fluctuations from images of the 21-cm signal with resolutions corresponding to SKA1-Low at the appropriate redshifts are well above the expected noise for deep integrations, indicating that imaging could be feasible for all the X-ray source models considered. The most notable contribution of the QSOs is a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm probability distribution functions. Furthermore, in the case of late Lyman-$$\alpha$$ saturation, this non-Gaussianity could be dramatically decreased particularly when heating occurs earlier. We conclude that increased non-Gaussianity is a promising signature of rare X-ray sources at this time, provided that Lyman-$$\alpha$$ saturation occurs before heating dominates the 21-cm signal.

Authors:

Ross, Hannah E.  ^[1];

• Search DOE PAGES for author "Ross, Hannah E."
• Search DOE PAGES for ORCID "0000-0001-9646-793X"
• Search orcid.org for ORCID "0000-0001-9646-793X"

Dixon, Keri L.  ^[2];

• Search DOE PAGES for author "Dixon, Keri L."
• Search DOE PAGES for ORCID "0000-0001-9311-1639"
• Search orcid.org for ORCID "0000-0001-9311-1639"

Ghara, Raghunath  ^[3];

• Search DOE PAGES for author "Ghara, Raghunath"
• Search DOE PAGES for ORCID "0000-0001-9816-5070"
• Search orcid.org for ORCID "0000-0001-9816-5070"

Iliev, Ilian T.  ^[4];

• Search DOE PAGES for author "Iliev, Ilian T."
• Search DOE PAGES for ORCID "0000-0002-5174-1365"
• Search orcid.org for ORCID "0000-0002-5174-1365"

Mellema, Garrelt  ^[3]

• Search DOE PAGES for author "Mellema, Garrelt"
• Search DOE PAGES for ORCID "0000-0002-2512-6748"
• Search orcid.org for ORCID "0000-0002-2512-6748"

---

+ Show Author Affiliations

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Sussex, Brighton (United Kingdom); Stockholm Univ., Stockholm (Sweden)
2. Univ. of Sussex, Brighton (United Kingdom); New York Univ. Abu Dhabi, Abu Dhabi (United Arab Emirates)
3. Stockholm Univ., Stockholm (Sweden)
4. Univ. of Sussex, Brighton (United Kingdom)

Publication Date:

2019-05-04

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1564050

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Monthly Notices of the Royal Astronomical Society

Additional Journal Information:

Journal Volume: 487; Journal Issue: 1; Journal ID: ISSN 0035-8711

Publisher:

Royal Astronomical Society

Country of Publication:

United States

Language:

English

Subject:

79 ASTRONOMY AND ASTROPHYSICS; radiative transfer; cosmology: dark ages; reionizaion; first stars; galaxies: quasars: general; intergalactic medium; cosmology: theory; cosmology: large-scale structure of Universe