HI galaxy simulations for the SKA: number counts and bias

It is broadly accepted that Supermassive Black Holes (SMBHs) are located in the centers of most massive galaxies, although there is still no convincing scenario for the origin of their massive seeds. It has been suggested that primordial black holes (PBHs) of masses 10 2 M may provide such seeds, which would grow to become SMBHs. We suggest an observational test to constrain this hypothesis: gas accretion around PBHs during the cosmic dark ages powers the emission of high energy photons which would modify the spin temperature as measured by 21cm Intensity Mapping (IM) observations. We model and compute their contribution to the standard sky-averaged signal and power spectrum of 21cm IM, accounting for its substructure and angular dependence for the first time. If PBHs exist, the sky-averaged 21cm IM signal in absorption would be higher, while we expect an increase in the power spectrum for 10 2 − 10 3 . We also forecast PBH detectability and measurement errors in the abundance and Eddington ratios for different fiducial parameter configurations for various future experiments, ranging from SKA to a futuristic radio array on the dark side of the Moon. While the SKA could provide a detection, only a more ambitious experiment would provide accurate measurements.

Section: Introductionmentioning

confidence: 99%

Signatures of primordial black holes as seeds of supermassive black holes

Bernal

Raccanelli

Verde

et al. 2018

“…[79] for WFIRST, and for the SKA HI we extract our catalog from the S 3 -SAX part of the S 3 simulation 4 , using a flux limit S of 1 µJy, which yields observations of over a billion objects over 30,000 deg 2 of the sky (see also Ref. [83] for more details about redshift distributions and biases of the SKA at different flux limits).…”

Section: B Galaxy Clusteringmentioning

confidence: 99%

Towards a measurement of the spectral runnings

Muñoz

Kovetz

Raccanelli

et al. 2017

Single-field slow-roll inflation predicts a nearly scale-free power spectrum of perturbations, as observed at the scales accessible to current cosmological experiments. This spectrum is slightly red, showing a tilt (1 − ns) ∼ 0.04. A direct consequence of this tilt are nonvanishing runnings αs = dns/d log k, and βs = dαs/d log k, which in the minimal inflationary scenario should reach absolute values of 10 −3 and 10 −5 , respectively. In this work we calculate how well future surveys can measure these two runnings. We consider a Stage-4 (S4) CMB experiment and show that it will be able to detect significant deviations from the inflationary prediction for αs, although not for βs. Adding to the S4 CMB experiment the information from a WFIRST-like or a DESI-like survey improves the sensitivity to the runnings by ∼ 20%, and 30%, respectively. A spectroscopic survey with a billion objects, such as the SKA, will add enough information to the S4 measurements to allow a detection of αs = 10 −3 , required to probe the single-field slow-roll inflationary paradigm. We show that only a very-futuristic interferometer targeting the dark ages will be capable of measuring the minimal inflationary prediction for βs. The results of other probes, such as a stochastic background of gravitational waves observable by LIGO, the Ly-α forest, and spectral distortions, are shown for comparison. Finally, we study the claims that large values of βs, if extrapolated to the smallest scales, can produce primordial black holes of tens of solar masses, which we show to be easily testable by the S4 CMB experiment.

“…We have used the specifications from the relevant chapter of the SKA Science Book [46]. The models for the number counts per redshift per deg 2 and the bias of the HI galaxy distribution are obtained in [69,70] by fitting the simulated data:…”

Section: Ska2 Hi Galaxy Redshift Surveymentioning

confidence: 99%

Probing primordial features with next-generation photometric and radio surveys

Ballardini

Finelli⋆

Maartens

et al. 2018

We investigate the possibility of using future photometric and radio surveys to constrain the power spectrum of primordial fluctuations that is predicted by inflationary models with a violation of the slow-roll phase. We forecast constraints with a Fisher analysis on the amplitude of the parametrized features on ultra-large scales, in order to assess whether these could be distinguishable over the cosmic variance. We find that the next generation of photometric and radio surveys has the potential to test these models at a sensitivity better than current CMB experiments and that the synergy between galaxy and CMB observations is able to constrain models with many extra parameters. In particular, an SKA continuum survey with a huge sky coverage and a flux threshold of a few µJy could confirm the presence of a new phase in the early Universe at more than 3σ.