The Supersonic Project: rotational effects of supersonic motions on the first structures in the Universe

Abstract

We introduce the "Supersonic Project," aimed at investigating the effects of the supersonic relative velocity between dark matter (DM) and baryons at high redshift using a combination of analytical calculations and cosmological simulations. In this paper, we study the effect of this stream velocity on the angular momentum of the first structures in the early Universe using simulations. We focus on DM haloes and their gas component as well as the recently predicted supersonically-induced gas objects (SIGOs) that arise as a result of the stream velocity phase shift. We find that the spin parameter of the gas component in these first haloes is increased with the stream velocity. Moreover, we find that when the stream velocity is taken into account, the angular momentum vectors of the DM component and the gas component are typically misaligned and this misalignment angle has a nearly isotropic distribution. The spin parameter value of the gas component is higher than in the no stream velocity case, which even in the absence of cooling, may result in more prolate objects. We also generalize the spin parameter to the SIGOs and find that they typically have a larger spin parameter with respect to their dark matter counterparts and that there is no correlation of the spin parameter and the prolateness of such structures. We speculate that SIGOs may be observed as very low luminosity objects in the early Universe and may serve as potential progenitors of Little Blue Dot-like systems.

The Supersonic Project: Shining Light on SIGOs—A New Formation Channel for Globular Clusters

“…The SIGOs are dimmer than the classical objects at the same redshift. Note that, while the simulation snapshot here is associated at z = 20, we expect these objects to continue to form 6 and exist (at least before reionization), based on the agreement between the analytical calculations (Naoz & Narayan 2014) and our simulations (Popa et al 2016;Chiou et al 2018Chiou et al , 2019.. Thus, future JWST observations may be able to disentangle star forming SIGOs from classical objects.…”

“…We then use semi-analytical calculations to determine the luminosities of objects in our simulations. We note that, although we study these objects at z = 20, they still exists at lower redshifts (e.g., Naoz & Narayan 2014;Popa et al 2016;Chiou et al 2018). Thus, their expected luminosities could possibly be detectable with JWST.…”

“…We follow the structure definitions suggested in Chiou et al (2018). In particular, DM-Primary/Gas-Secondary (DM/G) objects are spherical overdensity DM halos that also contain gas.…”

Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes

“…Early studies of this process, based on numerical simulations, indeed suggest that the kinetic energy provided by the streaming velocity provides additional stability. It reduces the baryon overdensity in low-mass halos and delays the onset of cooling, altogether resulting in a larger critical mass for collapse (Greif et al 2011; Stacy, Bromm & Loeb 2011; Maio et al 2011; Naoz, Yoshida, & Gnedin 2012, 2013; O’Leary & McQuinn 2012; Latif, Niemeyer, & Schleicher 2014b; Schauer et al 2017) and different angular momentum evolution of dark matter and dense gas (Chiou et al 2018; Druschke et al 2018). They may also have substantial impact on the resulting cm emission (Fialkov et al 2012; McQuinn 2012; Visbal et al 2012).…”

The Supersonic Project: SIGOs, A Proposed Progenitor to Globular Clusters, and Their Connections to Gravitational-wave Anisotropies

“…These objects, known as supersonically induced gas objects (SIGOs), have since been found in follow-up simulations (Popa et al 2016;Chiou et al 2018Chiou et al , 2019Chiou et al , 2021. However, there are still many outstanding questions about these objects.…”