Related papers: Effect of cosmic ray/X-ray ionization on supermass…
The origin of supermassive black holes (SMBHs) in galactic nuclei is one of the major unsolved problems in astrophysics. One hypothesis is that they grew from >10^5 M_sun black holes that formed in the `direct collapse' of massive gas…
Context. The seeds of the supermassive black holes (SMBHs) with masses of ~10^9 M_Sun observed already at z ~ 6 may have formed through the direct collapse of primordial gas in T_vir >~ 10^4 K halos, whereby the gas must stay hot (~10^4 K)…
Current models of galaxy formation lack an efficient and physically constrained mechanism to regulate star formation (SF) in low and intermediate mass galaxies. We argue that the missing ingredient could be the effect of photoionization by…
The presence of supermassive black holes (SMBHs) of a few billion solar masses at very high redshift has motivated us to study how these massive objects formed during the first billion years after the Big Bang. The most promising model that…
The ability of metal free gas to cool by molecular hydrogen in primordial halos is strongly associated with the strength of ultraviolet (UV) flux produced by the stellar populations in the first galaxies. Depending on the stellar spectrum,…
Explaining the existence of supermassive black holes (SMBHs) larger than $\sim 10^9 M_\odot$ at redshifts $z >\sim 6$ remains an open theoretical question. One possibility is that gas collapsing rapidly in pristine atomic cooling halos…
Direct collapse black holes (DCBHs) formed from the collapse of atomically-cooled primordial gas in the early Universe are strong candidates for the seeds of supermassive BHs. DCBHs are thought to form in atomic cooling haloes in the…
The conditions that affect the formation of stars in radiatively and mechanically active environments are quite different than the conditions that apply to our local interstellar neighborhood. In such galactic environments, a variety of…
Radiative feedback from populations II stars played a vital role in early structure formation. Particularly, photons below the Lyman limit can escape the star forming regions and produce a background ultraviolet (UV) flux which consequently…
Observational studies show that there is a strong link between the formation and evolution of galaxies and the growth of supermassive black holes (SMBH) at their centers. However, the underlying physics of this observed relation is poorly…
We explore the implications of a possible cosmic ray (CR) background generated during the first supernova explosions that end the brief lives of massive Population III stars. We show that such a CR background could have significantly…
The EUV photoionizing radiation and FUV dissociating radiation from newly born stars photoevaporate their parental neutral cloud, leading to the formation of dense clumps that could eventually form additional stars. We study the effects of…
Molecular clouds interacting with supernova remnants may be subject to a greatly enhanced irradiation by cosmic rays produced at the shocked interface between the ejecta and the molecular gas. Over the past decade, broad-band observations…
A massive primordial halo near an intensely star-forming galaxy may collapse into a supermassive star (SMS) and leave a massive black hole seed of about $10^5~M_{\odot}$. To investigate the impact of ionizing radiation on the formation of…
Extreme ultraviolet (EUV) radiations (10--117 nm) from host stars play important roles in the ionization, heating, and mass loss from exoplanet atmospheres. Together with the host star's Lyman-alpha and far-UV (117--170 nm) radiation, EUV…
Thermal and chemical evolution of primordial gas clouds irradiated with far-ultraviolet (FUV; < 13.6 eV) radiation is investigated. In clouds irradiated by intense FUV radiation, sufficient hydrogen molecules to be important for cooling are…
Ultra-violet (UV) radiation from accreting black holes ionizes the intergalactic gas around early quasars, carving out highly ionized bubbles in their surroundings. Any changes in a quasar's luminosity are therefore predicted to produce…
HD dominates the cooling of primordial clouds with enhanced ionization, e.g. shock-heated clouds in structure formation or supernova remnants, relic HII regions of Pop III stars, and clouds with cosmic-ray (CR) irradiation. There, the…
The star formation in molecular clouds is inefficient. The ionizing EUV radiation ($h \nu \geq 13.6$ eV) from young clusters has been considered as a primary feedback effect to limit the star formation efficiency (SFE). We here focus on…
JWST reveals numerous high-z galaxies and Supermassive Black Holes (SMBHs), suggesting that stars and SMBH seeds formation at $z \gtrsim 10$ may be more efficient than previously derived. One popular SMBH seed scenario is the Direct…