arXiv subjects

Muhammad A. Latif

Publications and source records attributed to Muhammad A. Latif.

At least 19 recordsLinked to original sources

arXiv2026

Little Red Dots are Direct-Collapse Black Hole-Forming Galaxies

"Little Red Dots" (LRDs) at $4 < z < 8$ are one of the most challenging discoveries by JWST to date because their distinctive V-shaped spectra and compact morphologies (100 - 200 pc) defy conventional astrophysical interpretation. Previous attempts to explain LRDs as compact stellar systems, heavily-cocooned black holes with differential flows, supermassive stars, or more exotic objects like 'black-hole stars' either cannot show how they formed, explain the origin of the dense shells needed for the absorption features in their spectra, or account for their observed abundances or inferred lifetimes. Here we show that LRDs are simply direct-collapse black hole galaxies in which the BH is still shrouded by the massive disk that created it. Our cosmological simulations yield spectra that are good matches to those of LRDs because high densities at the center of the disk trap X-rays from the BH and produce the observed Balmer absorption features while allowing UV, optical and reprocessed IR flux to partly escape. The host galaxy forms a dense 10$^8$ M$_{\odot}$ cluster of stars with a radius of 150 pc next to the BH, consistent with observations of LRDs. Our models reproduce a wide variety of LRD spectra from typical objects like RUBIES-EGS-42046 at $z = 5.28$ to those with the strongest Balmer breaks such as MoM-BH$^*$-1 at $z = 7.76$ and those at the highest redshifts like CAPERS-LRD-z9 at $z = 9.29$.

astro-ph.GA↗

arXiv2026

Impact of subhalo dynamical friction heating on the formation of the first structures in the universe

We present a model for gas heating, driven by dynamical friction from orbiting subhalos within dark matter halos. Using data from the TNG50 simulation, we derive the subhalo mass function and calculate the dynamical friction heating rate for a wide range of halo masses and redshifts from $z = 15$ to 0. Our results show that, by converting gravitational potential energy into thermal energy, dynamical friction is an important mechanism for galaxy quenching in massive halos at low redshifts, consistent with previous studies. Additionally, we find that in the early universe at $z \sim 15$, heating rates can be comparable to the molecular hydrogen cooling rates in metal-free minihalos. This can suppress gas cooling and fragmentation and does increase the critical molecular fraction for Pop III star formation by up to one order of magnitude, thereby making Pop III star formation more difficult. In combination with the Lyman-Werner background, the dynamical friction heating mechanism favors the formation of direct-collapse black hole (DCBH) seeds in atomic cooling halos, even when the average H$_2$ fraction is $\sim 10^{-5}$ during the minihalo progenitor phase. Dynamical friction heating at a fixed host halo mass can vary by two orders of magnitude due to the scatter in the number of subhalos. To capture dynamical friction heating in simulations, it is necessary to resolve subhalos with a subhalo to host halo mass ratio $ψ\gtrsim 0.05$.

astro-ph.GA↗

arXiv2026

Planet Formation at Cosmic Dawn: Planetesimals in H$_2$O-Rich Disks Around Low-Mass Stars

Primordial, or Pop III, supernovae (SNe) were the first, great nucleosynthetic engines in the Universe, forging the heavy elements required for the later formation of planets, and life. Past studies suggest that the rise of planet formation was gradual, and did not peak until about half of the present age of the Universe after cosmic mean metallicities exceeded a critical value. However, Pop III pair-instability (PI) SNe, which can eject over 100 M$_{\odot}$ of metals, locally enriched gas to metallicities of up to 1 Z$_{\odot}$ at Cosmic Dawn, just 100 Myr after the Big Bang. Here we show that planetesimals, the precursors of terrestrial planets, can form around low-mass, long-lived stars in the debris of such explosions, before the first galaxies and far earlier than previously thought. We modeled the collapse of a dense core with a Jeans mass of just 1 - 2 M$_{\odot}$ from a PI SN remnant and found that a protoplanetary disk formed with several Earth masses of planetesimals 0.5 - 1.0 AU from their parent star, within its water snow line. The disk has H$_2$O mass fractions that are only a factor of a few less than in the Solar System today, raising the possibility of enrichment of the first planets in the Universe with water in direct analogy to Earth in the Solar system.

astro-ph.GA↗

arXiv2026

Little Red Dot progenitors from Compact Starbursts: A Natural Path to Early AGN Formation

The recent discovery of Little Red Dots (LRDs) by the James Webb Space Telescope has challenged traditional models of early galaxy and black hole co-evolution. The nature of these highly compact objects remains heavily debated, with explanations divided between dust-reddened active galactic nuclei (AGN) and extremely dense stellar populations. We perform high-resolution cosmological simulations to model the formation of LRD precursors. Motivated by recent high-redshift observations and theoretical results, we specifically explore environments characterized by high star formation efficiencies (30\% and 100\%) and confined feedback. Our simulations naturally produce highly compact galaxies with stellar masses of $10^7-6 \times 10^8 $\,M$_\odot$, with most of the mass concentrated within $200-300$ pc. We find that, in these dense environments, gas inflows, gravitational torques, and stellar dynamical friction operate on highly efficient timescales. Over a 10 Myr timescale, gas inflows can accumulate $\rm \sim 10^7 M_\odot$ at the galactic center, while gravitational torques and dynamical friction can contribute an additional $10^5-10^9$\,M$_\odot$ and $10^3-10^4$\, M$_\odot$ through the inward migration of massive stars. Assuming a conservative 10\% efficiency to account for feedback, this rapid mass accumulation can lead to the formation of a $\sim 10^6$\,M$_\odot$ central black hole, naturally giving rise to an AGN in these dense systems. Therefore, stellar and AGN interpretations of LRDs may not be mutually exclusive; rather, dense stellar systems are likely precursors to AGN.

astro-ph.GA↗

arXiv2026

How Overmassive Black Holes Formed at Cosmic Dawn

Overmassive black hole galaxies (OBGs) at redshifts $z \sim$ 10, or 450 Myr after the Big Bang, are one of the most puzzling discoveries by the James Webb Space Telescope to date because they formed by such early epochs and their black-hole to stellar mass ratios are a hundred times higher than those in galaxies today. Here we show that OBGs are simply the result of DCBH birth in primordial halos at early times. A 70,000 M$_{\odot}$ DCBH forming at $z =$ 25.7 in our cosmological simulation grows at about half the Eddington rate to $6.0 \times 10^6$ M$_{\odot}$ by $z =$ 10.1. Its host galaxy reaches a stellar mass of $4 \times 10^8$ M$_{\odot}$, a metallicity $Z =$ 0.1 Z$_{\odot}$, a star formation rate of 2 M$_{\odot}$ yr$^{-1}$, and $M_{\rm BH}/M_{\ast}$ $\sim$ 0.01, on par with OBGs like GN-z11, UHZ1, and GHZ9 at $z =$ 10.6, 10.1, and 10.2, respectively. Our simulation, the first to follow the coevolution of a DCBH and its host galaxy for several hundred Myr, shows that this ratio is a natural result of initial suppression of star formation by the DCBH and the later, violent blowout of metals by Pop III supernovae. Our models provide an excellent match to the spectra of UHZ1 and GHZ9 at $z =$ 10.1 and 10.4, respectively.

astro-ph.GA↗

arXiv2026

Massive star clusters detected by JWST as natural birth places to form intermediate-mass black holes

The James Webb Space Telescope (JWST) has detected, through gravitational lensing, several young massive star clusters (YMCs), which are considered as relevant building blocks of high redshift galaxies. In this work, we show how a significant fraction of these YMCs could act as relevant birth places for intermediate-mass black holes. We first consider the formation of massive clusters and show that the population of YMCs is consistent with a steep mass-radius relation, which includes a relevant spread of roughly an order of magnitude. We pursue a comparison of this population with young star clusters in the local Universe and Milky Way globular clusters, including an analysis of the characteristic timescales. The YMCs show a wide spread over these properties, but include systems with both short relaxation times as well as relatively short collision timescales, implying they could go through efficient core collapse, which would lead to runaway collisions. We provide quantitative estimates of the sizes of the clusters that could efficiently form intermediate-mass black holes through a runaway collision-based channel, suggesting that these roughly correspond to the systems beyond the $1σ$ scatter in the mass-radius relation. This implies a fraction of ~16% of YMCs as candidates to form intermediate-mass black holes. We show that above a mass limit of ~6x10^6 M_sun, compact star clusters are likely to retain gas even in the presence of strong supernova feedback, altering the dynamics in the central core and providing the possibility to rapidly grow the central object both via gas dynamical friction and Bondi accretion. Finally, we consider the possibility of a gas-dominated regime, in which strong gravitational torques may inhibit star cluster formation and instead directly form a high-mass black holes, as suggested to have occurred in the infinity galaxy.

astro-ph.GA↗

arXiv2025

1000-10,000 M$_\odot$ Primordial Stars Created the Nitrogen Excess in GS 3073 at $z = 5.55$

The advent of the James Webb Space Telescope has revealed a wealth of new galaxies just a few hundred Myr after the Big Bang. Some of these galaxies exhibit unusual N/O ratios that are difficult to explain with stellar populations today. While Wolf-Rayet stars in multiple-burst populations, very massive or rapidly-rotating primordial stars, general relativistic explosions of metal-enriched supermassive stars, or the precursors of globular clusters can in principle account for the nitrogen excess in the galaxies GN-z11 and CEERS 1019, no known stars or supernovae can explain the far higher N/O ratio of 0.46 in GS 3073 at redshift $z =$ 5.55. Here we show that the extreme nitrogen abundances in GS 3073 can be produced by 1000 - 10,000 M$_{\odot}$ primordial (Pop III) stars. We find that these are the only candidates that can account for its large N/O ratios and its C/O and Ne/O ratios. GS 3073 is thus the first conclusive evidence in the fossil abundance record of the existence of supermassive Pop III stars at cosmic Dawn.

astro-ph.GA↗

arXiv2025

Euclid and Roman with JWST Could Reveal Quasars at up to $z \sim$ 15

Although supermassive black holes (SMBHs) are found at the centers of most galaxies today, over 300 have now been discovered at $z >$ 6, including UHZ1 at $z = 10.1$ and GHZ9 at $z =$ 10.4. They are thought to form when 10$^4$ - 10$^5$ M$_{\odot}$ primordial stars die as direct-collapse black holes (DCBHs) at $z \sim$ 20 - 25. While studies have shown that DCBHs should be visible at birth at $z \gtrsim$ 20 in the near infrared (NIR) to the James Webb Space Telescope (JWST), none have considered SMBH detections at later stages growth down to $z \sim$ 6 - 7. Here, we present continuum NIR luminosities for a BH like ULAS J1120+0641, a $1.35 \times 10^9$ M$_{\odot}$ quasar at $z =$ 7.1, from a cosmological simulation for Euclid, the Roman Space Telescope (RST) and JWST bands from $z =$ 6 - 15. We find that Euclid and RST could detect such BHs, including others like UHZ1 and GHZ9, at much earlier stages of evolution, out to $z \sim$ 14 - 15, and that their redshifts could be confirmed spectroscopically with JWST. Synergies between these three telescopes could thus reveal the numbers of SMBHs at much higher redshifts and discriminate between their evolution pathways because Euclid and RST can capture large numbers of them in wide-field surveys for further study by JWST.

astro-ph.GA↗

arXiv2025

Radio Signatures of a Massive Black Hole in GHZ9 at z $\sim$ 10

Synergies between the {\em James Webb Space Telescope} ({\em JWST}) and the {\em Chandra} X-ray observatory have advanced the observational frontier by detecting a handful of active galactic nuclei (AGNs) beyond $z \sim$ 10. In particular, the recent discovery of a candidate $\rm 8 \times 10^7~M_{\odot}$ black hole (BH) in the galaxy GHZ9 at $z =$ 10.4 favors massive seed formation channels for these objects. Motivated by prospects for their detection in radio by recent studies, we estimate radio fluxes for GHZ9 and explore the possibility of their detection with the Square Kilometer Array (SKA) and next-generation Very Large Array (ngVLA). We find that ngVLA should be able to detect radio emission from GHZ9 for integration times as short as 1 hr while SKA will require integration times of up to 100 hr. We also find that radio emission from the BH can be distinguished from that due to H II regions and supernovae in its host galaxy. The detection of a few hundred nJy radio signal at frequencies $> 2$ GHz will be a smoking gun for the presence of a BH in GHZ9.

astro-ph.GA↗

arXiv2025

Radio emission from little red dots may reveal their true nature

The unprecedented sensitivity of the \textit{James Webb Space Telescope} (\textit{JWST}) has revolutionized our understanding of the early universe. Among the most intriguing \textit{JWST} discoveries are red, very compact objects showing broad line emission features nicknamed as little red dots (LRDs). The discovery of LRDs has triggered great interest about their origin as either extremely starbursting galaxies or highly-obscured active galactic nuclei (AGN). Their exact nature still remains unknown. The goal of this work is to estimate the radio emission from LRDs and predict which radio surveys would detect them. To achieve these objectives, we employ the fundamental plane of black hole (BH) accretion to estimate radio emission from AGN and the stellar radio fluxes from their host galaxies. We assume a range of BH mass, X-ray luminosity ($\rm L_{X}$) and star formation rate (SFR) to bracket the likely properties of LRDs. Our findings suggest that BH radio fluxes from LRDs are 10-100 times higher than the stellar fluxes from their host galaxies, depending on BH mass, $\rm L_X$ and SFR. The detection of a $\sim$ 500 nJy signal above 2 GHz at $z \geq$ 5 or a $\sim$ 2000 nJy flux at $z =$ 3-4 would be a smoking gun for the presence of AGN provided that SFRs in the host galaxies are $\rm < 30~ M_{\odot} ~yr^{-1}$. We find that LRDs are most likely radio quiet AGN otherwise would have been already detected in the current radio surveys. Our findings suggest that LRDs can be detected with the upcoming radio observatories such as ngVLA and SKA with integration times of 10-100 hrs, respectively.

astro-ph.GA↗

arXiv2025

Massive black holes or stars first: the key is the residual cosmic electron fraction

Recent James Webb Space Telescope observations have unveiled that the first supermassive black holes (SMBHs) were in place at z $\geq$ 10, a few hundred Myrs after the Big Bang. These discoveries are providing strong constraints on the seeding of BHs and the nature of the first objects in the Universe. Here, we study the impact of the freeze-out electron fractions ($f_e$) at the end of the epoch of cosmic recombination on the formation of the first structures in the Universe. At $f_e$ below the current fiducial cosmic values of $\rm \sim 10^{-4}$, the baryonic collapse is delayed due to the lack of molecular hydrogen cooling until the host halo masses are increased by one to two orders of magnitude compared to the standard case and reach the atomic cooling limit. This results in an enhanced enclosed gas mass by more than an order of magnitude and higher inflow rates of up to $0.1~M_{\odot}/{yr}$. Such conditions are conducive to the formation of massive seed BHs with $\sim 10^{4}$ M$_{\odot}$. Our results reveal a new pathway for the formation of massive BH seeds which may naturally arise from free

astro-ph.CO↗

arXiv2025

Abundant Water from Early Supernovae at Cosmic Dawn

Primordial (or Pop III) supernovae were the first nucleosynthetic engines in the Universe, forging the heavy elements required for the later formation of planets and life. Water, in particular, is thought to be crucial to the cosmic origins of life as we understand it, and recent models have shown that water can form in low-metallicity gas like that present at high redshifts. Here we present numerical simulations that show that the first water in the Universe formed in Pop III core-collapse and pair-instability supernovae at redshifts $z \sim$ 20. The primary sites of water production in these remnants are dense molecular cloud cores, which in some cases were enriched with primordial water to mass fractions that were only a factor of a few below those in the Solar System today. These dense, dusty cores are also likely candidates for protoplanetary disk formation. Besides revealing that a primary ingredient for life was already in place in the Universe 100 - 200 Myr after the Big Bang, our simulations show that water was likely a key constituent of the first galaxies.

astro-ph.GA↗

arXiv2024

Radio Emission from High-Redshift Active Galactic Nuclei in the JADES and CEERS Surveys

Recent calculations indicate that radio emission from quasars at $z \sim$ 6 - 7 could be detected at much earlier stages of evolution, at $z \sim$ 14 - 15, by the Next-Generation Very Large Array (ngVLA) and the Square Kilometer Array (SKA). However, the {\em James Webb Space Telescope} has now discovered less luminous active galactic nuclei (AGNs) at $z >$ 4 and a few massive black holes (BHs) at $z >$ 10, which may be the progenitors of supermassive black holes (SMBHs) but at different stages of growth. Radio detections of these new AGNs would provide complementary measures of their properties and those of their host galaxies. Here we estimate radio flux densities for 19 new AGNs found by the JADES, CEERS and UNCOVER surveys. We find that ngVLA should be able to detect most of these sources in targeted surveys with integration times of 10 - 100 hr (and in just 1 hr for a few of them) but most would require at least 100 hr of SKA time in spite of its greater sensitivities at low frequencies. In some cases, radio emission from the BH can be distinguished from that of H II regions and supernovae in their host galaxies, which could be used to estimate their star formation rates. Such detections would be yet another example of the useful synergies between near infrared and radio telescopes in SMBH science in the coming decade.

astro-ph.GA↗

arXiv2023

Radio Emission From a $z =$ 10.1 Black Hole in UHZ1

The recent discovery of a 4 $\times$ 10$^7$ M$_{\odot}$ black hole (BH) in UHZ1 at $z =$ 10.3, just 450 Myr after the big bang, suggests that the seeds of the first quasars may have been direct-collapse black holes (DCBHs) from the collapse of supermassive primordial stars at $z \sim$ 20. This object was identified in James Webb Space Telescope (JWST) NIRcam and Chandra X-ray data, but recent studies suggest that radio emission from such a BH should also be visible to the Square Kilometer Array (SKA) and the next-generation Very Large Array (ngVLA). Here, we present estimates of radio flux densities for UHZ1 from 0.1 - 10 GHz, and find that SKA and ngVLA could detect it with integration times of 10 - 100 hr and just 1 - 10 hr, respectively. It may be possible to see this object with VLA now with longer integration times. The detection of radio emission from UHZ1 would be a first test of exciting new synergies between near infrared (NIR) and radio observatories that could open the era of $z \sim$ 5 - 15 quasar astronomy in the coming decade.

astro-ph.GA↗

arXiv2023

Radio Emission from the First Quasars at $z \sim$ 6-15

Nearly 300 quasars have now been found at $z >$ 6, including nine at $z >$ 7. They are thought to form from the collapse of supermassive primordial stars to 10$^4$ - 10$^5$ M$_{\odot}$ black holes at $z \sim$ 20 - 25, which then rapidly grow in the low-shear environments of rare, massive halos fed by strong accretion flows. Sensitive new radio telescopes such as the Next-Generation Very Large Array (ngVLA) and the Square Kilometer Array (SKA) could probe the evolution of these objects at much earlier times. Here, we estimate radio flux from the first quasars at $z \sim$ 6 - 15 at 0.5 - 12.5 GHz. We find that SKA and ngVLA could detect a quasar like ULAS J1120+0641, a 1.35 $\times$ 10$^9$ M$_{\odot}$ black hole at $z =$ 7.1, at much earlier stages of evolution, $z \sim$ 14 - 15, with 100 hr integration times in targeted searches. The advent of these new observatories, together with the James Webb Space Telescope (JWST), Euclid, and the Roman Space Telescope (RST), will inaugurate the era of $z \lesssim$ 15 quasar astronomy in the coming decade.

astro-ph.GA↗

arXiv2023

Magnetic braking during direct collapse black hole formation

Magnetic fields are expected to be efficiently amplified during the formation of the first massive black holes via the small-scale dynamo and in the presence of strong accretion shocks occurring during gravitational collapse. Here, we analyze high-resolution cosmological magneto-hydrodynamical simulations of gravitational collapse in atomic cooling halos, exploring the dynamical role of magnetic fields, particularly concerning the effect of magnetic braking and angular momentum transport. We find that after the initial amplification, magnetic fields contribute to the transport of angular momentum and reduce it compared to pure hydrodynamical simulations. However, the magnetic and Reynolds torques do not fully compensate for the inward advection of angular momentum, which still accumulates over timescales of $\sim1$~Myr. A Jeans analysis further shows that magnetic pressure strongly contributes to suppressing fragmentation on scales of $0.1-10$~pc. Overall, the presence of magnetic fields thus aids in the transport of angular momentum and favors the formation of massive objects.

astro-ph.HE↗

arXiv2023

Role of magnetic fields in the formation of direct collapse black holes

Direct collapse black holes (DCBHs) are the leading candidates for the origin of the first supermassive black holes. However, the role of magnetic fields during their formation is still unclear as none of the previous studies has been evolved long enough to assess their impact during the accretion phase. Here, we report the results from a suite of 3D cosmological magneto-hydrodynamic (MHD) simulations which are evolved for 1.6 Myrs comparable to the expected lifetime of supermassive stars (SMSs). Our findings suggest that magnetic fields are rapidly amplified by strong accretion shocks irrespective of the initial magnetic field strength and reach the saturation state. They stabilize the accretion disks and significantly reduce fragmentation by enhancing the Jeans mass in comparison with pure hydrodynamical runs. Although the initial clump masses are larger in MHD runs, the rapid coalescence of clumps in non-MHD cases due to the higher degree of fragmentation results in similar masses. Overall, the central clumps have masses of $\rm 10^5~M_{\odot}$ and the mean mass accretion rates of $\rm \sim 0.1 ~M_{\odot}/yr$ are similar in both MHD and non-MHD cases. The multiplicity of SMSs is significantly reduced in MHD simulations. Such strongly amplified magnetic fields are expected to launch Jets and outflows which may be detected with upcoming radio telescopes.

astro-ph.HE↗

arXiv2022

Public Release of A-SLOTH: Ancient Stars and Local Observables by Tracing Halos

The semi-analytical model A-SLOTH (Ancient Stars and Local Observables by Tracing Halos) is the first public code that connects the formation of the first stars and galaxies to observables. After several successful projects with this model, we publish the source code and describe the public version in this paper. The model is based on dark matter merger trees that can either be generated based on Extended Press-Schechter theory or that can be imported from dark matter simulations. On top of these merger trees, A-SLOTH applies analytical recipes for baryonic physics to model the formation of both metal-free and metal-poor stars and the transition between them with unprecedented precision and fidelity. A-SLOTH samples individual stars and includes radiative, chemical, and mechanical feedback. It is calibrated based on six observables, such as the optical depth to Thomson scattering, the stellar mass of the Milky Way and its satellite galaxies, the number of extremely-metal poor stars, and the cosmic star formation rate density at high redshift. A-SLOTH has versatile applications with moderate computational requirements. It can be used to constrain the properties of the first stars and high-z galaxies based on local observables, predicts properties of the oldest and most metal-poor stars in the Milky Way, can serve as a subgrid model for larger cosmological simulations, and predicts next-generation observables of the early Universe, such as supernova rates or gravitational wave events.

astro-ph.GA↗