Star Formation Rate Research Articles

Evolution of the star formation rate and Sigma_SFR of galaxies at cosmic morning (4<z<10)

The galaxy-integrated star formation rate (SFR) surface density measurement ($ SFR $) has been proposed as a valuable diagnostic of the mass accumulation in galaxies given it is more tightly related to the physics of star formation and stellar feedback than other indicators. In this work, we assembled a statistical sample of $230$ galaxies observed with JWST in the GLASS and CEERS spectroscopic surveys to estimate Balmer line-based dust attenuations and SFRs (i.e., from Halpha , Hbeta , and Hgamma ), along with the UV rest-frame effective radii. We studied the evolution of galaxy SFR and $ SFR $ in the first $1.5$ billion years of our Universe, from a redshift of $z to $z We found that $ SFR $ is mildly increasing with redshift with a linear slope of $0.16 0.06$. We explored the dependence of SFR and $ SFR $ on stellar mass, showing that a star-forming main sequence and a $ SFR $ main sequence are present out to $z=10$. This dependence exhibits a similar slope compared to the same relations at lower redshifts, but with a higher normalization. We find that the specific SFR (sSFR) and $ SFR $ are correlated with the ratio and with indirect estimates of the escape fraction of Lyman continuum photons; hence, they are likely to play an important role in the evolution of ionization conditions at higher redshifts and in the escape of ionizing radiation. We also searched for spectral outflow signatures in the Halpha and emission lines in a subset of galaxies observed at high resolution (R$=2700$) by the GLASS survey, finding an outflow incidence of $2/11$ 32<!PCT!> 9<!PCT!> $) at $z<6$, but no evidence at $z>6$ ($0/6$, $<26<!PCT!>$). Finally, we find a positive correlation between A$_V$ and $ SFR $, and a flat trend as a function of sSFR, indicating that there is no evidence of a drop in A$_V$ in extremely star-forming galaxies between $z 4$ and $ 10$. This result might be at odds with a dust-clearing outflow scenario, which may instead take place at redshifts of $z 10$, as suggested by some theoretical models.

The MAGPI survey: The interdependence of the mass, star formation rate, and metallicity in galaxies at z~0.3

Star formation rates (SFRs), gas-phase metallicities, and stellar masses are crucial for studying galaxy evolution. The different relations resulting from these properties give insights into the complex interplay of gas inside galaxies and their evolutionary trajectory and current characteristics. We aim to characterize these relations at $z 0.3$, corresponding to a 3-4 Gyr lookback time, to gather insight into the galaxies' redshift evolution. We utilized optical integral field spectroscopy data from 65 emission-line galaxies from the MUSE large program MAGPI at a redshift of $0.28<z<0.35$ (average redshift of $z 0.3$) and spanning a total stellar mass range of $8.2< /M_ odot ) < 11.4$. We measured emission line fluxes and stellar masses, allowing us to determine spatially resolved SFRs, gas-phase metallicities, and stellar mass surface densities. We derived the resolved star formation main sequence (rSFMS), resolved mass metallicity relation (rMZR), and resolved fundamental metallicity relation (rFMR) at $z 0.3$, and compared them to results for the local Universe. We find a relatively shallow rSFMS slope of $ 0.014$ compared to the expected slope at this redshift for an ordinary least square (OLS) fitting routine. For an orthogonal distance regression (ODR) routine, a much steeper slope of $ 0.022$ is measured. We confirm the existence of an rMZR at $z 0.3$ with an average metallicity located $ 0.03$ dex above the local Universe's metallicity. Via partial correlation coefficients, evidence is found that the local metallicity is predominantly determined by the stellar mass surface density and has a weak secondary (inverse) dependence on the SFR surface density $ SFR $. Additionally, a significant dependence of the local metallicity on the total stellar mass $M_ $ is found. Furthermore, we find that the stellar mass surface density $ $ and $M_ $ have a significant influence in determining the strength with which $ SFR $ correlates with the local metallicity. We observe that at lower stellar masses, there is a tighter correlation between $ SFR $ and the gas-phase metallicity, resulting in a more pronounced rFMR.

PHANGS-MeerKAT and MHONGOOSE HI observations of nearby spiral galaxies: Physical drivers of the molecular gas fraction, Rmol

The molecular-to-atomic gas ratio is crucial to our understanding of the evolution of the interstellar medium (ISM) in galaxies. We investigated the balance between the atomic ( and molecular gas ( surface densities in eight nearby star-forming galaxies using new high-quality observations from MeerKAT and ALMA (for and CO, respectively). We defined the molecular gas ratio as mol and measured how depends on local conditions in the galaxy disks using multiwavelength observations. We find that, depending on the galaxy is detected at out to $20-120$\,kpc in galactocentric radius gal $). The typical radius at which reaches 1 is hi kpc, which corresponds to $1-3$ times the optical radius $). We note that, $R_ mol $ correlates best with the dynamical equilibrium pressure, P$_ DE $, among potential drivers studied, with a median correlation coefficient of $ Correlations between mol $ and the star formation rate surface density, total gas surface density, stellar surface density, metallicity, and (a proxy for the combined effect of the UV radiation field and number density) are present but somewhat weaker. Our results also show a direct correlation between and $ SFR $, supporting self-regulation models. Quantitatively, we measured similar scalings as previous works, and attribute the modest differences that we do find to the effect of varying resolution and sensitivity. At $r_ gal gtrsim 0.4 r_ $, atomic gas dominates over molecular gas among our studied galaxies, and at the balance of these two gas phases ($R_ mol $ = 1), we find that the baryon mass is dominated by stars, with Our study constitutes an important step in the statistical investigation of how local galaxy properties (stellar mass, star formation rate, or morphology) impact the conversion from atomic to molecular gas in nearby galaxies.

The Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER). VI. The High-mass Stellar Initial Mass Function of M33

We measure the high-mass stellar initial mass function (IMF) from resolved stars in M33 young stellar clusters. Leveraging the Hubble Space Telescope’s high resolving power, we fully model the IMF probabilistically. We first model the optical color–magnitude diagram of each cluster to constrain its power-law slope Γ, marginalized over other cluster parameters in the fit (e.g., cluster age, mass, and radius). We then probabilistically model the distribution of mass function (MF) slopes for a highly strict cluster sample of nine clusters more massive than log(Mass/M ⊙) = 3.6; above this mass, all clusters have well-populated main sequences of massive stars and should have accurate recovery of their MF slopes, based on extensive tests with artificial clusters. We find that the ensemble IMF is best described by a mean high-mass slope of Γ¯=1.49±0.18 , with an intrinsic scatter of σΓ2=0.020.00+0.16 , consistent with a universal IMF. We find no dependence of the IMF on environmental impacts such as the local star formation rate (SFR) or galactocentric radius within M33, which serves as a proxy for metallicity. This Γ¯ measurement is consistent with similar measurements in M31, despite M33 having a much higher SFR intensity. While this measurement is formally consistent with the canonical Kroupa (Γ = 1.30) IMF, as well as the Salpeter (Γ = 1.35) value, it is the second Local Group cluster sample to show evidence for a somewhat steeper high-mass IMF slope. We explore the impacts a steeper IMF slope has on a number of astronomical subfields.

The FLAMINGO simulation view of cluster progenitors observed in the epoch of reionization with JWST

ABSTRACT Motivated by the recent JWST discovery of galaxy overdensities during the Epoch of Reionzation, we examine the physical properties of high-z protoclusters and their evolution using the Full-hydro Large-scale structure simulations with All-sky Mapping for the Interpretation of Next Generation Observations (FLAMINGO) simulation suite. We investigate the impact of the apertures used to define protoclusters, because the heterogeneous apertures used in the literature have limited our understanding of the population. Our results are insensitive to the uncertainties of the subgrid models at a given resolution, whereas further investigation into the dependence on numerical resolution is needed. When considering galaxies more massive than $M_\ast \, {\simeq }\, 10^8\, {\rm M_\odot }$, the FLAMINGO simulations predict a dominant contribution from progenitors similar to those of the Coma cluster to the cosmic star formation rate density during the reionization epoch. Our results indicate the onset of suppression of star formation in the protocluster environments as early as $z\, {\simeq }\, 5$. The galaxy number density profiles are similar to NFW (Navarro–Frenk–White profile) at $z\, {\lesssim }\, 1$ while showing a steeper slope at earlier times before the formation of the core. Different from most previous simulations, the predicted star formation history for individual protoclusters is in good agreement with observations. We demonstrate that, depending on the aperture, the integrated physical properties including the total (dark matter and baryonic) mass can be biased by a factor of 2 to 5 at $z\, {=}\, 5.5$–7, and by an order of magnitude at $z\, {\lesssim }\, 4$. This correction suffices to remove the ${\simeq }\, 3\, \sigma$ tensions with the number density of structures found in recent JWST observations.

The COS-Holes Survey: Connecting Galaxy Black Hole Mass with the State of the CGM

We present an analysis of Hubble Space Telescope COS/G160M observations of C IV in the inner circumgalactic medium (CGM) of a novel sample of eight z ∼ 0, L ≈ L ⋆ galaxies, paired with UV-bright QSOs at impact parameters (R proj) between 25 and 130 kpc. The galaxies in this stellar-mass-controlled sample (log10 M ⋆/M ⊙ ∼ 10.2–10.9 M ⊙) host supermassive black holes (SMBHs) with dynamically measured masses spanning log10 M BH/M ⊙ ∼ 6.8–8.4; this allows us to compare our results with models of galaxy formation where the integrated feedback history from the SMBH alters the CGM over long timescales. We find that the C IV column density measurements (N C IV; average log10 N C IV,CH = 13.94 ± 0.09 cm−2) are largely consistent with existing measurements from other surveys of N C IV in the CGM (average log10 N C IV,Lit = 13.90 ± 0.08 cm−2), but do not show obvious variation as a function of the SMBH mass. By contrast, specific star formation rate (sSFR) is highly correlated with the ionized content of the CGM. We find a large spread in sSFR for galaxies with log10 M BH/M ⊙ > 7.0, where the CGM C IV content shows a clear dependence on galaxy sSFR but not M BH. Our results do not indicate an obvious causal link between CGM C IV and the mass of the galaxy’s SMBH; however, through comparisons to the EAGLE, Romulus25, and IllustrisTNG simulations, we find that our sample is likely too small to constrain such causality.

The ALMA-ALPAKA survey. II. Evolution of turbulence in galaxy disks across cosmic time: Difference between cold and warm gas

The gas in the interstellar medium (ISM) of galaxies is supersonically turbulent. Measurements of turbulence typically rely on cold gas emission lines for low-$z$ galaxies and warm ionized gas observations for $z > 0$ galaxies. Studies of warm gas kinematics at $z > 0$ conclude that the turbulence strongly evolves as a function of redshift, due to the increasing impact of gas accretion and mergers in the early Universe. However, recent findings suggest potential biases in turbulence measurements derived from ionized gas at high-$z$, impacting our understanding of turbulence origin, ISM physics and disk formation. We investigate the evolution of turbulence using velocity dispersion (sigma ) measurements from cold gas tracers (i.e., CO CI CII ). The initial dataset comprises 17 galaxy disks with high data quality from the ALPAKA sample, supplemented with galaxies from the literature, resulting in a sample of 57 galaxy disks spanning the redshift range $z = 0 - 5$. This extended sample consists of main-sequence and starburst galaxies with stellar masses $ M_ odot $. The comparison with current Halpha kinematic observations and existing models demonstrates that the velocity dispersion inferred from cold gas tracers differ by a factor of $ 3$ from those obtained using emission lines tracing the warm, ionized gas. We show that stellar feedback is the main driver of turbulence measured from cold gas tracers and the physics of turbulence driving does not appear to evolve with time. This is fundamentally different from the conclusions of studies based on warm gas, which had to consider additional turbulence drivers to explain the high values of sigma . We present a model predicting the redshift evolution of turbulence in galaxy disks, attributing the increase of sigma with redshift to the higher energy injected by supernovae due to the elevated star-formation rate in high-$z$ galaxies. This supernova-driven model suggests that turbulence is lower in galaxies with lower stellar mass compared to those with higher stellar mass. Additionally, it forecasts the evolution of sigma in Milky-Way like progenitors.

Cosmic Type Ia supernova rate and constraints on supernova Ia progenitors

Type Ia supernovae play a key role in the evolution of galaxies by polluting the interstellar medium with a fraction of iron peak elements larger than that released in the core-collapse supernova events. Their light curve, moreover, is widely used in cosmological studies as it constitutes a reliable distance indicator on extragalactic scales. Among the mechanisms proposed to explain the Type Ia supernovae (SNe), the single- and double-degenerate channels are thought to be the dominant ones, which implies a different distribution of time delays between the progenitor formation and the explosion. In this paper, we aim to determine the dominant mechanism by comparing a compilation of Type Ia SN rates with those computed from various cosmic star-formation histories coupled with different delay-time distribution functions. We also evaluate the relative contributions of both channels. By using a least-squares fitting procedure, we modeled the observations of Type Ia SN rates assuming different combinations of three recent cosmic star-formation rates and seven delay-time distributions. The goodness of these fits are statistically quantified by the $ test. For two of the three cosmic star-formation rates, the single degenerate scenario provides the most accurate explanation for the observations, while a combination of 34<!PCT!> single-degenerate- and 66<!PCT!> double-degenerate delay-time distributions is more plausible for the remaining tested cosmic star-formation rates. Though dependent on the assumed cosmic star-formation rate, we find arguments in favor of the single-degenerate model. From the theoretic point of view, at least sim 34<!PCT!> of the Type Ia SN must have been produced through the single-degenerate channel to account for the observations. The wide, double-degenerate mechanism slightly under-predicts the observations at redshift $z 1$, unless the cosmic SFR flattens in that regime. On the contrary, although the purely close double-degenerate scenario can be ruled out, we cannot rule out a mixed scenario with single- and double-degenerate progenitors.

Tests of subgrid models for star formation using simulations of isolated disc galaxies

ABSTRACT We use smoothed particle hydrodynamics simulations of isolated Milky Way-mass disc galaxies that include cold, interstellar gas to test subgrid prescriptions for star formation (SF). Our fiducial model combines a Schmidt law with a gravitational instability criterion, but we also test density thresholds and temperature ceilings. While SF histories are insensitive to the prescription for SF, the Kennicutt–Schmidt (KS) relations between SF rate and gas surface density can discriminate between models. We show that our fiducial model, with an SF efficiency per free-fall time of 1 per cent, agrees with spatially resolved and azimuthally averaged observed KS relations for neutral, atomic, and molecular gas. Density thresholds do not perform as well. While temperature ceilings selecting cold, molecular gas can match the data for galaxies with solar metallicity, they are unsuitable for very low-metallicity gas and hence for cosmological simulations. We argue that SF criteria should be applied at the resolution limit rather than at a fixed physical scale, which means that we should aim for numerical convergence of observables rather than of the properties of gas labelled as star-forming. Our fiducial model yields good convergence when the mass resolution is varied by nearly 4 orders of magnitude, with the exception of the spatially resolved molecular KS relation at low surface densities. For the gravitational instability criterion, we quantify the impact on the KS relations of gravitational softening, the SF efficiency, and the strength of supernova feedback, as well as of observable parameters such as the inclusion of ionized gas, the averaging scale, and the metallicity.

Realistic simulated galaxies form [α/Fe]–[Fe/H] knees due to a sustained decline in their star formation rates

ABSTRACT We examine the stellar [$\alpha$/Fe]–[Fe/H] distribution of $\simeq 1000$ present-day galaxies in a high-resolution EAGLE simulation. Roughly half of the galaxies exhibit the canonical distribution, characterized by a sequence of low-metallicity stars with high [$\alpha$/Fe] that transitions at a ‘knee’ to a sequence of declining [$\alpha$/Fe] with increasing metallicity. This population yields a knee metallicity–galaxy–mass relation similar to that observed in Local Group galaxies, both in slope and scatter. However, many simulated galaxies lack a knee or exhibit more complicated distributions. Knees are found only in galaxies with star formation histories (SFHs) featuring a sustained decline from an early peak ($t\simeq 7~{\rm Gyr}$), which enables enrichment by Type Ia supernovae to dominate that due to Type II supernovae (SN II), reducing [$\alpha$/Fe] in the interstellar gas. The simulation thus indicates that, contrary to the common interpretation implied by analytic galactic chemical evolution (GCE) models, knee formation is not a consequence of the onset of enrichment by SN Ia. We use the SFH of a simulated galaxy exhibiting a knee as input to the vice GCE model, finding it yields an $\alpha$-rich plateau enriched only by SN II, but the plateau comprises little stellar mass and the galaxy forms few metal-poor ([Fe/H] $\lesssim$$-$1) stars. This follows from the short constant gas consumption time-scale typically assumed by GCEs, which implies the presence of a readily enriched low-mass gas reservoir. When an initially longer, evolving consumption time-scale is adopted, vice reproduces the simulated galaxy’s track through the [$\alpha$/Fe]–[Fe/H] plane and its metallicity distribution function.

Non-monotonic relations of galaxy star formation, radius, and structure at fixed stellar mass

ABSTRACT We investigate the relation between galaxy structure and star formation rate (SFR) in a sample of $\sim 2.9\times 10^{4}$ central galaxies with $z\lt 0.0674$ and axial ratios $b/a\gt 0.5$. The star-forming main sequence (SFMS) shows a bend around the stellar mass of $M_\ast \le {}M_c=2\times 10^{10}{}{\rm M}_{\odot }$. At $M_\ast \le {}M_c$, the SFMS follows a power-law $\text{SFR}\propto {}M_\ast ^{0.85}$, while at higher masses it flattens. $M_c$ corresponds to a dark matter halo mass of $M_\text{vir}\sim {}10^{11.8}{\rm M}_{\odot }$ where virial shocks occurs. Some galaxy structure (e.g. half-light radius, $R_e$) exhibits a non-monotonic dependence across the SFMS at a fixed $M_\ast$. We find $\text{SFR}\propto {R_e^{-0.28}}$ at fixed $M_\ast$, consistent with the global Kennicutt–Schmidt (KS) law. This finding suggests that galaxy sizes contribute to the scatter of the SFMS. However, at $M_\ast \gt M_c$ the relationship between SFR and $R_e$ diminishes. Low-mass galaxies above the mean of the SFMS have smaller radii, exhibit compact and centrally concentrated profiles resembling green valley (GV) and quiescent galaxies at the same mass, and have higher $M_{\text{H}_2}{/}M_\rm{H\,{\small I}}$. Conversely, those below the SFMS exhibit larger radii, lower densities, have no GV or quiescent counterparts at their mass and have lower $M_{\text{H}_2}/M_\rm{H\,{\small I}}$. The above data suggest two pathways for quenching low-mass galaxies, $M_\ast \le {}M_c$: a fast one that changes the morphology on the SFMS and a slow one that does not. Above $M_c$, galaxies below the SFMS resemble GV and quiescent galaxies structurally, implying that they undergo a structural transformation already within the SFMS. For these massive galaxies, CG are strongly bimodal, with SFMS galaxies exhibiting negative colour gradients, suggesting most star formation occurs in their outskirts, maintaining them within the SFMS.

Stochastic prior for non-parametric star-formation histories

ABSTRACT The amount of power contained in the variations in galaxy star-formation histories (SFHs) across a range of time-scales encodes key information about the physical processes which modulate star formation. Modelling the SFHs of galaxies as stochastic processes allows the relative importance of different time-scales to be quantified via the power spectral density (PSD). In this paper, we build upon the PSD framework and develop a physically motivated, ‘stochastic’ prior for non-parametric SFHs in the spectral energy distribution (SED)-modelling code prospector. We test this prior in two different regimes: (1) massive, $z = 0.7$ galaxies with both photometry and spectra, analogous to those observed with the LEGA-C survey, and (2) $z = 8$ galaxies with photometry only, analogous to those observed with NIRCam on JWST. We find that it is able to recover key galaxy parameters (e.g. stellar mass, stellar metallicity) to the same level of fidelity as the commonly used continuity prior. Furthermore, the realistic variability information incorporated by the stochastic SFH model allows it to fit the SFHs of galaxies more accurately and precisely than traditional non-parametric models. In fact, the stochastic prior is $\gtrsim 2\times$ more accurate than the continuity prior in measuring the recent star-formation rates (log SFR$_{100}$ and log SFR$_{10}$) of both the $z = 0.7$ and $z = 8$ mock systems. While the PSD parameters of individual galaxies are difficult to constrain, the stochastic prior implementation presented in this work allows for the development of hierarchical models in the future, i.e. simultaneous SED-modelling of an ensemble of galaxies to measure their underlying PSD.

Bulge+disc decomposition of HFF and CANDELS galaxies: UVJ diagrams and stellar mass–size relations of galaxy components at 0.2 ≤ z ≤ 1.5

ABSTRACT Using deep imaging from the CANDELS and HFF surveys, we present bulge+disc decompositions with galfitm for $\sim$17 000 galaxies over $0.2 \le z\le 1.5$. We use various model parameters to select reliable samples of discs and bulges, and derive their stellar masses using an empirically calibrated relation between mass-to-light ratio and colour. Across our entire redshift range, we show that discs follow stellar mass–size relations that are consistent with those of star-forming galaxies, suggesting that discs primarily evolve via star formation. In contrast, the stellar mass–size relations of bulges are mass-independent. Our novel data set further enables us to separate components into star-forming and quiescent based on their specific star formation rates. We find that both star-forming discs and star-forming bulges lie on stellar mass–size relations that are similar to those of star-forming galaxies, while quiescent discs are typically smaller than star-forming discs and lie on steeper relations, implying distinct evolutionary mechanisms. Similar to quiescent galaxies, quiescent bulges show a flattening in the stellar mass–size relation at $\sim 10^{10}$ M$_\odot$, below which they show little mass dependence. However, their best-fitting relations have lower normalizations, indicating that at a given mass, bulges are smaller than quiescent galaxies. Finally, we obtain rest-frame colours for individual components, showing that bulges typically have redder colours than discs, as expected. We visually derive UVJ criteria to separate star-forming and quiescent components and show that this separation agrees well with component colour. HFF bulge+disc decomposition catalogues used for these analyses are publicly released with this paper.

Detailed study of a rare hyperluminous rotating disk in an Einstein ring 10 billion years ago

Hyperluminous infrared galaxies (HyLIRGs) are the rarest and most extreme starbursts and found only in the distant Universe (z ≳ 1). They have intrinsic infrared (IR) luminosities LIR ≥ 1013 L⊙ and are commonly found to be major mergers. Recently, the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts project (PASSAGES) searched ~104 deg2 of the sky and found ~20 HyLIRGs. We describe a detailed study of PJ0116-24, the brightest (μLIR ≈ 2.6 × 1014 L⊙, magnified with μ ≈ 17) Einstein-ring HyLIRG in the southern sky, at z = 2.125, with observations from the near-IR integral-field spectrograph VLT/ERIS and the submillimetre interferometer ALMA. We detected Hα, Hβ, [N ii] and [S ii] lines and obtained an extreme Balmer decrement (Hα/Hβ ≈ 8.73 ± 1.14). We modelled the molecular-gas and ionized-gas kinematics with CO(3–2) and Hα data at ~100–300 pc and (sub)kiloparsec delensed scales, respectively, finding consistent regular rotation. We found PJ0116-24 to be highly rotationally supported (vrot/σ0, mol. gas ≈ 9.4) with a richer gaseous substructure than other known HyLIRGs. Our results imply that PJ0116-24 is an intrinsically massive (Mbaryon ≈ 1011.3 M⊙) and rare starbursty disk (star-formation rate, SFR = 1,490 M⊙ yr−1) probably undergoing secular evolution. This indicates that the maximal SFR (≳1,000 M⊙ yr−1) predicted by simulations could occur during a galaxy’s secular evolution, away from major mergers.

The baryon cycle in modern cosmological hydrodynamical simulations

ABSTRACT In recent years, cosmological hydrodynamical simulations have proven their utility as key interpretative tools in the study of galaxy formation and evolution. In this work, we present a comparative analysis of the baryon cycle in three publicly available, leading cosmological simulation suites: EAGLE, IllustrisTNG, and SIMBA. While these simulations broadly agree in terms of their predictions for the stellar mass content and star formation rates of galaxies at $z\approx 0$, they achieve this result for markedly different reasons. In EAGLE and SIMBA, we demonstrate that at low halo masses ($M_{\rm 200c}\lesssim 10^{11.5}\, \mathrm{M}_{\odot }$), stellar feedback (SF)-driven outflows can reach far beyond the scale of the halo, extending up to $2\!-\!3\times R_{\rm 200c}$. In contrast, in TNG, SF-driven outflows, while stronger at the scale of the interstellar medium, recycle within the circumgalactic medium (within $R_{\rm 200c}$). We find that active galactic nucleus (AGN)-driven outflows in SIMBA are notably potent, reaching several times $R_{\rm 200c}$ even at halo masses up to $M_{\rm 200c}\approx 10^{13.5}\, \mathrm{M}_{\odot }$. In both TNG and EAGLE, AGN feedback can eject gas beyond $R_{\rm 200c}$ at this mass scale, but seldom beyond $2\!-\!3\times R_{\rm 200c}$. We find that the scale of feedback-driven outflows can be directly linked with the prevention of cosmological inflow, as well as the total baryon fraction of haloes within $R_{\rm 200c}$. This work lays the foundation to develop targeted observational tests that can discriminate between feedback scenarios, and inform subgrid feedback models in the next generation of simulations.

Little Red Dots from Low-spin Galaxies at High Redshifts

Recently, a new population of compact, high-redshift (z ≳ 7) galaxies appeared as little red dots (LRDs) in deep JWST observations. The latest spectroscopic data indicates that these galaxies contain an evolved stellar population, reflecting an early episode of high star formation-rate. The appearance of broad emission lines suggests that a central overmassive black hole also powers these galaxies. I propose that LRD galaxies represent the low-spin tail of the galaxy population. Low-spin galaxies host a more compact gaseous disk with an enhanced star formation rate relative to typical galaxies at the same redshift. The compact disk feeds efficiently a central black hole, as predicted by Eisenstein & Loeb.

Entrainment of hot gas into cold streams: the origin of excessive star formation rates at cosmic noon

ABSTRACT We explore the evolution of cold streams from the cosmic web that feed galaxies through their shock-heated circumgalactic medium (CGM) at cosmic noon, $z\simeq 1-5$. In addition to the hydrodynamical instabilities and radiative cooling that we have incorporated in earlier works, we embed the stream and the hot CGM in the gravitational potential of the host dark matter halo, deriving equilibrium profiles for both. Self-gravity within the stream is tentatively ignored. We find that the cold streams gradually entrain a large mass of initially hot CGM gas that cools in the mixing layer and condenses onto the stream. This entrainment, combined with the acceleration down the gravitational potential well, typically triples the inward cold inflow rate into the central galaxy, compared to the original rate at the virial radius, which makes the entrained gas the dominant source of gas supply to the galaxy. The potential sources for the hot gas to be entrained are recycled enriched gas that has been previously ejected from the galaxy, and fresh virial-shock-heated gas that has accumulated in the CGM. This can naturally elevate the star formation rate in the galaxy by a factor of $\sim 3$ compared to the gas accretion rate onto the halo, thus explaining the otherwise puzzling observed excess of star formation at cosmic noon. When accounting for self-shielding of dense gas from the ultraviolet background, we find that the energy radiated from the streams, originating predominantly from the cooling of the entrained gas, is consistent with observed Lyman-$\alpha$ blobs around galaxies.

Mapping the oxygen abundance in Red Geysers and its relation with the gas kinematics using megacubes

ABSTRACT Red Geysers are galaxies with low-star formation rates and galactic scale ionized outflows likely driven by low-luminosity active galactic nuclei (AGN). We investigated the impact of AGN winds on the oxygen abundance using integral field spectroscopic data from Mapping Nearby Galaxies for Red Geysers, control galaxies (quiescent galaxies without outflows), and AGN hosts within the inner 1.5 kpc radius. Red Geyser galaxies have higher W$_{80}$ values compared to those of AGN and controls, with 64 per cent showing W$_{80}\gt 500$ km s$^{-1}$ that is indicative of outflow. Only 40 per cent of controls and 31 per cent of AGNs reach this value. We found a small tendency of the oxygen abundance distribution of controls to be biased towards higher values than those of Red Geysers. However, Red Geysers do not show a correlation between H$\alpha$ width (parametrized by the W$_{\rm 80}$) and oxygen abundance, which indicates that AGN winds are not significantly impacting the chemical abundance of the nuclear region of these galaxies. The oxygen abundance distribution mean value for the tree samples is $\rm 12+log(O/H)\sim$8.7 ($\mathit{Z}\sim \rm Z_{\odot })$. On the other hand, AGN hosts show a positive correlation between W$_{80}$ and O/H which could be due to star formation that outflows from the active nuclei could induce; or to the reservoir of gas that makes the nucleus active, and its is also used in the star formation.

Correlations between IR Luminosity, Star Formation Rate, and CO Luminosity in the Local Universe

We exploit the DustPedia sample of galaxies within approximately 40 Mpc, selecting 388 sources, to investigate the correlations between IR luminosity (LIR), the star formation rate (SFR), and the CO(1-0) luminosity (LCO) down to much lower luminosities than reached by previous analyses. We find a sub-linear dependence of the SFR on LIR. Below log(LIR/L⊙)≃10 or SFR≃1M⊙yr−1, the SFR/LIR ratio substantially exceeds the standard ratio for dust-enshrouded star formation, and the difference increases with decreasing LIR values. This implies that the effect of unobscured star formation overcomes that of dust heating by old stars, at variance with results based on the Planck ERCSC galaxy sample. We also find that the relations between the LCO and LIR or the SFR are consistent with those obtained at much higher luminosities.

Constraints on short gamma-ray burst physics and their host galaxies from systematic radio follow-up campaigns

ABSTRACT Short gamma-ray bursts (GRBs) are explosive transients caused by binary mergers of compact objects containing at least one neutron star. Multiwavelength afterglow observations provide constraints on the physical parameters of the jet, its surrounding medium, and the microphysics of the enhanced magnetic fields and accelerated electrons in the blast wave at the front of the jet. The synchrotron radio emission can be tracked for much longer than in other spectral regimes, and it can pin down the evolution of the spectral peak. We present the results of a systematic observing campaign of eight short GRBs with the MeerKAT radio telescope. Additionally, we present observations of four of these short GRBs using the ATCA radio telescope and two of these short GRBs with the e-MERLIN radio telescope. Using these results we report one possible detection of a short GRB afterglow from GRB 230217A and deep upper limits for the rest of our short GRB observations. We use these observations to place constraints on some of the physical parameters, in particular those related to electron acceleration, the circumburst density, and gamma-ray energy efficiency. We discuss how deeper observations with new and upgraded telescopes should be able to determine if the gamma-ray efficiency differs between long and short GRBs. We also report detections of the likely host galaxies for four of the eight GRBs and upper limits for another GRB, increasing the number of detected host galaxies in the radio with implications for the star formation rate in these galaxies.