Star Formation Rates Of Galaxies Research Articles

EPOCHS Paper V. The dependence of galaxy formation on galaxy structure at z < 7 from JWST observations

Abstract We measure the broad impact of galaxy structure on galaxy formation by examining the ongoing star formation and integrated star formation history as revealed through the stellar masses of galaxies at z < 7 based on JWST CEERS data from the Extended Groth Strip (EGS). Using the morphological catalog of 3965 visually classified JWST galaxies from Ferreira et al. (2023), we investigate the evolution of stars, and when they form, as a function of morphological type as well as galaxies classified as passive and starburst through spectral energy distributions. Although disk galaxies dominate the structures of galaxies at z < 7, we find that these disks are in general either ‘passive’, or on the main-sequence of star formation, and do not contain a large population of starburst galaxies. We also find no significant correlation between morphological type and the star formation rate or colours of galaxies at z < 7. In fact, we find that the morphologically classified ‘spheroids’ tend to be blue and are not found to be predominately passive systems at z > 1.5. We also find that the stellar mass function for disk galaxies does not evolve significantly during this time, whereas other galaxy types, such as the peculiar population, evolve dramatically, declining at lower redshifts. This indicates that massive peculiars are more common at higher redshifts. We further find that up to z ∼ 7, the specific star formation rate (sSFR) does not vary with visual morphology, but strongly depends on stellar mass and internal galaxy mass density. This demonstrates that at early epochs galaxy assembly is a mass-driven, rather than a morphologically-driven, process. Quenching of star formation is therefore a mass-dominated process throughout the universe’s history, likely due to the presence of supermassive black holes.

DEVILS/MIGHTEE/GAMA/DINGO: the impact of SFR time-scales on the SFR-radio luminosity correlation

ABSTRACT The tight relationship between infrared luminosity (LTIR) and 1.4 GHz radio continuum luminosity ($L_\mathrm{1.4\, GHz}$) has proven useful for understanding star formation free from dust obscuration. Infrared emission in star-forming galaxies typically arises from recently formed, dust-enshrouded stars, whereas radio synchrotron emission is expected from subsequent supernovae. By leveraging the wealth of ancillary far-ultraviolet – far-infrared photometry from the Deep Extragalactic VIsible Legacy Survey and Galaxy and Mass Assembly surveys, combined with 1.4 GHz observations from the Meer Karoo Array Telescope International GHz Tiered Extragalactic Exploration survey and Deep Investigation of Neutral Gas Origin projects, we investigate the impact of time-scale differences between far-ultraviolet – far-infrared and radio-derived star formation rate (SFR) tracers. We examine how the spectral energy distribution (SED)-derived star formation histories (SFHs) of galaxies can be used to explain discrepancies in these SFR tracers, which are sensitive to different time-scales. Galaxies exhibiting an increasing SFH have systematically higher LTIR and SED-derived SFRs than predicted from their 1.4 GHz radio luminosity. This indicates that insufficient time has passed for subsequent supernovae-driven radio emission to accumulate. We show that backtracking the SFR(t) of galaxies along their SED-derived SFHs to a time several hundred megayears prior to their observed epoch will both linearize the SFR–$L_\mathrm{1.4\, GHz}$ relation and reduce the overall scatter. The minimum scatter in the SFR(t)–$L_\mathrm{1.4\, GHz}$ is reached at 200 – 300 Myr prior, consistent with theoretical predictions for the time-scales required to disperse the cosmic ray electrons responsible for the synchrotron emission.

Exploring bar fractions: a comparative study of galaxy pairs and single galaxies

We present a comprehensive analysis of barred galaxies within two distinct samples: isolated single galaxies (SIG) and isolated galaxy pairs (SIP), drawn from the SDSS-based catalog of isolated galaxies and the catalog of isolated galaxy pair limited to M ≤ −18.5, respectively. Our primary aim is to investigate the influence of tidal effects on the bar fraction (f bar ) across various galaxy systems. Barred galaxies are identified through automated ellipse fitting analysis supplemented by visual inspection of r-band imaging. A strong correlation between f bar and both galaxy morphological type and star formation rate has been revealed. Although, barred galaxies represent a nearly equal percentage of 52% in SIG and 51% in SIP, we found a little evidence for the tidal dependence of bar formation where a notable increase in the f bar is observed among galaxies characterized by larger projected separation and higher radial velocity difference between the pair members. In SIGs, we observe a prevalent increasing trend of f bar with galaxy mass, contrasting the observed decrease in f bar with increasing galaxy mass in SIPs. This discrepancy is consistent with typical trends of weaker bars, suggesting that tidal effect may attenuate the strength of bar structures within galaxy pairs.

Radio properties of green pea galaxies

Green peas (GPs) are young, compact, star-forming dwarf galaxies, and local (\(z analogues of the early galaxies (\(z 6\)) considered to be mainly responsible for the reionisation of the Universe. Recent X-ray observations of GPs led to the detection of high excess emission, which cannot be accounted for by star formation alone and implies the presence of an active galactic nucleus (AGN). We employ radio observations to study the radio properties of GPs, build their radio spectral energy distributions, and verify the presence of AGNs. We performed new radio observations of three GPs with the Karl G. Jansky Very Large Array (JVLA) in the L, C, and X bands (1.4, 6 and 10 GHz resp.) and analysed them alongside data from archival observations and large radio surveys. We also analysed the archival radio data for a larger sample of GPs and blueberry (BBs) galaxies, which are lower-mass and lower-redshift analogues of the GPs. To understand the significance of the radio observations, we assess the detectability of these sources, and compare the detected radio luminosities with expectations from theoretical and empirical relations. Two of the three targeted GPs are strongly detected (\(>10 in the JVLA observations and their fluxes are consistent with star formation, while the third source is undetected. Although archival radio surveys have the sensitivity to detect a large fraction (\( 75<!PCT!>\)) of the sources from the larger archival sample of GPs and BBs we only detect a small number (\(< 40<!PCT!>\)) of them and their radio luminosity is significantly lower than the expectation from empirical relations. Our results show that the majority of the dwarf galax ies in our sample are highly underluminous. The radio luminosity star formation rate (SFR) relation deviates from the empirical relations, especially towards the lower end of galaxy mass and SFR, suggesting that the relations established for larger galaxies may not hold towards the low-mass end.

SAGAbg. I. A Near-unity Mass-loading Factor in Low-mass Galaxies via Their Low-redshift Evolution in Stellar Mass, Oxygen Abundance, and Star Formation Rate

Measuring the relation between star formation and galactic winds is observationally difficult. In this work we make an indirect measurement of the mass-loading factor (the ratio between the mass outflow rate and star formation rate) in low-mass galaxies using a differential approach to modeling the low-redshift evolution of the star-forming main sequence and mass–metallicity relation. We use Satellites Around Galactic Analogs (SAGA) background galaxies, i.e., spectra observed by the SAGA Survey that are not associated with the main SAGA host galaxies, to construct a sample of 11,925 spectroscopically confirmed low-mass galaxies from 0.01 ≲ z ≤ 0.21 and measure auroral line metallicities for 120 galaxies. The crux of the method is to use the lowest-redshift galaxies as the boundary condition of our model, and to infer a mass-loading factor for the sample by comparing the expected evolution of the low-redshift reference sample in stellar mass, gas-phase metallicity, and star formation rate against the observed properties of the sample at higher redshift. We infer a mass-loading factor of ηm=0.92−0.74+1.76 , which is in line with direct measurements of the mass-loading factor from the literature despite the drastically different sets of assumptions needed for each approach. While our estimate of the mass-loading factor is in good agreement with recent galaxy simulations that focus on resolving the dynamics of the interstellar medium, it is smaller by over an order of magnitude than the mass-loading factor produced by many contemporary cosmological simulations.

The α-element enrichment of gas in distant galaxies

Context. The chemical evolution of distant galaxies cannot be assessed from observations of individual stars, in contrast to the case of nearby galaxies. On the other hand, the study of the interstellar medium (ISM) offers an alternative way to reveal important properties of the chemical evolution of distant galaxies. The chemical enrichment of the ISM is produced by all the previous generations of stars and it is possible to precisely determine the metal abundances in the neutral ISM in galaxies. The chemical abundance patterns in the neutral ISM are determined by the gas metallicity, presence of dust (the depletion of metals into dust grains), and possible deviations due to specific nucleosynthesis, for example, α-element enhancements. Aims. We aim to derive the metallicities, dust depletion, and α-element enhancements in the neutral ISM of gas-rich mostly-metal-poor distant galaxies (Damped Lyman-α absorbers, DLAs). Furthermore, we aim to constrain the distribution of α-element enhancements with metallicity in these galaxies. Methods. We collected a literature sample of column density measurements of O, Mg, Si, S, Ti, Cr, Fe, Ni, Zn, P, and Mn in the neutral ISM of DLAs at redshifts of 0.60 < z < 3.40. We used this sample to define a golden sample of DLAs with constrained observations of Ti and at least one other α-element. By studying the abundance patterns, we determined the amount of dust depletion, solely based on the observed relative abundances of the α-elements. We then used the abundances of Fe-peak elements to determine the overall metallicity of each system, after correcting for dust depletion. In addition, we studied the deviations from the basic (linear) abundance patterns. We divided our sample into two groups of galaxies based on the widths of their absorption lines (Δv90 above or below 100 km s−1), which may be considered as a proxy for their dynamical mass. We characterised the distribution of the α-element enhancements as a function of metallicity for the galaxy population as a whole, by fitting a piecewise function (plateau, decline, plateau) to the data. Results. We observed systematic deviations from the basic abundance patterns for O, Mg, Si, S, Ti, and Mn, which we interpreted as α-element enhancements and a Mn underabundance. The distribution of the α-element enhancements with metallicity is different in the high-Δv90 and low-Δv90 groups of galaxies. We constrained the metallicity of the α-element knee for the high-Δv90 and low-Δv90 groups of galaxies to be −1.02±0.15 dex and −1.84±0.11 dex, respectively. The average α-element enhancement at the high-plateau is [α/Fe]=0.38±0.07 dex. On the other hand, Mn shows an underabundance in all DLAs in the golden sample of −0.36±0.07 dex, on average. Conclusions. We have constrained, for the first time, the distribution of the α-element enhancement with metallicity in the neutral ISM in distant galaxies. Less massive galaxies show an α-element knee at lower metallicities than more massive galaxies. This can be explained by a lower star formation rate in less massive galaxies. If this collective behaviour can be interpreted in the same way as it is for individual systems, this would suggest that more massive and metal-rich systems evolve to higher metallicities before the contribution of SN-Ia to [α/Fe] levels out that of core-collapse SNe. This finding may plausibly be supported by different SFRs in galaxies of different masses. Overall, our results offer important clues to the study of chemical evolution in distant galaxies.

Unveiling very young O stars

Context. O-type stars are known to significantly contribute to both the dynamics and evolution of galaxies. Massive and luminous, they probably control and regulate the galaxies star formation rates. The stellar feedback generated by such cosmic beasts can strongly affect the local star formation rate, with effects in the current (and future) generations of low and intermediate mass stars, and possibly also in the disruption process of the galaxies’ giant gas reservoirs. Aims. For this work I performed a redetermination of the spectral types and effective temperatures of the Galactic O-type stars MSP182, MSP183, MSP199, VPHAS-01338, and VPHAS-01273. Methods. From a careful examination of the spectral features present in the blue optical spectral region, it was possible to identify several nitrogen lines usually only seen in the blue optical spectra of O2–O3 stars. From the nitrogen ionic equivalent width ratios measured in the spectra of MSP182, MSP183, MSP199, VPHAS-01338, and VPHAS-01273, and in those of standard stars of the O2–O4 spectral types, earlier spectral types and hotter effective temperature values were derived. Results. Two O2V((f*))z, together with three new O3 V stars are now firmly identified in the Westerlund 2 region. Besides RFS1 in NGC 3603, the O2 V stars found in Westerlund 2 are the only other exemplars known to date in the Milky Way. From the nitrogen equivalent width line ratios measured in the spectra of standard stars of the O2–O4 spectral types, linear relations between the N IVλ4058/N IIIλ4640 ratio and the effective temperature in the 47 000–51 000 K range were derived. Based on my spectroscopic analysis of the science targets and the use of a HRD, a mean heliocentric distance of 5 kpc to Westerlund 2 was computed, a result that is in line with the mean heliocentric distance of 5.3 ± 1.5 kpc obtained from the associated Gaia DR3 parallaxes and distances. Conclusions. The Westerlund 2 massive stars studied in this work probably share a common evolutionary process that might be representative of the evolutionary ages of a large fraction of the cluster’s O-type stellar population, which seems to be much younger than 1 Myr.

The MAGPI survey: evolution of radial trends in star formation activity across cosmic time

ABSTRACT Using adaptive optics with the Multi-Unit Spectroscopic Explorer on the Very Large Telescope, the Middle Ages Galaxy Properties with Integral Field Spectroscopy survey allows us to study the spatially resolved Universe at a crucial time of ∼4 Gyr ago (z ∼ 0.3) when simulations predict the greatest diversity in evolutionary pathways for galaxies. We investigate the radial trends in the star formation (SF) activity and luminosity-weighted stellar ages as a function of offset from the star-forming main sequence (SFMS) for a total of 294 galaxies. Using both Hα emission and the 4000 Å break (i.e. D4000) as star formation rate (SFR) tracers, we find overall flat radial profiles for galaxies lying on and above the SFMS, suggestive of physical processes that enhance/regulate SF throughout the entire galaxy disc. However, for galaxies lying below the SFMS, we find positive gradients in SF suggestive of inside–out quenching. Placing our results in context with results from other redshift regimes suggests an evolution in radial trends at z ∼ 0.3 for SF galaxies above the SFMS, from uniformly enhanced SF at z ∼ 1 and ∼ 0.3 to centrally enhanced SF at z ∼ 0 (when averaged over a wide range of mass). We also capture higher local SFRs for galaxies below the SFMS compared to that of z ∼ 0, which can be explained by a larger population of quenched satellites in the local Universe and/or different treatments of limitations set by the D4000–sSFR relation.

Probing star formation rates and histories in AGNs and non-AGN galaxies across diverse cosmic environments and X-ray luminosity ranges

In this work, we compare the star formation rates (SFRs) and star formation histories (SFHs) of active galactic nuclei (AGNs) and non-AGN galaxies. We explore these aspects across different density fields and over three orders of magnitude in X-ray luminosity (L$_X$). For that purpose, we employed X-ray AGNs detected in the XMM-XXL field and constructed a galaxy control sample, using sources from the VIPERS catalogue. We applied strict photometric and quality selection criteria to ensure that only sources with robust (host) galaxy measurements were included in the analysis. Our final samples consist of 149 X-ray AGNs with $ L_ X,2-10keV (ergs^ <45$ and 3\,488 non-AGN systems. The sources span a redshift range of $ 0.5<z<1.0$ and have stellar masses within, $10.5< M_*(M_ odot) <11.5$. For these systems, we adopted the available measurements for their local densities and their spectral lines (D$_n$4000) from the VIPERS catalogue. To compare the SFRs of these two populations, we calculated the SFR$_ norm $ parameter. The latter is defined as the ratio of the SFRs of AGNs to the SFRs of non-AGN galaxies with similar M$_*$ and redshift. Our findings reveal that low- and moderate-L$_X$ AGNs ($ L_ X,2-10keV (ergs^ <44$) that reside in low-density fields have a nearly flat SFR$_ norm -$L$_X$ relation. In contrast, the AGNs of similar L$_X$ values that reside in high-density environments present an increase in SFR$_ norm $ with L$_X$. These results are in line with previous studies. Notably, our results suggest that the most luminous of the AGNs ($ L_ X,2-10keV (ergs^ >44$) exhibit an increased SFR in comparison to non-AGN galaxies. This trend appears to be independent of the density of the environment. Furthermore, for AGNs with similar L$_X$, those in high-density regions tend to have higher SFR$_ norm $ values compared to their counterparts in low-density areas. Comparisons of the D$_n$4000 spectral index, which serves as a proxy for the age of the stellar population, reveals that low- and moderate-L$_X$ AGNs reside in galaxies with comparable stellar populations with non-AGN systems, regardless of the density field they are situated in. However, the most luminous X-ray sources tend to reside in galaxies that have younger stellar populations, as compared to non-AGN galaxies, regardless of the galaxy's environment.

The Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey

We present the Next Generation Deep Extragalactic Exploratory Public (NGDEEP) Survey, a deep slitless spectroscopic and imaging Cycle 1 JWST treasury survey designed to constrain feedback mechanisms in low-mass galaxies across cosmic time. NGDEEP targets the Hubble Ultra Deep Field (HUDF) with NIRISS slitless spectroscopy ( flim,line,5σ≈1.2× 10−18 erg s−1 cm−2) to measure metallicities and star formation rates (SFRs) for low-mass galaxies through the peak of the cosmic SFR density (0.5 < z < 4). In parallel, NGDEEP targets the HUDF-Par2 parallel field with NIRCam ( mlim,5σ=30.6−30.9 ) to discover galaxies to z > 12, constraining the slope of the faint end of the rest-ultraviolet luminosity function. NGDEEP overlaps with the deepest HST Advanced Camera for Surveys optical imaging in the sky, F435W in the HUDF ( mlim,F435W=29.6 ) and F814W in HUDF-Par2 ( mlim,F814W=30 ), making this a premier HST+JWST deep field. As a treasury survey, NGDEEP data are public immediately, and we will rapidly release data products and catalogs in the spirit of previous deep-field initiatives. In this paper we present the NGDEEP survey design, summarize the science goals, and detail plans for the public release of NGDEEP reduced data products.

Attenuation proxy hidden in surface brightness – colour diagrams

Aims. Large future sky surveys, such as the Legacy Survey of Space and Time (LSST), will provide optical photometry for billions of objects. Reliable estimation of the physical properties of galaxies requires information about dust attenuation, which is usually derived from ultraviolet (UV) and infrared (IR) data. This paper aims to construct a proxy for the far-UV (FUV) attenuation (AFUVp) from the optical data alone, enabling the rapid estimation of the star formation rate (SFR) for galaxies that lack UV or IR data. This will accelerate and improve the estimation of key physical properties of billions of LSST–like observed galaxies (observed in the optical bands only). Methods. To mimic LSST observations, we used the deep panchromatic optical coverage of the Sloan Digital Sky Survey (SDSS) Photometric Catalogue, Data Release 12, complemented by the estimated physical properties for the SDSS galaxies from the GALEX-SDSS-WISE Legacy Catalog (GSWLC) and inclination information obtained from the SDSS Data Release 7. We restricted our sample to the 0.025–0.1 spectroscopic redshift range and investigated relations among surface brightness, colours, and dust attenuation in the FUV range for star-forming galaxies obtained from the spectral energy distribution (SED). Results. Dust attenuation is best correlated with colour measured between u and r bands (u − r) and the surface brightness in the u band (μu). We provide a dust attenuation proxy for galaxies on the star-forming main sequence. This relation can be used for the LSST or any other type of broadband optical survey. The mean ratio between the catalogue values of SFRs and those estimated using optical-only SDSS data with the AFUVp prior calculated as ΔSFR = log(SFRthis work/SFRGSWLC) is found to be less than 0.1 dex, while runs without priors result in an SFR overestimation larger than 0.3 dex. The presence or absence of the AFUVp has a negligible influence on the stellar mass (Mstar) estimation (with ΔMstar in the range from 0 to −0.15 dex). Conclusions. We note that AFUVp is reliable for low-redshift main sequence galaxies. Forthcoming deep optical observations of the LSST Deep Drilling Fields, which also have multi-wavelength data, will enable one to calibrate the obtained relation for higher redshift galaxies and, possibly, extend the study towards other types of galaxies, such as early-type galaxies off the main sequence.

Insights into Galaxy Morphology and Star Formation: Unveiling Filamentary Structures around an Extreme Overdensity at z ∼ 1.5 Traced by [O ii] Emitters

We explore the morphological features and star formation activities of [O ii] emitters in the COSMOS UltraDeep field at z ∼ 1.5 using JWST NIRCam data from the COSMOS-Web survey and Subaru Hyper Suprime-Cam. We also report the discovery of large filamentary structures traced by [O ii] emitters surrounding an extremely overdense core with a galaxy number density ∼11× higher than the field average. These structures span over 50 cMpc, underscoring their large scale in the cosmic web at this epoch. After matching the stellar-mass distributions, the core galaxies show a higher frequency of disturbances (50% ± 9%) than those in the outskirts (41% ± 9%) and the field (21% ± 5%), indicative of more frequent mergers and interactions in the innermost ≲1.′5 region. Additionally, we observe that specific star formation rates are elevated in denser environments. A Kolmogorov–Smirnov test comparing the distribution of specific star formation rates of core and field galaxies yields a p-value of 0.02, suggesting an enhancement of star formation activity driven by the dense environment. Our findings underscore the environmental impact on galaxy evolution during a pivotal cosmic epoch and set the stage for further investigation with the increasing larger data from upcoming surveys.

The mass–metallicity and fundamental metallicity relations in non-AGN and AGN-host galaxies

ABSTRACT Galaxies’ stellar masses, gas-phase oxygen abundances (metallicity), and star formation rates (SFRs) obey a series of empirical correlations, most notably the mass–metallicity relation (MZR) and fundamental metallicity relation (FZR), which relates oxygen abundance to a combination of stellar mass and SFR. However, due to the difficulty of measuring oxygen abundances and SFRs in galaxies that host powerful active galactic nuclei (AGN), to date it is unknown to what extent AGN-host galaxies also follow these correlations. In this work, we apply Bayesian methods to the MaNGA integral field spectrographic (IFS) survey that allow us to measure oxygen abundances and SFRs in AGN hosts, and use these measurements to explore how the MZR and FZR differ between galaxies that do and do not host AGN. We find similar MZRs at stellar masses above $10^{10.5} \, \mathrm{M}_\odot$, but that at lower stellar masses AGN hosts show up to $\sim 0.2$ dex higher oxygen abundances. The offset in the FZR is significantly smaller, suggesting that the larger deviation in the MZR is a result of AGN-host galaxies having systematically lower SFRs at fixed stellar mass. However, within the AGN-host sample there is little correlation between SFR and oxygen abundance. These findings support a scenario in which an AGN can halt efficient gas accretion, which drives non-AGN host galaxies to both higher SFR and lower oxygen abundance, resulting in the galaxy evolving off the star-forming main sequence (SFMS). As a consequence, as the SFR declines for an individual system its metallicity remains mostly unchanged.

Beware the recent past: a bias in spectral energy distribution modelling due to bursty star formation

ABSTRACT We investigate how the recovery of galaxy star formation rates (SFRs) using energy-balance spectral energy distribution (SED) fitting codes depends on their recent star formation histories (SFHs). We use the magphys and prospector codes to fit 6706 synthetic SEDs of simulated massive galaxies at 1 &amp;lt; z &amp;lt; 8 from the Feedback in Realistic Environments project. We identify a previously unknown systematic error in the magphys results due to bursty star formation: the derived SFRs can differ from the truth by as much as 1 dex, at large statistical significance (&amp;gt;5σ), depending on the details of their recent SFH. SFRs inferred using prospector with non-parametric SFHs do not exhibit this trend. We show that using parametric SFHs (pSFHs) causes SFR uncertainties to be underestimated by a factor of up to 5×. Although this undoubtedly contributes to the significance of the systematic, it cannot explain the largest biases in the SFRs of the starbursting galaxies, which could be caused by details of the stochastic prior sampling or the burst implementation in the magphys libraries. We advise against using pSFHs and urge careful consideration of starbursts when SED modelling galaxies where the SFR may have changed significantly over the last ∼100 Myr, such as recently quenched galaxies, or those experiencing a burst. This concern is especially relevant, e.g. when fitting JWST observations of very high redshift galaxies.

CLusters in the Uv as EngineS (CLUES). II. Subkiloparsec-scale Outflows Driven by Stellar Feedback

We analyze the far-ultraviolet (1130−1770 Å rest frame) spectroscopy of 20 young (<50 Myr) and massive (>104 M ⊙) star clusters (YSCs) in 11 nearby star-forming galaxies. We probe the interstellar gas intervening along the line of sight, detecting several metal absorption lines of a wide range of ionization potentials, from 6.0 to 77.5 eV. Multiple-component Voigt fits to the absorption lines are used to study the kinematics of the gas. We find that nearly all targets in the sample feature gas outflowing from 30 up to 190 km s−1, often in both the neutral and ionized phases. The outflow velocities correlate with the underlying stellar population properties directly linked to the feedback: the mass of the YSCs, the photon production rate, and the instantaneous mechanical luminosity produced by stellar winds and supernovae. We detect a neutral inflow in four targets, which we interpret as likely not associated with the star cluster but tracing larger-scale gas kinematics. A comparison between the outflows’ energy and that produced by the associated young stellar populations suggests an average coupling efficiency of 10% with a broad scatter. Our results extend the relation found in previous works between galactic outflows and the host galaxy star formation rate to smaller scales, pointing toward the key role that clustered star formation and feedback play in regulating galaxy growth.

Interplay of stellar and gas-phase metallicities: unveiling insights for stellar feedback modelling with Illustris, IllustrisTNG, and EAGLE

ABSTRACT The metal content of galaxies provides a window into their formation in the full context of the cosmic baryon cycle. In this study, we examine the relationship between stellar mass and stellar metallicity (MZ*R) in the hydrodynamic simulations Illustris, TNG, and EAGLE (Evolution and Assembly of GaLaxies and their Environment) to understand the global properties of stellar metallicities within the feedback paradigm employed by these simulations. Interestingly, we observe significant variations in the overall normalization and redshift evolution of the MZ*R across the three simulations. However, all simulations consistently demonstrate a tertiary dependence on the specific star formation rate (sSFR) of galaxies. This finding parallels the relationship seen in both simulations and observations between stellar mass, gas-phase metallicity, and some proxy of galaxy gas content (e.g. SFR, gas fraction, and atomic gas mass). Since we find this correlation exists in all three simulations, each employing a subgrid treatment of the dense, star-forming interstellar medium (ISM) to simulate smooth stellar feedback, we interpret this result as a fairly general feature of simulations of this kind. Furthermore, with a toy analytic model, we propose that the tertiary correlation in the stellar component is sensitive to the extent of the ‘burstiness’ of feedback within galaxies.

Comparative analysis of the SFR of AGN and non-AGN galaxies, as a function of stellar mass, AGN power, cosmic time, and obscuration

This study involves a comparative analysis of the star formation rates (SFRs) of active galactic nucleus (AGN) galaxies and non-AGN galaxies and of the SFRs of type 1 and 2 AGNs. To carry out this investigation, we assembled a dataset consisting of 2677 X-ray AGNs detected by the XMM-Newton observatory and a control sample of 64 556 galaxies devoid of AGNs. We generated spectral energy distributions (SEDs) for these objects using photometric data from the DES, VHS, and AllWISE surveys, and we harnessed the CIGALE code to extract measurements for the (host) galaxy properties. Our dataset encompasses a diverse parameter space, with objects spanning a range of stellar masses from 9.5 &lt; log [M*(M⊙)] &lt; 12.0, intrinsic X-ray luminosities within 42 &lt; log[LX,2−10 keV(erg s−1)] &lt; 45.5, and redshifts between 0.3 &lt; z &lt; 2.5. To compare SFRs, we calculated the SFRnorm parameter, which signifies the ratio of the SFR of an AGN galaxy to the SFR of non-AGN galaxies sharing similar M* and redshift. Our analysis reveals that systems hosting an AGN tend to exhibit elevated SFRs compared to non-AGN galaxies, particularly beyond a certain threshold in LX. Notably, this threshold increases as we move toward more massive galaxies. Additionally, for AGN systems with the same LX, the magnitude of the SFRnorm decreases as we consider more massive galaxies. This suggests that in galaxies with an AGN, the increase in SFR as a function of stellar mass is not as prominent as in galaxies without an AGN. This interpretation finds support in the shallower slope that we identify in the X-ray star-forming main sequence in contrast to the galaxy main sequence. Employing CIGALE’s measurements, we classified AGNs into type 1 and type 2. In our investigation, we focused on a subset of 652 type 1 AGNs and 293 type 2 AGNs within the stellar mass range of 10.5 &lt; log[M (M⊙)] &lt; 11.5. Based on our results, type 1 AGNs display higher SFRs than type 2 AGNs, at redshifts below z &lt; 1. However, at higher redshifts, the SFRs of the two AGN populations tend to be similar. At redshifts z &lt; 1, type 1 AGNs show augmented SFRs in comparison to non-AGN galaxies. In contrast, type 2 AGNs exhibit lower SFRs when compared to galaxies that do not host an AGN, at least up to log[LX,2−10 keV(erg s−1)] &lt; 45.

The ALMaQUEST Survey. XII. Dense Molecular Gas as Traced by HCN and HCO+ in Green Valley Galaxies

Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of two dense gas tracers, HCN (1−0) and HCO+ (1-0) for three galaxies in the green valley and two galaxies on the star-forming main sequence with comparable molecular gas fractions as traced by the CO (1−0) emissions, selected from the ALMaQUEST survey. We investigate whether the deficit of molecular gas star formation efficiency (SFEmol) that leads to the low specific star formation rate (sSFR) in these green valley galaxies is due to a lack of dense gas (characterized by the dense gas fraction f dense) or the low star formation efficiency of dense gas (SFEdense). We find that SFEmol as traced by the CO emissions, when considering both star-forming and retired spaxels together, is tightly correlated with SFEdense and depends only weakly on f dense. The sSFR on kiloparsec scales is primarily driven by SFEmol and SFEdense, followed by the dependence on f mol, and is least correlated with f dense or the dense-gas-to-stellar mass ratio (R dense). When compared with other works in the literature, we find that our green valley sample shows lower global SFEmol and lower SFEdense while exhibiting similar dense gas fractions when compared to star-forming and starburst galaxies. We conclude that the star formation of the three green valley galaxies with a normal abundance of molecular gas is suppressed, mainly due to the reduced SFEdense rather than the lack of dense gas.

Environmental dependence of AGN activity and star formation in galaxy clusters from Magneticum simulations

Context. The environment inside and on the outskirts of galaxy clusters has a profound impact on the star formation rate and active galactic nucleus (AGN) activity in cluster galaxies. While the overall star formation and AGN suppression in the inner cluster regions has been thoroughly studied in the past, recent X-ray studies also indicate that conditions on the cluster outskirts may promote AGN activity. Aims. We investigate how the environment and the properties of host galaxies impact the levels of AGN activity and star formation in galaxy clusters. We aim to identify significant trends in different galaxy populations and suggest possible explanations. Methods. We studied galaxies with stellar mass log M*(M⊙) &gt; 10.15 in galaxy clusters with mass M500 &gt; 1013 M⊙ extracted from box2b (640 comoving Mpc h−1) of the Magneticum Pathfinder suite of cosmological hydrodynamical simulations at redshifts 0.25 and 0.90. We examined the influence of stellar mass, distance to the nearest neighbouring galaxy, cluster-centric radius, substructure membership, and large-scale surroundings on the fraction of galaxies hosting an AGN, star formation rate, and the ratio between star-forming and quiescent galaxies. Results. We find that in low-mass galaxies, AGN activity and star formation are similarly affected by the environment and decline towards the cluster centre. In massive galaxies, the impact is different; star-formation level increases in the inner regions and peaks between 0.5 and 1 R500 with a rapid decline in the centre, whereas AGN activity declines in the inner regions and rapidly rises below R500 towards the centre. We suggest that this increase is a result of the larger black hole masses relative to stellar masses in the cluster centre. After disentangling the contributions of neighbouring cluster regions, we find an excess of AGN activity in massive galaxies on the cluster outskirts (∼3 R500). We also find that the local density, substructure membership, and stellar mass strongly influence star formation and AGN activity but verify that they cannot fully account for the observed radial trends.

Cosmic Vine: A z = 3.44 large-scale structure hosting massive quiescent galaxies

We report the discovery of a large-scale structure at z = 3.44 revealed by JWST data in the Extended Groth Strip (EGS) field. This structure, called the Cosmic Vine, consists of 20 galaxies with spectroscopic redshifts at 3.43 &lt; z &lt; 3.45 and six galaxy overdensities (4 − 7σ) with consistent photometric redshifts, making up a vine-like structure extending over a ∼4 × 0.2 pMpc2 area. The two most massive galaxies (M* ≈ 1010.9 M⊙) of the Cosmic Vine are found to be quiescent with bulge-dominated morphologies (B/T &gt; 70%). Comparisons with simulations suggest that the Cosmic Vine would form a cluster with halo mass Mhalo &gt; 1014 M⊙ at z = 0, and the two massive galaxies are likely forming the brightest cluster galaxies (BCGs). The results unambiguously reveal that massive quiescent galaxies can form in growing large-scale structures at z &gt; 3, thus disfavoring the environmental quenching mechanisms that require a virialized cluster core. Instead, as suggested by the interacting and bulge-dominated morphologies, the two galaxies are likely quenched by merger-triggered starburst or active galactic nucleus (AGN) feedback before falling into a cluster core. Moreover, we found that the observed specific star formation rates of massive quiescent galaxies in z &gt; 3 dense environments are one to two orders of magnitude lower than that of the BCGs in the TNG300 simulation. This discrepancy potentially poses a challenge to the models of massive cluster galaxy formation. Future studies comparing a large sample with dedicated cluster simulations are required to solve the problem.