Sequential Star Formation Research Articles

SAGAbg. II. The Low-mass Star-forming Sequence Evolves Significantly between 0.05 < z < 0.21

The redshift-dependent relation between galaxy stellar mass and star formation rate (SFR), known as the star-forming sequence (SFS), is a key observational yardstick for galaxy assembly. We use the SAGAbg-A sample of background galaxies from the Satellites Around Galactic Analogs (SAGA) Survey to model the low-redshift evolution of the low-mass SFS. The sample is comprised of 23,258 galaxies with Hα-based SFRs spanning 6<log10(M⋆/[M⊙])<10 and z < 0.21 (t < 2.5 Gyr). Although it is common to bin or stack galaxies at z ≲ 0.2 for galaxy population studies, the difference in lookback time between z = 0 and z = 0.21 is comparable to the time between z = 1 and z = 2. We develop a model to account for both the physical evolution of low-mass SFS and the selection function of the SAGA Survey, allowing us to disentangle redshift evolution from redshift-dependent selection effects across the SAGAbg-A redshift range. Our findings indicate significant evolution in the SFS over the last ∼2.5 Gyr, with a rising normalization: 〈SFR(M⋆=108.5M⊙)〉(z)=1.24−0.23+0.25z−1.47−0.03+0.03 . We also identify the redshift limit at which a static SFS is ruled out at the 95% confidence level, which is z = 0.05 based on the precision of the SAGAbg-A sample. Comparison with cosmological hydrodynamic simulations reveals that some contemporary simulations underpredict the recent evolution of the low-mass SFS. This demonstrates that the recent evolution of the low-mass SFS can provide new constraints on the assembly of the low-mass Universe and highlights the need for improved models in this regime.

SPYGLASS. V. Spatially and Temporally Structured Star-forming Environments in the Cepheus-Hercules Complex

Young associations record complete histories of star-forming events through their demographics and dynamics, and Gaia has greatly expanded our knowledge of these associations. We present the first structural and dynamical overview study of the Cep-Her Complex, which has recently emerged as the largest stellar population within 500 pc that still lacks substantial follow-up. We reveal that Cep-Her is not a singular association, but rather an amalgam of four, consisting of the older (τ > 100 Myr) open cluster Roslund 6, in addition to three dynamically coherent and highly substructured young associations that we focus on: Orpheus (25–40 Myr), Cinyras (28–43 Myr), and Cupavo (54–80 Myr). With 9552 ± 960 stars in Orpheus, 3872 ± 455 stars in Cinyras, and 8794 ± 1827 stars in Cupavo, all three are among the largest young associations within 500 pc, rivalling major associations like Sco-Cen. Our novel view of the ages and dynamics of these associations reveals evidence for sequential star formation in Cinyras, in addition to a multiorigin pattern of stellar dispersal in Orpheus that may hint to the presence of multiple clouds at formation. Dynamical simulations indicate that, while some embedded open clusters and central components of these associations are converging, they likely lack the mass necessary to capture one another and undergo hierarchical cluster assembly. Our results provide our first view of the complex star-forming environments that gave rise to the associations of Cep-Her, which will serve as important laboratories for future studies of star and planet formation.

Pop-cosmos: A Comprehensive Picture of the Galaxy Population from COSMOS Data

We present pop-cosmos: a comprehensive model characterizing the galaxy population, calibrated to 140,938 (r < 25 selected) galaxies from the Cosmic Evolution Survey (COSMOS) with photometry in 26 bands from the ultraviolet to the infrared. We construct a detailed forward model for the COSMOS data, comprising: a population model describing the joint distribution of galaxy characteristics and its evolution (parameterized by a flexible score-based diffusion model); a state-of-the-art stellar population synthesis model connecting galaxies’ intrinsic properties to their photometry; and a data model for the observation, calibration, and selection processes. By minimizing the optimal transport distance between synthetic and real data, we are able to jointly fit the population and data models, leading to robustly calibrated population-level inferences that account for parameter degeneracies, photometric noise and calibration, and selection. We present a number of key predictions from our model of interest for cosmology and galaxy evolution, including the mass function and redshift distribution; the mass–metallicity-redshift and fundamental metallicity relations; the star-forming sequence; the relation between dust attenuation and stellar mass, star formation rate, and attenuation-law index; and the relation between gas-ionization and star formation. Our model encodes a comprehensive picture of galaxy evolution that faithfully predicts galaxy colors across a broad redshift (z < 4) and wavelength range.

BreakBRD Galaxies: Evolutionary Clues through an Analysis of Gas Content

By combining newly obtained deep Green Bank Telescope 21 cm observations with optical spectroscopic data, we present an analysis of the gas content of break bulges in red disks (breakBRD) galaxies, a population denoted by their blue star-forming centers and red quenched disks that do not appear to follow the typical inside-out evolution of spiral galaxies. We confirm previous results that the neutral atomic hydrogen (H i) gas fractions of breakBRDs are, on average, lower than those of typical galaxies on the star-forming sequence (SFS), and find that their H i fractions are generally higher than green valley (GV) galaxies. H i depletion times for breakBRDs are roughly an order of magnitude lower than those of SFS galaxies, in stark contrast with GV galaxies that typically have much longer depletion times than SFS galaxies. The nuclear gas-phase metallicities of breakBRDs have a broader distribution than SFS galaxies and are skewed toward slightly above-average values. BreakBRDs are systematically offset from the baryonic Tully–Fisher relation toward lower baryonic mass at a given rotation velocity. They also have higher typical H i asymmetries than SFS galaxies, and of those galaxies with spatially resolved gas velocity fields from the Sloan Digital Sky Survey IV Mapping Nearby Galaxies at Apache Point Observatory survey, two-thirds are either highly distorted or completely misaligned relative to the stellar disk. Evidence supports a scenario where breakBRDs are in an early phase of quenching, and there is mixed evidence that their behavior is related to past merger activity.

Age of Massive Galaxies at Redshift 8

Recent James Webb Space Telescope data analyses have shown that massive red galaxies existed at redshifts z ≳ 6, a discovery that is difficult to understand in the context of standard cosmology (ΛCDM). Here, we analyze these observations more deeply, by fitting a stellar population model to the optical and near-infrared photometric data. These fits include a main stellar population in addition to a residual younger population and with the same extinction for both (a lower extinction for the younger population is unphysical). Extra stellar populations or the inclusion of an active galactic nucleus component do not significantly improve the fits. These galaxies are being viewed at very high redshifts, with an average 〈z〉 ≈ 8.2, when the ΛCDM Universe was only ≈600 Myr old. This result conflicts with the inferred ages of these galaxies, however, which were on average between 0.9 and 2.4 Gyr old within a 95% confidence level. Given the sequence of star formation and galaxy assembly in the standard model, these galaxies should instead be even younger than 290 Myr on average, for which our analysis assigns a probability of only <3 × 10−4 (≳3.6σ tension). This outcome may indicate the need to consider nonstandard cosmologies. Nevertheless, our conclusions result from several approximations in stellar astrophysics and extinction, so they should be taken with a grain of salt. Further research is necessary to corroborate the possible existence of galaxies older than the ΛCDM Universe at their observed redshifts.

Simulating nearby disc galaxies on the main star formation sequence

Past studies have long emphasised the key role played by galactic stellar bars in the context of disc secular evolution, via the redistribution of gas and stars, the triggering of star formation, and the formation of prominent structures such as rings and central mass concentrations. However, the exact physical processes acting on those structures, as well as the timescales associated with the building and consumption of central gas reservoirs are still not well understood. We are building a suite of hydro-dynamical RAMSES simulations of isolated, low-redshift galaxies that mimic the properties of the PHANGS sample. The initial conditions of the models reproduce the observed stellar mass, disc scale length, or gas fraction, and this paper presents a first subset of these models. Most of our simulated galaxies develop a prominent bar structure, which itself triggers central gas fuelling and the building of an over-density with a typical scale of 100−1000 pc. We confirm that if the host galaxy features an ellipsoidal component, the formation of the bar and gas fuelling are delayed. We show that most of our simulations follow a common time evolution, when accounting for mass scaling and the bar formation time. In our simulations, the stellar mass of 1010 M⊙ seems to mark a change in the phases describing the time evolution of the bar and its impact on the interstellar medium. In massive discs (M⋆ ≥ 1010 M⊙), we observe the formation of a central gas reservoir with star formation mostly occurring within a restricted starburst region, leading to a gas depletion phase. Lower-mass systems (M⋆ &lt; 1010 M⊙) do not exhibit such a depletion phase, and show a more homogeneous spread of star-forming regions along the bar structure, and do not appear to host inner bar-driven discs or rings. Our results seem to be supported by observations, and we briefly discuss how this new suite of simulations can help our understanding of the secular evolution of main sequence disc galaxies.

EPOCHS Paper V. The dependence of galaxy formation on galaxy structure at z &amp;lt; 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 &amp;lt; 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 disc galaxies dominate the structures of galaxies at z &amp;lt; 7, we find that these discs 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 &amp;lt; 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 &amp;gt; 1.5. We also find that the stellar mass function for disc 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.

PDRs4All

Context. TheJames WebbSpace Telescope (JWST) has captured the most detailed and sharpest infrared (IR) images ever taken of the inner region of the Orion Nebula, the nearest massive star formation region, and a prototypical highly irradiated dense photo-dissociation region (PDR).Aims. We investigate the fundamental interaction of far-ultraviolet (FUV) photons with molecular clouds. The transitions across the ionization front (IF), dissociation front (DF), and the molecular cloud are studied at high-angular resolution. These transitions are relevant to understanding the effects of radiative feedback from massive stars and the dominant physical and chemical processes that lead to the IR emission that JWST will detect in many Galactic and extragalactic environments.Methods. We utilized NIRCam and MIRI to obtain sub-arcsecond images over ~150″ and 42″ in key gas phase lines (e.g., Paα, Brα, [FeII] 1.64 µm, H21−0 S(1) 2.12 µm, 0–0 S(9) 4.69 µm), aromatic and aliphatic infrared bands (aromatic infrared bands at 3.3–3.4 µm, 7.7, and 11.3 µm), dust emission, and scattered light. Their emission are powerful tracers of the IF and DF, FUV radiation field and density distribution. Using NIRSpec observations the fractional contributions of lines, AIBs, and continuum emission to our NIRCam images were estimated. A very good agreement is found for the distribution and intensity of lines and AIBs between the NIRCam and NIRSpec observations.Results. Due to the proximity of the Orion Nebula and the unprecedented angular resolution of JWST, these data reveal that the molecular cloud borders are hyper structured at small angular scales of ~0.1–1″ (~0.0002–0.002 pc or ~40–400 au at 414 pc). A diverse set of features are observed such as ridges, waves, globules and photoevaporated protoplanetary disks. At the PDR atomic to molecular transition, several bright features are detected that are associated with the highly irradiated surroundings of the dense molecular condensations and embedded young star. Toward the Orion Bar PDR, a highly sculpted interface is detected with sharp edges and density increases near the IF and DF. This was predicted by previous modeling studies, but the fronts were unresolved in most tracers. The spatial distribution of the AIBs reveals that the PDR edge is steep and is followed by an extensive warm atomic layer up to the DF with multiple ridges. A complex, structured, and folded H0/H2DF surface was traced by the H2lines. This dataset was used to revisit the commonly adopted 2D PDR structure of the Orion Bar as our observations show that a 3D “terraced” geometry is required to explain the JWST observations. JWST provides us with a complete view of the PDR, all the way from the PDR edge to the substructured dense region, and this allowed us to determine, in detail, where the emission of the atomic and molecular lines, aromatic bands, and dust originate.Conclusions. This study offers an unprecedented dataset to benchmark and transform PDR physico-chemical and dynamical models for the JWST era. A fundamental step forward in our understanding of the interaction of FUV photons with molecular clouds and the role of FUV irradiation along the star formation sequence is provided.

Post-starburst Galaxies in SDSS-IV MaNGA: Two Broad Categories of Evolutionary Pathways

We study the size–mass relation (SMR) and recent star formation history (SFH) of post-starburst (PSB) galaxies in the local Universe using spatially resolved spectroscopy from the final data release of MaNGA. Our sample includes 489 PSB galaxies: 94 cPSB galaxies with central PSB regions, 85 rPSB galaxies with ringlike PSB regions, and 310 iPSB galaxies with irregular PSB regions. When compared to control galaxies of similar star formation rate, redshift, and mass, a similar SMR is found for all types of PSB samples except the cPSB galaxies, which have smaller sizes at intermediate masses ( 9.5≲log10(M*/M⊙)≲10.5 ). The iPSB galaxies in the star-forming sequence (iPSB-SF) show no/weak gradients in D n (4000), EW(Hδ A ), and EW(Hα), consistent with the global star-forming status of this type of galaxy, while the quiescent iPSB (iPSB-Q) sample shows negative gradients in D n (4000) and positive gradients in EW(Hδ A ), indicating older stellar populations in the inner regions. Both the cPSB and rPSB samples show positive gradients in D n (4000) and negative gradients in EW(Hδ A ), indicating younger stellar populations in the inner regions. These results imply that the four types of PSB galaxies can be broadly divided into two distinct categories in terms of evolutionary pathway: (1) iPSB-SF and iPSB-Q, which have SMRs and SFHs similar to control galaxies, preferring an inside-out quenching process, and (2) rPSB and cPSB, which appear to be different stages of the same event and likely to follow the outside-in quenching process driven by disruption events such as mergers that result in a more compact structure as quenching proceeds.

Enhanced star formation and metallicity deficit in the USS 1558−003 forming protocluster at z = 2.53

ABSTRACT We use K-band multi-object near-infrared spectroscopy with Keck/MOSFIRE to search for environmental imprints on the gas properties of 27 narrow-band selected H α emitters (HAEs) across the three major clumps of the assembling USS1558−003 protocluster at z = 2.53. We target the H α and [N ii]λ6584 emission lines to obtain star formation rates (SFR) and gas-phase oxygen abundances for our sources, confirming the membership of 23 objects. HAEs belonging to this protocluster display enhanced SFRs with respect to the main sequence of star formation at the same cosmic epoch. This effect is more prominent for low-mass galaxies ($\mathrm{\log \mathit{ M}_*/M_\odot \lt 10.0}$), which may be experiencing a vigorous phase of mass assembly shortly after they were formed. We compute the individual and stacked gas-phase metallicities for our sources finding a metallicity deficit for low-mass objects when compared against the field mass–metallicity relation and the massive Spiderweb protocluster at z = 2.16. These results suggest that HAEs within USS1558−003 may be less evolved than those in the Spiderweb protocluster. Finally, we explore the gas metallicity–gas fraction relation for a small sample of five galaxies with CO(3–2) molecular gas information. Assuming our objects are in equilibrium, we obtain a relatively wide range of mass loading factors (λ = 0.5–2) matching field samples at the cosmic noon but in contrast with our previous results in the Spiderweb protocluster. We speculate that these discrepancies between protoclusters may be (partly) driven by differences in their current dynamical and mass assembly stages, hinting at the co-evolution of protoclusters and their galaxy populations at 2 &amp;lt; z &amp;lt; 3.

CEERS: MIRI deciphers the spatial distribution of dust-obscured star formation in galaxies at 0.1 &lt; z &lt; 2.5

Aims. We study the stellar (i.e., rest-optical) and dust-obscured star-forming (i.e., rest-mid-infrared) morphologies (i.e., sizes and Sérsic indices) of star-forming galaxies (SFGs) at 0.1 &lt; z &lt; 2.5. Methods. We combined Hubble Space Telescope (HST) images from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) with JWST images from the Cosmic Evolution Early Release Science (CEERS) survey to measure the stellar and dust-obscured star formation distributions of 69 SFGs. Rest-mid-infrared (rest-MIR) morphologies were determined using a Markov chain Monte Carlo (MCMC) approach applied to the sharpest Mid-InfraRed Instrument (MIRI) images (i.e., shortest wavelength) dominated by dust emission (Sνdust/Sνtotal &gt; 75%), as inferred for each galaxy from our optical-to-far-infrared spectral energy distribution fits with CIGALE. Rest-MIR Sérsic indices were only measured for the brightest MIRI sources, that is, with a signal-to-noise (S/N) greater than 75 (35 galaxies). At a lower S/N, simulations do indeed show that simultaneous measurements of both the size and Sérsic index become less reliable. We extended our study to fainter sources (i.e., S/N &gt; 10; 69 galaxies) by restricting our structural analysis to their rest-MIR sizes (ReMIR) and by fixing their Sérsic index to a value of one. Results. Our MIRI-selected sample corresponds to a mass-complete sample (&gt; 80%) of SFGs down to stellar masses 109.5, 109.5, and 1010 M⊙ at z ∼ 0.3, 1, and 2, respectively. The rest-MIR Sérsic index of bright galaxies (S/N &gt; 75) has a median value of 0.7−0.3+0.8 (the range corresponds to the 16th and 84th percentiles), which is in good agreement with their median rest-optical Sérsic indices. The Sérsic indices as well as the distribution of the axis ratio of these galaxies suggest that they have a disk-like morphology in the rest-MIR. Galaxies above the main sequence (MS) of star formation (i.e., starbursts) have rest-MIR sizes that are, on average, a factor ∼2 smaller than their rest-optical sizes (ReOpt.). The median rest-optical to rest-MIR size ratio of MS galaxies increases with their stellar mass, from 1.1−0.2+0.4 at ∼109.8 M⊙ to 1.6−0.3+1.0 at ∼1011 M⊙. This mass-dependent trend resembles the one found in the literature between the rest-optical and rest-near-infrared sizes of SFGs, suggesting that it is primarily due to radial color gradients affecting rest-optical sizes and that the sizes of the stellar and star-forming components of SFGs are, on average, consistent at all masses. There is, however, a small population of SFGs (∼15%) with a compact star-forming component embedded in a larger stellar structure, with ReOpt.c &gt; 1.8 × ReMIR. This population could be the missing link between galaxies with an extended stellar component and those with a compact stellar component, the so-called blue nuggets.

Photoevaporation versus enrichment in the cradle of the Sun

ABSTRACT The presence of short-lived radioisotopes (SLRs) 26Al and 60Fe in the Solar system places constraints on the initial conditions of our planetary system. Most theories posit that the origin of 26Al and 60Fe is in the interiors of massive stars, and they are either delivered directly to the protosolar disc from the winds and supernovae of the massive stars, or indirectly via a sequential star formation event. However, massive stars that produce SLRs also emit photoionizing far and extreme ultraviolet radiation, which can destroy the gas component of protoplanetary discs, possibly precluding the formation of gas giant planets like Jupiter and Saturn. Here, we perfom N-body simulations of star-forming regions and determine whether discs that are enriched in SLRs can retain enough gas to form Jovian planets. We find that discs are enriched and survive the photoionizing radiation only when the dust radius of the disc is fixed and not allowed to move inwards due to the photoevaporation, or outwards due to viscous spreading. Even in this optimal scenario, not enough discs survive until the supernovae of the massive stars and so have zero or very little enrichment in 60Fe. We therefore suggest that the delivery of SLRs to the Solar system may not come from the winds and supernovae of massive stars.

The ionizing photon production efficiency of bright z ∼ 2 − 5 galaxies

Aims. We investigate the production efficiency of ionizing photons (ξion∗) of 1174 galaxies with secure redshift at z = 2 − 5 from the VANDELS survey to determine the relation between ionizing emission and physical properties of bright and massive sources. Methods. We constrained ξion∗ and galaxy physical parameters by means of spectrophotometric fits performed with the BEAGLE code. The analysis exploits the multi-band photometry in the VANDELS fields and the measurement of UV rest-frame emission lines (CIII]λ1909, HeIIλ1640, and OIII]λ1666) from deep VIMOS spectra. Results. We find no clear evolution of ξion∗ with redshift within the probed range. The ionizing efficiency slightly increases at fainter MUV and bluer UV slopes, but these trends are less evident when the analysis is restricted to a complete subsample at log(Mstar/M⊙) &gt; 9.5. We find a significant trend of increasing ξion∗ with increasing EW(Lyα), with an average log(ξion∗/Hz erg−1) &gt; 25 at EW &gt; 50 Å and a higher ionizing efficiency for high-EW CIII]λ1909 and OIII]λ1666 emitters. The most significant correlations are found with respect to stellar mass, specific star formation rate (sSFR), and SFR surface density (ΣSFR). The relation between ξion∗ and sSFR increases monotonically from log(ξion∗/Hz erg−1)∼24.5 at log(sSFR) ∼ −9.5 yr−1 to ∼25.5 at log(sSFR) ∼ −7.5 yr−1. This relation has a low scatter and only a weak dependence on mass. The objects above the main sequence of star formation consistently have higher than average ξion∗. A clear increase in ξion∗ with ΣSFR is also found, with log(ξion∗/Hz erg−1) &gt; 25 for objects at ΣSFR &gt; 10 M⊙ yr−1 kpc−2. Conclusions. Bright (MUV ≲ 20) and massive (log(Mstar/M⊙)≳9.5) galaxies at z = 2 − 5 have a moderate ionizing efficiency. However, the correlation between ξion∗ and sSFR, together with the known increase in the average sSFR with redshift at fixed stellar mass, suggests that similar galaxies in the epoch of reionization can be efficient sources of ionizing photons. The availability of sSFR and ΣSFR as proxies for ξion∗ can be fundamentally important in determining the role of galaxy populations at z ≳ 10 that were recently discovered by the James Webb Space Telescope in the onset of reionization.

The [O iii] Profiles of Far-infrared Active and Inactive Optically Selected Green Valley Galaxies

We present a study of the [O iii] λ5007 line profile in a subsample of eight active galactic nuclei (AGNs) and six non-AGNs in the optically selected green valley at z < 0.5 using long-slit spectroscopic observations obtained with the 11 m Southern African Large Telescope. Gaussian decomposition of the line profile was performed to study its different components. We observe that the AGN profiles are more complex than the non-AGN ones. In particular, in most AGNs (5/8) we detect a blue wing of the line. We derive the FWHM velocities of the wing and systemic component, and find that the AGNs show higher FWHM velocities than the non-AGNs in their core component. We also find that the AGNs show blue wings with a median velocity width of approximately 600 km s−1, and a velocity offset from the core component in the range −90 to −350 km s−1, in contrast to the non-AGN galaxies, where we do not detect blue wings in any of their [O iii] λ5007 line profiles. Using the spatial information in our spectra, we show that at least three of the outflow candidate galaxies have centrally driven gas outflows extending across the whole galaxy. Moreover, these are also the galaxies which are located on the main sequence of star formation, raising the possibility that the AGNs in our sample are influencing the star formation of their host galaxies (such as positive feedback). This is in agreement with our previous work where we studied the star formation, morphology, and stellar population properties of a sample of green valley AGNs and non-AGN galaxies.

Spectroscopy of the supernova H0pe host galaxy at redshift 1.78

Supernova (SN) H0pe was discovered as a new transient in James Webb Space Telescope (JWST) NIRCam images of the galaxy cluster PLCK G165.7+67.0 taken as part of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) JWST GTO program (ID 1176) on 2023 March 30. The transient is a compact source associated with a background galaxy that is stretched and triply imaged by the strong gravitational lensing of the cluster. This paper reports spectra in the 950–1370 nm observer frame of two of the galaxy images obtained with Large Binocular Telescope (LBT) Utility Camera in the Infrared (LUCI) in long-slit mode two weeks after the JWST observations. The individual and average spectra show the [O II] λλ3727,3730 doublet and the Balmer and 4000 Å breaks at redshift z = 1.783 ± 0.002. The code investigating galaxy emission (CIGALE) best-fit model of the spectral energy distribution indicates that the host galaxy of SN H0pe is massive (Mstar ≃ 6 × 1010 M⊙ after correcting for a magnification factor μ ∼ 7) with a predominantly intermediate-age (∼2 Gyr) stellar population, moderate extinction, and a magnification-corrected star formation rate ≃13 M⊙ yr−1, consistent with being below the main sequence of star formation. These properties suggest that H0pe might be a type Ia SN. Additional observations of SN H0pe and its host recently carried out with JWST (JWST-DD-4446; PI: B. Frye) will be able to both determine the SN classification and confirm its association with the galaxy analyzed in this work.

The relationship between the incidence of X-ray selected AGN in nearby galaxies &amp; star-formation rate

ABSTRACT We present the identification and analysis of an X-ray selected AGN sample that lie within the local (z &amp;lt; 0.35) galaxy population. From a parent sample of 22 079 MPA-JHU (based on SDSS DR8) galaxies, we identified 917 galaxies with central, excess X-ray emission (from 3XMM-DR7) likely originating from an AGN. We measured the host galaxies’ star formation rates and classified them as either star-forming or quiescent based on their position relative to main sequence of star formation. Only 72 per cent of the X-ray selected sample were identified as AGN using BPT selection; this technique is much less effective in quiescent hosts, only identifying 50 per cent of the X-ray AGN. We also calculated the growth rates of the black holes powering these AGN in terms of their specific accretion rate (∝ LX/M*) and found quiescent galaxies, on average, accrete at a lower rate than star-forming galaxies. Finally, we measured the sensitivity function of 3XMM so we could correct for observational bias and construct probability distributions as a function of accretion rate. AGN were found in galaxies across the full range of star formation rates ($\log _{10} \, \mathrm{SFR/M_\odot \ yr^{-1}} = -3\ \mathrm{to}\ 2$) in both star-forming and quiescent galaxies. The incidence of AGN was enhanced by a factor 2 (at a 3.5σ significance) in star-forming galaxies compared to quiescent galaxies of equivalent stellar mass and redshift, but we also found a significant population of AGN hosted by quiescent galaxies.

Main Sequence and Quenching of Star Formation based on Simulations from IllustrisTNG

Star formation plays a crucial role in the field of astrophysics and cosmology. In this paper, the simulation IllustrisTNG is used to recreate the main sequence of star-formation, which explored the relation between the mass of as well as the star-formation rate (SFR). Graphs of different redshifts were investigated based on ordinary least square linear regression fitting, where the trend of star formation main sequence is seen. The slopes and y-intercepts will be discussed regarding the main sequence of star formation, which has already been proved by different researchers in the past few years. However, unlike the main sequence of star formation, the quenching process still doesn’t have a proper explanation. Nevertheless, in this paper, star formation quenching was shown in the images and a possible solution to star formation quenching is proposed. Overall, these results offer a new insight toward star formation quenching and offer a guideline for future investigation in terms of star formation.

JWST Insight into a Lensed HST-dark Galaxy and Its Quiescent Companion at z = 2.58

Using the novel James Webb Space Telescope (JWST)/NIRCam observations in the A2744 field, we present a first spatially resolved overview of a Hubble Space Telescope (HST)-dark galaxy, spectroscopically confirmed at z = 2.58 with magnification μ ≈ 1.9. While being largely invisible at ∼1 μm with NIRCam, except for sparse clumpy substructures, the object is well detected and resolved in the long-wavelength bands with a spiral shape clearly visible in F277W. By combining ancillary Atacama Large Millimeter/submillimeter Array (ALMA) and Herschel data, we infer that this object is an edge-on dusty spiral with an intrinsic stellar mass log (M */M ⊙) ∼ 11.3 and a dust-obscured star formation rate ∼300 M ⊙ yr−1. A massive quiescent galaxy (log (M */M ⊙) ∼ 10.8) with tidal features lies 2.″0 away (r ∼ 9 kpc), at a consistent redshift as inferred by JWST photometry, indicating a potential major merger. The dusty spiral lies on the main sequence of star formation, and shows high dust attenuation in the optical (3 < A V < 4.5). In the far-infrared, its integrated dust spectral energy distribution is optically thick up to λ 0 ∼ 500 μm, further supporting the extremely dusty nature. Spatially resolved analysis of the HST-dark galaxy reveals a largely uniform A V ∼ 4 area spanning ∼57 kpc2, which spatially matches to the ALMA 1 mm continuum emission. Accounting for the surface brightness dimming and the depths of current JWST surveys, unlensed analogs of the HST-dark galaxy at z > 4 would be only detectable in F356W and F444W in an UNCOVER-like survey, and become totally JWST-dark at z ∼ 6. This suggests that detecting highly attenuated galaxies in the Epoch of Reionization might be a challenging task for JWST.

The cosmic timeline implied by the JWST high-redshift galaxies

ABSTRACT The so-called impossibly early galaxy problem, first identified via the Hubble Space Telescope’s observation of galaxies at redshifts z &amp;gt; 10, appears to have been exacerbated by the more recent JWST discovery of galaxy candidates at even higher redshifts (z ∼ 17) which, however, are yet to be confirmed spectroscopically. These candidates would have emerged only ∼230 Myr after the big bang in the context of Lambda cold dark matter (ΛCDM), requiring a more rapid star formation in the earliest galaxies than appears to be permitted by simulations adopting the concordance model parameters. This time-compression problem would therefore be inconsistent with the age–redshift relation predicted by ΛCDM. Instead, the sequence of star formation and galaxy assembly would confirm the timeline predicted by the Rh = ct universe, a theoretically advanced version of ΛCDM that incorporates the ‘zero active mass’ condition from general relativity. This model has accounted for many cosmological data better than ΛCDM, and eliminates all of its inconsistencies, including the horizon and initial entropy problems. The latest JWST discoveries at z ≳ 14, if confirmed, would add further support to the idea that the Rh = ct universe is favoured by the observations over the current standard model.

Constraining the physical properties of the first lensed z ∼ 9 − 16 galaxy candidates with JWST

ABSTRACT The first deep-field observations of the JWST have immediately yielded a surprisingly large number of very high redshift candidates, pushing the frontier of observability well beyond z ≳ 10. We here present a detailed SED-fitting analysis of the 10 gravitationally lensed z ∼ 9–16 galaxy candidates detected behind the galaxy cluster SMACS J0723.3−7327 in a previous paper using the BEAGLE tool. Our analysis makes use of dynamical considerations to place limits on the ages of these galaxies and of all three published SL models of the cluster to account for lensing systematics. We find the majority of these galaxies to have relatively low stellar masses $M_{\star }\sim 10^7-10^8\, \mathrm{M}_{\odot }$ and young ages tage ∼ 10–100 Myr but with a few higher mass exceptions ($M_{\star }\sim 10^9\rm{-}10^{10}\, \mathrm{M}_{\odot }$) due to Balmer-break detections at z ∼ 9–10. Because of their very blue UV-slopes, down to β ∼ −3, all of the galaxies in our sample have extremely low dust attenuations AV ≲ 0.02. Placing the measured parameters into relation, we find a very shallow M⋆ − MUV-slope and high sSFRs above the main sequence of star formation with no significant redshift-evolution in either relation. This is in agreement with the bright UV luminosities measured for these objects and indicates that we are naturally selecting UV-bright galaxies that are undergoing intense star formation at the time they are observed. Finally, we discuss the robustness of our high-redshift galaxy sample regarding low-redshift interlopers and conclude that low-redshift solutions can safely be ruled out for roughly half of the sample, including the highest redshift galaxies at z ∼ 12–16. These objects represent compelling targets for spectroscopic follow-up observations with JWST and ALMA.