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Relic galaxies, the oldest ultra-compact massive galaxies (UCMGs), contain almost exclusively 'pristine' stars formed during an intense star formation (SF) burst at high redshift. As such, they allow us to study in detail the early mechanism of galaxy assembly in the Universe. Using the largest catalogue of spectroscopically confirmed UCMGs for which a degree of relicness (DoR) had been estimated, the INSPIRE catalogue, we investigate whether or not relics prefer dense environments. The objective of this study is to determine if the DoR, which measures how extreme the SF history was, and the surrounding environment are correlated. In order to achieve this goal, we employ the AMICO galaxy cluster catalogue to compute the probability for a galaxy to be a member of a cluster, and measure the local density around each UCMG using machine learning-based photometric redshifts. We find that UCMGs can reside both in clusters and in the field, but objects with very low DoR (⁠|$\lt 0.3$|⁠ , i.e. a relatively extended SF history) prefer underdense environments. We additionally report a correlation between the DoR and the distance from the cluster centre: more extreme relics, when located in clusters, tend to occupy the more central regions of them. We finally outline potential evolution scenarios for UCMGs at different DoR to reconcile their presence in both clusters and field environments. [ABSTRACT FROM AUTHOR]

Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionize the study of tidal features. However, the volume of data will prohibit visual inspection to identify features, thereby motivating a need to develop automated detection methods. This paper presents a visual classification of ∼2000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells , and diffuse. We trained a convolutional neural network (CNN) to reproduce the assigned visual classifications using these labels. Evaluated on a testing set where galaxies with tidal features were outnumbered |$\sim 1:10$|⁠ , our network performed very well and retrieved a median |$98.7\pm 0.3$|⁠ , |$99.1\pm 0.5$|⁠ , |$97.0\pm 0.8$|⁠ , and |$99.4^{+0.2}_{-0.6}$|  per  cent of the actual instances of arm, stream, shell , and diffuse features respectively for just 20 per cent contamination. A modified version that identified galaxies with any feature against those without achieved scores of |$0.981^{+0.001}_{-0.003}$|⁠ , |$0.834^{+0.014}_{-0.026}$|⁠ , |$0.974^{+0.008}_{-0.004}$|⁠ , and |$0.900^{+0.073}_{-0.015}$| for the accuracy, precision, recall, and F1 metrics, respectively. We used a gradient-weighted class activation mapping analysis to highlight important regions on images for a given classification to verify the network was classifying the galaxies correctly. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver. [ABSTRACT FROM AUTHOR]

Modern cosmology rests on the cosmological principle , that on large enough scales the Universe is both homogeneous and isotropic. A corollary is that galaxies' spin vectors should be isotropically distributed on the sky. This has been challenged by multiple authors for over a decade, with claims to have detected a statistically significant dipole pattern of spins. We collect all publicly available data sets with spin classifications (binary Z-wise/S-wise), and analyse them for large-angle anisotropies (⁠|$\ell \le 2$|⁠). We perform each inference in both a Bayesian and frequentist fashion, the former establishing posterior probabilities on the multipole parameters and the latter calculating p -values for rejection of the null hypothesis of isotropy (i.e. no power at |$\ell \gt 0$|⁠). All analysis indicate consistency with isotropy to within |$3\sigma$|⁠. We similarly identify no evidence for a 'hemisphere anisotropy' that neglects the angular dependence of the dipole. We isolate the differences with contrary claims in the ad hoc or biased statistics that they employ. Our code is publicly available. [ABSTRACT FROM AUTHOR]

We use high-resolution magnetohydrodynamic simulations of isolated disc galaxies to investigate the co-evolution of magnetic fields with a self-regulated, star-forming interstellar medium (ISM). The simulations are conducted using the ramses adaptive mesh refinement code on the standard agora initial condition, with gas cooling, star formation, and feedback. We run galaxies with a variety of initial magnetic field strengths. The fields evolve and achieve approximate saturation within 500 Myr, but at different levels. The galaxies reach a quasi-steady state, with slowly declining star formation due to both gas consumption and increase in the field strength at intermediate ISM densities. We connect this behaviour to differences in the gas properties and overall structure of the galaxies. Stronger magnetic fields limit supernova bubble sizes. Different cases support the ISM using varying combinations of magnetic pressure, turbulence, and thermal energy. Initially, |$\gtrsim\!\! 1\ \mu \mathrm{ G}$| magnetic fields evolve modestly and dominate support at all radii. Conversely, initially weaker fields grow through feedback and turbulence but never dominate the support. This is reflected in the stability of the gas disc. This interplay determines the overall distribution of star formation in each case. We conclude that an initially weak field can grow to produce a realistic model of a local disc galaxy, but starting with typically assumed field strengths (⁠|$\gtrsim\!\! 1\ \mu \mathrm{ G}$|⁠) will not. [ABSTRACT FROM AUTHOR]

The circular velocity function (CVF) of galaxies is a fundamental test of the Lambda cold dark matter (⁠|$\Lambda$| CDM) paradigm as it traces the variation of galaxy number densities with circular velocity (⁠|$v_{\rm {circ}}$|⁠), a proxy for dynamical mass. Previous observational studies of the CVF have either been based on H  i -rich galaxies, or encompassed low-number statistics and probed narrow ranges in |$v_{\rm {circ}}$|⁠. We present a benchmark computation of the CVF between |$100\,{\text{and}}\,350\ \rm {km\ s^{-1}}$| using a sample of 3527 nearby Universe galaxies, representative for stellar masses between |$10^{9.2}\,{\text{and}}\,10^{11.9} \rm {{\rm M}_{\odot }}$|⁠. We find significantly larger number densities above 150 |$\rm {km\ s^{-1}}$| compared to results from H  i surveys, pertaining to the morphological diversity of our sample. Leveraging the fact that circular velocities are tracing the gravitational potential of haloes, we compute the halo mass function (HMF), covering |$\sim$| 1 dex of previously unprobed halo masses (⁠|$10^{11.7}{\!-\!}10^{12.7} \rm {{\rm M}_{\odot }}$|⁠). The HMF for our sample, representative of the galaxy population with |$M_{200}\geqslant 10^{11.35} \rm {{\rm M}_{\odot }}$|⁠ , shows that spiral morphologies contribute 67 per cent of the matter density in the nearby Universe, while early types account for the rest. We combine our HMF data with literature measurements based on H  i kinematics and group/cluster velocity dispersions. We constrain the functional form of the HMF between |$10^{10.5}-10^{15.5} \rm {{\rm M}_{\odot }}$|⁠ , finding a good agreement with |$\Lambda$| CDM predictions. The halo mass range probed encompasses 72 |$\substack{+5 -6}$| per cent (⁠|$\Omega _{\rm {M,10.5-15.5}} = 0.227 \pm 0.018$|⁠) of the matter density in the nearby Universe; 31 |$\substack{+5 -6}$| per cent is accounted for by haloes below |$10^{12.7}\rm {{\rm M}_{\odot }}$| occupied by a single galaxy. [ABSTRACT FROM AUTHOR]

We explain the large variety of star formation laws in terms of one single, simple law that can be inferred from the definition of the star formation rate and basic algebra. The resulting equation, |${\rm SFR}= {\epsilon _\mathrm{ff}}\ M_\mathrm{collapse}/{\tau _{\rm ff}}$|⁠ , although it has been presented elsewhere, is interpreted in terms of clouds undergoing collapse rather than being turbulence supported, an idea that different groups have pursued this century. Under such assumption, one can explain the constancy of |${\epsilon _\mathrm{ff}}$|⁠ , the different intra-cloud correlations observed in Milky Way's molecular clouds, as well as the resolved and unresolved extragalactic relationships between SFR and a measurement of the mass in CO, HCN, and CO + HI. We also explain why the slope of the correlation changes when the orbital time |${\tau _{\rm orb}}$| is considered instead of the free-fall time, and why estimations of the free-fall time from extragalactic observations skew the correlation, providing a false sublinear correlation. We furthermore show that the apparent nearly linear correlation between the star formation rate and the dynamical equilibrium pressure in the mid-plane of the galaxies, |$P_{\rm DE}$|⁠ , is just a consequence of |$P_{\rm DE}$| values being dominated by the variation of the column density of molecular gas. All in all, we argue that the star formation law is driven by the collapse of cold, dense gas, which happens to be primarily molecular in the present Universe, and that the role of stellar feedback is just to shut down the star formation process, not to shape the star formation law. [ABSTRACT FROM AUTHOR]

The terahertz frequency region of the electromagnetic spectrum is crucial for understanding the formation and evolution of galaxies and stars throughout the universe's history, as well as the process of planet formation. Detecting the unique spectral signatures of molecules and atoms requires terahertz spectrometers, which must be operated in space observatories due to water vapor absorption in the Earth's atmosphere. However, current terahertz spectrometers face challenges such as low resolution, limited bandwidth, large volume, and complexity. In this paper, the issues of size and weight are addressed by demonstrating a concept for a centimeter‐sized, low‐weight terahertz spectrometer using a metasurface. The design of the metasurface spectrometer is first discussed for the 1.85 to 2.4 THz range, followed by its fabrication. Next, an array of quantum cascade lasers operating at slightly different frequencies around 2.1 THz is utilized to characterize the spectrometer. Finally, a spectrum inversion method is applied to analyze the measured data, confirming a resolution R (λ/Δλ) of at least 273. This concept can be extended to other application areas, such as planetary observations and various wavelengths in the far‐infrared (FIR) and near‐infrared (NIR) ranges. [ABSTRACT FROM AUTHOR]

Mergers of and interactions between galaxies imprint a wide diversity of morphological, dynamical, and chemical characteristics in stellar halos and tidal streams. Measuring these characteristics elucidates aspects of the progenitors of the galaxies we observe today. The M81 group is the perfect galaxy group to understand the past, present, and future of a group of galaxies in the process of merging. Here, we measure the end of star formation (t 90) and metallicity ([M/H]) of the stellar halo of M82 and the eastern tidal stream of NGC 3077 to: (1) test the idea that M82 possesses a genuine stellar halo, formed before any interaction with M81; (2) determine if NGC 3077's tidal disruption is related to the star formation history in its tails; and (3) create a timeline of the assembly history of the central trio in the M81 group. We argue that M82 possesses a genuine, metal-poor ([M/H] ∼ −1.62 dex) stellar halo, formed from the merger of a small satellite galaxy roughly 6.6 Gyr ago. We also find that the stars present in NGC 3077's tails formed before tidal disruption with M81, and possess a roughly uniform metallicity as shown in S. Okamoto et al., implying that NGC 3077's progenitor had significant population gradients. Finally, we present a timeline of the central trio's merger/interaction history. [ABSTRACT FROM AUTHOR]

Bursty star formation—a key prediction for high-redshift galaxies from cosmological simulations explicitly resolving stellar feedback in the interstellar medium—has recently been observed to prevail among galaxies at redshift z ≳ 6. Line intensity mapping (LIM) of the 158 μ m [C ii ] line as a star formation rate (SFR) indicator offers unique opportunities to tomographically constrain cosmic star formation at high redshift, in a way complementary to observations of individually detected galaxies. To understand the effects of bursty star formation on [C ii ] LIM, which have remained unexplored in previous studies, we present an analytic modeling framework for high- z galaxy formation and [C ii ] LIM signals that accounts for bursty star formation histories induced by delayed supernova feedback. We use it to explore and characterize how bursty star formation can impact and thus complicate the interpretation of the [C ii ] luminosity function and power spectrum. Our simple analytic model indicates that bursty star formation mainly affects low-mass galaxies by boosting their average SFR and [C ii ] luminosity, and in the [C ii ] power spectrum it can create a substantial excess in the large-scale clustering term. This distortion results in a power spectrum shape that cannot be explained by invoking a mass-independent logarithmic scatter. We conclude that burstiness must be accounted for when modeling and analyzing [C ii ] data sets from the early Universe, and that in the extreme, the signature of burstiness may be detectable with first-generation experiments such as TIME, CONCERTO, and CCAT-DSS. [ABSTRACT FROM AUTHOR]

We use high-resolution (⁠|$\simeq$| 35pc) hydrodynamical simulations of galaxy formation to investigate the relation between gas accretion and star formation in galaxies hosted by dark matter haloes of mass |$10^{12}$| |${{\mathrm{M}}_{\odot }}$| at |$z = 2$|⁠. At high-redshift, cold-accreted gas is expected to be readily available for star formation, while gas accreted in a hot mode is expected to require a longer time to cool down before being able to form stars. Contrary to these expectations, we find that the majority of cold-accreted gas takes several hundred Myr longer to form stars than hot-accreted gas after it reaches the inner circumgalactic medium (CGM). Approximately 10 per cent of the cold-accreted gas flows rapidly through the inner CGM on to the galactic disc. The remaining 90 per cent is trapped in a turbulent accretion region that extends up to |$\sim 50$|  per cent of the virial radius, from which it takes several hundred Myr for the gas to be transported to the star-forming disc. In contrast, most hot shock-heated gas avoids this 'slow track', and accretes directly from the CGM on to the disc where stars can form. We find that shock-heating of cold gas after accretion in the inner CGM and supernova-driven outflows contribute to, but do not fully explain, the delay in star formation. These processes combined slow down the delivery of cold-accreted gas to the galactic disc and consequently limit the rate of star formation in Milky Way mass galaxies at |$z \gt 2$|⁠. [ABSTRACT FROM AUTHOR]

We decomposed the molecular gas in the spiral galaxy NGC 628 (M74) into multiscale hub-filament structures using the CO (2 |$-$| 1) line by the dendrogram algorithm. All leaf structures as potential hubs were classified into three categories, i.e. leaf-HFs-A, leaf-HFs-B and leaf-HFs-C. Leaf-HFs-A exhibit the best hub-filament morphology, which also have the highest density contrast, the largest mass and the lowest virial ratio. We employed the filfinder algorithm to identify and characterize filaments within 185 leaf-HFs-A structures, and fitted the velocity gradients around the intensity peaks. Measurements of velocity gradients provide evidence for gas inflow within these structures, which can serve as a kinematic evidence that these structures are hub-filament structures. The numbers of the associated 21 μ m and H α structures and the peak intensities of 7.7 μ m, 21 μ m, and H α emissions decrease from leaf-HFs-A to leaf-HFs-C. The spatial separations between the intensity peaks of CO and 21 μ m structures of leaf-HFs-A are larger than those of leaf-HFs-C. These evidence indicate that leaf-HFs-A are more evolved than leaf-HFs-C. There may be an evolutionary sequence from leaf-HFs-C to leaf-HFs-A. Currently, leaf-HFs-C lack a distinct gravitational collapse process that would result in a significant density contrast. The density contrast can effectively measure the extent of the gravitational collapse and the depth of the gravitational potential of the structure which, in turn, shapes the hub-filament morphology. Combined with the kinematic analysis presented in previous studies, a picture emerges that molecular gas in spiral galaxies is organized into network structures through the gravitational coupling of multiscale hub-filament structures. Molecular clouds, acting as knots within these networks, serve as hubs, which are local gravitational centres and the main sites of star formation. [ABSTRACT FROM AUTHOR]

Observations of ionized H  |$\alpha$| gas in high-redshift disc galaxies have ubiquitously found significant line broadening, |$\sigma _{\rm H\,\alpha }\sim 10{\!-\!}100\, {\rm km\, s^{-1}}$|⁠. To understand whether this broadening reflects gas turbulence within the interstellar medium (ISM) of galactic discs, or arises from out-of-plane emission in mass-loaded outflows, we perform radiation hydrodynamic simulations of isolated Milky Way-mass disc galaxies in a gas-poor (low-redshift) and gas rich (high-redshift) condition and create mock H  |$\alpha$| emission line profiles. We find that the majority of the total (integrated) |${\rm H\,\alpha }$| emission is confined within the ISM, with extraplanar gas contributing |${\sim} 45~{{\ \rm per\ cent}}$| of the extended profile wings (⁠|$v_z\ge 200$| |${\, \rm {km\, s^{-1}} }$|⁠) in the gas-rich galaxy. This substantiates using the |${\rm H\,\alpha }$| emission line as a tracer of mid-plane disc dynamics. We investigate the relative contribution of diffuse and dense |${\rm H\,\alpha }$| emitting gas, corresponding to diffuse ionized gas (DIG; |$\rho \lesssim 0.1\, {\rm cm^{-3}}$|⁠ , |$T\sim 8\, 000$|  K) and H  ii regions (⁠|$\rho \gtrsim 10\, {\rm cm^{-3}}$|⁠ , |$T\sim 10\, 000$|  K), respectively, and find that DIG contributes |$f_{\rm DIG}\lesssim 10~{{\ \rm per\ cent}}$| of the total L |$_{\rm H\alpha }$|⁠. However, the DIG can reach upwards of |$\sigma _{\rm H\,\alpha } \sim 60{\!-\!}80\, {\rm km\, s^{-1}}$| while the H  ii regions are much less turbulent |$\sigma _{\rm H\,\alpha }\sim 10{\!-\!}40\, {\rm km\, s^{-1}}$|⁠. This implies that the |$\sigma _{\rm H\,\alpha }$| observed using the full |${\rm H\,\alpha }$| emission line is dependent on the relative |${\rm H\,\alpha }$| contribution from DIG/H  ii regions and a larger |$f_{\rm DIG}$| would shift |$\sigma _{\rm H\,\alpha }$| to higher values. Finally, we show that |$\sigma _{\rm H\,\alpha }$| evolves, in both the DIG and H  ii regions, with the galaxy gas fraction. Our high-redshift equivalent galaxy is roughly twice as turbulent, except for in the DIG which has a more shallow evolution. [ABSTRACT FROM AUTHOR]

We report ultra-deep, medium-resolution spectroscopic observations for four quiescent galaxies with log |$_{10}(M_*/\mathrm{M_\odot })\gt 11$| at |$3 \lt z \lt 5$|⁠. These data were obtained with JWST NIRSpec as part of the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey, which we introduce in this work. The first two galaxies are newly selected from PRIMER UDS imaging, both at |$z=4.62$| and separated by 860 pkpc on the sky, within a larger structure for which we confirm several other members. Both formed at |$z\simeq 8-10$|⁠. These systems could plausibly merge by the present day to produce a local massive elliptical galaxy. The other two ultra-massive quiescent galaxies are previously known at |$z=3.99$| and 3.19, with the latter (ZF-UDS-7329) having been the subject of debate as potentially too old and too massive to be accommodated by the |$\Lambda$| -CDM halo-mass function. Both exhibit high stellar metallicities, and for ZF-UDS-7329 we are able to measure the |$\alpha -$| enhancement, obtaining [Mg/Fe] = |$0.42^{+0.19}_{-0.17}$|⁠. We finally evaluate whether these four galaxies are consistent with the |$\Lambda$| -CDM halo-mass function using an extreme value statistics approach. We find that the |$z=4.62$| objects and the |$z=3.19$| object are unlikely within our area under the assumption of standard stellar fractions (⁠|$f_*\simeq 0.1-0.2$|⁠). However, these objects roughly align with the most massive galaxies expected under the assumption of 100 per cent conversion of baryons to stars (⁠|$f_*$| =1). Our results suggest extreme galaxy formation physics during the first billion years, but no conflict with |$\Lambda$| -CDM cosmology. [ABSTRACT FROM AUTHOR]

The MIGHTEE survey utilizes the South African MeerKAT radio telescope to observe four extragalactic deep fields, with the aim of advancing our understanding of the formation and evolution of galaxies across cosmic time. MIGHTEE's frequency coverage encompasses the |$\textrm {H}\scriptstyle \mathrm{I}$|  line to a redshift of z |$\simeq$|  0.58, and OH megamasers to z |$\simeq$|  0.9. We present the MIGHTEE- |$\textrm {H}\scriptstyle \mathrm{I}$|  imaging products for the COSMOS field, using a total of 94.2 h on-target and a close-packed mosaic of 15 individual pointings. The spectral imaging covers two broad, relatively interference-free regions (960–1150 and 1290–1520 MHz) within MeerKAT's L -band, with up to 26 kHz spectral resolution (5.5 km s |$^{-1}$| at z  = 0). The median noise in the highest spectral resolution data is 74 μ Jy beam |$^{-1}$|⁠ , corresponding to a 5 |$\sigma$| |$\textrm {H}\scriptstyle \mathrm{I}$|  mass limit of 10 |$^{8.5}$|  M |$_{\odot }$| for a 300 km s |$^{-1}$| line at z  = 0.07. The mosaics cover |$\gt $| 4 deg |$^{2}$|⁠ , provided at multiple angular resolution / sensitivity pairings, with an angular resolution for |$\textrm {H}\scriptstyle \mathrm{I}$|  at z  = 0 of 12 arcsec. We describe the spectral line processing workflow that will be the basis for future MIGHTEE- |$\textrm {H}\scriptstyle \mathrm{I}$|  products, and validation of, and some early results from, the spectral imaging of the COSMOS field. We find no evidence for line emission at the position of the z  = 0.376 |$\textrm {H}\scriptstyle \mathrm{I}$|  line reported from the CHILES survey at a |$\gt $| 94 per cent confidence level, placing a 3 |$\sigma$| upper limit of 8.1 |$\times$|  10 |$^{9}$|  M |$_{\odot }$| on |$M_{\mathrm{HI}}$| for this galaxy. A public data release accompanies this article. [ABSTRACT FROM AUTHOR]

We follow up emission line galaxies identified through the near-infrared slitless HST /WFC3 WISP survey with VLT/FORS2 optical spectroscopy. Over 4 WISP fields, we targeted 85 of 138 line emission objects at |$0.4\lt z\lt 2$| identified in WFC3 spectroscopy. Half the galaxies are fainter than |$H_{AB}=24$|  mag, and would not have been included in many well-known surveys based on broad-band magnitude selection. We confirm 95 per cent of the initial WFC3 grism redshifts in the 38 cases where we detect lines in FORS2 spectroscopy. However, for targets which exhibited a single emission line in WFC3, up to 65 per cent at |$z\lt 1.28$| did not have expected emission lines detected in FORS2 and hence may be spurious (although this false-detection rate improves to 33 per cent using the latest public WISP emission line catalogue). From the Balmer decrement, the extinction of the WISP galaxies is consistent with |$A($| H  |$\alpha)=1$|  mag. From SED fits to multiband photometry including Spitzer |$3.6\, \mu$| m, we find a median stellar mass of |$\log _{10}(M_\star /{\rm M}_{\odot })=8.94$|⁠. Our emission-line-selected galaxies tend to lie above the star-forming main sequence (i.e. higher specific star formation rates). Using [O  iii ], [O  ii ], and H β lines to derive gas-phase metallicities, we find typically sub-solar metallicities, decreasing with redshift. Our WISP galaxies lie below the |$z=0$| mass–metallicity relation, and galaxies with higher star formation rates tend to have lower metallicity. Finally, we find a strong increase with redshift of the H α rest-frame equivalent width in this emission-line selected sample, with higher |$EW_0$| galaxies having larger [O  iii ]/H β and O32 ratios on average, suggesting lower metallicity or higher ionization parameter in these extreme emission line galaxies. [ABSTRACT FROM AUTHOR]

Data from the JWST have revealed an intriguing population of bright galaxies at high redshifts. In this work, we use extreme-value statistics to calculate the distribution [in ultraviolet (UV) magnitude] of the brightest galaxies in the redshift range |$9 \lesssim z \lesssim 16$|⁠. We combine the generalized extreme-value approach with modelling of the galaxy luminosity function. We obtain predictions of the brightest galaxies for a suite of luminosity functions, including the Schechter and double power-law functions, as well as a model parametrized by the stellar formation efficiency |$f_*$|⁠. We find that the JWST data are broadly consistent with |$f_*$| of |$5\!\!-\!\!10{{\ \rm per\, cent}}$|⁠ , and that the brightest galaxy at |$z\sim 16$| will have |$M_{\rm UV}\approx -23.5^{0.8}_{0.4}$|⁠. If |$f_*$| is dependent on halo mass, we predict |$M_{\rm UV}\approx -22.5^{0.5}_{1.5}$| for such an object. We show that extreme-value statistics not only predict the magnitude of the brightest galaxies at high redshifts, but may also be able to distinguish between models of star formation in high-redshift galaxies. [ABSTRACT FROM AUTHOR]

We explore the potential of using the low-redshift Lyman |$\alpha$| (Ly  |$\alpha$|⁠) forest surrounding luminous red galaxies (LRGs) as a tool to constrain active galactic nuclei (AGNs) feedback models. Our analysis is based on snapshots from the Illustris and IllustrisTNG simulations at a redshift of |$z=0.1$|⁠. These simulations offer an ideal platform for studying the influence of AGN feedback on the gas surrounding galaxies, as they share the same initial conditions and underlying code but incorporate different feedback prescriptions. Both simulations show significant impacts of feedback on the temperature and density of the gas around massive haloes. Following our previous work, we adjusted the UV background in both simulations to align with the observed number density of Ly  |$\alpha$| lines (⁠|$\rm dN/dz$|⁠) in the intergalactic medium and study the Ly  |$\alpha$| forest around massive haloes hosting LRGs, at impact parameters (⁠|$r_{\perp }$|⁠) ranging from 0.1 to 100 pMpc. Our findings reveal that |$\rm dN/dz$|⁠ , as a function of |$r_{\perp }$|⁠ , is approximately 1.5 to 2 times higher in IllustrisTNG compared to Illustris up to |$r_{\perp }$| of |$\sim 10$| pMpc. To further assess whether existing data can effectively discern these differences, we search for archival data containing spectra of background quasars probing foreground LRGs. Through a feasibility analysis based on these data, we demonstrate that |${\rm dN/dz} (r_{\perp })$| measurements can distinguish between feedback models of IllustrisTNG and Illustris with a precision exceeding 16 |$\sigma$|⁠. This underscores the potential of |${\rm dN/dz} (r_{\perp })$| measurements around LRGs as a valuable benchmark observation for discriminating between different feedback models. [ABSTRACT FROM AUTHOR]

We identify a low-metallicity (⁠|$12+\log ({\rm O}/{\rm H})=7.59$|⁠) Ly  |$\alpha$| -emitting galaxy at |$z=5.943$| with evidence of a strong Balmer jump, arising from nebular continuum. While Balmer jumps are sometimes observed in low-redshift star-forming galaxies, this galaxy also exhibits a steep turnover in the UV continuum. Such turnovers are typically attributed to absorption by a damped Ly  |$\alpha$| system (DLA); however, the shape of the turnover and the high observed Ly  |$\alpha$| escape fraction (⁠|$f_{\rm esc,Ly\alpha }~\sim 27~{{\ \rm per\ cent}}$|⁠) is also consistent with strong nebular two-photon continuum emission. Modelling the UV turnover with a DLA requires extreme column densities (⁠|$N_{\rm HI}\,\,\gt\,\, 10^{23}$|  cm |$^{-2}$|⁠), and simultaneously explaining the high |$f_{\rm esc,Ly\alpha }$| requires a fine-tuned geometry. In contrast, modelling the spectrum as primarily nebular provides a good fit to both the continuum and emission lines, motivating scenarios in which (a) we are observing only nebular emission or (b) the ionizing source is powering extreme nebular emission that outshines the stellar emission. The nebular-only scenario could arise if the ionizing source has 'turned off' more recently than the recombination time-scale (⁠|$\sim$| 1000 yr), hence we may be catching the object at a very specific time. Alternatively, hot stars with |$T_{\rm eff}\gtrsim 10^5$|  K (e.g. Wolf–Rayet or low-metallicity massive stars) produce enough ionizing photons such that the two-photon emission becomes visible. While several stellar SEDs from the literature fit the observed spectrum well, the hot-star scenario requires that the number of |$\gtrsim 50~{\rm M}_\odot$| stars relative to |$\sim 5\!-\!50~{\rm M}_\odot$| stars is significantly higher than predicted by typical stellar initial mass functions (IMFs). The identification of more galaxies with similar spectra may provide evidence for a top-heavy IMF at high redshift. [ABSTRACT FROM AUTHOR]

We present a numerical analysis investigating the reliability of Type Ia supernova (SN Ia) delay-time distributions recovered from individual host galaxy star formation histories. We utilize star formation histories of mock samples of galaxies generated from the IllustrisTNG simulation at two redshifts to recover delay-time distributions. The delay-time distributions are constructed through piecewise constants as opposed to typically employed parametric forms such as power laws or Gaussian or skew/lognormal functions. The SN Ia delay-time distributions are recovered through a Markov Chain Monte Carlo exploration of the likelihood space by comparing the expected SN Ia rate within each mock galaxy to the observed rate. We show that a reduced representative sample of nonhost galaxies is sufficient to reliably recover delay-time distributions while simultaneously reducing the computational load. We also highlight a potential systematic between recovered delay-time distributions and the mass-weighted ages of the underlying host galaxy stellar population. [ABSTRACT FROM AUTHOR]

We present an analysis of the galaxy merger rate in the redshift range |$4.0\lt z\lt 9.0$| (i.e. about 1.5 to 0.5 Gyr after the big bang) based on visually identified galaxy mergers from morphological parameter analysis. Our data set is based on high-resolution NIRCam JWST data (a combination of F 150 W and F 2000 W broad-band filters) in the low-to-moderate magnification (⁠|$\mu \lt 2$|⁠) regions of the Abell 2744 cluster field. From a parent set of 675 galaxies |$(M_{U}\in [-26.6,-17.9])$|⁠ , we identify 64 merger candidates from the Gini, |$M_{20}$| and asymmetry morphological parameters, leading to a merger fraction |$f_m=0.11\pm 0.04$|⁠. There is no evidence of redshift evolution of |$f_m$| even at the highest redshift considered, thus extending well into the epoch of reionization the constant trend seen previously at |$z\lesssim 6$|⁠. Furthermore, we investigate any potential redshift-dependent differences in the specific star formation rates between mergers and non-mergers. Our analysis reveals no significant correlation in this regard, with deviations in the studied redshift range typically falling within |$(1-1.5)\sigma$| from the null hypothesis that can be attributed to sample variance and measurement errors. Finally, we also demonstrate that the classification of a merging system is robust with respect to the observed (and equivalently rest frame) wavelength of the high-quality JWST broad-band images used. This preliminary study highlights the potential for progress in quantifying galaxy assembly through mergers during the epoch of reionization, with significant sample size growth expected from upcoming large JWST infrared imaging data sets. [ABSTRACT FROM AUTHOR]

Early-type dwarf galaxies constitute a prevalent population in the central regions of rich groups and clusters in the local Universe. These low-luminosity and low-mass stellar systems play a fundamental role in the assembly of the luminous galaxies observed today, according to the Lambda cold dark matter hierarchical theory. The origin of early-type dwarfs has been linked to the transformation of disc galaxies interacting with the intracluster medium, especially in dense environments. However, the existence of low-luminosity early-type galaxies in low-density environments presents a challenge to this scenario. This study presents a comprehensive photometric and spectroscopic analysis of the early-type dwarf galaxy CGCG014−074 using deep Gemini GMOS (Gemini Multi-Object Spectrograph) data, focusing on its peculiarities and evolutionary implications. CGCG014−074 exhibits distinct features, including a rotating inner disc, an extended stellar formation with a quiescent phase since about 2 Gyr ago, and the presence of boxy isophotes. From the kinematic analysis, we confirm CGCG014−074 as a nucleated early-type dwarf galaxy with embedded disc. The study of its stellar population parameters using different methods provides significant insights into the galaxy's evolutionary history. These results show an old and metal-poor nucleus (⁠|${\sim}9.3$| Gyr and |$\mathrm{[Z/H]}\sim -0.84$| dex), while the stellar disc is younger (⁠|${\sim}4.4$| Gyr) with a higher metallicity (⁠|$\mathrm{[Z/H]}\sim -0.40$| dex). These distinctive features collectively position CGCG014−074 as a likely building block galaxy that has evolved passively throughout its history. [ABSTRACT FROM AUTHOR]

We present an investigation of the L -band emission from known massive young stellar objects in the South African Radio Astronomy Observatory MeerKAT Galactic Plane Survey to search for non-thermal radio emitters in the sample. A total of 398 massive protostars, identified from the Red MSX Source survey, are located within the survey region. Among these, 162 fields that host the protostars are isolated from nearby bright H  ii regions, allowing for the study of any ionized jets present. Seventy-one of these fields have jets with five-sigma detections or higher, corresponding to a detection rate of 44 per cent. The MeerKAT fluxes of the detections, together with the upper limits of the non-detections and any other fluxes from previous observations, were used to estimate the spectral indices of the jets, and to search for the presence of non-thermal radiation. In cases where a source manifests as single in a given observation but is resolved into multiple components in observations of higher resolutions, the sum of the fluxes of the resolved components was used in estimating the indices. Any effects from missing flux in higher resolution observations were incorporated into the index uncertainties. The spectral indices of the sample show that at least 50 per cent of the jets emit non-thermal radiation. Additionally, the spectral energy distribution of some of the sources, as well as their radio luminosities exhibit evidence of non-thermal emission, especially in extended sources. [ABSTRACT FROM AUTHOR]

We use a complete sample of 211 nearby (⁠|$z< 0.08$|⁠), dwarf (10 |$^{8}$|  M |$_{\odot }$| < |$M_{\rm {\star }}$| < 10 |$^{9.5}$|  M |$_{\odot }$|⁠) galaxies in low-density environments, to study their structural properties: effective radii (⁠|$R_{\rm e }$|⁠), effective surface brightnesses (⁠|$\langle \mu \rangle _{\rm e}$|⁠), and colour gradients. We explore these properties as a function of stellar mass and the three principal dwarf morphological types identified in a companion paper – early-type galaxies (ETGs), late-type galaxies (LTGs), and featureless systems. The median |$R_{\rm e }$| of LTGs and featureless galaxies are factors of |$\sim$| 2 and |$\sim$| 1.2 larger than the ETGs. While the median |$\langle \mu \rangle _{\rm e}$| of the ETGs and LTGs is similar, the featureless class is |$\sim$| 1 mag arcsec |$^{-2}$| fainter. Although they have similar median |$R_{\rm e }$|⁠ , the featureless and ETG classes differ significantly in their median |$\langle \mu \rangle _{\rm e}$|⁠ , suggesting that their evolution is different and that the featureless galaxies are not a subset of the ETGs. While massive ETGs typically exhibit negative or flat colour gradients, dwarf ETGs generally show positive colour gradients (bluer centres). The growth of ETGs therefore changes from being 'outside-in' to 'inside-out' as we move from the dwarf to the massive regime. The colour gradients of dwarf and massive LTGs are, however, similar. Around 46 per cent of dwarf ETGs show prominent, visually identifiable blue cores which extend out to |$\sim$| 1.5 |$R_{\rm e}$|⁠. Finally, compared to their non-interacting counterparts, interacting dwarfs are larger, bluer at all radii and exhibit similar median |$\langle \mu \rangle _{\rm e}$|⁠ , indicating that interactions typically enhance star formation across the entire galaxy. [ABSTRACT FROM AUTHOR]

We present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range |$8.5< z< 15.5$| using a combination of several major Cycle-1 JWST imaging programmes – Public Release IMaging for Extragalactic Research, JWST Advanced Deep Extragalactic Survey, and Next Generation Deep Extragalactic Exploratory Public Survey. This multifield approach yields a total of |$\simeq 370$| arcmin2 of JWST /NIRCam imaging, reaching (5- |$\sigma$|⁠) depths of |$\simeq 30$| AB mag in the deepest regions. We select a sample of 2548 galaxies with a significant probability of lying at high redshift (⁠|$p(z> 8.5)> 0.05$|⁠) to undertake a statistical calculation of the UV LF. Our new measurements span |$\simeq 4$|  mag in UV luminosity at |$z=9-12.5$|⁠ , placing new constraints on both the shape and evolution of the LF at early times. Our measurements yield a new estimate of the early evolution of cosmic star-formation rate density (⁠|$\rho _{\rm {SFR}}$|⁠) confirming the gradual decline deduced from early JWST studies, at least out to |$z \simeq 12$|⁠. Finally we show that the observed early evolution of the galaxy UV LF (and |$\rho _{\rm {SFR}}$|⁠) can be reproduced in a |${\rm \Lambda }$| cold dark matter Universe, with no change in dust properties or star-formation efficiency required out to |$z \simeq 12$|⁠. Instead, a progressive trend towards younger stellar population ages can reproduce the observations, and the typical ages required at |$z \simeq$| 8, 9, 10, and 11 all converge on |$\simeq 380-330$|  Myr after the big bang, indicative of a rapid emergence of early galaxies at |$z \simeq 12 - 13$|⁠. This is consistent with the first indications of a steeper drop-off in |$\rho _{\rm {SFR}}$| we find beyond |$z \simeq 13$|⁠ , possibly reflecting the rapid evolution of the halo mass function at earlier times. [ABSTRACT FROM AUTHOR]

We use data from the JWST Public Release IMaging for Extragalactic Research survey to measure the size scaling relations of 1668 rest-frame UV-bright Lyman-break galaxies (LBGs) at |$z=3\!-\!5$| with stellar masses |$\mathrm{log}_{10}({\it M}_{\star}/{\rm M}_{\odot }) \gt 9$|⁠. The sample was selected from seeing-dominated ground-based data, presenting an unbiased sampling of the morphology and size distributions of luminous sources. We fit Sérsic profiles to eight NIRCam bands and also measure a non-parametric half-light radius. We find that the size distributions with both measurements are well-fit by a lognormal distribution at all redshifts, consistent with disc formation models where size is governed by host dark-matter halo angular momentum. We find a size–redshift evolution of |$R_{\rm e} = 3.51(1+z)^{-0.60\pm 0.22}$| kpc, in agreement with JWST studies. When considering the typical (modal) size over |$z=3\!-\!5$|⁠ , we find little evolution with bright LBGs remaining compact at |$R_{\rm e}\simeq 0.7{-}0.9$|  kpc. Simultaneously, we find evidence for a build-up of large (⁠|$R_{\rm e} \gt 2$|  kpc) galaxies by |$z=3$|⁠. We find some evidence for a negatively sloped size–mass relation at |$z=5$| when Sérsic profiles are used to fit the data in F200W. The intrinsic scatter in our size–mass relations increases at higher redshifts. Additionally, measurements probing the rest-UV (F200W) show larger intrinsic scatter than those probing the rest-optical (F356W). Finally, we leverage rest-UV and rest-optical photometry to show that discy galaxies are well established by |$z=5$|⁠ , but are beginning to undergo dissipative processes, such as mergers, by |$z=3$|⁠. The agreement of our size–mass and size–luminosity relations with simulations provides tentative evidence for centrally concentrated star formation at high redshift. [ABSTRACT FROM AUTHOR]

The mass assembly history (MAH) of dark matter haloes plays a crucial role in shaping the formation and evolution of galaxies. MAHs are used extensively in semi-analytic and empirical models of galaxy formation, yet current analytic methods to generate them are inaccurate and unable to capture their relationship with the halo internal structure and large-scale environment. This paper introduces florah (FLOw-based Recurrent model for Assembly Histories), a machine-learning framework for generating assembly histories of ensembles of dark matter haloes. We train florah on the assembly histories from the Gadget at Ultra-high Redshift with Extra Fine Time-steps and vsmdpl N -body simulations and demonstrate its ability to recover key properties such as the time evolution of mass and concentration. We obtain similar results for the galaxy stellar mass versus halo mass relation and its residuals when we run the Santa Cruz semi-analytic model on florah -generated assembly histories and halo formation histories extracted from an N -body simulation. We further show that florah also reproduces the dependence of clustering on properties other than mass (assembly bias), which is not captured by other analytic methods. By combining multiple networks trained on a suite of simulations with different redshift ranges and mass resolutions, we are able to construct accurate main progenitor branches with a wide dynamic mass range from |$z=0$| up to an ultra-high redshift |$z \approx 20$|⁠ , currently far beyond that of a single N -body simulation. florah is the first step towards a machine learning-based framework for planting full merger trees; this will enable the exploration of different galaxy formation scenarios with great computational efficiency at unprecedented accuracy. [ABSTRACT FROM AUTHOR]

We present the analysis of over 3000 red- Herschel sources (⁠|$S_{\mathrm{250\, \mu m}}\lt S_{\mathrm{350\, \mu m}}\lt S_{\mathrm{500\, \mu m} }$|⁠) using public data from the ALMA archive and the Herschel -ATLAS survey. This represents the largest sample of red- Herschel sources with interferometric follow-up observations to date. The high ALMA angular resolution and sensitivity (⁠|$\theta _{\rm FWHM}\sim$| 1 arcsec; |$\sigma _{1.3\mathrm{\, mm}}\sim 0.17$|  mJy beam |$^{-1}$|⁠) allow us to classify the sample into individual sources, multiple systems, and potential lenses and/or close mergers. Interestingly, even at this high angular resolution, 73 per cent of our detections are single systems, suggesting that most of these galaxies are isolated and/or post-merger galaxies. For the remaining detections, 20 per cent are classified as multiple systems, 5 per cent as lenses and/or mergers, and 2 per cent as low- z galaxies or active galactic nuclei. Combining the Herschel /SPIRE and ALMA photometry, these galaxies are found to be extreme and massive systems with a median star formation rate of |$\sim$| 1500  |$\mathrm{M_{\odot }\, yr^{-1}}$| and molecular gas mass of |$M_{\mathrm{gas}}\sim 10^{11}$|   |$\mathrm{M_{\odot }}$|⁠. The median redshift of individual sources is |$z\approx 2.8$|⁠ , while the likely lensed systems are at |$z\approx 3.3$|⁠ , with redshift distributions extending to |$z\sim 6$|⁠. Our results suggest a common star formation mode for extreme galaxies across cosmic time, likely triggered by close interactions or disc-instabilities, and with short depletion times consistent with the starburst-type population. Moreover, all galaxies with |$S_{\mathrm{1.3mm}}\ge 13$|  mJy are gravitationally amplified which, similar to the established |$S_{500\mathrm{ \, \mu m}}\gt 100$|  mJy threshold, can be used as a simple criterion to identify gravitationally lensed galaxies. [ABSTRACT FROM AUTHOR]

We investigate how the stellar rotational support changes as a function of spatially resolved stellar population age (⁠|$D_n4000$|⁠) and relative central stellar surface density (⁠|$\Delta \Sigma _1$|⁠) for MaNGA isolated/central disc galaxies. We find that the galaxy rotational support indicator |$\lambda _{R_\mathrm{e}}$| varies smoothly as a function of |$\Delta \Sigma _1$| and |$D_n4000$|⁠. |$D_n4000$| versus |$\Delta \Sigma _1$| follows a 'J-shape', with |$\lambda _{R_\mathrm{e}}$| contributing to the scatters. In this 'J-shaped' pattern rotational support increases with central |$D_n4000$| when |$\Delta \Sigma _1$| is low but decreases with |$\Delta \Sigma _1$| when |$\Delta \Sigma _1$| is high. Restricting attention to low- |$\Delta \Sigma _1$| (i.e. large-radius) galaxies, we suggest that the trend of increasing rotational support with |$D_n4000$| for these objects is produced by a mix of two different processes, a primary trend characterized by growth in |$\lambda _{R_\mathrm{e}}$| along with mass through gas accretion, on top of which disturbance episodes are overlaid, which reduce rotational support and trigger increased star formation. An additional finding is that star-forming galaxies with low |$\Delta \Sigma _1$| have relatively larger radii than galaxies with higher |$\Delta \Sigma _1$| at fixed stellar mass. Assuming that these relative radii rankings are preserved while galaxies are star forming then implies clear evolutionary paths in central |$D_n4000$| versus |$\Delta \Sigma _1$|⁠. The paper closes with comments on the implications that these paths have for the evolution of pseudo-bulges versus classical bulges. The utility of using |$\rm D_n4000$| – |$\Delta \Sigma _1$| to study |$\lambda _{R_\mathrm{e}}$| reinforces the notion that galaxy kinematics correlate both with structure and with stellar-population state, and indicates the importance of a multidimensional description for understanding bulge and galaxy evolution. [ABSTRACT FROM AUTHOR]

Magnetic fields are an energetically important component of star formation galaxies, but it is often difficult to measure their properties from observations. One of the complexities stems from the fact that the magnetic fields, especially in spiral galaxies, have a two-scale nature: a large-scale field, coherent over kpc scales, and a small-scale random field, with a scale of |${\lesssim} 100 \, {\rm pc}$|⁠. Moreover, it is known that the strength of small- and large-scale fields is comparable and this makes it even harder to find their imprints in radio polarization observations such as the Faraday rotation measure (RM), which is the integral over the path-length of the product of the thermal electron density and the parallel component of the magnetic field to the line of sight. Here, we propose and demonstrate the use of second-order structure functions of RM computed with multiple higher-order stencils as a powerful analysis to separate the small- and large-scale magnetic field components. In particular, we provide new methods and calibrations to compute the scale and the strength of the large-scale magnetic field in the presence of small-scale magnetic fluctuations. We then apply the method to find the scale of large-scale magnetic fields in the nearby galaxies M51 and NGC 6946, using archival data, and further discuss the need for computing the RM structure functions with higher-order stencils. With multiple modern radio polarization observatories and eventually the Square Kilometre Array, RM observations will significantly improve in quantity and quality, and the higher-order stencil structure function techniques developed here can be used to extract information about multiscale magnetic fields in galaxies. [ABSTRACT FROM AUTHOR]

The formation and evolution of supermassive black holes (SMBHs) remains an open question in the field of modern cosmology. The detection of nanohertz (n-Hz) gravitational waves via pulsar timing arrays (PTAs) in the form of individual events and the stochastic gravitational wave background (SGWB) offers a promising avenue for studying SMBH evolution across cosmic time, with SGWB signal being the immediately detectable signal with the currently accessible telescope sensitivities. By connecting the galaxy properties in the large scale (Gpc scale) cosmological simulation such as MICECAT with the small scale (⁠|$\sim$| Mpc scale) galaxy simulations from ROMULUS , we show that different scenarios of galaxy–SMBH evolution with redshift leads to a frequency-dependent spatial anisotropy in the SGWB signal. The presence of slow evolution of the SMBHs in the Universe leads to a pronounced blue anisotropic spectrum of the SGWB. In contrast, if SMBHs grow faster in the Universe in lighter galaxies, the frequency-dependent spatial anisotropy exhibits a more flattened anisotropic spectrum. This additional aspect of the SGWB signal on top of the monopole SGWB signal, can give insight on how the SMBHs form in the high-redshift Universe and its interplay with the galaxy formation from future measurements. [ABSTRACT FROM AUTHOR]

Fuzzy dark matter (FDM), comprised of ultralight (⁠|$m \sim 10^{-22}\,{\rm eV}$|⁠) boson particles, has received significant attention as a viable alternative to cold dark matter (CDM), as it approximates CDM on large scales (⁠|${\gtrsim}1$|  Mpc) while potentially resolving some of its small-scale problems via kiloparsec-scale quantum interference. However, the most basic FDM model, with one free parameter (the boson mass), is subject to a tension: small boson masses yield the desired cores of dwarf galaxies but underpredict structure in the Lyman-α forest, while large boson masses render FDM effectively identical to CDM. This Catch-22 problem may be alleviated by considering an axion-like particle with attractive particle self-interactions. We simulate an idealized FDM halo with self-interactions parametrized by an energy decay constant |$f \sim 10^{15}~\rm {GeV}$| related to the axion symmetry-breaking conjectured to solve the strong-CP problem in particle physics. We observe solitons, a hallmark of FDM, condensing within a broader halo envelope, and find that the density profile and soliton mass depend on self-interaction strength. We propose generalized formulae to extend those from previous works to include self-interactions. We also investigate a critical mass threshold predicted for strong interactions at which the soliton collapses into a compact, unresolved state. We find that the collapse happens quickly, and its effects are initially contained to the central region of the halo. [ABSTRACT FROM AUTHOR]

Submillimetre galaxies (SMGs) are some of the most extreme star-forming systems in the Universe, whose place in the framework of galaxy evolution is as yet uncertain. It has been hypothesized that SMGs are progenitors of local early-type galaxies, requiring that SMGs generally reside in galaxy cluster progenitors at high redshift. We test this hypothesis and explore SMG environments using a narrow-band VLT/HAWK-I+GRAAL study of H  |$\alpha$| and [O  iii ] emitters around an unbiased sample of three ALMA-identified and spectroscopically confirmed SMGs at |$z \sim 2.3$| and |$\sim 3.3$|⁠ , where these SMGs were selected solely on spectroscopic redshift. Comparing with blank-field observations at similar epochs, we find that one of the three SMGs lies in an overdensity of emission-line sources on the |$\sim 4$| Mpc scale of the HAWK-I field of view, with overdensity parameter |$\delta _{g} = 2.6^{+1.4}_{-1.2}$|⁠. A second SMG is significantly overdense only on |$\lesssim 1.6$| Mpc scales and the final SMG is consistent with residing in a blank field environment. The total masses of the two overdensities are estimated to be |$\log (M_{h}/{\rm M}_{\odot }) =$| 12.1–14.4, leading to present-day masses of |$\log (M_{h,z=0}/{\rm M}_{\odot }) =$| 12.9–15.9. These results imply that SMGs occupy a range of environments, from overdense protoclusters or protogroups to the blank field, suggesting that while some SMGs are strong candidates for the progenitors of massive elliptical galaxies in clusters, this may not be their only possible evolutionary pathway. [ABSTRACT FROM AUTHOR]

Galaxy–galaxy strong gravitational lensing (GGSL) is a powerful probe for the formation and evolution of galaxies and cosmology, while the sample size of GGSLs leads to considerable uncertainties and potential bias. The China Space Station Telescope (CSST, to be launched in late 2026) will conduct observations across 17 500 square degrees of the sky, capturing images in the |$ugriz$| bands with a spatial resolution comparable to that of the Hubble Space Telescope. We ran a set of Monte Carlo simulations to predict that the CSST's wide-field survey will observe |$\sim$| 160 000 galaxy–galaxy strong lenses over its lifespan, increasing the number of existing galaxy–galaxy strong lens samples by three orders of magnitude. This is comparable to the capabilities of the |$\it Euclid$| telescope but with the added benefit of additional colour information. Specifically, the CSST can detect strong lenses with Einstein radii about |$0.64\pm 0.42 ^{\prime \prime }$|⁠ , corresponding to the velocity dispersions of |$217.19 \pm 50.55 \, \text{km/s}$|⁠. These lenses exhibit a median magnification of |$\sim$| 5. The apparent magnitude of the unlensed sources in the g band is |$25.87 \pm 1.19$|⁠. The signal-to-noise ratio of the lensed images covers a range of |${\sim} 20$| to |${\sim} 1000$|⁠ , allowing us to determine the Einstein radius with an accuracy ranging from |${\sim} 1~{{\ \rm per\ cent}}$| to |${\sim} 0.1~{{\ \rm per\ cent}}$|⁠ , ignoring various modelling systematics. Our estimates indicate that CSST can observe rare systems like double source-plane and spiral galaxy lenses. The above selection functions of the CSST strong lensing observation help optimize the strategy of finding and modelling GGSLs. [ABSTRACT FROM AUTHOR]

Magnetic fields play an important role in shaping and regulating star formation in molecular clouds. Here, we present one of the first studies examining the relative orientations between magnetic (B) fields and the dust emission, gas column density, and velocity centroid gradients on the 0.02 pc (core) scales, using the BISTRO and VLA+GBT observations of the NGC 1333 star-forming clump. We quantified these relative orientations using the Project Rayleigh Statistic (PRS) and found preferential global parallel alignment between the B field and dust emission gradients, consistent with large-scale studies with Planck. No preferential global alignments, however, are found between the B field and velocity gradients. Local PRS calculated for subregions defined by either dust emission or velocity coherence further revealed that the B field does not preferentially align with dust emission gradients in most emission-defined subregions, except in the warmest ones. The velocity-coherent structures, on the other hand, also showed no preferred B field alignments with velocity gradients, except for one potentially bubble-compressed region. Interestingly, the velocity gradient magnitude in NGC 1333 ubiquitously features prominent ripple-like structures that are indicative of magnetohydrodynamic (MHD) waves. Finally, we found B field alignments with the emission gradients to correlate with dust temperature and anticorrelate with column density, velocity dispersion, and velocity gradient magnitude. The latter two anticorrelations suggest that alignments between gas structures and B fields can be perturbed by physical processes that elevate velocity dispersion and velocity gradients, such as infall, accretions, and MHD waves. [ABSTRACT FROM AUTHOR]

JWST has revealed a large population of accreting black holes (BHs) in the early Universe. Recent work has shown that even after accounting for possible systematic biases, the high- z |$M_*{\!-\!}M_{\rm \rm bh}$| relation can be above the local scaling relation by |$\gt 3\sigma$|⁠. To understand the implications of these overmassive high- z BHs, we study the BH growth at |$z\sim 4{\!-\!}7$| using the |$[18~\mathrm{Mpc}]^3$| BRAHMA cosmological simulations with systematic variations of heavy seed models that emulate direct collapse black hole (DCBH) formation. In our least restrictive seed model, we place |$\sim 10^5~{\rm M}_{\odot }$| seeds in haloes with sufficient dense and metal-poor gas. To model conditions for direct collapse, we impose additional criteria based on a minimum Lyman Werner flux (LW flux |$=10~J_{21}$|⁠), maximum gas spin, and an environmental richness criterion. The high- z BH growth in our simulations is merger dominated, with a relatively small contribution from gas accretion. The simulation that includes all the above seeding criteria fails to reproduce an overmassive high- z |$M_*{\!-\!}M_{\rm bh}$| relation consistent with observations (by factor of |$\sim 10$| at |$z\sim 4$|⁠). However, more optimistic models that exclude the spin and environment based criteria are able to reproduce the observed relations if we assume |$\lesssim 750~\mathrm{Myr}$| delay times between host galaxy mergers and subsequent BH mergers. Overall, our results suggest that current JWST observations may be explained with heavy seeding channels if their formation is more efficient than currently assumed DCBH conditions. Alternatively, we may need higher initial seed masses, additional contributions from lighter seeds to BH mergers, and / or more efficient modes for BH accretion. [ABSTRACT FROM AUTHOR]

Strong gravitational lensing provides a purely gravitational means to infer properties of dark matter haloes and thereby constrain the particle nature of dark matter. Strong lenses sometimes appear as four lensed images of a background quasar accompanied by spatially resolved emission from the quasar host galaxy encircling the main deflector (lensed arcs). We present methodology to simultaneously reconstruct lensed arcs and relative image magnifications (flux ratios) in the presence of full populations of subhaloes and line-of-sight haloes. To this end, we develop a new approach for multiplane ray tracing that accelerates lens mass and source light reconstruction by factors of |$\sim\!\! 100\!\!-\!\!1000$|⁠. Using simulated data, we show that simultaneous reconstruction of lensed arcs and flux ratios isolates small-scale perturbations to flux ratios by dark matter substructure from uncertainties associated with the main deflector mass profile on larger angular scales. Relative to analyses that use only image positions and flux ratios to constrain the lens model, incorporating arcs strengthens likelihood ratios penalizing warm dark matter with a suppression scale |$m_{\rm {hm}} / {\rm M}_{\odot }$| in the ranges of |$\left[10^7 \!\!-\!\! 10^{7.5}\right]$|⁠ , |$\left[10^{7.5} \!\!-\!\! 10^{8}\right]$|⁠ , |$\left[10^8 \!\!-\!\! 10^{8.5}\right]$|⁠ , and |$\left[10^{8.5} \!\!-\!\! 10^{9}\right]$| by factors of 1.3, 2.5, 5.6, and 13.1, respectively, for a cold dark matter ground truth. The 95 per cent exclusion limit improves by 0.5 dex in |$\log _{10} m_{\rm {hm}}$|⁠. The enhanced sensitivity to low-mass haloes enabled by these methods pushes the observational frontier of substructure lensing to the threshold of galaxy formation, enabling stringent tests of any theory that alters the properties of dark matter haloes. [ABSTRACT FROM AUTHOR]

We spectroscopically confirm the M UV = −20.5 mag galaxy GHZ2/GLASS-z12 to be at redshift z = 12.34. The source was selected via NIRCam photometry in GLASS-JWST Early Release Science data, providing the first evidence of a surprising abundance of bright galaxies at z ≳ 10. The NIRSpec PRISM spectrum shows detections of N iv, C iv, He ii, O iii, C iii, O ii, and Ne iii lines and the first detection at high redshift of the O iii Bowen fluorescence line at 3133 Å rest frame. The prominent C iv line with rest-frame equivalent width (EW) ≈ 46 Å puts GHZ2 in the category of extreme C iv emitters. GHZ2 displays UV lines with EWs that are only found in active galactic nuclei (AGNs) or composite objects at low/intermediate redshifts. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne iv ]/[N iv ] ratio favoring a stellar origin of the ionizing photons. We discuss a possible scenario in which the high ionizing output is due to low-metallicity stars forming in a dense environment. We estimate a metallicity ≲0.1 Z / Z ⊙, a high ionization parameter log U > −2, a N/O abundance 4–5 times the solar value, and a subsolar C/O ratio similar to the recently discovered class of nitrogen-enhanced objects. Considering its abundance patterns and the high stellar mass density (104 M ⊙ pc−2), GHZ2 is an ideal formation site for the progenitors of today's globular clusters. The remarkable brightness of GHZ2 makes it a "Rosetta stone" for understanding the physics of galaxy formation within just 360 Myr after the Big Bang. [ABSTRACT FROM AUTHOR]

Spatial, kinematic, and orbital properties, along with ages and chemical compositions of the thin disc, thick disc, and various stellar substructures in the halo, are studied based on data from the LAMOST and Gaia surveys. The star formation in the Galactic thin and thick disc, with peak metallicities of − 0.20 and − 0.45 dex, is found to have peaked about 5.5 and 12.5 Gyr ago, respectively. The thin disc is also found to have experienced an initial star formation burst about 12.5 Gyr ago. The pro-grade population Splash and hot-disc (HD), with peak metallicity of about − 0.60 and − 0.43, are found to be about 13.03 and 12.21 Gyr old, respectively, with peak eccentricity of 0.70 and 0.35, are understood to be of in situ origin. The Gaia-Enceladus/Sausage (GE/S), Thamnos and Sequoia, with peak metallicity of about − 1.31, − 1.36, and − 1.56, are found to be about 11.66, 12.89, and 12.18 Gyr, respectively, and are understood to be remnants of dwarf galaxies merged with the Milky Way. The HD, Splash, and Thamnos have experienced chemical evolution similar to the thick disc, while GE/S, Sequoia, and Helmi stream have experienced distinct chemical enrichment of iron and α -process elements. [ABSTRACT FROM AUTHOR]

Observational evidence consistently shows that the universe is spatially flat and undergoes Lorentzian time dilation as a function of redshift. In combination, such discoveries suggest that a Minkowskian description of cosmology might be technically viable. The thermal evolution that transpires in a conformal spacetime is herein derived. The description is constrained by the energy conservation of a unified cosmic fluid. The resulting model puts forth a Lorentzian correction for the temperature of the CMB as a function of redshift, which improves current data fitting without adding any free parameter. Furthermore, it sheds light upon the early galaxy formation problem: our model predicts up to 0.86 Gyr older objects within the first two billion years of the structure evolution in the universe. [ABSTRACT FROM AUTHOR]

This observational study investigates the effects of interaction on the kinematics and chemical abundance of the peculiar galaxy ESO 287-IG50, which may be a polar ring galaxy in an ongoing formation process. The study utilized BVRI broad band imagery and longslit spectroscopy in the wavelength range of 4240-8700 Å. The STARLIGHT stellar population synthesis code was used to analyze the data, and standard diagnostic diagrams were employed to classify the main ionizing source of selected emission-line regions. Image analysis using filtering techniques revealed an inner ring with perpendicular structures at both ends, which could be the inner part of a bisymmetric spiral structure. Photometric analysis showed dusty filaments crossing the central structure, which was identified as the redder region of the galaxy, dominated by a non-negligible amount of dust. Shell-like structures, which could be remnants of a galaxy merging process, were also found. Image analysis through filtering revealed what appears to be an inner ring, with perpendicular structures at both ends, which could be the inner part of a bisymmetric spiral structure. Photometric analysis shows dusty filaments crossing the central structure. This region would be dominated by a non negligible amount of dust, identified as the redder region of the galaxy. A heliocentric radial velocity of 17 689±45 km s−1 was measured, and the velocity profile exhibited a clear rotational behavior, with peak velocities of 110 km s−1 to the SW and 80 km s−1 to the other side. The analysis of the nuclear region using the STARLIGHT code revealed a stellar population consisting of approximately one-third young stars and two-thirds old stars. The predominance of an aged stellar population, a distinctive feature in galaxies undergoing interaction processes, can be attributed to the prolonged evolutionary period of this galaxy, as evidenced by the shell structures we identified as indicators of this interaction process. The [NII] λ 6584Å/H α ratio suggests that ESO 287-IG50 may be an AGN due to the excess of Nitrogen relative to Hydrogen in the residual spectrum, a feature not yet reported in the literature. Studying the line ratios and EW(H α ), we notice that this galaxy exhibits a peculiar AGN, with a non-stellar origin ionization mechanism. [ABSTRACT FROM AUTHOR]

Primordial axion stars, hypothetical stars formed from axions, could play an essential role in forming galaxy halos. These stars could have originated in the early universe shortly after the Big Bang. We show that the ultralight axions forming primordial stars can act as the initial seeds for galaxy halos. [ABSTRACT FROM AUTHOR]

This is a golden age for galaxy formation: Existing and especially new telescopes are providing observations that challenge and illuminate rapidly improving theory and simulations. This review describes the formation of the cosmic web and the structure of the dark matter halos that provide the scaffolding of the Universe. It then summarizes how empirical models, semianalytic models, and hydrodynamic simulations attempt to account for key properties of the galaxy population, including the main sequence of star-forming galaxies, the inefficiency of star formation, the shape evolution and color bimodality of galaxies, and the phenomena that cause galaxies to quench their star formation. It concludes with a summary of observations that have challenged the cosmological constant cold dark matter (ΛCDM) paradigm of galaxy formation—including the Hubble and S8 tensions, bright galaxies in the early Universe, an extragalactic background light mystery, missing satellite galaxies, the diversity of dwarf galaxies, the cusp–core problem, the too-big-to-fail problem, stellar clumps, planes of satellite galaxies, and galaxies without dark matter—and solutions that have been proposed. [ABSTRACT FROM AUTHOR]

We present novel insights into the interplay between tidal forces and star formation in interacting galaxies before their first pericentre passage. We investigate seven close pair galaxies devoid of visible tidal disturbances, such as tails, bridges, and shells. Using integral field spectroscopy data of extended Calar Alto Legacy Integral Field Area, we unveil a previously unreported phenomenon: H  |$\alpha$| emission, a proxy for recent star formation, exhibits a significant enhancement in regions facing the companion galaxy, reaching up to 1.9 times higher flux compared to opposite directions. Notably, fainter companions within pairs display a more pronounced one-sided H  |$\alpha$| excess, exceeding the typical range observed in isolated galaxies with 2 |$\sigma$| confidence level. Furthermore, the observed H  |$\alpha$| excess in fainter companion galaxies exhibits a heightened prominence at the outer galactic regions. These findings suggest that tidal forces generated before the first pericentre passage exert a stronger influence on fainter galaxies due to their shallower potential wells by their brighter companions. This unveils a more intricate interplay between gravitational interactions and star formation history within interacting galaxies than previously understood, highlighting the need further to explore the early stages of interaction in galaxy evolution. [ABSTRACT FROM AUTHOR]

We use the Phoenix simulations to study the mass assembly history and internal structures of cluster dark matter haloes (⁠|$M_{200} \gtrsim 5\times 10^{14} h^{-1}{\rm M}_\odot$|⁠). We confirm that cluster haloes grow inside-out, similar to galactic haloes. Major merger events dominate the growth of the internal region and minor mergers/diffuse accretion shape the outskirts. However, compared to galactic haloes, cluster haloes tend to have a younger and more actively evolving inner region. On average, the majority of mass (⁠|$\gtrsim 80$| per cent) in the inner region (⁠|$R\lt 0.1 r_{200}$|⁠) of Phoenix haloes is accreted after |$z = 3$|⁠ , while for galactic haloes, most mass in the central region has already been accreted before |$z=6$|⁠. The density profiles of cluster haloes are less stable than those of galactic haloes over different radii. The enclosed mass within 50 or 150 kpc of all Phoenix haloes evolves substantially in the past |${\sim } 7$|  Gyr, while galactic haloes remained stable during the same period. We suggest that the relatively younger and more active state explains the various observations of cluster haloes, especially in central regions. [ABSTRACT FROM AUTHOR]

The analysis of the cosmic microwave background data acquired by the Atacama Cosmology Telescope and the large-scale (⁠|$\ell \lesssim 1300$|⁠) Planck Telescope show a preference for the early dark energy (EDE) theory, which was set to alleviate the Hubble tension of the |$\Lambda$| cold dark matter (⁠|$\Lambda$| CDM) model by decreasing the sound horizon |$r_{s}$|⁠ , and gives |$H_{0} \approx 72$| km s |$^{-1}$| Mpc |$^{-1}$|⁠. However, the EDE model is commonly questioned for exacerbating the |$\sigma _8$| tension on top of the |$\Lambda$| CDM model, and its lack of preference from the late-time matter power spectrum observations, e.g. Baryon Oscillation Spectroscopic Survey. In light of the current obscurities, we inspect if the high redshift galaxy abundance, i.e. stellar mass function/density and luminosity function, can independently probe the EDE model. Our result shows that, compared to |$\Lambda$| CDM, the EDE model prediction at |$z\gt 10$| displays better consistency with the unexpectedly high results observed by the JWST. At lower redshift, the EDE model only fits the most luminous/massive end, with the majority of the data presenting better consistency with |$\Lambda$| CDM, implying that adding an extra luminosity/mass-sensitive suppression mechanism of the galaxy formation is required for EDE to explain all data around |$z\sim 7-10$|⁠. [ABSTRACT FROM AUTHOR]

Analyses of cosmic shear typically condense weak lensing information over a range of scales to a single cosmological parameter, |$S_8$|⁠. This paper presents a method to extract more information from Stage IV cosmic shear measurements by directly reconstructing the matter power spectrum from linear to non-linear scales. We demonstrate that cosmic shear surveys will be sensitive to the shape of the matter power spectrum on non-linear scales. We show that it should be possible to distinguish between different models of baryonic feedback and we investigate the impact of intrinsic alignments and observational systematics on forecasted constraints. In addition to providing important information on galaxy formation, power spectrum reconstruction should provide a definitive answer to the question of whether weak lensing measurements of |$S_8$| on linear scales are consistent with the Planck Lambda cold dark matter cosmology. In addition, power spectrum reconstruction may lead to new discoveries on the composition of the dark sector. [ABSTRACT FROM AUTHOR]

Employing the TNG100 run of the IllustrisTNG project, we characterize the environment of low surface brightness galaxies (LSBGs) across varying scales, from their associated dark matter haloes to their distribution within the broader cosmic structure. We find no significant differences in the halo concentration index |$c_{200}$| between LSBGs and their high surface brightness galaxy (HSBG) counterparts, with LSBGs residing in haloes with higher spin parameter |$\lambda$| and slightly more spherical shapes than HSBGs. LSBGs show a stronger alignment between the dark and stellar angular momentum vectors than their high surface brightness counterparts. The relative abundance of LSBGs within groups and clusters displays a central deficit, hinting at potential destruction upon reaching these core regions. Studying the density field, we find a preference for rotation-dominated LSBGs to reside in low-density environments, while dispersion-dominated LSBGs thrive in high-density regions where galaxy interactions govern their evolution, an observation corroborated by our analysis of the two-point correlation function |$\xi (r)$|⁠. Our examination of the cosmic web reveals no significant differences in the distance to the closest large-scale structure, barring a few exceptions. This suggests a limited impact of large-scale spatial distribution on mechanisms driving LSBG evolution. All together, we conclude that the halo vicinity and local environment at the scale of galaxy clusters, where mechanisms such as galaxy mergers and tidal stripping, as well as stellar and gas accretion take place, is the most likely environment that favour the emergence of LSBGs with different morphologies, mostly driven by the presence or absence of important local interaction phenomena. [ABSTRACT FROM AUTHOR]

The 21-cm spectral line widths, |$w_{50}$|⁠ , of galaxies are an approximate tracer of their dynamical masses, such that the dark matter halo mass function is imprinted in the number density of galaxies as a function of |$w_{50}$|⁠. Correcting observed number counts for survey incompleteness at the level of accuracy needed to place competitive constraints on warm dark matter (WDM) cosmological models is very challenging, but forward-modelling the results of cosmological hydrodynamical galaxy formation simulations into observational data space is more straightforward. We take this approach to make predictions for an ALFALFA-like survey from simulations using the EAGLE galaxy formation model in both cold (CDM) and WDM cosmogonies. We find that for WDM cosmogonies more galaxies are detected at the low- |$w_{50}$| end of the 21-cm velocity width function than in the CDM cosmogony, contrary to what might naïvely be expected from the suppression of power on small scales in such models. This is because low-mass galaxies form later and retain more gas in WDM cosmogonies (with EAGLE). While some shortcomings in the treatment of cold gas in the EAGLE model preclude placing definitive constraints on WDM scenarios, our analysis illustrates that near-future simulations with more accurate modelling of cold gas will likely make strong constraints possible, especially in conjunction with new 21-cm surveys such as WALLABY. [ABSTRACT FROM AUTHOR]