Star Formation Research Articles

Radial X-ray profiles of simulated galaxies. Contributions from hot gas and X-ray binaries

Theoretical models of structure formation predict the presence of a hot gaseous atmosphere around galaxies. While this hot circumgalactic medium (CGM) has been observationally confirmed through UV absorption lines, the detection of its direct X-ray emission remains scarce. Recent results from the eROSITA collaboration have claimed the detection of the CGM out to the virial radius for a stacked sample of Milky Way-mass galaxies. We investigate theoretical predictions of the intrinsic CGM X-ray surface brightness (SB) using simulated galaxies and connect them to their global properties, such as the gas temperature, hot gas fraction, and stellar mass. We selected a sample of central galaxies from the ultra-high-resolution cosmological volume ($48 cMpc $) of the Magneticum Pathfinder set of hydrodynamical cosmological simulations. We classified them as star-forming (SF) or quiescent (QU) based on their specific star formation rate (SFR). For each galaxy, we generated X-ray mock data using the X-ray photon simulator from which we obtained SB profiles out to the virial radius for different X-ray emitting components; namely, gas, active galactic nuclei (AGNs), and X-ray binaries (XRBs). We fit a β-profile to the gas component of each galaxy and observed trends between its slope and global quantities of the simulated galaxy. We found marginal differences among the average total SB profile in SF and QU galaxies beyond r>0.05 The relative contribution from hot gas exceeds $70%$ and is non-zero (lesssim 10%) for XRBs in both galaxy types. At small radii (r<0.05 XRBs dominate the SB profile over the hot gas for QU galaxies. We found positive correlations between the galaxies' global properties and the normalization of their SB profiles. The fitted β-profile slope is correlated with the total gas luminosity, which, in turn, shows strong connections to the current accretion rate of the central supermassive black hole (SMBH). We found the halo scaling relations to be consistent with the literature.

Predicting the detectability of sulphur-bearing molecules in the solid phase with simulated spectra of JWST instruments

To date, gas phase observations of sulphur in dense interstellar environments have only constrained the molecular carriers of ∼ 1 % of its predicted cosmic abundance. An additional ∼ 5 % is known to be locked up in molecular solids in dense clouds, leaving the main reservoir of depleted sulphur in the solid phase yet to be identified. Overall, OCS is the only S-bearing molecule unambiguously detected in interstellar ices thus far with infrared telescopes, although an absorption feature of SO_2 has been plausibly identified at 7.5 μm. The spectral resolution and sensitivity of the James Webb Space Telescope (JWST) could make a substantial difference in detecting part of this missing sulphur. The wavelength coverage of the JWST includes vibrational absorption features of the S-carriers H_2S, OCS, SO_2, CS_2, SO, CS, and S_8 are found. The aim of this study is to determine whether these molecules may be viable candidates for detection. We carried out new laboratory measurements of the IR absorption spectra of CS_2 and S_8 to update the IR band strength of the most intense CS_2 absorption feature at 6.8 μm, as well as to determine that of S_8 at 20.3 μm for the first time. These data, along with values previously reported in the literature for H_2S, OCS, and SO_2, allow us to evaluate which S-bearing species could be potentially detected with JWST in interstellar ices. Taking the literature abundances of the major ice species determined by previous IR observations towards starless cores, low-mass young stellar objects (LYSOs) and massive young stellar objects (MYSOs), we generated simulated IR spectra using the characteristics of the instruments on the JWST. Thus, we have been able to establish a case study for three stages of the star formation process. These spectra were simulated using a tool that produces synthetic ice spectra, with the aim of studying the feasibility of detecting S-bearing species with the JWST by artificially adding S-bearing molecules to the simulated spectra. We conclude that the detection of S-bearing molecules remains challenging due to a variety of parameters; principally, the overlap of absorption features with those of other species and the mixing of molecular species in the ice impacting the profile and central position of the targeted bands. Despite these obstacles, the detection of H_2S in dense clouds -- and potentially SO_2 in LYSOs and MYSOs -- should be possible in regions with favourable physical and chemical conditions, but not necessarily in the same region. In contrast, the large allotrope S_8 would remain undetected even in the unrealistic case that all the available sulphur atoms were involved in its formation. Although the sensitivity of JWST is insufficient to determine the sulphur budget in the solid state, the detection of (or setting of significant upper limits on the abundance of ) an additional icy sulphur compound (H_2S, SO_2) would enable us to validate a state-of-the-art approach in our knowledge of sulphur chemistry, offering a unique opportunity to make comparisons against future developments.

COSMOS-Web: Stellar mass assembly in relation to dark matter halos across 0.2<z<12 of cosmic history

We study the stellar mass assembly of galaxies via the stellar mass function (SMF) and the coevolution with dark matter halos via abundance matching in the largest redshift range to date, $0.2<z<12$. We used the $0.53 deg ^2$ imaged by JWST from the COSMOS-Web survey, in combination with ancillary imaging in over 30 photometric bands, to select highly complete samples (down to log$ ⋆ /M_ ⊙ = 7.5-8.8$) in 15 redshift bins. Our results show that the normalization of the SMF monotonically decreases from z=0.2 to z=12 with strong mass-dependent evolution. At z>5, we find increased abundances of massive (log$ ⋆ /M_ ⊙ >10.5$) systems compared to predictions from semi-analytical models and hydrodynamical simulations. These findings challenge traditional galaxy formation models by implying integrated star formation efficiencies (SFEs) of ε_ ⋆ ≡ M_ ⋆ b M_ halo ≳ 0.5. We find a flattening of the SMF at the high-mass end that is better described by a double power law at z>5.5, after correcting for the Eddington bias. At z 5.5, it transitions to a Schechter law, which coincides with the emergence of the first massive quiescent galaxies in the Universe, indicating that physical mechanisms that suppress galaxy growth start to take place at z∼5.5 on a global scale. By integrating the SMF, we trace the cosmic stellar mass density and infer the star formation rate density, which at z>7.5 agrees remarkably with recent JWST UV luminosity function-derived estimates. This agreement solidifies the emerging picture of rapid galaxy formation leading to increased abundances of bright and massive galaxies in the first ∼ 0.7 Gyrs. However, at z 3.5, we find significant tension (∼ 0.3 dex) with the cosmic star formation (SF) history from instantaneous SF measures, the causes of which remain poorly understood. We infer the stellar-to-halo mass relation (SHMR) and the SFE from abundance matching out to z=12, finding a non-monotonic evolution. The SFE has the characteristic strong dependence with mass in the range of $0.02 - 0.2$, and mildly decreases at the low-mass end out to z∼3.5. At z∼3.5, there is an upturn and the SFE increases sharply from ∼ 0.1 to approach a high SFE of $0.8-1$ by z∼ 10 for h /M_ ⊙ )≈11.5$, albeit with large uncertainties. Finally, we use the SHMR to track the SFE and stellar mass growth throughout the halo history and find that they do not grow at the same rate -- from the earliest times up until z∼3.5 the halo growth rate outpaces galaxy assembly, but at z>3.5 halo growth stagnates and accumulated gas reservoirs keep the SF going and galaxies outpace halos.

The DiskMass Survey. XI. Disk Geometries and Star Formation Surface Densities from Ionized Gas Kinematics and Line Intensities for the Full Hα Sample

The DiskMass Survey. XI. Disk Geometries and Star Formation Surface Densities from Ionized Gas Kinematics and Line Intensities for the Full Hα Sample

Simulating High-redshift Galaxies: Enhancing UV Luminosity with Star Formation Efficiency and a Top-heavy IMF

Simulating High-redshift Galaxies: Enhancing UV Luminosity with Star Formation Efficiency and a Top-heavy IMF

A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): Spectroscopically Complete Census of Obscured Cosmic Star Formation Rate Density at z = 4–6

A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): Spectroscopically Complete Census of Obscured Cosmic Star Formation Rate Density at z = 4–6

Unveiling the kinematics of a central region in the triple-AGN host NGC 7733-7734 interacting group

We present a detailed study of the interacting triple active galactic nuclear system, NGC 7733-34, focusing on stellar kinematics, ionised gas characteristics, and star formation within the central region and stellar bars of both galaxies. We performed a comprehensive analysis using archival data from MUSE, HST/ACS, and DECaLS, complemented with observations from UVIT and IRSF. We identified a disc-like bulge in both NGC 7733 and NGC 7734 through a 2D decomposition. A central nuclear structure, with a semi-major axis of ∼1.113 kpc, was detected in NGC 7733 via a photometric and kinematic analysis, confirmed by the strong anti-correlation between V/σ and h_3, indicative of circular orbits in the centre. NGC 7734 lacks a distinct nuclear structure. The presence of a disc-like bulge results in an anti-correlation between V/σ and h_3, along with diffuse light. However, it does show higher central velocity dispersion, possibly attributed to an interaction with a smaller clump, which is likely a fourth galaxy within the system. Both galaxies demonstrate ongoing star formation, evidenced by FUV and Hα observations. NGC 7734 shows recent star formation along its bar, while NGC 7733 experiences bar quenching. The star formation rate (SFR) analysis of NGC 7734 reveals that the bar region's SFR dominates the galaxy's overall SFR. Conversely, in NGC 7733, the lack of star formation along the bar and the presence of a Seyfert 2 active galactic nucleus (AGN) at the galaxy centre suggest the possibility of link among both. However, this would not affect the galaxy's overall star formation. Our findings provide valuable insights into the stellar and gas kinematics, star formation processes, and AGN feedback mechanisms in interacting galaxies hosting stellar bars.

The Arizona Molecular ISM Survey with the SMT: Variations in the CO(2–1)/CO(1–0) Line Ratio across the Galaxy Population

Abstract The J = 1 → 0 spectral line of carbon monoxide (CO(1–0)) is the canonical tracer of molecular gas. However, CO(2–1) is frequently used in its place, following the assumption that the higher-energy line can be used to infer the CO(1–0) luminosity and molecular gas mass. The use of CO(2–1) depends on a knowledge of the ratio between CO(2–1) and CO(1–0) luminosities, r 21. Here, we present galaxy-integrated r 21 measurements for 122 galaxies spanning stellar masses from 109 to 1011.5 M ⊙ and star formation rates (SFRs) from 0.08 to 35 M ⊙ yr−1. We find strong trends between r 21 and SFR, SFR surface density, star formation efficiency, and distance from the star formation main sequence (SFMS). We show that the assumption of a constant r 21 can introduce biases into the molecular gas trends in galaxy population studies and demonstrate how this affects the recovery of important galaxy scaling relations, including the Kennicutt–Schmidt law and the relation between SFMS offset and star formation efficiency. We provide a prescription that accounts for variations in r 21 as a function of SFR and can be used to convert between CO(2–1) and CO(1–0) when only one line is available. Our prescription matches variations in r 21 for both AMISS and literature samples and can be used to derive more accurate gas masses from CO(2–1) observations.

The role of dry mergers in shaping the scaling relations of galaxies

In the context of the hierarchical formation of galaxies, we investigated the role played by mergers in shaping the scaling relations of galaxies, that is the projections of their fundamental plane onto the and planes. To this end, based on the scalar virial theorem, we developed a simple theory of multiple dry mergers to read both the large-scale simulations and the companion scaling relations. The aim was to compare the results of this approach with the observational data and with two of the most recent and detailed numerical cosmo-hydro-dynamical simulations: Illustris-TNG and EAGLE (Evolution and Assembly of GaLaxies and their Environments). We derived these scaling relations for the galaxies of the Mapping Nearby Galaxies at APO (MaNGA) and Wide-field Imaging of Nearby Galaxy-Clusters Survey (WINGS) databases and compared them with the observational data, the numerical simulations, and the results of our simple theory of dry mergers. The multiple dry merging mechanism is able to explain all the main characteristics of the observed scaling relations of galaxies, such as slopes, scatters, curvatures, and zones of exclusion. The distribution of galaxies in these planes is continuously changing across time because of the merging activity and other physical processes, such as star formation, quenching, and energy feedback. The simple merger theory presented here yields the correct distribution of galaxies in the main scaling relations at all cosmic epochs. The precision is comparable with that obtained by the modern cosmo-hydro-dynamical simulations, with the advantage of providing a rapid exploratory response on the consequences engendered by different physical effects.

Exploring the Evolution of a Dwarf Spheroidal Galaxy with SPH Simulations. II. AGN Feedback

Abstract We investigate active galactic nucleus (AGN) feedback from an intermediate-mass black hole at the center of a dwarf spheroidal galaxy, by performing isolated galaxy simulations using a modified version of the GADGET-3 code. We consider Leo II (PGC 34176) in the Local Group as our simulation reference model. Beginning with black hole seeds ranging from 103−106 M ⊙, our simulations focus on comparing stellar/SN-only feedback with AGN+stellar/SN feedback over 13.7 Gyr of galactic evolution. Our results indicate that a low-mass AGN in a dwarf galaxy influences the star formation history under specific physical conditions. While AGN feedback is generally negative on star formation, instances of positive feedback were also identified. Despite measurable effects on the evolution of the dwarf host galaxy, black hole seeds exhibited only marginal growth. We tested several physical scenarios as modified models in our simulations, primarily concerning the dynamics of the central black holes, which may wander within dwarf galaxies rather than being centrally located. However, none of these adjustments significantly impacted the growth of the black hole seeds. This suggests that intermediate-mass black holes may struggle to achieve higher masses in isolated environments, with mergers and interactions likely playing crucial roles in their growth. Nevertheless, AGN feedback exhibited nonnegligible effects in our simulated dwarf spheroidal galaxies, despite the assumed dominant role of stellar feedback in the low-mass regime.

A Multiwavelength Investigation of Spiral Structures in z > 1 Galaxies with JWST

Abstract Recent JWST observations have revealed the prevalence of spiral structures at z > 1. Unlike in the local Universe, the origin and the consequence of spirals at this epoch remain unexplored. We use public JWST/NIRCam data from the COSMOS-Web survey to map spiral structures in eight massive (>1010.5 M ⊙) star-forming galaxies at z spec ∼ 1.5. We present a method for systematically quantifying spiral arms at z > 1, enabling direct measurements of flux distributions. Using rest-frame near-IR images, we construct morphological models accurately tracing spiral arms. We detect offsets (∼0.2–0.8 kpc) between the rest-frame optical and near-IR flux distributions across most arms. Drawing parallels to the local Universe, we conclude that these offsets reflect the presence of density waves. For 9 out of 18 arms, the offsets indicate spiral shocks triggered by density waves. In all, 5 arms have offsets in the opposite direction and are likely associated with tidal interactions. For the remaining cases with no detected offsets, we suggest that stochastic “clumpy” star formation is the primary driver of their formation. In conclusion, we find a multifaceted nature of spiral arms at z > 1, similar to that in the local Universe.

Carbon and Iron Deficiencies in Quiescent Galaxies at z = 1–3 from JWST-SUSPENSE: Implications for the Formation Histories of Massive Galaxies

Abstract We present the stellar metallicities and multielement abundances (C, Mg, Si, Ca, Ti, Cr, and Fe) of 15 massive (log M/M ⊙ = 10.2–11.2) quiescent galaxies at z = 1–3, derived from ultradeep JWST-SUSPENSE spectra. Compared to quiescent galaxies at z ∼ 0, these galaxies exhibit a deficiency of 0.26 ± 0.04 dex in [C/H], 0.16 ± 0.03 dex in [Fe/H], and 0.07 ± 0.04 dex in [Mg/H], implying rapid formation and quenching before significant enrichment from asymptotic giant branch stars and Type Ia supernovae. Additionally, we find that galaxies forming at higher redshift consistently show higher [Mg/Fe] and lower [Fe/H] and [Mg/H], regardless of their observed redshift. The evolution in [Fe/H] and [C/H] is therefore primarily driven by lower-redshift samples naturally including galaxies with longer star formation timescales. In contrast, the lower [Mg/H] likely reflects earlier-forming galaxies expelling larger gas reservoirs during their quenching phase. Consequently, the mass–metallicity relation, primarily reflecting [Mg/H], is somewhat lower at z = 1–3 compared to the lower-redshift relation. Finally, we compare our results to standard stellar population modeling approaches employing solar abundance patterns and nonparametric star formation histories (using Prospector). Our simple stellar population (SSP)-equivalent ages agree with the mass-weighted ages from Prospector, while the metallicities disagree significantly. Nonetheless, the metallicities better reflect [Fe/H] than total [Z/H]. We also find that the star formation timescales inferred from elemental abundances are significantly shorter than those from Prospector, and we discuss the resulting implications for the early formation of massive galaxies.

Pattern finding in millimetre-wave spectra of massive young stellar objects

Massive stars (M* > 8 M⊙) play a pivotal role in shaping their galactic surroundings due to their high luminosity and intense ionizing radiation. However, the precise mechanisms governing the formation of massive stars remain elusive. Complex organic molecules (COMs) offer an avenue for studying star formation across the low- to high-mass spectrum because COMs are found in every young stellar object (YSO) phase and offer insight into the structure and temperature. We aim to unveil patterns in the evolution of COM chemistry in 41 massive young stellar objects (MYSOs) sourced from diverse catalogues, using Atacama Large Millimeter/Submillimeter Array Band 6 spectra. Previous line analysis of these sources revealed the presence of methanol, methyl acetylene, and methyl cyanide with diverse excitation temperatures (a few tens to hundreds of Kelvin) and column densities (spanning two to four orders of magnitude in range), indicating a possible evolutionary path across sources. However, such analyses usually involve manual line extraction and rotational diagram fitting. We improved upon this process by directly retrieving the physicochemical state of MYSOs from their dimensionally reduced spectra. We used a locally linear embedding to find a lower-dimensional projection for the physicochemical parameters obtained from individual line analysis. We identified clusters of similar MYSOs in the embedded space using a Gaussian mixture model, revealing three groups of MYSOs corresponding to distinct physicochemical conditions: (i) cold, COM-poor sources, (ii) warm, medium-COM-abundance sources, and (iii) hot, COM-rich sources. Principal component analysis (PCA) of the source spectra further supported an evolutionary path across MYSO groups. Finally, by training a simple random forest model on the first few PCA components, we found that the physicochemical state of MYSOs in our sample can be derived directly from the spectra. Our results highlight the effectiveness of dimensionality reduction in obtaining clear physical insights directly from MYSO spectra.

Global and Local Infall in the ASHES Sample (GLASHES). I. Pilot Study in G337.541

Abstract Recent high-angular-resolution observations indicate the need for core growth to form high-mass stars. To understand the gas dynamics at the core scale in the very early evolutionary stages before being severely affected by feedback, we have conducted Atacama Large Millimeter/submillimeter Array (ALMA) observations toward a 70 μm dark massive clump, G337.541-00.082 as part of the Global and Local infall in the ASHES sample (GLASHES) program. Using dense gas tracers such as N2H+ (J = 1–0) and HNC (J = 3–2), we find signs of infall from the position–velocity diagram and more directly from the blue asymmetry profile in addition to the clump-scale velocity gradient. We estimate infall velocities from intermediate and low-mass cores to be 0.28–1.45 km s−1, and infall rates to be on the order of 10−4–10−3 M ⊙ yr−1, both are higher than those measured in low-mass star-forming regions by more than a factor of 5 and an order of magnitude, respectively. We find a strong correlation between the infall velocity with the nonthermal velocity dispersion, suggesting that infall may contribute significantly to the observed line width. Consistent with clump-fed scenarios, we show that the mass infall rate is larger for larger core masses and shorter distances to the clump center. Such high infall rates in cores embedded in IRDCs can be considered as strong signs of core growth, allowing high-mass star formation from intermediate-mass cores that would not initially form high-mass stars at their current mass.

The Gas-to-Dust Ratio Investigation in the Massive Star-Forming region M17

Abstract M17 is a well-known massive star-forming region, and its Gas-to-Dust Ratio (GDR) may vary significantly compared to the other areas. The mass of gas can be traced by the CO emission observed in the Milky Way Imaging Scroll Painting (MWISP) project. The dust mass can be traced by analyzing the interstellar extinction magnitude obtained from the United Kingdom Infrared Telescope (UKIRT). We computed the ratio W(CO)/AV: for AV ≤ 10 mag, W(12CO)/AV = (6.27 ± 0.19) K · km/s · mag−1 and W(13CO)/AV = (0.75 ± 0.72) K · km/s · mag−1; whereas for AV ≥ 10 mag, W(12CO)/AV = (15.8 ± 0.06) K · km/s · mag−1 and W(13CO)/AV = (3.11 ± 0.25) K · km/s · mag−1. Then, we converted the W(CO)/AV into ${N(\rm H)/A_V}$. Using the WD01 model, we derived the GDR: for AV ≤ 10 mag, the GDRs were 118 ± 9 for 12CO and 83 ± 62 for 13CO, comparable to those of the Milky Way; however, for AV ≥ 10 mag, the GDRs increased significantly to 296 ± 3 for 12CO and 387 ± 40 for 13CO, approximately three times higher than those of the Milky Way. In the discussion, we compared the results of this work with previous studies and provided a detailed discussion of the influence of massive stars and other factors on GDR.

SCUBADive. I. JWST+ALMA Analysis of 289 Submillimeter Galaxies in COSMOS-web

Abstract JWST has enabled detecting and spatially resolving the heavily dust-attenuated stellar populations of submillimeter galaxies, revealing detail that was previously inaccessible. In this work, we construct a sample of 289 submillimeter galaxies with joint Atacama Large Millimeter/submillimeter Array (ALMA) and JWST constraints in the COSMOS field. Sources are originally selected using the SCUBA-2 instrument and have archival ALMA observations from various programs. Their JWST NIRCam imaging is from COSMOS-Web and PRIMER. We extract multiwavelength photometry in a manner that leverages the unprecedented near-infrared (NIR) spatial resolution of JWST, and we fit the data with spectral energy distribution models to derive photometric redshifts, stellar masses, star formation rates, and optical attenuation. The sample has an average 〈 z 〉 = 2 . 6 − 0.8 + 1.0 , 〈 A V 〉 = 2 . 5 − 1.0 + 1.5 , 〈 SFR 〉 = 30 0 − 200 + 400 M ⊙ yr − 1 , and 〈 log ( M * / M ⊙ ) 〉 = 11 . 1 − 0.5 + 0.3 . There are 81 (30%) galaxies that have no previous optical/NIR detections, including 75% of the z > 4 subsample (n = 28). The faintest observed NIR sources have the highest redshifts and largest A V = 4 ± 1. In a preliminary morphology analysis we find that ∼10% of the members of our sample exhibit spiral arms and 5% host stellar bars, with one candidate bar found at z > 3. Finally, we find that the clustering of JWST sources within 10″ of a submillimeter galaxy is a factor of 2 greater than what is expected based on either random clustering or the distribution of sources around any red galaxy irrespective of a submillimeter detection.

The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt–Schmidt Star Formation Law on Subkiloparsec Scales

Abstract The molecular Kennicutt–Schmidt Law has been key for understanding star formation (SF) in galaxies across all redshifts. However, recent subkiloparsec observations of nearby galaxies reveal deviations from the nearly unity slope (N) obtained with disk-averaged measurements. We study SF and molecular gas (MG) distribution in the early-stage luminous infrared galaxy merger Arp 240 (NGC 5257-8). Using Very Large Array radio continuum (RC) and Atacama Large Millimeter/submillimeter Array CO(2–1) observations at 500 pc scale, with a uniform grid analysis, we estimate SF rates and MG surface densities (ΣSFR and Σ H 2 , respectively). In Arp 240, N is sublinear at 0.52 ± 0.17. For NGC 5257 and NGC 5258, N is 0.52 ± 0.16 and 0.75 ± 0.15, respectively. We identify two SF regimes: high surface brightness (HSB) regions in RC with N ~ 1, and low surface brightness (LSB) regions with shallow N (ranging 0.15 ± 0.09–0.48 ± 0.04). Median CO(2–1) linewidth and MG turbulent pressure (P turb) are 25 km s−1 and 9 × 105 K cm−3. No significant correlation was found between ΣSFR and CO(2–1) linewidth. However, ΣSFR correlates with P turb, particularly in HSB regions (ρ > 0.60). In contrast, SF efficiency moderately anticorrelates with P turb in LSB regions but shows no correlation in HSB regions. Additionally, we identify regions where peaks in SF and MG are decoupled, yielding a shallow N (≤0.28 ± 0.18). Overall, the range of N reflects distinct physical properties and distribution of both the SF and MG, which can be masked by disk-averaged measurements.

The Hubble Space Telescope Survey of M31 Satellite Galaxies. IV. Survey Overview and Lifetime Star Formation Histories

Abstract From >1000 orbits of HST imaging, we present deep homogeneous resolved star color–magnitude diagrams that reach the oldest main-sequence turnoff and uniformly measured star formation histories (SFHs) of 36 dwarf galaxies (−6 ≥ M V ≥ −17) associated with the M31 halo, and for 10 additional fields in M31, M33, and the Giant Stellar Stream. From our SFHs, we find: (i) The median stellar age and quenching epoch of M31 satellites correlate with galaxy luminosity and galactocentric distance. Satellite luminosity and present-day distance from M31 predict the satellite quenching epoch to within 1.8 Gyr at all epochs. This tight relationship highlights the fundamental connection between satellite halo mass, environmental history, and star formation duration. (ii) There is no difference between the median SFH of galaxies on and off the great plane of Andromeda satellites. (iii) ~50% of our M31 satellites show prominent ancient star formation (>12 Gyr ago) followed by delayed quenching (8–10 Gyr ago), which is not commonly observed among the MW satellites. (iv) A comparison with TNG50 and FIRE-2 simulated satellite dwarfs around M31-like hosts shows that some of these trends (dependence of SFH on satellite luminosity) are reproduced in the simulations while others (dependence of SFH on galactocentric distance, presence of the delayed-quenching population) are weaker or absent. We provide all photometric catalogs and SFHs as High-Level Science Products on MAST.

The host galaxies of radio AGN: New views from combining LoTSS and MaNGA observations

The role of radio mode active galactic nuclei (AGN) feedback on galaxy evolution is still under debate. In this study we utilized a combination of radio continuum observations and optical integral field spectroscopic (IFS) data to explore the impact of radio AGN on the evolution of their host galaxies at global and subgalactic scales. We constructed a comprehensive radio-IFS sample comprising 5548 galaxies with redshift z<0.15 by cross-matching the LOFAR Two-Metre Sky Survey (LoTSS) with the Mapping Nearby Galaxies at APO (MaNGA) survey. We revisited the tight linear radio continuum--star formation relation and quantify its intrinsic scatter, then used the relation to classify 616 radio-excess AGN with excessive radio luminosities over the values expected from their star formation rates. Massive radio AGN host galaxies are predominantly quiescent systems, but the quenching level shows no correlation with the jet luminosity. The mass assembly histories derived from the stellar population synthesis model fitting agree with the cosmological simulations incorporating radio-mode AGN feedback models. We observe that radio AGN hosts grow faster than a control sample of galaxies matched in stellar mass, and the quenching age (rm ∼ 5,Gyr) is at larger lookback times than the typical radio jet age (rm < 1,Gyr). By stacking the spectra in different radial bins and comparing results for radio AGN hosts and their controls, we find emission line excess features in the nuclear region of radio AGN hosts. This excess is more prominent in low-luminosity, low-mass, and compact radio AGN. The N II /rm Hα ratios of the excessive emission line indicate that radio AGN or related jets are ionizing the surrounding interstellar medium in the vicinity of the nucleus. Our results support the scenario that the observed present-day radio AGN activity may help their host galaxies maintain quiescence through gas ionization and heating, but it is not responsible for the past quenching of their hosts.

Not Just Winds: Why Models Find That Binary Black Hole Formation Is Metallicity-dependent, while Binary Neutron Star Formation Is Not

Abstract Both detailed and rapid population studies alike predict that binary black hole (BHBH) formation is orders of magnitude more efficient at low metallicity than high metallicity, while binary neutron star (NSNS) formation remains mostly flat with metallicity, and black hole–neutron star mergers show intermediate behavior. This finding is a key input to employ double compact objects as tracers of low-metallicity star formation, as spectral sirens, and for merger rate calculations. Yet the literature offers various (sometimes contradicting) explanations for these trends. We investigate the dominant cause for the metallicity dependence of double compact object formation. We find that the BHBH formation efficiency at low metallicity is set by initial condition distributions, and conventional simulations suggest that about one in eight interacting binary systems with sufficient mass to form black holes will lead to a merging BHBH. We further find that the significance of metallicities in double compact object formation is a question of formation channel. The stable mass transfer and chemically homogeneous evolution channels mainly diminish at high metallicities due to changes in stellar radii, while the common envelope channel is primarily impacted by the combined effects of stellar winds and mass-scaled natal kicks. Outdated giant wind prescriptions exacerbate the latter effect, suggesting that BHBH formation may be much less metallicity-dependent than previously assumed. NSNS formation efficiency remains metallicity-independent, as they form exclusively through the common envelope channel, with natal kicks that are assumed to be uncorrelated with mass. Forthcoming gravitational-wave observations will provide valuable constraints on these findings.