Suppression Of Star Formation Research Articles

How the cool-core population transitions from galaxy groups to massive clusters. A comparison of the largest Magneticum simulation with eROSITA, XMM-Newton, Chandra and LOFAR observations

Our aim is to understand how the interplay between black hole (BH) feedback and merge processes can effectively turn cool-core galaxy clusters into hot-core clusters in the modern universe. Additionally, we also aim to clarify which parameters of the BH feedback model used in simulations can cause an excess of feedback at the scale of galaxy groups while not efficiently suppressing star formation at the scale of galaxy clusters. To obtain robust statistics of the cool-core population, we compare the modern Universe snapshot (z = 0.25) of the largest Magneticum simulation ( Box2b/hr ) with the eROSITA eFEDS survey and Planck SZ-selected clusters observed with XMM-Newton. Additionally, we compare the BH feedback injected by the simulation in radio mode with Chandra observations of X-ray cavities, and LOFAR observations of radio emission. We confirm a decreasing trend in cool-core fractions towards the most massive galaxy clusters, which is well reproduced by the Magneticum simulations. This evolution is connected with an increased merge activity that injects high-energy particles into the core region, but it also requires thermalisation and conductivity to enhance mixing through the intra-cluster medium core, where both factors are increasingly efficient towards the high mass end. On the other hand, BH feedback remains as the dominant factor at the scale of galaxy groups, while its relative impact decreases towards the most massive clusters. The problems suppressing star formation in simulations are not caused by low BH feedback efficiencies. They root in the definition of the black hole sphere of influence used to distribute the feedback, which decreases as density and accretion rate increase. Actually, a decreasing BH feedback efficiency towards low-mass galaxy groups is required to prevent overheating. These problems can be addressed in simulations by using relations between accretion rate, cavity power, and cavity reach derived from X-ray observations.

Moderate Influence of Halo Spin on Stellar Mass Distributions in Dwarf and Massive Galaxies

Abstract We estimate halo spins for H i-rich galaxies in the Arecibo Legacy Fast ALFA survey using a semi-analytic approach, examining the relationship between halo spin and stellar surface density. Our findings reveal an inverse correlation in both low- and high-mass galaxy samples, with stellar surface density decreasing as halo spin increases. This trend highlights the pivotal role of halo spin in galaxy evolution and suggests a universal formation scenario: high-spin halos, accompanied by high-spin accreted gas, retain angular momentum, preventing gas from efficiently condensing in the galactic center and thus suppressing star formation. Consequently, weak feedback redistributes gas to the halo outskirts without significant expulsion. The shallower central gravitational potential in high-spin halos promotes outward stellar migration, leading to more extended stellar distributions and lower stellar surface densities.

The puzzle of isolated and quenched dwarf galaxies in cosmic voids

We report, for the first time, the detection of a sample of quenched and isolated dwarf galaxies (with 8.9 < log(M⋆/M⊙) < 9.5) in the least dense regions of the cosmic web, including voids, filaments, and walls. These dwarfs have no neighboring galaxy within 1.0 Mpc in projected distance. Based on the full spectral fitting of their central spectra using Sloan Digital Sky Survey data, these galaxies are gas-deprived, while also exhibiting a stellar mass assembly very similar to dwarfs in the central regions of galaxy clusters. Furthermore, they have experienced no significant star formation in the past 2 Gyr. Additionally, analyses of r-band images from the Dark Energy Camera Legacy Survey have shown that these dwarf galaxies host a central nuclear star cluster (NSC). Detecting quenched, isolated dwarf galaxies in cosmic voids indicates that environmental factors are not the sole drivers of their quenching. Internal mechanisms, such as feedback from in situ star formation, which also contribute to the NSC formation, along with black holes or variations in the conditions around their formation, offer potential explanations for star formation suppression in these galaxies. These findings highlight the need for a significant revision in our understanding of baryonic physics, particularly concerning the formation and evolution of low-mass galaxies.

Investigating the Star Formation Characteristics of Radio Active Galactic Nuclei

The coevolution of supermassive black holes and their host galaxies represents a fundamental question in astrophysics. One approach to investigating this question involves comparing the star formation rates (SFRs) of active galactic nuclei (AGNs) with those of typical star-forming galaxies. At relatively low redshifts (z ≲ 1), radio AGNs manifest diminished SFRs, indicating suppressed star formation, but their behavior at higher redshifts is unclear. To examine this, we leveraged galaxy and radio-AGN data from the well-characterized W-CDF-S, ELAIS-S1, and XMM-LSS fields. We established two mass-complete reference star-forming galaxy samples and two radio-AGN samples, consisting of 1763 and 6766 radio AGNs, the former being higher in purity and the latter more complete. We subsequently computed star-forming fractions (f SF; the fraction of star-forming galaxies to all galaxies) for galaxies and radio-AGN host galaxies and conducted a robust comparison between them up to z ≈ 3. We found that the tendency for radio AGNs to reside in massive galaxies primarily accounts for their low f SF, which also shows a strong negative dependence upon M ⋆ and a strong positive evolution with z. To investigate further the star formation characteristics of those star-forming radio AGNs, we constructed the star-forming main sequence (MS) and investigated the behavior of the position of AGNs relative to the MS at z ≈ 0–3. Our results reveal that radio AGNs display lower SFRs than star-forming galaxies in the low-z and high-M ⋆ regime and, conversely, exhibit comparable or higher SFRs than MS star-forming galaxies at higher redshifts or lower M ⋆.

SDSS. IV. MaNGA: The Impact of the Acquisition of Gas with Opposite Angular Momentum on the Evolution of Galaxies

A gaseous counterrotating galaxy is a galaxy containing a gas component with opposite angular momentum to the main stellar disk. The counterrotating gas provides direct evidence for the accretion of external material, a key aspect in hierarchical galaxy evolution. We identified 303 gaseous counterrotators out of 9992 galaxies in MaNGA. The majority of the counterrotators are early types. This implies their formation is highly correlated with early-type galaxies, although it is still difficult to know if one leads to the other. To disentangle which of the galaxy characteristics within a morphological class were changed by the accretion of counterrotating gas, we carefully selected a comparison sample with similar fundamental galactic properties but corotation in gas. This comparison shows that gaseous counterrotation correlates with weak rotation in the stellar component, the high central concentration of star-forming regions, if present, and a higher fraction of central low ionization emission regions (cLIER) galaxies. The light distributions of the stellar components, dust and H i content (both low), and overall suppressed star formation rates are similar for both samples and seem typical for the morphological class. We claim that elliptical and about half of the lenticular counterrotators, those with weak rotation in the stellar component in the outskirts and central regions, likely have a major merger origin for the gas acquisition, and the other half of lenticulars, with stronger stellar rotation, may have a minor merger or pure gas accretion origin.

Active Galactic Nuclei in the Green Valley at z ∼ 0.7

We present near-infrared (NIR) spectroscopy using the MMT and Magellan infrared spectrograph for a sample of 29 massive galaxies ( logM*/M⊙≳10 ) at z ∼ 0.7 with optical spectroscopy from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. Having both optical and NIR spectroscopy at this redshift allows us to measure the full suite of rest-optical strong emission lines, enabling the study of ionization sources and the rest-optical selection of active galactic nuclei (AGN), as well as the measurement of dust-corrected Hα-based star formation rates (SFRs). We find that 11 out of 29 galaxies host AGN. We infer the nonparametric star formation histories with the spectral energy distribution fitting code Prospector and classify galaxies as star-forming, green valley, or quiescent based on their most recent specific SFRs. We explore the connection between AGN activity and suppressed star formation, and find that 89% ± 15% of galaxies in the green valley or below host AGN, while only 15% ± 8% of galaxies above the green valley host AGN. We construct the star-forming main sequence (SFMS) and find that the AGN host galaxies are 0.37 dex below the SFMS, while galaxies without detectable AGN are consistent with being on the SFMS. However, when compared to a bootstrapped mass-matched sample, the SFRs of our sample of AGN host galaxies are consistent with the full LEGA-C sample. Based on this mass-matched analysis, we cannot rule out that this suppression of star formation is driven by other processes associated with the higher mass of the AGN sample. We therefore cannot link the presence of AGN activity to the quenching of star formation.

JADES + JEMS: A Detailed Look at the Buildup of Central Stellar Cores and Suppression of Star Formation in Galaxies at Redshifts 3 < z < 4.5

We present a spatially resolved study of stellar populations in six galaxies with stellar masses M * ∼ 1010 M ☉ at z ∼ 3.7 using 14-filter James Webb Space Telescope (JWST)/NIRCam imaging from the JADES and JEMS surveys. The six galaxies are visually selected to have clumpy substructures with distinct colors over rest frame 3600−4100 Å, including a red, dominant stellar core that is close to their stellar-light centroids. With 23-filter photometry from the Hubble Space Telescope to JWST, we measure the stellar-population properties of individual structural components via spectral energy distribution fitting using Prospector. We find that the central stellar cores are ≳2 times more massive than the Toomre mass, indicating they may not form via single in situ fragmentation. The stellar cores have stellar ages of 0.4−0.7 Gyr that are similar to the timescale of clump inward migration due to dynamical friction, suggesting that they likely instead formed through the coalescence of giant stellar clumps. While they have not yet quenched, the six galaxies are below the star-forming main sequence by 0.2−0.7 dex. Within each galaxy, we find that the specific star formation rate is lower in the central stellar core, and the stellar-mass surface density of the core is already similar to quenched galaxies of the same masses and redshifts. Meanwhile, the stellar ages of the cores are either comparable to or younger than the extended, smooth parts of the galaxies. Our findings are consistent with model predictions of the gas-rich compaction scenario for the buildup of galaxies’ central regions at high redshifts. We are likely witnessing the coeval formation of dense central cores, along with the onset of galaxy-wide quenching at z > 3.

ViCTORIA project: The LOFAR-MeerKAT view of active galactic nuclei in Virgo cluster early-type galaxies

Context. The evolution of active galactic nuclei (AGNs) is closely connected to their host galaxies and surroundings. Via feedback processes, AGNs can counteract the cooling of the intracluster medium (ICM) and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGNs as well as their feedback mechanisms. Aims. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle, and investigate environmental feedback in cluster member galaxies. Methods. We analysed 144 MHz and 1.3 GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT. Results. We detect 12 of these galaxies at 144 MHz, five of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC 4365 (M* = 2.2 × 1011 M⊙) is not detected as compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC 4472 (=M 49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.

The generation of a multiphase medium in ‘Splash’ bridge systems: towards an understanding of star formation suppression in turbulent galaxy systems

ABSTRACT Cloud–cloud collisions in splash bridges produced in gas-rich disc galaxy collisions offer a brief but interesting environment to study the effects of shocks and turbulence on star formation rates in the diffuse intergalactic medium, far from the significant feedback effects of massive star formation and active galactic nucleus. Expanding on our earlier work, we describe simulated collisions between counter-rotating disc galaxies of relatively similar mass, focusing on the thermal and kinematic effects of relative inclination and disc offset at the closest approach. This includes essential heating and cooling signatures, which go some way towards explaining the luminous power in H$_2$ and [C ii] emission in the Taffy bridge, as well as providing a partial explanation of the turbulent nature of the recently observed compact CO-emitting clouds observed in Taffy by the Atacama Large Millimeter Array (ALMA). The models show counter-rotating disc collisions result in swirling, shearing kinematics for the gas in much of the post-collision bridge. Gas with little specific angular momentum due to collisions between counter-rotating streams accumulates near the centre of mass. The disturbances and mixing in the bridge drive continuing cloud collisions, differential shock heating, and cooling throughout. A wide range of relative gas phases and line-of-sight velocity distributions are found in the bridges, depending sensitively on initial disc orientations, and the resulting variety of cloud collision histories. Most cloud collisions can occur promptly or persist for quite a long duration. Cold and hot phases can largely overlap throughout the bridge or can be separated into different parts of the bridge.

The effects of stellar and AGN feedback on the cosmic star formation history in the simba simulations

ABSTRACT Using several variants of the cosmological simba simulations, we investigate the impact of different feedback prescriptions on the cosmic star formation history. Adopting a global-to-local approach, we link signatures seen in global observables, such as the star formation rate density (SFRD) and the galaxy stellar mass function (GSMF), to feedback effects in individual galaxies. We find a consistent picture: stellar feedback mainly suppresses star formation below halo masses of $M_{\rm H} = 10^{12} \rm \, {\rm M}_{\odot }$ and before $z = 2$, whereas AGN feedback quenches the more massive systems after $z = 2$. Among simba’s AGN feedback modes, AGN jets are the dominant quenching mechanism and set the shape of the SFRD and the GSMF at late times. AGN-powered winds only suppress the star formation rate in intermediate-mass galaxies ($M_{\rm \star } = 10^{9.5 - 10} \rm \, {\rm M}_{\odot }$), without affecting the overall stellar mass-assembly significantly. At late times, the AGN X-ray feedback mode mainly quenches residual star formation in massive galaxies. Our analysis reveals that this mode is also necessary to produce the first fully quenched galaxies before $z=2$, where the jets alone are inefficient. These initially highly star-forming galaxies contain relatively large black holes, likely strengthening the X-ray-powered heating and ejection of gas from the dense, central region of galaxies. Such extra heating source quenches the local star formation and produces a more variable accretion rate. More generally, this effect also causes the break down of correlations between the specific star formation rate, the accretion rate and the black hole mass.

QSOFEED: Relationship between star formation and active galactic nuclei feedback

Context. Large-scale cosmological simulations suggest that feedback from active galactic nuclei (AGN) plays a crucial role in galaxy evolution. More specifically, outflows are one of the mechanisms by which the accretion energy of the AGN is transferred to the interstellar medium (ISM), heating and driving out gas and impacting star formation (SF). Aims. The purpose of this study is to directly test this hypothesis utilising SDSS spectra of a well-defined sample of 48 low-redshift (z &lt; 0.14) type 2 quasars (QSO2s). Methods. By exploiting these data, we were able to characterise the kinematics of the warm ionised gas by performing a non-parametric analysis of the [OIII]λ5007 emission line. We also constrained the properties of the young stellar populations (YSP; tysp &lt; 100 Myr) of their host galaxies via spectral synthesis modelling. Results. These analyses revealed that 85% of the QSO2s display velocity dispersions in the warm ionised gas phase greater than that of the stellar component of their host galaxies, indicating the presence of AGN-driven outflows. We compared the gas kinematics with the intrinsic properties of the AGN and found that there is a positive correlation between gas velocity dispersion and 1.4 GHz radio luminosity – but not with the AGN bolometric luminosity or Eddington ratio. This either suggests that the radio luminosity is the key factor driving outflows or that the outflows themselves are shocking the ISM and producing synchrotron emission. We found that 98% of the sample host YSPs to varying degrees, with star formation rates (SFRs) of 0 ≤ SFR ≤ 92 M⊙ yr−1, averaged over 100 Myr. We compared the gas kinematics and outflow properties to the SFRs to establish possible correlations that could suggest that the presence of the outflowing gas could be impacting SF, but we found that no such correlation exists. This leads us to the conclusion that on the scales probed by the SDSS fibre (between 2 and 7 kpc diameters), AGN-driven outflows do not impact SF on the timescales probed in this study. However, we find a positive correlation between the light-weighted stellar ages of the QSO2s and the black hole mass, which might indicate that successive AGN episodes lead to the suppression of SF over the course of galaxy evolution.

Extended CO(1–0) survey and ammonia measurements towards two bubble regions in W5

The feedback effect of massive stars can either accelerate or inhibit star formation activity within molecular clouds. Studying the morphology of molecular clouds near W5 offers an excellent opportunity to examine this feedback effect. We conducted a comprehensive survey of the W5 complex using the Purple Mountain Observatory 13.7 m millimeter telescope. This survey includes 12CO, 13CO, and C18O (J = 1 − 0), with a sky coverage of 6.6 deg2 (136.0° &lt; l &lt; 138.75°, 0° &lt; b &lt; 2.4°). Furthermore, we performed simultaneous observations of the NH3 (1,1) and NH3 (2,2) lines in the four densest star-forming regions of W5, using the 26 m radio telescope of the Xinjiang Astronomy Observatory (XAO). Our analysis of the morphological distribution of the molecular clouds, distribution of high-mass young stellar objects (HMYSOs), 13CO/C18O abundance ratio, and the stacked average spectral line distribution at different 8 μm thresholds provide compelling evidence of triggering. Within the mapped region, we identified a total of 212 molecular clumps in the 13CO cube data using the astrodendro algorithm. Remarkably, approximately 26.4% (56) of these clumps demonstrate the potential to form massive stars and 42.9% (91) of them are gravitationally bound. Within clumps that are capable of forming high-mass stars, there is a distribution of class I YSOs, all located in dense regions near the boundaries of the HII regions. The detection of NH3 near the most prominent cores reveals moderate kinetic temperatures and densities (as CO). Comparing the Tkin and Tex values reveals a reversal in trends for AFGL 4029 (higher Tex and lower Tkin) and W5-W1, indicating the inadequacy of optically thick CO for dense region parameter calculations. Moreover, a comparison of the intensity distributions between NH3 (1,1) and C18O (1–0) in the four densest region reveals a notable depletion effect in AFGL 4029, characterised by a low Tkin (9 K) value and a relatively high NH3 column density, 2.5 × 1014 cm−2. By classifying the 13CO clumps as: “feedback,” “non-feedback,” “outflow,” or “non-outflow” clumps, we observe that the parameters of the “feedback” and “outflow” clumps exhibit variations based on the intensity of the internal 8 μm flux and the outflow energy, respectively. These changes demonstrate a clear linear correlation, which distinctly separate them from the parameter distributions of the “non-feedback” and “non-outflow” clumps, thus providing robust evidence to support a triggering scenario.

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

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

Modelling the star-formation activity and ionizing properties of high-redshift galaxies

Early results from the JWST observations have reported a surprisingly high number of UV-bright galaxies at z ≥ 10, which appears to challenge the theoretical predictions from standard galaxy formation models in the ΛCDM framework at these redshifts. To alleviate this tension, several cosmological and astrophysical interpretations have been advanced. However, all of these proposed scenarios carry noteworthy consequences for other large-scale processes in the early Universe, particularly cosmic reionization, since high-redshift galaxies are believed to be the primary ionizing sources during the Epoch of Reionization (EoR). To investigate this, we introduce a semi-analytical model of galaxy formation and evolution that explains the evolving galaxy UV luminosity function (UVLF) over 6 ≲ z ≲ 15, and also jointly tracks the time evolution of the globally averaged neutral hydrogen fraction in the intergalactic medium. The model self-consistently accounts for the suppression of star formation in low-mass galaxies due to reionization feedback and is constrained by comparing the model predictions with various observational probes like the UVLF data from HST and JWST, recent measurements of the neutral hydrogen fraction, and the CMB scattering optical depth. Our analysis confirms that a rapid enhancement in the star-formation rate efficiency and/or UV luminosity per stellar mass formed is necessary for consistency with the JWST UVLF estimates at z ≥ 10. We further find that it is possible to jointly satisfy the current reionization constraints when the escape fraction is assumed to be halo-mass dependent, requiring higher Lyman-continuum leakage from low-mass galaxies. We also examine the relative contribution of galaxies with different UV luminosities towards the ionizing photon budget for the EoR and investigate the large-scale bias of high-z galaxies.

The impact of shear on the rotation of Galactic plane molecular clouds

ABSTRACT Stars form in the densest regions of molecular clouds; however, there is no universal understanding of the factors that regulate cloud dynamics and their influence on the gas-to-star conversion. This study considers the impact of Galactic shear on the rotation of giant molecular clouds (GMCs) and its relation to the solenoidal modes of turbulence. We estimate the direction of rotation for a large sample of clouds in the $\mathrm{^{13}CO}$/$\mathrm{C^{18}O}$(3–2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) and their corresponding sources in a new segmentation of the $\mathrm{^{12}CO}$(3–2) High-Resolution Survey. To quantify the strength of shear, we introduce a parameter that describes the shear’s ability to disrupt growing density perturbations within the cloud. Although we find no correlation between the direction of cloud rotation, the shear parameter, and the magnitude of the velocity gradient, the solenoidal fraction of the turbulence in the CHIMPS sample is positively correlated with the shear parameter and behaves similarly when plotted over Galactocentric distance. GMCs may thus not be large or long-lived enough to be affected by shear to the point of showing rotational alignment. In theory, Galactic shear can facilitate the rise of solenoidal turbulence and thus contribute to suppressing star formation. These results also suggest that the rotation of clouds is not strictly related to the overall rotation of the disc, but is more likely to be the imprint of Kelvin–Helmholtz instabilities in the colliding flows that formed the clouds.

Magnetic fields in star-forming environments: how does field strength affect gas on spiral arm and cloud scales?

ABSTRACT We investigate star formation from subpc to kpc scales with magnetohydrodynamic models of a cloud structure and a section of galactic spiral arm. We aim to understand how magnetic fields affect star formation and cloud formation, and how feedback couples with magnetic fields on scales of clouds and clumps. We find that magnetic fields overall suppress star formation by ${\sim}$10 per cent with a weak field (5 $\mu$G) and ${\sim} 50$ per cent with a stronger field (50 $\mu$G). Cluster masses are reduced by about 40 per cent with a strong field but show little change with a weak field. We find that clouds tend to be aligned parallel to the field with a weak field and become perpendicularly aligned with a stronger field, whereas on clump scales the alignment is more random. The magnetic fields and densities of clouds and clumps in our models agree with the Zeeman measurements of the Crutcher relation $B\!-\!\rho$ in the weaker field models, while the strongest field models show a relation that is too flat compared to the observations. In all our models, we find that both subcritical and supercritical clouds and clumps are present. We also find that if using a line-of-sight (1D) measure of the magnetic field to determine the critical parameter, the magnetic field, and thereby also criticality, can vary by a factor of 3–4 depending on whether the direction the field is measured along corresponds to the direction of the ordered component of the magnetic field.

Dark matter scattering constraints from observations of stars surrounding Sgr A*

High-resolution infrared data have revealed several young stars in close proximity to Sgr A*. These stars may encounter extremely high dark matter densities. We examine scenarios where dark matter scatters on stellar gas, accumulates in stellar cores, and then annihilates. We study the stars S2, S62, S4711, and S4714 and find three observable effects. First, dark matter interactions can inhibit star formation close to Sgr A*, favoring scenarios where these stars migrate into the Galactic Center. Second, dark matter interactions can delay main sequence evolution, making stars older than they appear. Third, very high dark matter densities can inject enough energy to disrupt main sequence stars, allowing S-star observations to constrain the dark matter density near Sgr A*. Published by the American Physical Society 2024

JWST/NIRSpec and MIRI observations of an expanding, jet-driven bubble of warm H2 in the radio galaxy 3C 326 N

The physical link between AGN activity and the suppression of star formation in their host galaxies is one of the major open questions of the AGN feedback scenario. The Spitzer space mission revealed a subset of powerful nearby radio galaxies with unusually bright line emission from warm ($T 100$ K) molecular hydrogen, while typical star-formation tracers such as polycyclic aromatic hydrocarbons (PAHs) or a dust continuum have been exceptionally faint or undetected. Here, we present JWST NIRSpec and MIRI MRS IFU observations of one of the best studied galaxies of this class, 3C 326 N at z=0.09. We identified a total of 19 lines of the S, O, and Q series of ro-vibrational H$_2$ emission with NIRSpec at a 0.11 spatial resolution, probing a small quantity odot $) of gas at temperatures of $T 1000$ K. We also mapped the rotational mid-infrared lines of H$_2$ 0--0 S(3), S(5), and S(6) at a spatial resolution of 0.4 with MIRI/MRS, probing most of the $2 odot $ of warm H$_2$ in this galaxy. The CO band heads show a stellar component consistent with a 'slow-rotator' that is typical of a massive ($3 $\,M$_ galaxy, offering a reliable systemic redshift of $z=0.08979 0.0003$. The extended line emission shows a bipolar bubble expanding through the molecular disk at velocities of up to $, delineated by several bright clumps along the northern outer rim, potentially coming from gas fragmentation. Throughout the disk, H$_2$ is very broadly dispersed, with an FWHM of $ 100-1300$ km $ and complex, dual-component Gaussian line profiles. The extended FeII lambda 1.644 and Paalpha follow the same morphology, however NeIII lambda 15.56 is more symmetric about the nucleus. We show that most of the gas (with the exception of NeIII lambda 15.56) is predominantly heated by shocks driven by the radio jets into the gas, both for the ro-vibrational and rotational H$_2$ lines. In addition, the accompanying line broadening is sufficient to suppress star formation in the molecular gas. We also compared the morphology and kinematics of the rotational and ro-vibrational lines, finding the latter to be a good proxy to the global morphology and kinematic properties of the former in strongly turbulent environments. This demonstrates the potential of using the higher frequency ro-vibrational lines in studying turbulent molecular gas. Provided they are bright enough, they would allow us to examine turbulence in galaxies during the early phases of cosmic history, while most rotational lines are red-shifted out of the MIRI bandpass for $z ge1.5$

Local versus global environment: the suppression of star formation in the vicinity of galaxy clusters

ABSTRACT In order to examine where, how and why the quenching of star formation begins in the outskirts of galaxy clusters, we investigate the de-projected radial distribution of a large sample of quenched and star-forming galaxies (SFGs) out to 30R500 around clusters. We identify the SFG sample using radio continuum emission from the Low-Frequency Array Two-metre Sky Survey. We find that the SFG fraction starts to decrease from the field fraction as far out as 10R500, well outside the virial radius of the clusters. We investigate how the SFG fraction depends on both large-scale and local environments, using radial distance from a cluster to characterise the former, and distance from fifth nearest neighbour for the latter. The fraction of SFGs in high-density local environments is consistently lower than that found in low-density local environments, indicating that galaxies’ immediate surroundings have a significant impact on star formation. However, for high-mass galaxies – and low mass galaxies to a lesser extent – high-density local environments appear to act as a protective barrier for those SFGs that survived this pre-processing, shielding them from the external quenching mechanisms of the cluster outskirts. For those galaxies that are not in a dense local environment, the global environment causes the fraction of SFGs to decrease toward the cluster centre in a manner that is independent of galaxy mass. Thus, the fraction of SFGs depends on quite a complex interplay between the galaxies’ mass, their local environment, and their more global cluster-centric distance.

Star Formation Rates in [Ne V] 3426 Å Selected Active Galactic Nuclei: Evidence for a Decrease along the Main Sequence?

Studying the behavior along the galaxy main sequence is key in furthering our understanding of the possible connection between active galactic nucleus (AGN) activity and star formation. We select a sample of 1215 AGN from the catalog of Sloan Digital Sky Survey galaxy properties from the Portsmouth group by detection of the high-ionization [Ne v] 3426 Å emission line. Our sample extends from 1040 to 1042.5 erg s−1 in [Ne v] luminosity in a redshift range z = 0.17 to 0.57. We compare the specific star formation rates (sSFRs; SFR scaled by galaxy mass) obtained from the corrected [O ii] and Hα luminosities, and the spectral energy distribution (SED)–determined values from Portsmouth. We find that the emission-line-based sSFR values are unreliable for the [Ne v] sample due to the AGN contribution, and proceed with the SED sSFRs for our study of the main sequence. We find evidence for a decrease in sSFR along the main sequence in the [Ne v] sample, which is consistent with results from the hard X-ray Burst Alert Telescope AGN sample, which extends to lower redshifts than our [Ne v] sample. Although we do not find evidence that the concurrent AGN activity is suppressing star formation, our results are consistent with a lower gas fraction in the host galaxies of the AGN as compared to that of the star-forming galaxies. If the evacuation of gas, and therefore suppression of star formation, is due to AGN activity, it must have occurred in a previous epoch.