Luminosity Density Research Articles

ALMA 300 pc Resolution Imaging of a z = 6.79 Quasar: No Evidence for Supermassive Black Hole Influence on the C ii Kinematics

We present Atacama Large Millimeter/submillimeter Array (ALMA) [C ii] 158 μm and dust continuum observations of the z = 6.79 quasar J0109–3047 at a resolution of 0.″045 (∼300 pc). The dust and [C ii] emission are enclosed within a ∼500 pc radius, with the central beam (r < 144 pc) accounting for ∼25% (8%) of the total continuum ([C ii]) emission. The far-infrared (FIR) luminosity density increases radially from ∼5 × 1011 L ⊙ kpc−2 to a central value of ∼70 × 1011 L ⊙ kpc−2 (SFRD ∼50–700 M ⊙yr−1 kpc−2). The [C ii] kinematics are dispersion dominated with a constant velocity dispersion of 137 ± 6 km s−1. The constant dispersion implies that the underlying mass distribution is not centrally peaked, consistent with the expectations of a flat gas mass profile. The lack of an upturn in velocity dispersion within the central beam is inconsistent with a black hole mass greater than M BH < 6.5 × 108 M ⊙ (2σ level), unless highly fine-tuned changes in the interstellar medium properties conspire to produce a decrease of the gas mass in the central beam comparable to the black hole mass. Our observations therefore imply either that (a) the black hole is less massive than previously measured, or (b) the central peak of the FIR and [C ii] emission are not tracing the location of the black hole, as suggested by the tentative offset between the near-infrared position of the quasar and the ALMA continuum emission.

The origin of the observed Ly α EW distribution of dwarf galaxies at z ∼ 2

ABSTRACT We present a rest-UV-selected sample of 32 lensed galaxies at z ∼ 2 observed with joint Keck/LRIS rest-UV and Keck/MOSFIRE rest-optical spectra behind the clusters Abell 1689, MACS J0717, and MACS J1149. The sample pushes towards the faintest UV luminosities observed ($-19 \le {M_{\rm UV}} \le -17$) at this redshift. The fraction of dwarf galaxies identified as Ly α emitters ($\rm EW \ge 20$ Å) is ${X_{\rm LAE}}=33^{+17}_{-12}\,{\rm per\, cent}$. We use the Balmer lines and UV continuum to estimate both the intrinsic EW and the Ly α escape fraction to determine their relative importance in dictating the observed EW distribution. Fainter galaxies (MUV &amp;gt; −19) show larger intrinsic EWs and escape fractions than brighter galaxies. Only galaxies with intrinsic EWs greater than 40 Å have escape fractions larger than 5 per cent. We find little to no anticorrelation between the escape fraction and dust in dwarf galaxies. The volumetric escape fraction of our sample is $f_{\rm esc}^{\rm Ly\alpha } = 4.6^{+2.0}_{-1.4}\,{\rm per\, cent}$ in agreement with measurements found elsewhere in the literature. 60 per cent of the total integrated Ly α luminosity density comes from galaxies with EWobs &amp;gt; 20 Å.

Completeness of the NASA/IPAC Extragalactic Database (NED) Local Volume Sample

Abstract We introduce the NASA/IPAC Extragalactic Database (NED) Local Volume Sample (NED-LVS), a subset of ∼1.9 million objects with distances out to 1000 Mpc. We use UV and IR fluxes available in NED from all-sky surveys to derive physical properties, and estimate the completeness relative to the expected local luminosity density. The completeness relative to near-IR luminosities (which traces a galaxy’s stellar mass) is roughly 100% at D &lt; 30 Mpc and remains moderate (70%) out to 300 Mpc. For brighter galaxies (≳L *), NED-LVS is ∼100% complete out to ∼400 Mpc. When compared to other local Universe samples (GLADE and HECATE), all three are ∼100% complete below 30 Mpc. At distances beyond ∼80 Mpc, NED-LVS is more complete than both GLADE and HECATE by ∼10%–20%. NED-LVS is the underlying sample for the NED gravitational-wave follow-up service (NED-GWF), which provides prioritized lists of host candidates for GW events within minutes of alerts issued by the LIGO–Virgo–KAGRA collaboration. We test the prioritization of galaxies in the volume of GW170817 by three physical properties, where we find that both stellar mass and inverse specific star formation rate place the correct host galaxy in the top 10. In addition, NED-LVS can be used for a wide variety of other astrophysical studies: galaxy evolution, star formation, large-scale structure, galaxy environments, and more. The data in NED are updated regularly, and NED-LVS will be updated concurrently. Consequently, NED-LVS will continue to provide an increasingly complete sample of galaxies for a multitude of astrophysical research areas for years to come.

First Sample of Hα+[O iii]λ5007 Line Emitters at z > 6 Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line-luminosity Functions

We present a sample of four emission-line galaxies at z = 6.11–6.35 that were serendipitously discovered using the commissioning data for the James Webb Space Telescope (JWST)/NIRCam wide-field slitless spectroscopy mode. One of them (at z = 6.11) has been reported previously, while the others are new discoveries. These sources are selected by the secure detections of both [O iii] λ5007 and Hα lines with other fainter lines, which were tentatively detected in some cases (e.g., [O ii] λ3727, [O iii] λ4959). In the [O iii]/Hβ–[N ii]/Hα Baldwin–Phillips–Terlevich diagram, these galaxies occupy the same parameter space as that of z ∼ 2 star-forming galaxies, indicating that they have been enriched rapidly to subsolar metallicities (∼0.4 Z ⊙), similar to galaxies with comparable stellar masses at much lower redshifts. The detection of strong Hα lines suggests a higher ionizing photon production efficiency within galaxies in the early universe. We find brightening of the [O iii] λ5007 line-luminosity function (LF) from z = 3 to 6, and weak or no redshift evolution of the Hα line LF from z = 2 to 6. Both LFs are underpredicted at z ∼ 6 by a factor of ∼10 in certain cosmological simulations. This further indicates a global Lyα photon escape fraction of 7%–10% at z ∼ 6, which is slightly lower than previous estimates through the comparison of the UV-derived star formation rate density and Lyα luminosity density. Our sample recovers % of z = 6.0–6.6 galaxies in the survey volume with stellar masses greater than 5 × 108 M ⊙, suggesting the ubiquity of strong Hα and [O iii] line emitters in the Epoch of Reionization, which will be further uncovered in the era of JWST.

A Search for Relativistic Ejecta in a Sample of ZTF Broad-lined Type Ic Supernovae

The dividing line between gamma-ray bursts (GRBs) and ordinary stripped-envelope core-collapse supernovae (SNe) is yet to be fully understood. Observationally mapping the variety of ejecta outcomes (ultrarelativistic, mildly relativistic, or nonrelativistic) in SNe of Type Ic with broad lines (Ic-BL) can provide a key test to stellar explosion models. However, this requires large samples of the rare SN Ic-BL events with follow-up observations in the radio, where fast ejecta can be probed largely free of geometry and viewing angle effects. Here, we present the results of a radio (and X-ray) follow-up campaign of 16 SNe Ic-BL detected by the Zwicky Transient Facility (ZTF). Our radio campaign resulted in four counterpart detections and 12 deep upper limits. None of the events in our sample is as relativistic as SN 1998bw and we constrain the fraction of SN 1998bw-like explosions to <19% (3σ Gaussian equivalent), a factor of ≈2 smaller than previously established. We exclude relativistic ejecta with radio luminosity densities in between ≈5 × 1027 erg s−1 Hz−1 and ≈1029 erg s−1 Hz−1 at t ≳ 20 days since explosion for ≈60% of the events in our sample. This shows that SNe Ic-BL similar to the GRB-associated SNe 1998bw, 2003lw, and 2010bh, or to the relativistic SNe 2009bb and iPTF17cw, are rare. Our results also exclude an association of the SNe Ic-BL in our sample with largely off-axis GRBs with energies E ≳ 1050 erg. The parameter space of SN 2006aj-like events (faint and fast-peaking radio emission) is, on the other hand, left largely unconstrained, and systematically exploring it represents a promising line of future research.

ATLASGAL: 3 mm class I methanol masers in high-mass star formation regions

Context. Class I methanol masers are known to be associated with shocked outflow regions around massive protostars, indicating a possible link between the maser properties and those of their host clumps. Aims. The main goals of this study are (1) to search for new class I methanol masers, (2) to statistically study the relationship between class I masers and shock tracers, (3) to compare the properties between class I masers and their host clumps, also as a function of their evolutionary stage, and (4) to constrain the physical conditions that excite multiple class I masers simultaneously. Methods. We analysed the 3 mm wavelength spectral line survey of 408 clumps identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), which were observed with the IRAM 30-meter telescope, focusing on the class I methanol masers with frequencies near 84, 95, and 104.3 GHz. Results. We detect narrow maser-like features towards 54, 100, and 4 sources in the maser lines near 84, 95, and 104.3 GHz, respectively. Among them, 50 masers at 84 GHz, 29 masers at 95 GHz, and 4 rare masers at 104.3 GHz are new discoveries. The new detections increase the number of known 104.3 GHz masers from five to nine. The 95 GHz class I methanol maser is generally stronger than the 84 GHz maser counterpart. We find nine sources showing class I methanol masers, but no SiO emission, indicating that class I methanol masers might be the only signpost of protostellar outflow activity in extremely embedded objects at the earliest evolutionary stage. Class I methanol masers that are associated with sources that show SiO line wings are more numerous and stronger than those without such wings. The total integrated intensity of class I methanol masers is well correlated with the integrated intensity and velocity coverage of the SiO (2−1) emission. The properties of class I methanol masers are positively correlated with the bolometric luminosity, clump mass, and peak H2 column density of their associated clumps, but are uncorrelated with the luminosity-to-mass ratio, dust temperature, and mean H2 volume density. Conclusions. We suggest that the properties of class I masers are related to shocks traced by SiO. Based on our observations, we conclude that class I methanol masers at 84 and 95 GHz can trace a similar evolutionary stage to the H2O maser, and appear prior to 6.7 and 12.2 GHz methanol and OH masers. Despite their small number, the 104.3 GHz class I masers appear to trace a shorter and more evolved stage compared to the other class I masers.

Spectroscopic Confirmation of CEERS NIRCam-selected Galaxies at z ≃ 8–10

We present JWST/NIRSpec prism spectroscopy of seven galaxies selected from Cosmic Evolution Early Release Science (CEERS) survey NIRCam imaging with photometric redshifts z phot > 8. We measure emission line redshifts of z = 7.65 and 8.64 for two galaxies. For two other sources without securely detected emission lines we measure and by fitting model spectral templates to the prism data, from which we detect continuum breaks consistent with Lyα opacity from a mostly neutral intergalactic medium. The presence of strong breaks and the absence of strong emission lines give high confidence that these two galaxies have redshifts z > 9.6, but the redshift values derived from the breaks alone have large uncertainties given the low spectral resolution and relatively low S/N of the CEERS NIRSpec prism data. The two z ∼ 10 sources observed are relatively luminous (M UV < −20), with blue continua (−2.3 ≲ β ≲ −1.9) and low dust attenuation (); and at least one of them has a high stellar mass for a galaxy at that redshift (). Considered together with spectroscopic observations of other CEERS NIRCam-selected high-z galaxy candidates in the literature, we find a high rate of redshift confirmation and low rate of confirmed interlopers (8%). Ten out of 35 z > 8 candidates with CEERS NIRSpec spectroscopy do not have secure redshifts, but the absence of emission lines in their spectra is consistent with redshifts z > 9.6. We find that z > 8 photometric redshifts are generally in agreement (within their uncertainties) with the spectroscopic values, but also that the photometric redshifts tend to be slightly overestimated (〈Δz〉 = 0.45 ± 0.11), suggesting that current templates do not fully describe the spectra of very-high-z sources. Overall, the spectroscopy solidifies photometric redshift evidence for a high spatial density of bright galaxies at z > 8 compared to theoretical model predictions, and further disfavors an accelerated decline in the integrated UV luminosity density at z > 8.

Life beyond 30: Probing the −20 < M UV < −17 Luminosity Function at 8 < z < 13 with the NIRCam Parallel Field of the MIRI Deep Survey

We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 < z < 13 derived from deep NIRCam observations taken in parallel with the MIRI Deep Survey of the Hubble Ultra Deep Field (HUDF), NIRCam covering the parallel field 2. Our deep (40 hr) NIRCam observations reach an F277W magnitude of 30.8 (5σ), more than 2 mag deeper than JWST public data sets already analyzed to find high-redshift galaxies. We select a sample of 44 z > 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on χ 2 calculations, and predominant solutions compared to z < 8 alternatives. We find mild evolution in the luminosity function from z ∼ 13 to z ∼ 8, i.e., only a small increase in the average number density of ∼0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = − 2.2 ± 0.1, and M * = − 20.8 ± 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses ∼108 M ⊙ during the first 350 Myr of the universe, z ∼ 12, with models matching better the luminosity density observational estimations ∼150 Myr later, by z ∼ 9.

Cosmic evolution of radio-AGN feedback: confronting models with data

ABSTRACT Radio-mode feedback is a key ingredient in galaxy formation and evolution models, required to reproduce the observed properties of massive galaxies in the local Universe. We study the cosmic evolution of radio-active galactic nuclei (AGN) feedback out to z ∼ 2.5 using a sample of 9485 radio-excess AGN. We combine the evolving radio luminosity functions with a radio luminosity scaling relationship to estimate AGN jet kinetic powers and derive the cosmic evolution of the kinetic luminosity density, Ωkin (i.e. the volume-averaged heating output). Compared to all radio-AGN, low-excitation radio galaxies dominate the feedback activity out to z ∼ 2.5, with both these populations showing a constant heating output of $\Omega _{\rm {kin}} \approx (4\!-\!5) \times 10^{32}\, \rm {W\, Mpc^{-3}}$ across 0.5 &amp;lt; z &amp;lt; 2.5. We compare our observations to predictions from semi-analytical and hydrodynamical simulations, which broadly match the observed evolution in Ωkin, although their absolute normalization varies. Comparison to the Semi-Analytic Galaxy Evolution (sage) model suggests that radio-AGN may provide sufficient heating to offset radiative cooling losses, providing evidence for a self-regulated AGN feedback cycle. We integrate the kinetic luminosity density across cosmic time to obtain the kinetic energy density output from AGN jets throughout cosmic history to be $\sim 10^{50}\, \rm {J\, Mpc^{-3}}$. Compared to AGN winds, the kinetic energy density from AGN jets dominates the energy budget at z ≲ 2; this suggests that AGN jets play an important role in AGN feedback across most of cosmic history.

Distance Duality Test: The Evolution of Radio Sources Mimics a Nonexpanding Universe

Distance duality relation (DDR) marks a fundamental difference between expanding and nonexpanding universes, as an expanding metric causes angular diameter distance smaller than luminosity distance by an extra factor of (1 + z). Here we report a test of this relation using two independent samples of ultracompact radio sources observed at 2.29 GHz and 5.0 GHz. The test with radio sources involves only geometry, so it is independent of cosmological models. Since the observed radio luminosities systematically increase with redshift, we do not assume a constant source size. Instead, we start with assuming the intensive property, luminosity density, does not evolve with redshift and then infer its evolution from the resultant DDR. We make the same assumption for both samples, and find it results in the same angular size–redshift relation. Interestingly, the resultant DDR is fully consistent with a nonexpanding universe. Imposing the DDR predicted by the expanding universe, we infer the radio luminosity density evolves as ρ L ∝ (1 + z)3. However, the perfect agreement with a nonexpanding universe under the assumption of constant luminosity densities poses a conspiracy and fine-tuning problem: the size and luminosity density of ultracompact radio sources evolve in the way that precisely mimics a nonexpanding universe.

EIGER. II. First Spectroscopic Characterization of the Young Stars and Ionized Gas Associated with Strong Hβ and [O iii] Line Emission in Galaxies at z = 5–7 with JWST

We present emission-line measurements and physical interpretations for a sample of 117 [O iii] emitting galaxies at z = 5.33–6.93, using the first deep JWST/NIRCam wide-field slitless spectroscopic observations. Our 9.7 hr integration is centered upon the z = 6.3 quasar J0100+2802—the first of six fields targeted by the EIGER survey—and covers λ = 3–4 μm. We detect 133 [O iii] doublets, but close pairs motivated by their small scale clustering excess. The galaxies are characterized by a UV luminosity M UV ∼ −19.6 (−17.7 to −22.3), stellar mass ∼108 (106.8−10.1) M ⊙, Hβ and [O iii]4960+5008 EWs ≈ 850 Å (up to 3000 Å), young ages, a highly excited interstellar medium, and low dust attenuations. These high EWs are very rare in the local universe, but we show they are ubiquitous at z ∼ 6 based on the measured number densities. The stacked spectrum reveals Hγ and [O iii]4364, which shows that the galaxies are typically dust- and metal-poor (E (B − V) = 0.1, ) with a high electron temperature (2 × 104 K) and a production efficiency of ionizing photons (ξ ion = 1025.3 Hz erg−1). We further show the existence of a strong mass–metallicity relation. The properties of the stars and gas in z ∼ 6 galaxies conspire to maximize the [O iii] output from galaxies, yielding an [O iii] luminosity density at z ≈ 6 that is significantly higher than that at z ≈ 2. Thus, [O iii] emission-line surveys with JWST prove a highly efficient method to trace the galaxy density in the Epoch of Reionization.

Exploring the impact of IMF and binary parameter stochasticity with a binary population synthesis code

ABSTRACT Low-mass star formation regions are unlikely to fully populate their initial mass functions (IMFs), leading to a deficit of massive stars. In binary stellar populations, the full range of binary separations and mass ratios will also be underpopulated. To explore the effects of stochastic sampling in the integrated light of stellar clusters, we calculate models at a broad range of cluster masses, from 102 to 107 M⊙, using a binary stellar population synthesis code. For clusters with stellar masses less than 105 M⊙, observable quantities show substantial scatter and their mean properties reflect the expected deficit of massive stars. In common with previous work, we find that purely stochastic sampling of the IMF appears to underestimate the mass of the most massive star in known clusters. However, even with this constraint, the majority of clusters likely inject sufficient kinetic energy to clear their birth clusters of gas. For quantities that directly measure the impact of the most massive stars, such as Nion, ξion, and βUV, uncertainties due to stochastic sampling dominate over those from the IMF shape or distribution of binary parameters, while stochastic sampling has a negligible effect on the stellar continuum luminosity density.

Evolution of the UV LF from z ∼ 15 to z ∼ 8 using new JWST NIRCam medium-band observations over the HUDF/XDF

ABSTRACT We present the first constraints on the prevalence of z &amp;gt; 10 galaxies in the Hubble Ultra Deep Field (HUDF) leveraging new NIRCam observations from JEMS (JWST Extragalactic Medium-band Survey). These NIRCam observations probe redward of 1.6 μm, beyond the wavelength limit of HST, allowing us to search for galaxies to z &amp;gt; 10. These observations indicate that the highest redshift candidate identified in the HUDF09 data with HST, UDFj-39546284, has a redshift of z &amp;gt; 11.5, as had been suggested in analyses of the HUDF12/XDF data. This has now been confirmed with JWST NIRSpec. This source is thus the most distant galaxy discovered by HST in its &amp;gt;30 yr of operation. Additionally, we identify nine other z ∼ 8–13 candidate galaxies over the HUDF, two of which are new discoveries that appear to lie at z ∼ 11–12. We use these results to characterize the evolution of the UV luminosity function (LF) from z ∼ 15 to z ∼ 8.7. While our LF results at z ∼ 8.7 and z ∼ 10.5 are consistent with previous findings over the HUDF, our new LF estimates at z ∼ 12.6 are higher than other results in the literature, potentially pointing to a milder evolution in the UV luminosity density from z ∼ 12.6. We emphasize that our LF results are uncertain given the small number of z ∼ 12.6 sources and limited volume probed. The new NIRCam data also indicate that the faint z ∼ 8–13 galaxies in the HUDF/XDF show blue UV-continuum slopes β ∼ −2.7, high specific star formation rates ∼24.5 Gyr−1, and high EW (∼1300 Å) [O iii] + H β emission, with two z ∼ 8.5 sources showing [O iii] + H β EWs of ∼2300 Å.

UV luminosity density results at z &amp;gt; 8 from the first JWST/NIRCam fields: limitations of early data sets and the need for spectroscopy

ABSTRACT We have derived luminosity functions and set constraints on the UV luminosity and SFR density from z ∼ 17 to z ∼ 8, using the three most-studied JWST/NIRCam data sets, the SMACS0723, GLASS Parallel, and CEERS fields. We first used our own selections on two independent reductions of these data sets using the latest calibrations. A total of 18 z ∼ 8, 12 z ∼ 10, 5 z ∼ 13, and 1 z ∼ 17 candidate galaxies are identified over these fields in our primary reductions, with a similar number of candidates in our secondary reductions. We then use these two reductions, applying a quantitative discriminator, to segregate the full set of z ≥ 8 candidates reported over these fields from the literature, into three different samples, ‘robust’, ‘solid’, and ‘possible’. Using all of these samples, we then derive UV LF and luminosity density results at z ≥ 8, finding substantial differences. For example, including the full set of ‘solid’ and ‘possible’ z ≥ 12 candidates from the literature, we find UV luminosity densities, which are ∼7× and ∼20× higher than relying on the ‘robust’ candidates alone. These results indicate the evolution of the UV LF and luminosity densities at z ≥ 8 is still extremely uncertain, emphasizing the need for spectroscopy and deeper NIRCam + optical imaging to obtain reliable results. Nevertheless, even with the very conservative ‘robust’ approach to selections, both from our own and those of other studies, we find the luminosity density from luminous (MUV &amp;lt; −19) galaxies to be ∼2 × larger than is easily achievable using constant star formation efficiency models, similar to what other early JWST results have suggested.

High-energy neutrino astronomy — the neutrino connections to the cosmic-ray origin: present and future

High-energy neutrino astronomy has been blooming. In addition to the possible identification of the blazar and Seyfert II galaxies as neutrino emitters, the present neutrino data has indicated some hints to characterize or constrain the origin of cosmic rays. Being motivated by the observational fact that the astrophysical neutrino background energy flux is comparable to that of ultrahigh-energy (UHE) cosmic rays, we derive the generic requirements that a major fraction of UHE cosmic ray sources must meet, if they are also responsible for the ∼ 100 TeV-energy cosmic neutrino background radiation. The source parameters characterizing the cosmic ray – neutrino unified scheme, such as the photon radiation luminosity and the cosmic ray luminosity density, suggest that the yet-unidentified cosmic ray and neutrino origins can be transient objects visible in the optical/NIR wavelength band. We propose a viable scheme of multimessenger observations to identify the sources using the neutrino multiplet detections.

Structure and kinematics of a massive galaxy at z ∼ 7

Context. Observations of the rest-frame UV emission of high-redshift galaxies suggest that the early stages of galaxy formation involve disturbed structures. Imaging the cold interstellar medium (ISM) can provide a unique view of the kinematics associated with the assembly of galaxies. Aims. In this paper, we analyze the spatial distribution and kinematics of the cold ionized gas of the normal star-forming galaxy COS-2987030247 at z = 6.8076, based on new high-resolution observations of the [C II] 158 μm line emission obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Methods. The analysis of these observations allowed us to: compare the spatial distribution and extension of the [C II] and rest-frame UV emission, model the [C II] line data-cube using the 3DBAROLO code, and measure the [C II] luminosity and star formation rate (SFR) surface densities in the galaxy subregions. Results. The system is found to be composed of a main central source, a fainter north extension, and candidate [C II] companions located 10-kpc away. We find similar rest-frame UV and [C II] spatial distributions, suggesting that the [C II] emission emerges from the star-forming regions. The agreement between the UV and [C II] surface brightness radial profiles rules out diffuse, extended [C II] emission (often called a [C II] halo) in the main galaxy component. The [C II] velocity map reveals a velocity gradient in the north-south direction, suggesting ordered motion, as commonly found in rotating-disk galaxies. However, higher resolution observations would be needed to rule out a compact merger scenario. Our model indicates an almost face-on galaxy (i ∼ 20°), with a average rotational velocity of 86 ± 16 km s−1 and a low average velocity dispersion, σ &lt; 30 km s−1. This result implies a dispersion lower than the expected value from observations and semi-analytic models of high redshift galaxies. Furthermore, our measurements indicate that COS-2987030247 and its individual regions systematically lie within the local L[CII]-SFR relationship, yet slightly below the local Σ[CII]-ΣUV relation. Conclusions. We argue that COS-2987030247 is a candidate rotating disk experiencing a short period of stability which will possibly become perturbed at later times by accreting sources.

Ultra High Energy Cosmic Ray Source Models: Successes, Challenges and General Predictions

Understanding the acceleration of Ultra High Energy Cosmic Rays is one of the great challenges of contemporary astrophysics. In this short review, we summarize the general observational constraints on their composition, spectrum and isotropy which indicate that nuclei heavier than single protons dominate their spectra above ˜ 5 EeV, that they are strongly suppressed above energies ˜ 50 EeV, and that the only significant departure from isotropy is a dipole. Constraints based upon photopion and photodisintegration losses allow their ranges and luminosity density to be estimated. Three general classes of source model are discussed - magnetospheric models (including neutron stars and black holes), jet models (including Gamma Ray Bursts, Active Galactic Nuclei and Tidal Disruption Events) and Diffusive Shock Acceleration models (involving large accretion shocks around rich clusters of galaxies). The value of constructing larger and more capable arrays to measure individual masses at the highest energies and probably identifying their sources is emphasized.

Modeling the Extragalactic Background Light and the Cosmic Star Formation History

We present an updated model for the extragalactic background light (EBL) from stars and dust, over wavelengths ≈0.1–1000 μm. This model uses accurate theoretical stellar spectra, and tracks the evolution of star formation, stellar mass density, metallicity, and interstellar dust extinction and emission in the universe with redshift. Dust emission components are treated self-consistently, with stellar light absorbed by dust reradiated in the infrared as three blackbody components. We fit our model, with free parameters associated with star formation rate and dust extinction and emission, to a wide variety of data: luminosity density, stellar mass density, and dust extinction data from galaxy surveys; and γ-ray absorption optical depth data from γ-ray telescopes. Our results strongly constraint the star formation rate density and dust photon escape fraction of the universe out to redshift z = 10, about 90% of the history of the universe. We find our model result is, in some cases, below lower limits on the z = 0 EBL intensity, and below some low-z γ-ray absorption measurements.

Death at watersheds: Galaxy quenching in low-density environments

Context.The evolution of galaxies is influenced by their local and global environment in the cosmic web. Galaxies with very old stellar populations (VO galaxies withDn(4000) index ≥1.75) mostly lie in the centres of galaxy clusters, where they evolve under the influence of processes characteristic of high-density cluster environments. However, VO galaxies have also been found in poor groups in global low-density environments between superclusters, which we call watershed regions.Aims.Our aim is to analyse the properties of galaxies in various cosmic environments with a focus on VO galaxies in the watershed regions to understand their evolution, and the origin of the large-scale morphology–density relation.Methods.We employ the Sloan Digital Sky Survey DR10 MAIN spectroscopic galaxy sample in the redshift range 0.009 ≤ z ≤ 0.200 to calculate the luminosity–density field of galaxies, to determine groups and filaments in the galaxy distribution, and to obtain data on galaxy properties. The luminosity–density field with smoothing length 8h−1Mpc,D8, characterises the global environment of galaxies. We analyse the group and galaxy contents of regions with variousD8 thresholds. We divide groups into low- and high-luminosity groups based on the highest luminosity of groups in the watershed region,Lgr ≤ 15 × 1012h−2L⊙. We compare the stellar masses, the concentration index, and the stellar velocity dispersions of quenched and star-forming galaxies among single galaxies, satellite galaxies, and the brightest group galaxies (BGGs) in various environments.Results.We show that the global density is most strongly related to the richness of galaxy groups. Its influence on the overall star formation quenching in galaxies is less strong. Correlations between the morphological properties of galaxies and the global density field are the weakest. The watershed regions withD8 &lt; 1 are populated mostly by single galaxies, constituting 70% of all galaxies there, and by low-luminosity groups. Still, approximately one-third of all galaxies in the watershed regions are VO galaxies. They have lower stellar masses, smaller stellar velocity dispersions, and stellar populations that are up to 2 Gyr younger than those of VO galaxies in other global environments. In higher density global environments (D8 &gt; 1), the morphological properties of galaxies are very similar. Differences in galaxy properties are the largest between satellites and BGGs in groups.Conclusions.Our results suggest that galaxy evolution is determined by the birthplace of galaxies in the cosmic web, and mainly by internal processes which lead to the present-day properties of galaxies. This may explain the similarity of (VO) galaxies in extremely different environments.

A super-linear ‘radio-AGN main sequence’ links mean radio-AGN power and galaxy stellar mass since z ∼ 3

Mapping the average active galactic nucleus (AGN) luminosity across galaxy populations and over time reveals important clues regarding the interplay between supermassive black hole and galaxy growth. This paper presents the demography, mean power, and cosmic evolution of radio AGN across star-forming galaxies (SFGs) of different stellar masses (ℳ*). We exploit deep VLA-COSMOS 3 GHz data to build the rest-frame 1.4 GHz AGN luminosity functions at 0.1 ≤ z ≤ 4.5 hosted in SFGs. Splitting the AGN luminosity function into different ℳ* bins reveals that, at all redshifts, radio AGN are both more frequent and more luminous in higher ℳ* than in lower ℳ* galaxies. The cumulative kinetic luminosity density exerted by radio AGN in SFGs peaks at z ∼ 2, and it is mostly driven by galaxies with 10.5 ≤ log(ℳ*/ℳ⊙) &lt; 11. Averaging the cumulative radio AGN activity across all SFGs at each (ℳ*,z) results in a ‘radio-AGN main sequence’ that links the time-averaged radio-AGN power ⟨L1.4AGN⟩ and galaxy stellar mass, in the form: log ⟨[L1.4AGN/ W Hz−1]⟩ = (20.97 ± 0.16) + (2.51 ± 0.34)⋅ log(1+z) + (1.41 ± 0.09)⋅(log[ℳ*/ℳ⊙] – 10). The super-linear dependence on ℳ*, at fixed redshift, suggests enhanced radio-AGN activity in more massive SFGs as compared to star formation. We ascribe this enhancement to both a higher radio AGN duty cycle and a brighter radio-AGN phase in more massive SFGs. A remarkably consistent ℳ* dependence is seen for the evolving X-ray AGN population in SFGs. This similarity is interpreted as possibly driven by secular cold gas accretion fuelling both radio and X-ray AGN activity in a similar fashion over the galaxy’s lifetime.