Magnetar Models of Superluminous Supernovae from the Dark Energy Survey: Exploring Redshift Evolution

Superluminous supernovae (SLSNe) are luminous transients that can be detected to high redshifts with upcoming optical time-domain surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time. An interesting open question is whether the properties of SLSNe evolve through cosmic time. To address this question, in this paper we model the multicolor light curves of all 21 Type I SLSNe from the Dark Energy Survey (DES) with a magnetar spin-down engine, implemented in the Modular Open-Source Fitter for Transients (MOSFiT). With redshifts up to z ≈ 2, this sample includes some of the highest-redshift SLSNe. We find that the DES SLSNe span a similar range of ejecta and magnetar engine parameters as previous samples of mostly lower-redshift SLSNe (spin period P ≈ 0.79–13.61 ms, magnetic field B ≈ (0.03–7.33) × 1014 G, ejecta mass M ej ≈ 1.54–30.32 M ⊙, and ejecta velocity v ej ≈ (0.55–1.45) × 104 km s−1). The DES SLSN sample by itself exhibits the previously found negative correlation between M ej and P, with a pronounced absence of SLSNe with low ejecta mass and rapid spin. Combining our results for the DES SLSNe with 60 previous SLSNe modeled in the same way, we find no evidence for redshift evolution in any of the key physical parameters.

The evolution of the mass-metallicity relations from the VANDELS survey and the gaea Semi-Analytic model

In this work, we study the evolution of the mass-metallicity relations (MZRs) as predicted by the GAlaxy Evolution and Assembly (gaea) semi-analytic model. We contrast these predictions with recent results from the VANDELS survey, that allows us to expand the accessible redshift range for the stellar MZR up to z ∼ 3.5. We complement our study by considering the evolution of the gas-phase MZR in the same redshift range. We show that gaea is able to reproduce the observed evolution of the z < 3.5 gas-phase MZR and z < 0.7 stellar MZR, while it overpredicts the stellar metallicity at z ∼ 3.5. Furthermore, gaea also reproduces the so-called fundamental metallicity relation (FMR) between gas-phase metallicity, stellar mass and star formation rate (SFR). In particular, the gas-phase FMR in gaea is already in place at z ∼ 5 and shows almost no evolution at lower redshift. gaea predicts the existence of a stellar FMR, that is, however, characterized by a relevant redshift evolution, although its shape follows closely the gas-phase FMR. We also report additional unsolved tensions between model and data: the overall normalization of the predicted MZR agrees with observations only within ∼0.1 dex; the largest discrepancies are seen at z ∼ 3.5 where models tend to slightly overpredict observed metallicities; the slope of the predicted MZR at fixed SFR is too steep below a few M⊙ yr−1. Finally, we provide model predictions for the evolution of the MZRs at higher redshifts, that would be useful in the context of future surveys, like those that will be performed with JWST.

Submillimetre galaxies in cosmological hydrodynamical simulations – an opportunity for constraining feedback models

ABSTRACT Submillimetre galaxies (SMGs) have long posed a challenge for theorists, and self-consistently reproducing the properties of the SMG population in a large-volume cosmological hydrodynamical simulation has not yet been achieved. We use a scaling relation derived from previous simulations plus radiative transfer calculations to predict the submm flux densities of simulated SMGs drawn from cosmological simulations from the Illustris and IllustrisTNG projects based on the simulated galaxies’ star formation rates (SFRs) and dust masses, and compare the predicted number counts with observations. We find that the predicted SMG number counts based on IllustrisTNG are significantly less than observed (more than 1 dex at S850 ≳ 4 mJy). The simulation from the original Illustris project yields more SMGs than IllustrisTNG: the predicted counts are consistent with those observed at both S850 ≲ 5 mJy and S850 ≳ 9 mJy and only a factor of ∼2 lower than those observed at intermediate flux densities. The redshift distribution of SMGs with S850 > 3 mJy in IllustrisTNG is consistent with the observed distribution, whereas the Illustris redshift distribution peaks at significantly lower redshift (1.5 versus 2.8). We demonstrate that IllustrisTNG hosts fewer SMGs than Illustris because in the former, high-mass ($M_{\star }\sim 10^{11} \, \text{M}_{\odot }$) z ∼ 2–3 galaxies have lower dust masses and SFRs than in Illustris owing to differences in the subgrid models for stellar and/or active galactic nucleus feedback between the two simulations (we unfortunately cannot isolate the specific cause(s) post hoc). Our results demonstrate that because our method enables predicting SMG number counts in post-processing with a negligible computational expense, SMGs can provide useful constraints for tuning subgrid models in future large-volume cosmological simulations.

The ALPINE-ALMA [C II] survey

The [C II] 158 μm line is one of the strongest IR emission lines, which has been shown to trace the star formation rate (SFR) of galaxies in the nearby Universe, and up to z ∼ 2. Whether this is also the case at higher redshift and in the early Universe remains debated. The ALPINE survey, which targeted 118 star-forming galaxies at 4.4 < z < 5.9, provides a new opportunity to examine this question with the first statistical dataset. Using the ALPINE data and earlier measurements from the literature, we examine the relation between the [C II] luminosity and the SFR over the entire redshift range from z ∼ 4 − 8. ALPINE galaxies, which are both detected in [C II] and in dust continuum, show good agreement with the local L([CII])–SFR relation. Galaxies undetected in the continuum by ALMA are found to be over-luminous in [C II] when the UV SFR is used. After accounting for dust-obscured star formation, by an amount of SFR(IR) ≈ SFR(UV) on average, which results from two different stacking methods and SED fitting, the ALPINE galaxies show an L([CII])–SFR relation comparable to the local one. When [C II] non-detections are taken into account, the slope may be marginally steeper at high-z, although this is still somewhat uncertain. When compared homogeneously, the z > 6 [C II] measurements (detections and upper limits) do not behave very differently to the z ∼ 4 − 6 data. We find a weak dependence of L([CII])/SFR on the Lyα equivalent width. Finally, we find that the ratio L([CII])/LIR ∼ (1 − 3) × 10−3 for the ALPINE sources, comparable to that of “normal” galaxies at lower redshift. Our analysis, which includes the largest sample (∼150 galaxies) of [C II] measurements at z > 4 available so far, suggests no or little evolution of the [C II]–SFR relation over the last 13 Gyr of cosmic time.

Protoclusters at 𝓏 = 5.7: a view from the MultiDark galaxies

ABSTRACT Protoclusters, which will yield galaxy clusters at lower redshift, can provide valuable information on the formation of galaxy clusters. However, identifying progenitors of galaxy clusters in observations is not an easy task, especially at high redshift. Different priors have been used to estimate the overdense regions that are thought to mark the locations of protoclusters. In this paper, we use mimicked Ly α-emitting galaxies at z = 5.7 to identify protoclusters in the MultiDark galaxies, which are populated by applying three different semi-analytic models to the $1\, h^{-1}\, {\rm Gpc}$ MultiDark Planck2 simulation. To compare with observational results, we extend the criterion 1 (a Ly α luminosity limited sample) to criterion 2 (a match to the observed mean galaxy number density). To further statistically study the finding efficiency of this method, we enlarge the identified protocluster sample (criterion 3) to about 3500 at z = 5.7 and study their final mass distribution. The number of overdense regions and their selection probability depends on the semi-analytic models and strongly on the three selection criteria (partly by design). The protoclusters identified with criterion 1 are associated with a typical final cluster mass of $2.82\pm 0.92 \times 10^{15} \, \rm {M_{\odot }}$, which is in agreement with the prediction (within ±1σ) of an observed massive protocluster at z = 5.7. Identifying more protoclusters allows us to investigate the efficiency of this method, which is more suitable for identifying the most massive clusters: completeness ($\mathbb {C}$) drops rapidly with decreasing halo mass. We further find that it is hard to have a high purity ($\mathbb {P}$) and completeness simultaneously.

Interpreting the Spitzer/IRAC colours of 7 ≤ z ≤ 9 galaxies: distinguishing between line emission and starlight using ALMA

ABSTRACT Prior to the launch of JWST, Spitzer/IRAC photometry offers the only means of studying the rest-frame optical properties of z &gt;7 galaxies. Many such high-redshift galaxies display a red [3.6]−[4.5] micron colour, often referred to as the ‘IRAC excess’, which has conventionally been interpreted as arising from intense [O iii]+H β emission within the [4.5] micron bandpass. An appealing aspect of this interpretation is similarly intense line emission seen in star-forming galaxies at lower redshift as well as the redshift-dependent behaviour of the IRAC colours beyond z ∼ 7 modelled as the various nebular lines move through the two bandpasses. In this paper, we demonstrate that, given the photometric uncertainties, established stellar populations with Balmer (4000 Å rest frame) breaks, such as those inferred at z &gt; 9 where line emission does not contaminate the IRAC bands, can equally well explain the redshift-dependent behaviour of the IRAC colours in 7 ≲ z ≲ 9 galaxies. We discuss possible ways of distinguishing between the two hypotheses using ALMA measures of [O iii] λ88 micron and dust continuum fluxes. Prior to further studies with JWST, we show that the distinction is important in determining the assembly history of galaxies in the first 500 Myr.

Galactic ionizing photon budget during the epoch of reionization in the Cosmic Dawn II simulation

ABSTRACT Cosmic Dawn II yields the first statistically meaningful determination of the relative contribution to reionization by galaxies of different halo mass, from a fully coupled radiation-hydrodynamics simulation of the epoch of reionization large enough (∼100 Mpc) to model global reionization while resolving the formation of all galactic haloes above ${\sim}10^8 \, {\rm M}_{\odot }$. Cell transmission inside haloes is bi-modal – ionized cells are transparent, while neutral cells absorb the photons their stars produce – and the halo escape fraction fesc reflects the balance of star formation rate (SFR) between these modes. The latter is increasingly prevalent at higher halo mass, driving down fesc (we provide analytical fits to our results), whereas halo escape luminosity, proportional to fesc × SFR, increases with mass. Haloes with dark matter masses within $6\times 10^{8} \, {\rm M}_{\odot }\lt M_{\rm halo}\lt 3 \times 10^{10} \, {\rm M}_{\odot }$ produce ∼80 per cent of the escaping photons at z = 7, when the universe is 50 per cent ionized, making them the main drivers of cosmic reionization. Less massive haloes, though more numerous, have low SFRs and contribute less than 10 per cent of the photon budget then, despite their high fesc. High-mass haloes are too few and too opaque, contributing &lt;10 per cent despite their high SFRs. The dominant mass range is lower (higher) at higher (lower) redshift, as mass function and reionization advance together (e.g. at z = 8.5, xH i = 0.9, $M_{\rm halo}\lt 5\times 10^9 \, {\rm M}_{\odot }$ haloes contributed ∼80 per cent). Galaxies with UV magnitudes MAB1600 between −12 and −19 dominated reionization between z = 6 and 8.

Timing the earliest quenching events with a robust sample of massive quiescent galaxies at 2 < z < 5

ABSTRACT We present a sample of 151 massive (M* &gt; 1010 M⊙) quiescent galaxies at 2 &lt; z &lt; 5, based on a sophisticated Bayesian spectral energy distribution fitting analysis of the CANDELS UDS and GOODS-South fields. Our sample includes a robust sub-sample of 61 objects for which we confidently exclude low-redshift and star-forming solutions. We identify 10 robust objects at z &gt; 3, of which 2 are at z &gt; 4. We report formation redshifts, demonstrating that the oldest objects formed at z &gt; 6; however, individual ages from our photometric data have significant uncertainties, typically ∼0.5 Gyr. We demonstrate that the UVJ colours of the quiescent population evolve with redshift at z &gt; 3, becoming bluer and more similar to post-starburst galaxies at lower redshift. Based upon this, we construct a model for the time evolution of quiescent galaxy UVJ colours, concluding that the oldest objects are consistent with forming the bulk of their stellar mass at z ∼ 6–7 and quenching at z ∼ 5. We report spectroscopic redshifts for two of our objects at z = 3.440 and 3.396, which exhibit extremely weak Ly α emission in ultra-deep VANDELS spectra. We calculate star formation rates based on these line fluxes, finding that these galaxies are consistent with our quiescent selection criteria, provided their Ly α escape fractions are &gt;3 and &gt;10 per cent, respectively. We finally report that our highest redshift robust object exhibits a continuum break at λ ∼ 7000 Å in a spectrum from VUDS, consistent with our photometric redshift of $z_\mathrm{phot}=4.72^{+0.06}_{-0.04}$. If confirmed as quiescent, this object would be the highest redshift known quiescent galaxy. To obtain stronger constraints on the times of the earliest quenching events, high-SNR spectroscopy must be extended to z ≳ 3 quiescent objects.

Nebular-line emission during the Epoch of Reionization

ABSTRACT Nebular emission lines associated with galactic H ii regions carry information about both physical properties of the ionized gas and the source of ionizing photons as well as providing the opportunity of measuring accurate redshifts and thus distances once a cosmological model is assumed. While nebular-line emission has been extensively studied at lower redshift there are currently only few constraints within the epoch of reionization (EoR; z &gt; 6), chiefly due to the lack of sensitive near-IR spectrographs. However, this will soon change with the arrival of the Webb Telescope providing sensitive near-IR spectroscopy covering the rest-frame UV and optical emission of galaxies in the EoR. In anticipation of Webb, we combine the large cosmological hydrodynamical simulation BlueTides with photoionization modelling to predict the nebular emission-line properties of galaxies at z = 8 → 13. We find good agreement with the, albeit limited, existing direct and indirect observational constraints on equivalent widths though poorer agreement with luminosity function constraints.

Revisiting the Fraction of Radio-Loud Narrow Line Seyfert 1 Galaxies with LoTSS DR1

Radio-Loud narrow-line Seyfert 1 galaxies (NLS1s), especially the extremely radio-loud ones, are widely accepted as the jetted versions of NLS1s. We explore the radio-loud fraction for NLS1s with recently released LoTSS DR1 at 150 MHz. The radio detection rate is about 28% for LoTSS DR1. The radio detected NLS1s have lower redshift than the non-detected ones. Moreover, the 150 MHz radio luminosities of NLS1s detected by LoTSS are about two orders of magnitude weaker than those of the previous samples. By defining the radio loudness with the ratio between 150 MHz radio flux and SDSS r band flux, the radio-loud fraction is about 1% with the critical radio loudness equalling 100. Radio loudness shows no dependence on central black hole mass, while weak correlations are found between radio loudness and disk luminosity, as well as Eddington ratio.