Recent IoA Publications

arXiv:2502.03085v1 Announce Type: new Abstract: The shape of the Ly-$\alpha$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$\alpha$ and Ly-$\beta$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$\alpha$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$\alpha$ damping wing profile and Ly-$\alpha$ near zone size that simultaneously match J0148 is very low, $p<10^{-3}$. We speculate this is because the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$\alpha$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$\alpha$ near zone edge due to recent HI and HeII photo-heating. Evidence for enhanced thermal broadening in the Ly-$\alpha$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$.

arXiv:2502.02983v1 Announce Type: new Abstract: Recent work has suggested that, during reionisation, spatial variations in the ionising radiation field should produce enhanced Ly ${\alpha}$ forest transmission at distances of tens of comoving Mpc from high-redshift galaxies. We demonstrate that the Sherwood-Relics suite of hybrid radiation-hydrodynamical simulations are qualitatively consistent with this interpretation. The shape of the galaxy--Ly ${\alpha}$ transmission cross-correlation is sensitive to both the mass of the haloes hosting the galaxies and the volume averaged fraction of neutral hydrogen in the IGM, $\bar{x}_{\rm HI}$. The reported excess Ly ${\alpha}$ forest transmission on scales r ~ 10 cMpc at $\langle z \rangle \approx 5.2$ -- as measured using C IV absorbers as proxies for high-redshift galaxies -- is quantitatively reproduced by Sherwood-Relics at z = 6 if we assume the galaxies that produce ionising photons are hosted in haloes with mass $M_{\rm h}\geq 10^{10}~h^{-1}\,{\rm M}_\odot$. However, this redshift mismatch is equivalent to requiring $\bar{x}_{\rm HI}\sim 0.1$ at $z\simeq 5.2$, which is inconsistent with the observed Ly ${\alpha}$ forest effective optical depth distribution. We speculate this tension may be partly resolved if the minimum C IV absorber host halo mass at z > 5 is larger than $M_{\rm h}=10^{10}~h^{-1}\,{\rm M}_\odot$. After reionisation completes, relic IGM temperature fluctuations will continue to influence the shape of the cross-correlation on scales of a few comoving Mpc at $4 \leq z \leq 5$. Constraining the redshift evolution of the cross-correlation over this period may therefore provide further insight into the timing of reionisation.

arXiv:2502.00576v2 Announce Type: replace Abstract: Measuring the properties of planets younger than about 50 Myr helps to test different planetary formation and evolution models. NASA's Transiting Exoplanet Survey Satellite (TESS) has observed nearly the entire sky, including a wide range of star-forming regions and young stellar clusters, expanding our census of the newborn planet population. In this work, we present the discovery of the TIC 88785435 planetary system located in the Upper-Centaurus Lupus (UCL) region of the Scorpius-Centaurus OB association (Sco-Cen) and a preliminary survey of the planet population within Sco-Cen. TIC 88785435 is a pre-main sequence, K7V dwarf ($M_\star = 0.72M_\odot$, $R_\star = 0.91R_\odot$, $T_\mathrm{eff}$ = 3998K, V = 11.7 mag) located within the bounds of UCL. We investigate the distribution of rotation periods measured from the TESS long-cadence data and the Halpha and Li abundances from the spectra of TIC 88785435. TESS long-candence data reveal that TIC 88785435 hosts a transiting super-Neptune ($R_b = 5.03R_\oplus$, P = 10.51 days), TIC 88785435 b. Ground-based follow-up validates the planetary nature of TIC 88785435 b. Using the TESS data, we perform a preliminary survey to investigate how TIC 88785435 b compares to the population of newly born planets located within Sco-Cen.

arXiv:2502.02647v1 Announce Type: new Abstract: The field of high redshift galaxy formation has been revolutionised by JWST, which is yielding unprecedented insights on galaxy assembly at early times. Our key aim is to study the physical mechanisms that can explain the unexpected abundance of bright galaxies at $z \geq 11$, as well as their metal enrichment and spectral properties. We also use recent data to determine the key sources of reionisation. To do so, we implement cold gas fractions and star formation efficiencies derived from the SPHINX20 high-resolution radiation-hydrodynamics simulation into DELPHI, a semi-analytic model that tracks the assembly of dark matter halos and their baryonic components from $z \sim 4.5-40$. In addition, we explore two different methodologies to boost galaxy luminosities at $z \geq 11$: a stellar initial mass function (IMF) that becomes increasingly top-heavy with decreasing metallicity and increasing redshift (eIMF model), and star formation efficiencies that increase with increasing redshift (eSFE model). Our key findings are: (i) both the eIMF and eSFE models can explain the abundance of bright galaxies at $z \geq 11$; (ii) dust attenuation plays an important role for the bright-end of the UV LF at $z \leq 11$; (iii) the mass-metallicity relation is in place as early as $z \sim 17$ in all models although its slope is model-dependent; (iv) within the spread of both models and observations, all of our models are in good agreement with current estimates of $\beta$ slopes at $z \sim 5-17$ and Balmer break strengths at $z \sim 6-10$; (v) in the eIMF model, galaxies at $z\geq12$ or with $\rm{M_{UV}}\geq-18$ show values of $\xi_{\rm{ion}} \sim 10^{25.55}~{\rm [Hz~erg^{-1}]}$, twice larger than in other models; (vi) star formation in galaxies below $10^{9}\rm{M_{\odot}}$ is the key driver of reionisation, providing the bulk ($\sim 85\%$) of ionising photons down to its midpoint at $z \sim 7$.