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Kavli Institute for Cosmology, Cambridge


Analytic Approximations for the Primordial Power Spectrum with Israel Junction Conditions. (arXiv:2309.15984v1 [astro-ph.CO])

Fri, 29/09/2023 - 10:19

This work compares cosmological matching conditions used in approximating generic pre-inflationary phases of the universe. We show that the joining conditions for primordial scalar perturbations assumed by Contaldi et al. are inconsistent with the physically motivated Israel junction conditions, however, performing general relativistic matching with the aforementioned constraints results in unrealistic primordial power spectra. Eliminating the need for ambiguous matching, we look at an alternative semi-analytic model for producing the primordial power spectrum allowing for finite duration cosmological phase transitions.

DESI Complete Calibration of the Color-Redshift Relation (DC3R2): Results from early DESI data. (arXiv:2309.13109v1 [astro-ph.CO])

Tue, 26/09/2023 - 10:16

We present initial results from the Dark Energy Spectroscopic Instrument (DESI) Complete Calibration of the Color-Redshift Relation (DC3R2) secondary target survey. Our analysis uses 230k galaxies that overlap with KiDS-VIKING $ugriZYJHK_s$ photometry to calibrate the color-redshift relation and to inform photometric redshift (photo-z) inference methods of future weak lensing surveys. Together with Emission Line Galaxies (ELGs), Luminous Red Galaxies (LRGs), and the Bright Galaxy Survey (BGS) that provide samples of complementary color, the DC3R2 targets help DESI to span 56% of the color space visible to Euclid and LSST with high confidence spectroscopic redshifts. The effects of spectroscopic completeness and quality are explored, as well as systematic uncertainties introduced with the use of common Self Organizing Maps trained on different photometry than the analysis sample. We further examine the dependence of redshift on magnitude at fixed color, important for the use of bright galaxy spectra to calibrate redshifts in a fainter photometric galaxy sample. We find that noise in the KiDS-VIKING photometry introduces a dominant, apparent magnitude dependence of redshift at fixed color, which indicates a need for carefully chosen deep drilling fields, and survey simulation to model this effect for future weak lensing surveys.

Impact of Galactic dust non-Gaussianity on searches for B-modes from inflation. (arXiv:2309.09978v1 [astro-ph.CO])

Wed, 20/09/2023 - 18:37

A key challenge in the search for primordial B-modes is the presence of polarized Galactic foregrounds, especially thermal dust emission. Power-spectrum-based analysis methods generally assume the foregrounds to be Gaussian random fields when constructing a likelihood and computing the covariance matrix. In this paper, we investigate how non-Gaussianity in the dust field instead affects CMB and foreground parameter inference in the context of inflationary B-mode searches, capturing this effect via modifications to the dust power-spectrum covariance matrix. For upcoming experiments such as the Simons Observatory, we find no dependence of the tensor-to-scalar ratio uncertainty $\sigma(r)$ on the degree of dust non-Gaussianity or the nature of the dust covariance matrix. We provide an explanation of this result, noting that when frequency decorrelation is negligible, dust in mid-frequency channels is cleaned using high-frequency data in a way that is independent of the spatial statistics of dust. We show that our results hold also for non-zero levels of frequency decorrelation that are compatible with existing data. We find, however, that neglecting the impact of dust non-Gaussianity in the covariance matrix can lead to inaccuracies in goodness-of-fit metrics. Care must thus be taken when using such metrics to test B-mode spectra and models, although we show that any such problems can be mitigated by using only cleaned spectrum combinations when computing goodness-of-fit statistics.

Spatially resolved Kennicutt-Schmidt relation at z~7 and its connection with the interstellar medium properties. (arXiv:2309.07957v1 [astro-ph.GA])

Tue, 19/09/2023 - 10:13

We exploit moderately resolved [OIII], [CII] and dust continuum ALMA observations to derive the gas density ($n$), the gas-phase metallicity ($Z$) and the deviation from the Kennicutt-Schmidt (KS) relation ($\kappa_s$) on ~sub-kpc scales in the interstellar medium (ISM) of five bright Lyman Break Galaxies at the Epoch of Reionization ($z\approx 7$). To do so, we use GLAM, a state-of-art, physically motivated Bayesian model that links the [CII] and [OIII] surface brightness ($\Sigma_{\rm [CII]}$, $\Sigma_{\rm [OIII]}$) and the SFR surface density ($\Sigma_{\rm SFR}$) to $n$, $\kappa_s$, and $Z$. All five sources are characterized by a central starbursting region, where the $\Sigma_{\rm gas}$ vs $\Sigma_{\rm SFR}$ align ~10x above the KS relation ($\kappa_s\approx10$). This translates into gas depletion times in the range $t_{\rm dep}\approx 80-250$ Myr. The inner starbursting centers are characterized by higher gas density ($\log (n/{\rm cm^{-3}}) \approx 2.5-3.0$) and higher metallicity ($\log (Z/Z_{\odot}) \approx -0.5$) than the galaxy outskirts. We derive marginally negative radial metallicity gradients ($\nabla \log Z \approx -0.03 \pm 0.07$dex/kpc), and a dust temperature ($T_d\approx$32-38 K) that anticorrelates with the gas depletion time.

Fully Bayesian Forecasts with Evidence Networks. (arXiv:2309.06942v1 [astro-ph.IM])

Sun, 17/09/2023 - 18:20

Sensitivity forecasts inform the design of experiments and the direction of theoretical efforts. We argue that to arrive at representative results Bayesian forecasts should marginalize their conclusions over uncertain parameters and noise realizations rather than picking fiducial values. However, this is computationally infeasible with current methods. We thus propose a novel simulation-based forecasting methodology, which we find to be capable of providing expedient rigorous forecasts without relying on restrictive assumptions.

Metal enrichment and evolution in four z > 6.5 quasar sightlines observed with JWST/NIRSpec. (arXiv:2309.06470v1 [astro-ph.GA])

Sun, 17/09/2023 - 18:04

We present JWST/NIRSpec R$\approx$2700 spectra of four high-redshift quasars: VDES J0020-3653 (z = 6.860), DELS J0411-0907(z = 6.825), UHS J0439+1634 (z = 6.519) and ULAS J1342+0928 (z = 7.535). The exquisite data quality, signal-to-noise ratio of 50-200, and large $0.86\!~\mu{\rm m}\le \lambda \le 5.5\!~\mu{\rm m}$ spectral coverage allows us to identify between 13 and 17 intervening and proximate metal absorption line systems in each quasar spectrum, with a total number of 61 absorption-line systems detected at $2.42<z<7.48$ including the highest redshift intervening OI $\lambda$1302 and MgII systems at $z=7.37$ and $z=7.44$. We investigate the evolution of the metal enrichment in the epoch of reionization at $z>6$ and find: i) A continued increase of the low-ionization OI, CII, and SiII incidence, ii) Decreasing high-ionization CIV and SiIV incidence with a transition from predominantly high- to low-ionization at $z\approx6.0$, and iii) a constant MgII incidence across all redshifts. The observations support a change in the ionization state of the intergalactic medium in the EoR rather than a change in metallicity. The abundance ratio of [Si/O] in five $z>6$ absorption systems show enrichment signatures produced by low-mass Pop III pair instability supernovae, and possibly Pop III hypernovae. In the Gunn-Peterson troughs we detect transmission spikes where Ly$\alpha$ photons can escape. From 22 absorption systems at $z>5.7$, only a single low-ionization system out of 13 lies within 2000 km s$^{-1}$ from a spike, while four high-ionization systems out of nine lie within $\sim$2000 km s$^{-1}$ from a spike. This confirms that galaxies responsible for the heavy elements that are transported into the circumgalactic medium lie in predominantly in high-density, neutral environments, while lower density environments are ionized without being polluted by metals at $z\approx$ 6-7. [abridged]

Relative baryon-dark matter velocities in cosmological zoom simulations. (arXiv:2207.11614v2 [astro-ph.CO] UPDATED)

Sun, 17/09/2023 - 18:03

Supersonic relative motion between baryons and dark matter due to the decoupling of baryons from the primordial plasma after recombination affects the growth of the first small-scale structures. Large box sizes (greater than a few hundred Mpc) are required to sample the full range of scales pertinent to the relative velocity, while the effect of the relative velocity is strongest on small scales (less than a few hundred kpc). This separation of scales naturally lends itself to the use of `zoom' simulations, and here we present our methodology to self-consistently incorporate the relative velocity in zoom simulations, including its cumulative effect from recombination through to the start time of the simulation. We apply our methodology to a large-scale cosmological zoom simulation, finding that the inclusion of relative velocities suppresses the halo baryon fraction by $46$--$23$ per cent between $z=13.6$ and $11.2$, in qualitative agreement with previous works. In addition, we find that including the relative velocity delays the formation of star particles by $\sim 20 {~\rm Myr}$ Myr on average (of the order of the lifetime of a $\sim 9~{\rm M}_\odot$ Population III star) and suppresses the final stellar mass by as much as $79$ per cent at $z=11.2$.

Unveiling Dark Matter free-streaming at the smallest scales with high redshift Lyman-alpha forest. (arXiv:2309.04533v1 [astro-ph.CO])

Wed, 13/09/2023 - 10:10

This study introduces novel constraints on the free-streaming of thermal relic warm dark matter (WDM) from Lyman-$\alpha$ forest flux power spectra. Our analysis utilises a high-resolution, high-redshift sample of quasar spectra observed using the HIRES and UVES spectrographs ($z=4.2-5.0$). We employ a Bayesian inference framework and a simulation-based likelihood that encompasses various parameters including the free-streaming of dark matter, cosmological parameters, the thermal history of the intergalactic medium, and inhomogeneous reionization, to establish lower limits on the mass of a thermal relic WDM particle of $5.7\;\mathrm{keV}$ (at 95\% C.L.). This result surpasses previous limits from the Lyman-$\alpha$ forest through reduction of the measured uncertainties due to a larger statistical sample and by measuring clustering to smaller scales ($k_{\rm max}=0.2\;\mathrm{km^{-1}\,s}$). The approximately two-fold improvement due to the expanded statistical sample suggests that the effectiveness of Lyman-$\alpha$ forest constraints on WDM models at high redshifts are limited by the availability of high-quality quasar spectra. Restricting the analysis to comparable scales and thermal history priors as in prior studies ($k_{\rm max}<0.1\;\mathrm{km^{-1}\,s}$) lowers the bound on the WDM mass to $4.1\;\mathrm{keV}$. As the precision of the measurements increases, it becomes crucial to examine the instrumental and modelling systematics. On the modelling front, we argue that the impact of the thermal history uncertainty on the WDM particle mass constraint has diminished due to improved independent observations. At the smallest scales, the primary source of modeling systematic arises from the structure in the peculiar velocity of the intergalactic medium and inhomogeneous reionization.

Measurements of the $z > 5$ Lyman-$\alpha$ forest flux auto-correlation functions from the extended XQR-30 data set. (arXiv:2309.03341v1 [astro-ph.CO])

Fri, 08/09/2023 - 11:19

Recently, the Lyman-$\alpha$ (Ly$\alpha$) forest flux auto-correlation function has been shown to be sensitive to the mean free path of hydrogen-ionizing photons, $\lambda_{\text{mfp}}$, for simulations at $z \geq 5.4$. Measuring $\lambda_{\text{mfp}}$ at these redshifts will give vital information on the ending of reionization. Here we present the first observational measurements of the Ly$\alpha$ forest flux auto-correlation functions in ten redshift bins from $5.1 \leq z \leq 6.0$. We use a sample of 35 quasar sightlines at $z > 5.7$ from the extended XQR-30 data set, this data has signal-to-noise ratios of $> 20$ per spectral pixel. We carefully account for systematic errors in continuum reconstruction, instrumentation, and contamination by damped Ly$\alpha$ systems. With these measurements, we introduce software tools to generate auto-correlation function measurements from any simulation. For an initial comparison, we show our auto-correlation measurements with simulation models for recently measured $\lambda_{\text{mfp}}$ values and find good agreements. Further work in modeling and understanding the covariance matrices of the data is necessary to get robust measurements of $\lambda_{\text{mfp}}$ from this data.

The SAMI Galaxy Survey: impact of black hole activity on galaxy spin-filament alignments. (arXiv:2309.02794v1 [astro-ph.GA])

Thu, 07/09/2023 - 10:30

The activity of central supermassive black holes might affect the alignment of galaxy spin axes with respect to the closest cosmic filaments. We exploit the SAMI Galaxy Survey to study possible relations between black hole activity and the spin-filament alignments of stars and ionised gas separately. To explore the impact of instantaneous black hole activity, active galaxies are selected according to emission-line diagnostics. Central stellar velocity dispersion ($\sigma_c$) is used as a proxy for black hole mass and its integrated activity. We find evidence for the gas spin-filament alignments to be influenced by AGN, with Seyfert galaxies showing a stronger perpendicular alignment at fixed bulge mass with respect to galaxies where ionisation is consequence of low-ionizaition nuclear emission-line regions (LINERs) or old stellar populations (retired galaxies). On the other hand, the greater perpendicular tendency for the stellar spin-filament alignments of high-bulge mass galaxies is dominated by retired galaxies. Stellar alignments show a stronger correlation with $\sigma_c$ compared to the gas alignments. We confirm that bulge mass ($M_{bulge}$) is the primary parameter of correlation for both stellar and gas spin-filament alignments (with no residual dependency left for $\sigma_c$), while $\sigma_c$ is the most important property for secular star formation quenching (with no residual dependency left for $M_{bulge}$). These findings indicate that $M_{bulge}$ and $\sigma_c$ are the most predictive parameters of two different galaxy evolution processes, suggesting mergers trigger spin-filament alignment flips and integrated black hole activity drives star formation quenching.

The black hole mass metallicity relation and insights into galaxy quenching. (arXiv:2309.00670v1 [astro-ph.GA])

Wed, 06/09/2023 - 09:06

One of the most important questions in astrophysics is what causes galaxies to stop forming stars. Previous studies have shown a tight link between quiescence and black hole mass. Other studies have revealed that quiescence is also associated with 'starvation', the halting of gas inflows, which results in the remaining gas being used up rapidly by star formation and in rapid chemical enrichment. In this work we find the final missing link between these two findings. Using a large sample of galaxies, we uncover the intrinsic dependencies of the stellar metallicity on galaxy properties. In the case of the star-forming galaxies, the stellar metallicity is driven by stellar mass. However, for passive galaxies the stellar metallicity is primarily driven by the black hole mass, as traced by velocity dispersion. This result finally reveals the connection between previous studies, where the integrated effect of black hole feedback prevents gas inflows, starving the galaxy, which is seen by the rapid increase in the stellar metallicity, leading to the galaxy becoming passive.

GA-NIFS: JWST/NIRSpec IFU observations of HFLS3 reveal a dense galaxy group at z~6.3. (arXiv:2308.16620v1 [astro-ph.GA])

Sat, 02/09/2023 - 18:10

Massive, starbursting galaxies in the early Universe represent some of the most extreme objects in the study of galaxy evolution. One such source is HFLS3 (z~6.34), which was originally identified as an extreme starburst galaxy with mild gravitational magnification. Here, we present new observations of HFLS3 with the JWST/NIRSpec IFU in both low (PRISM/CLEAR; R~100) and high spectral resolution (G395H/290LP; R~2700), with high spatial resolution (~0.1") and sensitivity. Thanks to the combination of the NIRSpec data and a new lensing model with accurate spectroscopic redshifts, we find that the 3"x3" field is crowded, with a lensed arc (C, z=6.3425+/-0.0002), two galaxies to the south (S1 and S2, z=6.3592+/-0.0001), two galaxies to the west (W1, z=6.3550+/-0.0001; W2, z=6.3628+/-0.0001), and two low-redshift interlopers (G1, z=3.4806+/-0.0001; G2, z=2.00+/-0.01). We present spectral fits and morpho-kinematic maps for each bright emission line (e.g., [OIII]5007, Halpha, [NII]6584) from the R2700 data for all sources except G2. From a line ratio analysis, the galaxies in C are likely powered by star formation, while we cannot rule out or confirm the presence of AGN in the other high-redshift sources. We perform gravitational lens modelling, finding evidence for a two-source composition of the lensed central object and a comparable magnification factor (mu=2.1-2.4) to previous work. The projected distances and velocity offsets of each galaxy suggest that they will merge within the next ~1Gyr. Finally, we examine the dust extinction-corrected SFR of each z>6 source, finding that the total star formation (460+/-90 Msol/yr, magnification-corrected) is distributed across the six z~6.34-6.36 objects over a region of diameter ~11kpc. Altogether, this suggests that HFLS3 is not a single starburst galaxy, but instead is a merging system of star-forming galaxies in the Epoch of Reionization.

JWST CEERS & JADES Active Galaxies at z = 4-7 Violate the Local $M_\bullet-M_\star$ Relation at $>3\sigma$: Implications for Low-Mass Black Holes and Seeding Models. (arXiv:2308.12331v1 [astro-ph.GA])

Sun, 27/08/2023 - 11:06

JWST is revolutionizing our understanding of the high-z Universe by expanding the black hole horizon, looking farther and to smaller masses, and revealing the stellar light of their hosts. New detections of high-z systems offer unprecedented insights into the formation of the first black holes and their early co-evolution with galaxies. By examining JWST galaxies at z=4-7 that host H$\alpha$-detected black holes, we investigate (i) the high-z $M_\bullet-M_\star$ relation and (ii) the black hole mass distribution, especially in its low-mass range ($M_\bullet\lesssim10^{6.5} M_\odot$). With a detailed statistical analysis, our findings conclusively reveal a high-z $M_\bullet-M_\star$ relation that deviates at $>3\sigma$ confidence level from the local relation: $\log(M_\bullet/M_\odot) = -2.38^{+0.82}_{-0.83}+1.06^{+0.09}_{-0.09}\log(M_\star/M_\odot)$. Black holes are overmassive by $\sim10-100\times$ compared to their local counterparts in similar galactic hosts. This fact is not due to a selection effect in surveys. Moreover, our analysis predicts the possibility of detecting in high-z JWST surveys $5-18\times$ more black holes with $M_\bullet\lesssim10^{6.5} M_\odot$, and $10-30\times$ more with $M_\bullet \lesssim 10^{8.5} M_\odot$, compared to local relation's predictions. The lighter black holes preferentially occupy galaxies with a stellar mass of $\sim 10^{7.5}-10^8 M_\odot$. We have yet to detect these sources because (i) they may be inactive (duty cycles 1%-10%), (ii) the host overshines the AGN, or (iii) the AGN is obscured and not immediately recognizable by line diagnostics. A search of low-mass black holes in existing JWST surveys will further test the $M_\bullet-M_\star$ relation. Current JWST fields represent a treasure trove of black hole systems at z=4-7; their detection will provide crucial insights into their early evolution and co-evolution with their galactic hosts.

Investigating the characteristic shape and scatter of intergalactic damping wings during reionization. (arXiv:2308.11709v1 [astro-ph.CO])

Fri, 25/08/2023 - 09:42

Ly$\alpha$ damping wings in the spectra of bright objects at high redshift are a useful probe of the ionization state of the intergalactic medium during the reionization epoch. It has recently been noted that, despite the inhomogeneous nature of reionization, these damping wings have a characteristic shape which is a strong function of the volume-weighted average neutral hydrogen fraction of the intergalactic medium. We present here a closer examination of this finding using a simulation of patchy reionization from the Sherwood-Relics simulation suite. We show that the characteristic shape and scatter of the damping wings are determined by the average neutral hydrogen density along the line of sight, weighted by its contribution to the optical depth producing the damping wing. We find that there is a redshift dependence in the characteristic shape due to the expansion of the Universe. Finally, we show that it is possible to differentiate between the shapes of damping wings in galaxies and young (or faint) quasars at different points in the reionization history at large velocity offsets from the point where the transmission first reaches zero.

The 21-cm bispectrum from neutral hydrogen islands at z < 6. (arXiv:2308.09744v1 [astro-ph.CO])

Wed, 23/08/2023 - 09:53

Spatial variations in the Lyman-$\alpha$ forest opacity at $z<6$ seem to require a late end to cosmic reionization. In this picture, the universe contains neutral hydrogen 'islands' of up to 100 cMpc$/h$ in extent down to redshifts as low as $z\sim 5.3$. This delayed end to reionization also seems to be corroborated by various other observables. An implication of this scenario is that the power spectrum of the cosmological 21-cm signal at $z<6$ is enhanced relative to conventional reionization models by orders of magnitude. However, these neutral hydrogen islands are also predicted to be at the locations of the deepest voids in the cosmological large-scale structure. As a result, the distribution of the 21-cm signal from them is highly non-Gaussian. We derive the 21-cm bispectrum signal from these regions using high-dynamic-range radiative transfer simulations of reionization. We find that relative to conventional models in which reionization is complete at $z>6$, our model has a significantly larger value of the 21-cm bispectrum. The neutral islands also imprint a feature in the isosceles bispectrum at a characteristic scale of $\sim 1$ cMpc$^{-1}$. We also study the 21-cm bispectrum for general triangle configuration by defining a triangle index. It should be possible to detect the 21-cm bispectrum signal at $\nu\gtrsim 200$ MHz using SKA1-LOW for 1080 hours of observation, assuming optimistic foreground removal.

Population synthesis of Be X-ray binaries: metallicity dependence of total X-ray outputs. (arXiv:2308.06154v1 [astro-ph.HE])

Tue, 15/08/2023 - 12:45

X-ray binaries (XRBs) are thought to regulate cosmic thermal and ionisation histories during the Epoch of Reionisation and Cosmic Dawn ($z\sim 5-30$). Theoretical predictions of the X-ray emission from XRBs are important for modeling such early cosmic evolution. Nevertheless, the contribution from Be-XRBs, powered by accretion of compact objects from decretion disks around rapidly rotating O/B stars, has not been investigated systematically. Be-XRBs are the largest class of high-mass XRBs (HMXBs) identified in local observations and are expected to play even more important roles in metal-poor environments at high redshifts. In light of this, we build a physically motivated model for Be-XRBs based on recent hydrodynamic simulations and observations of decretion disks. Our model is able to reproduce the observed population of Be-XRBs in the Small Magellanic Cloud with appropriate initial conditions and binary stellar evolution parameters. We derive the X-ray output from Be-XRBs as a function of metallicity in the (absolute) metallicity range $Z\in [10^{-4},0.03]$. We find that Be-XRBs can contribute a significant fraction ($\sim 60\%$) of the total X-ray budget from HMXBs observed in nearby galaxies for $Z\sim 0.0003-0.02$. A similar fraction of observed ultra-luminous ($\gtrsim 10^{39}\ \rm erg\ s^{-1}$) X-ray sources can also be explained by Be-XRBs. Moreover, the predicted metallicty dependence in our fiducial model is consistent with observations, showing a factor of $\sim 8$ increase in X-ray luminosity per unit star formation rate from $Z=0.02$ to $Z=0.0003$.

JWST observations of galaxy damping wings during reionization interpreted with cosmological simulations. (arXiv:2308.05800v1 [astro-ph.GA])

Tue, 15/08/2023 - 12:42

Spectra of the highest redshift galaxies taken with JWST are now allowing us to see into the heart of the reionization epoch. Many of these observed galaxies exhibit strong damping wing absorption redward of their Lyman-$\alpha$ emission. These observations have been used to measure the redshift evolution of the neutral fraction of the intergalactic medium and sizes of ionized bubbles. However, these estimates have been made using a simple analytic model for the intergalactic damping wing. We explore the recent observations with models of inhomogeneous reionization from the Sherwood-Relics simulation suite. We carry out a comparison between the damping wings calculated from the simulations and from the analytic model. We find that although the agreement is good on the red side of the Lyman-$\alpha$ emission, there is a discrepancy on the blue side due to residual neutral hydrogen present in the simulations, which saturates the intergalactic absorption. For this reason, we find that it is difficult to reproduce the claimed observations of large bubble sizes at z ~ 7, which are driven by a detection of transmitted flux blueward of the Lyman-$\alpha$ emission. We suggest instead that the observations can be explained by a model with smaller ionized bubbles and larger intrinsic Lyman-$\alpha$ emission from the host galaxy.

A fast-rotator post-starburst galaxy quenched by supermassive black-hole feedback at z=3. (arXiv:2308.06317v1 [astro-ph.GA])

Tue, 15/08/2023 - 12:34

There is compelling evidence that the most massive galaxies in the Universe stopped forming stars due to the time-integrated feedback from their central super-massive black holes (SMBHs). However, the exact quenching mechanism is not yet understood, because local massive galaxies were quenched billions of years ago. We present JWST/NIRSpec integral-field spectroscopy observations of GS-10578, a massive, quiescent galaxy at redshift z=3.064. From the spectrum we infer that the galaxy has a stellar mass of $M_*=1.6\pm0.2 \times 10^{11}$ MSun and a dynamical mass $M_{\rm dyn}=2.0\pm0.5 \times 10^{11}$ MSun. Half of its stellar mass formed at z=3.7-4.6, and the system is now quiescent, with the current star-formation rate SFR<9 MSun/yr. We detect ionised- and neutral-gas outflows traced by [OIII] emission and NaI absorption. Outflow velocities reach $v_{\rm out}\approx$1,000 km/s, comparable to the galaxy escape velocity and too high to be explained by star formation alone. GS-10578 hosts an Active Galactic Nucleus (AGN), evidence that these outflows are due to SMBH feedback. The outflow rates are 0.14-2.9 and 30-300 MSun/yr for the ionised and neutral phases, respectively. The neutral outflow rate is ten times higher than the SFR, hence this is direct evidence for ejective SMBH feedback, with mass-loading capable of interrupting star formation by rapidly removing its fuel. Stellar kinematics show ordered rotation, with spin parameter $\lambda_{Re}=0.62\pm0.07$, meaning GS-10578 is rotation supported. This study shows direct evidence for ejective AGN feedback in a massive, recently quenched galaxy, thus clarifying how SMBHs quench their hosts. Quenching can occur without destroying the stellar disc.

Probing Ultra-late Reionization: Direct Measurements of the Mean Free Path over $5<z<6$. (arXiv:2308.04614v1 [astro-ph.CO])

Thu, 10/08/2023 - 11:03

The mean free path of ionizing photons, $\lambda_{\rm mfp}$, is a critical parameter for modeling the intergalactic medium (IGM) both during and after reionization. We present direct measurements of $\lambda_{\rm mfp}$ from QSO spectra over the redshift range $5<z<6$, including the first measurements at $z\simeq5.3$ and 5.6. Our sample includes data from the XQR-30 VLT large program, as well as new Keck/ESI observations of QSOs near $z \sim 5.5$, for which we also acquire new [C II] 158$\mu$m redshifts with ALMA. By measuring the Lyman continuum transmission profile in stacked QSO spectra, we find $\lambda_{\rm mfp} = 9.33_{-1.80}^{+2.06}$, $5.40_{-1.40}^{+1.47}$, $3.31_{-1.34}^{+2.74}$, and $0.81_{-0.48}^{+0.73}$ pMpc at $z=5.08$, 5.31, 5.65, and 5.93, respectively. Our results demonstrate that $\lambda_{\rm mfp}$ increases steadily and rapidly with time over $5<z<6$. Notably, we find that $\lambda_{\rm mfp}$ deviates significantly from predictions based on a fully ionized and relaxed IGM as late as $z=5.3$. By comparing our results to model predictions and indirect $\lambda_{\rm mfp}$ constraints based on IGM Ly$\alpha$ opacity, we find that the $\lambda_{\rm mfp}$ evolution is consistent with scenarios wherein the IGM is still undergoing reionization and/or retains large fluctuations in the ionizing UV background well below redshift six.

Planck 2013 results X. Energetic particle effects: characterization, removal, and simulation. (arXiv:1303.5071v3 [astro-ph.CO] UPDATED)

Mon, 07/08/2023 - 10:09

We describe the detection, interpretation, and removal of the signal resulting from interactions of high energy particles with the \Planck\ High Frequency Instrument (HFI). There are two types of interactions: heating of the 0.1\,K bolometer plate; and glitches in each detector time stream. The transient responses to detector glitch shapes are not simple single-pole exponential decays and fall into three families. The glitch shape for each family has been characterized empirically in flight data and these shapes have been used to remove glitches from the detector time streams. The spectrum of the count rate per unit energy is computed for each family and a correspondence is made to the location on the detector of the particle hit. Most of the detected glitches are from Galactic protons incident on the die frame supporting the micro-machined bolometric detectors. In the \Planck\ orbit at L2, the particle flux is around $5\,{\rm cm}^{-2}\,{\rm s}^{-1}$ and is dominated by protons incident on the spacecraft with energy $>$39\,MeV, at a rate of typically one event per second per detector. Different categories of glitches have different signatures in the time stream. Two of the glitch types have a low amplitude component that decays over nearly 1\,s. This component produces excess noise if not properly removed from the time-ordered data. We have used a glitch detection and subtraction method based on the joint fit of population templates. The application of this novel glitch subtraction method removes excess noise from the time streams. Using realistic simulations, we find that this method does not introduce signal bias into the \Planck\ data.