arXiv subjects

Anna-Christina Eilers

Publications and source records attributed to Anna-Christina Eilers.

At least 73 records · Page 4Linked to original sources

arXiv2025

JWST ASPIRE: How Did Galaxies Complete Reionization? Evidence for Excess IGM Transmission around ${\rm [O\,{\scriptstyle III}]}$ Emitters during Reionization

The spatial correlation between galaxies and the Ly$α$ forest provides insights into how galaxies reionized the Universe. Here, we present initial results on the spatial cross-correlation between [OIII] emitters and Ly$α$ forest at 5.4 6.5 QSO fields. Using data from five QSO fields, we find $2σ$ evidence for excess Ly$α$ forest transmission at ~20-40 cMpc around [OIII] emitters at z=5.86, indicating that [OIII] emitters reside within a highly ionized IGM. At smaller scales, the Ly$α$ forest is preferentially absorbed, suggesting gas overdensities around [OIII] emitters. Comparing with models including THESAN simulations, we interpret the observed cross-correlation as evidence for significant large-scale fluctuations of the IGM and the late end of reionization at z<6, characterized by ionized bubbles over 50 cMpc around [OIII] emitters. The required UV background necessitates an unseen population of faint galaxies around the [OIII] emitters. Furthermore, we find that the number of observed [OIII] emitters near individual transmission spikes is insufficient to sustain reionization in their surroundings, even assuming all [OIII] emitters harbour AGN with 100 % LyC escape fractions. Despite broad agreement, a careful analysis of ASPIRE and THESAN, using the observed host halo mass from the clustering of [OIII] emitters, suggests that the simulations underpredict the observed excess IGM transmission around [OIII] emitters, challenging our model of reionization. Potential solutions include larger ionized bubbles at z<6, more enhanced large-scale UV background or temperature fluctuations of the IGM, and possibly a patchy early onset of reionization at z>10. Current observational errors are dominated by cosmic variance, meaning future analyses of more QSO fields from JWST will improve the results.

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arXiv2025

Shared Stochastic Gaussian Process Latent Variable Models: A Multi-modal Generative Model for Quasar Spectra

This work proposes a scalable probabilistic latent variable model based on Gaussian processes (Lawrence, 2004) in the context of multiple observation spaces. We focus on an application in astrophysics where data sets typically contain both observed spectral features and scientific properties of astrophysical objects such as galaxies or exoplanets. In our application, we study the spectra of very luminous galaxies known as quasars, along with their properties, such as the mass of their central supermassive black hole, accretion rate, and luminosity-resulting in multiple observation spaces. A single data point is then characterized by different classes of observations, each with different likelihoods. Our proposed model extends the baseline stochastic variational Gaussian process latent variable model (GPLVM) introduced by Lalchand et al. (2022) to this setting, proposing a seamless generative model where the quasar spectra and scientific labels can be generated simultaneously using a shared latent space as input to different sets of Gaussian process decoders, one for each observation space. Additionally, this framework enables training in a missing data setting where a large number of dimensions per data point may be unknown or unobserved. We demonstrate high-fidelity reconstructions of the spectra and scientific labels during test-time inference and briefly discuss the scientific interpretations of the results, along with the significance of such a generative model.

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arXiv2025

A Quasar-Anchored Protocluster at z=6.6 in the ASPIRE Survey: I. Properties of [OIII] Emitters in a 10 Mpc Overdensity Structure

ASPIRE (A SPectroscopic survey of bIased halos in the Reionization Era) is a quasar legacy survey primarily using \textit{JWST} to target a sample of 25 $z>6$ quasars with NIRCam slitless spectroscopy and imaging. The first study in this series found evidence of a strong overdensity of galaxies around J0305$-$3150, a luminous quasar at $z=6.61$, within a single NIRCam pointing obtained in JWST Cycle 1. Here, we present the first results of a JWST Cycle 2 mosaic that covers 35 arcmin$^2$ with NIRCam imaging/WFSS of the same field to investigate the spatial extent of the putative protocluster. The F356W grism data targets [OIII]+H$β$ at $5.3 10$ cMpc.

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arXiv2024

A unique window into the Epoch of Reionisation: A double-peaked Lyman-$α$ emitter in the proximity zone of a quasar at $z\sim 6.6$

We present a study of a double-peaked Ly$α$ emitter, named LAE-11, found in the proximity zone of QSO J0910-0414 at $z\sim6.6$. We use a combination of deep photometric data from Subaru Telescope, HST, and JWST with spectroscopic data from Keck/DEIMOS, NIRCam WFSS and NIRSpec MSA to characterise the ionising and general properties of the galaxy, as well as the quasar environment surrounding it. We detect Ly$α$, H$β$, [OIII] doublet, and H$α$ emission lines in the various spectral datasets. The presence of a double-peaked Ly$α$ line in the spectrum allows us to characterise the opening angle and lifetime of the QSO as $θ_Q>49.62$° and $t_Q > 3.8\times10^5$ years. LAE-11 is a fairly bright (M$_\rm{UV} = -19.84^{+0.14}_{-0.16}$), blue galaxy with a UV slope of $β= -2.61^{+0.06}_{-0.08}$. Since the galaxy is located in a quasar-ionised region, we have a unique opportunity to measure the escape fraction of Lyman Continuum photons using the un-attenuated double-peaked Ly$α$ emission profile and its equivalent width at such high redshift. We employ diagnostics which do not rely on the detection of Ly$α$ for comparison, and find that all tracers of ionising photon leakage agree within 1$σ$ uncertainty. We measure a moderate escape of Lyman Continuum photons from LAE-11 of $f_\rm{esc}^\rm{LyC} = (8 - 33)\%$. Detections of both H$α$ and H$β$ emission lines allow for separate measurements of the ionising photon production efficiency, resulting with $\log(ξ_\rm{ion}/\rm{Hz~erg^{-1}}) = 25.59\pm0.08$ and $25.65\pm0.09$, for H$α$ and H$β$, respectively. The total ionising output of LAE-11, $\log(f_\rm{esc}^\rm{LyC}ξ_\rm{ion, Hα}/\rm{Hz~erg^{-1}}) = 24.85^{+0.24}_{-0.34}$, is higher than the value of $24.3 - 24.8$ which is traditionally assumed as needed to drive Reionisation forward.

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arXiv2024

A blazar in the epoch of reionization

Relativistic jets are thought to play a crucial role in the formation and evolution of massive galaxies and supermassive black holes. Blazars, which are quasars with jets aligned along our line of sight, provide insights into the jetted population and have been observed up to redshifts of z=6.1. Here, we report the discovery and multi-wavelength characterization of the blazar VLASS J041009.05-013919.88 at z=7 (Universe's age ~750 Myr), powered by a ~7x10^8 Msun black hole. The presence of this high-redshift blazar implies a large population of similar but unaligned jetted sources in the early Universe. Our findings suggest two possible scenarios: in one, the jet in J0410-0139 is intrinsically low-power but appears highly luminous due to relativistic beaming, suggesting that most UV-bright quasars at this redshift host jets. Alternatively, if J0410-0139 represents an intrinsically powerful radio source, there should be hundreds to thousands of radio-quiet quasars at z~7 with properties similar to J0410-0139, a prediction in tension with observed quasar densities based on their UV luminosity function. These results support the hypothesis that rapid black hole growth in the early Universe may be driven by jet-enhanced or obscured super-Eddington accretion, potentially playing a key role in forming massive black holes during the epoch of reionization.

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arXiv2024

Environmental Evidence for Overly Massive Black Holes in Low Mass Galaxies and a Black Hole - Halo Mass Relation at $z \sim 5$

JWST observations have unveiled faint active galactic nuclei (AGN) at high-redshift that provide insights on the formation of supermassive black holes (SMBHs) and their coevolution with galaxies. However, disentangling stellar from AGN light in these sources is challenging. Here, we use an empirical approach to infer the average stellar mass of 6 faint broad line (BL) Halpha emitters at z = 4 - 5 with BH masses ~ 6 (4 - 15)x10^6 Msun, with a method independent of their spectral energy distribution (SED). We use the deep JWST/NIRcam grism survey ALT to measure the over-densities around BL-Halpha emitters and around a spectroscopic reference sample of ~300 galaxies. In our reference sample, we find that Mpc-scale over-density correlates with stellar mass, while pair counts are flat below ~50 kpc due to satellites. Their large-scale environments suggest that BL-Halpha emitters are hosted by galaxies with stellar masses ~5x10^7 Msun, ~40 times lower than those inferred from galaxy-only SED fits. Adding measurements around more luminous z~6 AGNs, we find tentative correlations between line width, BH mass and the over-density, suggestive of a steep BH to halo mass relation. The main implications are (1) when BH masses are taken at face value, we confirm extremely high BH to stellar mass ratios of ~10 %, (2) the low stellar mass galaxies hosting growing SMBHs are in tension with typical hydrodynamical simulations, except those without feedback, (3) a 1 % duty cycle implied by the host mass hints at super-Eddington accretion, which may imply over-estimated SMBH masses, (4) the masses are at odds with a high stellar density interpretation of the line broadening, (5) our results imply a diversity of galaxy masses, environments and SEDs among AGN samples, depending on their luminosity.

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arXiv2024

A unified model for the clustering of quasars and galaxies at $z\approx6$

Recent observations from the EIGER JWST program have measured for the first time the quasar-galaxy cross-correlation function at $z\approx6$. The auto-correlation function of faint $z\approx6$ quasars was also recently estimated. These measurements provide key insights into the properties of quasars and galaxies at high redshift and their relation with the host dark matter halos. In this work, we interpret these data building upon an empirical quasar population model that has been applied successfully to quasar clustering and demographic measurements at $z\approx2-4$. We make use of a new, large-volume N-body simulation with more than a trillion particles, FLAMINGO-10k, to model quasars and galaxies simultaneously. We successfully reproduce observations of $z\approx6$ quasars and galaxies (i.e., their clustering properties and luminosity functions), and infer key quantities such as their luminosity-halo mass relation, the mass function of their host halos, and their duty cycle/occupation fraction. Our key findings are: (i) quasars reside on average in $\approx10^{12.5}\,{\rm M}_\odot$ halos (corresponding to $\approx5σ$ fluctuations in the initial conditions of the linear density field), but the distribution of host halo masses is quite broad; (ii) the duty cycle of (UV-bright) quasar activity is relatively low ($\approx1\%$); (iii) galaxies (that are bright in [OIII]) live in much smaller halos ($\approx10^{10.9}\,{\rm M}_\odot$) and have a larger duty cycle (occupation fraction) of $\approx13\%$. Finally, we focus on the inferred properties of quasars and present a homogeneous analysis of their evolution with redshift. The picture that emerges reveals a strong evolution of the host halo mass and duty cycle of quasars at $z\approx2-6$, and calls for new investigations of the role of quasar activity across cosmic time.

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arXiv2024

A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE): JWST Supports Earlier Reionization around [OIII] Emitters

Understanding when and how reionization happened is crucial for studying the early structure formation and the properties of first galaxies in the Universe. At $z>5.5$, the observed IGM optical depth shows a significant scatter, indicating an inhomogeneous reionization process. However, the nature of the inhomogeneous reionization remains debated. ASPIRE is a JWST Cycle 1 program that has spectroscopically identified $>400$ [OIII] emitters in 25 quasar fields at $z>6.5$. Combined with deep ground-based optical spectroscopy of ASPIRE quasars, ASPIRE program provides the current largest sample for IGM-galaxy connection studies during cosmic reionization. We present the first results of IGM effective optical depth measurements around [OIII] emitters using 14 ASPIRE quasar fields. We find the IGM transmission is tightly related with reionization-era galaxies to the extent that significant excess of Ly$α$ transmission exists around [OIII] emitters. We measure the stacked IGM effective optical depth of IGM patches associated with [OIII] emitters and find they reach the same IGM effective optical depth at least dz~0.1 ahead of those IGM patches where no [OIII] emitters are detected, supporting earlier reionization around [OIII] emitters. Our results indicate an enhancement in IGM Ly$α$ transmission around [OIII] emitters at scales beyond 25 $h^{-1}$ cMpc, consistent with the predicted topology of reionization from fluctuating UV background (UVB) models.

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arXiv2024

Fast Outflow in the Host Galaxy of the Luminous z $=$ 7.5 Quasar J1007$+$2115

James Webb Space Telescope opens a new window to directly probe luminous quasars powered by billion solar mass black holes in the epoch of reionization and their co-evolution with massive galaxies with unprecedented details. In this paper, we report the first results from the deep NIRSpec integral field spectroscopy study of a quasar at $z = 7.5$. We obtain a bolometric luminosity of $\sim$$1.8\times10^{47}$ erg s$^{-1}$ and a black hole mass of $\sim$0.7--2.5$\times10^{9}$ M$_{\odot}$ based on H$β$ emission line from the quasar spectrum. We discover $\sim$2 kpc scale, highly blueshifted ($\sim$$-$870 km/s) and broad ($\sim$1400 km/s) [O III] line emission after the quasar PSF has been subtracted. Such line emission most likely originates from a fast, quasar-driven outflow, the earliest one on galactic-scale known so far. The dynamical properties of this outflow fall within the typical ranges of quasar-driven outflows at lower redshift, and the outflow may be fast enough to reach the circumgalactic medium. Combining both the extended and nuclear outflow together, the mass outflow rate, $\sim$300 M$_{\odot}$yr, is $\sim$60%--380% of the star formation rate of the quasar host galaxy, suggesting that the outflow may expel a significant amount of gas from the inner region of the galaxy. The kinetic energy outflow rate, $\sim$3.6$\times10^{44}$ erg s$^{-1}$, is $\sim$0.2% of the quasar bolometric luminosity, which is comparable to the minimum value required for negative feedback based on simulation predictions. The dynamical timescale of the extended outflow is $\sim$1.7 Myr, consistent with the typical quasar lifetime in this era.

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arXiv2024

The THESAN project: galaxy sizes during the epoch of reionization

We investigate galaxy sizes at redshift $z\gtrsim 6$ with the cosmological radiation-magneto-hydrodynamic simulation suite THESAN(-HR). These simulations simultaneously capture the reionization of the large-scale intergalactic medium and resolved galaxy properties. The intrinsic size ($r^{\ast}_{1/2}$) of simulated galaxies increases moderately with stellar mass at $M_{\ast} \lesssim 10^{8}\,{\rm M}_{\odot}$ and decreases fast at larger masses, resulting in a hump feature at $M_{\ast}\sim 10^{8}\,{\rm M}_{\odot}$ that is insensitive to redshift. Low-mass galaxies are in the initial phase of size growth and are better described by a spherical shell model with feedback-driven gas outflows competing with the cold inflows. In contrast, massive galaxies fit better with the disk formation model. They generally experience a phase of rapid compaction and gas depletion, likely driven by internal disk instability rather than external processes. We identify four compact quenched galaxies in the $(95.5\,{\rm cMpc})^{3}$ volume of THESAN-1 at $z\simeq 6$, and their quenching follows reaching a characteristic stellar surface density akin to the massive compact galaxies at cosmic noon. Compared to observations, we find that the median UV effective radius ($R^{\rm UV}_{\rm eff}$) of simulated galaxies is at least three times larger than the observed ones at $M_{\ast}\lesssim 10^{9}\,{\rm M}_{\odot}$ or $M_{\rm UV}\gtrsim -20$ at $6 \lesssim z \lesssim 10$. This inconsistency, related to the hump feature of the intrinsic size--mass relation, persists across many other cosmological simulations with different galaxy formation models and demonstrates the potential of using galaxy morphology to constrain the physics of galaxy formation at high redshifts.

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arXiv2024

Stacking X-ray Observations of "Little Red Dots": Implications for their AGN Properties

Recent James Webb Space Telescope (JWST) observations have revealed a population of compact extragalactic objects at $z\gtrsim4$ with red near-infrared colors, which have been dubbed as ``Little Red Dots" (LRDs). The spectroscopically-selected LRDs exhibit broad H$α$ emission lines, which likely indicates that type-I active galactic nuclei (AGN) are harbored in the galaxies' dust-reddened cores. However, other mechanisms, like strong outflowing winds, could also produce broad H$α$ emission lines, and thus, the nature of LRDs is still under debate. We test the AGN hypothesis for LRDs by stacking the archival {\em Chandra} observations of 34 spectroscopically-selected LRDs. We obtain tentative detections in the soft $(0.5-2\text{ keV})$ and hard $(2-8\text{ keV})$ X-ray bands with $2.9σ$ and $3.2σ$ significance, and with $4.1σ$ significance when combining the two bands. Nevertheless, we find that the soft (hard) band $3σ$ upper limit is $\sim1$dex ($\sim 0.3$dex) lower than the expected level from the $L_\text{X}-L_{\text{H}α}$ relation for typical type-I AGNs. Our results indicate that AGN activity is indeed likely present in LRDs, though these objects have significantly different properties compared to previously identified type-I AGNs, i.e., LRDs may have intrinsically weak X-ray emissions. We find it difficult to explain the low $L_\text{X}/L_{\text{H}α}$ ratios observed in LRDs solely by absorption. It is also unlikely that fast outflows have major contributions to the broad H$α$ lines. Our findings indicate that empirical relations (e.g., for black hole mass measurements) established for typical type-I AGNs should be used with caution when analyzing the properties of LRDs.

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arXiv2024

EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at $z\gtrsim6$

We expect luminous ($M_{1450}\lesssim-26.5$) high-redshift quasars to trace the highest density peaks in the early universe. Here, we present observations of four $z\gtrsim6$ quasar fields using JWST/NIRCam in imaging and widefield slitless spectroscopy mode and report a wide range in the number of detected [OIII]-emitting galaxies in the quasars' environments, ranging between a density enhancement of $δ\approx65$ within a $2$ cMpc radius - one of the largest proto-clusters during the Epoch of Reionization discovered to date - to a density contrast consistent with zero, indicating the presence of a UV-luminous quasar in a region comparable to the average density of the universe. By measuring the two-point cross-correlation function of quasars and their surrounding galaxies, as well as the galaxy auto-correlation function, we infer a correlation length of quasars at $\langle z\rangle=6.25$ of $r_0^{\rm QQ}=22.0^{+3.0}_{-2.9}~{\rm cMpc}\,h^{-1}$, while we obtain a correlation length of the [OIII]-emitting galaxies of $r_0^{\rm GG}=4.1\pm0.3~{\rm cMpc}\,h^{-1}$. By comparing the correlation functions to dark-matter-only simulations we estimate the minimum mass of the quasars' host dark matter halos to be $\log_{10}(M_{\rm halo, min}/M_\odot)=12.43^{+0.13}_{-0.15}$ (and $\log_{10}(M_{\rm halo, min}^{\rm [OIII]}/M_\odot) = 10.56^{+0.05}_{-0.03}$ for the [OIII]-emitters), indicating that (a) luminous quasars do not necessarily reside within the most overdense regions in the early universe, and that (b) the UV-luminous duty cycle of quasar activity at these redshifts is $f_{\rm duty}\ll1$. Such short quasar activity timescales challenge our understanding of early supermassive black hole growth and provide evidence for highly dust-obscured growth phases or episodic, radiatively inefficient accretion rates.

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arXiv2024

A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE): Broad-line AGN at $z=4-5$ revealed by JWST/NIRCam WFSS

Low-luminosity AGNs with low-mass black holes (BHs) in the early universe are fundamental to understanding the BH growth and their co-evolution with the host galaxies. Utilizing JWST NIRCam Wide Field Slitless Spectroscopy (WFSS), we perform a systematic search for broad-line ${\rm Hα}$ emitters (BHAEs) at $z\approx 4-5$ in 25 fields of the ASPIRE (A SPectroscopic survey of biased halos In the Reionization Era) project, covering a total area of 275 arcmin$^2$. We identify 16 BHAEs with FWHM of the broad components spanning from $\sim$ 1000 km s$^{-1}$ to 3000 km s$^{-1}$. Assuming the broad linewidths arise due to Doppler broadening around BHs, the implied BH masses range from $10^7$ to $10^{8}~M_\odot$, with broad ${\rm Hα}$-converted bolometric luminosity of $10^{44.5}-10^{45.5}$ erg s$^{-1}$ and Eddington ratios of $0.07-0.47$. The spatially extended structure of the F200W stacked image may trace the stellar light from the host galaxies. The ${\rm Hα}$ luminosity function indicates an increasing AGN fraction towards the higher ${\rm Hα}$ luminosities. We find possible evidence for clustering of BHAEs: two sources are at the same redshift with a projected separation of 519 kpc; one BHAE appears as a composite system residing in an overdense region with three close companion ${\rm Hα}$ emitters. Three BHAEs exhibit blueshifted absorption troughs indicative of the presence of high-column-density gas. We find the broad-line and photometrically selected BHAE samples exhibit different distributions in the optical continuum slopes, which can be attributed to their different selection methods. The ASPIRE broad-line ${\rm Hα}$ sample provides a good database for future studies of faint AGN populations at high redshift.

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arXiv2024

Damping Wing-Like Features in the Stacked Ly$α$ Forest: Potential Neutral Hydrogen Islands at $z<6$

Recent quasar absorption line observations suggest that reionization may end as late as $z \approx 5.3$. As a means to search for large neutral hydrogen islands at $z<6$, we revisit long dark gaps in the Ly$β$ forest in VLT/X-Shooter and Keck/ESI quasar spectra. We stack the Ly$α$ forest corresponding to both edges of these Ly$β$ dark gaps and identify a damping wing-like extended absorption profile. The average redshift of the stacked forest is $z=5.8$. By comparing these observations with reionization simulations, we infer that such a damping wing-like feature can be naturally explained if these gaps are at least partially created by neutral islands. Conversely, simulated dark gaps lacking neutral hydrogen struggle to replicate the observed damping wing features. Furthermore, this damping wing-like profile implies that the volume-averaged neutral hydrogen fraction must be $\langle x_{\rm HI} \rangle \geq 6.1 \pm 3.9\%$ at $z = 5.8$. Our results offer robust evidence that reionization extends below $z=6$.

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arXiv2024

A quasar-galaxy merger at $z\sim 6.2$: rapid host growth via accretion of two massive satellite galaxies

We present JWST/NIRSpec Integral Field Spectroscopy in the rest-frame optical bands of the system PJ308-21, a quasar at $z=6.2342$ caught as its host galaxy interacts with companion galaxies. We detect spatially extended emission of several emission lines (H$α$, H$β$, [OIII], [NII], [SII], HeII), which we use to study the properties of the ionized phase of the interstellar medium: the source and hardness of the photoionizing radiation field, metallicity, dust reddening, electron density and temperature, and star formation. We also marginally detect continuum starlight emission associated with the companion sources. We find that at least two independent satellite galaxies are part of the system. While the quasar host appears highly enriched and obscured, with AGN-like photoionization conditions, the western companion shows minimal dust extinction, low metallicity ($Z\sim0.4$ Z$_\odot$), and star-formation driven photoionization. The eastern companion shows higher extinction and metallicity ($Z\sim0.8$ Z$_\odot$) compared to the western companion, and it is at least partially photoionized by the nearby quasar. We do not find any indication of AGN in the companion sources. Our study shows that while the quasar host galaxy is already very massive ($M_{\rm dyn}>10^{11}$ M$_\odot$), it is still rapidly building up by accreting two relatively massive ($M_{\rm star}\sim 10^{10}$ M$_\odot$) companion sources. This dataset showcases the power of JWST in exposing the build-up of massive galaxies in the first Gyr of the Universe.

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arXiv2024

3D structure of the Milky Way out to 10 kpc from the Sun. Catalogue of large molecular clouds in the Galactic Plane

Understanding the 3D structure of the Milky Way is a crucial step in deriving properties of the star-forming regions, as well as the Galaxy as a whole. We present a novel 3D map of the Milky Way plane that extends to 10 kpc distance from the Sun. We leverage the wealth of information in the near-IR APOGEE dataset and combine that with our state-of-the-art 3D mapping technique using Bayesian statistics and the Gaussian process to provide a large-scale 3D map of the dust in the Milky Way. Our map stretches across 10 kpc along both the X and Y axes, and 750 pc in the Z direction, perpendicular to the Galactic plane. Our results reveal multi-scale over-densities as well as large cavities in the Galactic plane and shed new light on the Galactic structure and spiral arms. We also provide a catalogue of large molecular clouds identified by our map with accurate distance and volume density estimates. Utilising volume densities derived from this map, we explore mass distribution across various Galactocentric radii. A general decline towards the outer Galaxy is observed, followed by local peaks, some aligning with established features like the Molecular Ring and segments of the spiral arms. Moreover, this work explores extragalactic observational effects on derived properties of molecular clouds by demonstrating the potential biases arising from column density measurements in inferring properties of these regions, and opens exciting avenues for further exploration and analysis, offering a deeper perspective on the complex processes that shape our galaxy and beyond.

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arXiv2024

A Spatially Resolved [CII] Survey of 31 $z\sim7$ Massive Galaxies Hosting Luminous Quasars

The [CII] 158 $μ$m emission line and the underlying far-infrared (FIR) dust continuum are important tracers for studying star formation and kinematic properties of early galaxies. We present a survey of the [CII] emission lines and FIR continua of 31 luminous quasars at $z>6.5$ using the Atacama Large Millimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) at sub-arcsec resolution. This survey more than doubles the number of quasars with [CII] and FIR observations at these redshifts and enables statistical studies of quasar host galaxies deep into the epoch of reionization. We detect [CII] emission in 27 quasar hosts with a luminosity range of $L_{\rm [CII]}=(0.3-5.5)\times10^9~L_\odot$ and detect the FIR continuum of 28 quasar hosts with a luminosity range of $L_{\rm FIR}=(0.5-13.0)\times10^{12}~L_\odot$. Both $L_{\rm [CII]}$ and $L_{\rm FIR}$ are correlated ($ρ\simeq0.4$) with the quasar bolometric luminosity, albeit with substantial scatter. The quasar hosts detected by ALMA are clearly resolved with a median diameter of $\sim$5 kpc. About 40% of the quasar host galaxies show a velocity gradient in [CII] emission, while the rest show either dispersion-dominated or disturbed kinematics. Basic estimates of the dynamical masses of the rotation-dominated host galaxies yield $M_{\rm dyn}=(0.1-7.5)\times10^{11}~M_\odot$. Considering our findings alongside those of literature studies, we found that the ratio between $M_{\rm BH}$ and $M_{\rm dyn}$ is about ten times higher than that of local $M_{\rm BH}-M_{\rm dyn}$ relation on average but with substantial scatter (the ratio difference ranging from $\sim$0.6 to 60) and large uncertainties.

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arXiv2024

IGM damping wing constraints on the tail end of reionisation from the enlarged XQR-30 sample

The attenuation of Ly$α$ photons by neutral hydrogen in the intergalactic medium (IGM) at $z\gtrsim5$ continues to be a powerful probe for studying the epoch of reionisation. Given a framework to estimate the intrinsic (true) Ly$α$ emission of high-$z$ sources, one can infer the ionisation state of the IGM during reionisation. In this work, we use the enlarged XQR-30 sample of 42 high-resolution and high-SNR QSO spectra between $5.8\lesssim\,z\lesssim\,6.6$ obtained with VLT/X-Shooter to place constraints on the IGM neutral fraction. This is achieved using our existing Bayesian QSO reconstruction framework which accounts for uncertainties such as the: (i) posterior distribution of predicted intrinsic Ly$α$ emission profiles (obtained via covariance matrix reconstruction of the Ly$α$ and N V emission lines from unattenuated high-ionisation emission line profiles; C IV, Si IV + O IV] and C III]) and (ii) distribution of ionised regions within the IGM using synthetic damping wing profiles drawn from a $1.6^3$ Gpc$^3$ reionisation simulation. Following careful quality control, we used 23 of the 42 available QSOs to obtain constraints/limits on the IGM neutral fraction during the tail-end of reionisation. Our median and 68th percentile constraints on the IGM neutral fraction are: $0.20\substack{+0.14\\-0.12}$ and $0.29\substack{+0.14\\-0.13}$ at $z = 6.15$~and 6.35. Further, we also report 68th percentile upper-limits of $\bar{x}_{\mathrm{H\,{\scriptscriptstyle I}}} < 0.21$, 0.20, 0.21 and 0.18 at $z = 5.8, 5.95, 6.05$~and 6.55. These results imply reionisation is still ongoing at $5.8\lesssim\,z\lesssim\,6.55$, consistent with previous results from XQR-30 (dark fraction and Ly$α$ forest) along with other observational probes considered in the literature.

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