arXiv subjects

Alexander Beckett

Publications and source records attributed to Alexander Beckett.

11 recordsLinked to original sources

arXiv2026

HST's Deep Blue: extremely deep UV imaging to reveal the contributors to reionization

Understanding galaxy evolution in the epoch of reionization and the effect these galaxies had on the transformation of the intergalactic medium from neutral to ionized, is a key goal of modern astrophsyics, and is central to both HST's and JWST's missions. The biggest remaining uncertainty is the escape fraction of ionizing photons from galaxies. Quantifying and understanding this at redshifts close to reionization is an objective only achievable through observations with HST, in particular, deep imaging with the WFC3/UVIS instrument to detect ionizing photons from galaxies at 2<z<4. A survey across 20 fields with supporting spectroscopy would both build up a sample similar to the state of the art at low redshift, and also overcome the uncertainty stemming from the unknown transmission of ionizing photons through the intergalactic medium. Such a program would establish the tracers of ionizing photon escape to use within the epoch of reionization and reconcile the growth of the first galaxies with the progression and topology of reionization.

astro-ph.GA↗

arXiv2026

A Comprehensive Study of Morphology and Kinematics in Extended Nebulae Around UV Luminous Quasars at $z\approx1$

Gas flows between galaxies and the circumgalactic medium (CGM) play a central role in galaxy evolution and can become observable as giant nebulae when illuminated by the quasars. We present an ensemble study of nebulae around 30 UV-luminous quasars at z=0.4-1.4 from the CUBS and MUSEQuBES surveys, 27 of which are detected in extended [O II] and/or [O III] emission. Based on a joint analysis of nebular morphology and surrounding galaxy environments, we introduce three morpho-kinematic classifications. We identify eleven irregular, large-scale (>50 kpc) systems, many of which are likely interaction-related; twelve compact host-galaxy-scale nebula, likely tracing CGM/ISM gas; and four systems with complex morphologies of uncertain origin. We introduce a quantitative measure of the spatial and kinematic association between nebulae and quasar-host group galaxies, finding a statistically significant association for ten nebulae, most of which are irregular, large-scale nebulae, consistent with qualitative analysis. Radio jets are detected in six systems, with no strong correlation found between radio activity and nebular emission. The [O II] nebulae are more asymmetric than their Ly$\alpha$ counterparts at $z>2$, but bear more similarity to H I gas observed in 21 cm around local elliptical galaxies. Blueshifted-redshifted patterns, likely tracing gas rotation, are observed in roughly 30% of the systems, though disturbed kinematics suggest that feedback may also be important. These results show that giant quasar nebulae are not a uniform class of objects, but instead arise through multiple pathways shaped by host-galaxy gas, galaxy interactions, group environments, and quasar activity, with the most striking cases associated with galaxy interactions.

astro-ph.GA↗

arXiv2026

MXDFz4.4: A LyC emitter 250Myr after the epoch of reionization and a first test of Ly-alpha morphology as a tracer of LyC escape at high redshift

Assessing the contribution of ionizing sources to cosmic reionization is a central goal of extragalactic astrophysics. Understanding and quantifying ionizing escape remains challenging near the epoch of reionization. We present the highest-redshift Lyman continuum (LyC) emitter detected to date, MXDFz4.4 at z=4.442 in the MUSE eXtremely Deep Field, observed only ~0.25Gyr after the end of reionization. A high confidence Ly-alpha line confirms the redshift. LyC flux is detected at 5.3sigma in the F435W filter with a flux of 4.2+/-0.8nJy, corresponding to a flux measurement at 5.2sigma. After correcting for the intrinsic production of LyC photons and the IGM opacity at z=4.44, we derive high escape fractions, ranging from 50 - 100%. We apply established low-redshift tracers of LyC escape and, for the first time at high redshift, promising Ly-alpha morphological tracers such as the halo fraction. SED fitting indicates the presence of a recent burst of star formation; we explore its impact on the production and escape of ionizing photons. Ly-alpha-based tracers of LyC escape reveal a complex scenario in which the recent burst strong influences LyC production and escape, combined with a more evolved stellar population. This interpretation is supported by UV diagnostics, including the star formation rate surface density and sSFR. Our results provide cautious support for the Ly-alpha halo fraction as a LyC escape tracer at high redshift. Considering the burst-driven enhancement in LyC production and escape, we conclude that stochastic star formation in the early Universe likely plays a significant role in the contribution of galaxies to cosmic reionization.

astro-ph.GA↗

arXiv2025

The Parallel Ionizing Emissivity Survey (PIE). I. Survey design and selection of candidate Lyman Continuum leakers at 3.1<z<3.5

We present the survey design and initial results from the Parallel Ionizing Emissivity (PIE) survey. PIE is a large HST survey designed to detect Lyman continuum (LyC) emitting galaxies at 3.1$<$ z $<$3.5 and stack their images in order to measure average LyC escape fractions as a function of galaxy properties. PIE has imaged 37 independent fields in three filters (F336W, F625W and F814W), of which 18 are observed with a fourth band (F475W) from the accompanying PIE+ program. We use photometric colors to select candidate Lyman Break Galaxies (LBGs) at 3.1$<$ z $<$3.5, which can be followed up using ground-based spectrographs to confirm their redshifts. Unlike previous surveys, we use many independent fields to remove biases caused by correlated absorption in the IGM. In this paper, we describe the survey design, photometric measurements, and the use of mock galaxy samples to optimize our color selection. With 3 filters, we can select a galaxy sample of which $\approx$90\% are LBGs and over 30\% lie in the 3.1$<$ z $<$3.5 range for which we can detect uncontaminated LyC emission in F336W. We also use mock IGM sightlines to measure the expected transmission of the IGM, which will allow us to determine escape fractions from our stacked galaxies. We color-select $\approx$1400 galaxies, and predict that this includes $\approx$80 LyC-emitting galaxies and $\approx$500 that we can use in stacking. Finally, we present the Keck/LRIS spectrum of a galaxy at z $\approx$ 2.99, demonstrating that we can confirm the redshifts of z $\sim$ 3 galaxies from the ground.

astro-ph.GA↗

arXiv2024

The MUSE Ultra Deep Field (MUDF). VI. The relationship between galaxy properties and metals in the circumgalactic medium

We present intial results associating galaxies in the MUSE Ultra Deep Field (MUDF) with gas seen in absorption along the line-of-sight to two bright quasars in this field, to explore the dependence of metals in the circumgalactic medium (CGM) on galaxy properties. The MUDF includes $\sim$140h of VLT/MUSE data and 90 orbits of HST/G141M grism observations alongside VLT/UVES spectroscopy of the two quasars and several bands of HST imaging. We compare the metal absorption around galaxies in this field as a function of impact parameter, azimuthal angle and galaxy metallicity across redshifts 0.5 $<$ z $<$ 3.2. Due to the depth of our data and a large field-of-view, our analysis extends to low stellar masses ($<$ $10^{7}$ M$_{\odot}$) and high impact parameters ($>$ 600 kpc). We find a correlation between absorber equivalent width and number of nearby galaxies, but do not detect a significant anti-correlation with impact parameter. Our full sample does not show any significant change in absorber incidence as a function of azimuthal angle. However, we do find a bimodality in the azimuthal angle distribution of absorption at small impact parameters ($<$2 r$_{vir}$) and around highly-star-forming galaxies, possibly indicating disk-like accretion and biconical outflows. Finally, we do not detect any systematic deviation from the fundamental metallicity relation (FMR) among galaxies with detected absorption. This work is limited by gaps in the wavelength coverage of our current data; broader-wavelength observations with JWST will allow us to unlock the full potential of the MUDF for studying the CGM.

astro-ph.GA↗

arXiv2024

High-definition imaging of a filamentary connection between a close quasar pair at z=3

Filaments connecting halos are a long-standing prediction of cold dark matter theories. We present a detection of the cosmic web emission connecting two quasar-host galaxies at redshift z ~3.22 in the MUSE Ultra Deep Field (MUDF). The very deep observations unlock a high-definition view of the filament morphology, a measure of the transition radius between the intergalactic and circumgalactic medium, and the characterization of the surface brightness profiles along the filament and in the transverse direction. Through systematic comparisons with simulations, we validate the filaments' typical density predicted in the current cold dark-matter model. Our analysis of the MUDF field, an excellent laboratory for quantitatively studying filaments in emission, opens a new avenue to constrain the physical properties of the cosmic web and to trace the distribution of dark matter on large scales.

astro-ph.CO↗

arXiv2024

UVCANDELS: The role of dust on the stellar mass-size relation of disk galaxies at 0.5 $\leq z \leq$ 3.0

We use the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields (UVCANDELS) to measure half-light radii in the rest-frame far-UV for $\sim$16,000 disk-like galaxies over $0.5\leq z \leq 3$. We compare these results to rest-frame optical sizes that we measure in a self-consistent way and find that the stellar mass-size relation of disk galaxies is steeper in the rest-frame UV than in the optical across our entire redshift range. We show that this is mainly driven by massive galaxies ($\gtrsim10^{10}$M$_\odot$), which we find to also be among the most dusty. Our results are consistent with the literature and have commonly been interpreted as evidence of inside-out growth wherein galaxies form their central structures first. However, they could also suggest that the centers of massive galaxies are more heavily attenuated than their outskirts. We distinguish between these scenarios by modeling and selecting galaxies at $z=2$ from the VELA simulation suite in a way that is consistent with UVCANDELS. We show that the effects of dust alone can account for the size differences we measure at $z=2$. This indicates that, at different wavelengths, size differences and the different slopes of the stellar mass-size relation do not constitute evidence for inside-out growth.

astro-ph.GA↗

arXiv2024

The MUSE Ultra Deep Field (MUDF). V. Characterizing the Mass-Metallicity Relation for Low Mass Galaxies at $z\sim 1$-$2$

Using more than 100 galaxies in the MUSE Ultra Deep Field with spectroscopy from the Hubble Space Telescope's Wide Field Camera 3 and the Very Large Telescope's Multi Unit Spectroscopic Explorer, we extend the gas-phase mass-metallicity relation (MZR) at $z\approx\,$1$\,$-$\,$2 down to stellar masses of M$_{\star}$ $\approx$ 10$^{7.5}$ M$_{\odot}$. The sample reaches six times lower in stellar mass and star formation rate (SFR) than previous HST studies at these redshifts, and we find that galaxy metallicities decrease to log(O/H) + 12 $\approx$ 7.8 $\pm$ 0.1 (15% solar) at log(M$_{\star}$/M$_{\odot}$) $\approx$ 7.5, without evidence of a turnover in the shape of the MZR at low masses. We validate our strong-line metallicities using the direct method for sources with [O III] $\lambda$4363 and [O III] $\lambda$1666 detections, and find excellent agreement between the techniques. The [O III] $\lambda$1666-based metallicities double existing measurements with S/N $\geq$ 5 for unlensed sources at $z~>$ 1, validating the strong-line calibrations up to $z \sim$2.5. We confirm that the MZR resides $\sim$0.3 dex lower in metallicity than local galaxies and is consistent with the fundamental metallicity relation (FMR) if the low mass slope varies with SFR. At lower redshifts ($z\sim$0.5) our sample reaches $\sim$0.5 dex lower in SFR than current calibrations and we find enhanced metallicities that are consistent with extrapolating the MZR to lower SFRs. Finally, we detect only a $\sim$0.1 dex difference in the metallicities of galaxies in groups versus isolated environments. These results are based on robust calibrations and reach the lowest masses and SFRs that are accessible with HST, providing a critical foundation for studies with the Webb and Roman Space Telescopes.

astro-ph.GA↗

arXiv2023

Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet

We examine to what extent disk and outflow models can reproduce observations of H I gas within a few virial radii of galaxies in pairs and groups. Using highly-sensitive HST/COS and FOS spectra of the Q0107 quasar triplet covering Ly$\alpha$ for z$\lesssim$1, as well as a deep galaxy redshift survey including VIMOS, DEIMOS, GMOS and MUSE data, we test simple disk and outflow models against the H I absorption along three lines-of-sight (separated by 200-500 kpc) through nine galaxy groups in this field. These can be compared with our previous results in which these models can often be fit to the absorption around isolated galaxies. Our models can reproduce $\approx$ 75$\%$ of the 28 identified absorption components within 500 km/s of a group galaxy, so most of the H I around groups is consistent with a superposition of the CGM of the individual galaxies. Gas stripped in interactions between galaxies may be a plausible explanation for some of the remaining absorption, but neither the galaxy images nor the galaxy and absorber kinematics provide clear evidence of such stripped material, and these unexplained absorbers do not preferentially occur around close pairs of galaxies. We find H I column densities typically higher than at similar impact parameters around isolated galaxies ($\approx$ 2.5$\sigma$), as well as more frequent detections of O VI than around isolated galaxies (30$\%$ of sightlines to 7$\%$).

astro-ph.GA↗

arXiv2021

The relationship between gas and galaxies at z<1 using the Q0107 quasar triplet

We study the distribution and dynamics of the circum- and intergalactic medium using a dense galaxy survey covering the field around the Q0107 system, a unique z~1 projected quasar triplet. With full Ly$α$ coverage along all three lines-of-sight from z=0.18 to z=0.73, more than 1200 galaxy spectra, and two MUSE fields, we examine the structure of the gas around galaxies on 100-1000 kpc scales. We search for H I absorption systems occurring at the same redshift (within 500 $\textrm{km}$ $\textrm{s}^{-1}$) in multiple sightlines, finding with $>$ 99.9% significance that these systems are more frequent in the observed quasar spectra than in a randomly distributed population of absorbers. This is driven primarily by absorption with column densities N(H I) $> 10^{14}$ $\textrm{cm}^{-2}$, whilst multi-sightline absorbers with lower column densities are consistent with a random distribution. Star-forming galaxies are more likely to be associated with multi-sightline absorption than quiescent galaxies. HST imaging provides inclinations and position angles for a subset of these galaxies. We observe a bimodality in the position angle of detected galaxy-absorber pairs, again driven mostly by high-column-density absorbers, with absorption preferentially along the major and minor axes of galaxies out to impact parameters of several hundred kpc. We find some evidence supporting a disk/outflow dichotomy, as H I absorbers near the projected major-axis of a galaxy show line-of-sight velocities that tend to align with the rotation of that galaxy, whilst minor-axis absorbers are twice as likely to exhibit O VI at the same redshift.

astro-ph.GA↗

arXiv2021

Pair Lines of Sight Observations of Multiphase Gas Bearing O VI in a Galaxy Environment

Using $HST$/COS observations of the twin quasar lines of sight Q$0107-025$A $\&$ Q$0107-025$B, we report on the physical properties, chemical abundances and transverse sizes of gas in a multiple galaxy environment at $z = 0.399$ across a transverse separation of $520$ kpc. The absorber towards Q$0107-025$B has $\log N(H I)/cm^{-2} \approx 16.8$ (partial Lyman limit) while the absorber towards the other sightline has $N(H I) \approx 2$ dex lower. The O VI along both sightlines have comparable column densities and broad $b$-values, whereas the low ionization lines are considerably narrower. The low ionization gas is inconsistent with the O VI when modelled assuming photoionization in a single phase. Along both the lines-of-sight, O VI and coinciding broad H I are best explained through collisional ionization in a cooling plasma with solar metallicity. Ionization models infer $1/10$-th solar metallicity for the pLLS and solar metallicity for the lower column density absorber along the other sightline. Within $\pm~250~km~s^{-1}$ and $2$ Mpc of projected distance from the sightlines 12 galaxies are identified, of which 3 are within $300$ kpc. One of them is a dwarf galaxy while the other two are intermediate mass systems at impact parameters of $ρ\sim (1-4)R_{vir}$. The O VI along both lines-of-sight could be either tracing narrow transition temperature zones at the interface of low ionization gas and the hot halo of nearest galaxy, or a more spread-out warm gas bound to the circumgalactic halo/intragroup medium. This latter scenario leads to a warm gas mass limit of $M \gtrsim 4.5 \times 10^{9}$ M$_\odot$.

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