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Lutz Wisotzki

Publications and source records attributed to Lutz Wisotzki.

At least 19 recordsLinked to original sources
arXiv2026

Two domains of extended Lyman-alpha emission around galaxies: from local radiation to environmental regulation

We examine the relation between extended Ly$α$ halos around high-redshift galaxies and the main factors responsible for driving the emission in such halos, in particular at distances around and beyond one virial radius $r_\mathrm{vir}$. To reach the required surface brightness sensitivity we take advantage of the MUSE eXtremely Deep Field (MXDF) survey, allowing us to probe levels as faint as $\sim 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ in individual Ly$α$ halos. Our sample consists of the 21 apparently core- and halo-brightest (yet intrinsically low luminosity $\log_{10}$L$_{\mathrm{Ly}α} < 42.3$ erg s$^{-1}$) Ly$α$ emitters (LAEs) in the MXDF at $3<z<4$, with typical virial radii around 20 kpc. We measure their radial surface brightness profiles out to 50 kpc (more than $2r_{\mathrm{vir}}$) and investigate the correlations between surface brightness and internal (star formation rates of the host galaxies, SFR) or external influences (environmental density, $δ+1$). We find a clear break in these correlations at radii around or just below $1r_{\mathrm{vir}}$. Below this break the emission correlates tightly with SFR (as expected) and not at all with $δ+1$. Beyond $\sim 1r_\mathrm{vir}$(20 kpc) we observe the opposite trend with no dependence on SFR, but an emerging correlation with $δ+1$. We compare our measurements with the expected integrated surface brightness from ultrafaint, individually undetected LAEs and find that the latter is insufficient to drive the observed correlation. We conclude that Ly$α$ emission from the outer halos is regulated by the surrounding environment, but originates mostly from diffuse gas rather than discrete sources.

astro-ph.GA↗
arXiv2026

Lyman-alpha haloes in the aftermath of reionisation

We present a comparative study of Ly$α$ haloes (LAHs) around low-luminosity (L$_{\mathrm{Ly}α}\lesssim 10^{42}$ erg s$^{-1}$) Ly$α$-emitting galaxies (LAEs) at very high redshifts $z\geq6$ and a reference sample at $z\sim 3$ covering a similar Ly$α$ luminosity and host galaxy stellar mass range. Using data from the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO VLT, we extracted the samples such that at the different redshifts we obtain the same intrinsic surface brightness sensitivity, accounting for cosmological dimming. We detect extended Ly$α$ emission around 6 out of 18 high-$z$ LAEs in the MUSE eXtremely Deep Field (MXDF), more than doubling the number of known such objects at $z\geq6$. We obtain an only slightly higher individual LAH detection fraction of 40% among the lower redshift comparison sample. Yet the typical exponential scale lengths at $z\geq6$ are three times smaller than those at $z\sim3$. Stacking the LAEs with undetected haloes gives again drastically different results for the two samples, with a highly significant halo detection at $z\sim 3$ but no trace of extended Ly$α$ emission at $z\geq6$. We also find the Ly$α$ spectral line widths of the high-$z$ sample to be $\sim$2.5 smaller in comparison to the lower redshift objects. We discuss the potential mechanisms driving such strong changes. In a reionisation-driven scenario the higher neutral fraction in the intergalactic and circumgalactic media might lead to substantial scattering losses of escaping Ly$α$ radiation, leaving detectable only emission from the vicinity of the star-forming regions. In an alternative scenario the LAH properties might be linked more closely to the evolution of their host galaxies than previously thought.

astro-ph.GA↗
arXiv2026

HETDEX Public Data Release 1: Source Catalog 2 and Data Cubes from ~90 sq deg of Integral-Field Optical Spectroscopy

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is a wide-field, integral-field spectroscopic survey designed to map the large-scale distribution of Lyman-alpha emitting galaxies (LAEs) at 1.88 < z < 3.52 and constrain dark energy at cosmic noon. Using the 10-m Hobby-Eberly Telescope and the Visible Integral-Field Replicable Unit (IFU) Spectrograph, HETDEX obtains >35,000 spectra per exposure over 3500-5500 Å at R~800 with ~1.8 arcsec image quality, enabling an untargeted census of emission-line galaxies across 540 sq deg. We present HETDEX Public Data Release 1 (PDR1), comprising 431,713 IFU observations covering 86.67 sq deg of noncontiguous sky in the Spring (13h, +51°) and Fall (1.5h, 0°) fields, along with legacy regions (COSMOS, GOODS-N, NEP, SA22). PDR1 includes the HETDEX Public Source Catalog 2 (HPSC2), an expanded and reprocessed version of Mentuch Cooper et al. (2023) incorporating four additional years of data, improved quality control, and new machine learning classifiers. HPSC2 contains 426,654 LAEs, 491,411 [O II] emitters, 19,457 low-z galaxies, 18,303 active galactic nuclei, and 150,608 stars, providing coordinates, redshifts or stellar velocities, and 1D spectra for each source. Because the data cubes use local sky subtraction optimized for faint emission-line detection, they are not suited for absolute surface-brightness measurements or very extended nearby galaxies. Appendix materials include the full detection catalog, the 1.6 million-candidate LAE sample, and raw detection databases. All products are publicly accessible through the HETDEX data portal (https://hetdex.org/data-results/), including access to a public JupyterLab. HPSC2 is also publicly available via Zenodo (DOI: 10.5281/zenodo.19581262).

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arXiv2026

Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-Power Spectrum

We present a measurement of the Lyman-$α$ (Ly$α$) intensity mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of the Ly$α$ intensity and Ly$α$-emitting galaxies (LAEs) in a redshift range of $1.9 < z < 3.5$. We calculate the intensity from HETDEX spectra that do not contain any detected LAEs above a signal-to-noise ratio of $5.5$. To produce a power spectrum model and its covariance matrix, we simulate the data using lognormal mocks for the LAE catalog and Ly$α$ intensity in redshift space. The simulations include the HETDEX sensitivity, selection function, and mask. The measurements yield the product of the LAE bias, the intensity bias, the mean intensity of undetected sources, and the ratio of the actual and fiducial redshift-space distortion parameters, $b_\mathrm{g} b_I \langle I \rangle \bar{F}_{\rm RSD} / \bar{F}^{\rm fid}_{\rm RSD}= (6.7 \pm 3.1)$, $(11.7 \pm 1.4)$, and $(8.3 \pm 1.5) \times 10^{-22} \, \text{erg}\, \text{s}^{-1} \, \text{cm}^{-2} \, \text{arcsec}^{-2} \, \text{Å}^{-1}$ in three redshift bins centered at $\bar z=2.1$, 2.6, and 3.2, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Ly$α$ radiative transfer. They are, however, significantly smaller than previous results from cross-correlations of quasars with Ly$α$ intensity. These results demonstrate the statistical power of HETDEX for Ly$α$ intensity mapping and pave the way for a more comprehensive analysis. They will also be useful for constraining models of Ly$α$ emission from galaxies used in modern cosmological simulations of galaxy formation and evolution.

astro-ph.CO↗
arXiv2026

Lyα Nebulae in HETDEX: The Largest Statistical Census Bridging Lyα Halos and Blobs across Cosmic Noon

The Hobby-Eberly Dark Energy Experiment (HETDEX) is an untargeted ~540 deg^2 spectroscopic survey of Lyα emission in the 1.9 < z < 3.5 Universe. In surface brightness, this survey reaches 1σ Lyα sensitivities of approximately 2-5 x 10^-18 erg s^-1 cm^-2 arcsec^-2, allowing large samples of extended Lyα nebulae (LAN) to be studied. We selected a sample of 70,691 Lyα-emitting galaxies (LAEs) with an emission-line signal-to-noise ratio greater than 6 and modeled the Lyα emission as a point-source component with an optional exponential envelope. Half (~47.5%) of the LAE sample (33,612 objects) exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Lyα flux and luminosity. Their isophotal areas range from 10-130 arcsec^2 (median 15 arcsec^2), with integrated Lyα fluxes from 6-2000 x 10^-17 erg s^-1 cm^-2 (median 20 x 10^-17 erg s^-1 cm^-2). Comparison between point-spread-function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates the total Lyα flux by ~30% on average, reflecting the substantial halo contribution in extended sources. Approximately 420 LANs are found per deg^2 over 79.5 deg^2 of non-contiguous sky. About 12% of resolved sources show active galactic nuclei signatures and are bright in Lyα and continuum. The remaining 88% span a wide range of morphologies and often lack continuum counterparts. Exponential scale lengths show no strong correlation with Lyα flux or luminosity (median 11.6 +/- 1.9 kpc). Only 2.9% of the full S/N > 6 LAE population with ancillary data have radio counterparts, but 64% of those are found to be extended, with the radio fraction increasing with Lyα size.

astro-ph.GA↗
arXiv2026

First statistical constraints on galactic scale outflows properties traced by their extended Mg II emission with MUSE

Galaxies evolve within vast gaseous halos that fuel star formation and carry signatures of feedback-driven outflows. Deep integral field data have enabled the study of MgII halos, which trace galaxy-scale outflows in emission, but their faintness has limited studies to single-object analyses. Here, we present the first statistical study of MgII-emitting halos using deep MUSE observations of 47 star-forming galaxies at $0.7<z<2.0$. Building on our previous work, where we developed and applied an outflow modeling framework for a single MgII halo, we now extend this approach to a larger sample, enabling robust population-level insights on the properties of circumgalactic outflows traced by their extended MgII emission. We detect extended emission out to tens of kiloparsecs and model the outflows as an ensemble of radially accelerating shells. Galaxies with MgII outflows tend to have higher SFRs, sSFRs, and younger stellar populations, consistent with star-formation-driven winds. The observations are consistent with winds that accelerate linearly with radius, from launching velocities of ~60 km/s up to maximum velocities that correlate with stellar mass and reach ~490 km/s. Their inner regions are highly opaque, and we find a tentative trend between stellar mass and central optical depth. The opening angle of the outflow shows some dependency on the host-galaxy stellar mass, with less massive galaxies showing primarily wide opening angles, and more massive galaxies showing a broader range of values, with both wide and narrow opening angles. The distribution of the spatial extent of MgII halos exhibits a clear peak at half-light radius (HLR) of ~5 kpc, with an extended tail of larger HLR values, up to ~20 kpc. Compact halo sizes (HLR $< 8$ kpc) correlate with stellar mass, but extended halos do not, which could suggest a difference in the powering mechanism between compact and extended halos.

astro-ph.GA↗
arXiv2026

Multi-spin stellar velocity maps of the most massive galaxies

(Abridged) We present stellar kinematics of the MUSE Most Massive Galaxies (M3G) Survey, comprising 25 galaxies brighter than -25.7 mag in the Ks-band and stellar mass above ~6x10^11 Msun. Galaxies are divided between the brightest cluster galaxies (BCGs) and lower-ranked (in brightness) galaxies (non-BCGs) in three rich galaxy clusters within the core of the Shapley super cluster. We find several velocity maps with rich kinematic structure, including multiple spin reversals within the region encompassing central two effective radii, typically associated with BCGs. The majority of BCGs show rotation around the major-axis, at least in one of the visible velocity components. These kinematic structures are possible only if galaxies have non-axisymmetric shapes and contain several orbital families with both prograde and retrograde rotations. There are six fast rotators in the M3G sample, all among non-BCGs, and typically ranked below the 3rd brightest galaxy. Based on the properties of the h3 Gauss-Hermite moment, fast rotation can be linked to the dominance of prograde rotating short-axis tubes in the orbital distribution. Slow rotators are BCGs or the second and sometimes third brightest galaxies, indicating that the galaxy mass (brightness) is not the only driver of low spin, but that the location within the local environment also plays a role. Slow rotators, as evidenced from their multi-spin velocity maps, require more complex orbital structures. Furthermore, some BCGs show kinematic evidence for a secondary component at larger radii, likely not in equilibrium with the main galaxy and possibly made of stars accreted from other cluster galaxies. Multi-spin velocity maps, low angular momentum and additional kinematic components highlight the difference in the evolutionary histories of BCGs (including 2nd ranked galaxies) and non-BCGs.

astro-ph.GA↗
arXiv2024

MusE GAs FLOw and Wind (MEGAFLOW) XIII. Cool gas traced by MgII around isolated galaxies

The circumgalactic medium (CGM) is a key component needed to understand the physical processes governing the flows of gas around galaxies. Quantifying its evolution and its dependence on galaxy properties is particularly important for our understanding of accretion and feedback mechanisms. We select a volume-selected sample of 66 {\it isolated} star-forming galaxies (SFGs) at $0.4< z <1.5$ with $\log(M_\star/M_{\odot})> 9$ from the MusE GAs FLOw and Wind (MEGAFLOW) survey. Using MgII 2796,2803 absorptions in background quasars, we measure the covering fraction $f_c$ and quantify how the cool gas profile depends on galaxy properties (such as star-formation rate (SFR), stellar mass ($M_\star$) or azimuthal angle relative to the line of sight) and how these dependencies evolve with redshift. The MgII covering fraction of isolated galaxies is a strong function of impact parameter, and is steeper than previously reported. The impact parameter $b_{50}$ at which $f_c = $50\% is $b_{50}=50\pm7$kpc ($65\pm7$ kpc) for $W_r^{2796}>$0.5 Å($W_r^{2796}>0.1$ Å), respectively. It is weakly correlated with SFR ($\propto$ SFR$^{0.08\pm0.09}$) and decreases with cosmic time ($\propto (1+z)^{0.8 \pm 0.7}$), contrary to the expectation of increasingly larger halos with time. The covering fraction is also higher along the minor axis than along the major axis at the $\approx 2 σ$ level. The CGM traced by \MgII{} is similar across the isolated galaxy population. Indeed, among the isolated galaxies with an impact parameter below 55 kpc, all have associated MgII absorption with $W_r^{2796}>$0.3Å, resulting in a steep covering fraction $f_c(b)$.

astro-ph.GA↗
arXiv2024

The MUSE eXtremely Deep Field: Detections of circumgalactic SiII* emission at z>~2

The circumgalactic medium (CGM) serves as a baryon reservoir that connects galaxies to the intergalactic medium and fuels star formation. The spatial distribution of the metal-enriched cool CGM has not yet been directly revealed at cosmic noon (z~2-4), as bright emission lines at these redshifts are not covered by optical integral field units. To remedy this situation, we aim for the first-ever detections and exploration of extended SiII* emission (low-ionization state, LIS), referred to as ``SiII* halos'', at redshifts ranging from z=2 to 4 as a means to trace the metal-enriched cool CGM. We use a sample of 39 galaxies with systemic redshifts of z=2.1-3.9 measured with the [CIII] doublet in the MUSE Hubble Ultra Deep Field catalog, which contains integration times spanning from ~30 to 140 hours. We search for extended SiII*1265, 1309, 1533 emission (fluorescent lines) around individual galaxies. We also stack a subsample of 14 UV-bright galaxies. We report five individual detections of SiII*1533 halos. We also confirm the presence of SiII*1533 halos in stacks for the subsample containing UV-bright sources. The other lines do not show secure detections of extended emission in either individual or stacking analyses. These detections may imply that the presence of metal-enriched CGM is a common characteristic for UV-bright galaxies. To investigate whether the origin of SiII* is continuum pumping as suggested in previous studies, we check the consistency of the equivalent width (EW) of SiII* emission and the EW of SiII absorption for the individual halo object with the most reliable detection. We confirm the equivalence, suggesting that photon conservation works for this object and pointing toward continuum pumping as the source of SiII*. We also investigate SiII* lines in a RAMSES-RT zoom-in simulation including continuum pumping and find ubiquitous presence of extended halos.

astro-ph.GA↗
arXiv2024

A galactic outflow traced by its extended Mg II emission out to a $\sim30$ kpc radius in the Hubble Ultra Deep Field with MUSE

We report the discovery of a rare Mg II $λ$$λ$ 2796, 2803 doublet emission halo around a star forming galaxy with $\log (M_\star$/M$_\odot) = 10.3 \pm 0.3$ at $z=0.737$ in deep (9.94 h) VLT/MUSE data from the MUSE-HUDF mosaic. While the central region prominently displays an absorption-dominated Mg II doublet, characterized by discernible P-Cyg features, our examination reveals a remarkably extended Mg II emission, spanning approximately $\sim30$ kpc from the central galaxy. We introduce a simple outflow radiative transfer modeling scheme based on the Sobolev approximation, and we employ a Bayesian Monte Carlo Markov Chain (MCMC) fitting to find the best-fitting parameters that match our data. The model reproduces several key features of the observed Mg II halo and allows us to constrain the kinematics and geometry of the outflowing gas. Our data are consistent with a biconical wind whose velocity increases with radius, pointing nearly towards the observer, with an opening angle of $59\pm4^{\circ}$ In general, we find that our outflow model performs better in the inner regions of the galactic wind ($\lesssim 10$ kpc $\approx 6$ half-light radii), reaching a velocity of $\sim120$ km s$^{-1}$ at 10 kpc from the central galaxy. However, discrepancies between the data and the model in the outer regions suggest the possible influence of additional mechanisms, such as inflows, satellite interactions, or turbulence, which might significantly shape the circumgalactic medium (CGM) of galaxies at larger impact parameters. This analysis underscores the complexity of galactic outflows and encourages further exploration of the processes governing the dynamics of galactic winds through spatially resolved studies of the CGM.

astro-ph.GA↗
arXiv2024

The Intrinsic Distribution of Lyman-$α$ Halos

The emission and escape of Lyman-$α$ photons from star-forming galaxies is determined through complex interactions between the emitted photons and a galaxy's interstellar and circumgalactic gas, causing Lyman-$α$ emitters (LAEs) to commonly appear not as point sources but in spatially extended halos with complex spectral profiles. We develop a 3D spatial-spectral model of Lyman-$α$ halos (LAHs) to replicate LAH observations in integral field spectroscopic studies, such as those made with VLT/MUSE. The profile of this model is a function of 6 key halo properties: the halo- and compact-source exponential scale lengths ($r_{sH}$ and $r_{sC}$), the halo flux fraction ($f_H$), the compact component ellipticity ($q$), the spectral line width ($σ$), and the spectral line skewness parameter ($γ$). Placing a series of model LAHs into datacubes reflecting observing conditions in the MUSE UDF-Mosaic survey, we test their detection recoverability and determine that $σ$, $r_{sH}$, and $f_H$ are expected to have the most significant effect on the detectability of the overall LAH at a given central wavelength and intrinsic line luminosity. We develop a general selection function model spanning a grid of these halo parameters, and with a sample of 145 UDF-Mosaic LAHs with measured halo properties, we derive completeness-corrected, intrinsic distributions of the values of $σ$, $r_{sH}$, and $f_H$ for $3<z<5$ LAHs. We present best-fit functional forms of the distributions, and a $σ$ distribution corrected for instrumental line-spread function (LSF) broadening, and thereby show the physical line spread distribution of the intrinsic population. Finally, we discuss implications of these distributions for Ly$α$ emission through the circumgalactic medium, finding that observations undercount LAHs with extended halo scale lengths compared to the intrinsic population.

astro-ph.GA↗
arXiv2024

Spatially-resolved Spectroscopic Analysis of Ly$α$ Haloes: Radial Evolution of the Ly$α$ Line Profile out to 60 kpc

The extended Ly$α$ haloes (LAHs) have been found to be prevalent around high-redshift star-forming galaxies. However, the origin of the LAHs is still a subject of debate. Spatially resolved analysis of Ly$α$ profiles provides an important diagnostic. We analyse the average spatial extent and spectral variation of the circumgalactic LAHs by stacking a sample of 155 Ly$α$ emitters (LAEs) at redshift $3<z<4$ in the MUSE Extremely Deep Field. Our analysis reveals that, with respect to the Ly$α$ line of the target LAE, the peak of the Ly$α$ line at large distances becomes increasingly more blueshifted up to a projected distance of 60 kpc ($\approx 3 \times$ virial radius), with a velocity offset of $\approx$ 250 km/s. This trend is evident in both the mean and median stacks, suggesting that it is a general property of our LAE sample, which typically has a Ly$α$ luminosity $\mathrm{\approx 10^{41.1} erg\,s^{-1}}$. However, due to the absence of systemic redshift data, it remains unclear whether the Ly$α$ line peak at large projected distances is less redshifted compared to the inner regions or truly blueshifted with respect to the systemic velocity. We explore various scenarios to explain the large-scale kinematics of the Ly$α$ line.

astro-ph.GA↗
arXiv2024

Median Surface Brightness Profiles of Lyman-$α$ Haloes in the MUSE Extremely Deep Field

We present the median surface brightness profiles of diffuse Ly$α$ haloes (LAHs) around star-forming galaxies by stacking 155 spectroscopically confirmed Ly$α$ emitters (LAEs) at 3<z<4 in the MUSE Extremely Deep Field (MXDF), with median Ly$α$ luminosity $\mathrm{L_{Lyα} \approx 10^{41.1} erg\,s^{-1}}$. After correcting for a systematic surface brightness offset we identified in the datacube, we detect extended Ly$α$ emission out to a distance of 270 kpc. The median Ly$α$ surface brightness profile shows a power-law decrease in the inner 20 kpc, and a possible flattening trend at larger distance. This shape is similar for LAEs with different Ly$α$ luminosities, but the normalisation of the surface brightness profile increases with luminosity. At distances over 50 kpc, we observe strong overlap of adjacent LAHs, and the Ly$α$ surface brightness is dominated by the LAHs of nearby LAEs. We find no clear evidence of redshift evolution of the observed Ly$α$ profiles when comparing with samples at 4<z<5 and 5<z<6. Our results are consistent with a scenario in which the inner 20 kpc of the LAH is powered by star formation in the central galaxy, while the LAH beyond a radius of 50 kpc is dominated by photons from surrounding galaxies.

astro-ph.GA↗
arXiv2024

Large-scale excess HI absorption around $z\approx4$ galaxies detected in a background galaxy spectrum in the MUSE eXtremely Deep Field

Observationally mapping the relation between galaxies and the intergalactic medium (IGM) is of key interest for studies of cosmic reionization. Diffuse hydrogen gas has typically been observed in HI Lyman-$α$ (Ly$α$) absorption in the spectra of bright background quasars. However, it is important to extend these measurements to background galaxies as quasars become increasingly rare at high redshift and rarely probe closely separated sight-lines. Here we use deep integral field spectroscopy in the MUSE eXtremely Deep Field to demonstrate the measurement of the Ly$α$ transmission at $z\approx4$ in absorption to a background galaxy at $z=4.77$. The HI transmission is consistent with independent quasar sight-lines at similar redshifts. Exploiting the high number of spectroscopic redshifts of faint galaxies (500 between $z=4.0-4.7$ within a radius of 8 arcmin) that are tracers of the density field, we show that Ly$α$ transmission is inversely correlated with galaxy density, i.e. transparent regions in the Ly$α$ forest mark under-dense regions at $z\approx4$. Due to large-scale clustering, galaxies are surrounded by excess HI absorption over the cosmic mean out to 4 cMpc/h. We also find that redshifts from the peak of the Ly$α$ line are typically offset from the systemic redshift by +170 km/s. This work extends results from $z\approx 2 - 3$ to higher redshifts and demonstrates the power of deep integral field spectroscopy to simultaneously measure the ionization structure of the IGM and the large-scale density field in the early Universe.

astro-ph.GA↗
arXiv2024

MUSEQuBES: Mapping the distribution of neutral hydrogen around low-redshift galaxies

We present a detailed study of cool, neutral gas traced by Lya around 4595 z<0.5 galaxies using stacks of background quasar spectra. The galaxies are selected from our MUSEQuBES low-z survey along with data from the literature. These galaxies, with a median stellar mass of log (M*/Msun)= 10.0, are probed by 184 background quasars giving rise to 5054 quasar-galaxy pairs. The median impact parameter is b = 1.5 pMpc (median b/Rvir=10.4) with 204 (419) quasar-galaxy pairs probing b/Rvir < 1 (2). We find excess absorption out to at least ~ 15 Rvir transverse distance and ~ 600 km/s along the line of sight. We show that the median stacked profile for the full sample, dominated by the pairs with b > Rvir, can be explained by a galaxy-absorber two-point correlation function with r0 = 7.6 pMpc and gamma = -1.57. There are strong indications that the inner regions (< Rvir) of the rest equivalent width profile are better explained by a log-linear (or a Gaussian) relation whereas the outer regions are well described by a power-law, consistent with galaxy-absorber large-scale clustering. Using a sub-sample of 339 galaxies (442 quasar-galaxy pairs, median b/Rvir = 1.6) with star formation rate measurements, we find that the Lya absorption is significantly stronger for star-forming galaxies compared to passive galaxies, but only within the virial radius. The Lya absorption at b ~ Rvir for a redshift-controlled sample peaks at M* ~ 10^9 Msun~ (Mhalo ~ 10^11 Msun).

astro-ph.GA↗
arXiv2023

Bipolar Outflows out to 10~kpc for Massive Galaxies at Redshift $z\approx 1$

Galactic outflows are believed to play a critical role in the evolution of galaxies by regulating their mass build-up and star formation. Theoretical models assumes bipolar shapes for the outflows that extends well into the circumgalctic medium (CGM), up to tens of kpc perpendicular to the galaxies. They have been directly observed in the local Universe in several individual galaxies, e.g., around the Milky Way and M82. At higher redshifts, cosmological simulations of galaxy formation predict an increase in the frequency and efficiency of galactic outflows due to the increasing star formation activity. Outflows are responsible for removing potential fuel for star formation from the galaxy, while at the same enriching the CGM and the intergalactic medium. These feedback processes, although incorporated as key elements of cosmological simulations, are still poorly constrained on CGM scales. Here we present an ultra-deep MUSE image of the mean MgII emission surrounding a sample of galaxies at z~1 that strongly suggests the presence of outflowing gas on physical scales of more than 10kpc. We find a strong dependence of the detected signal on the inclination of the central galaxy, with edge-on galaxies clearly showing enhanced MgII emission along the minor axis, while face-on galaxies display much weaker and more isotropic emission. We interpret these findings as supporting the idea that outflows typically have a bipolar cone geometry perpendicular to the galactic disk. We demonstrate that the signal is not dominated by a few outliers. After dividing the galaxy sample in subsamples by mass, the bipolar emission is only detected in galaxies with stellar mass $\mathrm{M_* \gtrsim 10^{9.5} M_\odot}$.

astro-ph.GA↗
arXiv2023

HETDEX Public Source Catalog 1 -- Stacking 50K Lyman Alpha Emitters

We describe the ensemble properties of the $1.9 < z < 3.5$ Lyman Alpha Emitters (LAEs) found in the HETDEX survey's first public data release, HETDEX Public Source Catalog 1 (Mentuch Cooper et al. 2023). Stacking the low-resolution ($R \sim$ 800) spectra greatly increases the signal-to-noise ratio, revealing spectral features otherwise hidden by noise, and we show that the stacked spectrum is representative of an average member of the set. The flux limited, Ly$α$ signal-to-noise ratio restricted stack of 50K HETDEX LAEs shows the ensemble biweight ``average" $z \sim 2.6$ LAE to be a blue (UV continuum slope $\sim -2.4$ and E(B-V) $< 0.1$), moderately bright (M$_{\text{UV}} \sim -19.7$) star forming galaxy with strong Ly$α$ emission (log $L_{Lyα}$ $\sim$ 42.8 and $W_λ$(Ly$α$) $\sim$ 114Å), and potentially significant leakage of ionizing radiation. The restframe UV light is dominated by a young, metal poor stellar population with an average age 5-15 Myr and metallicity of 0.2-0.3 Z$_{\odot}$.

astro-ph.GA↗
arXiv2023

On the evolution of the size of Lyman alpha halos across cosmic time: no change in the circumgalactic gas distribution when probed by line emission

Lyman $α$ (Ly$α$) is now routinely used as a tool for studying high-redshift galaxies and its resonant nature means it can trace neutral hydrogen around star-forming galaxies. Integral field spectrograph measurements of high-redshift Ly$α$ emitters indicate that significant extended Ly$α$ halo emission is ubiquitous around such objects. We present a sample of redshift 0.23 to 0.31 galaxies observed with the Hubble Space Telescope selected to match the star formation properties of high-$z$ samples while optimizing the observations for detection of low surface brightness Ly$α$ emission. The Ly$α$ escape fractions range between 0.7\% and 37\%, and we detect extended Ly$α$ emission around six out of seven targets. We find Ly$α$ halo to UV scale length ratios around 6:1 which is marginally lower than high-redshift observations, and halo flux fractions between 60\% and 85\% -- consistent with high-redshift observations -- when using comparable methods. However, our targets show additional extended stellar UV emission: we parametrize this with a new double exponential model. We find that this parametrization does not strongly affect the observed Ly$α$ halo fractions. We find that deeper H$α$ data would be required to firmly determine the origin of Ly$α$ halo emission, however, there are indications that H$α$ is more extended than the central FUV profile, potentially indicating conditions favorable for the escape of ionizing radiation. We discuss our results in the context of high-redshift galaxies, cosmological simulations, evolutionary studies of the circumgalactic medium in emission, and the emission of ionizing radiation.

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