arXiv subjects

Ralf Bender

Publications and source records attributed to Ralf Bender.

At least 19 recordsLinked to original sources

arXiv2026

The future of high-resolution UV spectroscopy: Science with a UV \'Echelle spectrograph on the Habitable Worlds Observatory, or a dedicated mission

High-resolution UV spectroscopy serves a diversity of science cases, from small bodies to planets, stars, and galaxies, but is currently limited to the Hubble Space Telescope and bright targets. Major advances require increasing sensitivity by at least one order of magnitude. Here we present the UV science cases for PEGASUS (Planets, Earths, Galaxies, And Stars UV Spectrograph), a UV \'Echelle high-resolution spectrograph concept, with $R = \lambda/\delta\lambda \sim 100\,000$ (full range 10 000-140 000) and covering 90--400 nm, with a foreseen extension to at least 800 nm. PEGASUS is ideally suited for the Habitable Worlds Observatory (HWO), enabling transformative science across the UV/optical wavelength ranges. PEGASUS will be unique in high sensitivity (effective area) and high spectral resolution -- an uncharted territory -- as well as robustness, thanks to the simplicity of its design. Its UV science cases include: I) Formation and evolution of planets and their habitability: properties of exoplanets and atmospheres, protoplanetary disks, Solar System bodies; II) Stellar lives and deaths at their extremes: the first stars and the origin of the elements, compact and massive stars, Supernovae; III) Gas and metals in the baryon cycle of galaxies: the interstellar, circumgalactic, and intergalactic medium and their roles in galaxy growth. These are essential for the Astro Decadal 2020 Survey, Voyage 2050, and HWO. While this paper focuses on high-impact science enabled by UV high-resolution spectroscopy, PEGASUS will extend into the optical regime and lower spectral resolution, making it a multi-purpose, widely used, workhorse spectrograph for HWO.

astro-ph.IM↗

arXiv2026

Edgington's Combination Method for Two-Study Meta-Analysis: An Empirical Evaluation in 1226 Meta-Analyses

Two-study meta-analyses are common in evidence synthesis but pose major statistical challenges. With only two studies, the between-study variance cannot be reliably estimated, rendering standard random-effects methods unstable. Here, we investigate meta-analyses based on Edgington's p-value combination method as an alternative approach, applying it to 1226 two-study meta-analyses from the German Institute for Quality and Efficiency in Health Care (IQWiG). Like fixed-effect meta-analysis, Edgington's method is calibrated under homogeneity. However, it adapts confidence interval width to observed between-study discrepancy without requiring explicit heterogeneity estimation. In all of the examined meta-analyses, this leads to confidence intervals that contain both study-specific estimates but remain informative. Edgington's method agrees with fixed-effect meta-analysis on statistical significance (at two-sided $\alpha$ = 0.05) in 91% of all meta-analyses, but can give wider intervals when study results are discrepant and narrower intervals when results are highly consistent. Weighted extensions of Edgington's method shift point estimates toward the more precise study while preserving much of this adaptive behavior. We conclude that Edgington's method offers a principled and practically useful complement to existing approaches for two-study meta-analysis, occupying a middle ground between standard fixed-effect and random-effects approaches.

stat.AP↗

arXiv2026

Triaxial Schwarzschild Models of Brightest Cluster Galaxies with Long-Slit LBT Data

We present new long-slit stellar kinematics for a sample of 21 Brightest Cluster Galaxies (BCGs) and triaxial Schwarzschild models for 16 of these objects using our orbit modelling code SMART. The new kinematics obtained with the Large Binocular Telescope (LBT) is complemented with high-resolution photometry from HST or new AO-assisted ground-based observations also obtained at LBT and combined with wide-field imaging from the Wendelstein Observatory. These data enable robust modeling from the innermost regions - where the Supermassive Black Hole dominates the potential - to larger radii, where stars and dark matter (DM) are the primary mass contributors. As already discussed in a companion paper, we discovered 8 Ultramassive Black Holes (UMBHs, with mass $> 10^{10}$ M$_\odot$) in this BCG sample, more than doubling the number of galaxies with dynamically detected UMBHs. We show that the DM halos display a wide variety of geometries. Purely kinematical results include low central velocity dispersion with increasing profiles towards the outskirts, and the discovery of one Kinematically Decoupled Core.

astro-ph.GA↗

arXiv2025

Eight New Ultramassive Black Hole Masses confirm Best Correlation with Galaxy Core Sizes

We analyse black-hole scaling relations at the high-mass end, focusing in particular on the regime of ultra-massive black holes, $\mathrm{M}_\mathrm{BH} > 10^{10}\,\mathrm{M}_\odot$ (UMBHs). In a sample of 16 Brightest Cluster Galaxies (BCGs) without previous black-hole mass measurements we discover 8 UMBHs based on direct dynamical detections with triaxial Schwarzschild models. This first sample of triaxial black-hole mass determinations increases the number of known UMBHs by a factor of two and dramatically increases the constraints for BH mass scaling relations at the high-mass end. We find that BCGs are outliers in the canonical BH - $\sigma$ relation, while the size of their depleted cores - the central light-deficient region - is a much better unbiased predictor of the black hole mass and should be used as a proxy at the high-mass end. BCGs smoothly join the trend already established for massive core galaxies in previous studies. This also holds for tight correlations between core size and sphere-of-influence radius and core size and core density. All these relations strongly support the black-hole binary model for the formation of the centers of the most massive galaxies.

astro-ph.GA↗

arXiv2025

Galaxy Luminosity Function of the Coma Cluster from Deep $u'-g'-r'$ Wendelstein Imaging Data

We derive the $g'$ band galaxy luminosity function (GLF) of quenched resolved galaxies in the Coma cluster from a deep-imaging survey with $\approx1.5\,\mathrm{deg^2}$ around the cluster center. The dataset comprises deep $u'$-, $g'$-, and $r'$-band data obtained with the Wendelstein Wide Field Imager on the $2.1\,$m Fraunhofer Wendelstein Telescope reaching median $3\sigma$ surface brightness limits in 10" $\times$ 10" boxes of $\mathrm{ (30.0\,u',\,\,29.6\,g',\,\,28.7\,r')\,mag\,arcsec^{-2}}$. We measure structural parameters across a large dynamic range in galaxy brightness ($-24.5\,g'\,\mathrm{mag} \lessapprox M\lessapprox-11.3\,g'\,\mathrm{mag}$), from the brightest cluster galaxy to low-luminosity dwarfs, including compact dwarf galaxies and ultra-diffuse galaxies. We automatically identify more than 6000 cluster member candidates based on their membership on the quiescent sequence in the $u'-g'$ versus $g'-r'$ color-color diagram. The structural parameters of bright galaxies are obtained via isophotal modeling, and fully automated parametric image fitting for faint ones. Injection-recovery tests and two identically analyzed reference fields provide statistical corrections for completeness and contamination, yielding a representative GLF that reliably probes the faint end and may serve as a benchmark for future studies. We report a best-fit single Schechter $g'$ band GLF with $M^\star=-21.71^{+0.26}_{-0.29}\,g'\,\mathrm{mag}$, $\log_{10}(\phi^\star\,[\mathrm{deg}^{-2}\,\mathrm{mag}^{-1}])=1.355^{+0.076}_{-0.079}$, and a comparatively steep faint-end slope $\alpha=-1.444^{+0.015}_{-0.015}$. A directly matched comparison with the Coma counterpart in SLOW, a constrained cosmological simulation using CDM, shows broad agreement between the GLFs down to the simulation limit of $M = -15.5\,g'\,\mathrm{mag}$, despite a deficit of bright galaxies.

astro-ph.GA↗

arXiv2025

Modeling Tidal Streams and Tidal Tails around Galaxies Using Deep Wendelstein Imaging Data

From the $\Lambda$ cold dark matter paradigm it is expected that galaxies merge and grow in their environments. These processes form various tidal features depending on the merger mass ratio, orbital parameters, and gas richness. We inspected 170 $g'$-band Abell cluster observations from the 2.1m Fraunhofer-Teleskop Wendelstein and identify 111 of such features from which we select nine streams and five tails. A fast and innovative technique was developed for determining their photometric properties. The model is a Gaussian, including higher-order moments to describe the light profile in slices perpendicular to the elongation direction. From these models, FWHM apertures are generated. The method was developed, tested, and applied on the selected features and corresponding $g$- and $r$-band data from the Legacy Survey DR10. Regarding the novel modeling approach, we can measure surface and total brightnesses with precisions of 4% and 7%, respectively. Mean stream width precision, which also translates to the mean $R_\mathrm{e}$ along the feature is on average within 3% uncertainty. The measured streams have on average a surface brightness of $\sim26.25$ $g'$ mag arcsec$^{-2}$ and are dimmer than the tails in our sample ($\sim25.14$ $g'$ mag arcsec$^{-2}$). We infer that the progenitors of our streams can come from dwarfs, early-type galaxies or disks, based on the streams structural parameters. Furthermore, brightnesses and colors of the streams and tails are consistent with those of galaxies that populate the red sequence in the Coma cluster within $2\sigma$.

astro-ph.GA↗

arXiv2024

The VIRUS-dE Survey II: Cuspy and round halos in dwarf ellipticals -- A result of early assembly?

We analyze the dark matter (DM) halos of a sample of dwarf Ellitpicals (dE) and discuss cosmological and evolutionary implications. Using orbit modeling we recover their density slopes and, for the first time, the halo flattening. We find the `cusp-core' tension is mild, on average dEs have central slopes slightly below the Navarro Frenk White (NFW) predictions. However, the measured flattenings are still more spherical than cosmological simulations predict. Unlike brighter ETGs the total density slopes of dEs are shallower, and their average DM density does not follow their scaling relation with luminosity. Conversely, dE halos are denser and the densities steeper than in LTGs. We find average DM density and slope are strongly correlated with the environment and moderately with the angular momentum. Central, non-rotating dEs have dense and cuspy halos, whereas rotating dEs in Virgo's outskirts are more cored and less dense. This can be explained by a delayed formation of the dEs in the cluster outskirts, or alternatively, by the accumulated baryonic feedback the dEs in the outskirts have experienced during their very different star formation history. Our results suggest halo profiles are not universal (they depend on assembly conditions) and they evolve only mildly due to internal feedback. We conclude dEs in the local Universe have assembled at a higher redshift than local spirals. In these extreme conditions (e.g. star-formation, halo assembly) were very different, suggesting no new dEs are formed at present.

astro-ph.GA↗

arXiv2024

The Black Hole Mass and Photometric Components of NGC 4826

We present IR photometry and HST imaging and spectroscopy of Sab galaxy NGC 4826. Schwarzschild dynamical modeling is used to measure its central black hole mass $M$. Photometric decomposition is used to enable a comparison of $M$ to published scaling relations between black hole masses and properties of host bulges. This decomposition implies that NGC 4826 contains classical and pseudo bulges of approximately equal mass. The classical bulge has best-fit S\'ersic index $n=3.27$. The pseudobulge is made up of three parts, an inner lens ($n=0.18$ at $r\lesssim4^{\prime\prime}$), an outer lens ($n=0.17$ at $r \lesssim 45^{\prime\prime}$), and a $n=0.58$ component required to match the surface brightness between the lens components. The total $V$-band luminosity of the galaxy is $M_{VT}=-21.07$, the ratio of classical bulge to total light is $B/T\simeq0.12$, and the ratio of pseudobulge to total light is $PB/T\simeq0.13$. The outer disk is exponential ($n=1.07$) and makes up $D/T=0.75$ of the light of the galaxy. Our best-fit Schwarzschild model has a black hole mass with $1\sigma$ uncertainties of $M=8.4^{+1.7}_{-0.6}\times10^6\ M_\odot$ and a stellar $K$-band mass-to-light ratio of $\Upsilon_K=0.46\pm0.03\ M_{\odot}\ \mathrm{L}_{\odot}^{-1}$ at the assumed distance of 7.27 Mpc. Our modeling is marginally consistent with $M=0$ at the $3\sigma$ limit. These best-fit parameters were calculated assuming the black hole is located where the velocity dispersion is largest; this is offset from the maximum surface brightness, probably because of dust absorption. The black hole mass -- one of the smallest measured by modeling stellar dynamics -- satisfies the well known correlations of $M$ with the $K$-band luminosity, stellar mass, and velocity dispersion of the classical bulge only in contrast to total (classical plus pseudo) bulge luminosity.

astro-ph.GA↗

arXiv2024

The VIRUS-dE Survey I: Stars in dwarf elliptical galaxies - 3D dynamics and radially resolved stellar initial mass functions

We analyse the stellar structure of a sample of dwarf ellipticals (dE) inhabiting various environments within the Virgo cluster. Integral-field observations with a high spectral resolution allow us to robustly determine their low velocity dispersions ($\sim25$ km s$^{-1}$) and higher-order kinematic moments out to the half-light radius. We find the dEs exhibit a diversity in ages with the younger dEs being less enhanced than the older, suggesting a complex star formation history for those dEs that recently entered Virgo while others have been quenched shortly after reionization. Orbit-superposition modeling allowed us to recover viewing angles, stellar mass-to-light ratios (with gradients), as well as the intrinsic orbit structure. We find that the angular momentum of the dEs is strongly suppressed compared to ordinary early-type galaxies and correlates with the environment. Flattened dEs are so because of a suppressed kinetic energy perpendicular to their equatorial plane. Combining population and dynamical modeling results, we find an age-dependent stellar initial mass function (IMF) or, alternatively, evidence for a more extended star formation history for those galaxies that have had higher initial mass and/or inhabited lower density environments. dEs appear to have a spatially homogeneous stellar structure but the state they were `frozen' in as they stopped forming stars varies dramatically according to their initial conditions.

astro-ph.GA↗

arXiv2024

Triaxial Schwarzschild Models of NGC 708: a 10-billion solar mass black hole in a low dispersion galaxy with a Kroupa IMF

We report the discovery of a $(1.0 \pm 0.28) \times 10^{10}$ M$_\odot$ Supermassive Black Hole (BH) at the centre of NGC 708, the Brightest Cluster Galaxy of Abell 262. Such high BH masses are very rare and allow to investigate BH - host galaxy scaling relations at the high mass end, which in turn provide hints about the (co)evolution of such systems. NGC~708 is found to be an outlier in all the canonical scaling relations except for those linking the BH mass to the core properties. The galaxy mass-to-light ratio points to a Kroupa IMF rather than Salpeter, with this finding confirmed using photometry in two different bands. We perform this analysis using our novel triaxial Schwarzschild code to integrate orbits in a 5-dimensional space, using a semi-parametric deprojected light density to build the potential and non-parametric Line-of-Sight Velocity Distributions (LOSVDs) derived from long-slit spectra recently acquired at Large Binocular Telescope (LBT) to exploit the full information in the kinematic. We find that the galaxy geometry changes as a function of the radius going from prolate, nearly spherical in the central regions to triaxial at large radii, highlighting the need to go beyond constant shape profiles. Our analysis is only the second of its kind and will systematically be used in the future to hunt Supermassive Black Holes in giant ellipticals.

astro-ph.GA↗

arXiv2024

Stellar populations of massive early-type galaxies observed by MUSE

Stellar population studies of massive early-type galaxies (ETGs) suggest that the stellar initial mass function may not be universal. In particular, the centres of ETGs seem to contain an excess of low-mass dwarf stars compared to our own Galaxy. Through high resolution MUSE IFU data, we carry out a detailed study of the stellar populations of eight massive ETGs. We use full spectrum fitting to determine ages, element abundances, and IMF slopes for spatially binned spectra. We measure flat gradients in age and [Mg/Fe] ratio, as well as negative gradients in metallicity and [Na/Fe]. We detect IMF gradients in some galaxies, with the centres hosting bottom-heavy IMFs and mass excess factors between 1.5-2.5 compared to a Kroupa IMF. The IMF slope below 0.5~M$_\odot$ varies for our galaxy sample between 1-2.8, with negative radial gradients, while the IMF slope between 0.5-1~M$_\odot$ has a steep value of $\sim$3 with mildly positive gradients for most galaxies. For M87, we find excellent agreement with the dynamical M/L as a function of radius. For the other galaxies, we find systematically higher M/L from stellar populations compared to orbit-based dynamical analysis of the same data. This discrepancy increases with NaI strength, suggesting a combination of calibration issues of this line and correlated uncertainties.

astro-ph.GA↗

arXiv2023

Ultra-Diffuse Galaxies $-$ A Distinct Population? Dwarf Galaxies in the Coma Cluster and A262 from Deep $u'-g'-r'$ Wendelstein Imaging Data

In this study, we compare the structural parameters of ultra-diffuse galaxies (UDGs) to those of other dwarf galaxies and investigate whether UDGs form a distinct population. We observed deep $u'$-, $g'$-, and $r'$-band images (maximum limiting surface brightness [3$\sigma$, $10"\times10"$] $u'$ and $g'$: $\mathrm{\approx 30\,mag\,arcsec^{-2}}$; $r'$: $\mathrm{\approx 29\,mag\,arcsec^{-2}}$) of A1656 (Coma cluster) and A262 with the Wendelstein Wide Field Imager at the 2.1 m-Fraunhofer Wendelstein Telescope on the Wendelstein Observatory. We measure $u'-g'$ and $g'-r'$ colors and structural parameters using parametric fitting of tens of thousands of potential UDGs and other dwarf galaxies. Cluster members are identified and separated from diffuse background galaxies based on red sequence membership and location in the $u'-g'$ vs. $g'-r'$ color-color diagram. We find 11 UDGs in A262 and 48 UDGs in A1656. The latter is six times more than van Dokkum et al. found in the overlapping region. By comparing the structural parameters of UDGs to non-UDGs in our sample and to spheroidals from the literature, we do not find any separation in all tested parameter spaces. Instead, UDGs form the diffuse end of the already well-known spheroidal population and slightly extend it. Furthermore, we find that the UDG definition used by Koda et al. and Yagi et al. mainly extends the definition by van Dokkum et al. toward ordinary spheroidals.

astro-ph.GA↗

arXiv2023

Dynamical stellar mass-to-light ratio gradients: Evidence for very centrally concentrated IMF variations in ETGs?

Evidence from different probes of the stellar initial mass function (IMF) of massive early-type galaxies (ETGs) has repeatedly converged on IMFs more bottom-heavy than in the Milky Way (MW). This consensus has come under scrutiny due to often contradictory results from different methods on the level of individual galaxies. In particular, a number of strong lensing probes are ostensibly incompatible with a non-MW IMF. Radial gradients of the IMF -- related to gradients of the stellar mass-to-light ratio $\Upsilon$ -- can potentially resolve this issue. We construct Schwarzschild models allowing for $\Upsilon$-gradients in seven massive ETGs with MUSE and SINFONI observations. We find dynamical evidence that $\Upsilon$ increases towards the center for all ETGs. The gradients are confined to sub-kpc scales. Our results suggest that constant-$\Upsilon$ models may overestimate the stellar mass of galaxies by up to a factor 1.5. For all except one galaxy, we find a radius where the total dynamical mass has a minimum. This minimum places the strongest constraints on the IMF outside the center and appears at roughly 1 kpc. We consider the IMF at this radius characteristic for the main body of each ETG. In terms of the IMF mass-normalization $\alpha$ relative to a Kroupa IMF, we find on average a MW-like IMF $<\alpha_{main}> = 1.03 \pm 0.19$. In the centers, we find concentrated regions with increased mass normalizations that are less extreme than previous studies suggested, but still point to a Salpeter-like IMF, $<\alpha_{cen}> = 1.54 \pm 0.15$

astro-ph.GA↗

arXiv2023

Composite Bulges -- III. A Study of Nuclear Star Clusters in Nearby Spiral Galaxies

We present photometric and morphological analyses of nuclear star clusters (NSCs) -- very dense, massive star clusters present in the central regions of most galaxies -- in a sample of 33 massive disk galaxies within 20 Mpc, part of the "Composite Bulges Survey." We use data from the Hubble Space Telescope including optical (F475W and F814W) and near-IR (F160W) images from the Wide Field Camera 3. We fit the images in 2D to take into account the full complexity of the inner regions of these galaxies (including the contributions of nuclear disks and bars), isolating the nuclear star cluster and bulge components. We derive NSC radii and magnitudes in all 3 bands, which we then use to estimate NSC masses. Our sample significantly expands the sample of massive late-type galaxies with measured NSC properties. We clearly identify nuclear star clusters in nearly 80% of our galaxies, putting a lower limit on the nucleation fraction in these galaxies that is higher than previous estimates. We find that the NSCs in our massive disk galaxies are consistent with previous NSC mass-NSC radius and Galaxy Mass-NSC Mass relations. However, we also find a large spread in NSC masses, with a handful of galaxies hosting very low-mass, compact clusters. Our NSCs are aligned in PA with their host galaxy disks but are less flattened. They show no correlations with bar or bulge properties. Finally, we find the ratio of NSC to BH mass in our massive disk galaxy sample spans a factor of $\sim$300.

astro-ph.GA↗

arXiv2023

The isotropic center of NGC 5419 -- A core in formation?

With its cored surface brightness profile, the elliptical galaxy NGC 5419 appears as a typical high-mass early-type galaxy (ETG). However, the galaxy hosts two distinct nuclei in its center. We use high-signal MUSE (Multi-Unit Spectroscopic Explorer) spectral observations and novel triaxial dynamical orbit models to reveal a surprisingly isotropic central orbit distribution in NGC 5419. Recent collisionless simulations of merging massive ETGs suggest a two-phase core formation model, in which the low-density stellar core forms rapidly by supermassive black holes (SMBHs) sinking into the center due to dynamical friction. Only afterwards the SMBHs form a hard binary and the black hole scouring process slowly changes the central orbit distribution from isotropic to tangential. The observed cored density profile, the double nucleus and the isotropic center of NGC 5419 together thus point to an intermediate evolutionary state where the first phase of the core formation has taken place, yet the scouring process is only beginning. This implies that the double nucleus is a SMBH binary. Our triaxial dynamical models indicate a total mass of the two SMBHs in the center of NGC 5419 of MBH = (1.0 +/- 0.08) 10^10 Msol. Moreover, we find that NGC 5419's complex kinematically distinct core (KDC) can be explained by a coherent flip of the orbital rotation direction of stars on tube orbits at ~3kpc distance from the galaxy center together with projection effects. This is also in agreement with merger simulations hosting SMBHs in the same mass regime.

astro-ph.GA↗

arXiv2023

Minor Mergers are not enough: The importance of Major Mergers during Brightest Cluster Galaxy assembly

We investigate the roles of major and minor mergers during brightest cluster galaxy (BCG) assembly using surface brightness profiles, line indices, and fundamental plane relations. Based on our own sample and consistently reanalyzed Sloan Digital Sky Survey data, we find that BCGs and luminous normal ellipticals (LNEs) have similar central velocity dispersions, central absorption line strengths, and central surface brightnesses. However, BCGs are more luminous due to their much larger radial extent. These properties result in a flattening of the Faber$-$Jackson and Mg$_{\rm b}-$luminosity relations above 10$^{10.6}$ L$_{\odot,g'}$. We use this effect to estimate an amount of $60-80%$ of accreted and merged light in BCGs relative to LNEs, which agrees with results from cosmological simulations. We determine the contribution of this excess light (EL) at each radius from the difference between the surface flux profiles of BCGs and LNEs. It is small in the center but increases steeply to 50% at $\sim$3 kpc radius. The shape of these profiles suggests that BCGs could be formed from LNEs in three major merger processes. This is also consistent with the mild increase of the S\'ersic indices from $n\approx4$ to $n\approx6$, as confirmed in merger simulations. We note that minor mergers cannot be the dominant origin of the BCG's EL because they deposit too few stars at intermediate radii $r\lesssim20$ kpc. The shape of the EL profile also explains a detected offset of 0.14 dex of the fundamental planes for BCGs and LNEs relative to each other.

astro-ph.GA↗

arXiv2023

Introducing the Texas Euclid Survey for Lyman Alpha (TESLA) Survey: Initial Study Correlating Galaxy Properties to Lyman-Alpha Emission

We present the Texas Euclid Survey for Lyman-Alpha (TESLA), a spectroscopic survey in the 10 square degree of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lyman-alpha emitters (LAEs) correlate with Lyman-alpha emission to understand the escape of Lyman alpha from galaxies at redshifts 2 -- 3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in the grizy-bands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 square degree (H20) survey and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby-Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust, to the Lyman-alpha rest-frame equivalent widths (EW). We uncover marginal (1 sigma significance) correlations between stellar mass and Lyman-alpha EW, and star formation rate (SFR) and Lyman-alpha EW, with a Spearman correlation coefficient of -0.$34_{-.14}^{+.17}$ and -0.$37_{-.14}^{+.16}$ respectively. We show that the Lyman-alpha distribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale of 150 Angstrom. Once complete the TESLA survey will enable the study of ~ thousands of LAEs to explore correlations between galaxy properties and Lyman-alpha EW. The large sample size will allow the construction of a predictive model for the Lyman-alpha EW as a function of SED-derived galaxy properties, which could be used to improve Lyman-alpha based constraints on reionization.

astro-ph.GA↗

arXiv2023

Detailed shapes of the line-of-sight velocity distributions in massive early-type galaxies from non-parametric spectral models

We present the first systematic study of the detailed shapes of the line-of-sight velocity distributions (LOSVDs) in nine massive early-type galaxies (ETGs) using the novel non-parametric modelling code WINGFIT. High-signal spectral observations with MUSE at the VLT allow us to measure between 40 and 400 individual LOSVDs in each galaxy at a signal-to-noise level better than 100 per spectral bin and to trace the LOSVDs all the way out to the highest stellar velocities. We extensively discuss potential LOSVD distortions due to template mismatch and strategies to avoid them. Our analysis uncovers a plethora of complex, large scale kinematic structures for the shapes of the LOSVDs. Most notably, in the centers of all ETGs in our sample, we detect faint, broad LOSVD ``wings'' extending the line-of-sight velocities, v_los, well beyond 3 sigma to v_los = +- 1000 - 1500 km/s on both sides of the peak of the LOSVDs. These wings likely originate from PSF effects and contain velocity information about the very central unresolved regions of the galaxies. In several galaxies, we detect wings of similar shape also towards the outer parts of the MUSE field-of-view. We propose that these wings originate from faint halos of loosely bound stars around the ETGs, similar to the cluster-bound stellar envelopes found around many brightest cluster galaxies.

astro-ph.GA↗