Local Medium Research Articles

Sources and Radiations of the Fermi Bubbles

Two enigmatic gamma-ray features in the galactic central region, known as Fermi Bubbles (FBs), were found from Fermi-LAT data. An energy release, (e.g., by tidal disruption events in the Galactic Center, GC), generates a cavity with a shock that expands into the local ambient medium of the galactic halo. A decade or so ago, a phenomenological model of the FBs was suggested as a result of routine star disruptions by the supermassive black hole in the GC which might provide enough energy for large-scale structures, like the FBs. In 2020, analytical and numerical models of the FBs as a process of routine tidal disruption of stars near the GC were developed; these disruption events can provide enough cumulative energy to form and maintain large-scale structures like the FBs. The disruption events are expected to be 10−4∼10−5yr−1, providing an average power of energy release from the GC into the halo of E˙∼3×1041 erg s−1, which is needed to support the FBs. Analysis of the evolution of superbubbles in exponentially stratified disks concluded that the FB envelope would be destroyed by the Rayleigh–Taylor (RT) instabilities at late stages. The shell is composed of swept-up gas of the bubble, whose thickness is much thinner in comparison to the size of the envelope. We assume that hydrodynamic turbulence is excited in the FB envelope by the RT instability. In this case, the universal energy spectrum of turbulence may be developed in the inertial range of wavenumbers of fluctuations (the Kolmogorov–Obukhov spectrum). From our model we suppose the power of the FBs is transformed partly into the energy of hydrodynamic turbulence in the envelope. If so, hydrodynamic turbulence may generate MHD fluctuations, which accelerate cosmic rays there and generate gamma-ray and radio emission from the FBs. We hope that this model may interpret the observed nonthermal emission from the bubbles.

Hamilton Echelle Spectrograph Observations of Solar Analog Field Stars: Lithium Abundance and Activity

We measured lithium (Li) abundance and instantaneous chromospheric Ca ii HK activity in Hamilton Echelle Spectrograph observations of 211 solar analog field stars, with one objective being potential identification of grand minimum candidates for ongoing multiyear observation. At the zero-age main sequence, Li abundance for a typical late-type dwarf begins at the local interstellar medium abundance and over the main sequence lifetime is steadily depleted by convection at a rate dependent on details of the star’s convection and mixing processes. Our Li abundance measurements show an overall decrease in Li abundance with age and effective temperature, consistent with earlier surveys. In our activity measurements, 41 stars show log R′HK ≤ −5.0, which can be considered very inactive. Of the very inactive stars closest to solar effective temperature, 24 show Li abundances within the range typically observed for midlife Sun-like stars. Another three show very low Li abundance, which, combined with the low activity, suggest an older main sequence star or a slightly evolved star. We suggest that the combination of relatively undepleted Li and instantaneous very low activity might make these stars promising candidates for long time-series observations to determine if they are in a grand minimum state. The Hamilton Echelle Spectrograph observations are publicly available for download and are potentially useful for a variety of survey tasks involving Sun-like stars.

Persistent Behavior in Energetic Neutral Atom Time Series from IBEX

Abstract We investigate the long-term persistence of the time series of energetic neutral atom (ENA) fluxes recorded by the Interstellar Boundary Explorer (IBEX). ENAs provide global information about the outer heliosphere and its interactions with the very local interstellar medium. To avoid the IBEX Ribbon, here, we focus our analysis solely on the polar regions N60°–N90° and S60°–S90°. Each year, IBEX takes two measurements of every pixel in the sky. We make use of the whole set of 14 yr of IBEX data and adhere to the correct time order for the construction of the flux time series. We examine in detail both the trend and the fluctuations of these time series. Using modern methods of time series analysis and persistence characterization, we show that the time series (i) trend is influenced by the solar cycle, (ii) persistence can be established independently of the presence of this trend, and (iii) statistical properties of the fluctuations differs between north and south, pointing to the existence of anisotropy and thus a north–south asymmetry.

Pulsar-wind nebulae meeting the circumstellar media of their progenitors

A significative fraction of high-mass stars sail away through the interstellar medium of the galaxies. Once they evolved and died via a core-collapse supernova, a magnetised, rotating neutron star (a pulsar) is usually left over. The immediate surroundings of the pulsar is the pulsar wind, which forms a nebula whose morphology is shaped by the supernova ejecta and channelled into the circumstellar medium of the progenitor star in the pre-supernova time. Irregular pulsar-wind nebulae display a large variety of radio appearances, screened by their interacting supernova blast wave, or harbour asymmetric up–down emission. Here, we present a series of 2.5-dimensional (2 dimensions for the scalar quantities plus a toroidal component for the vectors) black non-relativistic magneto-hydrodynamical simulations exploring the evolution of the pulsar-wind nebulae generated by a red supergiant and a Wolf-Rayet massive supernova progenitor, moving with Mach number $M=1$ and $M=2$ into the warm phase of the Galactic plane. black In such a simplified approach, the progenitor's direction of motion, the local ambient medium magnetic field, and the progenitor and pulsar axis of rotation, are all aligned; this restricted our study to peculiar pulsar-wind nebula of high-equatorial-energy flux. We find that the reverberation of the termination shock of the pulsar-wind nebulae, when sufficiently embedded into its dead stellar surroundings and interacting with the supernova ejecta, is asymmetric and differs greatly as a function of the past circumstellar evolution of its progenitor, which reflects into their projected radio synchrotron emission. This mechanism is particularly at work in the context of remnants involving slowly moving or very massive stars. We find that the mixing of material in plerionic core-collapse supernova remnants is strongly affected by the asymmetric reverberation in their pulsar-wind nebulae.

Ultraviolet extinction correlation with 3D dust maps using white dwarfs

ABSTRACT Accurate astrometric and photometric measurements from Gaia have led to the construction of 3D dust extinction maps which can now be used for estimating the integrated extinctions of Galactic sources located within 5 kpc. These maps based on optical observations may not be reliable for use in the ultraviolet (UV) which is more sensitive to reddening. Past studies have focussed on studying UV extinction using main-sequence stars but lack comparison with 3D dust maps. White dwarfs with well-modelled hydrogen-dominated (DA) atmospheres provide an advantage over main-sequence stars affected by magnetic activity. In this work, we study the variation of UV extinction with 3D dust maps utilizing Hubble Space Telescope (HST) and Galaxy Evolution Explorer (GALEX) observations of DA white dwarfs located within 300 pc. We used HST COS spectroscopic data of 76 sightlines to calculate the optical extinction from Si ii column densities and validate our results with the kinematic model predictions of the local interstellar medium. Also, we combined GALEX and Gaia photometric observations of 1158 DA white dwarfs to study UV reddening by comparing observed and modelled colour–colour relations. We calculated GALEX non-linearity corrections and derived reddening coefficients [$R(NUV-G)=6.52\pm 1.53$ and $R(FUV-G)=6.04\pm 2.41$] considering their variations with optical extinction ($\rm{A_{V}}\lt 0.1$ mag), and found them to be in good agreement with known extinction laws. HST analysis suggests a positive bias of 0.01–0.02 mag in the optical extinction from 3D maps depending on the Galactic latitude. These results independently confirm the validity of 3D dust maps to de-redden the optical and UV observations of white dwarfs.

The XRISM first-light observation: Velocity structure and thermal properties of the supernova remnant N 132D

Abstract We present an initial analysis of the X-Ray Imaging and Spectroscopy Mission (XRISM) first-light observation of the supernova remnant (SNR) N 132D in the Large Magellanic Cloud. The Resolve microcalorimeter has obtained the first high-resolution spectrum in the 1.6–10 keV band, which contains K-shell emission lines of Si, S, Ar, Ca, and Fe. We find that the Si and S lines are relatively narrow, with a broadening represented by a Gaussian-like velocity dispersion of $\sigma _v \sim 450$ km s$^{-1}$. However, the Fe He$\alpha$ lines are substantially broadened with $\sigma _v \sim 1670$ km s$^{-1}$. This broadening can be explained by a combination of the thermal Doppler effect due to the high ion temperature and the kinematic Doppler effect due to the SNR expansion. Assuming that the Fe He$\alpha$ emission originates predominantly from the supernova ejecta, we estimate the reverse shock velocity at the time when the bulk of the Fe ejecta were shock heated to be $-1000 \lesssim V_{\rm rs}$ (km s$^{-1}$) $\lesssim 3300$ (in the observer frame). We also find that Fe Ly$\alpha$ emission is redshifted with a bulk velocity of $\sim 890$ km s$^{-1}$, substantially larger than the radial velocity of the local interstellar medium surrounding N 132D. These results demonstrate that high-resolution X-ray spectroscopy is capable of providing constraints on the evolutionary stage, geometry, and velocity distribution of SNRs.

The Impact of Headline Characteristics on Clicks: A Case Study of a Chinese Local Medium

ABSTRACT This paper addressed the question of whether the headline characteristics of a WeChat post affect its click counts. The research collected more than 40,000 posts from the WeChat official accounts of two local Chinese media outlets, scrutinizing headline features such as headline length, clickbait-type punctuation marks, and Arabic numeric symbols, and controlling for sharing amounts, content themes, and emotion words in titles. It found that the headline length and whether it contained clickbait-type punctuation marks had a significant impact on the number of clicks. Among them, the shorter the headline, the more likely it was to get a higher number of clicks, and the higher chance for the post to become a “100,000 + clicks” content. Moreover, an interesting finding was that headlines containing positive emotional words seemed to have a negative impact on click-through rates.

Local H i absorption towards the magellanic cloud foreground using ASKAP

ABSTRACT We present the largest Galactic neutral hydrogen H i absorption survey to date, utilizing the Australian SKA Pathfinder Telescope at an unprecedented spatial resolution of 30 arcsec. This survey, GASKAP-H i, unbiasedly targets 2714 continuum background sources over 250 square degrees in the direction of the Magellanic Clouds, a significant increase compared to a total of 373 sources observed by previous Galactic absorption surveys across the entire Milky Way. We aim to investigate the physical properties of cold (CNM) and warm (WNM) neutral atomic gas in the Milky Way foreground, characterized by two prominent filaments at high Galactic latitudes (between $-45^{\circ }$ and $-25^{\circ }$). We detected strong H i absorption along 462 lines of sight above the 3$\sigma$ threshold, achieving an absorption detection rate of 17 per cent. GASKAP-H i’s unprecedented angular resolution allows for simultaneous absorption and emission measurements to sample almost the same gas clouds along a line of sight. A joint Gaussian decomposition is then applied to absorption-emission spectra to provide direct estimates of H i optical depths, temperatures, and column densities for the CNM and WNM components. The thermal properties of CNM components are consistent with those previously observed along a wide range of Solar neighbourhood environments, indicating that cold H i properties are widely prevalent throughout the local interstellar medium. Across our region of interest, CNM accounts for $\sim$30 per cent of the total H i gas, with the CNM fraction increasing with column density towards the two filaments. Our analysis reveals an anticorrelation between CNM temperature and its optical depth, which implies that CNM with lower optical depth leads to a higher temperature.

Constraining the Properties of the Multicomponent Local Interstellar Medium: MHD-kinetic Modeling Validated by Voyager and New Horizons Data

We introduce the first solar-cycle simulations from our 3D, global MHD-plasma/kinetic-neutrals model, where both hydrogen and helium atoms are treated kinetically, while electrons and helium ions are described as individual fluids. Using Voyager/PWS observations of electron density up to 160 au from the Sun for validation of several different global models, we conclude that the current estimates for the proton density in the local interstellar medium (LISM) need a revision. Our findings indicate that the commonly accepted value of 0.054 cm−3 may need to be increased to values exceeding 0.07 cm−3. We also show how different assumptions regarding the proton velocity distribution function in the outer heliosheath may affect the global solution. A new feature revealed by our simulations is that the helium ion flow may be significantly compressed and heated in the heliotail at heliocentric distances exceeding ∼400 au. Additionally, we identify a Kelvin–Helmholtz instability at the boundary of the slow and fast solar wind in the inner heliosheath, which acts as a driver of turbulence in the heliotail. These results are crucial for inferring the properties of the LISM and of the global heliosphere structure.

Determining the Interstellar Wind Longitudinal Inflow Evolution Using Pickup Ions in the Helium Focusing Cone

The size, shape, and composition of the heliosphere are affected by its interaction with the local interstellar medium. A means of quantifying this interaction is by measuring the relative motion of the two media. We determine the flow direction, λISN , of the interstellar wind through the heliosphere and its trend over an 11 yr solar cycle using Advanced Composition Explorer/Solar Wind Ion Composition Spectrometer He+ double-coincidence pickup ion (PUI) measurements from a data set spanning 13 full orbits, with focusing cone crossings occurring between the years 1998 and 2010. We measure the flow direction by fitting a kappa function to the focusing cone signature in the count rates of He+ at the PUI cutoff measured as a function of ecliptic longitude. We determine λISN for each three-orbit boxcar centered on the years 1999 through 2009 and find the trend of the resulting linear fit. We account for solar transients by removing measurements associated with CMEs. However, there still may be effects from compression regions, such as stream–stream and corotating interaction regions. We additionally make considerations to ensure the PUI torus is in view, to account for varying interplanetary magnetic field angles, to ensure that we analyze newly injected interstellar PUIs largely unaffected by transport effects, and to account for general solar activity. We measure a slope in the flow direction to be 0.00° ± 0.51°​​​​ yr−1, indicating that we do not measure a varying trend over this period. We repeat the focusing cone analysis for the combined data set and determine an overall flow direction of 75.37° ± 0.43°.

Spatially–resolved gas-phase metallicity in Seyfert galaxies

Abstract We explore the relations between the gas-phase metallicity radial profiles (few hundred inner parsec) and multiple galaxy properties for 15 Seyfert galaxies from the AGNIFS (Active Galactic Nuclei Integral Field Spectroscopy) sample using optical Integral Field Unit (IFU) observations from Gemini Multi-Object Spectrographs (GMOS) and Multi Unit Spectroscopic Explorer (MUSE) processed archival data. The data were selected at z ≲ 0.013 within black hole mass range [6 < log (MBH/M⊙) < 9] with moderate 14–150 keV X-ray luminosities $\left[42\, \lesssim \, \log L_X (\rm erg\, s^{-1})\, \lesssim \, 44\right]$. We estimated the gas-phase metallicity using the strong-line methods and found mean values for the oxygen dependent (Z ∼ 0.75 Z⊙) and nitrogen dependent (Z ∼ 1.14 Z⊙) calibrations. These estimates show excellent agreement with ΔZ ≈ 0.19 dex and ΔZ ≈ 0.18 dex between the mean values from the two strong-line calibrations for GMOS and MUSE respectively, consistent with the order of metallicity uncertainty via the strong-line methods. We contend that our findings align with a scenario wherein local Seyferts have undergone seamless gas accretion histories, resulting in positive metallicity profile over an extended period of time, thereby providing insights into galaxy evolution and the chemical enrichment or depletion of the universe. Additionally, we argue that metal-poor gas inflow from the local interstellar medium (ISM) and accreted through the circumgalactic medium (CGM) onto the galaxy systems regulates the star formation processes by diluting their central metallicity and inverting their metallicity gradients, producing a more prominent anti-correlation between gas-phase metallicity and Eddington ratio.

Evolving Outer Heliosphere: Tracking Solar Wind Transients from 1 au to the VLISM with IBEX and Voyager 1

Interstellar Boundary Explorer (IBEX) observations of energetic neutral atom (ENA) fluxes from the heliosphere have greatly enriched our understanding of the interaction of the solar wind (SW) with the local interstellar medium (LISM). However, there has been recent controversy surrounding the inability of most ENA models to produce as high an intensity of ∼0.5–6 keV ENAs as IBEX observes at 1 au, especially as a function of time. In our previous study (E. J. Zirnstein et al.), we introduced a new model that utilizes a data-driven magnetohydrodynamic simulation of the SW–LISM interaction to propagate pickup ions through the heliosheath (HS) after they are nonadiabatically heated at the heliospheric termination shock. E. J. Zirnstein et al. only simulated and analyzed IBEX observations from the direction of Voyager 2. In this study, we expand our model to include fluxes from the direction of Voyager 1, as well as in the low-latitude part (middle) of the ribbon (10° below the ecliptic plane). We show that the model results at Voyager 1 are consistent with E. J. Zirnstein et al.’s results at Voyager 2 in terms of a secondary ENA source contribution of ≲20% from both directions. Our results in the middle of the ribbon also reproduce the data, when including a time-dependent secondary ENA source. Finally, we demonstrate with our simulation that three large pressure waves likely merged in the VLISM and were observed by Voyager 1 as “pf2,” while at least one of the wave’s effects in the HS was observed by IBEX as a brief enhancement in ENA flux in early 2016.

Rhythms of Kinabalu 2022 “Coming Back Stronger”: A Review

This article reviews the Rhythms of Kinabalu 2022 from the dual perspective of management and performance. Ever since its commencement in 2011, Rhythms of Kinabalu has been a yearly large-scale event organised by the National Department for Culture and Arts under the Ministry of Tourism, Arts and Culture Malaysia along with other collaborative bodies. The aim of this festival is to showcase the diversity and uniqueness of the dances, arts, and music in Sabah for the purpose of their continued popularity, relevance, and sustainability. As such, the review examines the current nature of festival, paying attention to the various categories of performances and performers in Rhythms of Kinabalu 2022 as well as the favoured and less favoured performances and/or artists as indicated by viewer turnouts of the live shows. At the same time, the article seeks to understand the local audiences’ reception and/or reaction towards the event and its many shows to signal the current festivalgoers’ taste and preference of the performing arts. A main observation reveals the striking presence of the art of busking and an imbalance in the representation of modern and traditional art forms. Essentially, the representation of traditional arts was limited and those artists struggled to keep up with their more modern counterpart. Technology, namely, social media, has been identified to have played a major role in influencing this outcome and contributing to this scenario. Management wise, the lack of cooperation from business entities (i.e., premise operators and owners) in support of the local artists, performers, small and medium enterprises, and the event itself is a cause for concern as this has caused several setbacks which were detrimental to the festival’s operations. Hence, the art-based and managerial issues identified in this review may benefit the relevant stakeholders in its decision-making of the festival’s future cycles.

Efficient implementation of equivalent medium parameterization in finite-difference seismic wave simulation methods

Summary Grid point discretization of the model has a significant impact on the accuracy of finite-difference seismic waveform simulations. Discretizing the discontinuous velocity model using local point medium parameters can lead to artifact diffraction caused by the stair-step representation and inaccuracies in calculated waveforms due to interface errors, particularly evident when employing coarse grids. To accurately represent model interfaces and reduce interface errors in finite-difference calculations, various equivalent medium parametrization methods have been developed in recent years. Most of these methods require volume-integrated averaging calculations of the medium parameter values within grid cells. The simplest way to achieve this volume averaging is to apply numerical integration averaging to all grid cells. However, this approach demands considerable computational time. To address this computational challenge, we propose employing a set of auxiliary grids to identify which grid cells intersected by the welded interface and perform volume averaging only on these specific cells, thereby reducing unnecessary computational overhead. Additionally, we present a three-dimensional tilted transversely isotropic equivalent medium parameterization method, which effectively suppresses interface errors and artefact diffraction under the application of coarse grids. We also provide an approach for computing the normal direction of the interface, which is essential for the tilted transversely isotropic equivalent medium parameterization. Numerical tests validate the accuracy of the tilted transversely isotropic equivalent medium parameterization method and demonstrate the practicality of the implementation proposed in this paper for complex models.

Probing the strength of radial migration via churning by using metal-rich red giant stars from APOGEE

ABSTRACT Making use of the APOGEE DR17 catalogue with high quality data for 143 509 red giant branch stars we explore the strength of different mechanisms that causes a star to radially migrate in the Milky Way stellar disc. At any position in the disc we find stars that are more metal-rich than the local interstellar medium. This is surprising and normally attributed to the migration of these stars after their formation inside their current Galactocentric radius. Such stars are prime candidates for studying the strength of different migratory processes. We specifically select two types of metal-rich stars: (i) super metal-rich stars ($\mathrm{[Fe/H]}\gt 0.2$) and (ii) stars that are more metal-rich than their local environment. For both, we explore the distribution of orbital parameters and ages as evidence of their migration history. We find that most super metal-rich stars have experienced some amount of churning as they have orbits with $R_g\gtrsim 5 \,{\rm kpc}$. Furthermore, about half of the super metal-rich stars are on non-circular orbits ($\mathrm{ecc} \gt 0.15$) and therefore also have experienced blurring. The metallicity of young stars in our sample is generally the same as the metallicity of the interstellar medium, suggesting they have not radially migrated yet. Stars with lower metallicity than the local environment have intermediate to old ages. We further find that super metal-rich stars have approximately the same age distribution at all Galactocentric radii, which suggests that radial migration is a key mechanism responsible for the chemical compositions of stellar populations in the Milky Way.

The Solar Magnetic Hump, Heliopause, and the Very Local Interstellar Medium

The magnetic hump was observed from 2020.4 to ∼2022 by Burlaga et al. who offered the hypothesis that it originated at the Sun during the declining phase of the solar cycle. Voyager 1 observed intermittency of 1 hr increments of the magnetic field from 2013 through 2019, as well as in the magnetic hump that began at the jump pf2 at 2020.4 and ended at ∼2022. Throughout this interval, the intermittency in the components of B and the magnitude B was described by the Tsallis distribution (q-Gaussian distribution). The q-Gaussian distributions have been observed throughout the solar wind and heliosheath. However, there was little or no intermittency in the 1 hr increments of the magnetic field observed by Voyager 1 from ∼2022.0 through day 270, 2023. During this interval Voyager 1 observed intermittency with a Gaussian distribution, which is associated with Boltzmann–Gibbs statistics. The boundary between these two regions, at ∼2022.0, coincides with the heliopause predicted by Fisk & Gloeckler. Alternatively, the Voyager 1 observations might be a solar cycle effect.

Feedback in Emerging Extragalactic Star Clusters, FEAST: The Relation between 3.3 μm Polycyclic Aromatic Hydrocarbon Emission and Star Formation Rate Traced by Ionized Gas in NGC 628

We present maps of ionized gas (traced by Paα and Brα) and 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission in the nearby spiral galaxy NGC 628, derived from new JWST/NIRCam data from the Feedback in Emerging extrAgalactic Star clusTers (FEAST) survey. With this data, we investigate and calibrate the relation between 3.3 μm PAH emission and star formation rate (SFR) in and around emerging young star clusters (eYSCs) on a scale of ∼40 pc. We find a tight (correlation coefficient ρ ∼ 0.9) sublinear (power-law exponent α ∼ 0.75) relation between the 3.3 μm PAH luminosity surface density and SFR traced by Brα for compact, cospatial (within 0.″16 or ∼7 pc) peaks in Paα, Brα, and 3.3 μm (eYSC–I). The scatter in the relationship does not correlate well with variations in local interstellar medium metallicity, due to a radial metallicity gradient, but rather is likely due to stochastic sampling of the stellar initial mass function (IMF) and variations in the PAH heating and age of our sources. The deviation from a linear relation may be explained by PAH destruction in more intense ionizing environments, variations in age, and IMF stochasticity at intermediate to low luminosities. We test our results with various continuum subtraction techniques using combinations of NIRCam bands and find that they remain robust with only minor differences in the derived slope and intercept. An unexpected discrepancy is identified between the relations of hydrogen recombination lines (Paα versus Brα; Hα versus Brα).

The ESO SupJup Survey

Context. It has been proposed that the distinct formation and evolutionary pathways of exoplanets and brown dwarfs may affect the chemical and isotopic content of their atmospheres. Recent work has indeed shown differences in the 12C/13C isotope ratio, which have provisionally been attributed to the top-down formation of brown dwarfs and the core accretion pathway of super-Jupiters. Aims. The ESO SupJup Survey is aimed at disentangling the formation pathways of isolated brown dwarfs and planetary-mass companions using chemical and isotopic tracers. The survey utilises high-resolution spectroscopy with the recently upgraded CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES+) at the Very Large Telescope, covering a total of 49 targets. Here, we present the first results of this survey: an atmospheric characterisation of DENIS J0255-4700, an isolated brown dwarf near the L-T transition. Methods. We analysed its observed CRIRES+ K-band spectrum using an atmospheric retrieval framework in which the radiative transfer code petitRADTRANS was coupled with the PyMultiNest sampling algorithm. Gaussian processes were employed to model inter-pixel correlations. In addition, we adopted an updated parameterisation of the pressure-temperature profile. Results. Abundances of CO, H2O, CH4, and NH3 were retrieved for this fast-rotating L-dwarf. The ExoMol H2O line list provides a significantly better fit than that of HITEMP. A free-chemistry retrieval is strongly favoured over equilibrium chemistry, caused by an under-abundance of CH4. The free-chemistry retrieval constrains a super-solar C/O-ratio of ~0.68 and a solar metallicity. We find tentative evidence (~3σ) for the presence of 13CO, with a constraint on the isotopologue ratio of 12CO/13CO = 184−40+61 and a lower limit of ≳97, which suggests a depletion of 13C compared to the local interstellar medium (12C/13C ~ 68). Conclusions. High-resolution, high signal-to-noise K-band spectra provide an excellent means of constraining the chemistry and isotopic content of sub-stellar objects, which is the main objective of the ESO SupJup Survey.

The ESO SupJup Survey II. The 12C/13C isotope ratios of three young brown dwarfs with CRIRES+

Young brown dwarfs exhibit atmospheric characteristics similar to those of super-Jupiters, providing a unique opportunity to study planetary atmospheres. Atmospheric retrievals of high-resolution spectra reveal detailed properties of these objects, with elemental and isotopic ratios offering insights into their formation history. The ESO SupJup Survey, utilising CRIRES$^+$ on the Very Large Telescope, aims to assess the role of as a formation tracer. We present observations of three young brown dwarfs: 2MASS J12003792-7845082, TWA 28, and 2MASS J08561384-1342242. Our goal is to constrain their chemical compositions, thermal profiles, surface gravities, spin rotations, and Cratio. We conducted atmospheric retrievals of CRIRES$^+$ K-band spectra, coupling the radiative transfer code petitRADTRANS with the Bayesian inference algorithm MultiNest The retrievals provide a detailed characterisation of the atmospheres of the three objects. We report the volume mixing ratios of the main molecular and atomic species: HF, Na, Ca, and Ti, including the novel detection of hydrogen fluoride (HF) in the atmosphere of a brown dwarf. We determine values of $ and $79^ $ in the atmospheres of TWA 28 and J0856, respectively, with strong significance ($>3 We also report tentative evidence ($ of in J1200, at $. Additionally, we detect at moderate significance in J0856 (3.3sigma ) and TWA 28 (2.1sigma ). The retrieved thermal profiles are consistent with hot atmospheres ($2300-2600$ K) with low surface gravities and slow spins, as expected for young objects. The measured carbon isotope ratios are consistent among the three objects and show no significant deviation from that of the local interstellar medium, suggesting a fragmentation-based formation mechanism similar to star formation. The tentative detection of in two objects of our sample highlights the potential of high-resolution spectroscopy to probe additional isotope ratios, such as O in the atmospheres of brown dwarfs and super-Jupiters.

The Plane Quasar Survey: First Data Release

We present a sample of 305 QSO candidates having ∣b∣ < 30°, the majority with GALEX magnitudes near-UV < 18.75. To generate this sample, we apply UV–IR color selection criteria to photometric data from the Ultraviolet Galactic Plane Survey as part of GALEX-CAUSE, the Million Quasars Catalog, Gaia DR2, and Pan-STARRS DR1. 165 of these 305 candidate UV-bright active galactic nuclei (AGN; 54%) have published spectroscopic redshifts from 45 different surveys, confirming them as AGN. We further obtained low-dispersion, optical, long-slit spectra with the Apache Point Observatory 3.5 m, MDM 2.4 m, and MDM 1.3 m telescopes for 84 of the candidates, and confirm 86% (N = 72) as AGN, generally with z < 0.6. Of these 72 confirmed AGN, 25 are newly discovered low-latitude QSOs without any previous spectroscopy. These sources fill a gap in the Galactic latitude coverage of the available samples of known UV-bright QSO background probes. Along with a description of the confirmed QSO properties, we provide the fully reduced, flux- and wavelength-calibrated spectra of 72 low-latitude QSOs through the Mikulski Archive for Space Telescopes. Future Hubble Space Telescope/Cosmic Origins Spectrograph spectroscopy of these low-Galactic-latitude QSOs has the potential to transform our view of the Milky Way and Local Group circumgalactic medium.