Integral Field Spectroscopy Research Articles

JADES

Finding the first generation of stars formed out of pristine gas in the early Universe, known as Population III (PopIII) stars, is one of the most important goals of modern astrophysics. Recent models have suggested that PopIII stars may form in pockets of pristine gas in the halo of more evolved galaxies. We present NIRSpec integral field spectroscopy and micro-shutter array spectroscopic observations of the region around GN-z11, an exceptionally luminous galaxy at z = 10.6, that reveal a greater than 5σ detection of a feature consistent with being HeIIλ1640 emission at the redshift of GN-z11. The very high equivalent width of the putative HeII emission in this clump (log(EWrest(HeII)/Å) = 1.79−0.25+0.15) and a lack of metal lines can be explained in terms of photoionisation by PopIII stars, while photoionisation by PopII stars is inconsistent with the data. The high equivalent width would also indicate that the putative PopIII stars likely have an initial mass function with an upper cutoff reaching at least 500 M⊙. The PopIII bolometric luminosity inferred from the HeII line would be ∼7 × 109 L⊙, which would imply a total stellar mass formed in the burst of ∼2 × 105 M⊙. We find that photoionisation by the active galactic nucleus (AGN) in GN-z11 cannot account for the HeII luminosity observed in the clump but can potentially be responsible for an additional HeII emission observed closer to GN-z11. We also consider the possibility of in situ photoionisation by an accreting direct collapse black hole hosted by the HeII clump. We find that this scenario is less favoured, but it remains a possible alternative interpretation. We also report the detection of a Lyα halo stemming out of GN-z11 and extending out to ∼2 kpc as well as resolved funnel-shaped CIII emission likely tracing the ionisation cone of the AGN.

H i Lyα Emission from a Metal-poor Cool Stream Fueling an Early Dusty Starburst

The GAMA J0913−0107 system is a rare conjunction of a submillimeter galaxy (SMG) at z ≈ 2.7 and two background QSOs with projected separations <200 kpc. Previous high-resolution QSO absorption-line spectroscopy has revealed high H i column density, extremely metal-poor (∼1% solar) gas streams in the circumgalactic medium of the SMG. Here we present deep optical integral-field spectroscopy of the system with the Keck Cosmic Web Imager (KCWI). Reaching a 2σ surface brightness limit ≈10−19 erg s−1 cm−2 arcsec−2 with ∼2 hr of integration time, we detect a filamentary Lyα nebula stretching ∼180 kpc from the SMG intercepting both QSO sightlines. This Lyα filament may correspond to the same cool gas stream penetrating through the hot halo seen in the absorption. In contrast to Lyα nebulae around QSOs, there is no obvious local source for photoionization due to the massive dust content. While uncertain, we consider the possibility that the nebula is ionized by shocks induced by the infall, obscured star formation, and/or a boosted UV background. The SMG–QSOs conjunction multiplied the efficiency of the KCWI observations, allowing a direct comparison of Lyα nebulae in two distinct environments. We find that the nebulae around the QSOs are much brighter and show steeper surface brightness profiles than the SMG nebula. This is consistent with the additional photoionization and Lyα scattering provided by the QSOs. While illustrating the challenges of detecting Lyα nebulae around SMGs, our work also demonstrates that important insights can be gained from comparative studies of high-z Lyα nebulae.

Resolved properties of a luminous hinge clump in the compact group of galaxies NGC 6845

Context. Compact groups of galaxies are unique places where galaxy-galaxy interactions play a mayor role on the evolution of its members. These strong gravitational encounters can induce star formation bursts. Aims. We study the properties of one of the most luminous so-called hinge clumps that is located in the compact group of galaxies NGC 6845. Methods. Using integral field spectroscopy from GMOS/Gemini complemented with archival MUSE data, we obtained oxygen abundances, ages, star formation rates, and velocity fields, and we also modeled a single stellar population to understand the star formation history of the hinge clump in NGC 6845. Results. We found that the hinge clump sits in a tailthat has a star formation rate of 3.4 M⊙ yr−1, which is comparable with a few other extreme cases, for instance, the star clusters in the Antennae galaxy and other reported hinge clumps in the literature. This clump represents ∼15% of total star formation rate of NGC 6845A. Large-scale modeling of the observed velocity field of NGC 6845A rules out the scenario according to which this hinge clump was a satellite galaxy. Its kinematics is compatible with that of the galactic disk of NGC 6845A. Its abundance with a mean value of 0.4 Z⊙ is also consistent with the metallicity gradient of the galaxy. Conclusions. Our analysis suggest that the hinge clump is formed by multiple stellar populations and not by a single burst. This causes the wide age range. We found that the central clump is encompassed by a ring-like structure, which might suggest a second generation of star formation. In addition, the analysis of the diagnostic diagram indicates that this central region might also be ionized by shocks from stellar and supernova winds. Finally, the derived star formation rate density Σ = 9.7 M⊙ yr−1 kpc−2 of the central clump places it in starburst regime, where gas inflows should provide gas to maintain the star formation. This work shows a resolved example of an extreme localized starburst in a compact group of galaxies.

Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS)

We present the Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS) project, designed for the spatial and spectral study of the diffuse ionised gas (DIG) in a selection of nearby spiral galaxies observed with the MUSE integral-field spectrograph. Our primary objective is to investigate the various ionisation mechanisms at play within the DIG. We analysed the distribution of high- and low-ionisation species in the optical spectra of the sample on a spatially resolved basis. We introduced a new methodology for spectroscopically defining the DIG, optimised for galaxies of different resolutions. Firstly, we employed an innovative adaptive binning technique on the observed datacube based on the spectroscopic signal-to-noise ratio (S/N) of the collisional [S II] line to increase the S/N of the rest of the lines including [O III], [O I], and He I. Subsequently, we created a DIG mask by eliminating the emissions associated with both bright and faint H II regions. We also examined the suitability of using Hα equivalent width (EWHα) as a proxy for defining the DIG and its associated ionisation regime. Notably, for EWHα &lt; 3 Å – the expected emission from hot low-mass evolved stars (HOLMES) – the measured value is contingent on the chosen population synthesis technique performed. Our analysis of the showcase sample reveals a consistent cumulative DIG fraction across all galaxies in the sample, averaging around 40%–70%. The average radial distribution of the [N II]/Hα, [S II]/Hα, [O I]/Hα, and [O III]/Hβ ratios are enhanced in the DIG regimes (up to 0.2 dex). It follows similar trends between the DIG regime and the H II regions, as well as the Hα surface brightness (ΣHα), indicating a correlation between the ionisation of these species in both the DIG and the H II regions. The DIG loci in typical diagnostic diagrams are found, in general, within the line ratios that correspond to photoionisation due to the star formation. There is a noticeable offset correspondent to ionisation due to fast shocks. However, an individual diagnosis performed for each galaxy reveals that all the DIG in these galaxies can be attributed to photoionisation from star formation. The offset is primarily due to the contribution of Seyfert galaxies in our sample, which is closely aligned with models of ionisation from fast shocks and galactic outflows, thus mimicking the DIG emission. Our results indicate that galaxies exhibiting active galactic nucleus (AGN) activity should be considered separately when conducting a general analysis of the DIG ionisation mechanisms, since this emission is indistinguishable from high-excitation DIG.

Shockingly Bright Warm Carbon Monoxide Molecular Features in the Supernova Remnant Cassiopeia A Revealed by JWST

We present JWST NIRCam (F356W and F444W filters) and MIRI (F770W) images and NIRSpec Integral Field Unit (IFU) spectroscopy of the young Galactic supernova remnant Cassiopeia A (Cas A) to probe the physical conditions for molecular CO formation and destruction in supernova ejecta. We obtained the data as part of a JWST survey of Cas A. The NIRCam and MIRI images map the spatial distributions of synchrotron radiation, Ar-rich ejecta, and CO on both large and small scales, revealing remarkably complex structures. The CO emission is stronger at the outer layers than the Ar ejecta, which indicates the re-formation of CO molecules behind the reverse shock. NIRSpec-IFU spectra (3–5.5 μm) were obtained toward two representative knots in the NE and S fields that show very different nucleosynthesis characteristics. Both regions are dominated by the bright fundamental rovibrational band of CO in the two R and P branches, with strong [Ar vi] and relatively weaker, variable strength ejecta lines of [Si ix], [Ca iv], [Ca v], and [Mg iv]. The NIRSpec-IFU data resolve individual ejecta knots and filaments spatially and in velocity space. The fundamental CO band in the JWST spectra reveals unique shapes of CO, showing a few tens of sinusoidal patterns of rovibrational lines with pseudocontinuum underneath, which is attributed to the high-velocity widths of CO lines. Our results with LTE modeling of CO emission indicate a temperature of ∼1080 K and provide unique insight into the correlations between dust, molecules, and highly ionized ejecta in supernovae and have strong ramifications for modeling dust formation that is led by CO cooling in the early Universe.

Optical Design of a Hyperspectral Remote-Sensing System Based on an Image-Slicer Integral Field Unit in the Short-Wave Infrared Band.

Grating-type spectral imaging systems are frequently employed in scenes for high-resolution remote-sensing observations of the Earth. However, the entrance of the grating-type spectral imaging system is a slit or a pinhole. This structure relies on the push broom method, which presents a challenge in capturing spectral information of transiently changing targets. To address this issue, the IFU is used to slice the focal plane of the telescope system, thereby expanding the instantaneous field of view (IFOV) of the grating-type spectral imaging system. The aberrations introduced by the expansion of the single-slice field of view (FOV) of the IFU are corrected, and the conversion of the IFU's FOV from arcseconds to degrees is achieved. The design of a spectral imaging system based on an image-slicer IFU for remote sensing is finally completed. The system has a wavelength range of 1400 nm to 2000 nm, and a spectral resolution of better than 3 nm. Compared with the traditional grating-type spectral imaging system, its IFOV is expanded by a factor of four. And it allows for the capture of complete spectral information of transiently changing targets through a single exposure. The simulation results demonstrate that the system has good performance at each sub-slit, thereby validating the effectiveness and advantages of the proposed system for dynamic target capture in remote sensing.

Microcalorimeter Absorber Optimization for ATHENA and LEM

High quantum efficiency (QE) X-ray absorbers are needed for future X-ray astrophysics telescopes. The Advanced Telescope for High ENergy Astrophysics (ATHENA) mission requirements for the X-ray Integral Field Unit (X-IFU) instrument dictate, at their most stringent, that the absorber achieve vertical QE > 90.6% at 7 keV and low total heat capacity, 0.731 pJ/K. The absorber we have designed is 313 µm square composed of 1.05 μm Au and 5.51 μm electroplated Bi films (Barret et al. in Exp Astron 55:373–426, 2023). Overhanging the TES, the absorber is mechanically supported by 6 small legs whose 5 μm diameter is tuned to the target thermal conductance for the device. Further requirements for the absorber for X-IFU include a > 40% reflectance at wavelengths from 1 to 20 μm to reduce shot noise from infrared radiation from higher temperature stages in the cryostat. We meet this requirement by capping our absorbers with an evaporated Ti/Au thin film. Additionally, narrow gaps between absorbers are required for high fill fraction, as well as low levels of fine particulate remaining on the substrate and zero shorts between absorbers that may cause thermal crosstalk. The Light Element Mapper (LEM) is an X-ray probe concept optimized to explore the soft X-ray emission from 0.2 to 2.0 keV. These pixels for LEM require high residual resistance ratio (RRR) thin 0.5 µm Au absorbers to thermalize uniformly and narrow < 2 μm gaps between pixels for high areal fill fraction. This paper reports upon technology developments required to successfully yield arrays of pixels for both mission concepts and presents first testing results of devices with these new absorber recipes.

One-sided H α excess before the first pericentre passage in galaxy pairs

ABSTRACT We present novel insights into the interplay between tidal forces and star formation in interacting galaxies before their first pericentre passage. We investigate seven close pair galaxies devoid of visible tidal disturbances, such as tails, bridges, and shells. Using integral field spectroscopy data of extended Calar Alto Legacy Integral Field Area, we unveil a previously unreported phenomenon: H $\alpha$ emission, a proxy for recent star formation, exhibits a significant enhancement in regions facing the companion galaxy, reaching up to 1.9 times higher flux compared to opposite directions. Notably, fainter companions within pairs display a more pronounced one-sided H $\alpha$ excess, exceeding the typical range observed in isolated galaxies with 2$\sigma$ confidence level. Furthermore, the observed H $\alpha$ excess in fainter companion galaxies exhibits a heightened prominence at the outer galactic regions. These findings suggest that tidal forces generated before the first pericentre passage exert a stronger influence on fainter galaxies due to their shallower potential wells by their brighter companions. This unveils a more intricate interplay between gravitational interactions and star formation history within interacting galaxies than previously understood, highlighting the need further to explore the early stages of interaction in galaxy evolution.

The MAGPI Survey: massive slow rotator population in place by z ∼ 0.3

ABSTRACT We use the ‘Middle Ages Galaxy Properties with Integral field spectroscopy’ (MAGPI) survey to investigate whether galaxies have evolved in the distribution of their stellar angular momentum in the past 3–4 Gyr, as probed by the observational proxy for spin, λR. We use 2D stellar kinematics to measure λR along with detailed photometric models to estimate galaxy ellipticity. The combination of these measurements quantifies the kinematic classes of ‘fast rotators’ and the rarer ‘slow rotators’, which show no regular rotation in their line-of-sight velocity fields. We compare 51 MAGPI galaxies with log10 (M⋆/M⊙) &amp;gt; 10 to carefully drawn samples of MaNGA galaxies in the local Universe, selected to represent possible descendants of the MAGPI progenitors. The EAGLE simulations are used to identify possible evolutionary pathways between the two samples, explicitly accounting for progenitor bias in our results and the varied evolutionary pathways a galaxy might take between the two epochs. We find that the occurrence of slow rotating galaxies is unchanged between the MAGPI (z ∼ 0.3) and MaNGA (z ∼ 0) samples, suggesting the massive slow rotator population was already in place ∼4 Gyr ago and has not accumulated since. There is a hint of the MAGPI sample having an excess of high λR galaxies compared to the MaNGA sample, corresponding to more ordered rotation, but statistically the samples are not significantly different. The large-scale stellar kinematics, as quantified through the λR parameter, of galaxies at z ∼ 0.3 have already evolved into the diversity of structures seen today in the local Universe.

The SAMI Galaxy Survey: impact of star formation and AGN feedback processes on the ionized gas velocity dispersion

ABSTRACT We investigate the influence of star formation and instantaneous active galactic nuclei (AGN) feedback processes on the ionized gas velocity dispersion in a sample of 1285 emission-line galaxies with stellar masses $\log \, (M_*/\mathrm{ M}_{\odot }) \ge 9$ from the integral-field spectroscopy Sydney-AAO Multi-object Integral-field Galaxy Survey. We fit both narrow- and broad-emission-line components using aperture spectra integrated within one effective radius, while ensuring the elimination of velocity differences between the spectra of individual spaxels. Our analysis reveals that 386 (30 per cent) galaxies can be adequately described using a single-emission component while 356 (28 per cent) galaxies require two (broad and narrow) components. Galaxies characterized by high-mass, elevated star formation rate surface density, or type-2 AGN-like emissions tend to feature an additional broad-emission-line component, leading to their classification as double-component galaxies. We explore the correlations between M* and gas velocity dispersions, highlighting that the prominence of the broad component significantly contributes to elevating the gas velocity dispersion. Galaxies displaying AGN-like emission based on optical definitions show enhanced gas velocity dispersions. In star-forming galaxies, both stellar mass and star-formation rate surface density substantially contribute to the velocity dispersion of the narrow component. Increased star-forming activity appears to elevate the velocity dispersion of the narrow component. The broad component exhibits a weaker dependence on stellar mass and is primarily driven by galactic outflows. We suggest that strong star-forming activity leads to the formation of a broad-emission-line component, but the impact on inflating gas velocity dispersion is moderate. On the other hand, AGN-driven outflows appear to be a more important contributor to the elevated velocity dispersion of the ionized gas.

VODKA-JWST: A 3.8 kpc Dual Quasar at Cosmic Noon in a Powerful Starburst Galaxy with JWST/MIRI Integral Field Unit

Dual quasars—two active supermassive black holes at galactic scales—represent crucial objects for studying the impact of galaxy mergers and quasar activity on the star formation rate (SFR) within their host galaxies, particularly at cosmic noon when SFR peaks. We present JWST/MIRI mid-infrared integral field spectroscopy of J074922.96+225511.7, a dual quasar with a projected separation of 3.8 kpc at a redshift z = 2.17. We detect spatially extended [Fe ii] 5.34 μm and polycyclic aromatic hydrocarbon (PAH) 3.3 μm emissions from the star formation activity in its host galaxy. We derive the SFR of 103.0±0.2 M ⊙ yr−1 using PAH 3.3 μm, which is 5 times higher than that derived from the knee of the infrared luminosity function for galaxies at z ∼ 2. While the SFR of J0749+2255 agrees with that of star-forming galaxies of comparable stellar mass at the same redshifts, its molecular gas content falls short of expectations based on the molecular Kennicutt–Schmidt law. This discrepancy may result from molecular gas depletion due to the longer elevated stage of star formation, even after the molecular gas reservoir is depleted. We do not observe any quasar-driven outflow that impacts PAH and [Fe ii] in the host galaxy based on the spatially resolved maps. From the expected flux in PAH-based star formation, the [Fe ii] line likely originates from the star-forming regions in the host galaxy. Our study highlights the extreme stardust nature of J0749+2255, indicating a potential connection between the dual quasar phase and intense star formation activities.

On the Origin of the Variety of Velocity Dispersion Profiles of Galaxies

Observed and simulated galaxies exhibit a significant variation in their velocity dispersion profiles. We examine the inner and outer slopes of stellar velocity dispersion profiles using integral field spectroscopy data from two surveys, SAMI (for z < 0.115) and CALIFA (for z < 0.03), comparing them with results from two cosmological hydrodynamic simulations: Horizon-AGN (for z = 0.017) and NewHorizon (for z ≲ 1). The simulated galaxies closely reproduce the variety of velocity dispersion slopes and stellar mass dependence of both inner and outer radii (0.5 r 50 and 3 r 50) as observed, where r 50 stands for half-light radius. The inner slopes are mainly influenced by the relative radial distribution of the young and old stars formed in situ: a younger center shows a flatter inner profile. The presence of accreted (ex situ) stars has two effects on the velocity dispersion profiles. First, because they are more dispersed in spatial and velocity distributions compared to in situ formed stars, it increases the outer slope of the velocity dispersion profile. It also causes the velocity anisotropy to be more radial. More massive galaxies have a higher fraction of stars formed ex situ and hence show a higher slope in outer velocity dispersion profile and a higher degree of radial anisotropy. The diversity in the outer velocity dispersion profiles reflects the diverse assembly histories among galaxies.

Are High-Σ1 Massive Blue Spiral Galaxies Rejuvenated Systems?

Quiescent galaxies generally possess denser cores than star-forming galaxies with similar mass. As a measurement of the core density, the central stellar mass surface density within a radius of 1 kpc (Σ1) was thus suggested to be closely related to galaxy quenching. Massive star-forming galaxies with high Σ1 do not fit into this picture. To understand the origin of such galaxies, we compare the spatially resolved stellar population and star formation properties of massive (>1010.5 M ⊙) blue spiral galaxies with high and low Σ1, divided by Σ1 = 109.4 M ⊙ kpc−2, based on the final release of MaNGA integral field unit data. We find that both high-Σ1 and low-Σ1 blue spirals show large diversities in stellar population and star formation properties. Despite the diversities, high-Σ1 blue spirals are statistically different from the low-Σ1 ones. Specifically, the radial profiles of the luminosity-weighted age and Mgb/〈Fe〉 show that high-Σ1 blue spirals consist of a larger fraction of galaxies with younger and less α-element-enhanced centers than their low-Σ1 counterparts, ∼55% versus ∼30%. The galaxies with younger centers mostly have higher central specific star formation rates, which still follow the spaxel-based star formation main-sequence relation. Examinations of the Hα velocity field and the optical structures suggest that galactic bars or galaxy interactions should be responsible for the rejuvenation of these galaxies. The remaining ∼45% of high-Σ1 blue spirals are consistent with the inside-out growth scenario.

Outshining in the spatially resolved analysis of a strongly lensed galaxy at z = 6.072 with JWST NIRCam

We present JWST/NIRCam observations of a strongly lensed, sub-L*, multiply imaged galaxy at z = 6.072, with magnification factors μ ≳ 20 across the galaxy. The galaxy has rich HST, MUSE, and ALMA ancillary observations across a broad wavelength range. Aiming to quantify the reliability of stellar mass estimates of high redshift galaxies, we performed a spatially resolved analysis of the physical properties at scales of ∼200 pc, inferred from spectral energy distribution (SED) modelling of five JWST/NIRCam imaging bands covering 0.16 μm &lt; λrest &lt; 0.63 μm on a pixel-by-pixel basis. We find young stars surrounded by extended older stellar populations. By comparing Hα+[N II] and [O III]+Hβ maps inferred from the image analysis with our additional NIRSpec integral field unit (IFU) data, we find that the spatial distribution and strength of the line maps are in agreement with the IFU measurements. We explore different parametric star formation history (SFH) forms with BAGPIPES on the spatially integrated photometry, finding that a double power-law (DPL) star formation history retrieves the closest value to the spatially resolved stellar mass estimate, and other SFH forms suffer from the dominant outshining emission from the youngest stars, thus underestimating the stellar mass – up to ∼0.5 dex. On the other hand, the DPL cannot match the IFU-measured emission lines. Additionally, the ionising photon production efficiency may be overestimated in a spatially integrated approach by ∼0.15 dex, when compared to a spatially resolved analysis. The agreement with the IFU measurements implies that our pixel-by-pixel results derived from the broadband images are robust, and that the mass discrepancies we find with spatially integrated estimates are not just an effect of SED-fitting degeneracies or the lack of NIRCam coverage. Additionally, this agreement points towards the pixel-by-pixel approach as a way to mitigate the general degeneracy between the flux excess from emission lines and underlying continuum, especially when lacking photometric medium-band coverage and/or IFU observations. This study stresses the importance of studying galaxies as the complex systems that they are, resolving their stellar populations when possible, or using more flexible SFH parameterisations. This can aid our understanding of the early stages of galaxy evolution by addressing the challenge of inferring robust stellar masses and ionising photon production efficiencies of high redshift galaxies.

GA-NIFS: The core of an extremely massive protocluster at the epoch of reionisation probed with JWST/NIRSpec

The SPT0311-58 system resides in a massive dark-matter halo at z sim 6.9. It hosts two dusty galaxies (E and W) with a combined star formation rate (SFR) of sim 3500 mostly obscured and identified by the rest-frame IR emission. The surrounding field exhibits an overdensity of submillimetre sources, making it a candidate protocluster. Our main goal is to characterise the environment and the properties of the interstellar medium (ISM) within this unique system. We used spatially resolved low-resolution ($R$=100) and high-resolution ($R$=2700) spectroscopy provided by the JWST/NIRSpec Integral Field Unit to probe a field of sim 17 times 17 kpc$^2$ around this object, with a spatial resolution of sim 0.5 kpc. These observations reveal ten new galaxies at zsim 6.9 characterised by dynamical masses spanning from sim 109 to 1010 and a range in radial velocity of sim 1500 in addition to the already known E and W galaxies. The implied large number density (phi sim $) and the wide spread in velocities confirm that is at the core of a protocluster immersed in a very massive dark-matter halo of sim (5 pm 3) times 1012 and therefore represents the most massive protocluster ever found at the epoch of reionisation (EoR). We also studied the dynamical stage of its core and find that it is likely not fully virialised. The galaxies in the system exhibit a wide range of properties and evolutionary stages. The contribution of the ongoing Halpha -based unobscured SFR to the total star formation (SF) varies significantly across the galaxies in the system. Their ionisation conditions range from those typical of the field galaxies at similar redshift recently studied with JWST to those found in more evolved objects at lower redshift, with OIII varying from sim 0.25 to 1. The metallicity spans more than 0.8 dex across the FoV, reaching nearly solar values in some cases. The detailed spatially resolved spectroscopy of the E galaxy reveals that it is actively assembling its stellar mass, showing inhomogeneities in the ISM properties at subkiloparsec scales, and a metallicity gradient (sim 0.1 dex/kpc) that can be explained by accretion of low metallicity gas from the intergalactic medium. The kinematic maps also depict an unsettled disc characterised by deviations from regular rotation, elevated turbulence, and indications of a possible precollision minor merger. These JWST/NIRSpec IFS observations confirm that is at the core of an extraordinary protocluster, and reveal details of its dynamical properties. They also unveil and provide insights into the diverse properties and evolutionary stages of the galaxies residing in this unique environment.

Toward mapping turbulence in the intra-cluster medium

Context. Future X-ray observatories with high spectral resolution and imaging capabilities will enable measurements and mappings of emission line shifts in the intracluster medium (ICM). Such direct measurements can serve as unique probes of turbulent motions in the ICM. Determining the level and scales of turbulence will improve our understanding of the galaxy cluster dynamical evolution and assembly, together with a more precise evaluation of the non thermal support pressure budget. This will allow for more accurate constraints to be placed on the masses of galaxy clusters, among other potential benefits. Aims. In this view, we implemented the methods presented in the previous instalments of our work to characterising the turbulence in the intra-cluster medium in a feasibility study with the X-ray Integral Field Unit (X-IFU) on board the future European X-ray observatory, Athena. Methods. From idealized mock observations of a toy model cluster, we reconstructed the second-order structure function built with the observed velocity field to constrain the turbulence. We carefully accounted for the various sources of errors to derive the most realistic and comprehensive error budget within the limits of our approach. With prior assumptions on the dissipation scale and power spectrum slope, we constrained the parameters of the turbulent power spectrum model through the use of Markov chain Monte Carlo (MCMC) sampling. Results. With a very long exposure time, a favourable configuration, and a prior assumption of the dissipation scale, we were able to retrieve the injection scale, velocity dispersion, and power spectrum slope, with 1σ uncertainties for better than ∼15% of the input values. We demonstrated the efficiency of our carefully set framework to constrain the turbulence in the ICM from high-resolution X-ray spectroscopic observations, paving the way for more in-depth investigation of the optimal required observing strategy within a more restrictive observational setup with the future Athena/X-IFU instrument.

Clumpy star formation and an obscured nuclear starburst in the luminous dusty z = 4 galaxy GN20 seen by MIRI/JWST

Dusty star-forming galaxies emit most of their light at far-infrared to millimeter wavelengths as their star formation is highly obscured. Far-infrared and millimeter observations have revealed their dust, neutral and molecular gas properties. The sensitivity of JWST at rest-frame optical and near-infrared wavelengths now allows the study of the stellar and ionized gas content. We investigate the spatially resolved distribution and kinematics of the ionized gas in GN20, a dusty star-forming galaxy at z = 4.0548. We present deep MIRI/MRS integral field spectroscopy of the near-infrared rest-frame emission of GN20. We detect spatially resolved Paα, out to a radius of 6 kpc, distributed in a clumpy morphology. The star formation rate derived from Paα (144 ± 9 M⊙ yr−1) is only 7.7 ± 0.5% of the infrared star formation rate (1860 ± 90 M⊙ yr−1). We attribute this to very high extinction (AV = 17.2 ± 0.4 mag, or AV, mixed = 44 ± 3 mag), especially in the nucleus of GN20, where only faint Paα is detected, suggesting a deeply buried starburst. We identify four, spatially unresolved, clumps in the Paα emission. Based on the double peaked Paα profile, we find that each clump consists of at least two sub-clumps. We find mass upper limits consistent with them being formed in a gravitationally unstable gaseous disk. The ultraviolet bright region of GN20 does not have any detected Paα emission, suggesting an age of more than 10 Myr for this region of the galaxy. From the rotation profile of Paα, we conclude that the gas kinematics are rotationally dominated and the vrot/σm = 3.8 ± 1.4 is similar to low-redshift luminous infrared galaxies. From the Paα kinematics, we cannot distinguish between a rotational profile of a large disk and a late stage merger mimicking a disk. We speculate that GN20 is in the late stage of a major merger, where the clumps in a large gas-rich disk are created by the major merger, while the central starburst is driven by the merger event.

The asymmetric bipolar [Fe II] jet and H2 outflow of TMC1A resolved with the JWST NIRSpec Integral Field Unit

Protostellar outflows exhibit large variations in their structure depending on the observed gas emission. To understand the origin of the observed variations, it is important to analyze the differences in the observed morphology and kinematics of the different tracers. The James Webb Space Telescope (JWST) allows us to study the physical structure of the protostellar outflow through well-known near-infrared shock tracers in a manner unrivaled by other existing ground-based and space-based telescopes at these wavelengths. This study analyzes the atomic jet and molecular outflow in the Class I protostar, TMC1A, utilizing spatially resolved Fe II and H2 lines to characterize the morphology and to identify previously undetected spatial features, and compare them to existing observations of TMC1A and its outflows observed at other wavelengths. We identified a large number of Fe II and H2 lines within the G140H, G235H, and G395H gratings of the NIRSpec IFU observations. We analyzed their morphology and position-velocity (PV) diagrams. From the observed Fe II line ratios, the extinction toward the jet is estimated. We detected the bipolar Fe jet by revealing, for the first time, the presence of a redshifted atomic jet. Similarly, the redshifted component of the H2 slower wide-angle outflow was observed. The Fe II and H2 redhifted emission both exhibit significantly lower flux densities compared to their blueshifted counterparts. Additionally, we report the detection of a collimated high-velocity ($ 100$ km $), blueshifted H2 outflow, suggesting the presence of a molecular jet in addition to the well-known wider angle low-velocity structure. The Fe II and H2 jets show multiple intensity peaks along the jet axis, which may be associated with ongoing or recent outburst events. In addition to the variation in their intensities, the H2 wide-angle outflow exhibits a ring-like structure. The blueshifted H2 outflow also shows a left-right brightness asymmetry likely due to interactions with the surrounding ambient medium and molecular outflows. Using the Fe II line ratios, the extinction along the atomic jet is estimated to be between $A_ V $ = 10--30 on the blueshifted side, with a trend of decreasing extinction with distance from the protostar. A similar $A_ V $ is found for the redshifted side, supporting the argument for an intrinsic red-blue outflow lobe asymmetry rather than environmental effects such as extinction. This intrinsic difference revealed by the unprecedented sensitivity of JWST, suggests that younger outflows already exhibit the red-blue side asymmetry more commonly observed toward jets associated with Class II disks.

NGC 1856: Using Machine Learning Techniques to Uncover Detailed Stellar Abundances from MUSE Data

We present the first application of the novel approach based on data-driven machine learning methods applied to Multi-Unit Spectroscopic Explorer (MUSE) field data to derive stellar abundances of star clusters. MUSE has been used to target more than 10,000 fields, and it is unique in its ability to study dense stellar fields such as stellar clusters providing spectra for each individual star. We use MUSE data of the extragalactic young stellar cluster NGC 1856, located in the Large Magellanic Cloud (LMC). We present the individual stellar [Fe/H] abundance of 327 cluster members in addition to [Mg/Fe], [Si/Fe], [Ti/Fe], [C/Fe], [Ni/Fe], and [Cr/Fe] abundances of subsample sets. Our results match the LMC abundances obtained in the literature for [Mg/Fe], [Ti/Fe], [Ni/Fe], and [Cr/Fe]. This study is the first to derive [Si/Fe] and [C/Fe] abundances for this cluster. The revolutionary combination of integral-field spectroscopy and data-driven modeling will allow us to understand the chemical enrichment of star clusters and their host galaxies in greater detail expanding our understanding of galaxy evolution.

Exploring the directly imaged HD 1160 system through spectroscopic characterization and high-cadence variability monitoring

ABSTRACT The time variability and spectra of directly imaged companions provide insight into their physical properties and atmospheric dynamics. We present follow-up R ∼ 40 spectrophotometric monitoring of red companion HD 1160 B at 2.8–4.2 μm using the double-grating 360° vector Apodizing Phase Plate (dgvAPP360) coronagraph and ALES integral field spectrograph on the Large Binocular Telescope Interferometer. We use the recently developed technique of gvAPP-enabled differential spectrophotometry to produce differential light curves for HD 1160 B. We reproduce the previously reported ∼3.2 h periodic variability in archival data, but detect no periodic variability in new observations taken the following night with a similar 3.5 per cent level precision, suggesting rapid evolution in the variability of HD 1160 B. We also extract complementary spectra of HD 1160 B for each night. The two are mostly consistent, but the companion appears fainter on the second night between 3.0–3.2 μm. Fitting models to these spectra produces different values for physical properties depending on the night considered. We find an effective temperature Teff = $2794^{+115}_{-133}$ K on the first night, consistent with the literature, but a cooler Teff = $2279^{+79}_{-157}$ K on the next. We estimate the mass of HD 1160 B to be 16–81 MJup, depending on its age. We also present R = 50 000 high-resolution optical spectroscopy of host star HD 1160 A obtained simultaneously with the PEPSI spectrograph. We reclassify its spectral type to A1 IV-V and measure its projected rotational velocity $\upsilon \sin i$ = $96^{+6}_{-4}$ km s−1. We thus highlight that gvAPP-enabled differential spectrophotometry can achieve repeatable few per cent level precision and does not yet reach a systematic noise floor, suggesting greater precision is achievable with additional data or advanced detrending techniques.