MUSE Data Research Articles

The MUSEHubbleUltra Deep Field surveys: Data release II

We present the second data release of the MUSEHubbleUltra-Deep Field surveys, which includes the deepest spectroscopic survey ever performed. The MUSE data, with their 3D content, amazing depth, wide spectral range, and excellent spatial and medium spectral resolution, are rich in information. Their location in theHubbleultra-deep field area, which benefits from an exquisite collection of ancillary panchromatic information, is a major asset. This update of the first release incorporates a new 141-h adaptive-optics-assisted MUSE eXtremely Deep Field (MXDF; 1 arcmin diameter field of view) in addition to the reprocessed 10-h mosaic (3 × 3 arcmin2) and the single 31-h deep field (1 × 1 arcmin2). All three data sets were processed and analyzed homogeneously using advanced data reduction and analysis methods. The 3σpoint-source flux limit of an unresolved emission line reaches 3.1 × 10−19and 6.3 × 10−20 erg s−1 cm−2at 10- and 141-h depths, respectively. We have securely identified and measured the redshift of 2221 sources, an increase of 41% compared to the first release. With the exception of eight stars, the collected sample consists of 25 nearby galaxies (z < 0.25), 677 [O II] emitters (z= 0.25 − 1.5), 201 galaxies in the MUSE redshift desert range (z = 1.5 − 2.8), and 1308 Lyαemitters (z = 2.8 − 6.7). This represents an order of magnitude more redshifts than the collection of all spectroscopic redshifts obtained before MUSE in theHubbleultra-deep field area (i.e., 2221 versus 292). At high redshift (z > 3), the difference is even more striking, with a factor of 65 increase (1308 versus 20). We compared the measured redshifts against three published photometric redshift catalogs and find the photo-z accuracy to be lower than the constraints provided by photo-z fitting codes. Eighty percent of the galaxies in our final catalog have an HST counterpart. These galaxies are on average faint, with a median ABF775Wmagnitude of 25.7 and 28.7 for the [O II] and Lyαemitters, respectively. Fits of their spectral energy distribution show that these galaxies tend to be low-mass star-forming galaxies, with a median stellar mass of 6.2 × 108 M⊙and a median star-formation rate of 0.4 M⊙yr−1. We measured the completeness of our catalog with respect to HST and found that, in the deepest 141-h area, 50% completeness is achieved for an AB magnitude of 27.6 and 28.7 (F775W) atz= 0.8 − 1.6 andz = 3.2 − 4.5, respectively. Twenty percent of our catalog, or 424 galaxies, have no HST counterpart. The vast majority of these new sources are high equivalent-widthz > 2.8 Lyαemitters that are detected by MUSE thanks to their bright and asymmetric broad Lyαline. We release advanced data products, specific software, and a web interface to select and download data sets.

MusE GAs FLOw and Wind (MEGAFLOW) IX. The impact of gas flows on the relations between the mass, star formation rate, and metallicity of galaxies

ABSTRACTWe study the link between gas flow events and key galaxy scaling relations: the relations between star formation rate (SFR) and stellar mass (the main sequence, MS); gas metallicity and stellar mass (the mass–metallicity relation, MZR); and gas metallicity, stellar mass, and SFR (the fundamental metallicity relation, FMR). Using all star-forming galaxies (SFGs) in the 22 MUSE fields of the MusE GAs FLOw and Wind (MEGAFLOW) survey, we derive the MS, MZR, and FMR scaling relations for 385 SFGs with $M_\star = 10^{8} - 10^{11.5}\, {\rm M}_\odot$ at redshifts 0.35 < z < 0.85. Using the MUSE data and complementary X-Shooter spectra at 0.85 < z < 1.4, we determine the locations of 21 SFGs associated with inflowing or outflowing circumgalactic gas (i.e. with strong Mg ii absorption in background quasar spectra) relative to these scaling relations. Compared to a control sample of galaxies without gas flows (i.e. without Mg ii absorption within 70 kpc of the quasar), SFGs with inflow events (i.e. Mg ii absorption along the major axis) are preferentially located above the MS, while SFGs with outflow events (i.e. Mg ii absorption along the minor axis) are preferentially more metal rich. Our observations support the scenario in which gas accretion increases the SFR while diluting the metal content and where circumgalactic outflows are found in more metal-rich galaxies.

MUSE crowded field 3D spectroscopy in NGC 300

Context. There are known differences between the physical properties of H II and diffuse ionized gas (DIG). However, most of the studied regions in the literature are relatively bright, with log10 L(Hα)[erg s−1] ≳ 37. Aims. We compiled an extremely faint sample of 390 H II regions with a median Hα luminosity of 34.7 in the flocculent spiral galaxy NGC 300, derived their physical properties in terms of metallicity, density, extinction, and kinematics, and performed a comparative analysis of the properties of the DIG. Methods. We used MUSE data of nine fields in NGC 300, covering a galactocentric distance of zero to ~450 arcsec (~4 projected kpc), including spiral arm and inter-arm regions. We binned the data in dendrogram leaves and extracted all strong nebular emission lines. We identified H II and DIG regions and compared their electron densities, metallicity, extinction, and kinematic properties. We also tested the effectiveness of unsupervised machine-learning algorithms in distinguishing between the H II and DIG regions. Results. The gas density in the H II and DIG regions is close to the low-density limit in all fields. The average velocity dispersion in the DIG is higher than in the H II regions, which can be explained by the DIG being 1.8 kK hotter than H II gas. The DIG manifests a lower ionization parameter than H II gas, and the DIG fractions vary between 15–77%, with strong evidence of a contribution by hot low-mass evolved stars and shocks to the DIG ionization. Most of the DIG is consistent with no extinction and an oxygen metallicity that is indistinguishable from that of the H II gas. We observe a flat metallicity profile in the central region of NGC 300, without a sign of a gradient. Conclusions. The differences between extremely faint H II and DIG regions follow the same trends and correlations as their much brighter cousins. Both types of objects are so heterogeneous, however, that the differences within each class are larger than the differences between the two classes.

JWST unveils a population of “red-excess” galaxies in Abell2744 and in the coeval field

AbstractWe combine JWST/NIRCam imaging and MUSE data to characterize the properties of galaxies in the cluster Abell2744 (z=0.3064) and in its immediate surroundings. We discover a “red-excess” population in F200W–F444W colors in both the cluster regions and the field. These galaxies have normal F115W-F150W colors and rather blue rest frame B–V colors, but are up to 0.8 mag redder than red sequence galaxies in F200W–F444W. Considering morphology, many cluster galaxies show signatures consistent with ram pressure stripping, while field galaxies have features resembling interactions and mergers. Our hypothesis is that these galaxies are characterized by dust enshrouded star formation: a JWST/NIRSpec spectrum for one of the galaxies is dominated by a strong PAH at 3.3 μm, suggestive of dust obscured star formation.

Morpho-kinematics of MACS J0416.1-2403 low-mass galaxies

We use optical integral field spectroscopy from VLT/MUSE, as well as photometric observations from Hubble Space Telescope and VLT/HAWK-I, to study the morpho-kinematics of 17 low-mass (log(M/M⊙) < 9.5) MACS J0416.1-2403 cluster galaxies at R200 and five field galaxies with a redshift of z ∼ 0.4. By measuring fluxes of strong emission lines from the MUSE data, we have recovered the star formation rates, gas-phase metallicities, and spatially resolved gas kinematics, and we have also investigated the ionising mechanisms. We have analysed the structure and morphology of the galaxies from the optical and infrared photometric data, performing a multi-component decomposition into a bulge and a disk. The spatially resolved gas velocity fields of the cluster members and field galaxies were modelled using a 3D approach, which allowed us to retrieve their intrinsic gas kinematics, including the maximum rotation velocity and velocity dispersion. This enabled us to study scaling relations such as the Tully–Fisher and the stellar mass–S0.5 relation for low-mass galaxies in different environments and to search for signatures of cluster-specific processes using disturbed gas velocity fields as tracers. Most galaxies from our sample fall in the star-forming and composite region in the diagnostic diagram, which allows for the ionising sources in a galaxy to be disentangled. The cluster and field population can be classified as star-forming main-sequence galaxies, with only a sub-sample of four quenched systems. We observe significant scatter for the cluster galaxies in the mass-metallicity plane, and the lowest-mass systems deviate from the predictions of the fundamental metallicity relation, showing higher metallicities, whereas the higher-mass ones are in accordance with the model predictions. This might hint at the cutoff of pristine gas inflow and/or the removal of the hot halo gas as the mechanisms driving these offsets. Our morpho-kinematic analysis reveals a sub-sample of dwarfs with maximum velocities vmax < 50 km s−1 and vmax, gas/σgas < 1, which depart from the Tully–Fisher relation. This might indicate that their interstellar medium is affected by external environmental processes, such as ram pressure stripping. However, ∼30% of the cluster galaxies have rotation-dominated gas disks and follow the Tully–Fisher relation within 1σ. Using the S0.5 parameter, which links the dynamical support of ordered motions with that of random motions, we can differentiate between galaxies affected by gravitational processes and systems affected by hydrodynamical ones. In the stellar mass–S0.5 plane, both cluster and field galaxies follow a tight sequence, with only a sub-population of five galaxies strongly departing (> 4σ) from this relation, showing high σgas values. Both the morphology and kinematics of the outlier galaxies hint at a combination of pre-processing and cluster-specific interactions affecting their stellar and gas disks.

Spatially resolved properties of early-type group-dominant galaxies with MUSE: gas content, ionization mechanisms, and metallicity gradients

ABSTRACT With the goal of a thorough investigation of the ionized gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). These data allowed us to study the spatially resolved warm gas properties, including the morphology of the ionized gas, EW(H α), and kinematics as well as the gas-phase metallicity (12 + log(O/H)) of these systems. In order to distinguish between different ionization mechanisms, we used the emission-line ratios [O iii]/H β and [N ii]/H α in the BPT diagrams and EW(H α). We find that the ionization sources in our sample have variable impacts at different radii; central regions are more influenced by low-luminosity active galactic nuclei, while extended regions of low-ionization nuclear emission-line region-like emission are ionized by other mechanisms with post-asymptotic giant branch stars photoionization likely contributing significantly. We classified our sample into three H α +[N ii] emission morphology types. We calculate the gas-phase metallicity assuming several methods and ionization sources. In general, 12 + log(O/H) decreases with radius from the centre for all galaxies, independently of nebular morphology type, indicating a metallicity gradient in the abundance profiles. Interestingly, the more extended filamentary structures and all extranuclear star-forming regions present shallow metallicity gradients. Within the uncertainties these extended structures can be considered chemically homogeneous. We suggest that group-dominant galaxies in our sample likely acquired their cold gas in the past as a consequence of one or more mechanisms, e.g. gas-clouds or satellite mergers/accretion and/or cooling flows that contribute to the growth of the ionized gas structures.

Unexplored outflows in nearby low luminosity AGNs

Context. Multi-phase outflows play a central role in galaxy evolution shaping the properties of galaxies. Understanding outflows and their effects in low luminosity active galactic nuclei (AGNs), such as low ionisation nuclear emission line regions (LINERs), is essential. LINERs bridge the gap between normal and active galaxies, being the most numerous AGN population in the local Universe. Aims. Our goal is to analyse the kinematics and ionisation mechanisms of the multi-phase gas of NGC 1052, the prototypical LINER, in order to detect and map the ionised and neutral phases of the putative outflow. Methods. We obtained Very Large Telescope MUSE and Gran Telescopio Canarias MEGARA optical integral field spectroscopy data for NGC 1052. In addition to stellar kinematics maps, by modelling spectral lines with multiple Gaussian components, we obtained flux, kinematic, and excitation maps of both ionised and neutral gas. Results. The stars are distributed in a dynamically hot disc (V/σ ∼ 1.2), with a centrally peaked velocity dispersion map (σc = 201 ± 10 km s−1) and large observed velocity amplitudes (ΔV = 167 ± 19 km s−1). The ionised gas, probed by the primary component is detected up to ∼30″ (∼3.3 kpc) mostly in the polar direction with blue and red velocities (∣V∣ < 250 km s−1). The velocity dispersion map shows a notable enhancement (σ > 90 km s−1) crossing the galaxy along the major axis of rotation in the central 10″. The secondary component has a bipolar morphology, velocity dispersion larger than 150 km s−1, and velocities up to 660 km s−1. A third component is detected with MUSE (and barely with MEGARA), but it is not spatially resolved. The broad-line region (BLR) component (used to model the broad Hα emission only) has a full width at half maximum of 2427 ± 332 and 2350 ± 470 km s−1 for MUSE and MEGARA data, respectively. The maps of the NaD absorption indicate optically thick neutral gas with complex kinematics. The velocity field is consistent with a slow rotating disc (ΔV = 77 ± 12 km s−1), but the velocity dispersion map is off-centred without any counterpart in the (centrally peaked) flux map. Conclusions. We found evidence of an ionised gas outflow (secondary component) with a mass of 1.6 ± 0.6 × 105 M⊙, and mass rate of 0.4 ± 0.2 M⊙ yr−1. The outflow is propagating in a cocoon of gas with enhanced turbulence and might be triggering the onset of kiloparsec-scale buoyant bubbles (polar emission), both probed by the primary component. Taking into account the energy and kinetic power of the outflow (1.3 ± 0.9 × 1053 erg and 8.8 ± 3.5 × 1040 erg s−1, respectively) as well as its alignment with both the jet and the cocoon, and that the gas is collisionally ionised (due to gas compression), we consider that the most likely power source of the outflow is the jet, although some contribution from the AGN is possible. The hints of the presence of a neutral gas outflow are weak.

Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. I. 2D Optical Spectroscopy

We use panoramic optical spectroscopy obtained with the Very Large Telescope/MUSE to investigate the nature of five candidate extremely isolated low-mass star-forming regions (Blue Candidates; hereafter, BCs) toward the Virgo cluster of galaxies. Four of the five (BC1, BC3, BC4, and BC5) are found to host several H ii regions and to have radial velocities fully compatible with being part of the Virgo cluster. All the confirmed candidates have mean metallicity significantly in excess of that expected from their stellar mass, indicating that they originated from gas stripped from larger galaxies. In summary, these four candidates share the properties of the prototype system SECCO 1, suggesting the possible emergence of a new class of stellar systems, intimately linked to the complex duty cycle of gas within clusters of galaxies. A thorough discussion of the nature and evolution of these objects is presented in a companion paper, where the results obtained here from the MUSE data are complemented with Hubble Space Telescope (optical) and Very Large Array (Hi) observations.

The MUSE eXtremely deep field: first panoramic view of an Mg II emitting intragroup medium

Using the exquisite data from the MUSE eXtremely Deep Field (MXDF), we report the discovery of an Mg II emission nebula with an area above a 2σ significance level of 1000 proper kpc2. This provides the first panoramic view of the spatial distribution of magnesium in the intragroup medium of a low-mass group of five star-forming galaxies at z = 1.31. The galaxy group members are separated by less than 50 physical kpc in projection and ≈120 km s−1 in velocity space. The most massive galaxy has a stellar mass of 109.35 M⊙ and shows an Mg II P-Cygni line profile, indicating the presence of an outflow, which is consistent with the spatially resolved spectral analysis showing ≈+120 km s−1 shift of the Mg II emission lines with respect to the systemic redshift. The other galaxies are less massive and only show Mg II in emission. The detected Mg II nebula has a maximal projected extent of ≈70 kpc, including a low-surface-brightness (≈2 × 10−19 erg s−1 cm−2 arcsec−2) gaseous bridge between two subgroups of galaxies. The presence of absorption features in the spectrum of a background galaxy located at an impact parameter of 19 kpc from the closest galaxy of the group indicates the presence of gas enriched in magnesium even beyond the detected nebula seen in emission, which suggests that we are observing the tip of a larger intragroup medium. The observed Mg II velocity gradient suggests an overall rotation of the structure along the major axis of the most massive galaxy. Our MUSE data also reveal extended Fe II* emission in the vicinity of the most massive galaxy, aligned with its minor axis and pointing towards a neighboring galaxy. Extended [O II] emission is found around the galaxy group members and at the location of the Mg II bridge. Our results suggest that both tidal stripping effects from galaxy interactions and outflows are enriching the intragroup medium of this system.

The morphology of the HD 163296 jet as a window on its planetary system

Context. HD 163296 is a Herbig Ae star which drives a bipolar knotty jet with a total length of ~6000 au. Strong evidence exists that the disk of HD 163296 harbors planets. Studies have shown that the presence of companions around jet-driving stars could affect the morphology of the jets. This includes a ‘wiggling’ of the jet axis and a periodicity in the positions of the jet knots. Aims. In this study we investigate the morphology (including the jet width and axis position) and proper motions of the HD 163296 jets, and use our results to better understand the whole system. Methods. This study is based on optical integral-field spectroscopy observations obtained with VLT/MUSE in 2017. Using spectro-images and position velocity diagrams extracted from the MUSE data cube, we investigated the number and positions of the jet knots. A comparison was made to X-shooter data collected in 2012 and the knot proper motions were estimated. The jet width and jet axis position with distance from the star were studied from the extracted spectro-images. This was done using Gaussian fitting to spatial profiles of the jet emission extracted perpendicular to the position angle of the jet. The centroid of the fit is taken as the position of the jet axis. Results. We observe the merging of knots and identify two previously undetected knots. We find proper motions that are broadly in agreement with previous studies. The jet width increases with distance from the source and we measure an opening angle of ~5° and 2.5° for the red and blue lobes, respectively. Measurements of the jet axis position, derived from Gaussian centroids of transverse intensity profiles, reveal a similar pattern of deviation in all forbidden emission lines along the first 20 arcsec of the jets. This result is interpreted as being due to asymmetric shocks and not due to a wiggling of the jet axis. Conclusions. The number of new knots detected and their positions challenge the 16-yr knot ejection periodicity proposed in prior studies, arguing for a more complicated jet system than was previously assumed. We use the non-detection of a jet axis wiggling to rule out companions with a mass >0.1 M⊙ and orbits between 1 au and 35 au. Any object inferred at these distances using other methods must be a brown dwarf or planet, otherwise it would have impacted the jet axis position. Both the precession and orbital motion scenarios are considered. Overall it is concluded that it is difficult to detect planets with orbits >1 au through a study of the jet axis.

Physics of ULIRGs with MUSE and ALMA: The PUMA project

Context. A classical scenario suggests that ultra-luminous infrared galaxies (ULIRGs) transform colliding spiral galaxies into a spheroid-dominated early-type galaxy. Recent high-resolution simulations have instead shown that, under some circumstances, rotation disks can be preserved during the merging process or rapidly regrown after coalescence. Our goal is to analyse in detail the ionised gas kinematics in a sample of ULIRGs to infer the incidence of gas rotational dynamics in late-stage interacting galaxies and merger remnants. Aims. We analysed integral field spectrograph MUSE data of a sample of 20 nearby (z < 0.165) ULIRGs (with 29 individual nuclei) as part of the Physics of ULIRGs with MUSE and ALMA (PUMA) project. We used multi-Gaussian fitting techniques to identify gaseous disk motions and the 3D-Barolo tool to model them. Methods. We found that 27% (8 out of 29) individual nuclei are associated with kiloparsec-scale disk-like gas motions. The rest of the sample displays a plethora of gas kinematics, dominated by winds and merger-induced flows, which makes the detection of rotation signatures difficult. On the other hand, the incidence of stellar disk-like motions is ∼2 times larger than gaseous disks, as the former are probably less affected by winds and streams. The eight galaxies with a gaseous disk present relatively high intrinsic gas velocity dispersion (σ0 ∈ [30 − 85] km s−1), rotationally supported motions (with gas rotation velocity over velocity dispersion vrot/σ0 ∼ 1 − 8), and dynamical masses in the range (2 − 7)×1010 M⊙. By combining our results with those of local and high-z disk galaxies (up to z ∼ 2) from the literature, we found a significant correlation between σ0 and the offset from the main sequence (δMS), after correcting for their evolutionary trends. Results. Our results confirm the presence of kiloparsec-scale rotating disks in interacting galaxies and merger remnants in the PUMA sample, with an incidence going from 27% (gas) to ≲50% (stars). Their gas σ0 is up to a factor of ∼4 higher than in local normal main sequence galaxies, similar to high-z starbursts as presented in the literature; this suggests that interactions and mergers enhance the star formation rate while simultaneously increasing the velocity dispersion in the interstellar medium.

Deciphering stellar metallicities in the early Universe: case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field

Directly characterising the first generations of stars in distant galaxies is a key quest of observational cosmology. We present a case study of ID53 at z = 4.77, the UV-brightest (but L⋆) star-forming galaxy at z > 3 in the MUSE eXtremely Deep Field with a mass of ≈109 M⊙. In addition to very strong Lyman-α (Lyα) emission, we clearly detect the (stellar) continuum and an N V P Cygni feature, interstellar absorption, fine-structure emission and nebular C IV emission lines in the 140 h spectrum. Continuum emission from two spatially resolved components in Hubble Space Telescope data are blended in the MUSE data, but we show that the nebular C IV emission originates from a subcomponent of the galaxy. The UV spectrum can be fit with recent BPASS stellar population models combined with single-burst or continuous star formation histories (SFHs), a standard initial mass function, and an attenuation law. Models with a young age and low metallicity (log10(age/yr) = 6.5–7.6 and [Z/H] = −2.15 to −1.15) are preferred, but the details depend on the assumed SFH. The intrinsic Hα luminosity of the best-fit models is an order of magnitude higher than the Hα luminosity inferred from Spitzer/IRAC data, which either suggests a high escape fraction of ionising photons, a high relative attenuation of nebular to stellar dust, or a complex SFH. The metallicity appears lower than the metallicity in more massive galaxies at z = 3 − 5, consistent with the scenario according to which younger galaxies have lower metallicities. This chemical immaturity likely facilitates Lyα escape, explaining why the Lyα equivalent width is anti-correlated with stellar metallicity. Finally, we stress that uncertainties in SFHs impose a challenge for future inferences of the stellar metallicity of young galaxies. This highlights the need for joint (spatially resolved) analyses of stellar spectra and photo-ionisation models.

HR 6819 is a binary system with no black hole

Context. Two scenarios have been proposed to match the existing observational constraints of the object HR 6819. The system could consist of a close inner B-type giant plus a black hole (BH) binary with an additional Be companion in a wide orbit. Alternatively, it could be a binary composed of a stripped B star and a Be star in a close orbit. Either scenario makes HR 6819 a cornerstone object as the stellar BH closest to Earth, or as an example of an important transitional, non-equilibrium phase for Be stars with solid evidence for its nature. Aims. We aim to distinguish between the two scenarios for HR 6819. Both models predict two luminous stars but with very different angular separations and orbital motions. Therefore, the presence of bright sources in the 1−100 milliarcsec (mas) regime is a key diagnostic for determining the nature of the HR 6819 system. Methods. We obtained new high-angular resolution data with VLT/MUSE and VLTI/GRAVITY of HR 6819. The MUSE data are sensitive to bright companions at large scales, whilst the interferometric GRAVITY data are sensitive down to separations on mas scales and large magnitude differences. Results. The MUSE observations reveal no bright companion at large separations and the GRAVITY observations indicate the presence of a stellar companion at an angular separation of ∼1.2 mas that moves on the plane of the sky over a timescale compatible with the known spectroscopic 40-day period. Conclusions. We conclude that HR 6819 is a binary system and that no BH is present in the system. The unique nature of HR 6819, and its proximity to Earth make it an ideal system for quantitatively characterising the immediate outcome of binary interaction and probing how Be stars form.

FSR 1776: A new globular cluster in the Galactic bulge?

Context. Recent near-IR surveys have uncovered a plethora of new globular cluster (GC) candidates towards the Milky Way bulge. These new candidates need to be confirmed as real GCs and properly characterised. Aims. We investigate the physical nature of FSR 1776, a very interesting star cluster projected towards the Galactic bulge. This object was originally classified as an intermediate-age open cluster, and has recently been re-discovered independently and classified as a GC candidate (Minni 23). Firstly, our aim is to confirm its GC nature; secondly, we determine its physical parameters. Methods. The confirmation of the cluster existence is checked using the radial velocity (RV) distribution of a MUSE data cube centred at FSR 1776. The cluster parameters are derived from isochrone fitting to the RV-cleaned colour-magnitude diagrams (CMDs) from visible and near-IR photometry taken from VVV, 2MASS, DECAPS, and Gaia all together. Results. The predicted RV distribution for the FSR 1776 coordinates, considering only contributions from the bulge and disc field stars, is not enough to explain the observed MUSE RV distribution. The extra population (12% of the sample) is FSR 1776 with an average RV of −103.7 ± 0.4 km s−1. The CMDs reveal that it is 10 ± 1 Gyr metal-rich population with [Fe/H]phot ≈ +0.2 ± 0.2, [Fe/H]spec = +0.02 ± 0.01(σ = 0.14 dex), located at the bulge distance of 7.24 ± 0.5 kpc with AV ≈ 1.1 mag. The mean cluster proper motions are (⟨μα⟩,⟨μδ⟩) = (−2.3 ± 1.1, −2.6 ± 0.8) mas yr−1. Conclusions. FSR 1776 is an old GC located in the Galactic bulge with a super-solar metallicity, among the highest for a Galactic GC. This is consistent with predictions for the age–metallicity relation of the bulge, being FSR 1776 the probable missing link between typical GCs and the metal-rich bulge field. High-resolution spectroscopy of a larger field of view and deeper CMDs are now required for a full characterisation.

Increasing power in the analysis of responder endpoints in rheumatology: a software tutorial

BackgroundComposite responder endpoints feature frequently in rheumatology due to the multifaceted nature of many of these conditions. Current analysis methods used to analyse these endpoints discard much of the data used to classify patients as responders and are therefore highly inefficient, resulting in low power. We highlight a novel augmented methodology that uses more of the information available to improve the precision of reported treatment effects. Since these methods are more challenging to implement, we developed free, user-friendly software available in a web-based interface and as R packages. The software consists of two programs: one that supports the analysis of responder endpoints; the second that facilitates sample size estimation. We demonstrate the use of the software to conduct the analysis with both the augmented and standard analysis method using the MUSE study, a phase IIb trial in patients with systemic lupus erythematosus.ResultsThe software outputs similar point estimates with smaller confidence intervals for the odds ratio, risk ratio and risk difference estimators using the augmented approach. The sample size required in each arm for a future trial using the novel approach based on the MUSE data is 50 versus 135 for the standard method, translating to a reduction in required sample size of approximately 63%.ConclusionsWe encourage trialists to use the software demonstrated to implement the augmented methodology in future studies to improve efficiency.

Recovery and analysis of rest-frame UV emission lines in 2052 galaxies observed with MUSE at 1.5 <z< 6.4

Rest-frame ultraviolet (UV) emission lines probe electron densities, gas-phase abundances, metallicities, and ionization parameters of the emitting star-forming galaxies and their environments. The strongest main UV emission line, Lyα, has been instrumental in advancing the general knowledge of galaxy formation in the early universe. However, observing Lyαemission becomes increasingly challenging atz ≳ 6 when the neutral hydrogen fraction of the circumgalactic and intergalactic media increases. Secondary weaker UV emission lines provide important alternative methods for studying galaxy properties at high redshift. We present a large sample of rest-frame UV emission line sources at intermediate redshift for calibrating and exploring the connection between secondary UV lines and the emitting galaxies’ physical properties and their Lyαemission. The sample of 2052 emission line sources with 1.5 < z < 6.4 was collected from integral field data from the MUSE-Wide and MUSE-Deep surveys taken as part of Guaranteed Time Observations. The objects were selected through untargeted source detection (i.e., no preselection of sources as in dedicated spectroscopic campaigns) in the three-dimensional MUSE data cubes. We searched optimally extracted one-dimensional spectra of the full sample for UV emission features via emission line template matching, resulting in a sample of more than 100 rest-frame UV emission line detections. We show that the detection efficiency of (non-Lyα) UV emission lines increases with survey depth, and that the emission line strength of He IIλ1640 Å, [O III]λ1661 + O III]λ1666, and [Si III]λ1883 + Si III]λ1892 correlate with the strength of [C III]λ1907 + C III]λ1909. The rest-frame equivalent width (EW0) of [C III]λ1907 + C III]λ1909 is found to be roughly 0.22 ± 0.18 of EW0(Lyα). We measured the velocity offsets of resonant emission lines with respect to systemic tracers. For C IVλ1548 + C IVλ1551 we find that ΔvC IV≲ 250 km s−1, whereas ΔvLyαfalls in the range of 250−500 km s−1which is in agreement with previous results from the literature. The electron densitynemeasured from [Si III]λ1883 + Si III]λ1892 and [C III]λ1907 + C III]λ1909 line flux ratios is generally < 105cm−3and the gas-phase abundance is below solar at 12 + log10(O/H)≈8. Lastly, we used “PhotoIonization Model Probability Density Functions” to infer physical parameters of the full sample and individual systems based on photoionization model parameter grids and observational constraints from our UV emission line searches. This reveals that the UV line emitters generally have ionization parameter log10(U) ≈ −2.5 and metal mass fractions that scatter aroundZ ≈ 10−2, that isZ ≈ 0.66 Z⊙. Value-added catalogs of the full sample of MUSE objects studied in this work and a collection of UV line emitters from the literature are provided with this paper.

The Fornax 3D project: PNe populations and stellar metallicity in edge-on galaxies

Context. Extragalactic planetary nebulae (PNe) are useful distance indicators and are often used to trace the dark-matter content in external galaxies. At the same time, PNe can also be used as probes of their host galaxy stellar populations and to help understand the later stages of stellar evolution. Previous works have indicated that a specific number of PNe per stellar luminosity can vary across different galaxies and as a function of stellar-population properties, for instance increasing with decreasing stellar metallicity. Aims. In this study we further explore the importance of stellar metallicity in driving the properties of the PNe population in early-type galaxies, using three edge-on galaxies in the Fornax cluster offering a clear view into their predominantly metal-rich and metal-poor regions near the equatorial plane or both below and above it, respectively. Methods. Using very large telescope-multi unit spectroscopic explorer (VLT-MUSE) integral-field observations and dedicated PNe detection procedures, we constructed the PNe luminosity function and computed the luminosity-specific number of PNe α in both in- and off-plane regions of our edge-on systems. Results. Comparing these α values with metallicity measurements also based on the same MUSE data, we find no evidence for an increase in the specific abundance of PNe when transitioning between metal-rich and metal-poor regions. Conclusions. Our analysis highlights the importance of ensuring spatial consistency to avoid misleading results when investigating the link between PNe and their parent stellar populations, and suggest that in passively evolving systems variations in the specific number of PNe may pertain to rather extreme metallicity regimes found either in the innermost or outermost regions of galaxies.

The spatially resolved view of star formation in galaxy clusters

AbstractIntegral field spectroscopic studies of galaxies in dense environments, such as clusters and groups of galaxies, have provided new insights for understanding how star formation proceeds, and quenches. I present the spatially resolved view of the star formation activity and its link with the multiphase gas in cluster galaxies based on MUSE and multi-wavelength data of the GASP survey. I discuss the link among the different scales (i.e. the link between the spatially resolved and the global star formation rate-stellar mass relation), the spatially resolved signatures and the quenching histories of jellyfish (progenitors) and post-starburst (descendants) galaxies in clusters. Finally, I discuss the multi-wavelength view of star-forming clumps both in galaxy disks and in the tails of stripped gas.

A triple active galactic nucleus in the NGC 7733–7734 merging group

Context. Galaxy interactions and mergers can lead to supermassive black hole (SMBH) binaries, which become active galactic nucleus (AGN) pairs when the SMBHs start accreting mass. If there is a third galaxy involved in the interaction, then a triple-AGN system can form. Aims. Our goal is to investigate the nature of the nuclear emission from the galaxies in the interacting pair NGC 7733–NGC 7734 using archival VLT/MUSE integral field spectrograph data and study its relation to the stellar mass distribution traced by near-infrared (NIR) observations from the South African Astronomical Observatory (SAAO). Methods. We conducted NIR observations using the SAAO and identified the morphological properties of bulges in each galaxy. We used MUSE data to obtain a set of ionized emission lines from each galaxy and studied the ionization mechanism. We also examined the relation of the galaxy pair with any nearby companions with far-ultraviolet observations using the UVIT. Results. The emission line analysis from the central regions of NGC 7733 and NGC 7734 shows Seyfert and low ionization nuclear emission-line regions type AGN activity. The galaxy pair NGC 7733−34 also shows evidence of a third component, which has Seyfert-like emission. Hence, the galaxy pair NGC 7733−34 forms a triple-AGN system. We also detected an extended narrow-line region associated with the nucleus of NGC 7733.

Toward Precision Cosmology with Improved PNLF Distances Using VLT-MUSEI. Methodology and Tests

Abstract The [O iii] λ5007 planetary nebula luminosity function (PNLF) is an established distance indicator that has been used for more than 30 yr to measure the distances of galaxies out to ∼15 Mpc. With the advent of the Multi-Unit Spectroscopic Explorer on the Very Large Telescope (MUSE) as an efficient wide-field integral-field spectrograph, the PNLF method is due for a renaissance, as the spatial and spectral information contained in the instrument’s data cubes provides many advantages over classical narrowband imaging. Here we use archival MUSE data to explore the potential of a novel differential emission-line filter (DELF) technique to produce spectrophotometry that is more accurate and more sensitive than other methods. We show that DELF analyses are superior to classical techniques in high surface brightness regions of galaxies, and we validate the method both through simulations and via the analysis of data from two early-type galaxies (NGC 1380 and NGC 474) and one late-type spiral (NGC 628). We demonstrate that with adaptive optics support or under excellent seeing conditions, the technique is capable of producing precision (≲0.05 mag) [O iii] photometry out to distances of 40 Mpc while providing discrimination between planetary nebulae and other emission-line objects such as H ii regions, supernova remnants, and background galaxies. These capabilities enable us to use MUSE to measure precise PNLF distances beyond the reach of Cepheids and the tip of the red giant branch method and become an additional tool for constraining the local value of the Hubble constant.