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Dynamically close galaxy pairs from the unWISE survey
No full textContext. Galaxy mergers are expected to have a profound influence on the star formation histories of galaxies. It is generally expected that mergers are the main drivers of galaxy mass growth through the accretion of mass and the triggering of new star formation episodes, while the shocks and torques induced by the merger may drive gas and dust to central supermassive black holes and fuel active galactic nucleus (AGN) activity and produce both positive and negative feedback.
Aims. We test whether a merger-AGN-star formation connection exists by selecting samples of galaxy pairs of stellar masses log(M/M⊙)∼10.2 and ∼11.4 within redshift z < 0.25 at various projected separation and velocity differences in an increasing order, and would therefore have a decreasing probability of being truly bound and interacting.
Methods. We identified galaxies in close pairs and then measured their star formation rates (SFRs; via their NUV − r colours) and the degree of AGN activity (from X-rays, radio emission at 20 cm, WISE infrared colours, and emission line ratios) as a function of their projected separation and velocity difference.
Results. We find only weak evidence that galaxies in pairs have higher SFRs as galaxies become closer in projected and velocity separation. This trend occurs for pairs at closest separation of rp < 20 kpc and ΔV < 500 km/s. Similarly, we observe no strong evidence that AGNs are more common for galaxies in closer pairs, irrespective of the method used to detect AGNs.
Conclusions. For this sample, we did not find any clear evidence that mergers and interactions may play a significant role in triggering star formation and AGN activity, opposite to expectations from theoretical models invoking feedback episodes. Secular processes may be more important, although this may depend on the selection of galaxies and indicators for star formation and AGN activity
The ACT Data Release 6 Sunyaev-Zel’dovich Selected Cluster Catalog
No full textThe Atacama Cosmology Telescope (ACT) conducted an arcmin resolution survey of the southern sky at millimeter wavelengths from 2008- 2022. I present an update on the ACT search for galaxy clusters using the redshift independent Sunyaev-Zel’dovich (SZ) effect, using data from the full ACT survey, covering 15,000 square degrees. The final ACT Data Release 6 (DR6) cluster catalog is expected to contain ~ 10000 galaxy clusters with redshift and mass estimates. I describe the construction of the catalog (in particular the differences with respect to ACT DR5), products and tools associated with the data release, and discuss some science applications of the catalog
Kinematics of young stellar objects in NGC 2024 based on infrared proper motions
No full textThe most recently formed young stellar objects (YSOs) in active star-forming regions are excellent tracers of their parent cloud motion. Their positions and dynamics provide insights into cluster formation and constrain kinematic decoupling timescales between stars and gas. However, because of their strong extinction and young age, embedded YSOs are mainly visible at infrared wavelengths, and are thus absent from astrometric surveys such as Gaia. We measured the proper motions of 6769 sources toward the NGC 2024 cluster in the Flame Nebula (d ~ 420 pc) using multi-epoch near-infrared observations from three ESO public surveys: VISIONS, VHS, and the VISTA/VIRCAM science verification program. Cross-validation of our results with Gaia using optically visible stars shows excellent agreement, with uncertainties on the same order of magnitude. For 362 YSO candidates identified from the literature, we derived proper motions on the order of 13-fold increase in available proper motion measurements. We analyzed the positional and kinematic differences between YSO classes and confirmed a previously reported inside-out age segregation from younger to older stars, likely driven by an outward movement of older stars. No evidence of prolonged hierarchical assembly was found. Instead, the results support a rapid (<1 Myr) cluster collapse into a centrally concentrated system. This scenario also accounts for the observed slightly higher 1D velocity dispersion of Class I sources relative to Class flat objects. YSO radial velocities generally align with the gas velocities measured from the molecular transitions of 12CO(3 − 2), HNC(1 − 0), HCN(1 − 0), and show a weaker correlation with N2H+(1 − 0). Some Class II and III objects already appear to be decoupling
A new method of deriving Doppler velocities for Solar Orbiter SPICE
No full textThis paper presents a follow-up to previous work on correcting point-spread-function (PSF)-induced Doppler artifacts in observations by the SPICE spectrograph on Solar Orbiter. In a previous paper, we demonstrated the correction of these artifacts in the y − λ plane with PSF regularization, treating the forward problem with a method based on large sparse matrix inversion. It has since been found that similar apparent artifacts are also present in the x − λ direction, i.e., across adjacent slit positions. Correcting this is difficult (although not impossible) with the previous matrix inversion method due to the time variation between slit positions. We have therefore devised a new method that addresses both x − λ and y − λ artifacts simultaneously by applying wavelength-dependent shifts at each x − y plane of the spectral cube. This paper demonstrates the SPICE data issue, describes the new method, and shows a comparison with the previous one. We explore the time variation of the correction parameters for the SPICE data and show a clear orbit dependence. The results of the method are significantly higher-quality Doppler signals, which we estimate at less than ∼5 km/s uncertainty for brighter lines in the absence of other systematics. Furthermore, we show the new SPICE polar observation results as a demonstration. The correction codes are written in Python, publicly available on GitHub, and can be directly applied to SPICE level 2 datasets
The magnetic origin of the outer boundaries of sunspots
No full textContext. Sunspot boundaries are commonly outlined by contours of the continuum intensity. However, their magnetic nature has not yet been fully characterised.
Aims. We investigate the properties of the outer boundary of a long-lived sunspot, aiming to identify the magnetic property that defines it.
Methods. We analysed the magnetic properties of AR NOAA 11591 spot during its two passages across the solar disc. To this end, we used SDO/HMI continuum intensity and magnetic field parameters and determined the contours of these parameters to outline the outer boundary.
Results. During the first disc passage, in which the sunspot is in its stable phase, we find that the intensity contours at 0.9 of the mean intensity of the vicinity of the spot and isocontours of the magnetic field strength of 625 G provide an almost perfect match between the two contours. With these thresholds, the time-averaged area of mismatch is minimised, yielding an average distance between the contours of 0.58 pixel, corresponding to less than 0.26 arcsec. During the second disc passage, the spot shows clear signs of decay, and we find that the 0.9 intensity and 625 G magnetic isocontours detach from each other, coupled to the disappearance of penumbra. In this super-equipartition area, granulation still operates.
Conclusions. Based on a comparison with simulation data from our previous work, and in agreement with findings of other authors, we conclude that the outer boundary of stable sunspots is defined by an invariant magnetic field: the equipartition field. From the discrepancy between intensity and magnetic contours during the decaying phase of the sunspot, we surmise that alongside the well-established (magneto-)convective regimes of the photosphere – granular, penumbral, and umbral – a super-equipartition granular regime can be identified. In this regime, bright, but smaller granules occur where the magnetic field exceeds equipartition but remains subcritical for convection suppression
Elemental abundance pattern and temperature inversion on the dayside of HAT-P-70b observed with CARMENES and PEPSI
No full textGround-based high-resolution spectroscopic observations have identified various chemical species in the atmosphere of numerous ultra-hot Jupiters (UHJs), including neutral and ionized metals. These detections have offered valuable insights into planet formation mechanisms via abundance measurements of refractory elements. We observed the dayside thermal emission spectrum of UHJ HAT-P-70b using the high-resolution spectrographs CARMENES and PEPSI. Through our cross-correlation analysis, we detected emission signals for Al
A Lexicon to Describe Specific Sounds of the Electric Car Cabin : Verbal Approach toward Comfort Improvement
No full textElectric vehicles are now part of the everyday automotive landscape. The resulting sonic experience is a major challenge for driver comfort. Despite this challenge being known, no solution reaching general consensus has yet been proposed. This might be due to the lack of a common culture of the sound or the expected sonic target in electric vehicles, in opposition to what existed for thermal engine. This work proposes a decisive tool to enhance communication on sound description in the electric car cabin. Inspired by soundscape studies, the methodology consists in using a semi-structured questionnaire oriented toward sound description and judgment with 12 acousticians working on electric vehicles. A verbal analysis identifies 11 specific sound names describing this sonic environment. Definitions that include three levels of description: causal, reduced and hedonic as well as audio illustrations, are proposed for each sound name. The lexicon is validated by the same group of acousticians and available online
Heat Pump Noise: Determination and Modelling of Preference-Equivalent Levels
No full textAir-to-water heat pumps are increasingly replacing traditional heating systems because of their environmental and energy benefits. However, noise emitted by their fans and compressors can cause complaints, even when regulatory limits are met. In this study, two listening experiments were conducted to examine heat pump noise by quantifying it as level penalties for equivalent loudness and preference. The study investigates how the preference-equivalent level differs from the loudness-equivalent level compared to a reference stimulus, and which psychoacoustic parameters best model the resulting level adjustments. Recordings from two heat pumps were auralised into a suburban residential setting and adjusted to an initial level of 60 dB(A). A two-alternative forced-choice (2-AFC) method with a 1-up-1-down rule is used to determine the point of subjective equality (PSE) for loudness and preference. Statistical analyses show significant differences between loudness-equivalent and preference-equivalent levels for eight of twelve stimuli. The median values further indicate that achieving equal preference relative to the reference generally requires lower sound pressure levels than achieving equal loudness, with the magnitude of this level offset varying across stimuli. Combining the results with psychoacoustic parameter analyses, two models based on linear regression were developed. This linear approach was chosen to ensure straightforward interpretability and robustness for the given stimulus set. Perceived loudness can be modelled by the psychoacoustic parameter loudness, while preference is best modelled by a linear combination of sharpness and roughness. These findings emphasise the need for perceptual metrics beyond A-weighted sound pressure levels when evaluating and optimising heat pump noise
Achondrites in meteor data: Spectra, dynamics, and physical properties of candidate aubrite and eucrite impactors
No full textMeteor spectroscopy presents new opportunities for investigating the diversity of small Solar System bodies and capturing the real distribution of present material types. In this work, we analyzed a sample of 180 higher-resolution meteor spectra from the All-sky Meteor Orbit System (AMOS) network to search for meteoroids with atypical compositions. In addition to several iron bodies, we have identified the first two achondritic meteoroids in our database, both likely meteorite-dropping impactors. We analyzed the two cases in detail using their spectral, dynamical, and physical properties, and compared them with a reference ordinary chondrite meteoroid observed under similar conditions. The spectral analysis revealed atypical features in the two achondrites - strong Mg and Si and low Fe in one case, and strong Ca, Al, and Ti and low Mg in the other. The measured relative elemental abundances imply an aubrite- and a eucrite-like composition. The aubrite-like meteoroid showed an unexpected enhancement in Ca, Mn, and Ti with short-lived intensity spikes not seen in the eucrite-like case, which we interpret as the rapid release of localized inclusions rather than a bulk enrichment. This indicates that transient spectral features can reveal internal heterogeneity in achondritic meteoroids beyond their average composition. The classification of both meteoroids was found to be consistent with the determined dynamical and physical properties. The eucrite meteoroid originated from an orbit affected by the ν6 resonance in the inner main belt, a common delivery mechanism of HowarditeEucrite-Diogenite meteorites, and exhibited ablation behavior corresponding to a compact material with low erosion and an estimated bulk density of ≈3.16 ± 0.10 g cm−3. The aubrite meteoroid originated from a short-period, low-eccentricity orbit similar to some known E-type near-Earth asteroids. Both events also exhibited atypical light curve behavior, but our results indicate that the robust identification of achondritic meteoroids in meteor surveys generally requires emission spectra. This work presents one of the first detailed studies of achondritic meteoroids from meteor observations and aims to provide reference properties of atypical meteors for more efficient identifications of achondrites in future surveys
Model selection with the Pantheon+ Type Ia supernova sample
No full textContext. Recent discoveries, for example by JWST and DESI, have elevated the level of tension with inflationary Λ cold dark matter (ΛCDM). For example, the empirical evidence now suggests that the standard model violates at least one of the energy conditions from general relativity, which were designed to ensure that systems have positive energy, attractive gravity, and non-superluminal energy flows.
Aims. We used a recently compiled Type Ia supernova sample to examine whether ΛCDM violates the energy conditions in the local Universe, and carried out model selection with its principal competitor, the Rh = ct universe.
Methods. We derived model-independent constraints on the distance modulus based on the energy conditions and compared them with the Hubble diagram predicted by both ΛCDM and Rh = ct, using the Pantheon+ Type Ia supernova catalogue.
Results. We find that ΛCDM violates the strong energy condition over the redshift range z ⊂ (0, 2), whereas Rh = ct satisfies all four energy constraints. At the same time, Rh = ct is favoured by these data over ΛCDM with a likelihood of ∼89.8% versus ∼10.2%.
Conclusions. The Rh = ct model without inflation is strongly favoured by the Type Ia supernova data over the current standard model, while simultaneously adhering to the general relativistic energy conditions at both high and low redshifts